An electronic control system having a boost converter circuit with an input for receiving a first DC voltage from a source of power and an output for delivering a second DC voltage to a load. The boost converter includes a main power transistor and a primary control circuit for providing a first control signal to control the main power transistor. The first control signal from the primary control circuit effects the maximum allowable current flowing in the main power transistor. The system includes a secondary control circuit having a temperature detector that provides a second control signal for overriding the first control signal of the primary control circuit. The temperature detector is mounted in thermal relation to the main power transistor, and the secondary control circuit is capable of reducing the maximum current flowing in the main power transistor based on a third signal received from the temperature detector.