Bias Supply Circuit Question
Bias Supply Circuit Question
(OP)
Hi All,
I'm an electrical that's coming from mostly experience in software and trying to learn some schematics of our current products.
Can't show it all but had a question about this circuit. We have an IC being fed by a 15V supply, it drives the gate of 2 MOSFETS in sync. Looking at the datasheet I understand all the resistors and caps on each input but I don't understand the purpose of the circuit. If we already have 15V, and we're driving both the driver circuit, and the MOSFETS, then why don't we just pass along that same voltage to the rest of the circuit where it gets bumped up to different values via bias transformer?
Are we using this to make sure the 15V is isolated, regulated, and "clean" from the original source? In that case why not just use 1 switch in a buck boost topology?
Appreciate it,
I'm an electrical that's coming from mostly experience in software and trying to learn some schematics of our current products.
Can't show it all but had a question about this circuit. We have an IC being fed by a 15V supply, it drives the gate of 2 MOSFETS in sync. Looking at the datasheet I understand all the resistors and caps on each input but I don't understand the purpose of the circuit. If we already have 15V, and we're driving both the driver circuit, and the MOSFETS, then why don't we just pass along that same voltage to the rest of the circuit where it gets bumped up to different values via bias transformer?
Are we using this to make sure the 15V is isolated, regulated, and "clean" from the original source? In that case why not just use 1 switch in a buck boost topology?
Appreciate it,





RE: Bias Supply Circuit Question
RE: Bias Supply Circuit Question
Not sure though because the schematic has a +15V supplying the driver circuit (going to each gate)...but the same 15V supply also goes to the drain of Q4. Q5 source goes down to the return terminal.
Why not just go straight from the original 15V? its only going to be able to source so much current regardless of some switches in line with it no?
RE: Bias Supply Circuit Question
The circuit exerpt you've provided is a very common architecture. It's essentially one half of an H-bridge. Search Google Images for H-bridge.
RE: Bias Supply Circuit Question
TTFN
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RE: Bias Supply Circuit Question
Having a hard time finding literature on that though. I get results saturated with motor rotation from the full-H topology. Much less on this being used as a DC to AC source. Its probably going to give a pretty rough AC waveform out no?
Thanks for the feedback
RE: Bias Supply Circuit Question
TTFN
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RE: Bias Supply Circuit Question
Seems strange to me that we'd generate AC this way through the board...but as one of the comments mention - there is a transformer immediately after the two mosfets. In order for that to work, it would have to be AC...
Sorry to be a pest on this circuit. I've gone ahead and worked forward on all the others with no problems but this one really confuses me.
RE: Bias Supply Circuit Question
TTFN
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RE: Bias Supply Circuit Question
RE: Bias Supply Circuit Question
RE: Bias Supply Circuit Question
That's precisely why notation and clarity is critical to such discussions. Switched DC does NOT require decomposition into Fourier components. Totem pole drivers do have 50% efficiency because their transition regimes are generally designed to be a small portion of the duty cycle. The OP did not show enough of his schematic to conclude that his design is a sinusoidally driven class A output.
TTFN
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