Power supply capable of being configured to generate positive and negative output resistances

• US 6,459,247 B1
• Filed: 11/21/2000
• Issued: 10/01/2002
• Est. Priority Date: 11/21/2000
• Status: Expired due to Fees

• Current Assignee: Agilent Technologies Europe BV (Agilent Technologies, Inc.)
• Original Assignee: Agilent Technologies, Inc.
• Inventors: Benes, Michael Joseph
• Primary Examiner(s): Patel, Rajnikant B.
• Application Number:
  US09/717,764
• Time in Patent Office: 679 Days
• Field of Search: 363/63, 363/60, 363/59, 323/277, 323/280, 323/281, 323/282, 323/283, 323/288, 327/334, 327/103
• US Class Current: 323/281
• CPC Class Codes: G05F 1/56 using semiconductor devices in series with the load as final control devices G05F1/461 takes precedence

Abstract

The present invention relates to a power supply capable of being configured to produce an equivalent negative output resistance or to produce both negative and positive output resistances. The power supply comprises components that can provide equivalent output resistance values that transition from negative values through zero to positive values, and vice versa. By selecting an appropriate negative output resistance for the power supply, the power supply can compensate for the load lead voltage drop caused by the elements (e.g., cabling) between the output sense leads of the power supply and the load. This allows the voltage level provided to the load to be set, or controlled, by setting a voltage level V_SET at the power supply. Preferably, a multiplier chip is used that enables the output resistance values of the power supply to be programmably varied from a negative resistance value through 0 to a positive resistance value, and vice versa. The multiplier chip receives a reference voltage V_REF that can be varied in order to vary the output resistance of the power supply.

Claims

1. A power supply comprising:

a voltage source having an output resistance;

first and second output sense terminals;

output resistance control circuitry which controls the output resistance according to a product of a current supplied by the voltage source and a predetermined value; and

output voltage control circuitry which controls a voltage of the voltage source according to a feedback voltage at the first and second output sense terminals.

2. The power supply of claim 1, wherein the output resistance control circuitry is controllable to provide the output resistance in a range including positive and negative values.

3. The power supply of claim 1, wherein the output voltage control circuitry is variable to select the voltage to be supplied to the load.

4. The power supply of claim 1, wherein the output resistance control circuitry comprises a multiplier integrated circuit having first and second input terminals and an output terminal, the first input terminal of the multiplier integrated circuit receiving a reference voltage that is variable to vary the output resistance of the voltage source, the second input terminal receiving a voltage proportional to the current supplied by the voltage source.

5. The power supply of claim 4, wherein:

the output resistance control circuitry is controllable to provide the output resistance in a range including positive and negative values; and

the reference voltage provided to the first input terminal of the multiplier integrated circuit is variable to produce smooth transitions in the output resistance from the negative output resistance values to the positive output resistance values and from the positive output resistance values to the negative output resistance values.

6. The power supply of claim 5, wherein the reference voltage supplied to the first input terminal of the multiplier integrated circuit is electrically coupled to a potentiometer circuit to enable the reference voltage to be programmably varied.

7. The power supply of claim 5, wherein the first input terminal of the multiplier integrated circuit is electrically coupled to a digital-to-analog converter to enable the reference voltage to be programmably varied.

8. The power supply of claim 1, further comprising:

a buffer stage driven by an error amplifier which has a negative input terminal, a positive input terminal and an output terminal, wherein the negative input terminal of the error amplifier acts as a summing, junction and is electrically coupled to a compensation network, a current feedback scaling resistor, a voltage feedback scaling resistors and a voltage set point scaling resistor, the positive input terminal of the error amplifier being electrically coupled to common, the output of the error amplifier being electrically coupled to the compensation network and buffer stage; and

a differential amplifier having a negative input terminal, a positive input terminal and an output terminal, the positive input terminal of the differential amplifier being electrically coupled to the first output sense terminal of the power supply, the negative input terminal of the differential amplifier being electrically coupled to the second output terminal of the power supply, the output terminal of the differential amplifier being electrically coupled to the negative input terminal of the error amplifier, wherein the output resistance control circuitry is electrically coupled to the negative input terminal of the error amplifier and to the second output sense terminal of the power supply.

9. A power supply comprising:

a voltage source having an output resistance;

first and second output sense terminals;

means for controlling the output resistance to provide a negative output resistance; and

means for controlling the voltage source in response to a feedback voltage at the first and second output sense terminals to provide a selected output voltage level to a load electrically coupled to the output sense terminals.

10. The power supply of claim 9, wherein the means for controlling the output resistance is controllable to produce the negative output resistance or a positive output resistance.

11. The power supply of claim 9, wherein the means for controlling the voltage source is variable to change the selected output voltage level being supplied to the load.

12. The power supply of claim 9, wherein the means for controlling the output resistance comprises a multiplier integrated circuit having first and second input terminals and an output terminal, the first input terminal of the multiplier integrated circuit receiving a reference voltage that can be varied to thereby vary the output resistance of the voltage source, the second input terminal receiving a voltage proportional to a current supplied by the voltage source.

