AC regulator

Claim 2

An AC regulator for controlling the current in primary windings of a multiphase transformer comprising: a. a multiphase transformer having a plurality of primary and secondary Y connected windings: b. a full wave rectifying bridge having an AC input coupled to one end of each transformer secondary winding, said bridge having a positive terminal and a negative terminal; c. a full wave rectifying bridge having an AC input coupled to one end of each transformer primary winding, said bridge having a positive terminal and a negative terminal, the negative terminals of said primary and secondary rectifying bridges connected in common to form a voltage reference point; d. a modulator having an input terminal coupled to the positive terminal of the primary rectifying bridge, an output terminal coupled to the voltage reference point and a control input terminal; and e. a drive feedback circuit coupled between the positive terminal of the secondary rectifying bridge and modulator control input terminal for driving the modulator to increase or decrease the current in the transformer primary windings so that voltage across the load remains constant and the ripple in the DC output reduced.

Claim 3

An AC regulator according to claim 1 wherein the modulator is a transistor.

Claim 4

An AC regulator according to claim 1 wherein the comparator means is a differential amplifier and the internal reference is a reference diode, said diode coupled to the non-inverting input of said amplifier and said inverting input coupled to the output of detection means.

Claim 5

An AC regulator according to claim 1 wherein said feedback circuit includes a comparator, an internal DC reference voltage, and an amplifier, the comparator having a first input terminal coupled to the positive output of the secondary rectifying bridge and a second input terminal coupled to the DC reference source for producing an error signal representing the difference between the voltages at the positive output terminal of the secondary rectifying bridge and the DC reference, and an output terminal coupled to the amplifier for feeding the error signal to the amplifier for amplification into a drive signal, said drive signal coupled to the modulator control input, whereby when the voltage at the output of the secondary rectifying bridge rises or falls above or below the DC reference voltage of the comparator the drive signal drives the modulator accordingly to reduce or increase current in the transformer primary windings so that voltage across a load remains constant and the ripple in the DC output reduced.

Claim 6

An AC regulator according to claim 2, wherein the modulator transistor includes a collector, emitter and base, the collector connected to the positive terminal of the primary rectifying bridge, the emitter coupled to the reference junction, and the base coupled to the drive feedback circuit and wherein said drive feedback circuit includes a potentiometer resistor having one end connected to the positive output of the secondary rectifying bridge and its other end connected to the reference junction; a wiper contact for selectively sampling the secondary rectifying bridge output voltage; an operational amplifier having an inverting input terminal and a noninverting input terminal; a source of DC power; a reference diode having an anode and cathode; said operational amplifier having the inverting terminal coupled to the wiper contact and the noninverting terminal coupled to the junction of the source of DC power and the cathode of the reference diode; said reference diode having the anode coupled to the reference junction; and a transistor having a base coupled to the operational amplifier output terminal, a collector coupled to the source of DC power, and an emitter coupled to the junction of a feedback circuit coupled to the inverting terminal of the operational amplifier for stabilizing the operational amplifier by limiting the overall loop gain, an emitter biasing resistor coupled to the reference junction, and the base of the modulator transistor whereby the modulating transistor is driven responsively to changes in the secondary rectifying bridge output voltage to selectively change the current flowing in the primary to maintain constant the output voltage of the secondary rectifying bridge output.