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1W potted LED Driver - OK for A140?

jupiter8

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I picked up one of these today and intend to use it to drive an A-140 diode. I'll test it carefully with a dummy load and make sure I run it with a regulated psu, anyone see any potential issues with this driver for LDs?

High power LED Driver - AA0596
 
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LSRFAQ

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I picked up one of these today and intend to use it to drive an A-140 diode. I'll test it carefully with a dummy load and make sure I run it with a regulated psu, anyone see any potential issues with this driver for LDs?

High power LED Driver - AA0596
Yes, I see a issue, LEDs are tough and take all sorts of ESD and Spikes and Pulses that Laser Diodes can't. That is a switching power supply, they rarely have output filtering beyond a minimum , and generate PULSES and inductive SPIKES.
At a minimum you should add some low pass filtering, or possibly a Lasorb.

I'd think twice before I used ANY switching led driver with a laser diode.

Steve
 

RDTech

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I picked up one of these today and intend to use it to drive an A-140 diode. I'll test it carefully with a dummy load and make sure I run it with a regulated psu, anyone see any potential issues with this driver for LDs?

High power LED Driver - AA0596
Filtering it from spikes may be possible with a small value Zener diode of 5.1V. I can not remember the drop voltage of these new 445nm devices. Certainly, Like the RECOM RCD series of adjustable LED drivers, which I have used for 405nm devices, they have a recomended filtering circuit at bottom of datasheet, but I do agree, spikes are bad for most LD's. The RECOM RCD-24-XXX can drive LD's, they also have a PWM as well as analog dimming capability. FYI
 

jupiter8

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Thanks LSRFAQ, good info. What did you mean by switching? This is a continuous adjust through the pot. no? I don't know what you mean by switching... How about bridging the output with a capacitor to absorb spikes? Perhaps 100nF ceramic or something like that.
 

LSRFAQ

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Thanks LSRFAQ, good info. What did you mean by switching? This is a continuous adjust through the pot. no? I don't know what you mean by switching... How about bridging the output with a capacitor to absorb spikes? Perhaps 100nF ceramic or something like that.

One, a switching power supply uses pulse width modulation of stored energy in a inductor to create a controlled current. For most LED drivers, they output a series of pulses at 100 Khz or so. The inductor "rings" like a bell on each pulse, resulting in a series of spikes at the leading or trailing edge of the pulse.

LEDs dont care, they have a big thick chip that can take some abuse. A LD on the other hand is a thin chip with very low capacitance and will try to follow the pulses faster then say a zener diode or simple cap can follow. The faster LD will in most cases, sacrifice itself to protect the zener and/or cap. :(

This is opposed to a linear driver that turns unused current into heat by acting as a variable resistor.

Switchers are nearly 90% efficient, that is why they are used. That and the fact thet they are often compact with no cooling needed. They have the downside that they are spikey in the cheaper models used for LEDs.

A Lasorb is a special ultrafast device to protect a diode against spikes.

LASORB - ESD absorber for laser diodes

Compared to the cost of another diode, a Lasorb is cheap insurance and a 100,000 times faster then a Zener diode. Lasorbs were between 6 and 9 USD in the PL group buy. I'm sure francesco is going to have another GB in the next week or two. A lasorb will switch in about 4 nanoseconds. A zener may need at least a microsecond to a millisecond. A 405 nm Lasorb works just fine for 445.

I'd start with a Lasorb across the diode for one. Two, I would use a LC lowpass filter to filter out the spikes if there. You really need a oscilloscope and a dummy diode to test with. make sure the lasorb is within a few cm of the diode.

Values in this pic are a guess. Without looking at the output of your module on a scope with a dummy load, I can't tell you for sure. The problem is I'm half a planet away!

I have no idea what the poles and zeros are for your driver (meaning is it stable, will it oscillate with a reactive load?) So use what is attached with a measure of concern. If this is your only 445, find a known good linear driver designed for laser diodes. ie Flexmod, Thorlabs, Meredith Instruments etc.

See attached, But I would find another driver, a linear designed for the purpose.

Steve
 

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Asherz

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Basically you could have just got hold of a flexdrive, groove driver or a microboost. That seems like a lot of hassle to create a makeshift solution for a problem that doesnt exist if you order the drivers listed.
 

jupiter8

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Hmmm... damn. I won't be connecting this to my A140. I'm going to return it and get my money back. Thanks LSRFAQ for your time explaining this, I didn't realise it was using PWM to control the output current. You live and you learn.
Cheers.
 

jupiter8

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Returned this today and got a full refund, thank goodness. Thanks guys for your wisdom and willingness to share it. This grasshopper is learning fast. I'll be putting the cash towards a good linear, constant current driver for the A140 diode, but in the mean time I have some components in the workshop and will put together a couple of good DDL drivers, circuit diagram courtesy of HIMNL9.

I'd really like to get hold of a drlava flexmod driver, but I'm sure you know the situation, out of stock until the new model comes online...

If anyone has a good driver lying around which they'd like to sell, please pm me. I'm definitely interested.
 

Seoul_lasers

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Hmmm... damn. I won't be connecting this to my A140. I'm going to return it and get my money back. Thanks LSRFAQ for your time explaining this, I didn't realise it was using PWM to control the output current. You live and you learn.
Cheers.
I blew my diode without evening thinking that my OEM laser driver would be a problem. These 445nm diodes seem to be extremely current hungry but still very sensitive.
The driver couldn't handle the load and more than likely spiked.


RIP, my poor 445nm diode.

Maybe I'll have a funeral tonight for it.
 

Seoul_lasers

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Returned this today and got a full refund, thank goodness. Thanks guys for your wisdom and willingness to share it. This grasshopper is learning fast. I'll be putting the cash towards a good linear, constant current driver for the A140 diode, but in the mean time I have some components in the workshop and will put together a couple of good DDL drivers, circuit diagram courtesy of HIMNL9.

I'd really like to get hold of a drlava flexmod driver, but I'm sure you know the situation, out of stock until the new model comes online...

If anyone has a good driver lying around which they'd like to sell, please pm me. I'm definitely interested.
Let me know too. I really am looking forward to a new driver.
 




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