Switching power supply

Claim 2

A switching power supply for supplying DC output power to a load operable below a predetermined temperature comprising: first rectifier means to be connected with an AC power source (l), for rectifying a first AC voltage supplied by said AC power source (l) into a DC input voltage; electric power converting means (3, 4, 5) to be connected with said first rectifier means, for con­verting said input DC voltage into a desired DC output power, said electric power converting means including a DC-to-AC converting means (3) for converting control­lably said DC input voltage into a second AC voltage, transformer means (4) for stepping up said second AC voltage to a third AC voltage, and second rectifier means (5) for rectifying said third AC voltage and producing said DC output power to be supplied to said load; and first control means (8) including means (7) for detecting the temperature of said load, for control­ling said DC-to-AC converting means (3) on the basis of said detected temperature and a preset value for said DC output power.

Claim 3

A switching power supply according to Claim l, wherein said first control means (8) comprises: drive means (8l, 82) for driving said DC-to-AC converting means (3), in response to a control signal corresponding to said preset value; and means (90, 9l, 83-85 in Fig. 3; 83, 86 in Fig. 6; 84, 87-89, 90 in Fig. 8; 86-89 in Fig. 9) for compar­ing said detected temperature with a predetermined operating temperature for said load and adjusting said control signal, depending on the difference between said detected temperature and said predetermined operating temperature when said detected temperature is higher than said predetermined operating temperature, whereby the temperature of said load is kept below said predetermined operating temperature.

Claim 4

A switching power supply according to Claim l, wherein said transformer means includes a transformer (4) having a primary winding connected with said first rectifier means, said DC-to-AC converting means (3) includes at least a switching element (3l) connected in series with said primary winding and said first rectifier means, and said first control means includes drive means (8l) for driving said switching element (3l), duty ratio controlling means (82) for controlling said drive means (8l) so that said switching element is turned on and off with a duty ratio corresponding to a control signal and control signal generating means (9l, 83-85 in Fig. 3; 83, 86 in Fig. 6; 84, 87-89, 90 in Fig. 8; 86-89 in Fig. 9) for generating said control signal on the basis of said detected temperature and said preset value.

Claim 5

A switching power supply according to Claim 3, wherein said control signal generating means includes means (90, 9l, 83-85 in Fig. 3; 83, 86 in Fig. 6; 84, 87-89 in Fig. 8; 86-89 in Fig. 9) for comparing said detected temperature with a predetermined operating temperature for said load and adjusting said control signal, depending on the difference between said detec­ted temperature and said predetermined operating temper­ature when said detected temperature is higher than said predetermined operating temperature.

Claim 6

A switching power supply according to Claim 4, wherein said adjust means includes means (9l, 83-85 in Fig. 3; 84, 87-89 in Fig. 8) for supplying said control signal (Ps) corresponding to said preset value to said duty ratio controlling means as it is when said detected temperature is lower than said predetermined operating temperature, said duty ratio being determined by said preset value and said DC input voltage of said first rectifier means, and corrects said control signal (Ps) corresponding to said preset value, depending on the difference between said detected temperature and said predetermined operating temperature when said detected temperature is higher than said predetermined operating temperature.

Claim 7

A switching power supply according to Claim 4, wherein said adjust means includes means (83, 86 in Fig. 6; 86-89 in Fig. 9) for supplying said control signal (Ps) corresponding to said preset value to said duty ratio controlling means as it is when said detected tem­perature is lower than said predetermined operating tem­perature, and changes said control signal (Ps) to a signal level corresponding to said DC output power which is zero when said detected temperature exceeds said pre­determined operating temperature.

