High efficiency multiple input voltage sources power supply

• US 6,522,190 B1
• Filed: 10/31/2001
• Issued: 02/18/2003
• Est. Priority Date: 10/31/2001
• Status: Active Grant

• Current Assignee: Lenovo International Limited (Lenovo Group Ltd.)
• Original Assignee: International Business Machines Corporation
• Inventors: Nguyen, Trung Minh, Malik, Randhir Singh, Hemena, William
• Primary Examiner(s): Callahan, Timothy P.
• Assistant Examiner(s): Luu, An T.
• Application Number:
  US09/999,103
• Time in Patent Office: 475 Days
• Field of Search: 327/530, 327/401, 327/407, 327/408, 327/63, 327/70, 307/64, 307/65, 307/125, 307/130
• US Class Current: 327/408
• CPC Class Codes: H02J 1/10 Parallel operation of dc sources
• CPC Class Codes: H02J 1/108 using diodes blocking reverse current flow H02J1/12 takes precedence
• CPC Class Codes: H02M 3/158 including plural semiconductor devices as final control devices for a single load
• CPC Class Codes: H03K 17/302 in field-effect transistor switches
• CPC Class Codes: H03K 17/693 Switching arrangements with several input- or output-terminals, e.g. multiplexers, distributors logic circuits H03K19/00; code converters H03M5/00, H03M7/00

Abstract

The present invention provides a highly efficient power supply with redundant multiple input voltage sources. The power supply uses switching transistors, specifically MOSFET'"'"'s, to create paths for current from one of the voltage sources to the load. The switching transistors are switched either “on” or “off” by comparators which compare the output from the voltage sources. These comparators allow the highest voltage source to provide power to the load, and keep the other switching transistors “off” that connect the common load to other voltage sources. Because the switching transistors have lower conduction losses than diodes in conventional power supplies, the power supply in accordance with the present invention is more efficient.

Claims

1. A power supply circuit including a first voltage source and a second voltage source, comprising:

a first circuit coupled to the first voltage source, wherein the first circuit comprises;

a first comparator for comparing a first voltage from the first voltage source with a second voltage from the second voltage source,

a first transistor coupled to the first comparator, wherein the first transistor conducts when the first voltage is higher than the second voltage, and

a second transistor coupled to the first transistor and the first voltage source, wherein the second transistor conducts when the first transistor conducts, wherein the first voltage is provided as an output voltage when the second transistor conducts; and

a second circuit coupled to the second voltage source, wherein the second circuit comprises;

a second comparator for comparing the second voltage with the first voltage,

a third transistor coupled to the second comparator, wherein the third transistor conducts when the second voltage is higher than the first voltage, and

a fourth transistor coupled to the third transistor and the second voltage source, wherein the fourth transistor conducts when the third transistor conducts, wherein the second voltage is provided as the output voltage when the fourth transistor conducts.

2. The circuit of claim 1, wherein the first circuit further comprises a means for sensing the first voltage, comprising:

a first resistor coupled to an input of the first voltage source and a non-inverting pin of the first comparator; and

a second resistor coupled to the first resistor and the non-inverting pin of the first comparator and to a return of the first voltage source.

3. The circuit of claim 1, wherein the second circuit further comprises a means for sensing the second voltage, comprising:

a first resistor coupled to an input of the second voltage source and a non-inverting pin of the second comparator; and

a second resistor coupled to the first resistor and the non-inverting pin of the second comparator and to a return of the second voltage source.

4. The circuit of claim 1, wherein the first comparator comprises:

a non-inverting pin coupled to a means for sensing the first voltage and to an inverting pin of the second comparator;

an inverting pin coupled to a means for sensing the second voltage and to a non-inverting pin of the second comparator; and

an output pin coupled to a gate of the first transistor.

5. The circuit of claim 1, wherein the second comparator comprises:

a non-inverting pin coupled to a means for sensing the second voltage and to an inverting pin of the first comparator;

an inverting pin coupled to a means for sensing the first voltage and to a non-inverting pin of the first comparator; and

an output pin coupled to a gate of the third transistor.

6. The circuit of claim 1, wherein the first transistor comprises:

a gate coupled to an output pin of the first comparator;

a source coupled to a return of the first voltage source; and

a drain coupled to a gate of the second transistor.

7. The circuit of claim 1, wherein the second transistor comprises:

a gate coupled to a drain of the first transistor;

a source coupled to a load; and

a drain coupled to an input of the first voltage source.

8. The circuit of claim 1, wherein the third transistor comprises:

a gate coupled to an output pin of the second comparator;

a source coupled to a return of the second voltage source; and

a drain coupled to a gate of the fourth transistor.

9. The circuit of claim 1, wherein the fourth transistor comprises:

a gate coupled to a drain of the third transistor;

a source coupled to a load; and

a drain coupled to an input of the second voltage source.

10. The circuit of claim 1, wherein the second transistor comprises a first internal diode, wherein an anode of the first internal diode is coupled to a source of the second transistor, and a cathode of the first internal diode is coupled to a drain of the second transistor.

11. The circuit of claim 1, wherein the fourth transistor comprises a second internal diode, wherein an anode of the second internal diode is coupled to a source of the fourth transistor, and a cathode of the second internal diode is coupled to a drain of the fourth transistor.

