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easy PWM mosfet drive?




 
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Author Topic: easy PWM mosfet drive?  (Read 680 times)
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km6sn
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« on: May 28, 2020, 01:40:29 PM »

Hi All,

After studying the TPA3116D2 stereo PWM amp boards ebay it seems to me
they would easily drive high power mosfet gates directly, by

1. running the board at 5 or 6 volts, or whatever you need, and
2. eliminating the LC filter on the board; connect directly to the chip output, and
3. run coax to the mosfet gate, or better yet, very large short wire, and
3. put a 6 or 8 ohm resistor right at the gate.

The real load on the board would be during the gate charge time. But with
rDS on resistance in the vicinity of 120milliOhms, the gate charge may not
be a problem.

In any case, I suspect any distortion introduced at turn on/turn off times would
be filtered out by the high power LC filter to the RF deck.

Please post any thoughts or concerns on this approach. I think I will try it after
I make my rig to drive the 3-500 one-holer.

73,
Rod


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M0VRF
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« Reply #1 on: May 29, 2020, 12:10:31 PM »

Just use any half bridge driver chip.
IR2110 is somewhat ancient but works fine.
There's Nigel's design on here somewhere.

I'm not sure why your try to use a chip designed for audio to drive MOSFET gates at 100s of KHz.

I'm not saying it won't work but there are much simpler and better ways..

JB.
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km6sn
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« Reply #2 on: May 29, 2020, 12:19:22 PM »

JB,
Well, the audio board has a  built-in PWM circuit. I think I will give it a try.
Rod
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km6sn
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« Reply #3 on: May 29, 2020, 12:35:47 PM »

JB,

I probably did not make it clear: I am proposing using
the board by taking off the LP filter and piping the
raw PWM directly to the gate.
Roed
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M0VRF
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« Reply #4 on: May 30, 2020, 07:20:31 AM »

Yes I fully understand what you are trying to do!

I guess you don't want to lay out a PCB?

Regards

JB.
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km6sn
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« Reply #5 on: May 30, 2020, 10:39:20 AM »

Actually, I already have a PCB. The problem is my hands shake so badly it is impossible to solder SMT devices.

So, this approach may be useful to me and to others.

Regards,
Rod
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