What Is Used to Convert AC to DC?

AC and DC explained

Electricity is measured by the flow of particles, known as "electrons." These particles can flow in two directions--forward and Backward. With direct current (DC) electricity, the electrons only move in one direction (forward), which keeps the electrical current always flowing in one direction. Alternating current (AC), however, works differently. AC electrical current moves like a wave (such as a sine wave from trigonometry) with the levels rising and falling. The current changes direction as well. As a result, electrons flow in both directions, thus giving it the name "alternating current."

Converting AC to DC

AC can be converted to DC, using one of two methods, depending on the desired efficiency and complexity of the device. Both methods use a rectifier, which can be made up of one or many sub-components called "diodes." The most efficient type of rectifier is known as a full-wave rectifier. It uses four diodes and converts all the AC electricity into DC. To do this, it lets the electricity flow normally when it is going forward, but when the electricity flows backward it reroutes it through the diodes so that it ultimately flows forward again. The other type of rectifier is called a "half-wave rectifier." It uses only one diode which simply blocks the electrical current when it is flowing backwards. This sort of device, while simple, is only able to convert half the AC electricity, which makes it inefficient.

Issues with AC-to-DC conversion

One issue with the conversion of AC to DC is that 100 percent efficiency is not possible. This is because the diodes have their own electrical resistance and voltage, which causes some of the electrical current to dissipate. The other main issue with the conversion of AC electricity is due to its cyclical nature; the current rises and falls in a steady cycle. This can be partially alleviated with the addition of a smoothing filter, which consists of a capacitor. Because capacitors can store electrical charges, the capacitor becomes charged when the current is at its peak and discharges its electricity when the current is low. While this does smooth the current out, there will still be periods where the current is slightly higher or lower than the average or smoothed-out current.