POWER SUPPLY CIRCUIT WITH PFC FUNCTION, AND AUTOMATIC GAIN CONTROL CIRCUIT THEREFOR AND CONTROL METHOD THEREOF

• US 20130250631A1
• Filed: 03/18/2013
• Published: 09/26/2013
• Est. Priority Date: 03/24/2012
• Status: Active Grant

• Current Assignee: Richtek Technology Corporation (MediaTek, Inc.)
• Original Assignee: Richtek Technology Corporation (MediaTek, Inc.)
• Inventors: Liao, Chia-Wei, Liu, Jing-Meng
• Granted Patent: US 9,337,716 B2
• Time in Patent Office: Days
• US Class Current: 363/44
• CPC Class Codes: G05F 3/262 using field-effect transistors only
• CPC Class Codes: H02M 1/0009 Devices or circuits for detecting current in a converter
• CPC Class Codes: H02M 1/08 Circuits specially adapted for the generation of control voltages for semiconductor devices incorporated in static converters
• CPC Class Codes: H02M 1/126 using passive filters
• CPC Class Codes: H02M 1/42 Circuits or arrangements for compensating for or adjusting power factor in converters or inverters
• CPC Class Codes: H02M 1/4208 Arrangements for improving power factor of AC input
• 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

The present invention discloses a power supply circuit with power factor correction (PFC) function, and an automatic gain control circuit therefor and a control method thereof. The power supply circuit includes the automatic gain control circuit and a load driver circuit. The automatic gain control circuit converts an input voltage to a regulation voltage, and the load driver circuit generates an output current according to the regulation voltage. The automatic gain control circuit automatically adjust the regulation voltage such that the regulation voltage has a substantially fixed amplitude or fixed average value under different input voltages of different specifications, and the output current provided by the load driver circuit varies in phase with the input voltage to provide a PFC function.

Claims

1. A power supply circuit, comprising:

an automatic gain control circuit, including;

a voltage-to-current converter circuit for converting an input voltage to a regulation current;

a current-to-voltage converter circuit, which is coupled to the voltage-to-current converter circuit, for converting the regulation current to a regulation voltage;

a low-pass filter circuit, which is coupled to the current-to-voltage converter circuit, for obtaining a low frequency signal from the regulation voltage; and

a comparison circuit, which is coupled to the low-pass filter circuit, for generating a control signal according to the low frequency signal and a reference voltage; and

a load driver circuit, which is coupled to the current-to-voltage converter circuit, for converting the input voltage or the regulation voltage to the output voltage and supplying an output current, wherein the output current is in phase with the regulation voltage;

wherein the control signal is inputted to the voltage-to-current converter circuit or the current-to-the voltage converter circuit, for adjusting a conversion ratio from the input voltage to the regulation current, or from the regulation current to the regulation voltage.

2. The power supply circuit of claim 1, wherein the voltage-to-current converter circuit includes:

a differential amplifier circuit, for generating a differential amplified signal according to the input voltage and a regulation current feedback signal;

a transistor, which is coupled to the differential amplifier circuit, for operating to generate the regulation current according to the differential amplified signal; and

a variable resistor circuit, which is coupled to the transistor, for generating the regulation current feedback signal according to the regulation current, wherein a resistance of the variable resistor circuit is controlled by the control signal.

3. The power supply circuit of claim 2, wherein the variable resistor circuit includes a metal oxide semiconductor (MOS) device, which has a resistance controlled by the control signal.

4. The power supply circuit of claim 2, wherein the current-to-voltage circuit includes:

a current mirror circuit, for generating a duplicated regulation current by duplicating the regulation current; and

an impedance circuit, which is coupled to the current mirror circuit, for converting the duplicated regulation current to the regulation voltage.

5. The power supply circuit of claim 1, wherein the current-to-voltage converter circuit includes:

a current mirror circuit, for generating a duplicated regulation current by duplicating the regulation current; and

a variable resistor circuit, which is coupled to the current mirror circuit, for converting the duplicated regulation current to the regulation voltage, wherein the variable resistor circuit has a resistance controlled by the control signal.

6. The power supply circuit of claim 5, wherein the variable resistor circuit includes a metal oxide semiconductor (MOS) device, which has a resistance controlled by the control signal.

