200 DEGREES-C OPERATION OF A 500-W DC-DC CONVERTER UTILIZING POWER MOSFETS

This paper presents results from the operation of the power stage of a 500-W dc-dc converter at an ambient temperature of 200 degrees C, Thi s converter is designed to provide an output voltage of 42-Vdc from a 28-Vdc input, It utilizes an H-bridge configuration composed of eight International Rectifier power MOSFET's (parallel connections of two MO SFET's) and four Motorola diodes to convert the dc input voltage to a high-frequency square wave which can then be stepped up with a transfo rmer, The transformer output voltage is then rectified and filtered to produce the dc output voltage, A phase-shifted pulsewidth modulation (PWM) switching scheme is utilized to control the MOSFET's in the H br idge. This scheme allows zero-voltage turn-on of the MOSFET's to impro ve the efficiency, The efficiency of this converter when operated on t he laboratory bench was measured to be 89%. The H bridge and transform er were then placed in an oven and operated over an ambient temperatur e range of 20 degrees C-200 degrees C. The efficiency varied from 86.1 % to 85.4% over this temperature range, The long feedthroughs for oven operation caused the efficiency to decrease from 89% to 86.1%.