Claim 8

A switching power supply according to Claim l, wherein said transformer means (4 in Fig. l3, l5, 2l-23) includes a primary winding connected with said first rectifier means and at least a secondary winding coupled magnetically with said primary winding, said DC-to-AC converting means includes swich­ing means (3 in Fig. l3; 3l in Figs. l5, 2l-23) connect­ed between said primary winding and said first rectifier means and having a control input for switching said DC input voltage in response to the driving signal given to the control input to produce said second AC voltage to be applied to said transformer means, said switching means being switched on and off in response to said driving signal given to the control input, and said second rectifier means (50, 60 in Fig. l3; 5l, 52, 53, 54 in Figs. l5, 2l-23) includes a first voltage source (50) connected with said secondary winding of said transformer and outputting the voltage developed across said secondary winding during the on-­ period of said switching means and a second voltage source (60) connected with said secondary winding of said transformer and storing exciting energy in said transformer by using the exciting inductance of said transformer as a current source during the off-period of said switching means, said first voltage source and said second voltage source being connected in series.

Claim 9

A switching power supply according to Claim 7, wherein said second rectifier means includes a first diode (5l), which is conductive during the on-period of said switching means, and a second diode (52), which is conductive during the off-period of said switching means, both being connected with said secondary winding, said first voltage source includes a first capacitor (53), which is charged through said first diode, and said second voltage source includes a second capacitor (54), which is charged through said second diode.

Claim 10

A switching power supply according to Claim 8, wherein said first control means comprises: drive means (8l) producing said driving signal; duty ratio controlling means (82) for control­ling said drive means so that said switching means is driven with a duty ratio corresponding to said detected temperature and said preset value; and control signal generating means (9l, 83-85, 90 in Fig. 3; 83, 86 in Fig. 6; 84, 87-89, in Fig. 8; 86-89 in Fig. 9) for generating a control signal for control­ling said duty ratio controlling means on the basis of said detected temperature and said preset value.

Claim 11

l0. A switching power supply according to Claim 9, wherein said first control signal generating means includes means (90, 9l, 83-85 in Fig. 3; 83, 86 in Fig. 6; 84, 87-89 in Fig. 8; 86-89 in Fig. 9) for comparing said detected temperature with a predetermined operating temperature for said load and adjusting said control signal, depending on the difference between said detected temperature and said predetermined operating temperature when said detected temperature is higher than said predetermined operating temperature.

Claim 12

A switching power supply according to Claim l0, wherein said adjust means includes means (9l, 83-85, 90 in Fig. 3; 84, 87-89 in Fig. 8) for supplying said control signal (Ps) corresponding to said preset value to said duty ratio controlling means as it is when said detected temperature is lower than said predetermined opeating temperature, said duty ratio being determined by said preset value and said DC input voltage of said first rectifier means, and for correcting said control signal (Ps) corresponding to said preset value, depending on the difference between said detected tem­perature and said predetermined operating temperature when said detected temperature is higher than said pre­determined operating temperature.

Claim 13

A switching power supply according to Claim l0, wherein said adjust means includes means (83, 86 in Fig. 6; 86-89 in Fig. 9) for supplying said control signal (Ps) corresponding to said preset value to said duty ratio controlling means as it is when said detected temperature is lower than said predetermined operating temperature, and for changing said control signal (Ps) to a signal level corresponding to said DC output power which is zero when said detected temperature exceeds said predetermined operating temperature.

Claim 14

A switching power supply according to Claim 8, wherein the leakage inductance of said transformer and the value of said first capacitor are so set that the waveform of the current flowing through said secondary winding during the on-period of said switching means is oscillatory.

Claim 15

A switching power supply according to Claim l, wherein said transformer means (4) includes a primary winding connected with said first rectifier means and at least a secondary winding coupled magnetically with said primary winding, said DC-to-AC converting means includes switching means (3) connected between said primary winding and said first rectifier means and having a control input, for switching said DC input voltage, in response to the driving signal given to the control input, and for developing said second AC voltage to be applied to said transformer means, and a capacitor (304) connected in parallel with said switching means, said switching means being switched on and off, in response to said driving signal given to the control input, a resonance voltage being developed by the exciting inductance of said transformer and said capacitor across said switching means during the off-period of said switching means, and said first control means includes: means (307, 308-l, ..... in Fig. 38; 3l0, 3l3 in Fig. 39; 200, ll in Fig. 40; 3l6, 3ll′-l, ..... in Fig. 4l) for producing signals representing a plurality of valley points of said resonance voltage; drive means for outputting a pulse signal, which turns on said switching means, as said driving signal; and means (3l2, 309 in Fig. 38; 3l2, 3l3 in Fig. 39; 3l2, 3l6 in Figs. 40, 4l) for selecting one of the signals representing a plurality of valley points on the basis of said detected temperature and said preset value, whereby said drive means turns on said switch­ing means at a valley point of said resonance voltage corresponding to the signal representing the selected valley point, in response to said selected valley point.

