1. Fast recovery diode
Recovery diode, referred to as FRD, is a semiconductor diode with good switching characteristics and short reverse recovery time. It has unidirectional conductivity like ordinary diodes. It is mainly used in switching power supplies, pulse width modulators, inverters and other electronics. In the circuit, it is mainly used as a high-frequency rectifier diode, a freewheeling diode or a damping diode.
1. Application of fast recovery diodes in relays
As shown in the figure below, a UF4007 is connected in parallel at both ends of the relay, its reverse repetitive peak voltage is 1000V, and the forward surge current is 30A. The relay coil can store energy. Once the coil is de-energized, a large reverse electromotive force will be generated at both ends of the coil. If a fast recovery diode is connected in parallel at both ends of the coil, it will generate a loop through which the electromotive force will store the coil. Of energy release.
2. Application of fast recovery diode in IGBT switch tube
The following figure shows the LC oscillation circuit controlled by the full bridge of the induction cooker. Q1-Q4 are connected to each other. During the on-off process, energy will be generated. This diode is often called a parasitic diode or a freewheeling diode. When the IGBT is used as a switch Generally, the voltage reaches thousands of volts, so Schottky diodes are not suitable.
3. Fast recovery diodes are used in switching power supply applications such as BOOST boost
1) The following figure shows the BOOST boost circuit, FR154 is a 400V/1.5A fast recovery diode, which can prevent current backflow
2) Applied in the clamp absorption circuit such as RCD, as shown in the figure D1/UF4007 and R1, C2 form an absorption circuit
2. Schottky diode
The Schottky diode, abbreviated as SBD, is not made by the principle of PN junction. It is made by using metal as the anode and N-type semiconductor as the cathode. The barrier formed on the contact surface of the two has rectification characteristics. A semiconductor device is a hot carrier diode. Schottky diodes are mainly used in circuits as rectifier diodes, freewheeling diodes, protection diodes, etc., and are mainly used in low-voltage, high-current circuits, such as switching power supplies, Frequency converter, inverter, microwave communication
1. Application of Schottky diode in switching power supply
As shown in the figure below, the switching power supply rectifier adopts D1 and D2 as the rectifier pair MBR20150CT (20A 150V), which can reduce the loss of the secondary winding and the rectifier to a certain limit.
Third, the characteristics of fast recovery diodes and Schottky diodes
1. The reverse recovery time of fast recovery diodes is several hundred nanoseconds, while Schottky diodes are faster than it, even several nanoseconds;
2. The reverse breakdown voltage of fast recovery diodes is high, generally higher than 200V, or even several thousand volts, while the reverse breakdown voltage of Schottky diodes is very low, generally below 100, and some will be higher;
3. The power consumption of fast recovery diodes is relatively large, while Schottky diodes have short reverse recovery time, low loss and low noise.
