Patent ID: 6175218
Filing Date: 2001-01-16
Classification: G05F,H02M,Y02B,Y02P

Abstract:
A Power Factor correction (PFC) controller, comprising:a converter including a transformer coupling the primary coil to input voltage, a switch controlling the current flowing to the primary coil, and a first diode and a first capacitor rectifying an output voltage of the primary coil and supplying the rectified voltage to a load;an error amplification unit including an error amplifier amplifying the difference between a voltage proportional to an output voltage of the converter and a first reference voltage, and a subtracter subtracting an output voltage of the error amplifier from a second reference voltage;a calculator receiving a first and a second input voltages proportional to the input voltage of the converter and an output voltage of the subtracter as inputs respectively, and outputting a voltage proportional to the first input voltage and the output voltage of the subtracter and inversely proportional to the second input voltage;a comparator comparing a detection voltage which detects the current flowing to the switch with the output voltage of the calculator;a zero current detection unit detecting the zero current of the secondary coil of the transformer;a switching driver controlling the switch to ON or OFF responsive to the output voltage of the comparator and the output of the zero current detection unit;wherein the subtracter comprises:first and second transistors receiving the second reference voltage and the output voltage of the error amplifier through their respective bases, and configuring a differential pair;first and second resistors coupled to between each emitter of the first and second transistors and a current source; andthird and fourth transistors in which the collectors of the third and fourth transistors are coupled to the collectors of the first and second transistors, respectively, and configure a current mirror.