HELP: Battery Powered Inductive Circuit

[hotrodman106]

Hello All,
I'm hoping someone smarter than myself can help me out with this one because I am bashing my head clean through a wall
This is my inductive transmitter circuit. Essentially, I have an ATTINY45 generating a 180khz square wave which drives a MOSFET and subsequently drives a coil to transmit current to the receive antenna. Now, for the most part this circuit works fine on my bench power supply (barring when I drive it a bit to hard) HOWEVER, the minute I attach this to a 12 volt battery, either the polyfuse trips or, if I remove the polyfuse, the MOSFET goes disco inferno. I'm guessing this has something to do with transient current on the power lines feeding the board but I have no idea WTF is going on and how can I fix it?
Thank you all in advance!

 

[rjenkinsgb]

There does not appear to be any real power decoupling on the power supplies? It's normal to have a good size electrolytic as well as a small polyester or ceramic cap across each power rail, anything from eg. 10uF to 1000uF depending on the current loading.

Adding a 100 or 470uF across the 12V power may mean you get the same effect on a bench supply.

If the antenna coil circuit is resonant at the drive frequency it could easily be building up to a higher voltage than the FET can stand.
Or the duty cycle it just too high and the current is building up beyond the FET capability.

It very much depends on the coil characteristics and how that is tuned.

 

[Nigel Goodwin]

You give no clue as to what the coil is?, is it simply shorting the supply out?.

 

[hotrodman106]

You give no clue as to what the coil is?, is it simply shorting the supply out?.

There does not appear to be any real power decoupling on the power supplies? It's normal to have a good size electrolytic as well as a small polyester or ceramic cap across each power rail, anything from eg. 10uF to 1000uF depending on the current loading.

Adding a 100 or 470uF across the 12V power may mean you get the same effect on a bench supply.

If the antenna coil circuit is resonant at the drive frequency it could easily be building up to a higher voltage than the FET can stand.
Or the duty cycle it just too high and the current is building up beyond the FET capability.

It very much depends on the coil characteristics and how that is tuned.

Few different things, my apologies on not citing the coil specs, that was dumb. I salvaged the coil from a different circuit so I don't have super detailed specs on it, however I know its a single coil but dual layer, it's 50mm in diameter, has a SRF of ~180khz, and should have an inductance of somewhere in the 20uH range give or take. You are correct that there is no power decoupling which may very well be a problem, that's easy enough to implement. I should also mention that I am driving the coil at it's SRF