US 3,939,394 AGranted

Constant voltage circuit

AssigneeSony Corporation

InventorTadao Suzuki

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Abstract

A power supply circuit using a silicon controlled rectifier to rectify alternating voltage and apply the rectified voltage across a capacitor. To obtain one polarity of rectified voltage, the cathode of the SCR is connected to the AC source and the output circuit of a switching transistor is connected in series with the gate of the SCR. The input circuit of the transistor is connected in series with a constant voltage element across the capacitor. The switching semiconductor only conducts when the capacitor discharges to a predetermined level. To obtain the opposite polarity rectified voltage the cathode of the SCR is connected to one terminal of the capacitor and, instead of the semiconductor switch, a constant voltage device is connected between the gate of the SCR and the other terminal of the capacitor so that the SCR conducts only when the voltage across the capacitor drops below the voltage of the constant voltage device.

Claims8

Dependent claims

A power supply circuit comprising:

A. first and second input terminals to be connected to an alternating voltage source;
B. first and second output terminals, said second input terminal being connected to said second output terminal;
C. thyristor switching means comprising a first electrode connected to said first input terminal, a second electrode connected to said first output terminal, and a third electrode;
D. semiconductor switching means comprising a first electrode connected to said first output terminal, and second and third electrodes;
E. a first impedance connecting said second electrode of said semiconductor switching means to said third electrode of said thyristor switching means;
F. a second impedance connecting said third electrode of said semiconductor switching means to said first input terminal;
G. a series circuit comprising constant voltage means connecting said third electrode of said semiconductor switching means to said second output terminal;
and
H. a capacitor connected in series between said output terminals.

6 more elements

Dependencies are inferred from the claim text.