7. The power supply circuit of claim 1, wherein the load driver circuit includes:

a differential amplifier circuit, for generating a differential amplified signal according to the regulation voltage and a current sense signal;

a power stage circuit, for operating at least one power switch therein according to the differential amplified signal, to convert the input voltage to the output voltage and to supply an output current; and

a current sense circuit, which is coupled to the differential amplifier circuit, for generating the current sense signal according to the output current or a signal which is related to the output current.

8. The power supply circuit of claim 2, wherein the voltage-to-current converter circuit further includes an upper limit gain determination circuit, which is connected to the variable resistor circuit in series, for determining an upper limit of a gain of the automatic gain control circuit.

9. The power supply circuit of claim 5, wherein the voltage-to-current converter circuit further includes an upper limit gain determination circuit, which is connected to the variable resistor circuit in series, for determining an upper limit of a gain of the automatic gain control circuit.

10. The power supply circuit of claim 2, wherein the voltage-to-current converter circuit further includes a lower limit gain determination circuit, which is connected to the variable resistor circuit in parallel, for determining a lower limit of a gain of the automatic gain control circuit.

11. The power supply circuit of claim 5, wherein the voltage-to-current converter circuit further includes a lower limit gain determination circuit, which is connected to the variable resistor circuit in parallel, for determining a lower limit of a gain of the automatic gain control circuit.

12. The power supply circuit of claim 4, wherein the current mirror circuit further includes a constant current source, for determining a minimum level of the regulation voltage.

13. The power supply circuit of claim 5, wherein the current mirror circuit further includes a constant current source, for determining a minimum level of the regulation voltage.

14. An automatic gain control circuit of a power supply circuit, wherein the power supply circuit is for converting an input voltage to an output voltage and supplying an output current, wherein the output current is in phase with the input voltage, the automatic gain control circuit comprising:

a voltage-to-current converter circuit, for converting the input voltage to a regulation current;

a current-to-voltage converter circuit, which is coupled to the voltage-to-current converter circuit, for converting the regulation current to a regulation voltage;

a low-pass filter circuit, which is coupled to the current-to-voltage converter circuit, for obtaining a low frequency signal from the regulation voltage; and

a comparison circuit, which is coupled to the low-pass filter circuit, for generating a control signal according to the low frequency signal and a reference voltage;

wherein the control signal is inputted to the voltage-to-current converter circuit or the current-to-the voltage converter circuit, for adjusting a conversion ratio from the input voltage to the regulation current, or from the regulation current to the regulation voltage.

15. The automatic gain control circuit of claim 14, wherein the voltage-to-current converter circuit includes:

a differential amplifier circuit, for generating a differential amplified signal according to the input voltage and a regulation current feedback signal;

a transistor, which is coupled to the differential amplifier circuit, for operating to generate the regulation current according to the differential amplified signal; and

a variable resistor circuit, which is coupled to the transistor, for generating the regulation current feedback signal according to the regulation current, wherein a resistance of the variable resistor circuit is controlled by the control signal.

16. The automatic gain control circuit of claim 15, wherein the variable resistor circuit includes a metal oxide semiconductor (MOS) device, which has a resistance controlled by the control signal.

17. The automatic gain control circuit of claim 15, wherein the current-to-voltage circuit includes:

a current mirror circuit, for generating a duplicated regulation current by duplicating the regulation current; and

an impedance circuit, which is coupled to the current mirror circuit, for converting the duplicated regulation current to the regulation voltage.

18. The automatic gain control circuit of claim 14, wherein the current-to-voltage converter circuit includes:

a current mirror circuit, for generating a duplicated regulation current by duplicating the regulation current; and

a variable resistor circuit, which is coupled to the current mirror circuit, for converting the duplicated regulation current to the regulation voltage, wherein the variable resistor circuit has a resistance controlled by the control signal.

19. The automatic gain control circuit of claim 18, wherein the variable resistor circuit includes a metal oxide semiconductor (MOS) device, which has a resistance controlled by the control signal.

20. The automatic gain control circuit of claim 15, wherein the voltage-to-current converter circuit further includes an upper limit gain determination circuit, which is connected to the variable resistor circuit in series, for determining an upper limit of a gain of the automatic gain control circuit.

21. The automatic gain control circuit of claim 18, wherein the voltage-to-current converter circuit further includes an upper limit gain determination circuit, which is connected to the variable resistor circuit in series, for determining an upper limit of a gain of the automatic gain control circuit.

