Discharge lamp e.g. metal halide lamp, lighting circuit for use in vehicle headlight, has control circuitry comprising differential computation circuitry to differentiate signal according to voltage between electrodes

摘要

The circuit (1) has a control circuitry comprising a differential computation circuitry to differentiate a signal according to a voltage between electrodes, and to generate a differential signal. An integral computation circuitry integrates a differential signal which increases and decreases as the differential signal increases and decreases with respect to time, and generates an integral signal. The control circuitry generates a control signal, and an electric power supply circuitry supplies electric power to a discharge lamp based on the control signal.