Power PCB for Lebowski Controller to be combined with Bobc's processor board

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Power PCB for Lebowski Controller to be combined with Bobc's processor board

Post by Lebowski » Nov 27, 2017 5:51 am

This thread is for a power section that is designed to work with the processor board described in this thread:
viewtopic.php?f=30&t=87104

The basic idea is to have an easy to solder PCB with a connector for Bob's board. The power PCB will have a simple low inductance bus bar setup, 6 TO247 FETs, gate drivers (using IRS 2186) and current sensors (ACS 770 type). The goal is to have the board complete, so with no hand wiring necessary.

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Re: Power PCB for Lebowski Controller to be combined with Bobc's processor board

Post by Lebowski » Nov 27, 2017 6:00 am

The basic setup I have in mind:
DSC02006-800x800.jpg
DSC02006-800x800.jpg (115.24 KiB) Viewed 345 times
On the top left the orange square is PCB copper on both sides of the PCB. Black circles / blue squares are xxx uF and yyy nF caps, one leg going through the PCB soldered to the bottom copper and the other leg bend flat soldered on the top copper. This is also where the main high voltage battery will attach. The idea is to leave the busbar copper exposed so it can be fattened up with solder or copper sheet/wire for high currents.
Below the busbar two rows of 3 FETs, sandwiching a thick (about 6mm or 1/4") aluminium piece attached to cooling. The idea is to follow my low inductance philosophy with the FET angled at 90 degrees:
DSC02007-800x800.jpg
So like this but with the FETs bend over 90 degrees
DSC02007-800x800.jpg (87.77 KiB) Viewed 345 times
Note that I use an aluminium L piece with threaded holes in the top for attaching to controller housing.

From the FETs wiring will go straigth down to the gate drivers (blue squares). Using twisted wires for the gate drive would be best, but I plan to use very close together short parallel wires to minimize inductance

Then finally on the right side are the 3 current sensors and below this (in purple) the connecting to Bob's processor board. Power will go from the busbar, probably via a small RC filter, into Bobs board. This one then generates the 15V for the gate drivers and 5V for the current sensor, so no low voltage supplies are necessary on the power PCB.

I will design the board and build a test version. I am thinking about using 4468's and 150A current sensors, as this works nicely on Izemans controller (built by Animalector). If you guys have different FETs in mind that make sense to me I will order a set of those to determine gate driver resistors (as the gate driver resistors are dependent on the FETs properties - gate charge)

Both Bob's board and the powerboard will have 100V components, though you can of course switch out the FETs for lower voltage / higher current ones. I think with 100V parts it should be usable from 36V upto around 80V (20s fully charged).

I hope to share progress here and to hear you guys suggestions...

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Re: Power PCB for Lebowski Controller to be combined with Bobc's processor board

Post by Lebowski » Dec 01, 2017 4:53 am

3d mockup of lebowski proposed board2.png
3d mockup of lebowski proposed board2.png (81.41 KiB) Viewed 281 times
This is a mockup made by Whereswally606 showing the general idea. Based on the size of the power stage and gate drivers I will need to think what to do about the processor board. I can lay it flat above or below the PCB, or stand it up straight. I'm thinking a few holes drilled in the PCB there will make it possible for a 3D printed plastic piece to act as a processor board holder. This may raise the processor board enough to 'float' above the current sensors...

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Re: Power PCB for Lebowski Controller to be combined with Bobc's processor board

Post by progrock » Dec 03, 2017 7:16 pm

Very cool!... I am looking forward to building one... maybe 2. What kind of volts/amps you think this will handle?

Thanks for the work.... and I guess this isn't so bad being all through hole (I still don't mind soldering some 1206/0805's.... but seeing how there's only a few components that would be different... would likely use the same FETs anyway... I suppose it wouldn't make much of a difference). Though guess we'll see, if/when whereswally makes the SMD version.

