What is a three-terminal regulator? The application and use of a fixed three-terminal regulator
Three-terminal regulator
A three-terminal regulator is a semiconductor device that has a very high resistance up to a critical reverse breakdown voltage. When the voltage regulator tube is in reverse breakdown, within a certain current range (or within a certain power loss range), the terminal voltage is almost unchanged, showing the characteristics of voltage regulation, so it is widely used in regulated power supply and limiter circuits among.
Three-terminal voltage regulator classification:
There are two main types of three-terminal voltage regulators, one with a fixed output voltage, called fixed Output three-terminal Zener tube, another output voltage is adjustable, called adjustable output three-terminal Zener tube.
Principle of three-terminal regulator:
Because the fixed three-terminal regulator is a series voltage regulator circuit, its principle is equivalent to that of the series type Regulator circuit.
Fixed three-terminal regulatorApplication
1. The general products of three-terminal regulator are 78 series ( Positive power supply) and 79 series (negative power supply), the output voltage is represented by the last two numbers in the specific model, and there are 5V, 6V, 8V, 9V, 12V, 15V, 18V, 24V and other grades. The output current is distinguished by adding letters after 78 (or 79). L means 0.1A, M means 0.5A, no letter means 1.5A, such as 78L05 table to find 5V 0.1A.
2. Circuit for increasing the output voltage
3. Dual power supply circuit
Fixed three-terminal regulator Notes on use
Must pay attention when using: the relationship between (VI) and (Vo), take 7805 as an example, the three-terminal voltage regulator The fixed output voltage is 5V, and the input voltage is at least greater than 7V, so that there is a voltage difference of 2-3V and above between the input/output. Make the adjustment tube work in the magnified area. However, when the voltage difference is large, it will increase the power consumption of the integrated block. Therefore, the two should be taken into account, that is, to ensure that the adjustment tube does not enter saturation at the maximum load current, and the power consumption is not too large.
In addition, a diode is generally connected to the input and output of the three-terminal regulator to prevent the charge stored at the output from passing through the regulator when the input is short-circuited, which damages the device.
Usage: The general purpose of the voltage regulator tube and the voltage regulator triode is the same, and they are both used for the voltage regulation of the control board circuit. In order to prevent the circuit from being burned due to excessive voltage.
