PFC apparatus for a converter operating in the borderline conduction mode

Claim 2

A power factor correction apparatus, for a switching power supply fed by an array of rectifying diodes and consisting of at least an input inductor, a contact of which is connected in series with a contact of said array, and of a power switch connected between the other contact of said array and the other contact of said input inductor, comprising: a) circuitry for identifying, in each cycle determined by the switching frequency of said power supply, whenever the instantaneous value of the current through said inductor reaches a minimal value; b) circuitry for switching said power switch to its conducting state in response to said minimal current through said inductor; c) circuitry for reflecting the current flowing through said inductor by a measurable or simulated parameter; and d) circuitry for providing indication, in each cycle, by using said parameter, said indication being related to the timing until the peak value of said current, that corresponds to a specific load, has been essentially reached, or to the time from the moment that said current reaches said minimal value until said timing, and for switching said power switch to its non-conducting state in response to said indication.

Claim 3

Apparatus according to claim 1 , further comprising: a) circuitry for sampling the output voltage; b) circuitry for generating a signal which reflects the deviation of said output voltage from a predetermined voltage value; and c) circuitry for modifying the value of one or more of said parameters in response to said signal, and for adjusting the timing at which said power switch is switched to its non-conducting state, thereby allowing the inductor current to reach a different peak value, for compensating said deviation, while keeping the portion, in each cycle, of the time period during which the power switch is in its non-conducting state.

Claim 4

Apparatus according to claim 1 , in which the minimal value is essentially zero.

Claim 5

Apparatus according to claim 2 , in which the deviation results from changes in the load.

Claim 6

Apparatus according to claim 2 , in which the deviation results from changes in the power line voltage.

Claim 7

Apparatus according to claim 1 , in which the circuitry for reflecting the current flowing through said inductor comprises: a) a capacitor that is charged/discharged by a combination of a constant current source being inactive during the time periods when the power switch is in its conducting state and a dependent current source for discharging said capacitor with a current that is proportional to the input inductor current, such that the voltage over said capacitor inversely reflects the value of/changes in, the current flowing through said input inductor; b) a first comparator, connected to said capacitor, for switching the power switch to its non-conducting state and for activating said constant current source whenever the voltage across said capacitor reaches a predetermined reference voltage; and c) a second comparator that samples the current flowing through said input inductor, for switching the power switch to its conducting state and for disactivating said constant current source whenever the current flowing through said input inductor reaches an essentially zero value.

Claim 8

Apparatus according to claim 1 , comprising: a) a timing circuitry for continuously sampling the output voltage of said converter and the input current passing through said converter, and for generating a cyclic intermediate signal, having in each cycle a portion of positive slope and a portion of negative slope, said positive slope having a duration being equal to the time required for said input current to decline from its maximum value, during said cycle, to a zero value, and said negative slope having a duration being equal to the time it takes said intermediate signal to decline from its maximum value to a reference value; b) a first controllable current source, for adjusting the rising rate of said positive slope portion of said intermediate signal; c) a second controllable current source, coupled to said timing circuitry, for adjusting the rate of decline of said negative portion of said intermediate signal and the rising rate of said positive slope portion of said intermediate signal, said second controllable current source having a magnitude that is smaller than the magnitude of said first controllable current source; d) a first controllable switch, coupled to the output of said controlled converter, for controlling the input current of said converter; e) a second controllable switch for connecting or disconnecting said first current source, for causing said rise and decline portions of said intermediate signal; and f) a drive circuit, coupled to said timing circuitry, for generating a switching signal from said intermediate signal for switching a first controllable switch for controlling said input current of said converter.

Claim 9

A power factor controller according to claim 7 , in which said timing circuitry comprises: a) a first means for comparing a voltage being a representative of the output voltage of said converter with a voltage reference; b) a second means for sensing whenever said input current reaches a zero value; and c) means for multiplying the output of said first means by a voltage being a representative of said input current, for adjusting said second controllable current source.

Claim 10

A power factor controller according to claim 7 , in which said driving circuit comprises a flip-flop, coupled to said timing circuit, that generates switching signal from the intermediate signal, for switching the first controllable switch.

Claim 11

A power factor controller according to claim 7 , in which said first controllable current source is controlled by a voltage being a representative of the output voltage of the converter that is controlled.

