so it converts DC to AC, and now you can vary the frequency, but you can't make gas with AC, so you'll rectify it, then you'll have pulsed DC with variable frequency, but it only goes up to 650 Hz, which doesn't give much room to find resonance.
I'm just trying to understand it, nothing against it, in fact because of this i finally understood how capacitors and resistors work in a circuit to control frequencies!