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2018-08-19, 03:21:29
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Author Topic: TK sidethread to that at OU.com  (Read 4241 times)
Group: Moderator
Hero Member
*****

Posts: 530
Hello guys.

OK, I really need some help.

Basically, since I have been  playing around with pulsing flybacks, I have managed to blow one HP frequency generator (FG), two power supplies and endless mosfets.

@ronotte had provided me with a circuit (shown below) to which I can connect my FG and have the circuit do the actual battery to primary pulsing. But that circuit blew the IRF7307 so I want to do the same thing as his circuit but instead of using the 6N137, I will use a FOB3180 opto and instead of using the IRF7307, I will use one IRF9540 P-Channel and an IRF840 N-Channel mosfet. The output will still be using another IRF840 mosfet.

What i would require is a total circuit diagram showing all the connections, resistors, capacitors, mosfet ends identified as well as showing which side of the opto is pin #1, etc. I need a really complete schematic diagram and if anyone can run this on a sim to make sure the resistor values are correct.

I know this is asking alot but my EE is just not up to par with my coil building skills.

I decided to migrate this here because the TK thread just keeps flying off in more tangents and I want to keep concentrated on these next tests.

I would like to make this circuit, tests it out and if it is strong enough to last, maybe then make the move to have the circuit board premade for other OUers that really need this type of control.

Anyways, if there is anyone that can help out, I would greatly appreciate it. @ronotte is pretty busy with his present works that I just do not want to drag his attention away from what he is doing.

wattsup



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Hero Member
*****

Posts: 1231
The two proposed circuits are not capable of adequately
driving a Power MosFet.  The input capacitance of the
power MosFet demands a very rapid charge current which
can easily exceed two Amperes at turn-on and , similarly,
a very rapid discharge current of the same magnitude at
turn-off.

Unless the MosFet is adequately driven at its Gate it will
be vulnerable to "burn-out" due to excessive time spent
in its linear region as it transitions from OFF to ON and
then back to OFF.

The only way to assure that a Power MosFet is driven with
sufficient "oomph" to produce the fastest possible full turn-on
and full turn-off is by means of a Driver Chip.

To obtain the kind of isolation you're seeking you may make
use of a newly available chip by Analog Devices:

Datasheet attached.

Here is the promotional video which explains its characteristics.





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