Surge tolerant power supply system for providing operating power to appliances

1. A surge-tolerant power supply system comprising:

an input circuit having a first input terminal and a second input terminal configured to receive a source of DC voltage;

an N-channel MOSFET having a gate terminal, a source terminal, and a drain terminal, the N-channel MOSFET having a characteristic threshold voltage between the gate terminal and the source terminal, and the drain terminal being electrically connected to a positive output of the input circuit;

a switch mode DC-to-DC converter having an input electrically connected to the source terminal of the N-channel MOSFET and a negative output of the input circuit;

a transformer driver having an input electrically connected to an output of the switch mode DC-to-DC converter;

an isolation transformer having a primary winding electrically connected to an output of the transformer driver;

a rectifier-filter circuit having an input electrically connected to a secondary winding of the isolation transformer and having an output configured to provide an output voltage;

a bias circuit having a first input electrically connected to the positive output of the input circuit and a second input electrically connected to the negative output of the input circuit; and

a DC bias boost circuit having a first input electrically connected to an auxiliary winding of the isolation transformer, a second input electrically connected to an output of the bias circuit, and an output electrically connected to the gate terminal of the N-channel MOSFET,

wherein the DC bias boost circuit is configured to apply a voltage at the gate terminal of the N-channel MOSFET that exceeds the characteristic threshold voltage between the gate terminal and the source terminal of the N-channel MOSFET.

2. The surge-tolerant power supply system of claim 1 , wherein the bias circuit is configured to provide a voltage ramp at the output of the bias circuit during a start-up period.

3. The surge-tolerant power supply system of claim 1 , wherein the input circuit comprises a transient voltage suppressor having a first terminal electrically connected to the first input terminal of the input circuit and a second terminal electrically connected to the second input terminal of the input circuit.

4. The surge-tolerant power supply system of claim 1 , wherein the input circuit comprises a polarity protection circuit having a first terminal electrically connected to the first input terminal of the input circuit and a second terminal electrically connected to the positive output of the input circuit.

5. The surge-tolerant power supply system of claim 1 , wherein the transformer driver is configured to delay an output signal of the transformer driver for a predetermined time during a start-up period.

6. The surge-tolerant power supply system of claim 1 , wherein the transformer driver is configured to shut down an output signal of the transformer driver when a voltage level at the positive output of the input circuit is above a predetermined level.

7. The surge-tolerant power supply system of claim 1 , wherein the transformer driver is configured to shut down an output signal of the transformer driver when a voltage level at the positive output of the input circuit is above a predetermined level.

8. A surge-tolerant power supply comprising:

an input circuit configured to receive a source of DC voltage;

a pass device having a first terminal electrically connected to a positive output of the input circuit;

a voltage converter circuit having an input and at least two isolated outputs, the input being electrically connected to a second terminal of the pass device, and a first isolated output of the at least two isolated outputs is configured to provide an output voltage;

a bias circuit having a first input electrically connected to a second output of the at least two isolated outputs of the voltage converter circuit, a second input electrically connected to the positive output of the input circuit, and an output electrically connected to a control terminal of the pass device, wherein the bias circuit is configured to apply a voltage on the control terminal of the pass device sufficient to put the pass device into a low impedance state between the first terminal and the second terminal of the pass device;

wherein the voltage converter circuit includes a switch mode DC-to-DC converter having, as an input, the input of the voltage converter circuit, a transformer driver having an input electrically connected to an output of the switch mode DC-to-DC converter, an isolation transformer having a primary winding electrically connected to an output of the transformer driver, and a rectifier-filter circuit having an input electrically connected to a secondary winding of the isolation transformer and having an output configured to provide the output voltage; and

wherein the transformer driver is configured to shut down an output signal of the transformer driver when a voltage level at the positive output of the input circuit is above a predetermined level.

9. The surge-tolerant power supply of claim 8 , wherein the bias circuit is configured to provide a voltage ramp at the output of the bias circuit during a start-up period.

10. The surge-tolerant power supply of claim 8 , wherein the input circuit comprises a transient voltage suppressor having a first terminal electrically connected to a first input terminal of the input circuit and a second terminal electrically connected to a second input terminal of the input circuit.

11. The surge-tolerant power supply of claim 8 , wherein the input circuit comprises a polarity protection circuit having a first terminal electrically connected to the first input terminal of the input circuit and a second terminal electrically connected to the positive output of the input circuit.

12. The surge-tolerant power supply of claim 8 , wherein the transformer driver is configured to delay an output signal of the transformer driver for a predetermined time during a start-up period.

13. The surge-tolerant power supply of claim 12 , wherein the transformer driver is configured to shut down an output signal of the transformer driver when the voltage level at the positive output of the input circuit is above a predetermined level.

14. A surge-tolerant power supply comprising:

an input circuit configured to receive a source of DC voltage;

a pass device having a first terminal electrically connected to an output of the input circuit;

a voltage converter circuit having an input and at least one output, the input being electrically connected to a second terminal of the pass device; and

a bias circuit having a first input electrically connected to a first of the least one output of the voltage converter circuit, a second input electrically connected to the output of the input circuit, and an output electrically connected to a control terminal of the pass device, wherein the bias circuit is configured to apply, after a predetermined start-up period, a voltage on the control terminal of the pass device sufficient to put the pass device into a low impedance state between the first terminal and the second terminal of the pass device;

wherein the bias circuit is further configured to provide a voltage ramp on the control terminal of the pass device during the predetermined start-up period.

15. The surge-tolerant power supply of claim 14 , wherein the voltage converter circuit has a second output configured to provide an output voltage.

16. The surge-tolerant power supply of claim 14 , wherein the input circuit comprises a transient voltage suppressor having a first terminal electrically connected to a first input terminal of the input circuit and a second terminal electrically connected to a second input terminal of the input circuit.

17. The surge-tolerant power supply of claim 14 , wherein the voltage converter circuit includes a switch mode DC-to-DC converter having, as an input, the input of the voltage converter circuit, a transformer driver having an input electrically connected to an output of the switch mode DC-to-DC converter, and an isolation transformer having a primary winding electrically connected to an output of the transformer driver.

18. The surge-tolerant power supply of claim 14 , wherein the input circuit comprises a polarity protection circuit having a first terminal electrically connected to a first input terminal of the input circuit and a second terminal electrically connected to the output of the input circuit.

19. The surge-tolerant power supply of claim 17 , wherein the transformer driver is configured to shut down an output signal of the transformer driver when a voltage level at the output of the input circuit is above a predetermined level.

20. The surge-tolerant power supply of claim 17 , wherein the transformer driver is configured to delay an output signal of the transformer driver for a predetermined time.