| 摘要 |
A method and apparatus for switching an electrical load, such as an incandescent lamp, with a FET and providing protection for the FET. An exponential reference signal is generated which is a function of drain to source voltage and represents the integral of instantaneous power dissipated in the FET. Simultaneously, an exponential FET gate signal is initiated for turning on the lamp or other load at a rate which would maximize the power dissipation in the FET under worst case short circuit conditions. The integrated power signal is compared to a critical threshold level which represents the maximum power dissipation rating of the FET. In the event the integrated instantaneous power signal rises above the critical threshold level, which would occur because of an overload, the FET is turned off to protect it and the load from the overload condition.
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