The function of the Zener diode is to keep the voltage stable. When the power supply voltage fluctuates or other reasons cause the voltage at different points in the circuit to change, the Zener diode can keep the voltage across the load basically unchanged. The series connection at higher voltage can protect the electronic components in the circuit from high current breakdown.
The voltage stabilizing circuit is connected in parallel, and the voltage stabilizing diode VD is connected in parallel at the output end, and the voltage on VD is the output voltage. This kind of voltage stabilization parallel connection is mainly used in occasions where the input voltage change is small and the load current is small. Series voltage regulator circuit. Since the base voltage of the regulator tube VT connected in series in the output circuit is stabilized by the Zener diode VD, when the output voltage changes, the base-emitter voltage of the regulator tube VT changes accordingly, causing the tube voltage drop of VT to be opposite. The direction changes to keep the output voltage basically stable.
Zener diodes can be used as voltage reference components or regulators. Zener diodes can protect the electronic components in the circuit from high current breakdown. Zener diodes can be connected in series for use at higher voltages, and higher stable voltages can be obtained by connecting them in series. In addition to forming a voltage regulator circuit, the Zener diode can also be used as a one-time protection circuit. For example, in important parts, boosting is prohibited to damage valuable equipment, and the Zener tube can be connected in reverse parallel with the power supply at this part. When the power supply voltage suddenly rises due to a fault and exceeds the voltage stabilization value of the zener diode, the zener diode quickly changes from the off state to reverse breakdown, directly short-circuits the power supply, blows the fuse or current-limiting protection resistor, and protects the power supply branch. All the loads are not damaged by overvoltage.
Zener diodes are classified into metal packaging, glass packaging and plastic packaging according to the packaging material of the housing. There are two types of plastic package Zener diodes: lead type and surface mount. According to the internal structure, it is divided into ordinary Zener diode (2 leads) and temperature compensation type Zener diode (3 leads). According to the current capacity, it can be divided into high-power Zener diode (above 2A) and low-power Zener diode (less than 1.5A).