BTW, I love the fact that the boards under 100mm X & Y so far.... these will be quite cheap to get from pcbway (or similar)... I htink it's almost insane how cheap a set of 10 <100x100mm boards are... and my last order arrived at my door less than 96 hours after ordering (and 3 x 10 boards, 30 in total, plus DHL shipping was only $35... hard to beat that)

As soon as you got a design somewhat locked down, let us know... I already got a couple of SMD brains coming from you... hopefully can get a couple of bobc's boards ready to test with this.

BTW, those 4468's look pretty damn good for the job... tho if you weren't expecting to go over 100A continious... the 4768's appear to be a pretty solid choice as well (given the 250V is likely unnecessary, but seems to have better RDS among a few other specs... and can even be slightly cheaper, tho pretty close in price to comparison). Though maybe I am missing something... would expect them to be very similar chips... and would think the 4768 could likely handle more amps than it's spec if your running less than half the max Voltage. But I could be wrong.

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Re: Power PCB for Lebowski Controller to be combined with Bobc's processor board

Post by marcos » Dec 04, 2017 8:01 am

Maybe you could benefit from SMD gate resistors. They are big enough so that soldering them is not a problem, and they are inherently very very low inductance, whereas regular TH resistor are inductive unless you specify a non inductive and more expensive part.

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Re: Power PCB for Lebowski Controller to be combined with Bobc's processor board

Post by Lebowski » Dec 04, 2017 9:24 am

I plan to use through hole resistors... I got a gazillion of those from when ST-Ericsson closed down here, makes it easy to experiment and find the correct values for the type of FETs. Another reason is that I do not have too much faith (for high currents) in PCB via's, I always try to switch PCB layer through a component wire. Also, never seen problems from the inductance of normal resistors.

Plus, I gather that if people really want to use SMD they can just lay it flat on the little solder pads that every through hole connection has.

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Re: Power PCB for Lebowski Controller to be combined with Bobc's processor board

Post by Alan B » Dec 04, 2017 12:14 pm

Another FET that is popular lately is the AOT290L.

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Re: Power PCB for Lebowski Controller to be combined with Bobc's processor board

Post by amberwolf » Dec 04, 2017 8:44 pm

Although that one doesn't appear to be available in TO247 package; maybe the legs could be bent out enough to still mount in the holes (I think I've done that before with other FETs).

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Re: Power PCB for Lebowski Controller to be combined with Bobc's processor board

Post by Alan B » Dec 04, 2017 9:13 pm

The TO247 makes the circuit board larger with little benefit.

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Re: Power PCB for Lebowski Controller to be combined with Bobc's processor board

Post by amberwolf » Dec 04, 2017 9:46 pm

I would have expected teh TO247 package to have better heat dissipation/conductivity, and higher leg-amp ratings. And allow for larger die size for more current handling/heat dissipation.

I'd assume from what you said that it doesn't?

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Re: Power PCB for Lebowski Controller to be combined with Bobc's processor board

Post by Lebowski » Dec 05, 2017 2:56 am

One thing I also like about the 247's is that you can use normal screws to attach them to the heatsink as the hole though the package is non-conducting. You only need some Kapton tape or heat conducting pad or something for drain isolation, no plastic screws or fiddly plastic washers.

Took a screenshot from Digikey, just searched for TO247 transistors, NMOS, between 75 and 100V, over 100A, NMOS, sorted by price:
FETs.png
(249.71 KiB) Not downloaded yet
The IXTH180 looks nice for a 150A controller...

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Re: Power PCB for Lebowski Controller to be combined with Bobc's processor board

Post by amberwolf » Dec 05, 2017 3:34 am

At least some of the TO247's have completely plastic cases, requiring no isolation pads. I don't know about modern ones, but I have some old 100A parts around here that are built that way. Can't recall the p/n.

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Re: Power PCB for Lebowski Controller to be combined with Bobc's processor board

Post by Njay » Dec 05, 2017 2:18 pm

Sometimes the TO-247 versions are beefier at the bounding wires.

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