Power supply apparatus

1. A power supply apparatus comprising:

a first power supply unit including a transformer switching and transforming an input power, and converting the input power into a first power and providing the first power to a main output terminal and a standby output terminal;

a second power supply unit converting the input power into a second power and providing power only to the first power supply unit as an operating power of the first power supply unit; and

a main switching unit intermitting a supply of the first power from the first power supply unit to the main output terminal.

2. The power supply apparatus of claim 1 , wherein the main switching unit includes a bidirectional switching device.

3. The power supply apparatus of claim 2 , wherein the main switching unit is switched off in a standby mode and is switched on in a nominal mode.

4. The power supply apparatus of claim 1 , wherein the main switching unit includes first and second switches each having a reverse diode embedded therein, and

a source of the first switch is connected to a source of the second switch, and a gate of the first switch is connected to a gate of the second switch.

5. The power supply apparatus of claim 1 , wherein the second power supply unit includes at least one of a flyback converter and a buck converter.

6. The power supply apparatus of claim 1 , wherein the first power supply unit includes:

a primary side circuit unit including a primary side winding of the transformer and a plurality of primary side switching devices controlling a current flowing to the primary side winding of the transformer; and

a secondary side circuit unit.

7. The power supply apparatus of claim 6 , wherein the primary side switching devices include first and second switching devices connected to each other in series and third and fourth switching devices connected to each other in series,

both ends of the first and second switching devices connected to each other in series are connected to a power input terminal in parallel, and both ends of the third and fourth switching devices connected to each other in series are connected in parallel with the power input terminal, and

the primary side winding of the transformer is connected between a first node, a connection point between the first and second switching devices, and a second node, a connection point between the third and fourth switching devices.

8. The power supply apparatus of claim 7 , wherein the second power supply unit includes:

an inductor device having one end connected to the first node; and

a capacitor device connected between the other end of the inductor device and a ground.

9. The power supply apparatus of claim 8 , wherein the second power supply unit further includes a buck converter.

10. The power supply apparatus of claim 7 , wherein the second power supply unit further includes:

an inductor device having one end connected to the first node;

a switching device connected between the other end of the inductor device and a ground; and

a diode device connected to the other end of the inductor device.

11. A power supply apparatus comprising:

a first power supply unit including a transformer switching and transforming an input power, and converting the input power into a first power and providing the first power to a main output terminal and a standby output terminal;

a second power supply unit converting the input power into a second power and providing power only to the first power supply unit as an operating power of the first power supply unit; and

a bidirectional switching device formed between an output terminal of the first power supply unit and the main output terminal and intermitting a supply of the first power from the first power supply unit to the main output terminal.