boylesg
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Does any one know where I can obtain a spice model for this component that will work in multisim 11?
I see two points:
- simulation. A TC4422 Spice model is available from Microchip and can be imported in any Spice based simulator, also Multisim
- hardware. As far as I understand, the real problem is failure of your hardware design. I won't expect any insights in this regard from a simulation, because you don't see the effects that possibly damaged the device.
As a side remark, I don't understand the power circuit as shown in post #3. Unfortunately it can't be viewn in detail. Do you have Z-diodes in parallel to the MOSFET?
I don't want to guess about the failure mechanism. But 1N5819 schottky diodes aren't a suitable replacement for 75V Z-diodes.
In "this circuit", there's only one 1N4007 and no TC4422. Looks like a riddle "guess the original circuit", maybe posted in the wrong forum?In this circuit the 2 x 1N4007s do not protect the TC4422 from transient spikes
In "this circuit", there's only one 1N4007 and no TC4422. Looks like a riddle "guess the original circuit", maybe posted in the wrong forum?
What difference does this make? Is it easy to explain or something I should just take your word for? Does that also mean the GND pins need to be externally connected?Both TC4422 VCC pins are internally connected, they should be used both and connected externally, too.
I understand that the mosfet is protected by the series zeners, but apparently that does nothing for the TC4422 as it keeps frying on me. So clearly I need another layer or protection in here specifically for the TC4422.....hence the snubber circuit I am trying to figure out.The MOSFET driver should be primarly protected by bypass capacitors and power zener respectively transsorb diode limiting the supply voltage to the allowed range.
The datasheet tells to connect all GND pins.Does that also mean the GND pins need to be externally connected?
Of course not because absolute maximum rating is 20V.I understand that the mosfet is protected by the series zeners, but apparently that does nothing for the TC4422 as it keeps frying on me.
The datasheet tells to connect all GND pins.
Of course not because absolute maximum rating is 20V.
What most likely happens is that the wiring inductance between battery and output transformer generates a kickback voltage that exceeds the said 20 V. Massive bypassing and Z-diode protection with suitable voltage level should be able to protect driver and MOSFET gate.
In a world of ideal designs, there's no wiring inductance, only the transformer primary inductance. But in practice there's wiring inductance. If it's only 0.1 µH versus 1 µH transformer inductance, you get 10 % of the inductive kickback at your 12V supply, but without any limiting means.I knew that kick back was killing the TC4422, but what I was forgetting was that the Jaycar jacobs ladder kit documentation states that they have only limited the kick back voltage to within the limits if the Darlington transistor they used. And that is something like 200V from memory - well in excess of the TC4422 limits.
In a world of ideal designs, there's no wiring inductance, only the transformer primary inductance. But in practice there's wiring inductance. If it's only 0.1 µH versus 1 µH transformer inductance, you get 10 % of the inductive kickback at your 12V supply, but without any limiting means.
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