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
