Depressing Start-Up Current Overshoot for a Laser Headlight Driver in High-Temperature and Forward Voltage Drift Conditions

High-optical-output-power laser diodes (HOO-PLDs) are a new option for the next-generation vehicle headlights. This paper develops a laser headlight driver (LHD) combining a safety standard circuit, dc-dc converter, and feedback controller. The dc-dc converter topology is a two-switch two-diode buck-boost converter (TSTDBBC), which could be operated in both step-up or step-down conversion modes for variable battery voltage input to the LHD, enabling the driving voltage and current of the HOOPLD to be obtained from the TSTDBBC output. Because the operating ambient temperature (OAT) can cause forward voltage drift in the HOOPLD, the feedback controller could be used to stabilize the driving current to cope with forward voltage drift. Moreover, in the start-up phase, a current overshoot occurs when the TSTDBBC operation changes from the constant-voltage output mode to the constant-current output mode. This can be further aggravated when HOOPLDs operate under a high OAT. Therefore, proportional switching proportional-integral control technology was applied to the current-feedback controller to depress the current overshoot, enabling the driving current of the HOOPLDs to be maintained at the rated specification to ensure operating lifespan. Complete design procedures are presented. Simulations and experimental results validate that the proposed control technology is effective for solving the ignition problem.