What is a thyristor?

A thyristor is a high-power semiconductor device, also known as a silicon-controlled rectifier. Its structure contains 4 quantities of semiconductor elements, including three PN junctions corresponding to the Anode, Cathode, and control electrode Gate. These three poles are definitely the critical parts of the thyristor, allowing it to control current and perform high-frequency switching operations. Thyristors can operate under high voltage and high current conditions, and external signals can maintain their operating status. Therefore, thyristors are widely used in various electronic circuits, such as controllable rectification, AC voltage regulation, contactless electronic switches, inverters, and frequency conversion.

The graphical symbol of a semiconductor device is generally represented through the text symbol “V” or “VT” (in older standards, the letters “SCR”). In addition, derivatives of thyristors also include fast thyristors, bidirectional thyristors, reverse conduction thyristors, and light-controlled thyristors. The operating condition of the thyristor is that each time a forward voltage is used, the gate needs to have a trigger current.

Characteristics of thyristor

1. Forward blocking

As shown in Figure a above, when an ahead voltage is used involving the anode and cathode (the anode is connected to the favorable pole of the power supply, as well as the cathode is linked to the negative pole of the power supply). But no forward voltage is used to the control pole (i.e., K is disconnected), as well as the indicator light does not light up. This shows that the thyristor is not conducting and has forward blocking capability.

2. Controllable conduction

As shown in Figure b above, when K is closed, as well as a forward voltage is used to the control electrode (called a trigger, as well as the applied voltage is referred to as trigger voltage), the indicator light turns on. Because of this the transistor can control conduction.

3. Continuous conduction

As shown in Figure c above, after the thyristor is switched on, whether or not the voltage on the control electrode is taken away (that is certainly, K is switched on again), the indicator light still glows. This shows that the thyristor can still conduct. At the moment, so that you can stop the conductive thyristor, the power supply Ea should be stop or reversed.

4. Reverse blocking

As shown in Figure d above, although a forward voltage is used to the control electrode, a reverse voltage is used involving the anode and cathode, as well as the indicator light does not light up currently. This shows that the thyristor is not conducting and can reverse blocking.

5. In summary

1) Once the thyristor is put through a reverse anode voltage, the thyristor is in a reverse blocking state regardless of what voltage the gate is put through.

2) Once the thyristor is put through a forward anode voltage, the thyristor will simply conduct if the gate is put through a forward voltage. At the moment, the thyristor is in the forward conduction state, the thyristor characteristic, that is certainly, the controllable characteristic.

3) Once the thyristor is switched on, as long as there is a specific forward anode voltage, the thyristor will stay switched on whatever the gate voltage. Which is, after the thyristor is switched on, the gate will lose its function. The gate only serves as a trigger.

4) Once the thyristor is on, as well as the primary circuit voltage (or current) decreases to close to zero, the thyristor turns off.

5) The disorder for your thyristor to conduct is that a forward voltage ought to be applied involving the anode as well as the cathode, as well as an appropriate forward voltage ought to be applied involving the gate as well as the cathode. To change off a conducting thyristor, the forward voltage involving the anode and cathode should be stop, or even the voltage should be reversed.

Working principle of thyristor

A thyristor is actually an exclusive triode composed of three PN junctions. It could be equivalently viewed as consisting of a PNP transistor (BG2) as well as an NPN transistor (BG1).

1. When a forward voltage is used involving the anode and cathode of the thyristor without applying a forward voltage to the control electrode, although both BG1 and BG2 have forward voltage applied, the thyristor is still switched off because BG1 has no base current. When a forward voltage is used to the control electrode currently, BG1 is triggered to create basics current Ig. BG1 amplifies this current, as well as a ß1Ig current is obtained in its collector. This current is precisely the base current of BG2. After amplification by BG2, a ß1ß2Ig current will be brought in the collector of BG2. This current is sent to BG1 for amplification and after that sent to BG2 for amplification again. Such repeated amplification forms a vital positive feedback, causing both BG1 and BG2 to get in a saturated conduction state quickly. A sizable current appears inside the emitters of these two transistors, that is certainly, the anode and cathode of the thyristor (the size of the current is actually determined by the size of the stress and the size of Ea), so the thyristor is entirely switched on. This conduction process is finished in a very short time.
2. Following the thyristor is switched on, its conductive state will be maintained through the positive feedback effect of the tube itself. Whether or not the forward voltage of the control electrode disappears, it is still inside the conductive state. Therefore, the function of the control electrode is simply to trigger the thyristor to turn on. When the thyristor is switched on, the control electrode loses its function.
3. The only way to turn off the turned-on thyristor would be to reduce the anode current that it is insufficient to keep the positive feedback process. How you can reduce the anode current would be to stop the forward power supply Ea or reverse the bond of Ea. The minimum anode current needed to keep your thyristor inside the conducting state is referred to as the holding current of the thyristor. Therefore, as it happens, as long as the anode current is lower than the holding current, the thyristor could be switched off.

Exactly what is the difference between a transistor as well as a thyristor?

Structure

Transistors usually contain a PNP or NPN structure composed of three semiconductor materials.

The thyristor is made up of four PNPN structures of semiconductor materials, including anode, cathode, and control electrode.

Functioning conditions:

The work of a transistor relies on electrical signals to control its closing and opening, allowing fast switching operations.

The thyristor requires a forward voltage as well as a trigger current in the gate to turn on or off.

Application areas

Transistors are widely used in amplification, switches, oscillators, and other aspects of electronic circuits.

Thyristors are mostly found in electronic circuits such as controlled rectification, AC voltage regulation, contactless electronic switches, inverters, and frequency conversions.

Method of working

The transistor controls the collector current by holding the base current to accomplish current amplification.

The thyristor is switched on or off by managing the trigger voltage of the control electrode to understand the switching function.

Circuit parameters

The circuit parameters of thyristors are related to stability and reliability and in most cases have higher turn-off voltage and larger on-current.

To summarize, although transistors and thyristors may be used in similar applications sometimes, due to their different structures and operating principles, they may have noticeable differences in performance and make use of occasions.

Application scope of thyristor

• In power electronic equipment, thyristors may be used in frequency converters, motor controllers, welding machines, power supplies, etc.
• Within the lighting field, thyristors may be used in dimmers and light control devices.
• In induction cookers and electric water heaters, thyristors could be used to control the current flow to the heating element.
• In electric vehicles, transistors may be used in motor controllers.

Supplier

PDDN Photoelectron Technology Co., Ltd is a superb thyristor supplier. It really is one of the leading enterprises in the Home Accessory & Solar Power System, which is fully working in the growth and development of power industry, intelligent operation and maintenance control over power plants, solar power and related solar products manufacturing.

It accepts payment via Credit Card, T/T, West Union and Paypal. PDDN will ship the goods to customers overseas through FedEx, DHL, by air, or by sea. If you are searching for high-quality thyristor, please feel free to contact us and send an inquiry.