Power Inverter DC-AC definition

Power inverter is a device that converts electrical power from dc form to ac form using electronic circuits. Its typical application is to convert battery voltage into conventional household AC voltage allowing you to use electronic devices when an AC power is not available. There are basically three kinds of dc-ac inverters: square wave, modified sinewave, and pure sine wave. The square wave is the simplest and the least expensive type, but nowadays it is practically not used commercially because of low quality of power. The modified sine wave topologies (which are actually modified square waves) produce square waves with some dead spots between positive and negative half-cycles. They are suitable for many electronic loads and are the most popular low-cost inverters on the consumer market today. Pure sine-wave inverters produce AC voltage with low total harmonic distortion (typically below 3%). They are used when there is a need for clean sine-wave outputs for some sensitive devices such as medical equipment, laser printers, stereos, etc.
Most commercial DC-AC inverters circuits use the same basic concept: a low dc voltage from the input source is first stepped-up to a higher-voltage dc link corresponding to the peak value of the desired ac voltage. A second power stage then generates an ac voltage by using full-bridge or half bridge configuration. Cheap square wave circuits may also use push-pull converter with step-up transformer. Output voltage can be controlled either in square-wave mode or in pulse width-modulated (PWM) mode. In PWM pure sine-wave circuits, the output voltage and frequency are controlled by varying the duty cycle of the high frequency pulses. Chopped voltage then passes through an output LC lowpass filter to produce a clean sinusoidal output.