I am a creator of silicon regulator diodes and their applications.
Because the output voltage of the rectifier filter circuit changes with the fluctuation of the grid voltage and the change of the load, for the occasion that the voltage is required to be stable, voltage stabilization measures must be taken to ensure that the voltage at both ends of the load is basically unchanged. In general, in addition to stabilizing the AC voltage being rectified, the simplest voltage regulation measure is to use a silicon regulator diode to stabilize the voltage.
1. Silicon regulator diode.
1. Silicon voltage regulator diode is a special diode with voltage stabilization effect. Its shape is basically the same as that of an ordinary diode, and the text symbol is often represented by DW. The volt-ampere characteristic curve of a silicon regulator diode is shown in the figure below
*。As can be seen from the curve:
1) The forward characteristics of silicon regulator diodes are the same as those of ordinary diodes.
2) The reverse characteristic curve is steeper than that of ordinary diodes. When the reverse voltage is small, the tube has only a tiny amount of reverse current. When the reverse voltage reaches a certain value, the tube is suddenly turned on, and even a small increase in voltage will cause a large current. This phenomenon is called "breakdown", and uz is called the breakdown voltage (i.e., the stable voltage of the regulator tube). In the reverse breakdown zone, the current of the regulator tube changes in a large range, but the uz is basically unchanged, which is the stabilizing effect of the regulator tube.
2. Since the stabilizer tube is working in the reverse breakdown state, when it is connected to the circuit, it should be reversed, that is, the positive pole of the stabilizer tube should be connected to the negative pole of the stabilized voltage, and the negative pole of the stabilizer tube should be connected to the positive pole of the stabilized voltage. If the polarity of the regulator tube is reversed, it cannot play the expected stabilizing role, and the forward voltage at both ends of the regulator tube is about 07 volts.
Second, the main parameters of silicon regulator diode.
1. Stable voltage uz
In normal operation, the reverse voltage at both ends of the regulator tube. For each tube in a certain type of stabilized tube, their stabilizing voltage is not exactly the same, slightly higher and lower;Therefore, it is usually given a range of the stable voltage value of the tube of this model, such as the voltage range of 2DW7 is 61~6.5 volts.
2. Stabilize the current IZ
The operating current of a stable voltage is maintained.
3. Maximum stable current IZM
It is the maximum working current of the regulator tube. If this current is exceeded, the regulator will overheat and be damaged.
4. Dynamic resistance.
The ratio of the amount of change in electricity to the amount of change in current during normal operation. A small dynamic resistance means that the current can vary over a wide range, while the reverse voltage at both ends of the regulator tube changes very little. Therefore, the smaller the dynamic resistance, the better the voltage stabilization effect of the regulator tube.
3. Silicon voltage regulator tube voltage regulator circuit.
1. Because the silicon regulator tube works in the reverse breakdown zone, the voltage at both ends of the tube is approximately constant within a certain current range, so the voltage regulator tube can be connected to both ends of the load to stabilize the load voltage.
Although the silicon regulator circuit is very simple and low-cost, the output current is small.
Because when the load is open, all the output current will flow through the regulator tube, and if this current exceeds the maximum stable current of the regulator, the regulator tube will be burned out.
The voltage regulator circuit of the silicon regulator tube is shown in the figure below.
In the figure, UR is the DC voltage that needs to be stabilized, R is the current limiting resistor, RFZ is the load resistor, and DW is the silicon voltage regulator.
2. The working process of the circuit is as follows:
1) Set the load resistance RFZ to be fixed. When the input voltage UR increases, the current flowing through the regulator tube increases, and the current flowing through the current limiting resistor R increases accordingly, so that the output voltage (i.e., the voltage at both ends of the load) UC=your-ur remains constant. Similarly, if the input voltage decreases, the voltage across the current-limiting resistor decreases accordingly, ensuring that the voltage across the load remains stable.
2) Set the input voltage ur unchanged. When the load resistance decreases, the load current increases, and the voltage drop across the current limiting resistor increases, the output voltage decreases.
However, a slight drop in the output voltage will cause the current drop flowing through the regulator tube, thereby canceling the voltage change caused by the change of load current on the current limiting resistor, ensuring the stability of the output voltage.
It can be seen that in addition to the voltage regulator tube playing the role of voltage stabilization, the current limiting resistor not only has the effect of limiting the current, but also has the role of voltage regulation, and cooperates with the voltage regulator tube to stabilize the output voltage.