The above figure is the most basic half-wave rectifier circuit we have encountered, which is one of the most basic and simplest circuits in all rectifier circuits. Therefore, the advantage of this circuit is that it has a simple structure, and there are few components used in the circuit, so it has been used a lot in some simple circuits. However, it is clear that this half-wave rectifier circuit, while simple, must also have a number of drawbacks. Because this circuit only uses half a cycle of alternating current, the direct current component of the output of this circuit is very low, and the AC component is relatively large, which leads to a large ripple in the output circuit waveform.
Therefore, this half-wave rectifier circuit is generally suitable for circuits with smaller currents. When we need a circuit with a higher current or higher DC composition, we usually use more complex and full-featured rectifier circuits, such as full-wave rectifier circuits and bridge rectifier circuits.
The half-wave rectifier circuit in the picture above is composed of three parts, the first is the transformer T, then the rectifier diode VD, and finally the load resistor RL. In the above circuit, the AC voltage UI (i.e. mains 220V) is connected to the primary coil L1 of transformer T. After the step-down treatment of transformer T, the AC voltage U required for the post-stage circuit is generated at both ends of the secondary coil L of transformer T. Next, the converted AC voltage passes through the rectifier diode VD and then becomes the DC voltage U. The rear load rl. is given in total
The following analyzes the specific work process, and we further analyze it separately.
When the UI AC input is in a positive half-cycle, U is positive and negative. Because the rectifier diode VD has the characteristics of unidirectional conduction, the current i in this circuit is along the direction of the rectifier diode from the positive electrode to the negative pole, that is, the current i forms a loop through the rectifier diode VD and the load RL.
When the alternating current at the UI is in a negative half-cycle, the U is in a negative state at the top and positive at the bottom. In this case, due to the unidirectional conductivity of the rectifier diode, the rectifier diode VD is cut-off and the current i is equal to 0, so there is no voltage drop across the load RL.
As shown in the figure above, we can see from the waveform of the working process that the half-wave rectifier circuit only has voltage output when U is in the positive half-cycle, and there is no voltage output when the U is in the negative half-cycle. Thus, u. The DC component is very small, but the AC component will be more. Because this circuit only uses half of the U sine wave, half of which is wasted, so the rectification efficiency of this circuit is very low.