High Power LED Stroboscope Analog section Design Problem

Hello Guys

I created nearly the same topic in microcontroller section of this forum , but not exactly the same question here ...
the other topic Here
If its illegal,please delete it

I'm making a high Power LED stroboscope that uses 2*10 watt LEDs Driven by micro controller with digitally controllable frequency and duty percent .
But my problem is :
for making a high speed rotary device look "still" , the duty percent should be lowered below 2% ( as experience ). and as you know with this low Duty the light intensity is so weak .

I know that with much more current the brightness can be multiplied , but with a 10-12 volt forward voltage LED the power supply should be multiplied by a factor of 50 ( 2% Duty) , which means 500-600 volts!, and i cant supply such a voltage nor LED can handle even 20% of it!( is it true at all?)

( I get about 5 mA with LED directly connected to a 20 A - 12V Computer power supply without any current limiting equipment , while strobing with 60Hz,1% Duty ) - and i cant even think about high voltage transformer circuits like the one used in crt TVs - and i couldn't find any step up regulator to do the job

Is there a specific type of circuit to do the job with a "high current capable but low voltage power supply" ?

I asked in uController section about a design that can be dynamically change this pumping current ( as duty percent incremented , the current lowered ) - but any help with analog design of such a circuit appreciated
thank you very much and sorry for my poor english - you are the best

Have a look at this link,
Interesting Electronic Schematics and Circuits - Novotill
and other projects,
constant_duty_cycle_LED_stroboscope
An LED Stroboscope
I think, brightness is not big problem if you choose right LEDs. (SUPER BRIGHT AND SUITABLE FOR MULIPLEXING)

You're writing a lot about special power supplies, but I think, the first point is to clarify the maximum ratings of high power LEDs in pulse operation. You'll find specifications of permissible current versus pulse duration and duty cycle in many data sheets. You can expect lower pulse overload capability with highest power LEDs, so it's most likely suggested to use multiple medium power LEDs or multi-chip lamps. You'll also find special LEDs specified for flash and strobe light applications, e.g. from OSRAM Opto Semiconductors|index

In any case, you won't be allowed to exceed e.g. factor 2 or 5 of rated continuous current, even for shortest pulses. The forward voltage will increase by a lower factor. In so far the 600V etc. considerations ar off-topic.

For very short pulses and high power, true Xenon flash lamps are without competition, however. Furthermore, circuits for a low power (a few watts) flash lamp strobe are very simple.

FvM said:

You're writing a lot about special power supplies, but I think, the first point is to clarify the maximum ratings of high power LEDs in pulse operation. You'll find specifications of permissible current versus pulse duration and duty cycle in many data sheets. You can expect lower pulse overload capability with highest power LEDs, so it's most likely suggested to use multiple medium power LEDs or multi-chip lamps. You'll also find special LEDs specified for flash and strobe light applications, e.g. from OSRAM Opto Semiconductors|index

In any case, you won't be allowed to exceed e.g. factor 2 or 5 of rated continuous current, even for shortest pulses. The forward voltage will increase by a lower factor. In so far the 600V etc. considerations ar off-topic.

For very short pulses and high power, true Xenon flash lamps are without competition, however. Furthermore, circuits for a low power (a few watts) flash lamp strobe are very simple.

Click to expand...

Thanks for your useful advises
First of all i use Chinese LED type and unfortunately i don't have any other non-Chinese choice here and these manufacturers are so weak in documenting their products .

But i used 1 watt LED with 3.5 volt FV and 200-300mA nominal Current . the problem is i get only about 7 mA consumption in 1% duty without use of any current limiting resitor - my power supply is 12 Volt regulated capable of driving 20A on each 12Volt rails. and Even a simple 5mm white LED is not consumes more than 4ma in here.

so is there any other option ?

I'm using a N-channel power mosfet to drive these LEDs with logic output of uC ( Panasonic K2129 about 3A continuous and 6A in pulse current absolute rating with 40ns rising time)

But i used 1 watt LED with 3.5 volt FV and 200-300mA nominal Current . the problem is i get only about 7 mA consumption in 1% duty without use of any current limiting resitor - my power supply is 12 Volt regulated capable of driving 20A on each 12Volt rails.

Click to expand...

The results don't sound plausible. Most likely, your switch transistor is involving current limiting.

Typically, a white power LED pulsed with 12 V would draw 5 to 10 A pulse current (50 - 100 mA average at 1% duty cycle) and be immediately blown.

FvM said:

The results don't sound plausible. Most likely, your switch transistor is involving current limiting.

Typically, a white power LED pulsed with 12 V would draw 5 to 10 A pulse current (50 - 100 mA average at 1% duty cycle) and be immediately blown.

Click to expand...

thank you for reply
As i mentioned before, I'm using a N-channel power mosfet to drive these LEDs with logic output of uC ( Panasonic K2129 about 3A continuous and 6A in pulse current absolute rating)
It has 40ns rising time and Gate current is adjusted to make it beyond fully ON minimum current

Is the MOSFET the source of problem ?

Hard to decide without a measurement showing the actual current waveform.