12. A power supply circuit including a first voltage source and a second voltage source, comprising:

a first circuit coupled to the first voltage source, wherein the first circuit comprises;

a first comparator for comparing a first voltage from the first voltage source with a second voltage from the second voltage source,

a first transistor coupled to the first comparator, wherein the first transistor conducts when the first voltage is higher than the second voltage, and

a second transistor coupled to the first transistor and the first voltage source, wherein the second transistor conducts when the first transistor conducts, wherein the first voltage is provided as an output voltage when the second transistor conducts,

wherein the second transistor comprises a first internal diode coupled to the second transistor, wherein the first internal diode prevents unwanted back flowing of current to the first voltage source; and

a second circuit coupled to the second voltage source, wherein the second circuit comprises;

a second comparator for comparing the second voltage with the first voltage,

a third transistor coupled to the second comparator, wherein the third transistor conducts when the absolute value of the second voltage is higher than the absolute value of the first voltage, and

a fourth transistor coupled to the third transistor and the second voltage source, wherein the fourth transistor conducts when the third transistor conducts, wherein the second voltage is provided as the output voltage when the fourth transistor conducts,

wherein the fourth transistor comprises a second internal diode coupled to the fourth transistor, wherein the second internal diode prevents unwanted back flowing of current to the second voltage source.

13. The circuit of claim 12, wherein the first circuit further comprises a means for sensing the first voltage, comprising:

a first resistor coupled to an input of the first voltage source and a non-inverting pin of the first comparator; and

a second resistor coupled to the first resistor and the non-inverting pin of the first comparator and to a return of the first voltage source.

14. The circuit of claim 12, wherein the second circuit further comprises a means for sensing the second voltage, comprising:

a first resistor coupled to an input of the second voltage source and a non-inverting pin of the second comparator; and

a second resistor coupled to the first resistor and the non-inverting pin of the second comparator and to a return of the second voltage source.

15. The circuit of claim 12, wherein the first comparator comprises:

a non-inverting pin coupled to a means for sensing the first voltage and to an inverting pin of the second comparator;

an inverting pin coupled to a means for sensing the second voltage and to a non-inverting pin of the second comparator; and

an output pin coupled to a gate of the first transistor.

16. The circuit of claim 12, wherein the second comparator comprises:

a non-inverting pin coupled to a means for sensing the second voltage and to an inverting pin of the first comparator;

an inverting pin coupled to a means for sensing the first voltage and to a non-inverting pin of the first comparator; and

an output pin coupled to a gate of the third transistor.

17. The circuit of claim 12, wherein the first transistor comprises:

a gate coupled to an output pin of the first comparator;

a source coupled to a return of the first voltage source; and

a drain coupled to a gate of the second transistor.

18. The circuit of claim 12, wherein the second transistor comprises:

a gate coupled to a drain of the first transistor;

the source coupled to a load; and

the drain coupled to an input of the first voltage source.

19. The circuit of claim 12, wherein the third transistor comprises:

a gate coupled to an output pin of the second comparator;

a source coupled to a return of the second voltage source; and

a drain coupled to a gate of the fourth transistor.

20. The circuit of claim 12, wherein the fourth transistor comprises:

a gate coupled to a drain of the third transistor;

the source coupled to a load; and

the drain coupled to an input of the second voltage source.

21. The circuit of claim 12, wherein an anode of the first internal diode is coupled to a source of the second transistor, and a cathode of the first internal diode is coupled to a drain of the second transistor.

22. The circuit of claim 12, wherein an anode of the second internal diode is coupled to a source of the fourth transistor, and a cathode of the second internal diode is coupled to a drain of the fourth transistor.

23. A power supply circuit, including a first voltage source with a first input and a first return for providing a first voltage, and a second voltage source with a second input and a second return for providing a second voltage, comprising:

a first circuit coupled to the first voltage source, wherein the first circuit comprises;

a first means for sensing the first voltage,

a first comparator comprising a first non-inverting pin, a first inverting pin, and a first output pin, wherein the first non-inverting pin is coupled to the first sensing means, wherein a third voltage is provided at the first output pin when the first voltage is higher than the second voltage,

a first transistor comprising a first gate, a first source, and a first drain, wherein the first gate is coupled to the first output pin, wherein the first source is coupled to the first return, and

a second transistor comprising a second gate, a second source, and a second drain, wherein the second gate is coupled to the first drain, wherein the second source is coupled to an output, wherein the second drain is coupled to the first input,

wherein the second transistor is coupled to a first internal diode comprising a first anode side and a first cathode side, wherein the first anode side is coupled to the second source and the first cathode side is coupled to the second drain; and

a second circuit coupled to the second voltage source, wherein the second circuit comprises;

a second means for sensing the second voltage,

a second comparator comprising a second non-inverting pin, a second inverting pin, and a second output pin, wherein the second non-inverting pin is coupled to the second sensing means and to the first inverting pin, wherein the second inverting pin is coupled to the first non-inverting pin, wherein a fourth voltage is provided at the second output pin when the second voltage is higher than the first voltage,

a third transistor comprising a third gate, a third emitter, and a third collector, wherein the third gate is coupled to the second output pin, wherein the third emitter is coupled to the second return, and

a fourth transistor comprising a fourth gate, a fourth source, and a fourth drain, wherein the fourth gate is coupled to the third drain, wherein the fourth source is coupled to the output, wherein the fourth drain is coupled to the second input,

wherein the fourth transistor comprises a second internal diode comprising a second anode side and a second cathode side, wherein the second anode side is coupled to the fourth source and the second cathode side is coupled to the fourth drain.