The crystal diode is actually a P-N junction, which has unidirectional conductivity and can make the alternating current into direct current. This effect is called rectification. The so-called unidirectional conductivity is that the diode is turned on by the forward voltage under the action of the forward voltage, and the diode is not turned on under the reverse voltage. There are many types of rectifier circuits, such as half-wave rectifier circuits and bridge-type full-wave circuits. The half-wave rectification circuit is a rectification method that removes the half cycle and the lower half of the figure. It is not difficult to see that the half-wave whole wave can be said to be exchanged for the rectification effect at the expense of “sacrificial” half of the exchange, and the current utilization rate is very low (calculation shows that the average value of the half-wave voltage obtained by rectification is over the entire period, ie The DC voltage Usc = 0.45e2 on the load is therefore commonly used in high voltage and low current applications, and is rarely used in general radios. The full-wave rectification circuit can be considered as a combination of two half-wave rectification circuits. In the middle of the secondary winding of the transformer, a tap is drawn to divide the secondary coil into two symmetrical windings, thereby extracting two equal voltages e2a and e2b of opposite polarity to form e2a, D1, Rfz and e2b, D2, Rfz, Two energized circuits. The bridge rectifier circuit is the most used rectifier circuit. Such a circuit, as long as two diode ports are connected to form a “bridge” structure, has the advantages of a full-wave rectifier circuit, while at the same time overcoming its disadvantages to some extent.