Power factor correction circuit with calculated duty compensation and driving method thereof
Provided is a power factor correction circuit including an inductor having one end to which an input voltage is applied; a power switch connected between another end of the inductor and the ground, and configured to control an output of the power factor correction circuit; and a power factor correction controller configured to calculate a duty of the power switch on the basis of an output detection voltage corresponding to the output and an inductor current flowing through the inductor, calculate conduction-period information regarding a conduction period in which the inductor current flows in one switching cycle of the power switch, and compensate the calculated duty on the basis of the conduction-period information.
1. A controller for a power factor correction (PFC) circuit, the controller comprising:
a time demodulator configured to generate a conduction detection signal in response to a zero-current detection signal, the conduction detection signal indicating a zero-current duration of an inductor current; and
a duty controller configured to generate conduction-period information in response to the conduction detection signal, the conduction-period information being associated with a conduction period in which the inductor current flows through a power switch, and to generate a duty control signal in response to the conduction-period information,
wherein a value of the conduction-period information decreases as a value of the conduction detection signal increases when the PFC circuit operates in a first mode and is substantially constant when the PFC circuit operates in a second mode.
2. The controller of claim 1 , wherein the first mode is a discrete conduction mode (DCM) and the second mode is a continuous conduction mode (CCM), and the inductor current keeps having a magnitude greater than zero during an entire switching cycle of the power switch when the PFC circuit operates in the CCM.
3. The controller of claim 1 , wherein the duty controller comprises:
a conduction period calculator circuit generating the conduction-period information in response to the conduction detection signal; and
a duty compensator circuit generating the duty control signal in response to the conduction-period information and duty information.
4. The controller of claim 1 , wherein the duty controller calculates the conduction-period information by subtracting the value of the conduction detection voltage from a predetermined reference value.
5. The controller of claim 1 , wherein the time demodulator generates the conduction detection signal by sampling a reference signal synchronized with a switching frequency of the power switch at a detected zero-cross time and holding a sampled reference signal to generate the conduction detection voltage.
6. The controller of claim 1 , wherein the conduction-period information has a maximum value when the PFC circuit operates in the second mode.
7. The controller of claim 1 , further comprising:
a comparator comparing the duty control signal with a predetermined reference signal synchronized with a switching frequency of the power switch; and
a flip-flop generating a gate signal to control the power switch in response to a comparison result.
8. The controller of claim 1 , wherein, when the PFC circuit operates in the first mode, the duty controller decreases a value of the duty control signal by decreasing the value of the conduction-period information as the zero-current duration of the inductor current increases.
9. The controller of claim 3 , wherein duty controller further comprises a duty calculator generating the duty information in response to line-current information and an output error voltage, the line-current information being associated with an average inductor current.
10. The controller of claim 5 , wherein the reference signal has a sawtooth waveform that decreases with a predetermined slope in a switching cycle of the power switch.
11. The controller of claim 5 , wherein the reference signal has a sawtooth waveform that increases with a predetermined slope in a switching cycle of the power switch.
12. The controller of claim 9 , wherein the duty compensator circuit generates the duty control signal by multiplying a value of the duty information by the value of the conduction-period information.
13. A method of controlling a power factor correction (PFC) circuit, the method comprising:
generating a conduction detection signal in response to a zero-current detection signal, the conduction detection signal indicating a zero-current duration of an inductor current;
decreasing a value of the conduction-period information a value of the conduction detection signal increases when the PFC circuit operates in a first mode and keeping the value of the conduction-period information substantially constant when the PFC circuit operates in a second mode, the conduction-period information being associated with a conduction period in which the inductor current flows through a power switch; and
generating a duty control signal in response to the conduction-period information.
14. The method of claim 13 , wherein the first mode is a discrete conduction mode (DCM) and the second mode is a continuous conduction mode (CCM), and the inductor current keeps having a magnitude greater than zero during an entire switching cycle of the power switch when the PFC circuit operates in the CCM.
15. The method of claim 13 , further comprising:
calculating the conduction-period information by subtracting the value of the conduction detection voltage from a predetermined reference value.
16. The method of claim 13 , further comprising sampling a reference signal synchronized with a switching frequency of the power switch at a detected zero-cross time and holding a sampled reference signal to generate the conduction detection voltage.
17. The method of claim 13 , further comprising decreasing a value of the duty control signal by decreasing the value of the conduction-period information as the zero-current duration of the inductor current increases when the PFC circuit operates in the first mode.
18. The method of claim 16 , wherein the reference signal has a sawtooth waveform that increases with a predetermined slope in a switching cycle of the power switch.
19. A power converter comprising:
an inductor having a first end to which an input voltage is applied and a second end;
a power switch coupled between the second end of the inductor and a ground, the power switch being configured to control an output of the power converter; and
a power factor correction (PFC) controller configured to generate a conduction detection signal in response to a zero-current detection signal, the conduction detection signal indicating a zero-current duration of an inductor current, to generate conduction-period information in response to the conduction detection signal, the conduction-period information being associated with a conduction period in which the inductor current flows through a power switch, and to generate a duty control signal in response to the conduction-period information,
wherein a value of the conduction-period information decreases as a value of the conduction detection signal increases when the power converter operates in a first mode and is substantially constant when the power converter operates in a second mode.
20. The power converter of claim 19 , wherein, when the power converter operates in the first mode, the PFC controller decreases a value of the duty control signal by decreasing the value of the conduction-period information as the zero-current duration of the inductor current increases.