LASTEC Delhi in a joint collaborative activity with LEOS, Bangalore is developing a space qualified diode array
pumped Nd:YAG laser transmitter delivering 30 mJ @ 10 pps of 10 ns duration. For space applications laser diodes are
preferred because of their excellent reliability with lifetimes exceeding 100,000 hours. However, they are extremely
sensitive to electro-static discharge, excessive current levels, and current spikes and transients. Small variations in bias
voltage may produce large fluctuations in the current causing instability and damage to the device. Hence instead of the
traditional power supplies a current controlled laser diode driver is required. This paper presents the design of a Q-CW
laser diode driver based on closed loop current regulator, capable of driving 24 QCW laser diode bars each with 75W
peak power at 70 A. The driver can generate up to 100 Amp peak current and 200μsec pulse width operating at 10 Hz.
The current source design includes special circuits for low noise operation, slow turn-on and turn-off, circuits for over
voltage and transient current protection; and good regulation. Space qualified and radiation hardened components are
required to be used to sustain stringent space environment requirements during mission life of two years.