Powering electronic circuits for various purposes requires a constant voltage source. In a conventional household network, the current is alternating, its frequency in most cases is 50 Hz. The shape of the voltage change graph is a sinusoid with a period of 0.02 seconds, while one half-cycle is positive relative to the neutral, the second is negative. To solve the problem of converting it to a constant value, AC rectifiers are used. They come in different designs and their designs may vary.
In order to understand how the simplest half-wave rectifier works, you must first understand the nature of electrical conductivity. The current is the directed movement of charged particles, which can have opposite polarity, they are conditionally divided into electrons and holes, otherwise they are donors and acceptors having conductivities of "n" and "p" types, respectively. If a material with n-conductivity is connected to another, p-type, then a so-called p-n junction is formed at their boundary, limiting the movement of charged particles in one direction. This discovery allowed the use of semiconductor technology,replacing most tube electronics with it.
A half-wave rectifier basically contains a diode, a device with one p-n junction. The alternating voltage at the input of the circuit contains only half of it at the output, the one that corresponds to the direction of switching on the rectifier diode. The second part of the period, which has the opposite direction, simply does not pass and is “cut off”.
The diagram shows a single-phase rectifier, most often used in simple home appliances and designed for domestic purposes. In industrial environments, a three-phase network is often used, so AC-to-DC conversion circuits can be more complicated. In addition, as a rule, fuses and filters are included in the circuit. A step-down transformer or other source of alternating voltage can be switched on at the input of the circuit. Rectifier diodes differ in their parameters, the main of which is the amount of current for which the diode is designed.
A half-wave rectifier has a significant disadvantage compared to a full-wave one. The voltage after rectification is not literally constant, it pulsates from the maximum value to zero in a half-sine shape of the graph and has a zero value in the interval between pulses. This uneven supply is usually compensated by the inclusion of a smoothing capacitor of a fairly large value (sometimes measured in thousands ofmicrofarads), designed for a voltage not less than that occurs at the output of the circuit, as a rule, with a margin. Such a measure also does not ensure the ideal evenness of the graph, but the magnitude of deviations from the set value is significantly reduced, which makes it possible to use a half-wave rectifier to power simple circuits that do not require high voltage stability.
In more complex cases, full-wave rectification schemes are used with subsequent stabilization.
