DC UPS with auto-ranging backup voltage capability

1. A direct current (DC) uninterruptible power supply (UPS) having an auto-ranging backup voltage capability, comprising:

at least one input;

at least one rectifier connected to the at least one input;

a common node connected to the at least one rectifier;

at least one DC output connected to the common node, the at least one DC output adapted for connection to at least one electrical load; and

an auto-ranging battery backup circuit connected to the common node, comprising:

negative and positive terminals,

first and second diodes connected to the negative terminal,

a first string of batteries connected to the first diode,

a second string of batteries connected to the second diode,

a switch connected between the first string of batteries and the second string of batteries,

a third diode connected between the first string of batteries and the positive terminal, and

a fourth diode connected between the second string of batteries and the positive terminal, wherein the switch places the first and second strings of batteries in parallel when opened, and places the first and second strings of batteries in series when closed.

2. The DC UPS of claim 1 , wherein the at least one rectifier is a full wave rectifier.

3. The UPS of claim 1 , wherein the at least one rectifier is a half wave rectifier.

4. The UPS of claim 1 , further including at least one of a disconnect switch connected between the battery backup circuit and the common node.

5. The UPS of claim 4 , wherein the disconnect switch connected between the battery backup circuit and the common node is adapted for connection to a controller for actuating the switch upon a power loss.

6. The UPS of claim 1 , wherein the switch of the battery backup circuit is adapted for connection to a controller to adjust the battery backup voltage to one of either a lower or a higher voltage depending upon a state of the switch.

7. The UPS of claim 6 , wherein the switch is an N-channel metal oxide semiconductor field effect transistor (MOSFET).

8. The UPS of claim 1 , wherein the at least one input is a direct current (DC), alternating current (AC), or rectified alternating current (AC) input.

9. A method for configuring a direct current (DC) uninterruptible power supply (UPS) to have an auto-ranging backup voltage capability, comprising:

configuring at least one input;

connecting at least one rectifier to the at least one input;

connecting a common node to the at least one rectifier;

connecting at least one DC output to the common node, the at least one DC output adapted for connection to at least one electrical load; and

connecting an auto-ranging battery backup circuit to the common node, comprising:

configuring negative and positive terminals,

connecting first and second diodes to the negative terminal,

connecting a first string of batteries to the first diode,

connecting a second string of batteries to the second diode,

connecting a switch between the first string of batteries and the second string of batteries,

connecting a third diode between the first string of batteries and the positive terminal, and

connecting a fourth diode between the second string of batteries and the positive terminal, wherein the switch places the first and second strings of batteries in parallel when opened, and places the first and second strings of batteries in series when closed.

10. The method of claim 9 , wherein connecting a common node to the rectifier includes connecting a common node to one of a full wave rectifier and a half wave rectifier.

11. The method of claim 9 , further including connecting a disconnect switch between the battery backup circuit and the common node.

12. A direct current (DC) uninterruptible power supply (UPS) having auto-ranging battery backup voltage capability, comprising:

at least one input;

a rectifier connected to the at least one input;

a common node connected to the rectifier;

at least one output connected to the common node; and

a battery backup circuit connected to the common node, comprising:

first and second strings of batteries,

a switch connected between a positive terminal of the first string of batteries and a negative terminal of the second string of batteries, wherein the switch is operable to place the first and second strings of batteries in series when closed, and operable to place the first and second strings of batteries in parallel when open, and

a plurality of steering diodes connected to the first and second strings of batteries and the switch to maintain current flow in a first direction.

13. The DC UPS of claim 12 , wherein the switch is a power transistor or a relay device.

14. The DC UPS of claim 12 , wherein the switch is connected to a controller, the controller selectively operating the switch to provide a lower or higher backup voltage depending on a position of the switch.

15. The DC UPS of claim 12 , further including a disconnect switch between the battery backup circuit and the common node.

16. The DC UPS of claim 12 , wherein the rectifier is one of a full wave rectifier or a half wave rectifier.

17. The DC UPS of claim 12 , further including a circuit protection device connected between the battery backup circuit and the common node.

18. The DC UPS of claim 12 , wherein the at least one input is a direct current (DC), alternating current (AC), or rectified alternating current (AC) input.

19. A method of manufacturing a direct current (DC) uninterruptible power supply (UPS) having auto-ranging battery backup voltage capability, comprising:

providing at least one input;

providing a rectifier connected to the at least one input;

providing a common node connected to the rectifier;

providing at least one output connected to the common node; and

providing a battery backup circuit connected to the common node, comprising:

providing first and second strings of batteries,

providing a switch connected between a positive terminal of the first string of batteries and a negative terminal of the second string of batteries, wherein the switch is operable to place the first and second strings of batteries in series when closed, and operable to place the first and second strings of batteries in parallel when open, and

providing a plurality of steering diodes connected to the first and second strings of batteries and the switch to maintain current flow in a first direction.

20. The method of manufacture of claim 19 , wherein providing a switch connected between a positive terminal of the first string of batteries and a negative terminal of the second string of batteries includes providing a power transistor or a relay device connected between the positive terminal of the first string of batteries and the negative terminal of the second string of batteries.

21. The method of manufacture of claim 19 , further including providing a controller connected to the switch, the controller selectively operating the switch to provide a lower or higher backup voltage depending on a position of the switch.

22. The method of manufacture of claim 19 , further including providing a disconnect switch between the battery backup circuit and the common node.

23. The method of manufacture of claim 19 , wherein providing a rectifier includes providing at least one of a full wave rectifier or a half wave rectifier.

24. The method of manufacture of claim 19 , further including providing a circuit protection device connected between the battery backup circuit and the common node.

25. The method of manufacture of claim 19 , wherein providing at least one input includes providing a direct current (DC), alternating current (AC), or partially rectified alternating current (AC) input.