Electric power conversion systems – Current conversion – Including d.c.-a.c.-d.c. converter
Patent
1993-10-27
1996-01-30
Sterrett, Jeffrey L.
Electric power conversion systems
Current conversion
Including d.c.-a.c.-d.c. converter
363 49, 363 97, 363131, H02M 3335
Patent
active
054885515
ABSTRACT:
A pulse width modulated power supply comprises a power transformer having a primary winding, a secondary winding and means for coupling one end of the primary winding to a DC power supply. A semiconductor switch is coupled to the other end of the primary winding to control power through the primary winding. A rectifier is connected across the secondary winding to rectify current induced in the secondary winding, and supplies the rectified current to an output capacitor to develop a DC output voltage. A control circuit controls the duty cycle of the switch based on charging time of a first, relatively small capacitor during start up. The resultant voltage is compared to a reference voltage and when the voltage across the first capacitor just exceeds the reference voltage, the switch is turned off. Because the first capacitor is relatively small, the charging time is short and widths of pulses through the primary winding are relatively short during start up. This reduces heating of the switch during start up. The control circuit controls the duty cycle of the switch based on charging time of the first capacitor and a second, relatively large capacitor in parallel afterwards such that widths of pulses through the primary winding are relatively long and the power supply can supply operating current to the load.
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International Business Machines - Corporation
Samodovitz Arthur J.
Sterrett Jeffrey L.
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