The half-wave rectifier, the principle of its operation and the circuit

The supply of electronic circuits for a variety of purposes requires a constant voltage source. In a conventional household network, the current is variable, its frequency is in most cases 50 Hz. The shape of the voltage variation graph is a sinusoid with a period of 0.02 seconds, with one half-period being positive relative to the neutral, the other half being negative. To solve the problem of its conversion to a constant value, rectifiers of alternating current are used. They come in different designs, and their schemes may differ.

In order to understand how the simplest half-wave rectifier works, one must first understand the nature of electrical conductivity. The current is the directed motion of charged particles, which can have opposite polarity, they are conventionally divided into electrons and holes, otherwise - donors and acceptors having "n" and "p" conductivity, respectively. If a material with n-conductivity is connected to another, p-type, then on their boundary a so-called pn-transition is formed, which restricts the motion of charged particles in one direction. This discovery made it possible to use semiconductor technology, replacing it with most tube electronics.

The half-wave rectifier basically contains a diode, a device with one pn junction. The alternating voltage applied to the input of the circuit at the output contains only half of it, one that corresponds to the direction of inclusion of the rectifier diode. The second part of the period, having the opposite direction, simply does not pass and is "cut off".

The diagram shows a single-phase rectifier, used most often in simple home devices and intended for domestic purposes. In industrial conditions, a three-phase network is often used , and therefore the schemes of converting AC to DC can be more complicated. In addition, as a rule, fuses and filters are included in the circuit. At the input of the circuit, a step-down transformer or other alternating voltage source may be included. Rectifier diodes differ in their parameters, the main of which is the value of the current to which the diode is designed.

The half-wave rectifier has a significant drawback in comparison with the full-wave rectifier. The voltage after rectification is not literally constant, it pulsates from the maximum value to zero in the half-sinusoidal form of the graph and has a zero value in the interval between the pulses. Such unevenness of supply is usually compensated for by incorporating a sufficiently large amount of a smoothing capacitor (sometimes measured in thousands of microfarads), calculated for a voltage not less than it appears at the output of the circuit, usually with a margin. Such a measure also does not provide an ideal flatness of the graph, but the deviation from the set value is significantly reduced, which makes it possible to use a half-wave rectifier to feed simple circuits that do not require high voltage stability.

In more complex cases, full-wave rectification schemes are used with subsequent stabilization.