Power factor correction efficiency improvement circuit, a converter employing the circuit and a method of manufacturing a converter

1. A power factor correcting circuit having a positive input terminal, an output terminal and a ground terminal, comprising:

a power factor inductor coupled in series between said positive input terminal and said output terminal, said power factor inductor comprising an output side coupled to a first node;

a main switch configured to periodically connect said power factor inductor to said ground terminal;

a snubber circuit coupled to said main switch, said snubber circuit comprising:

a choke inductor and an auxiliary switch coupled in series across said main switch, said choke inductor and said auxiliary switch configured to provide zero voltage switching for said main switch;

a clamping capacitor coupled to said power factor inductor at said first node, said clamping capacitor configured to provide zero turn-off loss for said main switch;

a conducting diode coupled to said choke inductor and said auxiliary switch at a second node;

a discharge diode coupled to said clamping capacitor and said conducting diode at a third node; and

an output diode connected in series between said power factor inductor and said output terminal, wherein said output diode is connected to said power factor inductor and said output diode at said first node.

2. The power factor correcting circuit as recited in claim 1 wherein said choke inductor said auxiliary switch are configured to discharge an internal capacitance of said main switch prior to activating said main switch.

3. The power factor correcting circuit as recited in claim 1 wherein said clamping capacitor is connected to said power factor inductor, said choke inductor and said main switch at said first node.

4. The power factor correcting circuit as recited in claim 3 wherein said conducting diode is configured to conduct current through said choke inductor when said auxiliary switch is off.

5. The power factor correcting circuit as recited in claim 4 wherein said discharge diode is configured to allow said choke inductor to discharge energy to an output capacitor coupled to said output terminal.

6. A method of manufacturing a power factor correcting circuit for a power converter, comprising:

connecting a power factor inductor to an output diode at a first node;

coupling a main power switch at said first node, said main power switch configured to periodically connect said power factor inductor to a ground terminal;

coupling a snubber circuit to said main switch, wherein coupling the snubber circuit to said main switch comprises:

coupling a choke inductor and an auxiliary switch in series across said main switch, said choke inductor and said auxiliary switch configured to provide zero voltage switching for said main switch;

connecting a clamping capacitor to said power factor inductor and said output diode at said first node, said clamping capacitor configured to provide zero turn-off loss for said main switch;

coupling a conducting diode coupled to said choke inductor and said auxiliary switch at a second node; and

coupling a discharge diode coupled to said clamping capacitor and said conducting diode at a third node.

7. The method as recited in claim 6 further comprising connecting said discharging diode and said output diode to an output capacitor at an output terminal of said converter.

8. The method as recited in claim 7 further comprising connecting unconnected sides of the main power switch, the auxiliary switch and the output capacitor to a ground terminal of the converter.

9. The method as recited in claim 8 further comprising connecting said power factor inductor of said PFC circuit to a power source.

10. The method as recited in claim 9 further comprising connecting a dc to dc converter to said output capacitor.

11. A power supply having a positive input terminal, an output terminal and a ground terminal, comprising:

a power source configured to receive AC power and generate DC power therefrom; and

a power factor correcting circuit configured to receive and condition said DC power, said power factor correcting circuit including:

a power factor inductor coupled to said power source at said positive input terminal and coupled in series between said positive input terminal and said output terminal, said power factor inductor comprising an output side coupled at a first node;

a main switch configured to periodically connect said power factor inductor to said ground terminal;

a snubber circuit coupled to said main switch, said snubber circuit comprising:

a choke inductor and an auxiliary switch coupled in series across said main switch, said choke inductor and said auxiliary switch configured to provide zero voltage switching for said main switch;

a clamping capacitor coupled to said power factor inductor at said first node, said clamping capacitor configured to provide zero turn-off loss for said main switch;

a conducting diode coupled to said choke inductor and said auxiliary switch at a second node;

a discharge diode coupled to said clamping capacitor and said conducting diode at a third node; and

an output diode connected in series between said power factor inductor and said output terminal, wherein said output diode is connected to said power factor inductor and said output diode at said first node.

12. The power supply as recited in claim 11 wherein said choke inductor said auxiliary switch are configured to discharge an internal capacitance of said main switch prior to activating said main switch.

13. The power supply as recited in claim 11 wherein said power factor correcting circuit is a first power factor correcting circuit and said power supply further comprises a second power factor correcting circuit coupled to said first power factor correcting circuit.

14. The power supply as recited in claim 13 wherein said first and said second power factor correcting circuits are coupled to said power factor inductor.

15. The power supply as recited in claim 14 wherein said first and said second power factor correcting circuits include zero voltage switching and zero turn-off snubber circuits.