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US 2003/0117698 A1Published application
Gain compensation for optocoupler feedback circuit
AssigneeTexas Instruments Incorporated
InventorsDavid A. Williams, Michael G. Amaro
Life of this patent
Estimating the term…
Abstract
A feedback circuit has an optical coupler with a feedback gain control. The feedback gain control includes an active element connected to vary current flow depending on changes in gain of the optical coupler.
Claims21
A feedback gain control for an optical coupler feedback circuit, comprising:
- an optical coupler having input leads and output leads isolated from said input leads;
- a current monitor connected to said input leads;
- a reference level;
- a operational amplifier having a first input connected to said current monitor and a second input connected to said reference level, an output of said operational amplifier connected to vary current to said input leads of said optical coupler depending on input signals to said operational amplifier.
1 more element
A feedback gain control for an optical coupler feedback circuit, comprising:
- an optical coupler having input leads and output leads isolated from said input leads;
- a current monitor connected to said input leads;
- and
- an active element connected to respond to changes in current flow as detected by said current monitor and connected to vary current at said input leads of said optical coupler.
1 more element
A method for gain control of an optical coupler feedback circuit, comprising the steps of:
- monitoring a current at an input of an optical coupler in said optical coupler feedback relative to a reference;
- and
- varying a current supplied to said input of said optical coupler depending on variation of said current from said reference to effect a substantially constant gain of said optical coupler feedback circuit over a lifetime of the optical coupler feedback circuit.
A power supply, comprising:
- a power transformer having an input side and an output side;
- a rectifier connected to said output side of said power transformer and having an output at which is available an output voltage;
- a operational amplifier connected to said output of said rectifier and connected to a first reference value, said operational amplifier having an output;
- a first active element having a control input connected to said output of said operational amplifier;
- an optical coupler having an input and an output isolated from said input, said input being connected to be controlled by said first active element;
- a control circuit having an input connected to said output of said optical coupler and an output connected to said input side of said power transformer;
- a voltage divider connected to receive at least a portion of a current through said first active element and said input of said optical coupler;
- a second active element connected to selectively draw current from said first active element and said input of said optical coupler, said second active element operating relative to a second reference value to hold a gain through said optical coupler substantially constant.
5 more elements
A gain controlled feedback circuit, comprising:
- an optical coupler having an input and an output isolated from said input;
- a first transistor connected to said input of said optical coupler;
- a first operational amplifier having an output connected to a control input of said first transistor, said first operational amplifier having first and second inputs connected to a first reference value and to a value to be controlled;
- a voltage divider connected to said first transistor;
- a second operational amplifier having first and second inputs connected to a second reference value and to said voltage divider;
- and
- a second transistor having a control input connected to an output of said second operational amplifier, said second transistor having a controllable current path connected to said first transistor to draw off current from said voltage divider depending on gain variations of said optical coupler.
4 more elements
Dependencies are inferred from the claim text.