When the regulator diode works in the reverse breakdown state, the voltage at both ends is basically unchanged. Using this property, in the circuit is often used to form a voltage regulator circuit.
Voltage regulator diode composed of voltage regulator circuit, although the stability is not very high, but it has the advantages of simple, economic and practical, so it is widely used.
In the actual circuit, to use a good voltage regulator diode, should pay attention to the following problems.
1, to pay attention to the general diode and voltage regulator diode difference method. Many general diodes, especially glassed tubes, shape color and voltage regulator diode more similar, such as not careful distinction, will use the wrong. The distinguishing method is: look at the shape, a lot of stabilized diodes for a cylindrical column, shorter and thicker, and the general diode if the cylindrical column is more slender; Look at the sign, the outside surface of the stable voltage diode is marked with a stable voltage value, such as 5V6, indicating that the stable voltage value is 5.6V; Use multimeter to measure, according to the unidirectional conductivity, use measured diode X1K block is the first of the positive and negative polarity judgment, and then use X10K block, black pens and diode cathode, red pens and diode cathode, compared to measure resistance and X1K block, if appear reverse resistance value is large, for the possibility of general diode is very large, if the reverse resistance is small, for the zener diode.
2. Pay attention to the difference between forward use and reverse use of voltage stabilizing diode. The voltage at both ends is basically unchanged after the forward guide pass, which is about 0.7V. Theoretically speaking, the voltage regulator diode can also be used forward to do voltage regulation pipe, but its voltage regulator value will be less than 1V, and the voltage regulator performance is not good, generally do not use the regulator tube's positive guide characteristic to stabilize the voltage, but the reverse breakdown characteristic to stabilize the voltage. The reverse breakdown voltage is the voltage regulator. Sometimes the use of two voltage regulator tube in series, one USES its forward characteristics, the other USES its reverse characteristics, can not only stabilize the pressure and can play the role of temperature compensation, in order to improve the stabilizing effect.
3. Pay attention to the effect of current limiting resistance and the influence of resistance value. In the regulator diode regulator circuit, a series resistor R is generally connected, as shown in Figure 1 or 2. The resistance plays a role in limiting current and improving voltage stabilization in the circuit. If this resistance is not added, when R=0, it is easy to burn out the stabilizing tube, and the stabilizing effect will be extremely poor. The greater the resistance value of the current-limiting resistor is, the better the voltage regulation performance of the circuit will be, but the pressure difference between input and output will be too large, and the power consumption will be more.
4. Pay attention to the pressure difference between input and output. Normal use, zener diode voltage stabilizing circuit of the output voltage is equal to the voltage at the ends of the pipe after the reverse breakdown voltage value, if the input to the voltage regulator circuit in the voltage value less than the regulated value of voltage regulator tube, the circuit will lose voltage stabilizing effect, only is greater than the relations, is regulated, and the pressure difference, the greater the resistance of the resistor should be, otherwise it will damage the regulator tube.
5. The regulator tube can be used in series. After several regulator tubes are connected in series, several different regulator values can be obtained, so it is common to use in series. The following is an example of how to obtain the voltage regulator after two regulator tubes are used in series. If the regulator value of one tube is 5.6V and that of another is 3.6V, and the voltage when the regulator tube is set to pass through the forward guide is 0.7V, then there are four different regulator values in series, as shown in Figure 1.
6. The regulator tube is generally not used in parallel. After several regulator tubes are connected in parallel, the regulator value will be determined by one of the lowest values (including the voltage after the positive guide pass). Take the above two voltage regulator as an example to illustrate the calculation method of voltage regulator. After two parallel, there are four cases, the stable voltage value is only two. The regulator diodes are not used in parallel except under special circumstances.
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