AC to DC Conversion with Full & Half-Wave Linear Rectifiers

Many types of electrical equipment are powered by alternating current (AC). When converting AC to DC, a linear rectifier, or simply a rectifier, is made up of diodes and, in certain situations, a transformer. In the online DC-DC converter courses, the students will learn about Bode Plots and how to draw them for any converter.

What is a Rectifier?

Rectifiers are classified into two types: full-wave and half-wave. Full-wave rectifiers convert a full AC waveform into a sequence of single-polarity DC pulses, whereas half-wave rectifiers just shut out half of an AC signal’s electrical output, leaving DC pulses.

Historically, we’ve seen a number of different intriguing devices achieve voltage rectification, which we’ll discuss later in the essay.

Half-Wave Rectifier

Because an AC circuit’s voltage swings between a positive and negative value—for our example, we’ll use the 60Hz 120VAC value common in the US—removing the negative or positive half of this electrical wave would result in a fairly choppy supply of DC power. This transfer method may be accomplished with a single diode that only permits the current to travel in one way.

Notice that “120VAC” is the root mean squared (RMS) power value, which is a more realistic interpretation of the 170 and -170-volt peaks of the sinusoidally fluctuating mains power source.

If you remove the maximum -170V component of the waveform, you’re left with power that rises up to +170VDC, then drops to 0V for 1/120th of a second (since a whole AC power cycle takes 1/60th of a second) before rising back up to 170.

This form of conversion reduces power production significantly. In theory, this equates to 40.6% of the AC input. In actuality, due to the unavoidable loss of efficiency that occurs with conversion, this figure would be lower.

Aside from reduced average power, a possible disadvantage of this sort of conversion is that the converted electricity is delivered in intermittent pulses.

This constraint is used in one intriguing application of this conversion method: a simple AC light bulb dimmer. Because of the tiny breaks in electricity flow, the light might remain lighted but looks weaker to human vision.

How Does a Full-Wave Bridge Rectifier Work?

A single diode may convert alternating current to direct current, but a bridge rectifier requires four diodes to reverse the direction of both sides of the alternating current pulse.

The DC oscillates from zero to a peak value using a bridge rectifier, but it does not cut off half the time. This approach delivers double the power to a DC output as a half-wave, resulting in a potential power conversion ratio of 81.2% (lower in the real world, again).

This type of rectified power also filters more readily to produce a clean DC output. Even if the output ranges from zero to a maximum in a sinusoidal pattern, the non-instantaneous gaps typical of half-wave rectified DC do not occur.

There are detailed evaluations of single and three-phase rectifiers, diode and thyristor-based, as well as the most popular applications in the online ac dc rectifiers courses. The options of the output filtering stages of the converter are addressed. Power quality concerns are also investigated.