What Is the Meaning of Rectifier?

Half-Wave Rectifier

• A half-wave rectifier may be useful to visualize AC and DC current in terms of a lake and a river. Alternating current is like the waves washing onto the lake's shore, and then washing away. Direct current is like a river, steadily moving in its predetermined course. When alternating current moves through a diode, the diode allows power through in one direction but blocks it in the other direction. In other words, the rectifier allows half the wave through, and is therefore called a half-wave rectifier. Picture a half-wave of water entering a river bed every few seconds, rather than a steady flow of water.

Full-Wave Rectifier

• Converting the whole wave form to direct current requires two diodes, usually incorporated into a transformer. One diode allows the top half of the AC power's waveform to pass through, while the other diode does the same for the bottom half. The two outputs are routed through the transformer to the rest of the circuit, where they provide an output that is nearly steady, but does still pulsate. In effect, you now have more water passing through the gate you've been envisioning, but still as a series of pulses rather than a steady flow.

Bridge Rectifiers

• For most purposes, creating usable direct current from an AC input requires a more sophisticated arrangement of components referred to as a full-wave bridge rectifier. Full-wave bridges combine two pairs of diodes, each converting either one-half of the positive side of the AC waveform, or one-half of the negative side. This makes twice as many pulses, but smaller ones, closer to a steady flow. The outgoing current is fed through capacitors, which store current when it is flowing, and release it when the input stops. This creates a steady flow of direct current, like a river emerging from a tunnel.

Uses of Rectifiers

• The most common and important use of rectifiers is in power supplies and battery chargers for electronic devices. Some of these are the familiar external "bricks" that plug into the wall and power laptop computers and cellular phones. Others are built into components such as stereos and DVD players, converting the AC input for use by the device's internal circuitry. A second very common use is in radio receivers and cellular phones, where rectifiers perform a similar conversion on the incoming radio waves.'