Is this this mini circuit goin to work ? (small DRSSTC)

[hashtala]

I am trying to build a DRSSTC but I am short on part at this time.

I came up with a circuit that might work but I am not sure.

https://ibb.co/Y0nqWG1

will this give me any result if I use lower voltage for safety?
also I will be using PWM with duty cycle of about 200us and 200hz

[Max]

I see a minor flaw in that circuit: if Q1 is enabled/conducts it shorts the mains supply...

If you're that short on parts, forget about DRSSTCs. "Single MOSFET SSTC" or "Slayer Exciter", sometimes also found when searching for "HFSSTC" is what you want to build. Those circuits really need only a hand full of parts, nothing complicated or special. Most of them run reliable at about 20-50V, consuming around 100W. This gives you a couple centimeters of output. Not very spectacular, just like the BOM cost. And by far not as dangerous as your circuit either (still: be careful!)

DRSSTC running from mains power is something that requires careful design otherwise you will not only kill pretty much any part of the circuit but also put yourself in danger. Shorting mains supply - especially using capacitors - can lead to a decent explosion as I've demonstrated in the following video (jump to 0:52 and turn down the volume!):

Granted, that was more capacitance than you planned in your circuit but I also used bricks. Compared to small TO-264 MOSFETS they need an order of magnitude more energy before they really go kaboom. tl;dr: don't short the mains supply.


Kind regards,
Max

[hashtala]

Thanks for your answer.

I was worried about the same issue. I though it would not explode if I shorted it for a short period of time. I have additional light bulb in series before something explodes it will turn on and absorb energy.


BUT: I have a question.

Aren't we technically shoring main supply to ground in half bridge case? since primary actually has very low ohmic resistance?

[hashtala]

Also

which circuit do you think will perform better

https://ibb.co/NY9FBGg    left or right

or are they the same in terms of shorting?

[davekni]

"Aren't we technically shoring main supply to ground in half bridge case? since primary actually has very low ohmic resistance?"

No for two reasons.  First, the half-bridge is running at high frequency, where reactance of the inductor is much higher than DC (ohmic) resistance.  Second, if the half-bridge were to run at low frequency, the series capacitor reactance becomes high, so limits current.

For your two circuits, try them at low power and see what happens.  Or, better, simulate the two circuits.  There are free on-line simulators, and free downloadable ones such as LTSpice for larger circuits.

[hashtala]

davekni, thank you for your reply.

resonance frequency of my sytem is about 400,000Hz. This means I will be having high frequency input signal to power transistor as well. I think my second circuit is going to address that issue, but problem is that on low frequency there is no protection. ( I will be turning it on 200 times per second with short impulses (200 us long))


I was planning to run in on low power, thanks for your suggestion!