The input voltage of the regulator tube is high, how to reduce the voltage?

Simple. 1- Try to make the transformer output DC, it is recommended to use bridge rectification. Let the rectifier output voltage be V

2- Understand or actually test the current required by the load at the output of the 7812, set to i3- Connect a resistor between the rectifier output and the 7812 input with a magnitude of (V-15) i

Power dissipation selection of resistors.

4- Be sure to add a heat sink to the 7812 with a power of 3i

The voltage is too high, more than twice as much, change the transformer!

I make it simple. 7812 is not used either. Directly connect a 300 ohm winding resistance of 2W, and then connect a 4742.

The 4742 is a 12C regulated diode. Probably meta. The winding resistance is also elemental.

The total ** talent yuan is much cheaper than 7812. ）

You're a little misunderstood! The regulated voltage value of a semiconductor regulator diode (avalanche diode) is exactly its reverse avalanche breakdown voltage value! Its forward voltage drop is the same as that of a normal diode! (Silicon tubes!) Germanium tubes! It's not regulated with a positive voltage drop!

The important indicator of a Zener diode is not only its regulation value! Its maximum regulated operating current (maximum avalanche current) is important!

In practice, it is best not to exceed 2 times the maximum input voltage of its regulated voltage!

The forward voltage drop of the regulator tube refers to the forward voltage drop of the diode under the specified forward current of the regulator tube, which is the lowest forward voltage that the diode can conduct.

When the regulator tube is matched with the reverse breakdown ridge, the terminal voltage is almost unchanged in a certain current range (or in a certain power loss range), showing the characteristics of voltage regulation, and it is widely used in voltage regulator power supply and limiting circuit because of its cautiousness.

Regulator diodes are binned according to breakdown voltage, and because of this characteristic, the regulator main is used as a regulator or voltage reference element. Forward voltage drop: The forward voltage drop of a diode at a specified forward current.

A voltage regulator can solve your problem!

Start by determining your actual power: That's it.

This voltage fluctuation is relatively large, but it is still within the range of use of the voltage regulator.

The 001 or HN regulator has a TMA model, and the input voltage range is 130-270V, which means that it can be used as long as it is within this range, which matches your voltage situation.

The attributes of the voltage regulator, the most direct is the voltage stabilization, because the electrical appliances are required to use normally, the voltage is low can not be used, and the voltage is high There is a hidden danger of burning out, so the voltage regulator is a product.

As long as the input voltage is within the required range, the voltage regulator can achieve a positive or negative percentage output of 220V, for example, the above TMA regulator can achieve a voltage output of 220+-10%, that is, a voltage output of 198-242V.

If you want to buy a voltage regulator, you should consider the use of load, if it is a load with air conditioning, motor, etc., you should make the load energy power x3.

Hope the above helps.

The ** that can be selected is around 300.

Yes, the forward direction is equivalent to an ordinary diode, and the reverse direction is the voltage stabilization.

In electronic circuits, the positive pole of the diode is connected to the high potential end and the negative terminal is connected to the low potential end, and the diode will be turned on, and this connection method is called forward bias. It must be noted that when the forward voltage applied to both ends of the diode is very small, the diode still cannot be conducted, and the forward current flowing through the diode is very weak. Only when the forward voltage reaches a certain value (this value is called the "threshold voltage", which is about germanium and silicon), can the diode be turned on straight.

The voltage across the diode remains essentially the same after turn-on (about germanium tubes, about silicon tubes, and is called the "forward voltage drop" of the diode).

What is the forward pressure drop of the regulator tube? 】

Is it a regulator diode?

Pressure drop. It is 225V, "the regulator tube itself works in the reverse breakdown zone, and only when this voltage is reached can it start working, so that the output voltage is its regulated value."

Regulator Tube: Regulator diode.

Also known as Zener diode.

It is a kind of surface contact crystal diode made of silicon material, referred to as voltage regulator tube. This diode is a semiconductor device that has a very high resistance until the critical reverse breakdown voltage. When the regulator tube is in reverse breakdown, the terminal voltage is almost unchanged in a certain current range (or in a certain power loss range), showing voltage stabilization characteristics, so it is widely used in voltage regulator power supply and limiting circuit.

Zener diodes are binned according to the breakdown voltage, and because of this characteristic, they are mainly used as voltage regulators.

The 100-degree boy is right: "The regulator itself works in the reverse breakdown zone, and only when this voltage is reached can it start working, so that the output voltage is ,...... its regulated value."

But I guess what you might be asking is: what happens if the applied voltage is less than that?

The applied voltage is less than this voltage. It does not break down, and the current is equal to zero. And the voltage, how much voltage is added, how big is the maximum. It is equivalent to an open circuit.

