Redundant DC input power supplies having back-feed protection

1. A control circuit coupled for controlling a back-feed protection circuit, the control circuit configured to:

sense a first input DC voltage supplied to a first input circuit of the back-feed protection circuit;

sense a second input DC voltage supplied to a second input circuit of the back-feed protection circuit;

enable one of the first input circuit and the second input circuit having the highest input DC voltage; and

disable the other one of the first input circuit and the second input circuit to substantially prevent current from back feeding to the first input circuit and/or the second input circuit.

2. The control circuit of claim 1 , wherein the first input circuit includes a positive rail, a reference rail and a set of switching devices coupled in series in the positive rail of the first input circuit, and

wherein the second input circuit includes a positive rail, a reference rail, and a set of switching devices coupled in series in the positive rail of the second input circuit.

3. The control circuit of claim 2 , wherein the set of switching devices of the first input circuit include at least two MOSFETs and at least one diode; and

wherein the set of switching devices of the second input circuit include at least two MOSFETs and at least one diode.

4. The control circuit of claim 2 , wherein the control circuit includes:

a first set of drivers coupled for controlling the set of switching devices of the first input circuit, and

a second set of drivers coupled for controlling the set of switching devices of the second input circuit, and

wherein the control circuit is configured to:

generate a signal for enabling the first set of drivers or the second set of drivers associated with the one of the first input circuit and the second input circuit having the highest input DC voltage, and

generate a signal for disabling the first set of drivers or the second set of drivers associated with the other one of the first input circuit and the second input circuit.

5. The control circuit of claim 4 , wherein the first set of drivers includes:

a driver configured to control one switching device of the set of switching devices of the first input circuit, and

another driver configured to control another switching device of the set of switching devices of the first input circuit.

6. The control circuit of claim 4 , wherein the control circuit is configured to:

disable the first set of drivers based on a drive signal provided by any one of the second set of drivers changing state; and

disable the second set of drivers based on a drive signal provided by any one of the first set of drivers changing state.

7. The control circuit of claim 4 , wherein the first input circuit includes another set of switching devices coupled in series in the reference rail of the first input circuit;

wherein the first set of drivers are coupled for controlling the other set of switching devices of the first input circuit;

wherein the second input circuit includes another set of switching devices coupled in series in the reference rail of the second input circuit, and

wherein the second set of drivers are coupled for controlling the other set of switching devices of the second input circuit.

8. A method for controlling a back-feed protection circuit, the method comprising:

receiving a first input DC voltage via a first input circuit of the back-feed protection circuit;

receiving a second input DC voltage via a second input circuit of the back-feed protection circuit; and

sensing the first input DC voltage and the second input DC voltage;

enabling the first input circuit in response to the first input circuit having the highest input DC voltage;

disabling the second input circuit in response to the first input circuit having the highest input DC voltage to substantially prevent current from back feeding to the first input circuit from the second input circuit;

enabling the second input circuit in response to the second input circuit having the highest input DC voltage; and

disabling the first input circuit in response to the second input circuit having the highest input DC voltage to substantially prevent current from back feeding to the second input circuit from the first input circuit.

9. The method of claim 8 , wherein:

the first input circuit comprises:

a positive rail;

a reference rail, wherein the positive and reference rails of the first input circuit define an input for receiving the first input DC voltage; and

a first set of switching devices coupled in series in the positive rail of the first input circuit; and

the second input circuit comprises:

a positive rail;

a reference rail, wherein the positive and reference rails of the second input circuit define an input for receiving the second input DC voltage; and

a first set of switching devices coupled in series in the positive rail of the second input circuit.

10. The method of claim 9 , wherein the first input circuit further comprises a second set of switching devices coupled in series in the reference rail of the first input circuit; and

wherein the second input circuit further comprises a second set of switching devices coupled in series in the reference rail of the second input circuit.

11. The method of claim 10 further comprising:

controlling, via one driver of a set of drivers, one switching device of the first set of switching devices of the first input circuit and one switching device of the second set of switching devices of the first input circuit; and

controlling, via another driver of the set of drivers, another switching device of the first set of switching devices of the first input circuit and another switching device of the second set of switching devices of the first input circuit.

12. The method of claim 11 further comprising generating a first set of drive signals; and

controlling the first set of switching devices of the first input circuit based on the first set of drive signals.

13. The method of claim 12 , further comprising:

generating a signal for enabling the one of the first input circuit and the second input circuit having the highest input DC voltage; and

generating a signal for disabling the other one of the first input circuit and the second input circuit having the lowest input DC voltage.

14. The method of claim 9 , wherein one of:

the first set of switching devices of the first input circuit includes at least two MOSFETs; and

the first set of switching devices of the second input circuit includes at least two MOSFETs.

15. The method of claim 14 , wherein one of:

the first set of switching devices of the first input circuit includes at least one diode; and

the first set of switching devices of the second input circuit includes at least one diode.

16. The method of claim 8 , wherein the second input circuit is coupled to the first input circuit.

17. A back-feed protection circuit comprising:

first and second input circuits, each input circuit including:

a positive rail; and

a set of MOSFETs coupled to the positive rail; and

a control circuit coupled to the first and second input circuits and configured to:

enable the first input circuit or the second input circuit by turning on the set of MOSFETs of the first input circuit or the second input circuit; and

disabling the other one of the first input circuit and the second input circuit to substantially prevent current from back feeding to the enabled first or second input circuit.

18. The back-feed protection circuit of claim 17 , wherein the first input circuit includes an input for receiving a first input DC voltage;

wherein the second input circuit includes an input for receiving a second input DC voltage; and

wherein the control circuit is configured to sense the first input DC voltage and the second input DC voltage and enable the one of the first input circuit and the second input circuit having the highest input DC voltage.

19. The back-feed protection circuit of claim 18 , wherein the control circuit is configured to generate a first set of drive signals and a second set of drive signals; and

wherein the control circuit includes:

a first set of drivers coupled for controlling the set of MOSFETs of the first input circuit based on the first set of drive signals; and

a second set of drivers coupled for controlling the set of MOSFETs of the second input circuit based on the second set of drive signals.

20. The back-feed protection circuit of claim 19 , wherein the first set of drivers includes:

a first driver configured to control one MOSFET of the first set of MOSFETs; and

a second driver configured to control another MOSFET of the first set of MOSFETs.