DC power-supply unit

Claim 2

A dc power-supply unit comprising: rectifying means for converting ac power output from an ac power supply into dc power so as to feed to a load; an inductive element whose one end is connected to one terminal on a side of said rectifying means; switching means connected between the other end of said inductive element and the other terminal on side of said rectifying means to perform a switching operation; and smoothing means connected in parallel with said switching means, and said dc power-supply unit further comprising: switch controlling means in which first and second delay times are preset so as to, when ac voltage and/or ac current of said ac power supply passes through a zero point, close said switching means after said preset first delay time from a passing through time, and open said switching means after said second delay time form said passing through time.

Claim 3

A dc power-supply unit comprising: rectifying means for converting ac power output from an ac power supply into dc power so as to feed to a load; an inductive element whose one end is connected to one terminal on a side of said rectifying means; switching means connected between the other end of said inductive element and the other terminal on said side of said rectifying means to perform a switching operation; and smoothing means connected in parallel with said switching means, and said dc power-supply unit further comprising: switch controlling means in which a first delay time is preset so as to, when ac voltage and/or ac current of said ac power supply passes through a zero point, close said switching means after said first delay time from a passing through time, and open said switching means after a predetermined time period from a closing time.

Claim 4

A dc power-supply unit comprising: rectifying means for converting ac power output from an ac power supply into dc power so as to feed to a load; an inductive element whose one end is connected to one terminal on a side of said rectifying means; switching means connected between the other end of said inductive element and the other terminal on said side of said rectifying means to perform a switching operation; and smoothing means connected in parallel with said switching means, and said dc power-supply unit further comprising: switch controlling means in which a first delay time is preset so as to, when ac voltage and/or ac current of said ac power supply passes through a zero point, close said switching means after said first delay time from a passing through time, and open said switching means after a predetermined time period from a closing time.

Claim 5

A dc power-supply unit comprising: rectifying means for converting ac power output from an ac power supply into dc power so as to feed to a load; an inductive element whose one end is connected to one terminal on a side of said rectifying means; switching means connected between the other end of said inductive element and the other terminal on said side of said rectifying means to perform a switching operation; and smoothing means connected in parallel with said switching means, and said dc power-supply unit further comprising: short-circuit current detecting means for detecting short-circuit current flowing in said inductive element; and switch controlling means in which a first delay time is preset so as to, when ac voltage and/or ac current of said ac power supply passes through a zero point, close said switching means after said delay time from a passing through time, and open said switching means when a value of said short-circuit current becomes a predetermined value after a closing operation.

Claim 6

A dc power-supply unit comprising: rectifying means for converting ac power output from an ac power supply into dc power so as to feed to a load; an inductive element whose one end is connected to one terminal on a side of said rectifying means; switching means connected between the other end of said inductive element and the other terminal on said side of said rectifying means to perform a switching operation; and smoothing means connected in parallel with said switching means, and said dc power-supply unit further comprising: short-circuit current detecting means for detecting short-circuit current flowing in said inductive element; and switch controlling means in which a first delay time is preset so as to, when ac voltage and/or ac current of said ac power supply passes through a zero point, close said switching means after said delay time from a passing through time, and open said switching means when a value of said short-circuit current becomes a predetermined value after a closing operation.

Claim 7

A dc power-supply unit comprising: rectifying means for converting ac power output from an ac power supply into dc power so as to feed to a load; an inductive element whose one end is connected to one terminal on a side of said rectifying means; switching means connected between the other end of said inductive element and the other terminal on said side of said rectifying means to perform a switching operation; and smoothing means connected in parallel with said switching means, and said dc power-supply unit further comprising: load condition detecting means for detecting magnitude of said load; and switch controlling means in which a first delay time under a light load is preset to be shorter than a second delay time under a heavy load, and a third delay time is preset to, when ac voltage and/or ac current of said ac power supply passes through a zero point, select said first delay time or said second delay time depending upon the results of detection of said load condition detecting means so as to close said switching means after a selected delay time from a passing through time, and so as to open said switching means after said third delay time from said passing through time.

Claim 8

A dc power-supply unit comprising: rectifying means for converting ac power output from an ac power supply into dc power so as to feed to a load; an inductive element whose one end is connected to one terminal on a side of said rectifying means; switching means connected between the other end of said inductive element and the other terminal on said side of said rectifying means to perform a switching operation; and smoothing means connected in parallel with said switching means, and said dc power-supply unit further comprising: load condition detecting means for detecting magnitude of said load; and switch controlling means in which a first delay time under a light load is preset to be shorter than a second delay time under a heavy load, and a third delay time is preset to, when ac voltage and/or ac current of said ac power supply passes through a zero point, select said first delay time or said second delay time depending upon the results of detection of said load condition detecting means so as to close said switching means after a selected delay time from a passing through time, and so as to open said switching means after said third delay time from said passing through time.

Claim 9

A dc power-supply unit comprising: rectifying means for converting ac power output from an ac power supply into dc power so as to feed to a load; an inductive element whose one end is connected to one terminal on a side of said rectifying means; switching means connected between the other end of said inductive element and the other terminal on the side of said rectifying means to perform a switching operation; and smoothing means connected in parallel with said switching means, and said dc power-supply unit further comprising: load condition detecting means for detecting magnitude of said load; and switch controlling means in which a first delay under a light load is preset, and a second delay time under a heavy load is preset to be shorter than said first delay time under said light load to, when ac voltage and/or ac current of said ac power supply passes through a zero point, select said first delay time or said second delay time depending upon results of detection of said load condition detecting means so as to close said switching means after a selected delay time from a passing through time, and so as to open said switching means after a predetermined time period from a closing time.

Claim 10

A dc power-supply unit comprising: rectifying means for converting ac power output from an ac power supply into dc power so as to feed to a load; an inductive element whose one end is connected to one terminal on a side of said rectifying means; switching means connected between the other end of said inductive element and the other terminal on the side of said rectifying means to perform a switching operation; and smoothing means connected in parallel with said switching means, and said dc power-supply unit further comprising: load condition detecting means for detecting magnitude of said load; and switch controlling means in which a first delay under a light load is preset, and a second delay time under a heavy load is preset to be shorter than said first delay time under said light load to, when ac voltage and/or ac current of said ac power supply passes through a zero point, select said first delay time or said second delay time depending upon results of detection of said load condition detecting means so as to close said switching means after a selected delay time from a passing through time, and so as to open said switching means after a predetermined time period from a closing time.