Claim 12

A power factor controller according to claim 7 , in which said second controllable current source is controlled by a voltage being a representative of the output voltage of the converter being controlled.

Claim 13

A power factor controller according to claim 7 , in which said timing circuitry comprises a capacitor, coupled to the second switch, to said second controllable current source and to one input of an amplifier, said capacitor being charged whenever said second switch is closed and discharged whenever said second switch is open, the voltage of said capacitor being the intermediate signal and compared to a reference voltage coupled to a second input of said amplifier of which output is coupled to the flip-flop.

Claim 14

A power factor controller according to claim 7 , in which said timing circuitry comprises: a) an ‘Absolute-value’ module (ABS), the input of which is coupled to the first and second current sources whenever the second switch is closed, and to said second current source whenever said second switch is open; b) a Voltage-Controlled-Oscillator (VCO) module, coupled to the output of the ABS module, having an output clock signal of which frequency being dependent on the value of the magnitude of the current being delivered from the output of said ABS module to the input of said VCO module; and c) an ‘up-down’ counter, coupled to the VCO module and to the flip-flop, said counter counts ‘up’ whenever said second switch is closed and ‘down’ whenever said second switch is open, said ‘up’ and ‘down’ counting rates are a function of said VCO frequency being a representative of the absolute value of the magnitude of the current passing through the input of the ABS module.

Claim 15

A power factor controller according to claim 7 , in which the timing circuitry further comprises a first oscillator having a constant frequency, for allowing to initialize/excite the operation of the converter and/or to resume normal operation, said first oscillator being inoperative in normal operation of said converter.

Claim 16

A power factor controller according to claim 7 , in which the timing circuitry further comprises a second oscillator having a constant frequency, for allowing to operate the converter at constant frequency, said frequency being adjusted so as to maintain the input current of the converter above zero.

Claim 17

A power factor controller according to claim 14 , in which the first oscillator and the second oscillator are the same oscillator, further comprising means for programming and/or for configuring and/or for switching said oscillator.

Claim 18

A power factor controller according to claim 7 , in which the first current source adjusts a rate of decline of the intermediate signal and the second current source adjusts a rate of rise of the intermediate signal, said second controllable current source being greater in magnitude in comparison with said first controllable current source.

Claim 19

A power factor controller according to claim 7 , in which the zero value input current of the converter is sensed by means of an analog comparator.

Claim 20

A power factor controller according to claim 7 , in which the zero value input current of the converter is sensed by digital means.

Claim 21

A power factor controller according to claim 7 , in which the zero value input current of the converter is sensed by a second inductor, being inductively coupled to the first inductor, said first inductor induces voltage on said second inductor.

Claim 22

A power factor controller according to claim 8 , in which the control circuit comprises: a) a first means for digitizing the output voltage of the converter; b) a second means for digitizing the input current of the converter; and c) means for processing the data gathered from said first and second digitizing means, for generating the switching signal for the first controllable switch.

Claim 23

A power factor controller according to claim 13 , in which the control circuit components are contained in a module that comprises five external contacts.

Claim 24

A power factor controller according to claim 13 , in which the control circuit components are contained in an integrated circuit (IC).

Claim 25

A power factor controller according to claim 22 , in which the input current sensing resistor and/or the output diode and/or the power switch are contained in, or being external to, a module that comprises five external contacts and/or to an integrated circuit (IC).

Claim 26

A power factor controller according to claim 15 , in which the first oscillator and the second oscillator are the same oscillator, further comprising means for programming and/or for configuring and/or for switching said oscillator.

Claim 27

A power factor controller according to claim 21 , in which the control circuit components are contained in a module that comprises five external contacts.

Claim 28

A power factor controller according to claim 26 , in which the input current sensing resistor and/or the output diode and/or the power switch are contained in, or being external to, a module that comprises five external contacts and/or to an integrated circuit (IC).

Claim 29

A power factor controller according to claim 21 , in which the control circuit components are contained in an integrated circuit (IC).

Claim 30

A power factor controller according to claim 28 , in which the input current sensing resistor and/or the output diode and/or the power switch are contained in, or being external to, a module that comprises five external contacts and/or to an integrated circuit (IC).

Claim 31

A power factor controller according to claim 23 , in which the input current sensing resistor and/or the output diode and/or the power switch are contained in, or being external to, a module that comprises five external contacts and/or to an integrated circuit (IC).