i am working on true sinewave 200VA HOME UPS.i am getting 80 to 82% inveter efficiency at 40W to 100W incandescent lamp load.After 100watt to 200watt load my invterter efficiency is gradully decresing and at 200watt load i am getting 70%.i have taken all efficiency tests at openloop microcontroller based control.how can i improve my efficiency at 100watt to 200watt load.