I have created a 24VAC 100W sinewave inverter that uses an ATMega8535. The Mega, is used to control, amongst other things, a boost converter from 24VDC to arround 35VDC, which is then used to create the 50Hz sinewave output via a H-Bridge.
The Sine PWM section is via OC1A, running at 12.288MHz/510 ~24KHz. There are 480 steps in the initial Sinewave table which varies from min 5, to max 250, to allow for refresh of the bootstrap capacitors on my HIP4080A H-Bridge driver IC.
The problem is the Output Filter LC. Without the output filter I can drive loads to over 150W.
The original filter, uses 470uH inductors, 2.2uF to 0V from each output, and 4,4uF between each output.
With the filter in place, the inductors either run Hot, or cause the inverter to fail. Going up to a 1.57" iron powder torroid (Amidon T157-26mix) seems OK, but why is the output filter size so big?
What if this was a 240V application?
I would be happy to share my code, and perhaps hardware for a valid solution to this problem.