How are zener diodes different from ordinary diodes

How are zener diodes different from ordinary diodes

zener diodes differ from ordinary diodes in terms of parameters, principles, and functions.

Different parameters

The dynamic resistance of a diode is the ratio of the change in voltage near the static operating point Q of the diode characteristic curve to the corresponding change in current.

The dynamic resistance of a voltage regulator diode refers to the ratio of the voltage change at both ends of the voltage regulator to the current change. The ratio changes with different working currents, generally the higher the working current, the smaller the dynamic resistance. For example, when the working current of the 2CW7C voltage regulator is 5mA, Rz is 18 Ω; When the working current is 1 OmA, Rz is 8 Ω; At 20mA, Rz is 2 Ω;> 20mA basically maintains this value.

The principle is different 

A crystal zener diodes is a pn junction formed by p-type and n-type semiconductors, which forms a space charge layer on both sides of its interface and has a self built electric field. When there is no applied voltage, the Diffusion current caused by the carrier concentration difference on both sides of the pn junction is equal to the Drift current caused by the self built electric field and is in electric balance.

When there is a positive voltage bias outside, the mutual suppression of the external electric field and the self built electric field makes the Diffusion current of the carrier increase, resulting in a positive current. When there is a reverse voltage bias outside, the external electric field and the self built electric field further strengthen, forming a reverse Saturation current I0 within a certain reverse voltage range that is independent of the reverse bias voltage value.

The reverse characteristic of a voltage regulator diode is that when the reverse voltage is lower than the reverse breakdown voltage, the reverse resistance is high and the reverse leakage current is minimal. However, when the reverse voltage approaches the critical value of the reverse voltage, the reverse current suddenly increases, known as breakdown. At this critical breakdown point, the reverse resistance suddenly drops to a very small value. Although the current varies over a large range, the voltage at both ends of the diode is basically stable near the breakdown voltage, thus achieving the diode's voltage stabilizing function.

The effect is different

The functions of zener diodes include rectification circuits, detection circuits, voltage stabilizing circuits, and various modulation circuits, all of which are mainly composed of diodes.

Voltage stabilizing zener diodes, overvoltage protection circuits, arc suppression circuits, etc. in televisions.

For example, in the overvoltage protection circuit of a TV, 115V is the main power supply voltage of the TV. When the output voltage of the power supply is too high, D is turned on, and the transistor T is turned on. Its collector potential will change from the original high level (5V) to low level, and the voltage of the standby control line will put the TV into a standby protection state