A laser diode control system is configured to limit cascade failure of a series of laser diodes. The laser diode series is coupled to an output filter of a power supply. The power supply is a switch-mode power supply and the output filter includes an LC circuit. The laser diode control system includes a protection circuit coupled to the laser diode series. The protection circuit includes a post regulator circuit and an inductor coupled in series to the laser diode series. The post regulator includes a transistor and two amplifiers configured to regulate a voltage across the transistor. In the event of a failure within the laser diode series, a current spike across the laser diode series is prevented by regulating the voltage across resistor.