Electric power conversion systems – Current conversion – Including d.c.-a.c.-d.c. converter
Patent
1989-04-10
1989-11-21
Beha, Jr., William H.
Electric power conversion systems
Current conversion
Including d.c.-a.c.-d.c. converter
219 1055B, 323222, 331112, 363131, H02M 3338
Patent
active
048826634
ABSTRACT:
In a flyback converter, a 15 Amp N-channel power MOSFET is driven to saturation by a gate voltage derived by connecting the gate to the relatively high-magnitude (150 volt) B+ voltage by way of a resistor of relatively high resistance (about 20 kilo-Ohm). Current flowing through this resistor causes the gate capacitance (3600 pico-Farad) to charge at a rate of about 2 Volt per micro-second. Since the forward transconductance of the MOSFET is 6 mhos or more, a situation has been established where the MOSFET is effectively fully switched ON as long as the MOSFET's drain current does not rise at a rate higher than about 12 Amp per micro-second.
Eventually, the magnitude of the gate voltage reaches a predetermined maximum level (about 20 Volt), at which point a threshold device, which is connected between gate and source, breaks down and rapidly discharges the base capacitance, thereby rapidly switching the MOSFET into a non-conducting state.
An ordinary bi-polar control transistor is also connected between gate and source, and this control transistor is made conductive by a small current from a secondary winding on the flyback inductor. This control transistor makes the threshold device de-latch and also keeps the gate shorted to the source for as long as the flyback inductor is in the process of discharging its energy.
REFERENCES:
patent: 3435320 (1969-03-01), Lee et al.
patent: 3571697 (1971-03-01), Phillips
patent: 4001867 (1977-01-01), Kravitz et al.
patent: 4445055 (1984-04-01), Bete
patent: 4459539 (1984-07-01), Cordy
patent: 4562527 (1985-12-01), Klampt
Kent, "Single Coil 9V Voltage Converter", New Electronics, vol. 15, No. 6, p. 26, Mar. 23, 1982.
Berzin et al., "Ultralow-Frequency Blocking Oscillator using MOS Transistors," Instrum. & Exp. Tech. (U.S.A.) vol. 20, No. 4, pp. 1092-1094 (Jul.-Aug. 1977) (Publ. Feb. 1978).
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