Electric power conversion systems – Current conversion – Including d.c.-a.c.-d.c. converter
Patent
1984-12-21
1986-12-16
Wong, Peter S.
Electric power conversion systems
Current conversion
Including d.c.-a.c.-d.c. converter
363 97, 323289, H02M 3335
Patent
active
046301860
ABSTRACT:
A switching power source circuit intermittently switches a current at a primary winding of a transformer in accordance with the repeated switching of a bipolar transistor so as to rectify and smooth a voltage induced at a secondary winding of the transformer, thereby obtaining an output voltage. A capacitor is charged by a voltage induced by a feedback winding of the transformer. The base-emitter path of the bipolar transistor is reverse biased by this charge voltage so as to perform high-speed switching, so that a compact transformer and capacitor can be used and the switching power source circuit becomes low in cost.
The application of the reverse bias voltage is performed by a transistor which is turned on when an emitter (grounded through a resistor) voltage of the bipolar transistor is increased to a predetermined level (threshold). A switching period of the bipolar transistor is determined by a period determining circuit consisting of a timing capacitor and a resistor. The timing capacitor is charged to reverse bias the bipolar transistor when the bipolar transistor is turned on. The timing capacitor is discharged when the bipolar transistor is turned off. An auxiliary winding is arranged in the transformer to detect flyback energy, and the ON and OFF times of the bipolar transistor are controlled to stabilize the output voltage even if an output terminal is overloaded.
REFERENCES:
patent: 3662249 (1972-05-01), Wijsboom
patent: 4361865 (1982-11-01), Shono
Stanley Electric Co. Ltd.
Wong Peter S.
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