another gate driver

PV gate drivers are nice, but they are slow turning on when supplying a lot of gate charge. The ADI parts, with internal power isolators, are expensive and insane power hogs.

So maybe we could separate the power transfer from the gate drive functions:

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Another possibility would be to use the single PV driver, but blast the LED side with extra current at the turn-on edge.

Or just stick with my flyback gate driver.

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Or maybe use a standard DC/DC converter as an isolated gate driver, if we could find a cheap one that was fast enough on/off and didn't waste a lot of power.

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John Larkin         Highland Technology, Inc 

lunatic fringe electronics
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John Larkin
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fig. 11

how fast? some of these

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claim a typical startup of a few 100 us into 10uF

Reply to
Lasse Langwadt Christensen

The PV optocouplers use the same trick (Q1) to fast discharge the gate capacitance. But the PVs have low output current, so can't turn on a fet very fast of it has a lot of gate charge. Some fat fets need 100 nC.

Something like that would work. A cheap converter probably won't have much output capacitance, so turn-off time might not be bad. We'd like well under 1 ms on/off times. We could load the output with a resistor or a depletion fet. I think we have some of these bricks around; I'll play with one.

My home-made flyback thing above isn't bad, about 75 cents for parts. The little potted dc/dc converters run around $2.50 each. This sort of thing:

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The 2KV isolation spec is nice.

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John Larkin         Highland Technology, Inc 

lunatic fringe electronics
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John Larkin

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