25w LED pulse circuit design?

Thread Starter

Nickski

Joined Apr 13, 2024
2
Hi All, newbs here. I have general circuitry knowledge, mostly tinkering with Arduino. I bought a 25w LED chip, and I would like to flash the LED up to 1000 pulses per second or less. Attached is the data sheet. Is there an off-the-shelf solution for this or could I use an Arduino and fast capacitor and a fast mosfet to achieve this? Any help or schematic I would greatly appreciate.
 

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LowQCab

Joined Nov 6, 2012
4,290
What amount of Current do You expect to use ?
( ~5-Amps will be absolutely blinding,
complete with floating-blue-dots and stars,
at anything closer than around ~10-feet, ( ~3-Meters )).

What is the On-Time vs the Off-Time, and does this need to be adjustable ?
Or, do You want a fixed-ON-Pulse-Length with adjustable Off-Time in between flashes ?

Why do You need ~1000Hz as a maximum-Rate ?

What will be the lowest-Frequency desired ?

Have You worked-out the necessary Heat-Sinking that may be required ?

Will this project be Mains-Powered or Battery-Powered ?

If Battery-Powered, how much run-time do You expect ?
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Thread Starter

Nickski

Joined Apr 13, 2024
2
Thank you for your Response LowQCab.

What amount of Current do You expect to use ? 3-5 Amps - thank you for pointing out the safety, this was also a question I had but wasn't sure this was the right forum. I have IR LASER safety glasses as I am also working with 905nm lasers . Is this just because of the wattage or is this because of the wavelength, or both? I am testing LEDs as a cheaper option.

( ~5-Amps will be absolutely blinding,
complete with floating-blue-dots and stars,
at anything closer than around ~10-feet, ( ~3-Meters )).


What is the On-Time vs the Off-Time, and does this need to be adjustable ? yes, I will need to be able to do multiple different patterns, so yes needs to be adjustable.
Or, do You want a fixed-ON-Pulse-Length with adjustable Off-Time in between flashes ? no

Why do You need ~1000Hz as a maximum-Rate ? it actually needs to be adjustable between 100 and 9000hz

What will be the lowest-Frequency desired ? see above

Have You worked-out the necessary Heat-Sinking that may be required ? yes, got that covered

Will this project be Mains-Powered or Battery-Powered ? automotive application so 12v

If Battery-Powered, how much run-time do You expect ? NA
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LowQCab

Joined Nov 6, 2012
4,290
"" What is the On-Time vs the Off-Time, and does this need to be adjustable ?
yes, I will need to be able to do multiple different patterns, so yes needs to be adjustable. ""
Add to this ..........
"" it actually needs to be adjustable between 100 and 9000hz ""
Any Frequency above roughly ~40-Hz is not noticeable to the average Human-Eye.
This means that there must be some undisclosed reasoning for using this Frequency-range,
what would that purpose be ?

This would also seem to indicate that You will need to employ a Micro-Controller to
create what You call "different-patterns", ( whatever that might mean ).

My first suggestion would be to purchase a 5-Volt, ~10-Amp, Buck-Regulator.
The Buck-Regulator will then provide Power to a FET-Gate-Driver, which will switch a heavy-duty FET.

The Buck Regulator will also power your choice of Micro-Controller,
which will then drive the FET-Gate-Driver-Input.

~9000-Hz doesn't make any sense in an "Automotive" application, as You have specified,
unless maybe if it's for a DIY-Timing-Light-Strobe.
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dovo

Joined Dec 12, 2019
72
The LED is specified for 9V, 5000 mA at 1/10 duty cycle. That is 4.5 watts average power. The maximum pulse width is 100 us. Your plan to pulse 1000 Hz with 100 us width works and bumps up against the maximums.

Yes, it can be done with a 9V power supply and N-channel MOSFET. I would design for a current rise time of 1us to keep transistor power dissipation down. I can post a circuit if you'd like.
 

dovo

Joined Dec 12, 2019
72
Here is an LED driver circuit.
9V
500 mA
100 us pulse width
1000 pulse repetition rate
3.3V gate drive

A TO-220 case logic level MOSFET is used so a 3.3V Arduino can drive it. Other logic level MOSFETs can be used as long as their gate charge is 100 nC or less and the Vgs is 2V or less. Check the datasheet. The 100 ohm gate resistor helps keep the MOSFET from breaking into an HF oscillation. The 1000 uF supplies the 0.5A pulse current and discharges 50 mV + 0.5 x ESR during the 100 us current pulse.

C = i/(dv/dt)
dv = (i/C)dt = (0.5A/1000uF) x 100 us = 50 mV


1715829287983.png

IRLZ530 datasheet https://mm.digikey.com/Volume0/opasdata/d220001/medias/docus/1103/IRL530,SiHL530.pdf
 

dovo

Joined Dec 12, 2019
72
Here is an LED driver circuit.
9V
500 mA
100 us pulse width
1000 pulse repetition rate
3.3V gate drive

A TO-220 case logic level MOSFET is used so a 3.3V Arduino can drive it. Other logic level MOSFETs can be used as long as their gate charge is 100 nC or less and the Vgs is 2V or less. Check the datasheet. The 100 ohm gate resistor helps keep the MOSFET from breaking into an HF oscillation. The 1000 uF supplies the 0.5A pulse current and discharges 50 mV + 0.5 x ESR during the 100 us current pulse.

C = i/(dv/dt)
dv = (i/C)dt = (0.5A/1000uF) x 100 us = 50 mV


View attachment 322418

IRLZ530 datasheet https://mm.digikey.com/Volume0/opasdata/d220001/medias/docus/1103/IRL530,SiHL530.pdf
MOSFET power dissipation is 5 mW and a heatsink is not needed even with a small SMD device.

Average current is 50 mA and even a 9V battery will pulse the LED for a few hours.

The 10k pulldown resistor ensures the MOSFET is OFF when the Arduino is powered down.

Capacitor RMS current is 170 mA.

Parts List
IRL530
100 ohm (47 to 220 ohms is fine)
10k
1000 uF (or whatever you have on hand)
 

LowQCab

Joined Nov 6, 2012
4,290
No "~100us Pulse-Width has been specified by the TS.
There are many possible circumstances in which that FET will not survive more than a few seconds.

Please wait until the TS has fully specified exactly what he wants and expects.
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MisterBill2

Joined Jan 23, 2018
19,398
The challenge with any transistor switch will be during switch on period and the switching off time period, when it is in the linear mode and dissipating power. so for a maximum current of 5 amps use at least a 10 amp rated device with an adequate heat sink. And use a driver circuit able to switch it rapidly.
 
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