What role do diodes play in a circuit

in the rectifier circuit; The use of diodes in series can increase the backpressure tolerance value (generally the sum of the backpressure of all diodes, but it is best to use a diode of the same specification).

in voltage regulator circuits; The diodes are connected in series equal to the sum of the diode regulation values. The parallel use of diodes is theoretically the sum of the rated currents, but considering that absolute symmetry is not possible, it can only be used less than 80% of the sum.

When a diode of the same type is used in series, the reverse voltage is distributed according to the reverse resistance of the diode. Because although each diode has the same model, it is difficult for the reverse resistance to be exactly the same, so the reverse voltage shared by each diode cannot be completely equal, the diode with large reverse resistance shares a large voltage, and the reverse voltage shared by a small reverse resistance is small. In this way, the diode that is subjected to a large reverse voltage may be broken down because its reverse voltage exceeds the limit value, so the entire reverse voltage must be added to the rest of the diodes, causing the other diodes to be overvoltage and broken down one after another.

In order to avoid this phenomenon, a resistor with equal resistance value (called voltage equalization resistance) is connected in parallel on each diode connected in series, so that the resistance value of each group in parallel tends to be equal, so that the reverse voltage tends to be evenly distributed.

The relay coil has a large amount of inductance, and when the external circuit cuts off the coil current, the coil will induce a fairly high voltage at both ends! If the withstand voltage of the transistor pushing it is not high enough, it will break down. After connecting the diode (note that it is in parallel on the **circle instead of series), this induced voltage is released through the diode, and the transistor will not be endangered.

When the relay coil is energized, this diode is in the cut-off state and does not affect the relay operation.

rectification, and also has a depressurizing effect.

The diode has three functions: rectification, limiting and clamping.

Tandem talk about the trace, diode.

The core circuit state is like a posture by PN knots.

composition, as shown in the figure below:

Sometimes more than two diodes need to be used in parallel to increase the rectifier current. (or to increase the ability to pass current). When connected in parallel, it is necessary to pay attention to the withstand voltage value of the two old electrode defectors and the allowable current value of the car containing a single diode.

Sometimes, in order to increase the forward voltage drop value, or the reverse withstand voltage value of the embankment height, multiple diodes are connected in series. When connecting in series, you should also pay attention to the voltage and current values of the single closed tube.

It depends! There are roughly 2 kinds of LED fluorescent lamps on the market now, one is a high-power 1W LED, and generally 20 in series (the current output of the drive circuit is large because of the large amount of current output by the drive circuit). The other is a combination of series and parallel, using straw hat LEDs.

Parallel and series connection of diodes.

What is the use of diodes in parallel and series?

Questions from anonymous users.

The resistance value is sufficient when the current flowing through the resistor is about three times the diode leakage current at the maximum cut-off voltage. But even under this condition, considerable losses can still occur in the resistor.

In principle, a dynamic voltage distribution is different from a static voltage distribution. If the carriers of one diode's p-n junction are smaller than the other, then it will be subjected to voltage earlier. Mountain branches.

Extended information: The main principle of the diode is to use the unidirectional conductivity of the p-n junction, and add leads and packages to the p-n junction to become a diode.

When there is a forward voltage bias in the external area, the mutual suppression effect of the external comic field and the self-built electric field increases the diffusion current of the carriers and causes the forward current.

When there is a reverse voltage bias in the outside world, the external electric field and the self-built electric field are further strengthened to form a reverse saturation current that is independent of the reverse bias voltage value within a certain reverse voltage range.

That is, when the coil is powered off, an induced electromotive force will be generated, and the two ends of the ** circle will produce reverse high voltage, so that an electric spark will be generated on the switch. If the coil is controlled by a triode, it will break down the triode, so the diode can protect the triode.

When the coil generates a reverse voltage, the diode turns on, forming a current, which discharges the magnetic field and eliminates the reverse voltage.

If HBJ is an ordinary relay, such as a power relay, or a voltage relay, then V1 and V2 are in opposite directions.

If the HBJ is a current relay, then V1 and V2 play the role of overcurrent protection to prevent the coil from heating and burning under the condition of high current. v3 is reverse protection.

If it is an ordinary relay, such as a power relay, or a voltage relay, then V1 and V2 are in opposite directions. The diode on the reverse parallel ** ring is called a freewheeling diode, which plays the role of suppressing the absorption of reverse electromotive force. If it is a current relay, then V1 and V2 play the role of overcurrent protection to prevent the coil from heating and burning under the condition of high current.

v3 is reverse protection.

There is a difference.

This is because the most common function of a diode is to allow current to pass through only one direction (called forward bias) and to block it in reverse direction (called reverse bias).

Turning the diode in reverse will cause the circuit to run out of current.

The resistance of the diode in series is for voltage division and current limiting, regardless of whether it is connected to the cathode or anode of the diode, as long as it is on, it can play the role of current limiting and voltage division, so it is the same.

The exception to this is the regulator diode. Because the Zener diode is reversed, the output voltage should be taken between the ground and the cathode, so the current limiting resistor should be connected to the cathode.

Whether it is an ordinary diode, a voltage regulator diode, etc., when the resistor and the diode are connected in series, they are connected in series to the positive or negative electrode, and the current in the diode and the resistor is the same. This is what junior high school physics has said: "In series circuits, the current is equal everywhere".

If you need to extract the voltage value to ground from the connection point, that's another problem.

It can play the following roles:

1. The unidirectional conductivity of the diode is used to prevent the power supply from being reversed, so as to protect the electronic circuit.

2. Isolation filtering of the signal of the front and back stages, this circuit is often connected with a capacitor to ground filtering at the negative end of the series diode.

3. Balance the DC potential of the front and rear stages, so that the pre-stage potential of the multi-stage amplifier is a little lower than that of the back stage.

It can play a variety of roles, such as one-way conduction, preventing power supply from being reversed, clamping limiting, step-down, and so on.

To make an accurate judgment, it depends on the form of the circuit.

Generally, in the DC circuit that is connected to the power supply, the diodes connected in series are mainly used for anti-reverse polarity protection. In this way, if you accidentally connect the positive and negative poles in reverse, the diode will not turn on, so as not to damage the device.

Reverse polarity protection means that the diode cuts off the circuit when the positive and negative poles are reversed.

A small voltage drop that takes advantage of the forward conduction voltage drop of the diode.