H-bridge circuit with protection against crossover conduction
US5309347A · kind A · utility
Assignees
Inventors
Key dates
| Filing date | Sep 18, 1992 |
| Grant date | May 3, 1994 |
| Priority date | — |
| Expiry date | Sep 18, 2012 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH03K17/663
- WIPO fieldBasic communication processes
- WIPO sectorElectrical engineering
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.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.