The forward characteristic of the volt-ampere characteristic curve of a Zener diode is similar to that of an ordinary diode. The reverse characteristic is that when the reverse voltage is lower than the reverse breakdown voltage, the reverse resistance is large and the reverse leakage current is extremely small. However, when the reverse voltage approaches the critical value of the reverse voltage, the reverse current suddenly increases, which is called breakdown. At this critical breakdown point, the reverse resistance suddenly drops to a very small value. Although the current changes in a wide range, the voltage across the diode is basically stable near the breakdown voltage, thus realizing the diode's voltage stabilization function.
Stable voltage refers to the stable voltage value generated at both ends of the Zener diode when the rated current passes. This value varies slightly with operating current and temperature. Due to different manufacturing processes, the voltage stabilization values of the same type of zener tubes are not completely consistent. For example, the Vzmin of the 2CW51 regulator is 3.0V and the Vzmax is 3.6v. The rated current refers to the current value flowing through the diode when the Zener diode generates a stable voltage. Below this value, although the regulator cannot stabilize the voltage, the stabilization effect will be worse. Above this value, as long as the rated power loss is not exceeded, it is also allowed. The voltage regulation performance will be better, but more power will be consumed.
The dynamic resistance is the ratio of the voltage change and the current change across the Zener diode. The ratio varies with the operating current. Generally, the larger the operating current, the smaller the dynamic resistance. For example, when the operating current of the 2CW7C voltage regulator is 5mA, Rz is 18ω. When the operating current is 1mA, Rz is 8ω. When it is 20mA, Rz is 2ω; 20mA basically maintains this value. The rated power consumption is determined by the allowable temperature rise of the chip, and its value is the product of the stable voltage Vz and the maximum allowable current Izm. For example, if the Vz of the 2CW51 Zener diode is 3V and Izm is 20mA, the Pz of the tube is 60mWo.
Under the specified reverse voltage, the reverse leakage current generated by the teacher's Zener diode. For example, when the voltage of the 2CW58 regulator is 1 volt, infrared radiation = 0.1 A; when VR = 6V, IR = 10uA. The breakdown of the Zener diode is mainly manifested as open circuit, short circuit and unstable voltage regulation value. Among the three types of failures, the first type of failure indicates an increase in power supply voltage. The latter two faults are manifested as the power supply voltage drops to zero volts or the output is unstable.
The difference between the positive and negative poles can be seen from the outside. One end of the anode of the metal-encapsulated Zener diode tube is flat, and the other end of the cathode is semicircular. One end of the plastic sealed Zener diode body with color marks is the negative electrode, and the other end is the positive electrode. For zener diodes with unclear markings, the polarity can also be determined with a multimeter. The measurement method is the same as that of ordinary diodes, that is, use a multimeter R×1k, connect two probes to the two electrodes of the Zener diode, measure a result, and then switch the two probes to measure. In the two measurement results, the black probe is connected to the anode of the Zener diode, and the red probe is connected to the cathode of the Zener diode for the smaller resistance value. This refers to an analog multimeter.
The above explanations are the functions and parameters of Zener diodes. I hope it will be helpful to you after reading them. If you want to know more about Zener diodes, please contact customer service online or call our company's service hotline. (Upper right corner of the website) For consultation, we will be happy to provide you with quality service!