Switching voltage regulator with optical coupling

Claim 1

A voltage regulator comprising, a transformer having a primary winding and a secondary winding, first and second, transistors connected to switch a current through the primary winding to produce in alternating voltage across the secondary winding, means to turn said two transistors on and off alternately, and means for connecting said secondary winding to supply a voltage to a load, means for comparing said load voltage with a reference and for providing a first signal according to the difference between the load voltage and the reference, a third transistor connected to supply said current to said transformer and a resistor connected to provide a second signal proportional to said current, a differential amplifier having fourth and fifth transistors of a first conductivity type, and means connected to provide a current differentially to the emitter terminals of said fourth and fifth transistors, means connecting said fourth transistor to receive a reference voltage, means connecting said fifth transistor to receive said first signal and said second signal, a sixth transistor of opposite conductivity type connected in the collector circuit of said fifth transistor to limit the current in said third transistor, and means connecting the collector terminal of said fourth transistor to control said third transistor to supply said current to said transformer at a value to maintain said load voltage.