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Suppressing/Filtering this circuit...

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rx5

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Hello guys,

any one can suggest HOW I could supress reverse inductive spikes?!?!(is this the right term???) on this oscillator.. it runs great on lower voltages BUT when i supply it with 12-15VDC, it gets DEAD...

-raff
 

What exactly happens when you apply 12-15V .. oscillations stop or Q1 is killed?
You may try to add a resistor (100-470Ω) between the base of Q1 and transformer's winding ..

Regards,
IanP
 

Hi IanP,

I think the oscillation stops..... Ive used 4.7uF tantalum and it burned after a few minutes .... then the circuit DIED....also the transistor heated so MUCH,,

is it OK too IF I shunt a diode in the colector-gnd winding??
 

As far as the 4.7µF cap is concerned, the best choice will be a bipolar cap .. if you don't have it, use electrolytic capacitor rated for at least 25V ..

Instead of a diode in parallel with the transformer's winding I would connect a 24V 1W zener diode in parallel with the power transistor - cathode to +V (emitter), anode to the collector ..

Regards,
IanP
 

IanP,

how do I lower the frequency by a few KHz??? increase turns on the feedback?? increase value of feedback capacitor?? resistor??

:)
 

why don't you use dedicated PWM IC with MOSFET driver output i think that should be more reliable
regards
 

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