Power factor correction control circuit
View Patent ↗A bi-directional boost circuit for power factor correction includes a power factor control circuit and a pair of diodes, a pair of inductors, and a pair of switches. A first diode, a second diode, a first inductor, a second inductor, a first switch, and a second switch convert the AC input voltage, rectify the AC input voltage, and output an intermediate DC voltage. The power factor control circuit receives the AC input voltage and receives the intermediate DC voltage. The power factor control circuit regulates the DC output voltage. Based on the AC input voltage and the intermediate DC output voltage, the power factor control circuit controls an inductor current waveform by driving the first switch and the second switch to create a substantially sinusoidal current as seen by the power source that is in phase with the AC input voltage.
1. A power factor correction circuit, comprising:
a first primary winding and a second primary winding of an isolation transformer to receive an AC voltage and an AC current,
a first switch coupled to the first winding and a second switch coupled to the second winding to draw current through the first primary winding and the second primary winding when the first switch and the second switch are turned on;
a control circuit to drive the first switch and the second switch to generate a current waveform for the AC current in accordance with power factor correction requirements;
a first secondary winding and a second secondary winding of the isolation transformer to receive, from the first primary winding and the secondary primary winding, an induced AC voltage and an induced AC current when the first switch and the second switch are turned off; and
a rectification circuit on a secondary side of the isolation transformer to rectify the induced AC voltage and the induced AC current.
2. The power factor correction circuit of claim 1 , wherein the first primary winding and the second primary winding are physically separate from each other.
3. The power factor correction circuit of claim 2 , wherein a terminal of the first secondary winding and a terminal the second secondary winding are coupled to ground and this results in noise cancellation of the high-frequency common-mode noise generated by high-frequency switching of the first switch and the second switch.
4. The power factor correction circuit of claim 1 , wherein the control circuit is configured to turn on the first switch and the second switch simultaneously.
5. The power factor correction circuit of claim 1 , wherein during a positive cycle of the AC input, the first switch is turned on and off by the control circuit and the second switch is continuously turned on by the control circuit.
6. The power factor correction circuit of claim 1 , wherein the rectification circuit is a first rectification diode and a second rectification diode.
7. The power factor correction circuit of claim 1 , wherein the rectification circuit is a first field effect transistor (FET) and a second FET.
8. The power factor correction circuit of claim 1 , wherein the power factor control circuit during a positive cycle of the AC input creates a clipped current waveform for the AC current if the control circuit is configured with a clipping threshold value and a value of a current in the first primary winding is above the clipping threshold value.
9. The power factor correction circuit of claim 1 , wherein the power factor control circuit, during a negative cycle of the AC input, creates a clipped current waveform if the power factor control circuit is configured with a clipping threshold value and a value of the current in the second primary winding is above the clipping threshold value.
10. The circuit of claim 1 , wherein the isolation transformer includes utilization of planar magnetics.
11. The circuit of claim 1 , wherein the isolation transformer includes utilization of solid or stranded wire.
12. A method of providing isolation, power factor correction, and rectification, comprising:
receiving an AC voltage and an AC current at a first primary winding and a secondary winding of an isolation transformer;
generating a current waveform for the AC current in accordance with power factor correction requirements utilizing the first primary winding, the second primary winding, a first switch, a second switch, and a power factor control circuit;
generating a second intermediate voltage and an induced current on a secondary side of the isolation transformer when the first switch and the second switch are turned off by the power factor control circuit; and
rectifying the second intermediate voltage and the induced current to create a rectified intermediate voltage and a rectified secondary current.
13. The method of claim 12 , wherein the rectifying of the second intermediate voltage and the induced current occurs utilizing a pair of rectification diodes.
14. The method of claim 12 , wherein the rectifying of the second intermediate voltage and the induced current occurs utilizing a pair of field effect transistors.
15. The method of claim 12 , wherein the current waveform is clipped utilizing the control circuit if an inductor current has a larger value than a threshold value.
16. The method of claim 12 , further including generating high frequency common mode noise, which is capacitively coupled from the first primary winding to the first secondary winding and from the second primary winding to the second primary winding, and canceling the high frequency common mode noise on a secondary side of the isolation transformer because of the configuration of the first secondary winding and the second secondary winding.
17. The method of claim 12 , wherein the current waveform is substantially sinusoidal in shape.