Electronics > Projects, Designs, and Technical Stuff

Ultra Short, Ultra Fast LED Flash

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ogden:

--- Quote from: Marco on March 07, 2019, 12:14:47 pm ---a lot of LEDS&resistors in parallel

--- End quote ---

No, no, no. Better use (inductive switching) converter to pump energy into (flash) capacitor (48V or even 100V), to *avoid* lot of LEDs in parallel, but use single or few (long) strings. White balance using programmable voltage.

Marco:
He only wants 500 ns pulse width. Avalanche transistors, massive overvoltage to overcome inductance, worrying about a little trace length are all overkill.

Meanwhile low voltage has the advantage it can't kill.

Zero999:
One thing to note is the LED(s) should have a reverse parallel diode. I didn't include one in my schematic, because the LEDs I tested all have one built-in, which is very common for high current LEDs.

Seekonk:

--- Quote from: ogden on March 06, 2019, 02:37:06 pm ---
--- Quote from: Siwastaja on March 06, 2019, 01:28:04 pm ---to maintain some current regulation, you need to drop some meaningful voltage over the resistor, let's say at least 20-30% of the total supply voltage.

--- End quote ---

20-30% of waste power? :) Please don't... Somebody may take your joke as an advise. Example: Osram 24V strips uses 7 white LED's in series.

--- End quote ---

Resistors, we don't need no stinking resistors.  I hit the LED right from the FET at about four times the rated voltage.

schmitt trigger:

--- Quote from: JAndrew on March 05, 2019, 11:06:50 pm ---

Jay

--- End quote ---

Doc Edgerton himself would be proud of this photo

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