Power supply circuit with pfc function, and automatic gain control circuit therefor and control method thereof

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.

1 - 25 . (canceled) 
     
     
         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 filtered signal; and   generating a control signal according to the filtered 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 a gain 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.