Method and device for detecting current of inductor of PFC circuit

1. A method for detecting inductor current of a power factor correction (PFC) circuit, comprising:

detecting a voltage on a boost inductor of a critical-conduction mode PFC circuit, and obtaining an inductor voltage detection signal;

converting the inductor voltage detection signal into a voltage signal of which a waveform is consistent with a current waveform of the inductor to serve as an inductor current detection signal, to perform loop protection on the PFC circuit or perform over-current protection on the PFC circuit by using the inductor current detection signal;

wherein, the step of detecting a voltage on a boost inductor of a critical-conduction mode PFC circuit, and obtaining an inductor voltage detection signal comprises:

enwinding two inductor auxiliary windings on a magnetic core of the boost inductor of the PFC circuit for respectively detecting corresponding inductor voltages when an input alternating voltage is in positive and negative half cycles, and obtaining induced voltages in conformity with the current of the boost inductor of the PFC circuit on the inductor auxiliary windings; and

taking the obtained induced voltages as the inductor voltage detection signal;

wherein an end of a first inductor auxiliary winding of the PFC circuit is connected with a resistor R 1 , an end of a second inductor auxiliary winding of the PFC circuit is connected with a resistor R 2 , the other end of the resistor R 1 is connected with a collector of a switch triode VT 1 and the other end of the resistor R 2 is connected with a collector of a switch triode VT 2 , emitters of the switch triodes VT 1 and VT 2 are earthed, a capacitor C 1 is connected in parallel with the collector and emitter of the switch triode VT 1 and a capacitor C 2 is connected in parallel with the collector and emitter of the switch triode VT 2 , the collector of the switch triode VT 1 is connected with an anode of a diode D 1 and the collector of the switch triode VT 2 is connected with an anode of a diode D 2 , cathodes of the D 1 and D 2 are joined together and connected with an Analog-to-Digital Converter (ADC) sampling port of a Digital Signal Processor (DSP).

2. The method according to claim 1 , wherein, said obtaining induced voltages in conformity with the current of the boost inductor of the PFC circuit on the inductor auxiliary windings comprises:

through electromagnetic coupling, obtaining a positive voltage corresponding to a rising waveform of the current of the boost inductor of the PFC circuit and a negative voltage corresponding to a falling waveform of the current of the boost inductor of the PFC circuit on the two inductor auxiliary windings respectively.

3. The method according to claim 2 , wherein, the step of converting the inductor voltage detection signal into a voltage signal of which a waveform is consistent with a current waveform of the inductor to serve as an inductor current detection signal comprises:

performing integral processing on the inductor voltage detection signal, and taking the inductor voltage detection signal on which the integral processing is performed as the inductor current detection signal, wherein a waveform of the inductor current detection signal is consistent with a waveform of a current signal of the boost inductor of the PFC circuit.

4. The method according to claim 3 , wherein, the step of performing integral processing on the inductor voltage detection signal comprises:

performing integral processing on the positive voltage and the negative voltage obtained on the two inductor auxiliary windings respectively, and switching on or switching off a corresponding switch tube to charge or discharge a capacitor in a connected integral circuit;

detecting a voltage across two ends of the capacitor in the integral circuit, and obtaining the inductor current detection signal in conformity with the inductor current waveform after the integral processing.

5. The method according to claim 1 , wherein, said obtaining induced voltages in conformity with the current of the boost inductor of the PFC circuit on the inductor auxiliary windings comprises:

through electromagnetic coupling, obtaining a positive pulse corresponding to a sawtooth wave rising edge of the current of the boost inductor of the PFC circuit and a negative pulse corresponding to a sawtooth wave falling edge of the current of the boost inductor of the PFC circuit on the two inductor auxiliary windings respectively.

6. The method according to claim 5 , wherein, the step of converting the inductor voltage detection signal into a voltage signal whose waveform is consistent with a current waveform of the inductor to serve as an inductor current detection signal comprises:

performing integral processing on the inductor voltage detection signal, and taking the inductor voltage detection signal on which the integral processing is performed as the inductor current detection signal, wherein a waveform of the inductor current detection signal is consistent with a waveform of a current signal of the boost inductor of the PFC circuit.

7. The method according to claim 6 , wherein, the step of performing integral processing on the inductor voltage detection signal comprises:

by performing integral processing on the positive pulse and the negative pulse obtained on the two inductor auxiliary windings respectively, driving to switch on or switch off a corresponding switch tube to charge or discharge a capacitor in a connected integral circuit;

detecting a voltage across two ends of the capacitor in the integral circuit, and obtaining the inductor current detection signal in conformity with the inductor current waveform after the integral processing.

8. A device for detecting inductor current of a power factor correction (PFC) circuit, comprising:

a detection circuitry, configured to detect a voltage on a boost inductor of a critical-conduction mode PFC circuit, and obtain an inductor voltage detection signal, wherein two inductor auxiliary windings are enwound on a magnetic core of the boost inductor of the PFC circuit for respectively detecting corresponding inductor voltages when an input alternating voltage is in positive and negative half cycles, and induced voltages in conformity with the current of the boost inductor of the PFC circuit on the inductor auxiliary windings are obtained and taken as the inductor voltage detection signal; and

a conversion circuitry, configured to convert the inductor voltage detection signal into a voltage signal of which a waveform is consistent with a current waveform of the inductor to serve as an inductor current detection signal, to perform loop protection on the PFC circuit or perform over-current protection on the PFC circuit by using the inductor current detection signal;

wherein an end of a first inductor auxiliary winding of the PFC circuit is connected with a resistor R 1 , an end of a second inductor auxiliary winding of the PFC circuit is connected with a resistor R 2 , the other end of the resistor R 1 is connected with a collector of a switch triode VT 1 and the other end of the resistor R 2 is connected with a collector of a switch triode VT 2 , emitters of the switch triodes VT 1 and VT 2 are earthed, a capacitor C 1 is connected in parallel with the collector and emitter of the switch triode VT 1 and a capacitor C 2 is connected in parallel with the collector and emitter of the switch triode VT 2 , the collector of the switch triode VT 1 is connected with an anode of a diode D 1 and the collector of the switch triode VT 2 is connected with an anode of a diode D 2 , cathodes of the D 1 and D 2 are joined together and connected with an Analog-to-Digital Converter (ADC) sampling port of a Digital Signal Processor (DSP).

9. The device according to claim 8 , wherein, the conversion circuitry comprises:

an integral circuitry, configured to perform integral processing on the inductor voltage detection signal, and take the inductor voltage detection signal on which the integral processing is performed as the inductor current detection signal, wherein a waveform of the inductor current detection signal is consistent with a waveform of a current signal of the boost inductor of the PFC circuit.