COMPENSATION FOR PARAMETER VARIATIONS IN A FEEDBACK CIRCUIT

• US 20090201701A1
• Filed: 04/22/2009
• Published: 08/13/2009
• Est. Priority Date: 09/13/2004
• Status: Active Grant

• Current Assignee: Power Integrations Incorporated
• Original Assignee: Power Integrations Incorporated
• Inventors: Odell, Arthur B., Cuadra, Jason E., Polivka, William Michael
• Granted Patent: US 7,813,150 B2
• Time in Patent Office: Days
• US Class Current: 363/21.150
• CPC Class Codes: H02M 1/0025 Arrangements for modifying reference values, feedback values or error values in the control loop of a converter
• CPC Class Codes: H02M 1/32 Means for protecting converters other than automatic disconnection
• CPC Class Codes: H02M 3/33523 with galvanic isolation between input and output of both the power stage and the feedback loop
• CPC Class Codes: Y10S 323/902 Optical coupling to semiconductor
• CPC Class Codes: Y10S 323/907 Temperature compensation of semiconductor

Abstract

Techniques to compensate for parameter variations in a feedback circuit are disclosed. In one embodiment, a regulator circuit includes an energy source coupled to output a generated current in response to a control current. A feedback resistor is coupled to an output of the regulator circuit. The feedback resistor is coupled to conduct a feedback current responsive to the output of the regulator circuit. A current amplifier is coupled to the feedback resistor to generate the control current in response to the feedback current. A compensation network is coupled to the current amplifier to adjust the control current in response to an extrinsic parameter of the regulator circuit. The compensation network includes a transistor and first, second and third resistors. The first resistor is coupled between the feedback resistor and a collector of the transistor. The second resistor coupled between the collector and the base of the transistor. The third resistor coupled between the base and an emitter of the transistor.

Claims

1. A power supply, comprising:

an energy transfer element having a primary winding and a secondary winding;

an integrated circuit coupled to the primary winding to produce an output between a first and a second output terminal of the power supply;

an optocoupler including;

a photodiode coupled to conduct an input current; and

a phototransistor optically coupled to the photodiode to provide a control current to the integrated circuit in response to the input current, wherein the integrated circuit produces the output between the output terminals of the power supply in response to the control current; and

a compensation network coupled to the photodiode and coupled to generate a compensation current in response to an extrinsic parameter of the power supply, wherein the compensation network is further coupled to adjust a feedback current of the power supply such that the input current is the difference between the feedback current and the compensation current.

2. The power supply of claim 1, wherein the output is a regulated voltage for loads substantially less than a maximum current of the power supply and wherein the output is a regulated current for voltages substantially less than a minimum voltage of the power supply.

3. The power supply of claim 1, wherein the integrated circuit includes a power switch coupled to the primary winding of the energy transfer element, wherein the switch is switched in response to the control signal to produce the output between the first and second output terminals of the power supply.

4. The power supply of claim 1, further comprising a feedback resistor coupled to the second output terminal to conduct the feedback current, wherein the feedback current is responsive to the output of the power supply.

5. The power supply of claim 4, wherein the compensation network comprises a transistor and first, second and third resistors, the first resistor coupled between the feedback resistor and a collector of the transistor, the second resistor coupled between the collector and a base of the transistor, and the third resistor coupled between the base and an emitter of the transistor.

6. The power supply of claim 5, further comprising a current sensing resistor coupled between the second output terminal of the power supply and the emitter of the transistor, wherein an output current of the power supply is regulated by regulating a voltage that appears across the current sensing resistor.

7. A regulator circuit, comprising:

an energy source including a control input coupled to receive a control current, wherein an output of the regulator circuit is responsive to the control current;

an optocoupler including;

a photodiode coupled to conduct a diode current, wherein the diode current is responsive to the output of the regulator circuit; and

a phototransistor optically coupled to the photodiode to generate an emitter current in response to the diode current; and

a compensation network coupled to the control input of the energy source and to the phototransistor to generate a compensation current in response to an extrinsic parameter of the regulator circuit, such that the control current is a difference between the emitter current and the compensation current.

