Power factor correction control circuit for regulating the current waveshape in a switching power supply

• US 6,275,397 B1
• Filed: 06/27/2000
• Issued: 08/14/2001
• Est. Priority Date: 06/27/2000
• Status: Expired due to Fees

• Current Assignee: Power-One Incorporated (ABB Limited)
• Original Assignee: Power-One Incorporated (ABB Limited)
• Inventors: McClain, Edward L.
• Primary Examiner(s): BERHANE, ADOLF D
• Application Number:
  US09/604,381
• Time in Patent Office: 413 Days
• Field of Search: 363/84, 363/89, 363/34, 363/78, 363/127, 363/37
• US Class Current: 363/89
• CPC Class Codes: H02M 1/4225 using a non-isolated boost converter
• CPC Class Codes: Y02B 70/10 Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes

Abstract

A switching power supply comprises an AC rectifier adapted to receive an AC line voltage and provide an input voltage (V_IN) therefrom having a haversine waveform. A switching power converter is connected to the AC rectifier and provides a DC output voltage (V_OUT) for a load. The switching power converter comprises an inductor and a power switch adapted to control current in the inductor. A pulse width modulator provides a drive signal to the power switch having a variable duty cycle to regulate current provided to the load by the switching power converter. A power factor correction circuit is adapted to control operation of the pulse width modulator so that a waveshape of the current from the AC rectifier matches the output voltage (V_OUT) with changes in the input voltage (V_IN) and load. More particularly, the power factor correction circuit further comprises a voltage error circuit providing a voltage error signal corresponding to a difference between the output voltage (V_OUT) and a reference voltage, a differential amplifier circuit generating a current program signal based in part on the voltage error signal, including an amplifier circuit to amplify a scaled input voltage (V_IN) signal with gain determined by the voltage error signal, and a current error circuit controlling the pulse width modulator based on the current program signal and a current sense signal corresponding to the current from the AC rectifier. The amplifier circuit further comprises a field effect transistor (FET) biased in a saturation condition to thereby provide a resistance that varies in accordance with the voltage error signal. The gain of the amplifier circuit is determined by the resistance. The differential amplifier circuit further comprises a second amplifier circuit adapted to amplify a difference between the scaled input voltage (V_IN) signal and the amplified scaled input voltage (V_IN) signal from the first amplifier circuit.

Claims

1. A switching power supply, comprising

an AC rectifier adapted to receive an AC line voltage and provide an input voltage (V_IN) therefrom having a haversine waveform;

a switching power converter connected to the AC rectifier and providing a DC output voltage (V_OUT) for a load, said switching power converter comprising an inductor and a power switch adapted to control current in said inductor;

a pulse width modulator providing a drive signal to said power switch having a variable duty cycle to regulate current provided to said load by said switching power converter; and

a power factor correction circuit adapted to control operation of said pulse width modulator so that a waveshape of said current from said AC rectifier matches said output voltage (V_OUT) with changes in said input voltage (V_IN) and said load, said power factor correction circuit further comprising;

voltage error means for providing a voltage error signal corresponding to a difference between said output voltage (V_OUT) and a reference voltage;

differential amplifier means for generating a current program signal based in part on said voltage error signal, said differential amplifier means comprising a first amplifier circuit adapted to amplify a scaled input voltage (V_IN) signal with gain determined by said voltage error signal; and

current error means for controlling said pulse width modulator based on said current program signal and a current sense signal corresponding to said current from said AC rectifier such that said pulse width modulator increases the duty factor of said power switch when the sum of said current sense signal and said current program signal is positive and decreases the duty factor of said power switch when the sum of said current sense signal and said current program signal is negative.

2. The switching power supply of claim 1, wherein said first amplifier circuit further comprises a field effect transistor (FET) biased in a saturation condition to thereby provide a resistance that varies in accordance with said voltage error signal, wherein said gain of said first amplifier circuit is determined by said resistance.

3. The switching power supply of claim 1, wherein said differential amplifier means further comprises a second amplifier circuit adapted to amplify a difference between said scaled input voltage (V_IN) signal and said amplified scaled input voltage (V_IN) signal from said first amplifier circuit.

4. The switching power supply of claim 1, wherein said power factor correction circuit further comprises means for defining a reference voltage.

5. The switching power supply of claim 1, wherein said power factor correction circuit further comprises means for limiting said current in said inductor of said switching power converter.

