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The four generators indeed go to zero, but after one second theres is a high freq sinusoidal signal on the output for the rest of 0,1 second.
I put a 100ohms-100nF snubber across one of the Mosfet and that signal stopped. Seems like a ringing or something.
Well, the Simulator seems like a...
virgiox
thanks for the idea. Never thought of such an approach.
I am very newbie on LTSpice. Could you explain your sources setup of V1 to V4 please?
Regarding the MosFets protection, for such conditions a SS36 would be OK?
Ioannis
Hi Diver300,
you are right about that. The current cannot be the same in every voltage set (1-40volts) or any frequency (1-50Hz). Also I do know that the coil will be saturated in many combinations, but this is what the requirements need.
To protect from overcurrent I will add a shunt...
Hi Dana.
Thanks for the link. Lots of good info but not on the protection of discrete MosFets. Rather a presentation of the ICs that ST carries as a compete chip solution.
Ioannis
Hi!
I am searching for the appropriate MosFet to build an H-Bridge for 40Volts at 15Amps max current. Will drive a coil of about 18mH (a very big 60cm coil of 2mm wire). The frequency that will feed the coil is from 1 to 50Hz.
Unfortunately all MosFets I found have not the SOA that is needed...
It seemed to me that, since the input voltage is a recified 100Hz it would not matter, but proves it does.
Looking again the circuit I see another flaw in the design. That PNP current limiting transisor is limiting the speed that Mosfet is turning ON as it limits the current in safe levels, but...
You are right. I forgot to draw the resistor from gate to ground, of 270K. That way the Mosfet is driven to ON state and the optocoupler would turn it OFF when the difference of output to C1 voltage is more than 10 volts.
I attach the corrected file. Thank you for spoting the error.
Ioannis
Indirect because Mosfet was getting hot.
OK, here is the schematic with the opto coupler. The regulator is not important and was used for testing only. The real regulator is different.
The idea is that when the output is around 10volts less than the cap C1 voltage, the Mosfet M1 turned OFF and...
It could be, but all I tried (4N25-27, PC817) had the same result.
Maybe something was wrong in the Mosfet driving circuit. Did not turn it on/off fast eough. Will make a ciruit file and upload it.
Ioannis
Yes, I see your point.
Let me express another idea that I tried on the fly with not good results though, because I used optocouplers. Optocouplers are not fast enough and the end result was enough power loss.
I 'll try to make a schematic later but the general idea is to have a Mosfet right...
One other idea is to use a lower voltage, say 0-48 Volts DC as primary supply and then drive a half bridge of switching circuit like that of #21 post. Adjusting the Vdc of the bridge may also adjust the voltage of the secondary of the ferrite transformer. This needs also an adjustable SMPS of...
It is a small production (about 15 pcs per year) of a Electrophoresis Power Supply, (https://www.signalcom.gr/en/electrophoresis-power-supplies/electrophoresis-power-supply-ps-220/) and that is why I was not able to show the schematic of the current design.
I wish to offer clients a better...
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