The circuit symbol of the voltage regulator diode (also called Zener diode) is: This diode is a semiconductor device with very high resistance until the critical reverse breakdown voltage. At this critical breakdown point, the reverse resistance is reduced to a very small value. In this low resistance area, the current increases while the voltage remains constant. The voltage regulator diode is divided into grades according to the breakdown voltage. Because of this characteristic, the voltage regulator is mainly used as a voltage regulator or voltage reference element. Its volt-ampere characteristic is shown in Figure 1. The voltage regulator diode can be connected in series for use at higher voltages. By connecting in series, more stable voltage can be obtained. Application of voltage regulator diode: 1. Surge protection circuit (as shown in Figure 2): The voltage regulator breaks down at an accurate voltage, which makes it possible to use it as a limiting or protective element. Since voltage regulator diodes of various voltages are available, they are particularly suitable for this application. The voltage regulator diode D in the figure is used as an overvoltage protection device. As long as the power supply voltage VS exceeds the voltage regulator value of the diode, D will be turned on, causing the relay J to pull in the load RL and separate it from the power supply. 2. Overvoltage protection circuit in TV (as shown in Figure 3): EC is the main supply voltage of TV. When the voltage of EC is too high, D is turned on, transistor BG is turned on, and its collector potential will change from the original high level (5V) to a low level, and the TV will enter the standby protection state through the control of the standby control line. 3. Arc suppression circuit is shown in Figure 4: If a suitable voltage-stabilizing diode is connected in parallel to the inductor (it can also be connected to a common diode with the same principle), when the coil is cut off in the on state, the high voltage generated by the release of its electromagnetic energy is absorbed by the diode, so when the switch is turned off, the arc of the switch is eliminated. This application circuit is used more in industry, such as some high-power electromagnetic suction control circuits. 4. Series voltage regulator circuit (as shown in Figure 5): In this circuit, the base of the series voltage regulator tube BG is clamped at 13V by the voltage regulator diode D, so its emitter outputs a constant 12V voltage. This circuit has application in many occasions .
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