H-bridge circuit with protection against crossover conduction

Details H-bridge circuit with protection against crossover conduction H-bridge circuit with protection against crossover conduction

1992-09-18

1994-05-03

Beha, Jr., William H.

Electric power conversion systems

Current conversion

With means to selectively provide d.c. of either polarity

363 56, H02M 3155

Patent

active

053093470

ABSTRACT:
An H-bridge circuit which includes four power transistors (an npn pull-down and a pnp pull-up for each of the output terminals). Two control circuits are connected to drive these transistors in a complementary crossover configuration, so that each control circuit can turn on the pull-up transistor on one side of the load and the pull-down transistor on the opposite side of the load. Each of the power transistors is paralleled (base-to-base) by a smaller transistor which provides a scaled current output (proportional to that of the corresponding power transistor) to the opposite control circuit. The control circuit includes static current-thresholding disable logic, which prevents turn-on until the currents through the opposite power devices have declined to threshold levels. Thus, as long as either control circuit is driving one of the pull-up transistors into in the on-state, the other control circuit will not be able to turn on the pull-down transistor which is in series with the active pull-up transistor. This efficiently prevents any condition of unlimited crowbar current, without adding any excess delay or causing any high-impedance condition at the output.

REFERENCES:
patent: 3538353 (1970-11-01), Hanger
patent: 3778641 (1973-12-01), Persson
patent: 3828206 (1974-08-01), Zuk
patent: 4551772 (1985-11-01), Sliger
patent: 4633358 (1986-12-01), Nagano
patent: 4796145 (1989-01-01), Oshikiri
patent: 4953070 (1990-08-01), Lenz
patent: 4989114 (1991-01-01), Storti et al.

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