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FrozenGate by Avery

OPEN SOURCE: "CC-Boost" - 2.4 Amp boost driver - RC1

Re: OPEN SOURCE: New Boost Drive, 2.4A capable from one cell, tested and working

paul1598419 said:
Yeah, I get that, but increasing the inductive reactance of this part of the circuit isn't going to limit your noise at the output, from what I can see. All boost PWM circuits like this one have an inductor to limit the current of the output, but as your noise is part and parcel of the FET's output and this is a function of the output from the feedback circuit and the current sensing device I don't get the increase as reducing the noise by its increase.
Click to expand...

No harshness intended by this response :) but you're wrong. Just Google pretty much any guide to selecting an inductor for any type of switching regulator and you'll see, unequivocally, that inductance has more impact on output ripple than anything else, including capacitor selection.
 





Re: OPEN SOURCE: New Boost Drive, 2.4A capable from one cell, tested and working

Exactly. A bigger inductor slows everything down and gives the feedback/compensation more time to
react.
 
Re: OPEN SOURCE: New Boost Drive, 2.4A capable from one cell, tested and working

Just reflowed two of the V14 boards. They work great. No surprise there though, it's the scoping that matters. I'm going to have to place another digikey order, but by mid next week I should be able to get two drivers to ARG for scoping.

Going to send a 2.4A and a 750mA.

On a separate driver project I'm having good results with alternatives to the ZXCT1009. So once we've got the ripple fixed here, upgrading the ZXCT1009 for something else will be the last task.
 
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Re: OPEN SOURCE: New Boost Drive, 2.4A capable from one cell, tested and working

Sounds good to me :)

Are there any parts that I should add to my next digikey order in case the new inductor/cap combo doesn't achieve the desired results?
 
Re: OPEN SOURCE: New Boost Drive, 2.4A capable from one cell, tested and working

ARG said:
Sounds good to me :)

Are there any parts that I should add to my next digikey order in case the new inductor/cap combo doesn't achieve the desired results?
Click to expand...

Not really.

If the new combo doesn't achieve the desired results, I suspect the change will need to be further layout revision, rather than part swaps.
 
Re: OPEN SOURCE: New Boost Drive, 2.4A capable from one cell, tested and working

Finally got a digikey order.

I've reflowed:
- V14 - 2.4A
- V14 - 850 mA
- V15 - 2.4A

I'll ship them off for testing this weekend. I was hoping to hit 750mA instead of 850mA, but then I checked the ZXCT datasheet, and 750mA would put us under the minimum VSENSE voltage drop of 50mV. So we're stuck with 850mA for now, but in a future revision I'm going to up the sense resistance (just slightly) to get it into the 50mV drop range for currents above 600mA, and then add a trimmer to set the range at something like 600mA to 2.4A, all of which will be within the ZXCT's operating range.
 
Re: OPEN SOURCE: New Boost Drive, 2.4A capable from one cell, tested and working

Double-posting intentionally, so subscribed users get notifications.

V14 and V15 drivers in the mail for testing.

I did a quick build with the V15 at 2.2A, a 9mm Nichia diode, and the MS-ENVY host - just to see how practical the driver is real-world. It operates fantastically, and was easy to work with. The IC does need to be heatsinked for long duty cycles, but once done, it runs without issue. I'm liking where this is at, and I have high hopes for V14 and V15. Fingers crossed. Lets see how they scope.

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Re: OPEN SOURCE: New Boost Drive, 2.4A capable from one cell, tested and working

V14 - 2.3A
Test 1:
ectmMJR.png

Test 2:
Dh1lTra.png

Test 3: [Time/Div changed]
sNZUo1C.png




V15 - 2.3A
Test 1:
Gi2Espz.png

Test 2:
Z04jGmz.png

Test 3:
5ZM8FLO.png


I'll test the last one in a bit, got to find some more diodes to make a 6V load :)
 
Re: OPEN SOURCE: New Boost Drive, 2.4A capable from one cell, tested and working

I cant quite tell, but it looks like that initial tiny "spike" (if you can even call it that) doesn't hardly exceed the set current. Is that correct?
 
Re: OPEN SOURCE: New Boost Drive, 2.4A capable from one cell, tested and working

It's a chart of voltage in the graphs, but you're right. The spike doesn't exceed the stabilized voltage.

LQctXCm.png
 
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Re: OPEN SOURCE: New Boost Drive, 2.4A capable from one cell, tested and working

Ah, ok. Is there a way for you check current as well? I assume there is, but im certainly no expert on oscilloscopes :whistle:
 
Re: OPEN SOURCE: New Boost Drive, 2.4A capable from one cell, tested and working

crazyspaz said:
Ah, ok. Is there a way for you check current as well? I assume there is, but im certainly no expert on oscilloscopes :whistle:
Click to expand...

There is, by putting a a small value resistor in series with the diodes and scoping across the resistor. I don't have one of suitable value/power rating; I'll put one in my next digikey order :)
 
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Re: OPEN SOURCE: New Boost Drive, 2.4A capable from one cell, tested and working

That's all exactly what we wanted to see.

V15 is prettier, but it does come at the cost of size. I think V14 is the winner on balance.
 
Re: OPEN SOURCE: New Boost Drive, 2.4A capable from one cell, tested and working

Was there a zip file for v14?

There is some +rep coming around. :beer:
 
Re: OPEN SOURCE: New Boost Drive, 2.4A capable from one cell, tested and working

V14 - 850mA
Test 1:
cbES7mO.png

Test 2:
I8VWSGB.png

Test 3: [Time/Div changed]
zeItHrx.png
 
Re: OPEN SOURCE: New Boost Drive, 2.4A capable from one cell, tested and working

Thanks ARG. And VERY interesting. That dirtiness on the version set to blu-ray currents vindicates a theory I had over here (http://laserpointerforums.com/f38/first-casualty-dead-bdr-209-diode-90121.html) about FlexDrives / MicroBoost drives being the cause of deaths on 16x diodes.

Compare V14 driving 5V at 2,300 mA (445nm multi-mode diode sim)
ectmMJR.png


...to V14 driving 6.5V at 850mA (16x blu-ray diode sim), and remember, these divisions are 2V instead of 1V as in the previous test, so this is a harsh ripple that looks to be roughly 5x the ripple in the previous chart:
zeItHrx.png


Same driver, except that I actually used a slightly better inductor on the V14 destined for the blu-ray. Even though driving the 16x blu-ray at 850 mA would represent less than half the output wattage of driving a 445nm at 2.3A (so common sense might cause you to think it should produce better results), the output is much worse - it's dirty and dangerous. We've got a phenomenally clean output on the 445nm 2.3A sim, and a fairly bad output on the 16x 850mA blu-ray sim.

It's not all about absolute wattage in/out. In this case, it's really about the differential between input/output voltage, and the impact that has on duty cycle of the regulator (which in turn has a substantial impact on ripple).

With this driver now in a great state for 445s, it's an easy fix to set things straight for blu-rays. The solution is to use the same driver topology (and probably the exact same PCBs), but use an inductor that has been intelligently selected depending on what we're boosting for. 850mA doesn't require a huge saturation current, which means we can select an inductor with much higher inductance for drivers destined for blu-rays. In other words:
- For 445 boosting: Moderate inductance, higher saturation current (basically, the inductor used in the tests above is A-OK)
- For blu-ray boosting: Higher inductance, relatively lower saturation current (like perhaps 587-2956-1-ND - 47UH 1.15A SMD)
 
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