Claim 11

A dc power-supply unit comprising: rectifying means for converting ac power output from an ac power supply into dc power so as to feed to a load; an inductive element whose one end is connected to one terminal on a side of said rectifying means; switching means connected between the other end of said inductive element and the other terminal on the side of said rectifying means to perform a switching operation; and smoothing means connected in parallel with said switching means, and said dc power-supply unit further comprising: short-circuit current detecting means for detecting short-circuit current flowing in said inductive element; load condition detecting means for detecting magnitude of said load; and switch controlling means in which a first delay time under a light load is preset, and a second delay time under a heavy load is preset to be shorter than said first delay time under said light load to, when ac voltage and/or ac current of said ac power supply passes through a zero point, select said first delay time or said second delay time depending upon results of detection of said load condition detecting means so as to close said switching means after a selected delay time from a passing through time, and so as to open said switching means when a value of said short-circuit current becomes a predetermined value after a closing operation.

Claim 12

A dc power-supply unit comprising: rectifying means for converting ac power output from an ac power supply into dc power so as to feed to a load; an inductive element whose one end is connected to one terminal on a side of said rectifying means; switching means connected between the other end of said inductive element and the other terminal on the side of said rectifying means to perform a switching operation; and smoothing means connected in parallel with said switching means, and said dc power-supply unit further comprising: short-circuit current detecting means for detecting short-circuit current flowing in said inductive element; load condition detecting means for detecting magnitude of said load; and switch controlling means in which a first delay time under a light load is preset, and a second delay time under a heavy load is preset to be shorter than said first delay time under said light load to, when ac voltage and/or ac current of said ac power supply passes through a zero point, select said first delay time or said second delay time depending upon results of detection of said load condition detecting means so as to close said switching means after a selected delay time from a passing through time, and so as to open said switching means when a value of said short-circuit current becomes a predetermined value after a closing operation.

Claim 13

A dc power-supply unit comprising: rectifying means for converting ac power output from an ac power supply into dc power so as to feed to a load; an inductive element whose one end is connected to one terminal on a side of said rectifying means; switching means connected between the other end of said inductive element and the other terminal on said side of said rectifying means to perform a switching operation; and smoothing means connected in parallel with said switching means, and said dc power-supply unit further comprising: load condition detecting means for detecting magnitude of said load; and switch controlling means in which a first delay time and a second delay time under a light load are preset, and a third delay time under a heavy load is preset to be longer than said second delay time under said light load to, when ac voltage and/or ac current of said ac power supply passes through a zero point, close said switching means after said first delay time from a passing through time, and select said second delay time or said third delay time depending upon the results of the detection of said load condition detecting means so as to open said switching means after a selected delay time from said passing through time.

Claim 14

A dc power-supply unit comprising: rectifying means for converting ac power output from an ac power supply into dc power so as to feed to a load; an inductive element whose one end is connected to one terminal on a side of said rectifying means; switching means connected between the other end of said inductive element and the other terminal on said side of said rectifying means to perform a switching operation; and smoothing means connected in parallel with said switching means, and said dc power-supply unit further comprising: load condition detecting means for detecting magnitude of said load; and switch controlling means in which a first delay time and a second delay time under a light load are preset, and a third delay time under a heavy load is preset to be longer than said second delay time under said light load to, when ac voltage and/or ac current of said ac power supply passes through a zero point, close said switching means after said first delay time from a passing through time, and select said second delay time or said third delay time depending upon the results of the detection of said load condition detecting means so as to open said switching means after a selected delay time from said passing through time.

Claim 15

A dc power-supply unit comprising: rectifying means for converting ac power output from an ac power supply into dc power so as to feed to a load; an inductive element whose one end is connected to one terminal on a side of said rectifying means; switching means connected between the other end of said inductive element and the other terminal on said side of said rectifying means to perform a switching operation; and smoothing means connected in parallel with said switching means, and said dc power-supply unit further comprising: load condition detecting means for detecting magnitude of said load; and switch controlling means in which a first delay time and a second delay time under a light load are preset, and a third delay time under a heavy load is preset to be longer than said second delay time under said light load to, when ac voltage and/or ac current of said ac power supply passes through a zero point, close said switching means after said first delay time from a passing through time, and select said second delay time or said third delay time depending upon results of detection of said load condition detecting means so as to open said switching means after a selected delay time from a closing operation.

Claim 16

A dc power-supply unit comprising: rectifying means for converting ac power output from an ac power supply into dc power so as to feed to a load; an inductive element whose one end is connected to one terminal on a side of said rectifying means; switching means connected between the other end of said inductive element and the other terminal on said side of said rectifying means to perform a switching operation; and smoothing means connected in parallel with said switching means, and said dc power-supply unit further comprising: load condition detecting means for detecting magnitude of said load; and switch controlling means in which a first delay time and a second delay time under a light load are preset, and a third delay time under a heavy load is preset to be longer than said second delay time under said light load to, when ac voltage and/or ac current of said ac power supply passes through a zero point, close said switching means after said first delay time from a passing through time, and select said second delay time or said third delay time depending upon results of detection of said load condition detecting means so as to open said switching means after a selected delay time from a closing operation.

Claim 17

A dc power-supply unit comprising: rectifying means for converting ac power output from an ac power supply into dc power so as to feed to a load; an inductive element whose one end is connected to one terminal on a side of said rectifying means; switching means connected between the other end of said inductive element and the other terminal on said side of said rectifying means to perform a switching operation; and smoothing means connected in parallel with said switching means, and said dc power-supply unit further comprising: short-circuit current detecting means for detecting short-circuit current flowing in said inductive element; load condition detecting means for detecting magnitude of said load; and switch controlling means in which a first delay time is preset to, when ac voltage and/or ac current of said ac power supply passes through a zero point, close said switching means after said delay time from a passing through time, and detect depending upon said load condition detecting means whether or not a value of said short-circuit current becomes a value preset according to said magnitude of said load after a closing operation so as to open said switch means when a decision is made that said short-circuit current becomes said predetermined value.

