VERFAHREN UND SCHALTUNGSANORDNUNG ZUM SCHUTZ EINES TRANSISTORS VOR THERMISCHER ZERSTOERUNG

摘要

The power transistor circuit has a stage that will guarantee protection against thermal overload without any time delay. A barrier layer for blocking the flow of energy can be set at an predetermined temperature. The base-emitter voltage of the transistor to be protected is compared with an internal reference voltage in a comparator. The result triggers a cut-out system, when a given voltage is exceeded. There is a thermally decoupled transistor (2) immediately in front of the protected transistor (1). There is a third transistor (3) which supplies the base current for the first two transistors. The third transistor is controlled via a drop resistor (7). An additional resistor (6) switches on the required base current again, and two diodes (4, 5) the short circuit current.