These are interesting products, and I'm always amazed at how low cost a
consumer product can be. I think these typically have a flyback converter
that converts the 12VDC to +/-170VDC. They then have an H-bridge that
switches the +/-170VDC out at 60Hz. A rectangular waveform is used with
the duty cycle set so the RMS is 120VAC and the peak voltage is 170V.
Doing all that for $17 is quite a trick!

Harold


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