Power factor correction (PFC) controller

Claim 2

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; and third 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.

Claim 3

The controller of claim 1 , wherein the calculator comprises: a fifth transistor in which the emitter is coupled to the supply voltage; a sixth transistor in which the collector is coupled to the base and collector of the fifth transistor; an operational amplifier in which one input terminal is coupled to a second input voltage, and the other input terminal is coupled to the emitter of the sixth transistor, and the output is supplied to the base of the sixth transistor; a third resistor coupled to between the emitter of the sixth transistor and the ground; a seventh transistor configuring a current mirror together with the fifth transistor; eighth and ninth transistors in which the base and the collector of both are coupled to the collector of the seventh transistor; a fourth and fifth resistors in which each one end is coupled to the emitter of the eighth and ninth transistors, respectively; tenth and eleventh transistors in which the emitters are coupled to the other ends of the fourth and fifth resistors, respectively, and configure a differential pair, and the collectors are coupled to the ground and the first input voltage respectively; twelfth and thirteenth transistors in which the emitters are coupled to the bases of the tenth and eleventh transistors and the current source; fourteenth and fifteenth transistors in which the emitters are coupled to the supply voltage, respectively, and configure a current mirror; sixteenth and seventeenth transistors in which the collectors are coupled to the collectors of the fourteenth and fifteenth transistors, respectively, configuring a differential pair, and receive the voltage difference between the emitters of the eighth and ninth transistors between their bases; an eighteenth transistor in which the collector is coupled to the emitter of the sixteenth and seventeenth transistors; a nineteenth transistor, configuring a current mirror together with the eighteenth transistor, in which the emitter is coupled to the common collectors of the first and third transistors of the subtracter; twentieth transistor in which the emitter is coupled to the supply voltage, and the base and collector are coupled to the collector of the fifteenth transistor; twenty first transistor configuring a current mirror together with the twentieth transistor; sixth resistor coupled to between the collector of the twenty first transistor and the ground; and the voltage between the collector of the twenty first transistor and the sixth resistor is supplied to the comparator.