So what is a thyristor?

A thyristor is a high-power semiconductor device, also referred to as a silicon-controlled rectifier. Its structure includes four quantities of semiconductor elements, including 3 PN junctions corresponding for the Anode, Cathode, and control electrode Gate. These 3 poles would be 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 working status. Therefore, thyristors are popular in a variety of electronic circuits, like controllable rectification, AC voltage regulation, contactless electronic switches, inverters, and frequency alteration.

The graphical symbol of a semiconductor device is generally represented from the text symbol “V” or “VT” (in older standards, the letters “SCR”). Furthermore, derivatives of thyristors include fast thyristors, bidirectional thyristors, reverse conduction thyristors, and lightweight-controlled thyristors. The working condition of the thyristor is the fact when 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 between the anode and cathode (the anode is connected to the favorable pole of the power supply, and the cathode is attached to the negative pole of the power supply). But no forward voltage is used for the control pole (i.e., K is disconnected), and the indicator light will not glow. This shows that the thyristor is not really conducting and it has forward blocking capability.

2. Controllable conduction

As shown in Figure b above, when K is closed, and a forward voltage is used for the control electrode (known as a trigger, and the applied voltage is referred to as trigger voltage), the indicator light switches on. Which means that the transistor can control conduction.

3. Continuous conduction

As shown in Figure c above, following the thyristor is turned on, even if the voltage around the control electrode is taken away (which is, K is turned on again), the indicator light still glows. This shows that the thyristor can still conduct. At the moment, so that you can shut down the conductive thyristor, the power supply Ea has to be shut down or reversed.

4. Reverse blocking

As shown in Figure d above, although a forward voltage is used for the control electrode, a reverse voltage is used between the anode and cathode, and the indicator light will not glow at the moment. This shows that the thyristor is not really conducting and may reverse blocking.

5. In conclusion

1) Once the thyristor is exposed to a reverse anode voltage, the thyristor is in a reverse blocking state no matter what voltage the gate is exposed to.

2) Once the thyristor is exposed to a forward anode voltage, the thyristor will only conduct when the gate is exposed to a forward voltage. At the moment, the thyristor is within the forward conduction state, the thyristor characteristic, which is, the controllable characteristic.

3) Once the thyristor is turned on, so long as there exists a specific forward anode voltage, the thyristor will stay turned on regardless of the gate voltage. Which is, following the thyristor is turned on, the gate will lose its function. The gate only serves as a trigger.

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

5) The disorder for your thyristor to conduct is the fact a forward voltage ought to be applied between the anode and the cathode, and an appropriate forward voltage should also be applied between the gate and the cathode. To change off a conducting thyristor, the forward voltage between the anode and cathode has to be shut down, or the voltage has to be reversed.

Working principle of thyristor

A thyristor is essentially a distinctive triode composed of three PN junctions. It can be equivalently regarded as consisting of a PNP transistor (BG2) and an NPN transistor (BG1).

1. If a forward voltage is used between the anode and cathode of the thyristor without applying a forward voltage for the control electrode, although both BG1 and BG2 have forward voltage applied, the thyristor remains switched off because BG1 has no base current. If a forward voltage is used for the control electrode at the moment, BG1 is triggered to produce basics current Ig. BG1 amplifies this current, and a ß1Ig current is obtained in its collector. This current is precisely the base current of BG2. After amplification by BG2, a ß1ß2Ig current is going to be introduced the collector of BG2. This current is sent to BG1 for amplification then 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 large current appears within the emitters of these two transistors, which is, the anode and cathode of the thyristor (how big the current is in fact determined by how big the burden and how big Ea), and so the thyristor is entirely turned on. This conduction process is finished in a very short time.
2. Following the thyristor is turned on, its conductive state is going to be maintained from the positive feedback effect of the tube itself. Even if the forward voltage of the control electrode disappears, it really is still within the conductive state. Therefore, the function of the control electrode is simply to trigger the thyristor to change on. When the thyristor is turned on, the control electrode loses its function.
3. The best way to turn off the turned-on thyristor is to decrease the anode current so that it is inadequate to keep the positive feedback process. The best way to decrease the anode current is to shut down the forward power supply Ea or reverse the link of Ea. The minimum anode current required to maintain the thyristor within the conducting state is referred to as the holding current of the thyristor. Therefore, strictly speaking, so long as the anode current is lower than the holding current, the thyristor can be switched off.

Exactly what is the difference between a transistor and 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 task of a transistor relies upon electrical signals to control its opening and closing, allowing fast switching operations.

The thyristor needs a forward voltage and a trigger current at the gate to change on or off.

Application areas

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

Thyristors are mostly used in electronic circuits like 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 turned 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 based on stability and reliability and usually have higher turn-off voltage and larger on-current.

To summarize, although transistors and thyristors can be utilized in similar applications in some cases, due to their different structures and working principles, they have noticeable differences in performance and make use of occasions.

Application scope of thyristor

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

Supplier

PDDN Photoelectron Technology Co., Ltd is a wonderful thyristor supplier. It is actually one of the leading enterprises in the Home Accessory & Solar Power System, which is fully involved in the growth and development of power industry, intelligent operation and maintenance handling of 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.