Electric power conversion systems – Current conversion – With starting arrangement
Patent
1994-01-28
1995-10-17
Wong, Peter S.
Electric power conversion systems
Current conversion
With starting arrangement
363 21, 363 41, 363 97, 323901, H02M 3335
Patent
active
054596521
ABSTRACT:
A boot strap control circuit including a depletion mode NMOS transistor to effectively switch a boot strap bleed resistor out of the circuit after power up is achieved. The NMOS transistor is initially turned fully on to allow current to flow through the bleed resistor to a pulse width modulation circuit (PWM) upon power up and to allow early control by the PWM. When the PWM reaches operating power, it asserts its reference voltage output high, activating a transistor switch to turn the NMOS transistor fully off. A capacitor maintains power to the PWM until an auxiliary winding of the power transformer develops sufficient voltage to operate the PWM. In the event of failure of the auxiliary winding, the NMOS transistor operates discretely, turning on and off at a low duty cycle, rather than operating in the linear mode. In this manner, the NMOS transistor and bleed resistor assure low power during normal operation and safe operation at all times.
REFERENCES:
patent: 4063307 (1977-12-01), Stephens
patent: 4866590 (1989-09-01), Odaka et al.
patent: 5014178 (1991-05-01), Balakrishnan
patent: 5124630 (1992-06-01), Tsutsumi
patent: 5350997 (1994-09-01), Ghotbi et al.
Compaq Computer Corp.
Riley Shawn
Wong Peter S.
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