8. The regulator circuit of claim 7, wherein the compensation network includes a first terminal and a second terminal, wherein the first terminal is coupled to a node between the control input and an emitter of the phototransistor and wherein the second terminal is coupled to a ground terminal of the regulator circuit.

9. The regulator circuit of claim 7, wherein a collector of the phototransistor is coupled to a bias voltage and wherein the control input is an input terminal of a power supply controller integrated circuit included in the regulator circuit.

10. The regulator circuit of claim 7, wherein an emitter of the phototransistor is coupled to the control input of the energy source.

11. The regulator circuit of claim 7, wherein the compensation network includes a bipolar transistor, wherein a voltage V_BE between a base and an emitter of the bipolar transistor adjusts in response to the extrinsic parameter of the regulator circuit and wherein the compensation network is coupled to adjust the compensation current in response the voltage V_BE.

12. The regulator circuit of claim 11, wherein the compensation network further includes first, second, and third resistors, the first resistor coupled between an emitter of the phototransistor and a collector of the bipolar transistor, the second resistor coupled between the collector and the base of the bipolar transistor, and the third resistor coupled between the base and an emitter of the bipolar transistor.

13. The regulator circuit of claim 7, wherein the compensation network consists of a bipolar transistor and first, second and third resistors.

14. The regulator circuit of claim 7, wherein the compensation network includes a bipolar transistor, wherein a voltage V_BE between a base and an emitter of the bipolar transistor adjusts by a first amount in response to the extrinsic parameter of the regulator circuit and wherein a reference voltage of the regulator circuit includes a voltage across the photodiode where the reference voltage adjusts by a second amount in response to the extrinsic parameter and wherein the second amount is proportional to the first amount.

15. A regulator circuit, comprising:

an output responsive to a control current;

a feedback current responsive to the output of the regulator circuit;

a current amplifier that produces an amplified current from an input current received at an input terminal having a reference voltage, wherein the input current includes the feedback current, wherein the control current is a difference between the amplified current and a compensation current, wherein the current amplifier includes an optocoupler having a photodiode and a phototransistor, wherein the photodiode is coupled to receive the input current and the phototransistor is coupled to generate the amplified current; and

a compensation network including a bipolar transistor and first, second, and third resistors, the first resistor coupled between the output terminal of the current amplifier and a collector of the bipolar transistor, the second resistor coupled between the collector and the base of the bipolar transistor, and the third resistor coupled between the base and an emitter of the bipolar transistor, wherein a voltage V_BE between the base and the emitter of the bipolar transistor adjusts in response to an extrinsic parameter of the regulator circuit and wherein the compensation network is coupled to adjust the compensation current in response the voltage V_BE.

16. The regulator circuit of claim 15, wherein the extrinsic parameter of the regulator circuit includes at least one of temperature, ionizing radiation, or aging of the regulator circuit.

17. The regulator circuit of claim 15, wherein the reference voltage of the regulator circuit comprises a voltage across the photodiode of the optocoupler.

18. The regulator circuit of claim 15, wherein the reference voltage is a first reference voltage value in response to a first extrinsic parameter value and wherein the reference voltage is a second reference voltage value in response to a second extrinsic parameter value.

19. The regulator circuit of claim 18, wherein the voltage V_BE is a first voltage V_BE value in response to the first extrinsic parameter value and wherein the voltage V_BE is a second voltage V_BE value in response to the second extrinsic parameter value, wherein a difference between the first reference voltage value and the second reference voltage value is proportional to a difference between the first voltage V_BE value and the second voltage V_BE value.

20. The regulator circuit of claim 19, wherein an output voltage of the regulator circuit is substantially the same under the first extrinsic parameter value as the output voltage under the second extrinsic parameter value.