The key function of the Zener diode is to obtain a lower output voltage Vo from a higher input working voltage Vi, which is not described here: obtain a lower stable output voltage Vo from a higher unstable input working voltage Vi . Although Zener diodes have a certain voltage stabilizing effect, this type of voltage stabilization ability is not suitable for places with high precision requirements. In most specific application power circuits, a large number of Zener diodes are used to obtain a precise The degree of regulation is not too high a working voltage value.
When the input power supply voltage Vi is lower than the steady working voltage VZ of the Zener diode, the Zener diode does not penetrate and is in the opposite direction cut-off zone. At this time, there is only a relatively small amount of reverse current IR in the power circuit control loop. This kind of operation state is not all normal operation states of Zener diodes. Because the output voltage Vo changes with the input working voltage Vi, the goal of outputting a stable working voltage is not achieved.
When the input power supply voltage Vi is higher than the steady working voltage ZT of the Zener diode, the Zener diode is penetrated by the working voltage in the opposite direction, and the current in the control loop is greatly increased. The output voltage Vo at this time is the allowable and stable working voltage of the Zener diode, that is, the required operating voltage value for everyone, and the current in the control loop is the current IZ of the Zener diode. Among them, the resistor R is the current limiting resistor of the Zener diode. The minimum amount of current IZ that can make the Zener diode enter the voltage stabilization situation is also called the knee point/turning point current IZK. Therefore, the resistor R value should not be very large, so how much should the minimum value of this resistor be suitable? ?
When the input power supply voltage Vi is increased again, the steady working voltage VZ (that is, the output voltage Vo) of the Zener diode will have a certain change, but it is not as large as the input working voltage Vi, because the Zener diode is in the opposite direction. In the case of through-regulation, the errors between the input working voltage Vi and the output voltage Vo are released to both sides of the resistor R, which in turn causes the current in the control loop to increase.
The Zener diode itself does not have the main parameter of the maximum reverse working voltage, but it will have a certain functional loss, that is, the stable operating voltage VZ of the Zener diode and the amount of current IZ passing through the Zener diode are multiplied. The stable operating voltage VZ of the Zener diode is the rated value, so the functional loss can also be indicated by the larger functional loss or the larger working current IZM. This value is also obtained in many data information guides. When the control loop current IZ exceeds the larger working current IZM of the Zener diode (that is, exceeds the maximum allowable output power loss of the diode), the Zener diode will be destroyed due to over-temperature, and the output voltage Vo at this time is entered The working voltage Vi, that is, no longer has the ability to stabilize. Therefore, when we set the minimum value of the resistor R, we should manipulate the current of the Zener diode to be within IZM.
The above explanation is about the voltage stabilization function of Zener diodes. I hope it will be helpful to you after reading. If you want to know more about Zener diodes, please contact customer service online or call our company’s service hotline. (Upper right corner of the website) For consultation, we will be happy to provide you with quality service!