Power circuit and liquid crystal display using same

1. A power circuit comprising:

a first rectifying and filtering circuit configured to receive an alternating current (AC) voltage and transform the AC voltage to a first DC voltage, the first rectifying and filtering circuit comprising a first output configured to output the first DC voltage and a first filter capacitor directly connected between the first output and ground;

a power factor correction (PFC) circuit comprising a first transformer, a first diode, a second diode with a grounded positive terminal and a first storage capacitor, the first transformer comprising a primary winding and a secondary winding;

an inverter circuit comprising a transistor and a second transformer, the second transformer comprising a primary winding and a secondary winding, the primary winding of the second transformer being grounded via the transistor and configured to receive the first DC voltage via the primary winding of the first transformer, the first diode, and the secondary winding of the first transformer in series when the transistor is switched on; and

a second rectifying and filtering circuit connected to the secondary winding of the second transformer for providing a second DC voltage to a load circuit;

wherein the first filter capacitor is charged via a current path formed by the primary winding of the first transformer, the second diode, and the first filter capacitor when the transistor is switched off.

2. A power circuit comprising:

a first rectifying and filtering circuit configured to receive an alternating current (AC) voltage and transform the AC voltage to a first DC voltage, the first rectifying and filtering circuit comprising a first output configured to output the first DC voltage and a first filter capacitor connected between the first output and ground;

a power factor correction (PFC) circuit comprising a first transformer, a first diode, a second diode and a first storage capacitor, the first transformer comprising a primary winding and a secondary winding;

an inverter circuit comprising a transistor and a second transformer, the second transformer comprising a primary winding and a secondary winding, the primary winding of the second transformer being grounded via the transistor and configured to receive the first DC voltage via the primary winding of the first transformer, the first diode, and the secondary winding of the first transformer in series when the transistor is switched on; and

a second rectifying and filtering circuit connected to the secondary winding of the second transformer for providing a second DC voltage to a load circuit,

wherein the first filter capacitor is charged via a current path formed by the primary winding of the first transformer, the second diode, and the first filter capacitor when the transistor is switched off;

wherein the primary winding of the first transformer comprises a first terminal and a second terminal, wherein the first terminal of the first transformer is connected to the first output, the second terminal of the primary winding of the first transformer is connected to a positive terminal of the first diode and a negative terminal of the second diode, a positive terminal of the second diode is grounded, a negative terminal of the first diode is grounded via the secondary winding of the first transformer, the primary winding of the second transformer, and the transistor in series.

3. The power circuit of claim 2 , the inverter circuit further comprises a pulse width modulation (PWM) chip configured to switch on or switch off the transistor.

4. The power circuit of claim 3 , wherein the PWM chip comprises a pulse output connected to a gate electrode of the transistor.

5. The power circuit of claim 3 , wherein the inverter circuit further comprises a protection circuit connected in parallel with the primary winding of the second transformer.

6. The power circuit of claim 2 , wherein the second rectifying and filtering circuit comprises an inductor, a third diode, a second storage capacitor, and a voltage output, wherein the secondary winding of the second transformer comprises a first terminal and a second terminal, the first terminal of the secondary winding of the second transformer is connected to a negative terminal of the third diode, the second terminal of the secondary winding of the second transformer is connected to ground via the second storage capacitor, and is connected to the voltage output via the inductor, a positive terminal of the third diode is grounded.

7. The power circuit of claim 6 , wherein second rectifying and filtering circuit further comprises a second filter capacitor connected between the voltage output and ground.

8. The power circuit of claim 2 , wherein transistor is an n-channel metal-oxide-semiconductor field-effect transistor.

9. A liquid crystal display (LCD) comprising an LCD panel and a power circuit, the power circuit comprising a power supply for providing an alternating current (AC) voltage and a first rectifying and filtering circuit for providing a first DC voltage, a PFC circuit, an inverter circuit, and a second rectifying and filtering circuit, the PFC circuit comprising a first transformer, the inverter circuit comprising a second transformer and a transistor, wherein the PFC circuit realizes a power factor correction of the first DC voltage according to the operation of the transistor and the PFC circuit, wherein a primary winding of the first transformer comprises a first terminal and a second terminal, wherein the first terminal of the primary winding of the first transformer is configured to receiving the first DC voltage, the second terminal of the primary winding of the first transformer is connected to a positive terminal of a first diode and a negative terminal of a second diode, a positive terminal of the second diode is grounded, a negative terminal of the first diode is grounded via a secondary winding of the first transformer, the primary winding of the second transformer, and the transistor in series.

10. The LCD of claim 9 , the inverter circuit further comprises a pulse width modulation (PWM) chip configured to switch on and switch off the transistor.

11. The LCD of claim 10 , wherein the PWM chip comprises a pulse output connected to a gate electrode of the transistor.

12. The LCD of claim 11 , wherein the inverter circuit further comprises a protection circuit connected in parallel with the primary winding of the second transformer.

13. The LCD of claim 9 , wherein the second rectifying and filtering circuit comprises an inductor, a third diode, a second storage capacitor, and a voltage output, wherein a secondary winding of the second transformer comprises a first terminal and a second terminal, the first terminal of the secondary winding of the second transformer is connected to a negative terminal of the third diode, the second terminal of the secondary winding of the second transformer is connected to ground via the second storage capacitor, and is connected to the voltage output via the inductor, a positive terminal of the third diode is grounded.

14. The LCD of claim 9 , wherein a negative terminal of the first diode is grounded via the first storage capacitor.

15. The LCD of claim 1 , wherein a negative terminal of the first diode is grounded via the first storage capacitor.