Halogen discharge lamp for vehicle - has protection circuit for start-up current and for failing battery supply

摘要

A control circuit is provided for monitoring the state of the discharge current through the lamp (10) and operates current limiting circuits (11, 16) to limit the current through the FET in the DC amplifier (6). The control is via pulse-width modulation (PWM) and with the voltage- and current limiting. The discharge monitoring circuit provides a correction signal which is superimposed on the control signal. The DC amplifier includes a chopper to feed a varying signal to the DC/AC converter (7) which powers the lamp. The correction signal is also chopped into a saw-tooth pattern to fit over the drive signal. The system provides rapid starting if the lamp is still warm, and protection against overcurrent if the battery supply reduces. ADVANTAGE - Improved protection for discharge lamp; self correcting.