Apparatus and method for balancing output current of transistors

Details Apparatus and method for balancing output current of transistors Apparatus and method for balancing output current of transistors

1987-11-04

1988-11-01

Beha, Jr., William H.

Electric power conversion systems

Current conversion

Including automatic or integral protection means

330272, 363 26, 363134, H02H 7122, H02M 7538

Patent

active

047824360

ABSTRACT:
An apparatus for allowing the use of unmatched transistors in a power supply is shown. A potentiometer (482) and a switch (481) divert base drive current away from the transistor having the higher Beta so that the collector currents of the two transistors (477, 484) can be matched. Heat sensitive resistors (480, 483) are thermally connected to the opposing transistor (484, 477) so if the temperature and collector current of one transistor should increase the base drive to the other transistor is automatically increased, thereby causing the collector currents to remain matched. The total collector current provided by the transistors (477, 484) is limited to a safe value by a regulating pulsewidth modulator (457). The use of additional protective diodes (468, 469, 478, 479) prevent transient voltages from affecting the transistors (477, 484) and allow the use of lower power, less expensive transistors.

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patent: 4672175 (1987-06-01), Niven

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