Voltage regulated power supply having low ripple factor

Claim 2

In a power supply providing a regulated DC output voltage to a load from a source of unregulated input voltage and including an active variable impedance means having input, output and control electrodes, the active variable impedance means connected with its input and output electrodes in series with the source and the load, a voltage comparator means coupled to compare the regulated DC output voltage with a reference voltage and generate a DC signal representative of a DC error in said regulated DC output voltage, a DC amplifier coupled to amplify the representative signal and provide a DC error signal to the control electrode of the active variable impedance means to change its impedance and correct the DC error in the regulated DC output voltage, and a constant current generator coupled to provide a constant current load to the control electrode of the active variable impedance means and DC amplifier from the source of unregulated input voltage, the combination therewith comprising; a high-gain AC amplifier without significant DC gain relative to the AC gain having an input terminal and an output terminal, said input terminal coupled to receive a signal representative of the instantaneous voltage of AC signal components superimposed on the regulated DC output voltage, said AC amplifier responsive to the superimposed AC signal components to generate at its output terminal an amplifier AC signal without corresponding amplification of any DC voltage present at the input terminal, and feedback means coupled to the output terminal of the AC amplifier to receive the amplified AC signal and provide an AC error signal to the control electrode of the active variable impedance means in phase opposition to corresponding AC signal components coupled thereto from the source of unregulated input voltage.

Claim 3

The power supply according to claim 1 wherein the high-gain AC amplifier has a DC gain of about unity, the input terminal of said high-gain AC amplifier is coupled to receive a signal representative of the regulated DC output voltage and the superimposed instantaneous voltage of the AC signal components, said AC amplifier generates at its output terminal the amplified AC signal components superimposed on a DC voltage which varies according to the change in the regulated DC output voltage, the output terminal of the AC Amplifier is directly coupled to an input of said DC amplifier, said DC amplifier responsive to the output of the AC amplifier to amplify the instantaneous difference between the DC voltage with the superimposed amplified AC signal components and the said reference voltage to provide to the control electrode of said active variable impedance means a composite error signal including the AC error signal superimposed on the DC error signal.

Claim 4

The power supply according to claim 2 wherein the AC gain of the AC amplifier and the gain of the DC amplifier are set and the signal representative of the regulated DC output voltage and superimposed AC signal components is selected to maintain the power supply unconditionally stable while substantially cancelling the DC error and AC signal components present in the regulated DC output voltage in a selected frequency range.

Claim 5

The power supply according to claim 2 wherein the active variable impedance means includes at least one control transistor having collector, emitter and base, the collector and emitter connected in series and poled to conduct current between one terminal of the source and one side of the load, the other side of the load is coupled to the other terminal of the source, the DC amplifier is a transistor having collector, emitter and base, the collector and emitter coupled in series and poled to conduct current between the base of the control transistor and other terminal of the source, the voltage comparator means includes a Zener diode and resistor network connected in parallel with the load and to the emitter and base circuit of the DC amplifier the Zener diode is reversed biased to provide the reference voltage to bias the emitter and base junction of the DC amplifier transistor so that a change in the regulated DC output voltage is productive of a proportionate change in the emitter-to-collector current of the DC amplifier transistor, the constant current generator provides a constant current to the base of the control transistor and the emitter and collector circuit of the DC amplifier transistor so that a change in the emitter-to-collector current of the DC amplifier transistor causes an inversely proportioned change in the base current and hence impedance of the control transistor, and the high-gain AC amplifier is a transistor having a collector, emitter and base, the collector and emitter connected and poled to conduct current in parallel with the load, the emitter electrode connected in series with a parallel connected emitter resistor and AC bypass capacitor, the collector electrode connected in series with a collector resistor, the collector directly connected to the base of the DC amplifier transistor, the base of the AC amplifier transistor coupled to receive a signal representative of the regulated DC output voltage and superimposed AC signal components.

Claim 6

The power supply according to claim 4 wherein the collector resistor of the AC amplifier transistor has an impedance of a magnitude on the order of the magnitude of the emitter resistor, the capacitor has an impedance over a selected frequency of at least one order of magnitude less than the impedance of the collector resistor.