I am developing a power inverter. It has 40 VDC as input and it will provide 220 VRMS at the output.

Our idea is to generate a bipolar signal from a H-Bridge then amplify the output by a transformer. What is the best way to select this transformer?

We made a little proof of concept with low power compsumition and a common transformer AC/AC (220~24,) and the transformer gets warm. The losses efficency about the transformer relation (9 times passed to 6).

Should I select a high frequency transformer?

Should I select a toroidal transformer?

  • 1
    \$\begingroup\$ Please clarify your specific problem or provide additional details to highlight exactly what you need. As it's currently written, it's hard to tell exactly what you're asking. \$\endgroup\$
    – Community Bot
    Sep 14, 2022 at 14:05
  • \$\begingroup\$ What power range do you want to achieve? \$\endgroup\$
    – Jens
    Sep 14, 2022 at 20:01
  • \$\begingroup\$ The question looks clear to me. The question looks clear to Andy (as he has adedand answer). Why are people downvoting? \$\endgroup\$
    – Russell McMahon
    Sep 16, 2022 at 10:45

1 Answer 1


It sounds like you are either using the H bridge to produce a sinewave input to the transformer in a linear fashion or, you are using PWM to create an equivalent sinewave. Either way will be fraught with inefficiencies; either the H-bridge will get warm (linear sinewave generation) or the transformer will get warm (PWM).

You never mentioned the H-bridge getting warm so I'll concentrate on the PWM problems.

If you use high-speed PWM switching to create a pseudo sinewave, the high frequency harmonics will play havoc with a regular power transformer. You'll get significant eddy-current losses due to the laminations simply being to fat. Ferrite (as used in HF transformers) do not conduct and therefore have very low eddy current losses.

My solution would be to step-up the 40 volts to something like 320 volts DC. I'd use a high-frequency transformer and a high-frequency driver to do this. So now, you have an isolated 320 volts DC rail and, to finish the job off, I'd use a H-bridge to generate the sinewave using PWM techniques and, add a low-pass filter on the output to return the generated signal to something close to a decent sinewave: -

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