FAST, High Energy Pulser
This circuit is designed to provide very fast, high current pulses into laser diodes and LEDs. It can be modified to drive ultrasonic transducers as well. The light pulses from the laser are typically used for range-finder applications as well as fluorescent excitation sources. Some blue LED's from Nichia will generate UV energy when overdriven with short, high-current pulses.
The circuit is designed around a transistor designed for this application: the DE150 from Directed Energy, Inc (www.directedenergy.com). The circuit works as follows: the 78S40 forms a basic 15V to 100V flyback DC to DC converter. The 100 volts is then used to charge the four, 1000pf caps connected to the source pins of Q1. When Q1 is turned on, the caps discharge through the laser diode dissipating 1/2*C*V^2 of energy. JP1 can be used as a current monitor. Multiply the observed voltage by four to determine the current through the diode.
Careful attention to layout will yield the best turn-on times. Keep the leads short and the traces fat. For more information on designs of this type, we strongly recommend a visit to the DEI site referenced above.