Hello, I noticed on eBay there are lots of low-cost high power constant current LED drivers.

Say I want to build a high power LED strobe light. I could potentially wire a FET on the output of the constant current driver, and switch the FET rapidly to create a strobe effect on the high power LED. However, I'm worried that the constant current driver will get "confused" by switching - If it doesn't react fast enough, could it send too high of a current into the LED? Thanks!

 

What would be the maximum strobe frequency?

 

You can use an emitter follower CC driver for this task, it's very reliable and can run at high speeds.

I drive a NPN transistor base at 0v and 4.5v (from a PIC digital output pin) then connect it's emitter to ground via the current sense resistor (will see approx 3.9v on resistor) and the LED goes between PSU + (+12v?) and the collector.

The current is set by the value of the emitter resistor. I = 3.9v/R

The circuit is good up to MHz, assuming your transistor is fast enough. It's a great way to pulse high current LEDs for IR comms etc.

 

Elegantly simple. Seems like this would allow you to avoid buying a constant-current driver as the OP was asking about, and just use any old power supply.

 

Hello, I noticed on eBay there are lots of low-cost high power constant current LED drivers.

Say I want to build a high power LED strobe light. I could potentially wire a FET on the output of the constant current driver, and switch the FET rapidly to create a strobe effect on the high power LED. However, I'm worried that the constant current driver will get "confused" by switching - If it doesn't react fast enough, could it send too high of a current into the LED? Thanks!

Some of the cheaper LED drivers are nothing more than a blocking oscillator - the flyback pulse is energy limited by how many lines of flux will fit in the inductor core.

There is a way to bias a separate feedback winding from a C/R network to produce discrete pulses.

 

I would find one with dimmer capability. Then drive the pwm pin. That way the current comes up instead of needing to go down. Or at least limit the current to something safe for the led at the maximum output voltage of the driver until it has time to recover.

 

Elegantly simple. Seems like this would allow you to avoid buying a constant-current driver as the OP was asking about, and just use any old power supply.

Yep, and it's inherently safe because any overcurrent situation causes the transistor to bias off. Making it immune to HF overcurrent spikes etc.

I can't claim originality, it's something I learned from looking at commercial designs when i worked in repair.

 

A big part of wisdom is learning to stand on the shoulders of giants.