This question asks, the regulator tube itself is working in the reverse breakdown area, only when this voltage is reached, it can start to work, so that the output voltage is its voltage stabilization value, different voltage regulator diodes have different voltage stabilization values, if you continue to add a rising voltage to it, then it will only make the output current rise a lot, when you add the voltage exceeds the maximum working voltage of the voltage regulator diode, the diode will be due to the output current is too large and the heating temperature is too high and permanently breakdown and burn out;

On the contrary, if you add a forward bias voltage, then the regulator tube is equivalent to an ordinary diode, as long as it is greater than the dead zone voltage, it can work, but there is no voltage regulation characteristic, people will not use it like this, because the cost of using a regulator tube as an ordinary diode is too high.

A voltage regulator is also a crystal diode, which uses the breakdown zone of the PN junction to have a stable voltage to work. Voltage regulator tubes are widely used in voltage regulator equipment and some electronic circuits. This type of diode is called a regulator to distinguish it from diodes used in rectification, detection, and other unidirectional conduction applications.

The characteristic of a Zener diode is that the voltage at both ends of the diode remains basically unchanged after breakdown. In this way, when the regulator tube is connected to the circuit, if the voltage at each point in the circuit fluctuates due to the fluctuation of the power supply voltage or other reasons, the voltage at both ends of the load will basically remain the same. The volt-ampere characteristics and symbols of the regulator tube are depicted in the figure.

After the reverse breakdown of the regulator tube, although the current changes in a wide range, the voltage at both ends of the regulator tube changes very little. Taking advantage of this characteristic, the regulator can play a role in stabilizing the voltage in the circuit. Because of this characteristic, regulators are mainly used as voltage regulators or voltage reference components.

Strictly speaking, the three-terminal regulator is an integrated circuit, and the output voltage is compared with the internal reference voltage and the drive regulator is adjusted to a stable value. Individual components can be roughly damaged by measuring the resistance between the pins with a multimeter, preferably in the connected circuit. Indicators such as voltage regulation and ripple can only be tested with professional instruments.

Qualitative inspection with an oscilloscope can also be used in amateur conditions.

A voltage regulator is also a crystal diode, which uses the breakdown zone of the PN junction to have a stable voltage to work. Voltage regulator tubes are widely used in voltage regulator equipment and some electronic circuits. We refer to this type of diode as a regulator to distinguish it from diodes used in rectification, detection, and other unidirectional conduction applications.

1) Stable voltage uz uz is the breakdown voltage of the PN junction, which varies slightly with the difference of operating current and temperature. For the same type of regulator tube, the voltage regulation value has a certain discreteness.

2) Stable current iz The reference current value when the regulator tube is working. It usually has a certain range, i.e., izmin – izmax.

3) Dynamic resistance rz It is the ratio of voltage change to current change at both ends of the regulator tube, as shown in the figure above, that is, this value changes with the difference of working current. In general, the higher the operating current, the smaller the dynamic resistance, and the better the voltage regulation.

4) Voltage temperature coefficient It is used to explain the coefficient by which the stable voltage value is affected by temperature changes. Different types of regulator tubes have different temperature coefficients of stable voltage, and there are positive and negative points. For regulators with a voltage stabilization value lower than 4V, the temperature coefficient of the stabilized voltage is negative; For a regulator with a voltage stabilization value higher than 6V, the temperature coefficient of the stabilized voltage is positive; Between 4V and 6V, it may be positive or negative.

In demanding cases, it can be compensated with two tubes with opposite temperature coefficients in series (e.g. 2dw7).

5) The rated power consumption pz has been pointed out before, the larger the working current, the smaller the dynamic resistance, and the better the voltage regulation, but the maximum working current is limited by the rated power consumption pz, and exceeding pz will damage the voltage regulator tube.

Check that the measuring instrument is accurate and that the input voltage is still unchanged at 26V. The Zener voltage value of the Zener diode will not change so much, even if there is a certain change in temperature, there will be no such situation, the most likely factor to cause the voltage change of the regulator tube is the working current, if the resistance value of the 1k resistance in the figure is greatly reduced (such as changing to 100), the stable voltage of the regulator tube will be significantly increased.

Poor thermal stability of a Zener diode, or a poor thermal stability of a triode, will cause a change in the output voltage. You should be aware that this is a simple type of voltage regulator circuit, not a precision type. It is enough to meet the general application.

To be precise, use devices such as 431 or 317.

Maybe it's due to the temperature.

You're not doing it the right way. The negative end of the regulator tube is connected to 12V in series with a current limiting resistor, and the positive end of the regulator tube is grounded. When measuring, the black pen of the multimeter is grounded, and the red pen is connected to the junction of the resistance and the negative end of the regulator tube.

When the reverse voltage is added to a certain value, the reverse current increases sharply, and the long-term reverse breakdown occurs, at this time there is a repercussion breakdown voltage, and the stable voltage of the voltage regulator tube. The function of the regulator tube is that when the current increment is large, it only causes a small voltage change, which means that the voltage is basically constant.

In the circuit, the voltage regulator tube usually plays the role of stabilizing the DC voltage, making the circuit work in a suitable state, and limiting the working current in the circuit.

That's pretty much it.