COMPENSATION FOR PARAMETER VARIATIONS IN A FEEDBACK CIRCUIT
First Claim
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.
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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.
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Citations
20 Claims
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1. A power supply, comprising:
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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. - View Dependent Claims (2, 3, 4, 5, 6)
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7. A regulator circuit, comprising:
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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. - View Dependent Claims (8, 9, 10, 11, 12, 13, 14)
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15. A regulator circuit, comprising:
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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 VBE 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 VBE. - View Dependent Claims (16, 17, 18, 19, 20)
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Specification