Power factor correction circuit and method of driving the same

1. A power factor correction circuit, comprising:

a power transfer element configured to receive an input voltage with an input current corresponding to the input voltage flowing through the power transfer element; and

a switch connected to the power transfer element and configured to control an output voltage generated by the current flowing through the power transfer element,

wherein the power factor correction circuit is configured to detect a zero voltage edge timing of the input voltage by detecting the input voltage, generate a reference clock signal having a frequency that varies according to the detected edge timing, generate a reference signal using the reference clock signal, generate an error amplification signal based on a difference between the output voltage and a predetermined error reference signal, generate the amplification reference signal by multiplying the reference signal by the error amplification signal, and control a switching operation of the switch using the amplification reference signal and a detection signal corresponding to a current flowing through the switch.

2. The power factor correction circuit of claim 1 , further comprising:

a capacitor charged to the input current and configured to generate the output voltage during a period in which the switch is turned off;

an error amplifier configured to generate the error amplification signal based on the difference between the output voltage and the predetermined error reference signal;

a reference signal generator configured to generate the reference signal corresponding to the input voltage; and

a power factor correction controller configured to turn on the switch in synchronization with the clock signal having a predetermined cycle and to turn off the switch when the detection signal reaches the amplification reference signal.

3. The power factor correction circuit of claim 2 , wherein

the reference signal generator comprises:

a voltage detector configured to generate an input detection voltage corresponding to the input voltage;

a zero voltage detector configured to compare the input detection voltage and a predetermined first reference value, and generate a zero voltage detection signal having a first or second level according to the comparison result;

a reference clock generator configured to generate the reference clock signal having a frequency that varies according to one cycle of the zero voltage detection signal;

a digital sine wave generator synchronized with the zero voltage detection signal in response to the reference clock signal and the zero voltage detection signal and configured to generate a digital signal that increases according to the reference clock signal during one half of the one cycle of the zero voltage detection signal and that decreases according to the reference clock signal during the other half of the one cycle of the zero voltage detection signal; and

a digital analog converter configured to generate the reference signal having a voltage level corresponding to a voltage level of the digital signal.

4. The power factor correction circuit of claim 3 , wherein

the voltage detector comprises:

a detection current generator configured to generate a current corresponding to the input voltage, and

a current-voltage converter configured to generate a voltage corresponding to the current.

5. The power factor correction circuit of claim 3 , wherein

the zero voltage detector is configured to

generate the zero voltage detection signal of the first level when the input detection voltage is the first reference value or more and generate the zero voltage detection signal of the second level when the input detection voltage is the first reference value or less.

6. The power factor correction circuit of claim 3 , wherein

the reference clock generator is configured to

detect a reference edge timing at which the zero voltage detection signal changes from the first level to the second level, calculate the one cycle of the zero voltage detection signal using two consecutive reference edge timings, and generate the rising and falling reference clock signal rising and falling a predetermined number of times during the one calculated cycle.

7. The power factor correction circuit of claim 3 , wherein

the reference clock generator is configured to

detect a predetermined edge timing as reference edge timing during a period from edge timing at which the zero voltage detection signal changes from the first level to the second level to edge timing at which the zero voltage detection signal changes from the second level to the first level, calculate the one cycle of the zero voltage detection signal using two consecutive reference edge timings, and generate the rising and falling reference clock signal a predetermined number of times during the one calculated cycle.

8. The power factor correction circuit of claim 1 , wherein

the power transfer element includes an inductor.

9. The power factor correction circuit of claim 8 , wherein:

one terminal of the inductor is connected to one terminal of the switch; and

the power factor correction circuit further comprises a diode having an anode connected to one terminal of the inductor, wherein a capacitor is connected to a cathode of the diode.

10. The power factor correction circuit of claim 1 , wherein

the power transfer element comprises

a transformer comprising a primary side coil having one terminal to which the input voltage is applied and another terminal to which the switch is connected, and a secondary side coil having a predetermined turn ratio for the primary side coil, and the current flowing through the power transfer element corresponds to a current flowing through the primary side coil.

11. The power factor correction circuit of claim 10 , further comprising

a diode having an anode connected to one terminal of the secondary side coil, wherein a capacitor is connected to a cathode of the diode.

12. The power factor correction circuit of claim 1 , further comprising

a bridge diode configured to generate a full-wave rectified sine wave input voltage by rectifying an input AC power source.

13. A method of driving a power factor correction circuit, comprising a power transfer element through which an input current corresponding to an input voltage flows and a switch connected to the power transfer element and configured to control an output voltage generated by the current flowing through the power transfer element, the method comprising the steps of:

generating a reference signal corresponding to the input voltage;

generating an error amplification signal corresponding to the output voltage;

generating an amplification reference signal by multiplying the error amplification signal and the reference signal;

comparing the amplification reference signal and a detection signal corresponding to an input current by the input voltage; and

controlling a switching operation of the switch according to the comparison result.

14. The method of claim 13 , wherein

the step of controlling the switching operation of the switch includes the steps of:

turning off the switch when the detection signal reaches the amplification reference signal; and

turning on the switch every cycle of a clock signal having a predetermined cycle.

15. The method of claim 13 , wherein

the step of generating the reference signal includes the steps of:

generating an input detection voltage corresponding to the input voltage;

comparing the input detection voltage and a predetermined first reference value, and generating a zero voltage detection signal having a first or second level according to the comparison result;

generating a reference clock signal having a frequency that varies according to one cycle of the zero voltage detection signal;

generating a digital signal that increases according to the reference clock signal during one half of the one cycle of the zero voltage detection signal and decreases according to the reference clock signal during the other half of the one cycle of the zero voltage detection signal in synchronization with the zero voltage detection signal using the reference clock signal and the zero voltage detection signal; and

generating the reference signal having a voltage level corresponding to a voltage level of the digital signal.

16. The method of claim 15 , wherein

the step of generating the zero voltage detection signal includes

generating the zero voltage detection signal of the first level when the input detection voltage is the first reference value or more, and generating the zero voltage detection signal of the second level when the input detection voltage is the first reference value or less.

17. The method of claim 15 , wherein

the step of generating the reference clock signal includes

detecting reference edge timing at which the zero voltage detection signal changes from the first level to the second level, calculating the one cycle of the zero voltage detection signal using two consecutive reference edge timings, and generating the rising and falling reference clock signal a predetermined number of times during the one calculated cycle.

18. The method of claim 15 , wherein

the step of generating the reference clock signal includes

detecting as reference edge timing predetermined edge timing as reference edge timing during a period from edge timing at which the zero voltage detection signal changes from the first level to the second level to edge timing at which the zero voltage detection signal changes from the second level to the first level, calculating the one cycle of the zero voltage detection signal using two consecutive reference edge timings, and generating the rising and falling reference clock signal a predetermined number of times during the one calculated cycle.