Claim 16

A switching power supply according to Claim l4, wherein said second rectifier means includes a first voltage source connected with said secondary winding of said transformer, for outputting the voltage developed across said secondary winding during the on-period of said switching means and a second voltage source connected with said secondary winding of said transform­er, for storing exciting energy in said transformer by using the exciting inductance of said transformer as a current source during the off-period of said switching means, said first voltage source and said second voltage source being connected in series.

Claim 17

A switching power supply according to Claim l5, wherein said second rectifier means includes a first diode which is conductive during the on-period of said switching means, and a second diode which is conductive during the off-period of said switching means, both being connected with said secondary winding, said first voltage source includes a first capacitor which is charged through said first diode, and said second voltage source includes a second capacitor which is charged through said second diode.

Claim 18

A switching power supply according to Claim l6, wherein the leakage inductance of said transformer and the value of said first and the second capacitors are so set that the waveform of the current flowing through said secondary winding during the on-period of said switching means is oscillatory.

Claim 19

A switching power supply comprising: a transformer having a primary winding to be connected with a DC power source and at least a seconda­ry winding coupled with said primary winding; switching means connected with said primary winding in series, for connecting and disconnecting controllably said primary winding repeatedly with and from said DC power source; a first voltage source (50) connected with said secondary winding, to which electric power produced in said secondary winding during the on-period, during which said primary winding is connected with said DC power source, is supplied; a second voltage source (60) connected with said transformer, to which the energy stored in the exciting inductance of said transformer during said on-­period is supplied during the off-period, where said primary winding is disconnected from said DC power source; and means for controlling said switching means, said first and said second voltage source being connected in series and forming the output circuit for said switching power supply, said output electric power of said output circuit being supplied to the load (6).

Claim 20

A switching power supply comprising: a transformer having a primary winding to be connected with a DC power source and at least a seconda­ry winding coupled with said primary winding; switching means connected with said primary winding in series, for connecting and disconnecting controllably said primary winding repeatedly with and from said DC power source; a first voltage source (50) connected with said secondary winding, to which electric power produced in said secondary winding during the on-period, during which said primary winding is connected with said DC power source, is supplied; a second voltage source (60) connected with said transformer, to which the energy stored in the exciting inductance of said transformer during said on-­period is supplied during the off-period, where said primary winding is disconnected from said DC power source; and means for controlling said switching means, said first and said second voltage source being connected in series and forming the output circuit for said switching power supply, said output electric power of said output circuit being supplied to the load (6).

Claim 21

A switching power supply according to Claim l8, wherein said first voltage source is connected with said secondary winding and includes a first capacitor (53) which is charged through said first diode (5l) which is conductive during said on-period, and said second voltage source is connected with said secondary winding and includes a second capacitor (54) which is charged through said second diode (52) during said off-period.

Claim 22

A switching power supply according to Claim l9, wherein said control means comprises duty ratio con­trolling means (8l), which controls the duty ratio of said on-period to said off-period.

Claim 23

2l. A switching power supply according to Claim 20, wherein said duty ratio controlling means comprises means (l4l-l45 in Fig. l7) for controlling said duty ratio on the basis of an output setting signal represen­ting the desired output power of said switching power supply and the value of the voltage of said DC power source.

Claim 24

A switching power supply according to Claim l8, wherein said second voltage source is connected with said secondary winding.

Claim 25

A switching power supply according to Claim l8, wherein said transformer has another secondary winding magnetically coupled with said primary winding and said second voltage source is connected with said another secondary winding.

Claim 26

A switching power supply according to Claim l8, wherein said load includes a magnetron.

