I'm trying to drive LEDs for the purposes of a strobe light. I'm planning on driving the LEDs at ~60 fps, and for ~100 us pulses to provide very sharp strobe images.
If the pulses are very short and infrequent, you end up needing extremely bright LEDs to make up for how infrequent the LEDs are "on" (same as if you were PWM'ing them with a 0.1" duty cycle or so). The typical solution is to overdrive the LEDs by a large factor -- I've read papers about putting 1000x the rated current through an LED, which won't damage the LED as long as it cools for sufficiently long times.
To accomplish this goal, I put together this circuit:
The LEDs are connected via a connector at
P4 (labelled "LED_1"). I currently have 3x White LEDs with a forward voltage of 3.5 volts placed there.
I would expect to see (12 Volts - 3*3.5 Volts) = 1.5 Volts across the resistor
R5. With a resistance of 0.02 Ohms, I would expect to see 75 Amps placed through the LED -- however, while running the circuit, I find that it's only about 1.3 Amps, with a voltage of 150 mV or so placed across the resistor.
I'm using a FET Driver to drive the MOSFET, so it doesn't seem to be an issue of it not being fully turned on.
Can anyone help me understand why this is?