Bidirectional thyristor, what is a unidirectional thyristor and how to use it?

The international common name of thyristor (SCR) is thyyistor, and the Chinese abbreviation thyristor. It can work under high voltage and high current conditions, and has the characteristics of high withstand voltage, large capacity and small size.

1. Characteristics of thyristors.

Thyristors are divided into unidirectional thyristors and bidirectional thyristors. The unidirectional thyristor has three pins: anode A, cathode mid, and control electrode G. The triac has three pins: the first anode A1 (T1), the second anode A2 (T2), and the control electrode G.

Unidirectional, that is, the current passing through the two main poles of the thyristor can only flow in one direction. Therefore, when the current is reversed, the thyristor will not pass, and it will be bidirectional, that is, the current through the two main poles of the thyristor can flow in both directions. Therefore, when the current is reversed, the thyristor can still be turned on, can it be replaced by a two-way one direction where it can be used?

It depends on the circuit, some occasions are okay, some occasions are not!

In the case of the voltage applied to the yang 1 and yang 2 poles of the bidirectional thyristor, enough positive or negative trigger voltage is added to the trigger terminal, and the bidirectional thyristor is turned on. If the two poles of the bidirectional thyristor 1 and 2 lose voltage, the bidirectional thyristor will be automatically disconnected, and then add voltage to the yang 1 and yang 2 poles of the bidirectional thyristor, if there is no trigger voltage at this time, the bidirectional thyristor will still be in a disconnected state.

Reducing the forward anode voltage to a single point or adding the reverse anode voltage can make the thyristor change from on-to off.

In order for a thyristor to change from turn-on to off, the passing current must be reduced below the maintenance current. The main way to reduce the noise current of electric silver is to reduce the current by reducing the loop voltage, and the second is to increase the loop resistance to reduce the current.

According to its packaging form, the thyristor can be divided into three types: metal encapsulated thyristor, plastic encapsulated thyristor and ceramic encapsulated thyristor. Among them, metal-encapsulated thyristors are divided into bolt-shaped, flat-shaped, round-shell and other types; Plastic thyristors are divided into two types: type with heat sink and type without heat sink.

According to the current capacity, thyristors can be divided into three types: high-power thyristors, medium-power thyristors and low-power thyristors. In general, high-power thyristors are mostly packaged in metal shells, while medium- and low-power thyristors are mostly packaged in plastic or ceramic packages.

Categories: Science & Engineering >> Engineering & Technology Sciences.

Problem description: The book says that there are many kinds of trigger methods, but I feel that it is inconvenient to judge in engineering applications, my understanding is that as long as the G pole has a trigger signal, because it is a bidirectional thyristor, the trigger signal can be positive or negative, and when the trigger signal strength requirements are met, the bidirectional thyristor is turned on. Is that right? In the same way, I understand that the same is true of ordinary unidirectional thyristors.

Don't know, right?

Analysis: 1The landlord's point of view is correct about bidirectional thyristors. The one-way thyristor liquid slow can only be triggered in the positive trigger mode.

2.In general, a negative trigger method is preferable for bidirectional thyristors. That is, regardless of the positive or negative of the first and second anodes of the chain mode, the trigger current should be injected from the second anode to control the outflow of the electrode.

The unidirectional thyristor has the advantages of small size, relatively simple structure, strong function, light weight, high efficiency and flexible control.

A unidirectional thyristor (SCR) has three PN junctions inside, which are the main bright burning junction, the auxiliary junction, and the trigger junction.

The main junction is the core component of the SCR and consists of one p-type semiconductor and two n-type semiconductors. Its positive end is connected to the anode and the negative end is connected to the cathode. When a sufficiently large anode voltage is applied, a reverse bias region is formed in the main junction, which can be broken down under certain conditions to produce a flow effect.

Auxiliary junctions are also known as protection diodes or free-wheel diodes. It is connected in parallel with the main junction to form the entire SCR component. During operation, when the load is disconnected or the AC power waveform reverses the peak, the auxiliary junction acts as a protection and releases the remaining energy.

The trigger junction is located at the control port of the SCR. It consists of a p-type semiconductor and an n-type semiconductor, and is led out by metal wiring for control signal input. When an appropriate trigger pulse signal is applied, the previously blocked current in the main SCR junction can be allowed to pass through and maintain a stable state.

As a result, there are a total of three PN junctions inside the unidirectional thyristor for its special functions and performance.

A unidirectional thyristor can be used as a type of semiconductor switch. It can remain open when current is passed through and turn on when power is stopped. Therefore, it can be used to control the current in electronic devices and thus realize the switching function.

In addition, unidirectional thyristors can also be used to protect circuits from overcurrent or overvoltage. For example, it can be used in power lines to disconnect circuits when they are subjected to overcurrent or overvoltage, thus protecting the circuit from damage.

In conclusion, unidirectional thyristors can be used as switches in electronic devices or as a protection circuit from damage caused by overcurrent or overvoltage.

Unidirectional thyristors are mainly used in power lines to protect circuits from damage caused by overcurrent or overvoltage. It can also be used for switches in electronic devices, such as power switches for computers, power switches for televisions, etc.

In addition, unidirectional thyristors can also be used in the field of communication, e.g. for the protection of ** lines. In the medical field, it can also be used in pacemakers to control the switching of cardiac pacing currents. In conclusion, unidirectional thyristors are widely used in many fields.

If a one-way thyristor fails, it can lead to circuit failure, and may even cause circuit overload or circuit short-circuit. If a one-way thyristor is found to be faulty, it should be stopped immediately and a professional should be contacted for maintenance.

Often, the cause of one-way thyristor failure can be due to overload or overvoltage. Therefore, when using unidirectional thyristors, care should be taken to prevent overload or overvoltage to ensure the normal operation of unidirectional thyristors.

A bidirectional thyristor is a triac, which uses the forward and reverse conduction angles (alternating current) to adjust the output voltage or speed regulation.

Hello:——Bidirectional thyristors are bidirectional thyristors. The function of the bidirectional thyristor is to use the forward and reverse conduction angles (alternating current) to adjust the output voltage or speed regulation.