Claim 18

A dc power-supply unit comprising: rectifying means for converting ac power output from an ac power supply into dc power so as to feed to a load; an inductive element whose one end is connected to one terminal on a side of said rectifying means; switching means connected between the other end of said inductive element and the other terminal on said side of said rectifying means to perform a switching operation; and smoothing means connected in parallel with said switching means, and said dc power-supply unit further comprising: short-circuit current detecting means for detecting short-circuit current flowing in said inductive element; load condition detecting means for detecting magnitude of said load; and switch controlling means in which a first delay time is preset to, when ac voltage and/or ac current of said ac power supply passes through a zero point, close said switching means after said delay time from a passing through time, and detect depending upon said load condition detecting means whether or not a value of said short-circuit current becomes a value preset according to said magnitude of said load after a closing operation so as to open said switch means when a decision is made that said short-circuit current becomes said predetermined value.

Claim 19

A dc power-supply unit comprising: rectifying means for converting ac power output from an ac power supply into dc power so as to feed to a load; an inductive element whose one end is connected to one terminal on a side of said rectifying means; switching means connected between the other end of said inductive element, and the other terminal on said side of said rectifying means to perform a switching operation; and smoothing means connected in parallel with said switching means, and said dc power-supply unit further comprising: load condition detecting means for detecting magnitude of said load; and switch controlling means in which a first delay time under a light load and a second delay time under a heavy load are preset such that said second delay time under said heavy load is shorter than said first delay time under said light load, and a third delay time under a light load and a fourth delay time under a heavy load are preset such that said fourth delay time under said heavy load is longer than said third delay time under said light load to, when ac voltage and/or ac current of said ac power supply passes through a zero point, select said first delay time or said second delay time depending upon results of detection of said load condition detecting means so as to close said switching means after a selected delay time from a passing through time, and to select said third delay time or said fourth delay time depending upon results of said detection of said load condition detecting means so as to open said switching means after a selected delay time from said passing through time.

Claim 20

A dc power-supply unit comprising: rectifying means for converting ac power output from an ac power supply into dc power so as to feed to a load; an inductive element whose one end is connected to one terminal on a side of said rectifying means; switching means connected between the other end of said inductive element, and the other terminal on said side of said rectifying means to perform a switching operation; and smoothing means connected in parallel with said switching means, and said dc power-supply unit further comprising: load condition detecting means for detecting magnitude of said load; and switch controlling means in which a first delay time under a light load and a second delay time under a heavy load are preset such that said second delay time under said heavy load is shorter than said first delay time under said light load, and a third delay time under a light load and a fourth delay time under a heavy load are preset such that said fourth delay time under said heavy load is longer than said third delay time under said light load to, when ac voltage and/or ac current of said ac power supply passes through a zero point, select said first delay time or said second delay time depending upon results of detection of said load condition detecting means so as to close said switching means after a selected delay time from a passing through time, and to select said third delay time or said fourth delay time depending upon results of said detection of said load condition detecting means so as to open said switching means after a selected delay time from said passing through time.

Claim 21

A dc power-supply unit comprising: rectifying means for converting ac power output from an ac power supply into dc power so as to feed to a load; an inductive element whose one end is connected to one terminal on a side of said rectifying means; switching means connected between the other end of said inductive element and the other terminal on said side of said rectifying means to perform a switching operation; and smoothing means connected in parallel with said switching means, and said dc power-supply unit further comprising: load condition detecting means for detecting magnitude of said load; and switch controlling means in which a first delay time under a light load and a second delay time under a heavy load are preset such that said second delay time under said heavy load is shorter than said first delay time under said light load, and a third delay time under a light load and a fourth delay time under a heavy load are preset such that said fourth delay time under said heavy load is longer than said third delay time under said light load to, when ac voltage and/or ac current of said ac power supply passes through a zero point, select said first delay time or said second delay time depending upon results of detection of said load condition detecting means so as to close said switching means after a selected delay time from a passing through time, and to select said third delay time or said fourth delay time depending upon results of said detection of said load condition detecting means so as to open said switching means after a selected delay time from a closing time.

Claim 22

A dc power-supply unit comprising: rectifying means for converting ac power output from an ac power supply into dc power so as to feed to a load; an inductive element whose one end is connected to one terminal on a side of said rectifying means; switching means connected between the other end of said inductive element and the other terminal on said side of said rectifying means to perform a switching operation; and smoothing means connected in parallel with said switching means, and said dc power-supply unit further comprising: load condition detecting means for detecting magnitude of said load; and switch controlling means in which a first delay time under a light load and a second delay time under a heavy load are preset such that said second delay time under said heavy load is shorter than said first delay time under said light load, and a third delay time under a light load and a fourth delay time under a heavy load are preset such that said fourth delay time under said heavy load is longer than said third delay time under said light load to, when ac voltage and/or ac current of said ac power supply passes through a zero point, select said first delay time or said second delay time depending upon results of detection of said load condition detecting means so as to close said switching means after a selected delay time from a passing through time, and to select said third delay time or said fourth delay time depending upon results of said detection of said load condition detecting means so as to open said switching means after a selected delay time from a closing time.

Claim 23

A dc power-supply unit comprising: rectifying means for converting ac power output from an ac power supply into dc power so as to feed to a load; an inductive element whose one end is connected to one terminal on a side of said rectifying means; switching means connected between the other end of said inductive element and the other terminal on said side of said rectifying means to perform a switching operation; and smoothing means connected in parallel with said switching means, and said dc power-supply unit further comprising: short-circuit current detecting means for detecting short-circuit current flowing in said inductive element; load condition detecting means for detecting magnitude of said load; and switch controlling means in which a first delay time under a light load and a second delay time under a heavy load are preset such that said second delay time under said heavy load is shorter than said first delay time under said light load to, when ac voltage and/or ac current of said ac power supply passes through a zero point, select said first delay time or said second delay time depending upon results of detection of said load condition detecting means so as to close said switching means after a selected delay time from a passing through time, and to detect depending upon said load condition detecting means whether or not a value of said short-circuit current becomes a predetermined value preset according to said magnitude of said load after a closing operation so as to open said switching means when a decision is made that said short-circuit current becomes said predetermined value.

