METHOD AND APPARATUS FOR CURRENT DERATING WITH INTEGRATED TEMPERATURE SENSING

摘要

A method and apparatus for derating current in a camera LED flash is provided. The method comprises monitoring a local junction temperature of a module (802). The local junction temperature is converted into a local junction current (804), which is a function of the local junction temperature. The local junction current is then compared with a reference current (806), which is independent of temperature or a function of a reference temperature. After the current comparison and subtraction is made (808), a derate control current is obtained to generate the LED reference current. After the temperature crosses the temperature threshold (810), the derate control current is derated at a designated rate (812). Both the temperature threshold and current derate slope are programmable and precisely controlled. The LED output current is regulated and proportional to the LED reference current. If the local junction temperature is greater than the temperature threshold, the LED output current is derated at the moment of the camera flash to avoid thermal overload.