Power supply with programmable voltage slew rate and method

• US 6,025,704 A
• Filed: 04/23/1998
• Issued: 02/15/2000
• Est. Priority Date: 04/23/1998
• Status: Expired due to Fees

• Current Assignee: Illinois Tool Works Inc.
• Original Assignee: Trilectron Industries, Inc. (Illinois Tool Works Inc.)
• Inventors: Elliott, Stephen H.
• Primary Examiner(s): HAN, YOUNGHUIE JESSICA
• Application Number:
  US09/065,130
• Time in Patent Office: 663 Days
• Field of Search: 323/274, 323/276, 323/277, 323/280, 323/281, 323/901, 323/908, 363/49, 361/56, 361/79
• US Class Current: 323/280
• CPC Class Codes: G05F 1/569 for protection
• CPC Class Codes: Y10S 323/901 Starting circuits
• CPC Class Codes: Y10S 323/908 Inrush current limiters

Abstract

A power supply with a programmable voltage slew rate is disclosed for generating a regulated voltage at a predetermined set-point. The power supply includes a programmable current source for generating a controllable level of current flow and a capacitive element coupled to the current source. The capacitive element is responsive to the current flow to establish a reference voltage that varies linearly with respect to variations in the current flow. The power supply additionally includes a power device having a control element disposed in sensed communication with the reference voltage and an output for driving a load. The output is operative to generate an output voltage following that of the reference voltage.

Claims

1. A power supply with a programmable voltage slew rate for generating a regulated voltage at a predetermined set-point, said power supply including:

a programmable current source for generating a controllable level of current flow;

a capacitive element coupled to said current source and responsive to said current flow to establish a reference voltage, said reference voltage varying linearly with respect to variations in said current flow; and

a power device having a control element electrically connected to said reference voltage and an output for driving a load, said output operative to generate an output voltage following that of said reference voltage.

2. A power supply according to claim 1 wherein said programmable current source comprises:

an operational amplifier disposed in a bi-polar current source for grounded load configuration.

3. A power supply according to claim 1 and further including:

a feedback circuit for detecting said output voltage and controlling said current source based on said output voltage level.

4. A power supply according to claim 3 wherein said feedback circuit includes:

an error amplifier having a first input connected to said voltage output and a second input coupled to a predetermined setpoint voltage, said error amplifier operative to determine the difference between said voltage output and said setpoint voltage and generate a command current signal to linearly control said current source.

5. A power supply according to claim 4 and further including:

a multiplying digital-to-analog converter disposed between said error amplifier and said current source; and

a digital controller coupled to said digital-to-analog converter and including memory for storing a scaling factor, said controller operative to load said scaling factor into said multiplying digital-to-analog converter and establish a maximum level of current into said current source.

6. A power supply according to claim 5 and further including:

a clamping circuit interposed between said multiplying digital-to-analog converter and said current source.

7. A power supply according to claim 1 wherein:

said capacitive element comprises a capacitor having respective positive and negative voltage terminals.

8. A power supply according to claim 7 wherein:

said output is referenced to said capacitor negative terminal.

9. A power supply according to claim 1 and further including:

a pre-regulated voltage source; and

said power device including an input coupled to said voltage source.

10. A power supply according to claim 1 wherein:

said power device comprises a MOSFET.

11. A power supply with a programmable voltage slew rate for generating a regulated voltage at a predetermined set-point, said power supply including:

current generating means for generating a controllable level of current flow;

reference means coupled to said current source and comprising a capacitive element, the reference means responsive to said current flow to establish a reference voltage, said reference voltage varying linearly with respect to variations in said current flow; and

power means coupled to said reference means and having an output operative to generate an output voltage following that of said reference voltage.

12. A power supply according to claim 11 wherein:

said current generating means comprises a programmable current source.

13. A power supply according to claim 11 wherein:

said capacitive element comprises a capacitor.

14. A power supply according to claim 11 wherein:

said power means comprises a power device having a control element electrically connected to said reference voltage and an output for driving said load.

15. A power supply according to claim 14 wherein:

said power means output is referenced to said capacitive element.

16. A power supply according to claim 14 wherein:

said power device comprises a MOSFET.

17. A power supply with a programmable voltage slew rate for generating a regulated voltage at a predetermined set-point, said power supply including:

a programmable current source for generating a controllable level of current flow;

a capacitive element coupled to said current source and responsive to said current flow to establish a reference voltage, said reference voltage varying linearly with respect to variations in said current flow; and

a power device having a control element electrically connected to said reference voltage and an output for driving a load, said output operative to generate an output voltage following that of said reference voltage;

a feedback circuit including an error amplifier for detecting said output voltage and controlling said current source based on said output voltage level;

a multiplying digital-to-analog converter disposed between said error amplifier and said current source;

a digital controller coupled to said digital-to-analog converter and including memory for storing a scaling factor, said controller operative to load said scaling factor into said multiplying digital-to-analog converter and establish a maximum level of current into said current source; and

a clamping circuit interposed between said multiplying digital-to-analog converter and said current source.

18. A power supply with a programmable voltage slew rate for generating a regulated voltage at a predetermined set-point, said power supply including:

a programmable current source for generating a controllable level of current flow;

a capacitive element coupled to said current source and responsive to said current flow to establish a reference voltage, said reference voltage varying linearly with respect to variations in said current flow; and

a power device having a control element electrically connected to said reference voltage and an output for driving a load, said output operative to generate an output voltage following that of said reference voltage;

a feedback circuit including an error amplifier for detecting said output voltage and controlling said current source based on said output voltage level;

a multiplying digital-to-analog converter disposed between said error amplifier and said current source; and

a digital controller coupled to said digital-to-analog converter and including memory for storing a scaling factor, said controller operative to load said scaling factor into said multiplying digital-to-analog converter and establish a maximum level of current into said current source.

19. A power supply according to claim 18 and further including:

a clamping circuit interposed between said multiplying digital-to-analog converter and said current source.

20. A method of linearly varying the set point of a regulated voltage power supply, said power supply including a programmable current source, a capacitive element coupled to said current source, and a power device having a control element electrically connected to said capacitive element and an output, said method including the steps of:

operating said power supply in a floating configuration wherein the programmable current source is controlled with reference to an output voltage and without reference to an external ground; and

varying current from said current source to vary said reference voltage.

21. A method of controlling the slew rate of a regulated voltage power supply, said power supply including a programmable current source, a capacitive element coupled to said current source, and a power device having a control element electrically connected to said capacitive element and an output, said method including the steps of:

charging said capacitive element to generate a reference voltage;

sensing said reference voltage with said control element; and

generating an output voltage at said power device output that follows said reference voltage, said charging step effective to adjust said reference voltage to correspondingly create a proportional change in said output voltage.

22. A method according to claim 21 wherein:

said step of charging includes driving said capacitive element with current from said current source.

23. A method according to claim 22 wherein:

said step of driving includes programmably injecting current into said capacitive element according to predetermined instructions.

24. A method according to claim 23 wherein:

said injecting step includes varying said reference voltage linearly with changes in said current flow.

25. A method according to claim 21 and further including the step of:

referencing said reference voltage to said power device output.