Claim 24

A dc power-supply unit comprising: rectifying means for converting ac power output from an ac power supply into dc power so as to feed to a load; an inductive element whose one end is connected to one terminal on a side of said rectifying means; switching means connected between the other end of said inductive element and the other terminal on said side of said rectifying means to perform a switching operation; and smoothing means connected in parallel with said switching means, and said dc power-supply unit further comprising: short-circuit current detecting means for detecting short-circuit current flowing in said inductive element; load condition detecting means for detecting magnitude of said load; and switch controlling means in which a first delay time under a light load and a second delay time under a heavy load are preset such that said second delay time under said heavy load is shorter than said first delay time under said light load to, when ac voltage and/or ac current of said ac power supply passes through a zero point, select said first delay time or said second delay time depending upon results of detection of said load condition detecting means so as to close said switching means after a selected delay time from a passing through time, and to detect depending upon said load condition detecting means whether or not a value of said short-circuit current becomes a predetermined value preset according to said magnitude of said load after a closing operation so as to open said switching means when a decision is made that said short-circuit current becomes said predetermined value.

Claim 25

A dc power-supply unit according to any one of claims 1 to 12, further comprising correcting means for detecting a power factor of ac power output from said ac power supply, and comparing said power factor with a predetermined value so as to correct said first delay time which is set in said switch controlling means to close said switching means depending upon results of a comparison.

Claim 26

A dc power-supply unit according to claim 1, further comprising correcting means for detecting a power factor of ac power output from said ac power supply, and comparing said power factor with a predetermined value so as to correct said second delay time which is set in said switch controlling means to open said switching means depending upon results of a comparison.

Claim 27

A dc power-supply unit according to any one of claims 1 to 12, further comprising correcting means for detecting a relative harmonic content in ac power output from said ac power supply, and comparing said relative harmonic content with a predetermined value so as to correct said first delay time which is set in said switch controlling means to close said switching means depending upon results of a comparison.

Claim 28

A dc power-supply unit according to claim 1, further comprising correcting means for detecting a relative harmonic content in ac power output from said ac power supply, and comparing said relative harmonic content with a predetermined value so as to correct said second delay time which is set in said switch controlling means to open said switching means depending upon results of a comparison.

Claim 29

A dc power-supply unit according to any one of claims 1 to 12, further comprising correcting means for detecting distortion in a waveform of said ac power supply, and comparing said distortion in said waveform with a predetermined value so as to correct said first delay time which is set in said switch controlling means to close said switching means depending upon results of a comparison.

Claim 30

A dc power-supply unit according to claim 1, further comprising correcting means for detecting distortion in a waveform of said ac power supply, and comparing said distortion in said waveform with a predetermined value so as to correct said second delay time which is set in said switch controlling means to open said switching means depending upon results of a comparison.

Claim 31

A dc power-supply unit according to claim 1, further comprising correcting means for detecting a power factor and a relative harmonic content of ac power output from said ac power supply, and comparing said power factor with a predetermined value so as to correct a first delay time which is set in said switch controlling means to close said switching means depending upon results of a comparison, and comparing said relative harmonic content with a predetermined value so as to correct said second delay time which is set in said switch controlling means to open said switching means depending upon results of a comparison.

Claim 32

A dc power-supply unit according to claim 1, further comprising correcting means for detecting a power factor and a relative harmonic content of ac power output from said ac power supply, and comparing said relative harmonic content with a predetermined value so as to correct said first delay time which is set in said switch controlling means to close said switching means depending upon results of a comparison, and comparing said power factor with a predetermined value so as to correct a second delay time which is set in said switch controlling means to open said switching means depending upon results of a comparison.

Claim 33

A dc power-supply unit according to any one of claims 1 to 12, wherein said side to which said inductive element is connected between one terminal of said rectifying means and said ac power supply is the ac side.

Claim 34

A dc power-supply unit according to any one of claims 1 to 12, wherein said switch controlling means repeatedly opens and closes said switching means at predetermined intervals until said switching means is opened after said switching means is closed.

Claim 35

A dc power-supply unit according to any one of claims 1 to 12, wherein said side to which said inductive element is connected between one terminal of said rectifying means and said ac power supply is the dc side.

Claim 36

A dc power-supply unit comprising: rectifying means for converting ac power output from an ac power supply into dc power so as to feed to a load; an inductive element whose one end is connected to one terminal on a side of said rectifying means; switching means connected between the other end of said inductive element and the other terminal on said side of said rectifying means for short-circuiting at least one of a plurality of rectifying devices forming said rectifying means; and smoothing means connected in parallel with said switching means, and said dc power-supply unit further comprising: load condition detecting means for detecting magnitude of said load; and switch controlling means in which a first delay time under a light load and a second delay time under a heavy load are preset such that said second delay time under said heavy load is shorter than said first delay time under said light load, and a third delay time under a light load and a fourth delay time under a heavy load are preset such that said fourth delay time under said heavy load is longer than said third delay time under said light load to, when ac voltage and/or ac current of said ac power supply passes through a zero point, select said first delay time or said second delay time depending upon results of detection of said load condition detecting means so as to close said switching means after a selected delay time from a passing through time, and to select said third delay time or said fourth delay time depending upon results of said detection of said load condition detecting means so as to open said switching means after a selected delay time from a closing time.

Claim 37

A dc power-supply unit comprising: rectifying means for converting ac power output from an ac power supply into dc power so as to feed to a load; an inductive element whose one end is connected to one terminal on a side of said rectifying means; switching means connected between the other end of said inductive element and the other terminal on said side of said rectifying means for short-circuiting at least one of a plurality of rectifying devices forming said rectifying means; and smoothing means connected in parallel with said switching means, and said dc power-supply unit further comprising: load condition detecting means for detecting magnitude of said load; and switch controlling means in which a first delay time under a light load and a second delay time under a heavy load are preset such that said second delay time under said heavy load is shorter than said first delay time under said light load, and a third delay time under a light load and a fourth delay time under a heavy load are preset such that said fourth delay time under said heavy load is longer than said third delay time under said light load to, when ac voltage and/or ac current of said ac power supply passes through a zero point, select said first delay time or said second delay time depending upon results of detection of said load condition detecting means so as to close said switching means after a selected delay time from a passing through time, and to select said third delay time or said fourth delay time depending upon results of said detection of said load condition detecting means so as to open said switching means after a selected delay time from a closing time.

