Features and Applications of Fast Recovery Diodes

Features and Applications of Fast Recovery Diodes

The switching speed of Fast Recovery Diodes is much higher than that of ordinary diodes and  The switching diodes. They are often used in switching power supply output terminals, switching power supplies, chargers, high-frequency heating equipment, converters, ultrasonic cleaning machines, electric welding machines, UPS, and motor control. Rectifier diode A semiconductor device used to convert alternating current to direct current.st important characteristic of a diode is unidirectional conductivity. In the circuit, current can only flow in from the positive terminal of the diode and flow out from the negative terminal. Usually it consists of a PN junction with two terminals, positive and negative.

     The carriers in the P region are holes, and the carriers in the N region are electrons, forming a certain potential barrier between the P region and the N region. When the applied voltage makes the P region a positive voltage relative to the N region, the potential barrier is lowered, and storage carriers are generated near both sides of the potential barrier, which can pass a large current and have a low voltage drop (typically 0.7V), which is called positive to the ON state. If the opposite voltage is applied, the potential barrier is increased, it can withstand high reverse voltage, and a small reverse current (called reverse leakage current) flows, which is called reverse blocking state. Rectifier diodes have obvious unidirectional conductivity. Rectifier diodes can be made of materials such as semiconductor germanium or silicon.

     Silicon rectifier diodes have high breakdown voltage, low reverse leakage current, and good high temperature performance. Usually high-voltage and high-power rectifier diodes are made of high-purity single crystal silicon (it is easy to reverse breakdown when doped more). This kind of device has a large junction area and can pass a large current (up to thousands of amps), but the operating frequency is not high, generally below tens of kilohertz. Rectifier diodes are mainly used in various low-frequency half-wave rectification circuits. If full-wave rectification is required, they must be connected into a rectifier bridge.

     Fast recovery rectifier diodes belong to the high frequency rectifier diodes in rectifier diodes. The reason why they are called Fast Recovery Diodesis that ordinary rectifier diodes generally work at low frequencies (such as the mains frequency is 50Hz), and their operating frequency is lower than 3kHz. When the operating frequency is tens to hundreds of kHz, the change time of the forward and reverse voltages is slower than the recovery time, and ordinary rectifier diodes cannot normally achieve unidirectional conduction. At this time, fast recovery rectifier diodes are required.

     The characteristic of fast recovery diode is that its recovery time is very short, which makes it suitable for high frequency (such as horizontal frequency in TV) rectification.Fast Recovery Diodes have an important parameter that determines their performance - reverse recovery time. The definition of reverse recovery time is that the diode changes sharply from the forward conduction state to the cut-off state, from the time the output pulse drops to the zero line, and the time required for the reverse power supply to recover to 10% of the maximum reverse current, the common symbol trr express. The trr of an ordinary fast recovery rectifier diode is several hundred nanoseconds (10-9s), and the trr of an ultra-fast recovery diode is generally tens of nanoseconds. The smaller the Trr is, the higher the operating frequency of the fast recovery diode is.