1. TVS diode (transient voltage suppressor)
In the circuit, the TVS diode is connected to the power supply in the reverse direction. Once the instantaneous voltage exceeds the normal working voltage of the circuit, the TVS diode will have an avalanche effect, providing an ultra-low instantaneous current. Resistance path, so as to avoid damage to the protected device or equipment.
figure 1
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figure 2
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I found a picture on the Internet. Let me start with the conclusion. Picture 2 is better than Picture 1. Because there are two diodes in these two figures, they are used to prevent reverse connection of the power supply and prevent static electricity. When a negative voltage surge comes, if it is shown in Figure 1, the anti-reverse diode is directly sacrificed, while in Figure 2, the TVS diode is avalanche breakdown, and the short circuit plays a protective role, so that the anti-reverse diode will not be damaged. In addition, the fuse should be connected behind the diode, because the design idea of bleeder components is to rush forward and resist positively. And the thicker the blood, the more he must rush forward. There are gas discharge tubes, varistors, and TVS. The gas discharge tube has the largest current, which is of lightning protection level, but the action is very slow, so you should stand in the forefront. The varistor can also flow too much current, but it is self-sacrifice, a little bit later. TVS has the fastest response speed, but the overcurrent is small, so it will hide at the end, eat some fast, but low energy hazards, such as static electricity. Then there are the fuses, anti-reverse diodes, capacitor resistors, filter circuits, etc., these devices that store negative energy by themselves.
2. Zener diode
as shown below, the base of transistor T is stabilized at 13V by Zener diode D, then its emitter will output a constant voltage of 13-0.7=12.3V, within a certain range, regardless of whether the input voltage rises or Decrease, no matter the load resistance changes, the output voltage remains the same. This circuit has applications in many occasions. The 7805 is a series integrated voltage regulator circuit that can output a voltage of 5V. 7805-7824 can output 5-24V voltage. It has applications in many electrical appliances.
3. Schottky diodes
are generally used for freewheeling and anti-reverse connection.