Claim 38

A dc power-supply unit comprising: rectifying means for converting ac power output from an ac power supply into dc power so as to feed to a load; an inductive element whose one end is connected to one terminal on a side of said rectifying means; switching means connected between the other end of said inductive element and the other terminal on said side of said rectifying means for short-circuiting at least one of a plurality of rectifying devices forming said rectifying means; and smoothing means connected in parallel with said switching means, and said dc power-supply unit further comprising: short-circuit current detecting means for detecting short-circuit current flowing in said inductive element; load condition detecting means for detecting magnitude of said load; and switch controlling means in which a first delay time under a light load and a second delay time under a heavy load are preset such that said second delay time under said heavy load is shorter than said first delay time under said light load to, when ac voltage and/or ac current of said ac power supply passes through a zero point, select said first delay time or said second delay time depending upon the results of detection of said load condition detecting means so as to close said switching means after a selected delay time from a passing through time, and to detect depending upon said load condition detecting means whether or not a value of said short-circuit current becomes a predetermined value preset according to said magnitude of said load after a closing operation so as to open said switching means when a decision is made that said short-circuit current becomes said predetermined value.

Claim 39

A dc power-supply unit comprising: rectifying means for converting ac power output from an ac power supply into dc power so as to feed to a load; an inductive element whose one end is connected to one terminal on a side of said rectifying means; switching means connected between the other end of said inductive element and the other terminal on said side of said rectifying means for short-circuiting at least one of a plurality of rectifying devices forming said rectifying means; and smoothing means connected in parallel with said switching means, and said dc power-supply unit further comprising: short-circuit current detecting means for detecting short-circuit current flowing in said inductive element; load condition detecting means for detecting magnitude of said load; and switch controlling means in which a first delay time under a light load and a second delay time under a heavy load are preset such that said second delay time under said heavy load is shorter than said first delay time under said light load to, when ac voltage and/or ac current of said ac power supply passes through a zero point, select said first delay time or said second delay time depending upon the results of detection of said load condition detecting means so as to close said switching means after a selected delay time from a passing through time, and to detect depending upon said load condition detecting means whether or not a value of said short-circuit current becomes a predetermined value preset according to said magnitude of said load after a closing operation so as to open said switching means when a decision is made that said short-circuit current becomes said predetermined value.

Claim 40

A dc power-supply unit comprising: rectifying means for converting ac power output from an ac power supply into dc power so as to feed to a load; an inductive element whose one end is connected to one terminal on a side of said rectifying means; switching means connected between the other end of said inductive element and the other terminal on said side of said rectifying means to perform a switching operation; and smoothing means connected in parallel with said switching means, and said dc power-supply unit further comprising: overvoltage detecting means for detecting overvoltage across said smoothing means; and switch controlling means in which a delay time is preset so as to, when ac voltage and/or ac current of said ac power supply passes through a zero point, close said switching means after said delay time from a passing through time, and open said switching means when said overvoltage is detected by said overvoltage detecting means.

Claim 41

A dc power-supply unit comprising: rectifying means for converting ac power output from an ac power supply into dc power so as to feed to a load; an inductive element whose one end is connected to one terminal on a side of said rectifying means; switching means connected between the other end of said inductive element and the other terminal on said side of said rectifying means to perform a switching operation; and smoothing means connected in parallel with said switching means, and said dc power-supply unit further comprising: overvoltage detecting means for detecting overvoltage across said smoothing means; and switch controlling means in which a delay time is preset so as to, when ac voltage and/or ac current of said ac power supply passes through a zero point, close said switching means after said delay time from a passing through time, and open said switching means when said overvoltage is detected by said overvoltage detecting means.

Claim 42

A dc power-supply unit comprising: rectifying means for converting ac power output from an ac power supply into dc power so as to feed to a load; an inductive element whose one end is connected to one terminal on a side of said rectifying means; switching means connected between the other end of said inductive element and the other terminal on said side of said rectifying means to perform a switching operation; and smoothing means connected in parallel with said switching means, and said dc power-supply unit further comprising: overvoltage detecting means for detecting overvoltage across said smoothing means; load condition detecting means for detecting magnitude of said load; and switch controlling means in which a first delay time under a light load is preset, and a second delay time under a heavy load is preset to be shorter than said first delay time under said light load to, when ac voltage and/or ac current of said ac power supply passes through a zero point, select said first delay time or said second delay time depending upon results of detection of said load condition detecting means so as to close said switching means after a selected delay time from a passing through time, and so as to open said switching means when said overvoltage is detected by said overvoltage detecting means.

Claim 43

A dc power-supply unit comprising: rectifying means for converting ac power output from an ac power supply into dc power so as to feed to a load; an inductive element whose one end is connected to one terminal on a side of said rectifying means; switching means connected between the other end of said inductive element and the other terminal on said side of said rectifying means to perform a switching operation; and smoothing means connected in parallel with said switching means, and said dc power-supply unit further comprising: overvoltage detecting means for detecting overvoltage across said smoothing means; load condition detecting means for detecting magnitude of said load; and switch controlling means in which a first delay time under a light load is preset, and a second delay time under a heavy load is preset to be shorter than said first delay time under said light load to, when ac voltage and/or ac current of said ac power supply passes through a zero point, select said first delay time or said second delay time depending upon results of detection of said load condition detecting means so as to close said switching means after a selected delay time from a passing through time, and so as to open said switching means when said overvoltage is detected by said overvoltage detecting means.

