Fast Recovery Diode Manufacturer

What are fast recovery diodes?

Fast recovery diode (FRD for short) is a semiconductor diode with good switching characteristics and short reverse recovery time. It is mainly used in electronic circuits such as switching power supplies, PWM pulse width modulators, and frequency converters. Freewheeling diodes or damping diodes are used. The internal structure of the fast recovery diode is different from the ordinary PN junction diode. It belongs to the PIN junction diode, that is, the base region I is added between the P-type silicon material and the N-type silicon material to form a PIN silicon chip. Because the base region is very thin and the reverse recovery charge is very small, the reverse recovery time of the fast recovery diode is short, the forward voltage drop is low, and the reverse breakdown voltage (withstand voltage) is high.

Classification of fast recovery diodes

High-power fast recovery diodes packaged in TO-220 or TO-3P, available in single and double tubes. The pin lead-out method of the double tube is divided into common anode and common cathode.
Application topology:

Performance characteristics of fast recovery diodes

The definition of reverse recovery time (tr): the time interval during which the current passes through the zero point and changes from the positive direction to the specified low value. It is an important technical index to measure the performance of high-frequency freewheeling and rectifying devices. The waveform of the reverse recovery current is shown in Figure 1. IF is the forward current, and IRM is the maximum reverse recovery current. Irr is the reverse recovery current, usually stipulated Irr=0.1IRM. When t≤t0, forward current I=IF. When t>t0, because the forward voltage on the rectifier suddenly changes to the reverse voltage, the forward current decreases rapidly, and at the time t=t1, I=0. Then the reverse current IR flows through the rectifier device, and IR gradually increases; The maximum reverse recovery current IRM value is reached at t=t2. Afterwards, under the action of the forward voltage, the reverse current gradually decreases and reaches the specified value Irr at t=t3. The reverse recovery process from t2 to t3 has similarities with the capacitor discharge process.

Structural characteristics of fast recovery diodes
The internal structure of the fast recovery diode is different from that of ordinary diodes. It adds a base region I between the P-type and N-type silicon materials to form a P-I-N silicon wafer. Because the base area is very thin, the reverse recovery charge is very small, which not only greatly reduces the trr value, but also reduces the transient forward voltage drop, so that the tube can withstand a high reverse operating voltage. The reverse recovery time of fast recovery diodes is generally hundreds of nanoseconds, the forward voltage drop is about 0.6V, the forward current is several amperes to several thousand amperes, and the reverse peak voltage can reach hundreds to several thousand volts. The reverse recovery charge of the ultrafast recovery diode is further reduced, making its trr as low as tens of nanoseconds. Fast recovery and ultra-fast recovery diodes below 20A are mostly packaged in TO-220. From the perspective of internal structure, it can be divided into two types: single tube and paired tube (also known as double tube). There are two fast recovery diodes inside the pair of tubes. According to the different connection methods of the two diodes, there are common cathode pair tubes and common anode pair tubes. Figure 2(a) is the shape and internal structure of the C20-04 fast recovery diode (single tube). Figures (b) and (c) respectively show the shape and structure of C92-02 type (common cathode paired tubes) and MUR1680A type (common anode paired tubes) ultra-fast recovery diodes. They are all packaged in TO-220 plastic, and the fast recovery diodes of tens of amperes are generally packaged in TO-3P metal shell. Tubes with larger capacity (hundreds of amps to thousands of amps) are packaged in the form of bolts or flat plates.

Reverse recovery time of fast recovery diode
The measurement circuit is shown in Figure 3. The specified IF is supplied by the DC current source, and the pulse generator adds the pulse signal through the DC blocking capacitor C. The trr value observed by the electronic oscilloscope is the time elapsed from the moment I=0 to the moment IR=Irr. Assuming that the reverse recovery charge inside the device is Qrr, there is a relationship:
trr≈2Qrr/IRM (5.3.1)
It can be known from formula (5.3.1) that when the IRM is constant, the smaller the reverse recovery charge is, the shorter the reverse recovery time will be.
Routine detection method
Under amateur conditions, a multimeter can be used to detect the unidirectional conductivity of the fast recovery and ultra-fast recovery diodes, as well as whether there are open circuit or short circuit faults inside, and the forward voltage drop can be measured. If it is equipped with a megohmmeter, it can also measure the reverse breakdown voltage. Example: Measure a C90-02 ultra-fast recovery diode, its main parameters are: trr=35ns, Id=5A, IFSM=50A, VRM=700V. The appearance is the same as figure (a). Turn the 500-type multimeter to the R×1 position, and read the forward resistance as 6.4Ω, n'=19.5 divisions; the reverse resistance is infinite. Further obtain VF=0.03V/grid×19.5=0.585V. Proof that the diode tube is good.