FREE DIY open source BOOST driver!!! Tested & working!!

I did some tests on the ben boost with 22uF caps. (real 22uF )

I tested the rectangular and the round board.

I made videos of the waveform cuz the screen of the Digital Scope is small and you cannot see the whole form in details without scrolling.

The first two videos are the startup and the ripple current with 1x probe on the rectangular board.

The 3rd video is ripple current on round board with contacts on the bottom. I forgot to take a video of the startup but it's similar to the rectangular (with some more oscillations)

The rectangular board is showing around 30mA of ripple current without oscillations which is pretty good with the 22uF Caps.

It has a little startup spike with some oscillations that could be a problem for the more sensitive laser diodes like the blurays.

The circle board is showing oscillations in the 50mA range which is bad. This might be a design flaw and oscillations on startup

I have set both to approximately 1.25A of output current.


I didn't have time to do more tests... you will have to excuse the TV noise. My gf was watching some comedy shows.

If any questions I will answer tomorrow cuz I am going to bed now good night folks :beer:

I am surprised no one replied

Soz I was speachless.. o_0 I dont really know what to say because I dont really understand how to read that. I take it the ripple is the little spikes and the oscilation is the overall wave? I see the wave with the round boards looked horible with some bad spikes. I still havent found out if I have 2.2 or 22uf caps. Were those the boards I sent you?

I was going to but I can only get on from my phone right now and I didnt feel like typing a big reply from this little keyboard!

I'll try to keep this short. The ripple doesn't seem very bad at all. On any blu ray you would be using less than half that current so you can expect even less ripple. On the rect. spikes were only ~15ma above the output current and 1.25A is basically maxed out do I think that is very good.

Also I couldn't tell if there was even a start up spike at all. You moved it up so fast I couldn't count the rows though so I may be wrong. I didn't see any obvious big spikes though.

The round board does have a weird wave at a lower freq than the ripple. Do you have a second you could try too? If this is on more than one then it is probably something with the layout. Even still, 50ma at this current isn't extremely bad. It goes between about 1.225A and 1.275A I guess.

I'll be doing my own testing soon enough. I'll try a few different cap combinations and see what works out best.

Keeping it short didn't work out so well haha

Yeah I think it's pretty acceptable. At lower currents it will be better so I think with 22uF caps this driver is a go.

The spike is pretty small like 10mA or so. That won't be a problem indeed.

Kent, yes this is the round board you sent me. tsteele93 sent me some components and I assembled one rectangular and one round board but I put my own 22uF caps which are real 22uF caps.

I think the round board is behaving like that because of the layout.

Ben, you can pause the video at any time :beer:

I tried pausing it! It jumps up really fast and a couldn't keep track of it. If I was at my computer I could get it playing in slow mo or something and figure it out. I just wasn't sure if that entire piece shown in the video was supposed to be a long current spike. 10ma is great, won't cause trouble with any diode.

I'll work on the round one later, but for now it will do.

benmwv said:

I tried pausing it! It jumps up really fast and a couldn't keep track of it. If I was at my computer I could get it playing in slow mo or something and figure it out. I just wasn't sure if that entire piece shown in the video was supposed to be a long current spike. 10ma is great, won't cause trouble with any diode.

I'll work on the round one later, but for now it will do.

Click to expand...

Yeah, you will be able to see it on the PC better. The video is showing the startup sequence from 0 to 1.25A :beer:

Yeah, I was operating under the "better to keep quiet and have people assume you are stupid than to open your mouth and remove all doubt."

I really wasn't able to read it. I have a hard enough time understanding my own scope!

MY problem is with all the heatsinking in the world benboost at 1.25A will only run for 30 seconds before thermal shutdown! So why even try to use that setting? You use 2 of them at the 955 setting and your going to need more than 1 18650 batt.

I don't know maybe small PHR builds in the 120mA to a 6x 150mA that will be my next venture I guess.

I'll agree that we need a better thermal solution here... Any word on the new designed boards ben with the extra copper?

Latest test confirmed that a capacitor between Vout and FB is going to decrease the output ripple current BUT!!! at certain voltage levels IT WILL CAUSE OSCILLATIONS at the output no matter the value of capacitance...

This capacitor should be removed in all cases to ensure the stability of the driver at all voltage levels. Better to have a little more ripple than oscillations causing the driver to ring and heat up pretty quickly. Also lowering the the efficiency drastically!

This is also tested on my driver! Do not put caps between Vout and FB (LD+ and LD-)

so your saying to remove the cap on the LD out?

Oh have ya seen this yet?


Clip_3 by Kizdawg, on Flickr

yes the cap between LD+ and LD-.

what exactly is that? :thinking:

Hmm. What different setups did you try? You mention "certain voltage levels" are you talking about input voltage or output voltage? Can I get some specifics?

benmwv said:

Hmm. What different setups did you try? You mention "certain voltage levels" are you talking about input voltage or output voltage? Can I get some specifics?

Click to expand...

When varying the input voltage and the diodes used on the test load. At some point I can't remember exact numbers but here is an example

when input voltage is 4.2V and 4 diodes at 1.25A output is good. Low ripple no oscillations. Lower the input voltage at some point the driver starts to oscillate turn back the input at the previous voltage - driver steady. Pass a specific voltage downwards let's say it oscillated at 3.7V. We turn to 3.5V driver steady again. Note: I can't remember exact numbers here.

Another example driver steady at input voltage 3.7V and 4 diodes on test load. We move to 5 diodes - driver gets oscillations again .. we rise or lower the input voltage oscillations are gone at some point and appear on another.

I am not saying the driver can't handle the output. If the cap is removed the driver will be working as it should at the same voltage levels on which oscillations appeared with the cap. So it's the cap causing them.

I tried values 100nF, 2.2uF, 10uF and 22uF. All show the oscillations on different positions of the input and output values. With 100nF I got the fewest positions on which it oscillates with 22uF it gets lots of it.

foulmist said:

When varying the input voltage and the diodes used on the test load. At some point I can't remember exact numbers but here is an example

when input voltage is 4.2V and 4 diodes at 1.25A output is good. Low ripple no oscillations. Lower the input voltage at some point the driver starts to oscillate turn back the input at the previous voltage - driver steady. Pass a specific voltage downwards let's say it oscillated at 3.7V. We turn to 3.5V driver steady again. Note: I can't remember exact numbers here.

Another example driver steady at input voltage 3.7V and 4 diodes on test load. We move to 5 diodes - driver gets oscillations again .. we rise or lower the input voltage oscillations are gone at some point and appear on another.

I am not saying the driver can't handle the output. If the cap is removed the driver will be working as it should at the same voltage levels on which oscillations appeared with the cap. So it's the cap causing them.

I tried values 100nF, 2.2uF, 10uF and 22uF. All show the oscillations on different positions of the input and output values. With 100nF I got the fewest positions on which it oscillates with 22uF it gets lots of it.

Click to expand...

Well then it does sound like its best to remove it. I wonder if it would be possible to get the better ripple but no oscillations by putting a small cap between FB and ground instead of between LD+/-?