Claim 44

A dc power-supply unit comprising: rectifying means for converting ac power output from an ac power supply into dc power so as to feed to a load; an inductive element whose one end is connected to one terminal on a side of said rectifying means; switching means connected between the other end of said inductive element and the other terminal on said side of said rectifying means to perform a switching operation; and smoothing means connected in parallel with said switching means, and said dc power-supply unit further comprising: overvoltage detecting means for detecting overvoltage across said smoothing means; load condition detecting means for detecting magnitude of said load; and switch controlling means in which a delay time is preset to, when ac voltage and/or ac current of said ac power supply passes through a zero point, close said switching means after said delay time from a passing through time, and detect depending upon said load condition detecting means whether or not a value of said short-circuit current becomes a value preset according to said magnitude of said load after a closing operation so as to open said switch means when said overvoltage is detected by said overvoltage detecting means.

Claim 45

A dc power-supply unit comprising: rectifying means for converting ac power output from an ac power supply into dc power so as to feed to a load; an inductive element whose one end is connected to one terminal on a side of said rectifying means; switching means connected between the other end of said inductive element and the other terminal on said side of said rectifying means to perform a switching operation; and smoothing means connected in parallel with said switching means, and said dc power-supply unit further comprising: overvoltage detecting means for detecting overvoltage across said smoothing means; load condition detecting means for detecting magnitude of said load; and switch controlling means in which a delay time is preset to, when ac voltage and/or ac current of said ac power supply passes through a zero point, close said switching means after said delay time from a passing through time, and detect depending upon said load condition detecting means whether or not a value of said short-circuit current becomes a value preset according to said magnitude of said load after a closing operation so as to open said switch means when said overvoltage is detected by said overvoltage detecting means.

Claim 46

A dc power-supply unit comprising: rectifying means for converting ac power output from an ac power supply into dc power so as to feed to a load; an inductive element whose one end is connected to one terminal on a side of said rectifying means; switching means connected between the other end of said inductive element and the other terminal on said side of said rectifying means for short-circuiting at least one of a plurality of rectifying devices forming said rectifying means; smoothing means connected in parallel with said switching means, and said dc power-supply unit further comprising: switch controlling means in which first and second delay times are preset so as to, when ac voltage and/or ac current of said ac power supply passes through a zero point, close said switching means after said preset first delay time from a passing through time, and open said switching means after said second delay time from said passing through time.

Claim 47

A dc power-supply unit comprising: rectifying means for converting ac power output from an ac power supply into dc power so as to feed to a load; an inductive element whose one end is connected to one terminal on a side of said rectifying means; switching means connected between the other end of said inductive element and the other terminal on said side of said rectifying means for short-circuiting at least one of a plurality of rectifying devices forming said rectifying means; smoothing means connected in parallel with said switching means, and said dc power-supply unit further comprising: switch controlling means in which first and second delay times are preset so as to, when ac voltage and/or ac current of said ac power supply passes through a zero point, close said switching means after said preset first delay time from a passing through time, and open said switching means after said second delay time from said passing through time.

Claim 48

A dc power-supply unit comprising: rectifying means for converting ac power output from an ac power supply into dc power so as to feed to a load; an inductive element whose one end is connected to one terminal on a side of said rectifying means; switching means connected between the other end of said inductive element and the other terminal on said side of said rectifying means for short-circuiting at least one of a plurality of rectifying devices forming said rectifying means; smoothing means connected in parallel with said switching means, and said dc power-supply unit further comprising: switch controlling means in which a delay time is preset so as to, when ac voltage and/or ac current of said ac power supply passes through a zero point, close said switching means after said delay time from a passing through time, and open said switching means after a predetermined time period from a closing time.

Claim 49

A dc power-supply unit comprising: rectifying means for converting ac power output from an ac power supply into dc power so as to feed to a load; an inductive element whose one end is connected to one terminal on a side of said rectifying means; switching means connected between the other end of said inductive element and the other terminal on said side of said rectifying means for short-circuiting at least one of a plurality of rectifying devices forming said rectifying means; smoothing means connected in parallel with said switching means, and said dc power-supply unit further comprising: switch controlling means in which a delay time is preset so as to, when ac voltage and/or ac current of said ac power supply passes through a zero point, close said switching means after said delay time from a passing through time, and open said switching means after a predetermined time period from a closing time.

Claim 50

A dc power-supply unit comprising: rectifying means for convening ac power output from an ac power supply into dc power so as to feed to a load; an inductive element whose one end is connected to one terminal on a side of said rectifying means; switching means connected between the other end of said inductive element and the other terminal on said side of said rectifying means for short-circuiting at least one of a plurality of rectifying devices forming said rectifying means; smoothing means connected in parallel with said switching means, and said dc power-supply unit further comprising: short-circuit current detecting means for detecting short-circuit current flowing in said inductive element; and switch controlling means in which a delay time is preset so as to, when ac voltage and/or ac current of said ac power supply passes through a zero point, close said switching means after said delay time from a passing through time, and open said switching means when a value of said short-circuit current becomes a predetermined value after a closing operation.

Claim 51

A dc power-supply unit comprising: rectifying means for convening ac power output from an ac power supply into dc power so as to feed to a load; an inductive element whose one end is connected to one terminal on a side of said rectifying means; switching means connected between the other end of said inductive element and the other terminal on said side of said rectifying means for short-circuiting at least one of a plurality of rectifying devices forming said rectifying means; smoothing means connected in parallel with said switching means, and said dc power-supply unit further comprising: short-circuit current detecting means for detecting short-circuit current flowing in said inductive element; and switch controlling means in which a delay time is preset so as to, when ac voltage and/or ac current of said ac power supply passes through a zero point, close said switching means after said delay time from a passing through time, and open said switching means when a value of said short-circuit current becomes a predetermined value after a closing operation.

Claim 52

A dc power-supply unit comprising: rectifying means for converting ac power output from an ac power supply into dc power so as to feed to a load; an inductive element whose one end is connected to one terminal on a side of said rectifying means; switching means connected between the other end of said inductive element and the other terminal on said side of said rectifying means for short-circuiting at least one of a plurality of rectifying devices forming said rectifying means; and smoothing means connected in parallel with said switching means, and said dc power-supply unit further comprising: load condition detecting means for detecting magnitude of said load; and switch controlling means in which a first delay time under a light load is preset to be shorter than a second delay time under a heavy load, and a third delay time is preset to, when ac voltage and/or ac current of said ac power supply passes through a zero point, select said first delay time or said second delay time depending upon results of detection of said load condition detecting means so as to close said switching means after a selected delay time from a passing through time, and so as to open said switching means after said third delay time from said passing through time.

