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.