6. The switching power supply of claim 1, wherein said power factor correction circuit further comprises means for reducing scale of said input voltage (V_IN) signal to provide said scaled input voltage (V_IN) signal.

7. The switching power supply of claim 1, wherein said switching power converter further comprises a boost inverter.

8. A power factor correction circuit for use in a switching power supply comprising an AC rectifier adapted to receive an AC line voltage and provide an input voltage (V_IN) therefrom having a haversine waveform, a switching power converter connected to the AC rectifier and providing a DC output voltage (V_OUT) for a load, said switching power converter comprising an inductor and a power switch adapted to control current in said inductor, and a pulse width modulator providing a drive signal to said power switch having a variable duty cycle to regulate current provided to said load by said switching power converter, said power factor correction circuit being adapted to control operation of said pulse width modulator so that a waveshape of said current from said AC rectifier matches said output voltage (V_OUT) with changes in said input voltage (V_IN) and said load, said power factor correction circuit further comprising:

voltage error means for providing a voltage error signal corresponding to a difference between said output voltage (V_OUT) and a reference voltage;

differential amplifier means for generating a current program signal based in part on said voltage error signal, said differential amplifier means comprising a first amplifier circuit adapted to amplify a scaled input voltage (V_IN) signal with gain determined by said voltage error signal; and

current error means for controlling said pulse width modulator based on said current program signal and a current sense signal corresponding to said current from said AC rectifier such that said pulse width modulator increases the duty factor of said power switch when the sum of said current sense signal and said current program signal is positive and decreases the duty factor of said power switch when the sum of said current sense signal and said current program signal is negative.

9. The power factor correction circuit of claim 8, wherein said first amplifier circuit further comprises a field effect transistor (FET) biased in a saturation condition to thereby provide a resistance that varies in accordance with said voltage error signal, wherein said gain of said first amplifier circuit is determined by said resistance.

10. The power factor correction circuit of claim 8, wherein said differential amplifier means further comprises a second amplifier circuit adapted to amplify a difference between said scaled input voltage (V_IN) signal and said amplified scaled input voltage (V_IN) signal from said first amplifier circuit.

11. The power factor correction circuit of claim 8, further comprising means for defining a reference voltage.

12. The power factor correction circuit of claim 8, further comprising means for limiting said current in said inductor of said switching power converter.

13. The power factor correction circuit of claim 8, further comprising means for reducing scale of said input voltage (V_IN) signal to provide said scaled input voltage (V_IN) signal.

14. In a switching power supply comprising an AC rectifier adapted to receive an AC line voltage and provide an input voltage (V_IN) therefrom having a haversine waveform, a switching power converter connected to the AC rectifier and providing a DC output voltage (V_OUT) for a load, said switching power converter comprising an inductor and a power switch adapted to control current in said inductor, and a pulse width modulator providing a drive signal to said power switch having a variable duty cycle to regulate current provided to said load by said switching power converter, a method for correcting power factor of said switching power supply whereby a waveshape of said current from said AC rectifier matches said output voltage (V_OUT) with changes in said input voltage (V_IN) and said load comprises:

providing a voltage error signal corresponding to a difference between said output voltage (V_OUT) and a reference voltage;

generating a current program signal by amplifying a scaled input voltage (V_IN) signal with gain determined by said voltage error signal; and

controlling said pulse width modulator based on said current program signal and a current sense signal corresponding to said current from said AC rectifier such that said pulse width modulator increases the duty factor of said power switch when the sum of said current sense signal and said current program signal is positive and decreases the duty factor of said power switch when the sum of said current sense signal and said current program signal is negative.

15. The method of claim 14, wherein said generating step further comprises biasing a field effect transistor (FET) in a saturation condition to thereby provide a resistance that varies in accordance with said voltage error signal, wherein said gain of said first amplifier circuit is determined by said resistance.

16. The method of claim 14, wherein said generating step further comprises amplifying a difference between said scaled input voltage (V_IN) signal and said amplified scaled input voltage (V_IN) signal.

17. The method of claim 14, further comprising defining a reference voltage.

18. The method of claim 14, further comprising limiting said current in said inductor of said switching power converter.

19. The method of claim 14, further comprising reducing scale of said input voltage (V_IN) signal to provide said scaled input voltage (V_IN) signal.