Let's talk about how transient suppression diodes regulate voltage

Let's talk about how transient suppression diodes regulate voltage

Everyone knows very well that the role of the transient suppression diode is to effectively stabilize the voltage, thereby protecting the equipment in the circuit from high voltage, so how does it regulate the voltage? It uses the reverse breakdown characteristic to stabilize the voltage. When the voltage is high, it breaks through and leads to ground, and when the voltage is low, it does not break down. The transient suppression diode is used in reverse, and the regulator diode, also known as the Zener diode, maintains a high resistance value when used in reverse, and the resistance becomes sharply smaller and close to zero when the breakdown voltage is reached. (To limit the current)

    The state of the transient suppression diodes at reverse breakdown: Reverse breakdown generally has two states: avalanche breakdown and Zener breakdown. Avalanche breakdown is when the reverse voltage of the PN junction increases to a value, and the carrier doubling is like an avalanche, increasing much faster and faster.  Zener breakdown is a strong electric field in the PN junction at high reverse voltage, breaking the covalent bond in the conductor will form electron-hole pairs, forming large reverse currents. Zener breakdown requires a lot of electric field strength! This can only be done in PN junctions with a large concentration of impurities. (The large impurity, the greater the charge density). PN junction reverse breakdown has Zener breakdown and avalanche breakdown, generally both kinds of breakdown exist at the same time, but the breakdown when the voltage is lower than 5-6V is mainly Zener breakdown, and the breakdown when the voltage is higher than 5-6V is mainly avalanche breakdown.

    The difference between the two for the stabilized diode is mainly:

    transient suppression diodes with voltages below 5-6V, Zener breakdown is dominant, and the temperature coefficient of the regulated value is negative. For voltage regulators with voltages higher than 5-6V, avalanche breakdown is the mainstay, and the temperature coefficient of the regulator tube is positive. Sometimes the two regulator tubes are connected in series in reverse to compensate for the temperature coefficient, and such a regulator tube is connected to the circuit without distinguishing between positive and negative. The regulator tube is generally small in power and is only used as a regulator reference, and a single regulator tube is used to regulate the voltage when a small current is required.