Claim 53

A dc power-supply unit comprising: rectifying means for converting ac power output from an ac power supply into dc power so as to feed to a load; an inductive element whose one end is connected to one terminal on a side of said rectifying means; switching means connected between the other end of said inductive element and the other terminal on said side of said rectifying means for short-circuiting at least one of a plurality of rectifying devices forming said rectifying means; and smoothing means connected in parallel with said switching means, and said dc power-supply unit further comprising: load condition detecting means for detecting magnitude of said load; and switch controlling means in which a first delay time under a light load is preset to be shorter than a second delay time under a heavy load, and a third delay time is preset to, when ac voltage and/or ac current of said ac power supply passes through a zero point, select said first delay time or said second delay time depending upon results of detection of said load condition detecting means so as to close said switching means after a selected delay time from a passing through time, and so as to open said switching means after said third delay time from said passing through time.

Claim 54

A dc power-supply unit comprising: rectifying means for converting ac power output from an ac power supply into dc power so as to feed to a load; an inductive element whose one end is connected to one terminal on a side of said rectifying means; switching means connected between the other end of said inductive element and the other terminal on said side of said rectifying means for short-circuiting at least one of a plurality of rectifying devices forming said rectifying means; and smoothing means connected in parallel with said switching means, and said dc power-supply unit further comprising: load condition detecting means for detecting magnitude of said load; and switch controlling means in which a first delay under a light load is preset, and a second delay time under a heavy load is preset to be shorter than said first delay time under said light load to, when ac voltage and/or ac current of said ac power supply passes through a zero point, select said first delay time or said second delay time depending upon results of detection of said load condition detecting means so as to close said switching means after a selected delay time from a passing through time, and so as to open said switching means after a predetermined time period from a closing time.

Claim 55

A dc power-supply unit comprising: rectifying means for converting ac power output from an ac power supply into dc power so as to feed to a load; an inductive element whose one end is connected to one terminal on a side of said rectifying means; switching means connected between the other end of said inductive element and the other terminal on said side of said rectifying means for short-circuiting at least one of a plurality of rectifying devices forming said rectifying means; and smoothing means connected in parallel with said switching means, and said dc power-supply unit further comprising: load condition detecting means for detecting magnitude of said load; and switch controlling means in which a first delay under a light load is preset, and a second delay time under a heavy load is preset to be shorter than said first delay time under said light load to, when ac voltage and/or ac current of said ac power supply passes through a zero point, select said first delay time or said second delay time depending upon results of detection of said load condition detecting means so as to close said switching means after a selected delay time from a passing through time, and so as to open said switching means after a predetermined time period from a closing time.

Claim 56

A dc power-supply unit comprising: rectifying means for converting ac power output from an ac power supply into dc power so as to feed to a load; an inductive element whose one end is connected to one terminal on a side of said rectifying means; switching means connected between the other end of said inductive element and the other terminal on said side of said rectifying means for short-circuiting at least one of a plurality of rectifying devices forming said rectifying means; and smoothing means connected in parallel with said switching means, and said dc power-supply unit further comprising: short-circuit current detecting means for detecting short-circuit current flowing in said inductive element; load condition detecting means for detecting magnitude of said load; and switch controlling means in which a first delay time under a light load is preset, and a second delay time under a heavy load is preset to be shorter than said first delay time under said light load to, when ac voltage and/or ac current of said ac power supply passes through a zero point, select said first delay time or said second delay time depending upon results of detection of said load condition detecting means so as to close said switching means after a selected delay time from a passing through time, and so as to open said switching means when a value of said short-circuit current becomes a predetermined value after a closing operation.

Claim 57

A dc power-supply unit comprising: rectifying means for converting ac power output from an ac power supply into dc power so as to feed to a load; an inductive element whose one end is connected to one terminal on a side of said rectifying means; switching means connected between the other end of said inductive element and the other terminal on said side of said rectifying means for short-circuiting at least one of a plurality of rectifying devices forming said rectifying means; and smoothing means connected in parallel with said switching means, and said dc power-supply unit further comprising: short-circuit current detecting means for detecting short-circuit current flowing in said inductive element; load condition detecting means for detecting magnitude of said load; and switch controlling means in which a first delay time under a light load is preset, and a second delay time under a heavy load is preset to be shorter than said first delay time under said light load to, when ac voltage and/or ac current of said ac power supply passes through a zero point, select said first delay time or said second delay time depending upon results of detection of said load condition detecting means so as to close said switching means after a selected delay time from a passing through time, and so as to open said switching means when a value of said short-circuit current becomes a predetermined value after a closing operation.

Claim 58

A dc power-supply unit comprising: rectifying means for converting ac power output from an ac power supply into dc power so as to feed to a load; an inductive element whose one end is connected to one terminal on a side of said rectifying means; switching means connected between the other end of said inductive element and the other terminal on said side of said rectifying means for short-circuiting at least one of a plurality of rectifying devices forming said rectifying means; and smoothing means connected in parallel with said switching means, and said dc power-supply unit further comprising: load condition detecting means for detecting magnitude of said load; and switch controlling means in which a first delay time and a second delay time under a light load are preset, and a third delay time under a heavy load is preset to be longer than said second delay time under said light load to, when ac voltage and/or ac current of said ac power supply passes through a zero point, close said switching means after said first delay time from a passing through time, and select said second delay time or said third delay time depending upon results of detection of said load condition detecting means so as to open said switching means after a selected delay time from said passing through time.

Claim 59

A dc power-supply unit comprising: rectifying means for converting ac power output from an ac power supply into dc power so as to feed to a load; an inductive element whose one end is connected to one terminal on a side of said rectifying means; switching means connected between the other end of said inductive element and the other terminal on said side of said rectifying means for short-circuiting at least one of a plurality of rectifying devices forming said rectifying means; and smoothing means connected in parallel with said switching means, and said dc power-supply unit further comprising: load condition detecting means for detecting magnitude of said load; and switch controlling means in which a first delay time and a second delay time under a light load are preset, and a third delay time under a heavy load is preset to be longer than said second delay time under said light load to, when ac voltage and/or ac current of said ac power supply passes through a zero point, close said switching means after said first delay time from a passing through time, and select said second delay time or said third delay time depending upon results of detection of said load condition detecting means so as to open said switching means after a selected delay time from said passing through time.

