How to choose the diode model and what parameters should be considered when using fast recovery diodes in circuit applications?

How to choose the diode model and what parameters should be considered when using fast recovery diodes in circuit applications?

1. Average rectified current IF: refers to the forward average current allowed to pass through the diode during long-term operation. The current is determined by the junction area and heat dissipation conditions of the PN junction. When using, it should be noted that the average current through the diode should not exceed this value, and the heat dissipation conditions should be met. For example, the IF of the 1N4000 series diode is 1A.

2. Reverse working voltage VR: refers to the maximum reverse voltage allowed to be applied across the diode. If it is greater than this value, the reverse current (IR) will increase dramatically, and the unidirectional conductivity of the diode will be disrupted, causing reverse breakdown. Usually, half of the reverse breakdown voltage (VB) is taken as (VR). For example, the VR of 1N4001 is 50V, and the VR of 1N4007 is 100OV

3. Reverse current IR: It is the reverse current allowed to flow through the diode at the highest reverse operating voltage, and this parameter reflects the unidirectional conductivity of the diode. Therefore, the smaller the current value, the better the quality of the diode.

4. Breakdown voltage VR: refers to the voltage value at the sharp bend point of the reverse volt ampere characteristic curve of a diode. When the reverse is a soft characteristic, it refers to the voltage value under the given reverse leakage current condition.

5. Operating frequency fm: It is the highest operating frequency of the diode under normal conditions. Mainly determined by the junction capacitance and diffusion capacitance of the PN junction, if the operating frequency exceeds fm, the unidirectional conductivity of the diode will not be well reflected. For example, the fm of the 1N4000 series diode is 3kHz.

6. Reverse recovery time tre: refers to the reverse recovery time under the specified load, forward current, and maximum reverse transient voltage.

7. Zero bias capacitor CO: refers to the sum of the capacitance of the diffusion capacitor and the junction capacitor when the voltage across the diode is zero. It is worth noting that due to manufacturing process limitations, even diodes of the same model have significant parameter variability. The parameters given in the manual are often within a range, and if the testing conditions change, the corresponding parameters will also change. For example, the IR of the 1N5200 series silicon plastic encapsulated rectifier diode measured at 25 ° C is less than 1OuA, while at 100 ° C, the IR becomes less than 500uA.

When selecting and purchasing fast recovery diodes, their performance needs to be tested. The specific method is as follows

Measure the two lead wires of the rectifier diode using the 100 × R or 1000 × R ohm range of a multimeter (test the head and tail of the rectifier diode once each). If there is a significant difference in resistance values between two measurements, such as a high resistance value of several hundred thousand Ω and a low resistance value of only a few hundred Ω or even smaller, it indicates that the diode is good (except for diodes that have experienced soft breakdown). If the resistance values measured twice are almost equal and very small, it indicates that the diode has been broken down and cannot be used.