Consultation

[bendilmi]

It is my pleasure to consult you about an electronic problem that I have faced while I was making a ''High voltage generator'' based on a small and simple circuit which is joined in this document.
The circuit is made and it is quiet functional, but after few minutes or sometimes just by switching it ON it gets damaged, and the components that always get burn are either the NE555 that generates the command signal, or the transistor put in sires between the primary of the amplifying transformer and the ground, which by its turn is commanded by the NE555, I have tried my suggested solution from few colleagues and so, but none of them was really useful, so with all my respect it would be a great pleasure if you manage to help me about this, and thank you

 

[Alec_t]

Welcome to EP!

after few minutes or sometimes just by switching it ON it gets damaged

Sounds like a voltage spike could be causing Q2 collector-base breakdown, which would pass a current pulse through the 555.
Is Q2 on a heatsink?
What peak current does Q2 draw?

 

[bendilmi]

yes it is mounted on a heat sink, Q2 is rarely burned, the NE555 is the one that gets damaged most of the time while Q2 still functional and Q2 draws a current that has a square chape but the value is not mesures yet !

 

[bendilmi]

we thought the same, so we put a power diode in the output of the 555, but still have the same problem !

 

[bendilmi]

q2 is a mosfet

 

[Audioguru]

1) Why do you have coupling capacitor C6? R5 should be connected directly to the gate of the Mosfet.

2) The 1N4007 power diode is made for 100Hz or 120Hz, not 15kHz. When C6 is removed then the diode is not needed.

 

[bendilmi]

1n4007 just to creat a negative 0,7v in the gate of mosfet because ne555 gives us logic state and i want to assure that state LOW must be 0v.

 

[bendilmi]

I putted c6 for the same reason just to disallow continue voltage to passes to mosfet

 

[davenn]

I putted c6 for the same reason just to disallow continue voltage to passes to mosfet

what continuous voltage ? there isn't one ... well there shouldn't be one
there is only a voltage there when there is an output on pin3 of the 555

 

[bendilmi]

I don't know why but ne555 oscillate between 12 and 2v !?

 

[CDRIVE]

You have other things going on in there besides your FET and 555 issues. Your power supply is ...uh..?? Have you consulted the 78L12 Datasheet for its maximum input voltage? R2 will not protect it from exceeding that rating.

Chris

 

[davenn]

Have you consulted the 78L12 Datasheet for its maximum input voltage? R2 will not protect it from exceeding that rating.

agreed
and that is probably why you have this ....

I don't know why but ne555 oscillate between 12 and 2v !?

you will probably find that the output of the 78L12 isn't stable

 

[bendilmi]

You have other things going on in there besides your FET and 555 issues. Your power supply is ...uh..?? Have you consulted the 78L12 Datasheet for its maximum input voltage? R2 will not protect it from exceeding that rating.

Chris

I know that maximum voltage for the 7812 is 30v ..... My power supply generate 24v DC and befor 7812 i put 7815 ..... My problem is on the mosfet and ne555

 

[(*steve*)]

My power supply generate 24

But it says it generates 60V?!

 

[bendilmi]

But it says it generates 60V?!

I resolved this problem, i changed the power supply to smps 24v 4,5A

 

[(*steve*)]

Ok. If you still have a problem then please redraw your circuit so it represents what you're now using.

 

[bendilmi]

Ok. If you still have a problem then please redraw your circuit so it represents what you're now using.

Ok , i try to include every modification i did cause the problem still embarrassing me :/

 

[Audioguru]

What is the part number of your 555? Maybe it is a LMC555, TLC555 or ICM7555 Cmos one.
Did you remove C6 and the diode?

 

[bendilmi]

What is the part number of your 555? Maybe it is a LMC555, TLC555 or ICM7555 Cmos one.
Did you remove C6 and the diode?

Hhhh i used more than 50 pieces of ne555 .... When i remove c6 the mosfet heat more and more .... Diode didn't remove it yet