Claim 60

A dc power-supply unit comprising: rectifying means for converting ac power output from an ac power supply into dc power so as to feed to a load; an inductive element whose one end is connected to one terminal on a side of said rectifying means; switching means connected between the other end of said inductive element and the other terminal on said side of said rectifying means for short-circuiting at least one of a plurality of rectifying devices forming said rectifying means; and smoothing means connected in parallel with said switching means, and said dc power-supply unit further comprising: load condition detecting means for detecting magnitude of said load; and switch controlling means in which a first delay time and a second delay time under a light load are preset, and a third delay time under a heavy load is preset to be longer than said second delay time under said light load to, when ac voltage and/or ac current of said ac power supply passes through a zero point, close said switching means after said first delay time from a passing through time, and select said second delay time or said third delay time depending upon results of detection of said load condition detecting means so as to open said switching means after a selected delay time from a closing operation.

Claim 61

A dc power-supply unit comprising: rectifying means for converting ac power output from an ac power supply into dc power so as to feed to a load; an inductive element whose one end is connected to one terminal on a side of said rectifying means; switching means connected between the other end of said inductive element and the other terminal on said side of said rectifying means for short-circuiting at least one of a plurality of rectifying devices forming said rectifying means; and smoothing means connected in parallel with said switching means, and said dc power-supply unit further comprising: load condition detecting means for detecting magnitude of said load; and switch controlling means in which a first delay time and a second delay time under a light load are preset, and a third delay time under a heavy load is preset to be longer than said second delay time under said light load to, when ac voltage and/or ac current of said ac power supply passes through a zero point, close said switching means after said first delay time from a passing through time, and select said second delay time or said third delay time depending upon results of detection of said load condition detecting means so as to open said switching means after a selected delay time from a closing operation.

Claim 62

A dc power-supply unit comprising: rectifying means for converting ac power output from an ac power supply into dc power so as to feed to a load; an inductive element whose one end is connected to one terminal on a side of said rectifying means; switching means connected between the other end of said inductive element and the other terminal on said side of said rectifying means for short-circuiting at least one of a plurality of rectifying devices forming said rectifying means; and smoothing means connected in parallel with said switching means, and said dc power-supply unit further comprising: short-circuit current detecting means for detecting short-circuit current flowing in said inductive element; load condition detecting means for detecting magnitude of said load; and switch controlling means in which a delay time is preset to, when ac voltage and/or ac current of said ac power supply passes through a zero point, close said switching means after said delay time from a passing through time, and detect depending upon said load condition detecting means whether or not a value of said short-circuit current becomes a value preset according to said magnitude of said load after a closing operation so as to open said switch means when a decision is made that said short-circuit current becomes said predetermined value.

Claim 63

A dc power-supply unit comprising: rectifying means for converting ac power output from an ac power supply into dc power so as to feed to a load; an inductive element whose one end is connected to one terminal on a side of said rectifying means; switching means connected between the other end of said inductive element and the other terminal on said side of said rectifying means for short-circuiting at least one of a plurality of rectifying devices forming said rectifying means; and smoothing means connected in parallel with said switching means, and said dc power-supply unit further comprising: short-circuit current detecting means for detecting short-circuit current flowing in said inductive element; load condition detecting means for detecting magnitude of said load; and switch controlling means in which a delay time is preset to, when ac voltage and/or ac current of said ac power supply passes through a zero point, close said switching means after said delay time from a passing through time, and detect depending upon said load condition detecting means whether or not a value of said short-circuit current becomes a value preset according to said magnitude of said load after a closing operation so as to open said switch means when a decision is made that said short-circuit current becomes said predetermined value.

Claim 64

A dc power-supply unit comprising: rectifying means for converting ac power output from an ac power supply into dc power so as to feed to a load; an inductive element whose one end is connected to one terminal on a side of said rectifying means; switching means connected between the other end of said inductive element, and the other terminal on said side of said rectifying means for short-circuiting at least one of a plurality of rectifying devices forming said rectifying means; and smoothing means connected in parallel with said switching means, and said dc power-supply unit further comprising: load condition detecting means for detecting magnitude of said load; and switch controlling means in which a first delay time under a light load and a second delay time under a heavy load are preset such that said second delay time under said heavy load is shorter than said first delay time under said light load, and a third delay time under a light load and a fourth delay time under a heavy load are preset such that said fourth delay time under said heavy load is longer than said third delay time under said light load to, when ac voltage and/or ac current of said ac power supply passes through a zero point, select said first delay time or said second delay time depending upon results of detection of said load condition detecting means so as to close said switching means after a selected delay time from a passing through time, and to select said third delay time or said fourth delay time depending upon results of said detection of said load condition detecting means so as to open said switching means after a selected delay time from said passing through time.

Claim 65

A dc power-supply unit comprising: rectifying means for converting ac power output from an ac power supply into dc power so as to feed to a load; an inductive element whose one end is connected to one terminal on a side of said rectifying means; switching means connected between the other end of said inductive element, and the other terminal on said side of said rectifying means for short-circuiting at least one of a plurality of rectifying devices forming said rectifying means; and smoothing means connected in parallel with said switching means, and said dc power-supply unit further comprising: load condition detecting means for detecting magnitude of said load; and switch controlling means in which a first delay time under a light load and a second delay time under a heavy load are preset such that said second delay time under said heavy load is shorter than said first delay time under said light load, and a third delay time under a light load and a fourth delay time under a heavy load are preset such that said fourth delay time under said heavy load is longer than said third delay time under said light load to, when ac voltage and/or ac current of said ac power supply passes through a zero point, select said first delay time or said second delay time depending upon results of detection of said load condition detecting means so as to close said switching means after a selected delay time from a passing through time, and to select said third delay time or said fourth delay time depending upon results of said detection of said load condition detecting means so as to open said switching means after a selected delay time from said passing through time.