Operational Amplifier Based Low Power dc-ac Converter for Domestic Applications

In Indian households, voltage source inverters (VSIs) are generally found as a part of uninterruptible power supplies for washing machines, refrigerators or air-conditioning units. Besides power electronic switches, the power circuit of VSI comprises of gate drivers and snubber circuitry. This results in increased component count and complexity. With a suitable pulse width modulation (PWM) technique, VSI can provide sinusoidal currents. However, the output voltage waveform is in the form of bidirectional pulses. This can have a detrimental effect on the performance of the load and necessitate passive filtering. This paper presents an operational amplifier (op-amp) based low power dc-ac converter for domestic applications. For 1-phase loads, in place of four power electronic switches and associated circuitry, a single op-amp OPA549 is employed to act as a dc-ac converter and generate ac supply for the domestic loads from the dc supply. The magnitude, phase and frequency of the thus generated ac voltage depends on the control signal, which acts as a reference signal and can be generated through a microcontroller as is the case with the traditional VSIs. Additionally, the voltage and current waveforms are also sinusoidal. This is validated by the experimental results obtained from the prototype OPA549 based VSI.