Electric power conversion systems – Current conversion – Including d.c.-a.c.-d.c. converter
Patent
1995-09-07
1997-06-10
Wong, Peter S.
Electric power conversion systems
Current conversion
Including d.c.-a.c.-d.c. converter
363 95, H02M 3335, H02M 324, H02M 542, H02M 744
Patent
active
056382626
ABSTRACT:
An isolated low power converter including a low voltage, self-oscillating power converter, which derives power through bleeder current from the relatively high-voltage, input bulk capacitors. A bleeder circuit taps a relatively low voltage current source from the bulk capacitors to supply an oscillator circuit. The bleeder circuit preferably incorporates current limit resistors typically provided according to safety specifications. The oscillator circuit is preferably implemented using the primary of a transformer. A simple regulator circuit coupled to the secondary of the transformer provides a low voltage SELV power signal for powering detection circuitry. In the preferred embodiment, the bleeder circuit includes a relatively large resistive voltage divider for supplying current to charge a capacitor. The voltage of the capacitor is regulated using a constant voltage device, such as one or more Zener diodes. The oscillator is implemented in a very simple and inexpensive manner, including a switching transistor having a current path coupled to the primary inductor of the transformer, a current limiter coupled between the current path of the transistor and primary ground, a bias circuit coupled to the control terminal of the transistor and a voltage regulating device coupled between the control terminal of the transistor and ground. The transformer preferably includes a tertiary winding coupled between the other end of the voltage divider and the current limiter for facilitating oscillation.
REFERENCES:
patent: 5175675 (1992-12-01), Uramoto
patent: 5341279 (1994-08-01), Yamada
patent: 5424932 (1995-06-01), Inou et al.
patent: 5499184 (1996-03-01), Squibb
Dell USA L.P.
Stanford Gary R.
Vu Bao Q.
Wong Peter S.
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