Patent ID: 7023005

Claim:
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.