Overcurrent and overtemperature protective circuit for power transistor system
US4360852A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Apr 1, 1981 |
| Grant date | Nov 23, 1982 |
| Priority date | — |
| Expiry date | Apr 1, 2001 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH03K2017/0806
- WIPO fieldBasic communication processes
- WIPO sectorElectrical engineering
Abstract
A power transistor switch is protected against thermal destruction that might be caused by accidental short circuiting of the load being switched by a protective circuit having a base-drive-removing transistor in shunt to the base-emitter junction of the power transistor; an RC circuit including a capacitor in series with a resistor connected across the power transistor with the capacitor coupled across the base-emitter junction of the base-drive-removing transistor; a forward-biased shunting transistor connected across the capacitor; a shunt-removing transistor connected across the base-emitter junction of the shunting transistor; and a turn-on transistor triggerable to the conductive state by a turn-on signal for applying base drive to the power transistor and for forward biasing the shunt removing transistor to thereby turn off the shunting transistor and permit the capacitor to charge. Excessive current flow through the power switch causing it to desaturate results in charging the capacitor and consequent turning on the base-drive-removing transistor to thereby remove base current from the power transistor and turn it off.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.