Kapanadze Cousin - DALLY FREE ENERGY

[NickZ]

   Verpies, TK, and All:
   Well I finally got my order of new IRFP260N mosfets, but what I actually received were IRFP250P. So, I guess I'll make due with them, instead.
   
   As my TL494 board seems to be working now, I connected up two new fets to it, but find that they still heat up, as they had done previously with the now burnt out fets.
   So, my overheating problem is still with me, and any help or ideas are welcome, in order to solve this issue. 
I only get very low light output at my bulbs, so, there must be something which is not right, and which is causing the burning out of my fets.
   
   I also replaced my TL's board output resistors with new 1k resistors to ground, (instead of the 460ohm), and also the 1k resistors going to the TC4420 drivers, (instead of the stated 1k5 resistors). I had only 10 ohm resistors going to the drivers, previously, and 460ohm to ground.
 

[verpies]

As my TL494 board seems to be working now, I connected up two new fets to it, but find that they still heat up, as they had done previously with the now burnt out fets.

Are you still using this circuit ?

I had only 10 ohm resistors going to the drivers, previously, and 460ohm to ground.

That would have given you faster rise and fall times.

If the TL494.pin13 has 5V on it and you are taking the outputs from pins 9&10, then it means the TL494 is operating in push-pull mode with active-high pulses out of emitter follower outputs (pins 9&10 are emitters). 
The TC4420 is a non-inverting driver and the IRFP250P is an N-Ch enhancement mode MOSFET so their polarities are matching with active-high pulses.

I am afraid it will be difficult to help you without a scopeshot of drain currents and drain-source voltages.

[AlienGrey]

   Verpies, TK, and All:
   Well I finally got my order of new IRFP260N mosfets, but what I actually received were IRFP250P. So, I guess I'll make due with them, instead.

I only get very low light output at my bulbs, so, there must be something which is not right, and which is causing the burning out of my Fet's

Nick Hi have you tried disconnecting the yoke 3 to 6  turn winding from the 0.47 uf cap and connecting a car tail light bulb or head light bulb and seeing if the driver stage can light it up mine can light a 50 watt bulb up no problem, if it can you might have a shorted turn somewhere, see if you can break it down till you find the fault. good luck.

My test rig device is running with 16 to 24 volts 3.5 Amp on this test, (it's a 6 turn winding) and using high-speed IGBTs and even running a 50W quartz bulb nothing gets warm only the bulb.
AG

[starcruiser]

It sounds like they are overheating due to overlapping of the triggering pulses or they are not turning off fast enough (my guess is they are not turning off fast enough before the other FET is energizing).

[AlienGrey]

It sounds like they are overheating due to overlapping of the triggering pulses or they are not turning off fast enough (my guess is they are not turning off fast enough before the other FET is energising).

Unless he shows us a scope shot or breaks it down who knows ?

A G