LOAD CONTROL SYSTEM HAVING AN OVERLOAD PROTECTION CIRCUIT

摘要

A load control circuit (36) having an overload circuit capable of protecting a switching element (26) from overload conditions over a wide range of operating conditions. The overload circuit limits the maximum average power dissipation of the switching element (26) in accordance with a comparison of an average voltage across the switching element over a half-cycle and a variable threshold. The variable threshold is determined based on an ON-state resistance of the switching element (26) and the environment in which the switching elements are operating. The variable threshold accounts for the squared term (V2 or I2) in determining power dissipation and allows power to be determined based on average voltage.