List of commonly used circuits for zener diodes

When voltage regulator tube is connected in forward direction, it has same characteristics as a conventional diode.

When Zener tube is connected in reverse, when reverse voltage is less than breakdown voltage, reverse current is very small, and dynamic resistance presented is very large. As a rule, larger operating current, lower dynamic resistance and better voltage stabilization characteristics.

When reverse voltage is greater than breakdown voltage, current flowing through diode increases dramatically, but voltage across it remains almost unchanged, which can be used to stabilize voltage.

Zener tube application

1. Surge protection circuit

The zener diode breaks down at a precise voltage, making it suitable for use as a limiting or protection element, since zener diodes with different voltages are available, so it is especially suitable for this application. Zener diode D is used as an overvoltage protection device. As long as source voltage supply voltage VS exceeds adjustable value D of diode, it will be turned on, so relay J will pull in load RL and disconnect from power supply.

2. TV surge protection circuit

EC is main power supply voltage of TV. When EC voltage is too high, D is turned on, triode BG is turned on, and its collector potential changes from original high level (5V) to low level, through standby control line, TV control enters standby protection state.

3. Arc quenching scheme

If a suitable zener diode is connected in parallel with inductor (it can also be connected to a conventional diode, principle is same), when coil is turned off in a state of conduction, high voltage generated by release of its electromagnetic energy will be absorbed by diode, so when key is turned off, arc of key is also eliminated . This application circuit is widely used in industry, such as some high power electromagnetic suction control circuit.

4. Series voltage regulator circuit

In this circuit, zener tube is connected in series, base of BG is fixed at 13V by Zener diode D, then its emitter will output a constant voltage of 12V. This circuit is used in many cases.

5. In addition to creating a voltage stabilization circuit, voltage regulator tube can also be used as a one-time protection circuit.

For example, in important parts, it is forbidden to increase voltage in order to damage valuable components. You can use a voltage regulator tube to connect back and forth in parallel with power supply. The zener tube quickly exits reverse fault trip state, directly shorts power supply, blows fuse or current-limiting protection resistor, and protects all loads in power branch circuit from being damaged by overvoltage.

Because this type of voltage regulator protection tube is ineffective during normal times, it can be temporarily used for emergency repairs. Experienced service personnel can even obtain local emergency materials and disassemble them as spare parts for maintenance. Use it flexibly.