A Novel Sine Wave Inverter with PWM DC Link

Pulse width modulation (PWM) switching technique is commonly used in full bridge converters to overcome the bulky filter requirements and efficient voltage control, at the cost of higher switching losses. However, all PWM techniques not only cause circuit complexity but also need high frequency switches such as MOSFETs with high conduction drop causing lower efficiency. This paper presents a novel sine wave inverter circuit which uses a full bridge topology with a PWM DC link. The PWM DC link is generated by using a buck switch in series with the DC source which is switched with unipolar sine PWM signal continuously. The bridge inverter switches are supplied with line frequency gate signals which are synchronized with the original modulating sine wave signal. The proposed inverter uses five switches out of which only one switch is switched at high frequency, while other switches operate at low (line) frequency which not only make the overall efficiency high but also make the voltage control simple as only one switch is supplied with controllable PWM signal. The proposed topology with switching technique was simulated and a prototype model was developed in the laboratory to prove its feasibility.