Claim 27

A switching power supply comprising: a transformer having a primary winding to be connected with a DC power source and at least a seconda­ry winding coupled with said primary winding; switching means connected with said primary winding in series, for connecting and disconnecting con­trollably said primary winding repeatedly with and from said DC power source; and secondary circuit means connected with said secondary winding, including at least a diode and at least a capacitor, for transforming the AC electric power produced in said secondary winding into a DC elec­tric power; wherein the leakage inductance of said trans­former and the value of said capacitor are so set that the waveform of the current flowing through said second­ary winding during the on-period of said switching means, during which said primary winding is connected with said DC power source, is oscillatory.

Claim 28

A switching power supply comprising: a transformer having a primary winding to be connected with a DC power source and at least a seconda­ry winding coupled with said primary winding; switching means connected with said primary winding in series, for connecting and disconnecting con­trollably said primary winding repeatedly with and from said DC power source; and secondary circuit means connected with said secondary winding, including at least a diode and at least a capacitor, for transforming the AC electric power produced in said secondary winding into a DC elec­tric power; wherein the leakage inductance of said trans­former and the value of said capacitor are so set that the waveform of the current flowing through said second­ary winding during the on-period of said switching means, during which said primary winding is connected with said DC power source, is oscillatory.

Claim 29

A switching power supply according to Claim 25, wherein said diode and said capacitor are connected with said secondary winding so that said capacitor is charged during said on-period through said diode, and said secondary circuit means includes another diode and another capacitor, said another diode and said another capacitor being connected with said secondary winding so that said another capacitor is charged through said another diode during the off-period of said switching means, during which said primary winding is disconnected from said DC power source.

Claim 30

A switching power supply comprising: a transformer having a primary winding to be connected with a DC power supply and at least a seconda­ry winding coupled with said primary winding; switching means connected with said primary winding in series, for connecting and disconnecting con­trollably said primary winding repeatedly with and from said DC power source; a capacitor connected with said switching means in parallel; secondary circuit means connected with said secondary winding, for transforming an AC electric power developed across said secondary winding into a DC electric power; drive means for driving said switching means; and means including means for detecting an arbitrary one of a plurality of valley points of an oscillating voltage developed across said switching means during the off-period during which said primary winding is disconnected from said DC power source, for controlling said driving means, whereby said driving means responds to said detection means and drives said switching means at a point of time corresponding to the detected valley point.

Claim 31

A switching power supply comprising: a transformer having a primary winding to be connected with a DC power supply and at least a seconda­ry winding coupled with said primary winding; switching means connected with said primary winding in series, for connecting and disconnecting con­trollably said primary winding repeatedly with and from said DC power source; a capacitor connected with said switching means in parallel; secondary circuit means connected with said secondary winding, for transforming an AC electric power developed across said secondary winding into a DC electric power; drive means for driving said switching means; and means including means for detecting an arbitrary one of a plurality of valley points of an oscillating voltage developed across said switching means during the off-period during which said primary winding is disconnected from said DC power source, for controlling said driving means, whereby said driving means responds to said detection means and drives said switching means at a point of time corresponding to the detected valley point.

Claim 32

A switching power supply according to Claim 27, wherein said controlling means (307, 308-l, ..... , 3l2, 3l4, in Fig. 38; 3l2, 3l0, 3l3 in Fig. 39; 3ll-l, ..... , 3l2, 3l5, 3l6 in Fig. 40; 3ll′-l, ..... , 3l2, 3l6, 320 in Fig. 4l) for selecting the valley point to be detected, depending on the desired DC output power.

Claim 33

A switching power supply according to Claim 27, wherein said secondary circuit means comprises: a first voltage source connected with said secondary winding, an electric power developed in said secondary winding during an on-period of said switching means being supplied to said first voltage source, said primary winding is connected with said DC power source during said on-period; and a second voltage source connected with said transformer, an energy stored in the exciting inductance of said transformer during said on-period being supplied during said off-period, said first and said second voltage sources being connected in series and the DC output power being supplied to the load from said first and said second voltage sources connected in series.