The difference between rectifier diodes and switching diodes

The difference between rectifier diodes and switching diodes

The difference between rectifier diodes and switching diodes can be distinguished by their characteristics, working principles, and operating characteristics.

1、 Characteristics

rectifier diodes utilize the unidirectional conductivity of PN junctions to convert alternating current into pulsating direct current. The rectifier diode has a high current flow, and most diodes are packaged with surface contact materials. In addition, the parameters of the rectifier diode, in addition to the ones mentioned earlier, also include the maximum rectifier current, which refers to the maximum current allowed to pass through therectifier diode during long-term operation. It is the main parameter of the rectifier diode and the main basis for selecting the rectifier diode

The switching time of a switching diode is mainly determined by the transition time from the on state to the off state, which is also known as the reverse recovery time. The time required from the beginning of applying reverse bias voltage until the reverse current drops to 1/10 of the starting value is called the reverse recovery time. When the P+N switching diode is in the on state, holes are injected from the P+region into the N region, forming a forward conduction current. That is, there is always a certain minority of charge carriers stored in the N region during the on state. After adding anti bias voltage, the diode can only be in the off state when all the minority carriers stored in the N region are eliminated.

2、 Working principle

When a semiconductor diode is turned on, it is equivalent to a switch closing (circuit on), and when it is turned off, it is equivalent to a switch opening (circuit off). Therefore, the diode can be used as a switch, and the commonly used model is 1N4148. Due to the unidirectional conductivity of semiconductor diodes, the PN junction conducts under positive bias, and the resistance in the conduction state is very small, about tens to hundreds of ohms; Under reverse bias, it is in a cut-off state and has a high resistance. Generally, silicon diodes are at 10 Μ Above Ω, germanium tubes can also range from tens to hundreds of kiloohms. By utilizing this characteristic, a diode will play a role in controlling the current on or off in the circuit, making it an ideal electronic switch.

3、 Working characteristics

The time from the cut-off (high resistance state) to the conduction (low resistance state) of the switching diode is called the turning on time; The time from conduction to cut-off is called reverse recovery time; The sum of two times is called the switching time. Generally, the reverse recovery time is greater than the opening time, so only the reverse recovery time is given in the usage parameters of the switching diode. The switching speed of switching diodes is quite fast, like the reverse recovery time of silicon switching diodes, which is only a few nanoseconds, and even germanium switching diodes, which are only a few hundred nanoseconds.