22. The automatic gain control circuit of claim 15, wherein the voltage-to-current converter circuit further includes a lower limit gain determination circuit, which is connected to the variable resistor circuit in parallel, for determining a lower limit of a gain of the automatic gain control circuit.

23. The automatic gain control circuit of claim 18, wherein the voltage-to-current converter circuit further includes a lower limit gain determination circuit, which is connected to the variable resistor circuit in parallel, for determining a lower limit of a gain of the automatic gain control circuit.

24. The automatic gain control circuit of claim 17, wherein the current mirror circuit further includes a constant current source, for determining a minimum level of the regulation voltage.

25. The automatic gain control circuit of claim 18, wherein the current mirror circuit further includes a constant current source, for determining a minimum level of the regulation voltage.

26. A control method of an automatic gain control circuit for use in a power supply circuit, wherein the power supply circuit is for converting an input voltage to an output voltage and supplying an output current, wherein the output current is in phase with a regulation voltage, the control method comprising:

converting the input voltage to a regulation current;

converting the regulation current to a regulation voltage;

filtering the regulation voltage to obtain a low frequency signal; and

generating a control signal according to the low frequency signal;

wherein the control signal is for adjusting a conversion ratio from the input voltage to the regulation current, or from the regulation current to the regulation voltage.

27. The control method of claim 26, further comprising:

determining an upper limit conversion ratio and/or a lower limit conversion ratio from the input voltage to the regulation current to determine an upper limit of a gain and/or a lower limit of again of the automatic gain control circuit.

28. The control method of claim 26, further comprising:

determining an upper limit conversion ratio or a lower limit conversion ratio from the regulation current to the regulation voltage to determine an upper limit of a gain or a lower limit of a gain of the automatic gain control circuit.

29. The control method of claim 26 further comprising:

determining a minimum level of the regulation voltage.

30. A power supply circuit, for generating an output current according to an input voltage, wherein the output current has a substantially same average value under different input voltages of different specifications, the power supply circuit comprising:

an automatic gain control circuit, for generating a regulation signal which is in phase with the input voltage, wherein the regulation signal has a substantially same amplitude or average value under different input voltages of different specifications; and

a load driver circuit, controlled by the regulation signal with an open loop connection, for generating the output current.

31. The power supply circuit of claim 30, wherein the load driver circuit includes a control circuit and a power stage circuit, wherein the control circuit receives the regulation signal with an open loop connection and generates a driving signal for controlling the power stage circuit to generate the output current according to the regulation signal.

32. The power supply circuit of claim 30, wherein the automatic gain control circuit includes:

a voltage-to-current converter circuit for converting an input voltage to a regulation current;

a current-to-voltage converter circuit, which is coupled to the voltage-to-current converter circuit, for converting the regulation current to a regulation voltage;

a low-pass filter circuit, which is coupled to the current-to-voltage converter circuit, for obtaining a low frequency signal from the regulation voltage; and

a comparison circuit, which is coupled to the low-pass filter circuit, for generating a control signal according to the low frequency signal and a reference voltage to control a parameter in the voltage-to-current converter circuit, such that the regulation voltage maintains at a substantially same amplitude or average value under different input voltages of different specifications, wherein the regulation signal is the regulation voltage or a signal derived from the regulation voltage.

33. The power supply circuit of claim 30, wherein the automatic gain control circuit includes:

a voltage-to-current converter circuit for converting an input voltage to a regulation current;

a current-to-voltage converter circuit, which is coupled to the voltage-to-current converter circuit, for converting the regulation current to a regulation voltage;

a low-pass filter circuit, which is coupled to the current-to-voltage converter circuit, for obtaining a low frequency signal from the regulation voltage; and

a comparison circuit, which is coupled to the low-pass filter circuit, for generating a control signal according to the low frequency signal and a reference voltage to control a parameter in the current-to-voltage converter circuit, such that the regulation voltage maintains at a substantially same amplitude or average value under different input voltages of different specifications, wherein the regulation signal is the regulation voltage or a signal derived from the regulation voltage.

34. The power supply circuit of claim 32, wherein the comparison circuit is a differential amplifier circuit.

35. The power supply circuit of claim 33, wherein the comparison circuit is a differential amplifier circuit.