Why 540 mosfets are unhappy!

[dave_j_fan]

that is just a temporary place.. 

got the extech210 meter .. will work on the overload circuit
finally


experts  do provide guidance
@wiss
* yes the trafos hav  single primary , i ordered them to make a stepdown smps
  now suitable for the reverse
   
 
* Most drivers have rectifiers  i suppose the bulb too has fast enough diodes , seen the flood led driver having bridge

i also have UF4007 in the HV line , adding this stopped the heating of transformer

* inductive kick should be within limits (guess work is the voltage is <200V) i will measure with this trueRMS DMM

wiss ,
 can  i combine 4 tiny transformers(max 15Watts) and make a 60watt inverter?
 each being fed with a mosfet and final voltages somehow clubbed with diode or some arrangement

if possible i can make a scalable inverter that can give many driving capacity based on the  number of MOSFET and trafo pairs   

[wiss]

that is just a temporary place.. 

got the extech210 meter .. will work on the overload circuit
finally


experts  do provide guidance
@wiss
* yes the trafos hav  single primary , i ordered them to make a stepdown smps
  now suitable for the reverse

I've only seen flybacks use single-primary, could be made to work here...
_NEVER_ run that without a load!
Make sure that you have fast full wave rectification on the secondary!
It can produce very high voltages!

 
* Most drivers have rectifiers  i suppose the bulb too has fast enough diodes , seen the flood led driver having bridge

If they are for 50/60 Hz they will not be fast enough, add switching diodes, fast recovery or schottky diodes.

i also have UF4007 in the HV line , adding this stopped the heating of transformer

* inductive kick should be within limits (guess work is the voltage is <200V) i will measure with this trueRMS DMM

The DMM will be way too slow to measure anything. The peak will be as high as the breakdown of whatever is in front of it!

wiss ,
 can  i combine 4 tiny transformers(max 15Watts) and make a 60watt inverter?
 each being fed with a mosfet and final voltages somehow clubbed with diode or some arrangement

if possible i can make a scalable inverter that can give many driving capacity based on the  number of MOSFET and trafo pairs

Drivers and primaries separate and the combined after secondary rectification? probably...
Post a schematic!

[wiss]

BTW, this circuit could very well kill your brand new multimeter in a few microseconds...

[planet12]

I second @wiss on the updated schematic request. Given what's been said, I'm not sure whether it's now a flyback or some kind of mutant one-switch forward converter (without a reset winding?).

Details on the transformer would also be good - anything you have from the manufacturer about it would help.

[dave_j_fan]

that is just a temporary place.. 

got the extech210 meter .. will work on the overload circuit
finally


experts  do provide guidance
@wiss
* yes the trafos hav  single primary , i ordered them to make a stepdown smps
  now suitable for the reverse

I've only seen flybacks use single-primary, could be made to work here...
_NEVER_ run that without a load!
Make sure that you have fast full wave rectification on the secondary!
It can produce very high voltages!

 
* Most drivers have rectifiers  i suppose the bulb too has fast enough diodes , seen the flood led driver having bridge

If they are for 50/60 Hz they will not be fast enough, add switching diodes, fast recovery or schottky diodes.

i also have UF4007 in the HV line , adding this stopped the heating of transformer

* inductive kick should be within limits (guess work is the voltage is <200V) i will measure with this trueRMS DMM

The DMM will be way too slow to measure anything. The peak will be as high as the breakdown of whatever is in front of it!

wiss ,
 can  i combine 4 tiny transformers(max 15Watts) and make a 60watt inverter?
 each being fed with a mosfet and final voltages somehow clubbed with diode or some arrangement

if possible i can make a scalable inverter that can give many driving capacity based on the  number of MOSFET and trafo pairs

Drivers and primaries separate and the combined after secondary rectification? probably...
Post a schematic!

well scary voltage spikes i came to know from you..but why single primary makes highvoltages?

regarding rectifiers @ bulbs and floodlights
i dont want to modify the load items .. that end user will not b able to do .

given  the schematic ..i n a way this is way easy solution wrt Joule ringers that people have  reasearched months ..efficiency part yet to check
did trialswith a few 5630SMD LEds for a bulb idea!  to accompany  this inverter
The bulb is not done yet ,but 7 leds gave pretty good light

schematic attached

[tom66]

Where's your snubber? You'll kill that MOSFET pretty quickly. If you've put the transformer windings in opposed directions all you've made is a flyback, a very inefficient one at that.

If you put them in the same direction and add a reset winding in reverse on the primary, with one end to supply and diode to ground, you'll make a fairly nice forward converter (you'll also have to change the output topology)
http://www.powerelectronicsconsultant.com/uploads/3/6/3/8/3638391/2592511.jpg

[wiss]

There is a thin explanation of the turn-off spike here:
http://www.maximintegrated.com/en/app-notes/index.mvp/id/3983

This page is more about an alternative method to reset the core, which might be useful in your application.

You do have an oscilloscope?

[planet12]

@dave_j_fan I think it would be to your great advantage to have a good read through the following two app notes from Microchip - "Switch Mode Power Supply (SMPS) Topologies" part one and two:

AN1114 - SMPS part 1: http://ww1.microchip.com/downloads/en/AppNotes/01114A.pdf

AN1207 - SMPS part 2: http://ww1.microchip.com/downloads/en/AppNotes/01207B.pdf

It's great that you're willing to jump in and give it a go building things up, but these documents will help you greatly in your understanding - and also allow you to talk to us in the standard terms, eg. "one switch/two switch forward converter" / "flyback converter" and know what is meant by them.

@wiss - I hadn't seen that resonant reset technique, thanks for the pointer! *scurries off to the lab to play with it*

[wiss]

@wiss - I hadn't seen that resonant reset technique, thanks for the pointer! *scurries off to the lab to play with it*

I just googled for an explanation of forward converters and stumbled over it just now
If my bench weren't full of other things I would too. I do suspect that it might not behave under no-load...
Please report @planet12 !

[dave_j_fan]

3roomlab
 there are hours on inverter videos good post ..

planet12/wiss

many  thanks ..links helping a lot
reading mosfet protection http://www.circuitstoday.com/how-to-protect-mosfet-devices


yes the mOSfets may take charge build up and kill itself , i will short the gate 

---i will come back after a while testing a dumb touch fan control --