Sorry for the hijack
@vivensub , now back to business with the half-wave rectifier.
You say you have a grasp of how a half-wave rectifier works, and just want to know how it can be used.
While the full-wave rectifier is more commonly used, a half-wave rectifier can be used to simply provide a DC supply voltage from an AC supply voltage, when ripple isn't too much of a concern. Almost always used in conjunction with a 'smoothing' capacitor, to smooth the rectified waveform into usable DC rather than a series of pulses.
Here's a circuit with a transformer, in which the secondary winding is feeding a diode, (half-wave rectifier), and the pulsed DC output has a load resistor across it.
View attachment 22058
The problem with this is that the pulsed DC is not usable as a DC supply. DC circuits usually need a much more constant voltage, with the ripple smoothed into a more consistent waveform.
Adding a capacitor, like in the next diagram, smooths the waveform to a more acceptable shape:-
View attachment 22059
The smoothing capacitor stores energy right up until the maximum positive input voltage, then releases it when the voltage drops in the trough, keeping the output voltage more constant.
As mentioned, for power supply purposes a half-wave rectifier is not often used, at mains frequencies, due to the high ripple.
As frequency increases, however, a capacitor becomes more efficient, and so a similar sized capacitor will achieve a far greater level of smoothing. A good example of a half-wave rectifier being used in a higher frequency application is an old-school CRT TV set, which uses high frequency to switch a transformer, and most of the secondary voltages from the transformer are only half-wave rectified, with relatively large capacitors for smoothing.
Another use for a half-wave rectifier is in a simple 'sample-and-hold' circuit, where the capacitor is charged to the peak voltage of the input waveform, (minus 0.6V, the diode forward voltage), then the diode stops the capacitor from discharging when the input voltage drops again. In this case, in an ideal circuit, there would be no load resistance, since the capacitor will discharge through that load. In practice, there is always some leakage into the circuit componenet following the capacitor.
Yet another use is as a pulse-length extender. Exactly the same as the crude 'sample-and-hold' described above, but the load resistance is chosen to discharge the capacitor in a given time, known as the RC time constant. One RC time constant is 'resistance multiplied by capacitance', which is the time it would take for the capacitor to lose 63% of it's voltage, discharging into the resistance. It takes 5 RC time constants for the voltage across the capacitor to approach zero again.
I think that this has been long-winded enough, so I'll stop here.
I hope you found this useful.