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InPhase

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Joined: 15/12/2020
Location: United States
Posts: 178

Posted: 07:49pm 12 Mar 2023

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I have been steadily tinkering and improving my DIY inverter. Not much public fanfare on here, because it is just a hot mess of wires and amateur-ish PCBs. But it really does work well. I've tested it to over 4000 watts resistive and it easily starts a 3 HP pump under load. It is currently 24 volts input, but I'm well underway on the next gen 48 volt version.

I currently use a DIY DC-DC converter with 6 isolated outputs to create the bipolar gate drive voltages, but it's a bit clunky. For those who use isolated supplies and negative gate voltages, what are you using to supply the gates?

oreo

Senior Member

Joined: 11/12/2020
Location: Canada
Posts: 101

Posted: 08:14pm 12 Mar 2023

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Not for your particular application, but I am using the following modules.
ebay 1
ebay 2

my battery is nominal 72v, so I have needed higher voltage, isolated step downs.

These are nice and compact, but not rated at 48 nominal volts.
ebay 3

Greg

noneyabussiness
Guru

Joined: 31/07/2017
Location: Australia
Posts: 526

Posted: 09:33pm 12 Mar 2023

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AU $7.75 5%OFF | 5Pcs B0515S-1W Isolated dc-dc power modules B0515S 1W DC DC boost Converter 5V to 15V 1W
https://a.aliexpress.com/_msRKCaa

these are good for gate drivers.. many different input / output voltages, compact and easy to use..

I think it works !!

pd--
Senior Member

Joined: 11/12/2020
Location: Australia
Posts: 122

Posted: 09:43pm 12 Mar 2023

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If you are looking for a drop in component
https://recom-power.com/en/applications/gate-drivers/gate-drivers.html?0

rustyrotors
Newbie

Joined: 07/01/2023
Location: United States
Posts: 36

Posted: 09:09am 15 Mar 2023

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noneyabussiness said AU $7.75 5%OFF | 5Pcs B0515S-1W Isolated dc-dc power modules B0515S 1W DC DC boost Converter 5V to 15V 1W
https://a.aliexpress.com/_msRKCaa

these are good for gate drivers.. many different input / output voltages, compact and easy to use..

i am using the Mornsun modules too. i think i went a little overkill on my inverter with a 3A, 30W module. i agree a 1W module is really all you need

please correct me if i am way off, but i figure typical hy4008 with 200nC Qg, worst case switching at 30kHz, 24 fets, up to 12 switching simultaneously:

ave gate current = 200nC * 30kHz switching * 12 fets = 70mA

15V gate drive * 70mA ave gate current = 1W required from gate power supply

and for output cap = 200nC gate charge * 12 fets / 0.25V ripple = 10uF

wiseguy

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Joined: 21/06/2018
Location: Australia
Posts: 1204

Posted: 11:23am 16 Mar 2023

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rustyrotors said

please correct me if i am way off, but i figure typical hy4008 with 200nC Qg, worst case switching at 30kHz, 24 fets, up to 12 switching simultaneously:

ave gate current = 200nC * 30kHz switching * 12 fets = 70mA

15V gate drive * 70mA ave gate current = 1W required from gate power supply

and for output cap = 200nC gate charge * 12 fets / 0.25V ripple = 10uF

You said "up to 12 FETs switching simultaneously". I think that you only need to account for the 8 FET's doing the HF switching? The other two FETs are switching at a 50Hz rate?

Empirically, I measured the current required for each HY4008 switching 53V at 20kHz from 12V and ~ 4mA of drive current was used (per FET), the other 2 groups of FETs were switching at 50Hz and their drive current requirements are negligible

In my experience a 1W dc/dc converter (12V @ ~ 80mA) or (15V @ ~65mA) should easily supply the drive current required for a group of 4 Mosfets even at a 30kHz rate.

If at first you dont succeed, I suggest you avoid sky diving....
Cheers Mike

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