13. The power supply of claim 12, wherein:

the means for controlling the output resistance is controllable to produce the negative output resistance or a positive output resistance; and

the reference voltage being provided to the first input terminal of the multiplier integrated circuit is variable to cause the output resistance of the voltage source to continuously transition from the negative output resistance to the positive output resistance, and vice versa.

14. The power supply of claim 13, wherein the first input terminal of the multiplier integrated circuit is electrically coupled to a potentiometer circuit to enable the reference voltage to be programmably varied.

15. The power supply of claim 13, wherein the first input terminal of the multiplier integrated circuit is electrically coupled to a digital-to-analog converter to enable the reference voltage to be programmably varied.

16. A method of supplying power to a load, the method comprising:

providing power to the load from a voltage source having a settable output voltage and a controllable output resistance;

setting a voltage to be supplied to the load; and

controlling the output resistance in response to sensing a current through the load to maintain the load voltage.

17. The method of claim 16, wherein the setting of the voltage to be supplied to the load comprises setting a voltage level, −

V_SET, such that an open circuit voltage at the load is linearly proportional to V_SET.

18. The method of claim 16, wherein:

during the setting of the voltage to be supplied to the load, the voltage source uses feedback received from the load to compensate for a load lead voltage drop at the load.

19. The method of claim 16, wherein:

the controlling of the output resistance comprises;

multiplying the sensed load current by a predetermined value; and

controlling the output resistance using the multiplied sensed load current as feedback.

20. The method of claim 19, wherein the the predetermined value is programmably variable.

21. A power supply for supplying a voltage and a current to a load, the power supply comprising:

a voltage source having a source resistance and which supplies the load voltage and the load current;

a control circuit which;

sets the load voltage at a predetermined load current in response to a first reference value, and

controls the source resistance in a range including positive and negative values according to a control value, the control value determined by adjusting a measure of the load current with a second reference value.

22. The power supply of claim 21, wherein the control circuit comprises:

an amplifier which;

sums the first reference value and a feedback value analogous to the load voltage to set the load voltage at the predetermined load current, and

adds the control value to the sum of the first reference value and the feedback value to control the source resistance;

a shunt which converts the load current to the measure of the load current; and

a multiplier which multiplies the measure of the load current by the second reference value to provide the control value.

23. The power supply of claim 21, wherein the control circuit further comprises a digital to analog converter and the digital to analog converter outputs the second reference value based on a digital input to the digital to analog converter.

24. The power supply of claim 21, wherein the power supply further comprises a potentiometer circuit which outputs the second reference value.

25. A power supply for supplying a load voltage and a load current to a load, the power supply comprising:

a voltage source;

a control circuit which;

sets the load voltage at a predetermined load current in response to a first reference value, and

controls an effective source resistance of the load voltage in a range including positive and negative values according to a control value, the control value determined by feeding back one of a measure of the load current and an inverted measure of the load current, the control circuit connected between the voltage source and the load.

26. The power supply of claim 25, wherein the control circuit comprises:

an amplifier which;

sums the first reference value and a feedback value analogous to the load voltage to set the load voltage at the predetermined load current, and

adds the control value to the sum of the first reference value and the feedback value to control the effective source resistance;

a shunt which converts the load current to the measure of the load current;

an inverter which inverts the measure of the load current to provide the inverted measure of the load current;

a switch which selects one of the measure of the load current and the inverted measure of the load current; and

an attenuator which attenuates the selected measure of the load current to provide the control value.

27. The power supply of claim 26, wherein the attenuator is a variable attenuator.

28. An apparatus for testing a battery powered device, comprising:

a voltage source having a controllable source resistance;

a control circuit which;

sets an input voltage of the device at a predetermined load current of the device in response to a first reference value, and

controls the source resistance in a range including positive and negative values according to a control value, the control value determined by multiplying a measure of the load current by a second reference value.

29. The apparatus of claim 28, wherein the control circuit comprises:

an amplifier which;

sums the first reference value and a feedback value analogous to the device voltage to set the device voltage at the predetermined load current, and

adds the control value to the sum of the first reference value and the feedback value to control the source resistance;

a shunt which converts the device current to the measure of the device current; and

a multiplier which multiplies the measure of the device current and the second reference value to provide the control value.

30. The apparatus of claim 28, wherein the control circuit further comprises a digital to analog converter and the digital to analog converter outputs the second reference value based on a digital input to the digital to analog converter.

31. The power supply of claim 28, wherein the apparatus further comprises a potentiometer circuit which outputs the second reference value.

32. A method of testing a battery powered device, comprising:

providing current to the device from a voltage source having a controllable source resistance;

setting an output voltage of the voltage source at a first value of device current;

measuring the device current;

regulating the voltage source by monitoring a voltage intermediate the voltage source and the device; and

controlling the source resistance according to a factor determined by multiplying the measure of the device current by a predetermined value.

33. The method of claim 32, further comprising controlling the source resistance by multiplying the multiple of measure of the device current and the predetermined value by minus one.

34. An apparatus for powering a load, comprising:

means for supplying a voltage and a current to the load;

means for inputting first and second reference values;

means for regulating the voltage in response to the first reference value;

means for providing a measure of the current;

means for multiplying the measure of the current by the second reference value to provide a control value; and

means for controlling a source resistance of the supplied voltage in a range including positive and negative values in response to the control value.