Electronics > Projects, Designs, and Technical Stuff
High frequency MOSFET Driver
diyaudio:
You might want to look at these babies, have them on order for a gate drive circuit I'm designing.
* 625mW POWER DISSIPATION
* IC CONT 3A
* 12A Peak Pulse Current
https://docs-emea.rs-online.com/webdocs/09c3/0900766b809c30e1.pdf
Also look at ZTX from Diodes Inc they make BJT's for this sort of applications.
BD136 and BD139 are ancient. still cost effective for medium power zener + transistor regulators, better options exists.
Marco:
--- Quote from: Saitama on July 13, 2019, 01:23:49 pm ---I plan to use this circuit to drive only one IGBT
--- End quote ---
So what is driving the high side one you have in a "half-bridge"?
magic:
Pains of BJTs can be remedied by building the driver out of FETs. Here's something I cobbled together from a few jellybean parts. Note that it requires increased supply voltage: -5V/20V.
M1/M2 can be just about any complementary FETs. Reasonable RDS(on), preferably small gate charge, preferably IPAK. Nice if it's rated for 30Vgs, or try with supply reduced to 15V, or add protection zeners.
M3 is used because a BJT was taking a long time to turn off and it looked just lame on simulation :P Could also give trouble in practice due to mismatched propagation delay of rising and falling transitions.
R1 must be 1W. C1/C2 recommended ;) Make the physical layout compact and ensure that connections are short.
David Hess:
--- Quote from: magic on July 14, 2019, 12:45:09 pm ---Pains of BJTs can be remedied by building the driver out of FETs. Here's something I cobbled together from a few jellybean parts. Note that it requires increased supply voltage: -5V/20V.
--- End quote ---
The higher MOSFET threshold voltage compared to the Vbe of a bipolar transistor requires higher supply voltages.
Common source/emitter output stages swing rail-to-rail but require extra complexity to avoid turning both transistors on during transitions.
--- Quote ---M3 is used because a BJT was taking a long time to turn off and it looked just lame on simulation :P Could also give trouble in practice due to mismatched propagation delay of rising and falling transitions.
--- End quote ---
Usually the storage time is irrelevant because the driver will be inside of a feedback control loop. But if it is a problem, then the input transistor can be baker clamped with a schottky diode. Or a fast saturated switching transistor can be used but their availability is poor.
magic:
--- Quote from: David Hess on July 14, 2019, 06:59:57 pm ---the input transistor can be baker clamped with a schottky diode
--- End quote ---
I actually know of this trick and tried it. According to SPICE, collector current starts to fall immediately after removal of base current (good) but it takes a linear ramp towards zero which is almost as long as the combined delay and fall time of unclamped and oversaturated transistor. Which is only worse, because now the driven FET is dragged through linear region for half microsecond.
Maybe it was good for speeding up digital circuits, but not so great for analog it seems. A more effective solution was reducing collector resistor to 100Ω, but not practical.
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