In order to convert between direct current (DC) and alternating current (AC), some type of inverter is required. A DC to AC voltage converter essentially switches the direct current source back and forth between positive and negative values using a circuit known as an oscillator. The two main classes of DC to AC voltage converter are differentiated based on whether the output is a modified square or pure sine wave, depending on the complexity of the oscillator circuit. A DC to AC voltage converter can be used to power electronic devices using the batteries found in automobiles, recreational vehicles and boats, solar panels, and other sources.
The difference between direct and alternating current is that electrons in DC circuits move in only one direction, while those in AC circuits periodically reverse their flow. This can be examined by testing the voltage in a circuit. A DC circuit will show a constant, positive voltage if the leads are hooked up correctly, while an AC circuit will cycle between positive and negative voltage. When viewed on an oscilloscope or similar device, the alternating current available from the power grid will appear as a sine wave.
A DC to AC voltage converter functions by switching a direct current source back and forth in order to approximate a sine wave. The oscillator circuits used to accomplish this were once mechanical in nature, though a variety of solid state designs have been created. Simple converters create a type of modified square wave that involves the voltage staying positive for a time, dropping directly to zero, moving in a straight line to a negative voltage, and then back again. Square wave AC power is sufficient for many devices, though in some cases a purer waveform is necessary. Pure sine wave inverters are a more expensive type of DC to AC voltage converter that use additional control circuitry to approximate the sine waves seen in grid power.
An inverter will typically also use transformers and various control circuits to generate the desired level of voltage and current to power a device. Small inverters are available that can plug into the cigarette lighter in a car, which typically provides a limited amount of wattage. The power output of an inverter tends to be limited by the input circuit. Inverters that are used with solar panel installations can provide power to an entire house, and pure sine wave models are often used to tie these systems into the grid.
