Ground short problem in power switching

Kiran Khunte

I made the above circuit with the following objectives :

1. The pulse which I am applying at transistor Q8's base is being carried away to an output terminal which is source terminal of IRF540 MOSFET.

2. When the opamp's output is negatively referenced then MOSFET should be always off.

The topmost circuit branch is expected to carry a high amount of current.

I have asked some of freinds about the circut whether its practically applicable what they told me is you cannot short the ground directly to transistor and some other things.

Please specify if any mistakes is there.

P.S. I have run PSpie simulation of it and its giving expected results.

over 7 years ago

0 LeonardEllis over 7 years ago

TI__Guru 71526 points

Hello Kiran,

The circuit you are discussing did not get attached/included in your post. Be sure to use the
Insert Code, Attach Files and more... and then click the 'attach' icon on the toolbar to include the schematic.

Thank you for using E2E,

~Leonard

0 Kiran Khunte over 7 years ago in reply to LeonardEllis

Prodigy 125 points

Here is the circuit.

Thanks for pointing out the mistake.

0 Collin Wells over 7 years ago in reply to Kiran Khunte

TI__Guru 63965 points

Hello Kiran,

What is the supply voltage to the op amp? 20V? Without feedback you're using the op amp as a comparator and based on the input voltages you're using it to create a logic HIGH output. If the amp inputs are not switched maybe it makes more sense to tie this node to a constant DC voltage.

0 Kiran Khunte over 7 years ago in reply to Collin Wells

Prodigy 125 points

The opamp is used as comparator here, with +20V and +0V as refernced voltage levels.

The opamp is used as a switch between to pass the pulse from from transistor Q8 collector terminal to base of MOSFET.

Thanks.

kiran

0 Collin Wells over 7 years ago in reply to Kiran Khunte

TI__Guru 63965 points

Based on that it looks like you want an "AND" type function where both the op amp output and the V15 output must be driven HIGH to allow the M1 transistor to turn on.

This looks like it will work, but the actual implementation may require some extra components and testing based on the inductance/capacitance in the system that may cause undesired voltage/currents to appear.

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Ground short problem in power switching