What is the difference between fast recovery diode and normal diode?

Nowadays, electronic circuits have become an indispensable part of people's lives. Among them, diodes are one of the most commonly used components in electronic circuits. And diodes are divided into two types: fast recovery diodes and ordinary diodes. So, what is the difference between these two diodes?

The main difference between fast recovery diodes and ordinary diodes lies in their structure and the materials used. Let's first take a look at the structure of the fast recovery diode. The structure of a fast recovery diode is basically the same as that of a regular diode, consisting of alternating P-type and N-type semiconductors. But unlike ordinary diodes, fast recovery diodes set up a transcendental junction between P-type and N-type semiconductors, which is known as one of the special structures of fast recovery diodes.

When the forward voltage of the fast recovery diode reaches a certain value, the overjunction will enter a conduction state, thereby offsetting the additional voltage generated by the slow reverse recovery current of the ordinary diode, and improving the conduction ability. Therefore, the reverse recovery time of fast recovery diodes is shorter than that of ordinary diodes, and they have stronger energy efficiency.

On the contrary, the structure of ordinary diodes is relatively simple, consisting only of P-type semiconductors and N-type semiconductors. Under forward voltage, electrons flow from N-type semiconductors to P-type semiconductors, while under reverse voltage, only a very small number of doped impurity ions are excited to leave their free electrons, forming drift charges. The conductivity is relatively small, manifested as leakage current. If the reverse bias is too large, it will cause forward voltage breakdown and burn out the diode.

The application fields of fast recovery diodes and ordinary diodes are also different. Ordinary diodes are widely used in fields such as ordinary rectifiers, power supplies, and signal detection. For example, there are many ordinary diodes on the computer motherboard. Fast recovery diodes, due to their advantages of short reverse recovery time, high voltage resistance, and high frequency response, can be used in high-frequency circuits, high-precision converters, power converters, and other fields, and play a very important role in these fields.

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