Half-wave rectifier

The simplest rectifier circuit uses one diode to chop off half of the alternating current input cycle.

In a half-wave circuit, the average output voltage is approximately 45 % of the RMS ac input voltage. But PIV across diode can be as much as 2.8 times RMS alternating current input voltage. It is a better to use diodes whose PIV ratings are at least 1.5 times the maximum predictable PIV; thus, with a half-wave supply, the diodes must be rated for at least 4.2 times the RMS alternating current input voltage.

Half-wave rectification has certain shortcomings. First, the output is difficult to smooth out, as the waveform is so irregular. Second, voltage output tends to drop when supply is connected to load. (This can be overcome to some extent by means of a good voltage regulator. Voltage regulation can be discussed later in this chapter.) Third, ½ wave rectification puts a disproportionate strain on power transformer and diodes. 1/2 wave rectification is useful in supplies which do not have to deliver much current, or that do not need to be well regulated. The basic advantage of using a 1/2 wave circuit in these situations is that it costs less than full wave or bridge circuits.