A 250W PWM inverter circuit built around IC SG3524 is shown here.
SG3524 is an integrated switching regulator circuit that has all essential circuitry required for making a switching regulator in single ended or push-pull mode
The built in circuitries inside the SG3524 include pulse width modulator, oscillator, voltage reference, error amplifier, overload protection circuit, output drivers etc.
SG3524 forms the heart of this PWM inverter circuit which can correct its output voltage against the variations in the output load.
In a non PWM inverter the change in output load directly affects the output voltage (when output load increases output voltage decreases and vice versa), but in a PWM inverter the output voltage remains constant over a range of output load.