Application Fields of Fast Recovery Diodes

Application Fields of Fast Recovery Diodes

Fast Recovery Diodes are common in circuits, so in which fields are Fast Recovery Diodes widely used?

With the development of power electronics technology towards lightweight, miniaturization, intelligence, and energy-saving, the applications of various control circuits, uninterruptible power supplies, and switching power supplies are constantly expanding. As a high-frequency and high-voltage fast soft recovery diode that directly affects the rationality and operational reliability of these circuit designs. Its importance has been re recognized, and its market demand is also increasing.

Fast Recovery Diodes, also known as power semiconductor devices, serve as a bridge between weak current control and strong current operation, as well as between information technology and advanced manufacturing. They are an important foundation for the national economy. With the increasing demand for energy conservation and emission reduction in various countries around the world, power semiconductor devices have moved from traditional industrial control and 4C (communication, computer, consumer electronics, and automotive) leading industries to many industries such as new energy, rail transit, smart grids, and variable frequency household appliances.

Among various power semiconductor devices, power diode is a relatively simple device, but it is the most widely used component in power electronic circuits and plays a crucial role in the circuit. Its performance directly affects the rationality of circuit design and the reliability of circuit operation.

However, with the development of power electronics technology towards lightweight, miniaturization, intelligence, and energy-saving, the application of various control circuits (such as frequency conversion circuits and chopper circuits) continues to expand. Whether the main circuit in these power electronics circuits uses thyristor with commutation and shutdown, or new power electronic devices with self shutdown capability, such as GTO, power VDM0S, IGBT, etc., all require a fast recovery diode in parallel with it, To reduce the charging time of the capacitor by passing the reactive current in the load, while suppressing the high voltage induced by the instantaneous reversal of the load current. This is due to the low ability of IGBT, power VDMOS and other devices to withstand reverse voltage during reverse bias, and the reverse diode in the structure is in a conduction state.

In uninterruptible power supplies and switching power supplies, in order to achieve a smooth waveform with the least harmonics, the switching frequency of the conversion device must be increased as much as possible. But every time the switch is turned on, it generates losses, leading to an increase in the temperature of the device. The cooling capacity usually limits the performance of the conversion device. A well-designed diode plays a significant role in reducing the losses of the converter, and the better the switching characteristics of the diode, the smaller the turn-on losses of the device.

Due to the continuous improvement in frequency and performance of power electronic devices such as IGBT and power VDMOS, in order to match their turn-off process, the diode must have fast turn-on and high-speed turn-off capabilities, namely short reverse recovery time trr, small reverse recovery current IRRM, and soft recovery characteristics，Fast Recovery Diodes。

In high voltage and high current circuits, traditional PIN diodes have good reverse voltage withstand performance, and when biased forward, they can conduct large currents at very low voltages, presenting a low resistance state. However, the presence of minority carriers injected into the forward direction leads to a longer minority carrier lifetime, resulting in a correspondingly lower switching speed of the diode. To improve its switching speed, doping with heavy metal impurities and electron irradiation can be used to reduce minority carrier lifetime. However, this will result in varying degrees of hard recovery characteristics of the diode, causing a higher induced voltage in the circuit, which has a significant impact on the normal operation of the entire circuit. Therefore, developing high-frequency and high-voltage fast soft recovery high-power diodes has become a very important and urgent task, with important practical significance.