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Solar Mike Guru Joined: 08/02/2015 Location: New ZealandPosts: 1138
Posted: 09:59am 10 Feb 2021
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Whilst doing some research, came across some of the new design D2PAK-7 mosfets, they are very impressive, along with a better driver chip; so thought I might throw something together to give them a try out. I quite like the idea of not using a separate driver pcb module and using a bootstrap technique for the upper mosfet drive supply. The D2PAK mosfets allow a better layout over external TO247 types.
This latest design version 4.x uses a Silicon Labs Si823H4BB-IS1 isolated half bridge mosfet driver chip driving D2PAK - NTBGS4D1N15MC mosfets in a synchronous buck format; these ones are only 150v rated so PV voltage limited here.
The mosfets are soldered direct onto the top surface of the pcb, with heat conducted to the lower layer by a multitude of vias, the pcb them clamps via an heat conducting insulator to an alloy bar attached to the case side panel to conduct heat away. I have some 25mm x 25mm x 80mm alloy bars left over from an older project, so will put them to good use.
These type of mosfets have multi-source connection pins with short parallel internal links, resulting in very low lead inductance along with low RSon resistance; means I don't require multiple paralleled chips for high power output. The design has 3, one each for the PV-Battery isolation, buck converter and synchronous rectifier.
Here is the driver:
First cut of PCB 155 x 205mm:
As yet no schematic and no vias added on the pcb yet, just built on the fly, will do a schematic to pick up my errors.
Cheers Mike
Davo99 Guru Joined: 03/06/2019 Location: AustraliaPosts: 1578
Posted: 09:44pm 10 Feb 2021
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Geez you build a lot of Stuff!
I am very jealous of your skills and talent.
Haxby Guru Joined: 07/07/2008 Location: AustraliaPosts: 423
Posted: 11:29pm 10 Feb 2021
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That SI823HX looks like a great chip.
Nice find! And I agree with Davo, your industrious pace is hard to beat!
Solar Mike Guru Joined: 08/02/2015 Location: New ZealandPosts: 1138
Posted: 10:40pm 11 Feb 2021
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Ha the more you do, the easier it gets. Writing the software seems to be the most difficult and time consuming bit, I really must start using the Micro-Mites or something else in these designs.
Here's the final as yet unchecked layout, added those vias, just over 1100 of them, could never had prototyped a DIY version without the low cost of getting boards made in China. Big yellow tinned areas need additional thick copper wire soldered to pcb to support 60A current - with prototype's 1oz copper.
I have placed all high current carrying circuitry in the upper half of pcb, low power control, cpu etc has its own separated ground plane, with a single 0v connection point at the main PSU. Will see if I can locate any higher voltage mosfets for this so I can test it on a 100v battery bank (190v PV)
Top:
Bottom:
Will do a schematic next to check layout.
Cheers Mike
Solar Mike Guru Joined: 08/02/2015 Location: New ZealandPosts: 1138
Posted: 11:23am 12 Feb 2021
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Schema for power stages.
Cheers Mike
Solar Mike Guru Joined: 08/02/2015 Location: New ZealandPosts: 1138
Posted: 09:41am 14 Feb 2021
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Updated complete Schema, pcb layout checked, couple minor reposition changes, so wont repeat it. Send off to be made, Chinese new year, may take a while. I did locate some higher voltage mosfets to test with 200V PV, on order.
Cheers Mike
Solar Mike Guru Joined: 08/02/2015 Location: New ZealandPosts: 1138
Posted: 12:29am 16 Feb 2021
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Update, JCLPCB site appears broken, cannot login or place any orders, same with LCSC, they share a common Easy EDA sign in screen which appears to not be working, their Gerber viewer is also broken, national holidays, wonder how long it will take them to fix it.
Edit: Not long, tried again after a couple of hours and seems back to normal.
Mike Edited 2021-02-16 17:58 by Solar Mike
Solar Mike Guru Joined: 08/02/2015 Location: New ZealandPosts: 1138
Posted: 03:03am 22 Feb 2021
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Update: Finally sent the gerbers off today, delayed a little due to creating another design. I was intrigued by the possibility of mounting the larger TO-247 mosfets in a similar manner, surface mounted with the pcb vias acting as the heat conducting medium to the heatsink under the pcb; in this case the mosfet mounting bolt clamps the device to the top surface when screwed into the heatsink below. Have no idea how well this will work, but means I can use the higher voltage devices for PV exceeding 200v. Edit: caps I'm using here each have a ripple rating > 5amps, those cheap hunglow brands just wont work here.
So sort of threw this one together, its got just the basics to work, no Blinky lights, just an lcd serial display and piezo, have opted for the 30-35mm caps here as I have a box of them that need using up.
Pcb is 160 x 200mm.
I wont be creating a schematic of this, its basically same as above without the extras.
Notice. New forum software under development. It's going to miss a few functions and look a bit ugly for a while, but I'm working on it full time now as the old forum was too unstable. Couple days, all good. If you notice any issues, please contact me.
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