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I am trying to build a high frequency step-up transformer for PWM signals.

The signal that I want to step-up with transformer has to be modifiable with the 2 pulse signal generators. PWM signal to step-up transform

So Freq 1 and Freq 2 are regulated by the user for a value from 1Hz to 150kHz. The core of the transformer is ferrite, meant for high frequencies.

Then for that I thought that the best solution was a N type MOSFET and use the Freq 1 as Gate and Freq 2 as Drain, but then I found my self with lots of bad planning (newbie) mistakes. So before I go on trying newbie things I though better to get checked my ideas before buying new things to build something that is wrong from the basis. Thanks in advance.

So here I add a circuit with what I think could be the solution, sadly I think is something wrong. I have two MOSFETs because the PWM generator only gives 1-30 mA, which I think is too little to step-up voltage, so I put one MOSFET directly to the 20V that can give about 3 A.

schematic

simulate this circuit – Schematic created using CircuitLab

For sure you will have better ideas, I just look for a solution to make this PWM signals with high voltage (from 0V to 300V, or more if possible).

The use of PWM generators or MOSFETs is not mandatory, but both frequencies have to be regulable by user.

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    \$\begingroup\$ Why not take a step back, and tell what waveforms you have and what waveforms you need, instead of asking how to do something with them using a transformer? Does it need to be isolated? Would a simple level shifter do the job? \$\endgroup\$
    – Justme
    Mar 2 at 17:39
  • \$\begingroup\$ Hi "Justme", I had a look at level shifters, but I don´t understand the point. I already got my 2 PWM signal generators that can give voltages up to 20V but with very little current (only 1-30mA) so the idea is with MOSFET use this small current signals to put the same voltage on the transformer. Please, if I didn´t understand how to use the level shifter tell me again. Thanks!! \$\endgroup\$
    – Javiero
    Mar 2 at 21:18
  • \$\begingroup\$ Maybe you should first tell for what purpose you need the signals, what voltages and currents you are trying to achieve? Right now you just seem to want to use transformers to do something, but we can't understand what it is and why. I ask this because you may have an X-Y problem, and transformers may not be the way to solve your original problem. \$\endgroup\$
    – Justme
    Mar 2 at 21:22
  • \$\begingroup\$ On the other side of the transformer there is a choke and a capacitor and the idea is to make resonance and achieve very high voltages with low current input (but not as low as 1-30mA) \$\endgroup\$
    – Javiero
    Mar 2 at 21:25

1 Answer 1

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sadly I think is something wrong

Here's the basic problem: -

enter image description here

You can't put DC through a transformer; transformers are for AC signals that have an average voltage level of zero. If you try and put DC through you'll saturate the core and probably destroy your MOSFETs when they deactivate.

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  • \$\begingroup\$ As I understood the theory of transformers, the signal doesn´t have to be AC but can't be DC, it needs a voltage variation, so AC would be from for example -10 to +10V and in this case with PWM would be from 0V to 20V. That is not possible? Is true that I don´t know if at the step-up side of the transformer the voltage will also be negative with, for example for the PWM something like 300V to -50V. \$\endgroup\$
    – Javiero
    Mar 2 at 21:12
  • \$\begingroup\$ Hi "Andy aka", I just saw your post answering: How to properly wind a high frequency / high voltage transformer? - electronics.stackexchange.com/questions/236092/… it gives a lot of useful information. I have to study the case more. Thanks \$\endgroup\$
    – Javiero
    Mar 2 at 21:31
  • \$\begingroup\$ @Javiero the average voltage level associated with the signal feeding a transformer has to be zero. It has to be an alternating voltage of average value zero. \$\endgroup\$
    – Andy aka
    Mar 2 at 22:31
  • \$\begingroup\$ @Javiero you don't "have to" put pure AC into a transformer, but only the AC component is coupled across the transformer; all of the energy in the DC component is wasted, it leads to unwanted heating, and premature saturation. It's not something you want. \$\endgroup\$
    – hobbs
    Mar 2 at 23:00

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