Zener diode: Q8 M, w5 U7. Zener diodes are often represented by "ZD" plus numbers in the circuit, such as: ZD5 represents the number 5 Zener tube.
1. The principle of voltage stabilization of Zener diode: The characteristic of Zener diode is that after breakdown, the voltage at both ends remains basically unchanged. In this way, when the voltage regulator tube is connected to the circuit, if the voltage of each point in the circuit fluctuates due to fluctuations in the power supply | voltage regulator voltage, or other reasons, the voltage across the load will basically remain unchanged.
2. Fault characteristics: The faults of the Zener diode are mainly manifested in open circuit, short circuit and unstable voltage regulation. Among these three types of faults, the first type of fault shows an increase in power supply voltage; the latter two types of faults show a change in power supply voltage. Low to zero volts or unstable output.
SMD Zener diode package:
LL4148 LL34 2.2V LL34—75V LL34 (1/2W glass), 3.3V—56V LL41 (1W glass)
2.2V—75V voltage regulator series
The models and voltage regulation values of commonly used Zener diodes are as follows:
Voltage regulation value:3.3V、3.6V、3.9V、4.7V、5.1V、5.6V、6.2V、15V、27V、30V、75V