Holdup time circuit and method for bridgeless PFC converter

1. A circuit comprising:

a charge device connected between an output terminal of a bridgeless power factor correction circuit and an energy storage apparatus; and

a discharge device connected between the energy storage apparatus and an input of the bridgeless power factor correction circuit, wherein the discharge device comprises a switching element, and wherein:

the bridgeless power factor correction circuit comprises a first boost converter, a second boost converter and an output of the first boost converter is connected to an output of the second boost converter.

2. The circuit of claim 1 , wherein:

the charge device is an n-type metal oxide semiconductor transistor.

3. The circuit of claim 1 , wherein:

the charge device is a diode.

4. The circuit of claim 1 , wherein:

the charge device is a resistor and a diode connected in parallel.

5. The circuit of claim 1 , wherein:

the discharge device is an n-type metal oxide semiconductor transistor.

6. The circuit of claim 1 , further comprising:

a surge protection diode, wherein the discharge device and the surge protection diode are in one single device.

7. The circuit of claim 1 , wherein:

the discharge device is formed by two n-type metal oxide semiconductor transistors.

8. The circuit of claim 7 , wherein:

a first transistor of the discharge device is connected to an input terminal of the first boost converter; and

a second transistor of the discharge device is connected to an input terminal of the second boost converter.

9. The circuit of claim 8 , wherein:

a body diode of the first transistor is configured to operate as a surge protection diode for the first boost converter; and

a body diode of the second transistor is configured to operate as a surge protection diode for the second boost converter.

10. A system comprising:

a bridgeless power factor correction circuit comprising a first boost converter coupled between a first terminal of an input ac source and an output, a second boost converter coupled between a second terminal of the input ac source and the output, a first switch coupled between an input of the first boost converter and ground and a second switch coupled between an input of the second boost converter and ground;

a plurality of surge protection diodes connected between the input ac source and the output;

a charge device connected between an output terminal of the bridgeless power factor correction circuit and an energy storage apparatus; and

a discharge device connected between the energy storage apparatus and an input of the bridgeless power factor correction circuit.

11. The system of claim 10 , wherein the plurality of surge protection diodes comprises:

a first surge protection diode coupled between the input of the first boost converter and the output; and

a second surge protection diode coupled between the input of the second boost converter and the output.

12. The system of claim 10 , wherein:

the charge device is a diode coupled between a first inductor of the first boost converter and the energy storage apparatus; and

the discharge device is a switching element coupled between the energy storage apparatus and the input of the second boost converter.

13. The system of claim 10 , wherein:

the charge device is a diode coupled between a second inductor of the second boost converter and the energy storage apparatus; and

the discharge device is a switching element coupled between the energy storage apparatus and the input of the first boost converter.

14. The system of claim 10 , wherein:

the charge device is a first switching element coupled between the output terminal of the bridgeless power factor correction circuit and the energy storage apparatus; and

the discharge device is a second switching element coupled between the energy storage apparatus and the input of the bridgeless power factor correction circuit.

15. The system of claim 10 , wherein:

the charge device is a first switching element coupled between the output terminal of the bridgeless power factor correction circuit and the energy storage apparatus; and

the discharge device is formed by a second switching element and a third switching element connected to the first terminal and the second terminal of the input ac source, respectively.

16. A method comprising:

charging an energy storage apparatus through a charge device, wherein the charge device is connected between an output of a bridgeless power factor correction circuit and the energy storage apparatus; and

discharging the energy storage apparatus through a discharge device, wherein the discharge device is connected between the energy storage apparatus and an input of the bridgeless power factor correction circuit, wherein the discharge device comprises a switching element.

17. The method of claim 16 , further comprising:

detecting a first half cycle of an input ac source connected to the bridgeless power factor correction circuit comprising two boost converters;

activating a first boost converter and a second switch coupled between an input of a second boost converter and ground; and

charging the energy storage apparatus from the first boost converter through the charge device.

18. The method of claim 16 , further comprising:

detecting a second half cycle of an input ac source connected to the bridgeless power factor correction circuit comprising two boost converters;

activating a second boost converter and a first switch coupled between an input of a first boost converter and ground; and

charging the energy storage apparatus from the second boost converter through the charge device.

19. The method of claim 16 , further comprising:

detecting, by a controller, a dropout of an input ac source connected to the bridgeless power factor correction circuit; and

activating the discharge device in response to the dropout.

20. The method of claim 19 , wherein:

the controller is configured to control the charge device, the discharge device and the bridgeless power factor correction circuit.