The structure of the Zener diode is the same as the ordinary diode, and there is a PN junction. Due to different manufacturing processes, when the PN junction is in the reverse breakdown state, the PN junction will not be damaged (the PN junction of ordinary diodes will be damaged). When a Zener diode is used to stabilize the voltage, use this breakdown characteristic . Generally, when the reverse voltage of the diode exceeds its reverse withstand voltage value, the reverse voltage of the diode will be broken down and damaged, but the reverse current of the Zener diode will increase sharply when it reaches its withstand voltage value. As long as the reverse current value does not exceed the maximum allowable current, it can work normally. The reverse volt-ampere characteristic curve is steep and the linearity is good.
When the voltage reaches the adjusted value Uz, the curve is very steep, indicating that when the current flowing through the Zener diode changes, the voltage across the Zener diode remains basically unchanged, that is, within a certain voltage range, the voltage across the Zener diode The voltage remains basically the same as the current flowing through the Zener diode. This is the working principle of the Zener diode, which uses the reverse working characteristic. Because of its voltage stabilization function, it is widely used in many circuits, such as regulated power supply, electronic ignition, DC level conversion, limiter circuit, overvoltage protection circuit, compensation circuit, etc.
Zener diode uses the temperature coefficient of Zener diode in the temperature compensation circuit. In circuits where a complementary Zener diode requires higher voltage stability, especially the influence of temperature on voltage, there are actually two common Zener diodes in this temperature complementary Zener diode. However, their temperature characteristics are opposite. When the temperature rises or falls, the tube voltage drop of one diode decreases, and the tube voltage drop of the other diode increases, so the total tube voltage drop of the two diodes remains unchanged, which plays a role of temperature compensation.
Although the voltage stabilizing diode has a certain voltage stabilizing function, this voltage stabilizing ability is not suitable for occasions requiring high precision. In most practical application circuits, Zener diodes are more for obtaining voltage values with low accuracy requirements. Unlike traditional diodes, when reverse biased, the diode will prevent any current from passing through itself, that is, the cathode becomes more positive than the anode. Once the reverse voltage reaches a predetermined value, the Zener diode will start to conduct reversely. This is because when the reverse voltage applied to the Zener diode exceeds the rated voltage of the device, a process called avalanche breakdown occurs in the semiconductor loss layer, and current starts to flow through the diode to limit the voltage increase.
If the current flowing through the Zener diode increases sharply and reaches the maximum circuit value (usually limited by the series resistance), once it reaches, the reverse saturation current remains fairly constant over a wide range of reverse voltage. The voltage point on the Zener diode at which the voltage is stable is called the "Zener voltage" (Vz). For Zener diodes, the voltage range can be from less than 1 volt to hundreds of volts. During the doping phase of the diode semiconductor structure, the point at which the Zener voltage triggers the current to flow through the diode can be controlled very accurately (the error is less than 1%), so that the diode has a specific Zener breakdown voltage (Vz), such as 4.3V or 7.5 V. This Zener breakdown voltage is almost a vertical straight line on the voltage-current curve.
The above explanation is the difference between Zener diodes and ordinary diodes. I hope it will be helpful to you after reading. If you want to know more about Zener diodes, please contact customer service online or call this Company service hotline (upper right corner of the website) for consultation, we will wholeheartedly provide you with quality service!