The high-power laser diode driver (HPLDD) that combines the buck-boost converter (BBC) and feedback controllers was designed and implemented for the vehicle headlights. The buck-boost converter could be operated in all conversion modes including step-up, step-down, and step-up-down, with variable battery voltages input to the HPLDD. Moreover, the feedback controllers composed of a voltage-loop controller (VLC) and a current-loop controller (CLC) to control the BBC's output voltage and current to drive high-power laser diodes (HPLDs). In the start-up phase, when the BBC output side is operated from the constant-voltage mode and changed to the constant-current mode, a current overshoot occurs, which can damage the high-power laser diodes. This paper proposed a control method, the proportional-switching-proportional-integral control technology, can be used to the CLC to reduce the start-up current overshoot.