So what is a thyristor?

A thyristor is actually a high-power semiconductor device, also called a silicon-controlled rectifier. Its structure consists of four quantities of semiconductor elements, including 3 PN junctions corresponding for the Anode, Cathode, and control electrode Gate. These 3 poles are the critical parts in the thyristor, letting it control current and perform high-frequency switching operations. Thyristors can operate under high voltage and high current conditions, and external signals can maintain their functioning status. Therefore, thyristors are commonly used in various electronic circuits, like controllable rectification, AC voltage regulation, contactless electronic switches, inverters, and frequency conversion.

The graphical symbol of a semiconductor device is usually represented by the text symbol “V” or “VT” (in older standards, the letters “SCR”). Additionally, derivatives of thyristors also include fast thyristors, bidirectional thyristors, reverse conduction thyristors, and lightweight-controlled thyristors. The functioning condition in the thyristor is the fact that each time a forward voltage is applied, the gate will need to have a trigger current.

Characteristics of thyristor

1. Forward blocking

As shown in Figure a above, when an ahead voltage is used in between the anode and cathode (the anode is connected to the favorable pole in the power supply, and also the cathode is linked to the negative pole in the power supply). But no forward voltage is applied for the control pole (i.e., K is disconnected), and also the indicator light will not illuminate. 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, along with a forward voltage is applied for the control electrode (known as a trigger, and also the applied voltage is referred to as trigger voltage), the indicator light switches on. This means that the transistor can control conduction.

3. Continuous conduction

As shown in Figure c above, following the thyristor is excited, even when the voltage around the control electrode is taken away (that is certainly, K is excited again), the indicator light still glows. This shows that the thyristor can still conduct. At the moment, to be able to stop the conductive thyristor, the power supply Ea must be stop or reversed.

4. Reverse blocking

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

5. In conclusion

1) Once the thyristor is subjected to a reverse anode voltage, the thyristor is within a reverse blocking state whatever voltage the gate is subjected to.

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

3) Once the thyristor is excited, as long as there exists a specific forward anode voltage, the thyristor will remain excited no matter the gate voltage. That is certainly, following the thyristor is excited, the gate will lose its function. The gate only serves as a trigger.

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

5) The condition for your thyristor to conduct is the fact that a forward voltage needs to be applied in between the anode and also the cathode, as well as an appropriate forward voltage should also be applied in between the gate and also the cathode. To transform off a conducting thyristor, the forward voltage in between the anode and cathode must be stop, or the voltage must be reversed.

Working principle of thyristor

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

1. If a forward voltage is applied in between the anode and cathode in the thyristor without applying a forward voltage for the control electrode, although both BG1 and BG2 have forward voltage applied, the thyristor is still switched off because BG1 has no base current. If a forward voltage is applied for the control electrode currently, BG1 is triggered to generate basics current Ig. BG1 amplifies this current, along with 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 brought in the collector of BG2. This current is delivered to BG1 for amplification then delivered to BG2 for amplification again. Such repeated amplification forms a crucial positive feedback, causing both BG1 and BG2 to get in a saturated conduction state quickly. A sizable current appears in the emitters of these two transistors, that is certainly, the anode and cathode in the thyristor (the dimensions of the current is actually dependant on the dimensions of the stress and the dimensions of Ea), so the thyristor is totally excited. This conduction process is completed in a really short period of time.
2. Following the thyristor is excited, its conductive state is going to be maintained by the positive feedback effect in the tube itself. Even if the forward voltage in the control electrode disappears, it is actually still in the conductive state. Therefore, the function of the control electrode is simply to trigger the thyristor to turn on. Once the thyristor is excited, the control electrode loses its function.
3. The only way to switch off the turned-on thyristor is always to decrease the anode current so that it is insufficient to maintain the positive feedback process. The way to decrease the anode current is always to stop the forward power supply Ea or reverse the connection of Ea. The minimum anode current needed to keep your thyristor in the conducting state is referred to as the holding current in the thyristor. Therefore, strictly speaking, as long as the anode current is under the holding current, the thyristor can be switched off.

What is the difference between a transistor along with a thyristor?

Structure

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

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

Working conditions:

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

The thyristor demands a forward voltage along with a trigger current at the gate to turn on or off.

Application areas

Transistors are commonly used in amplification, switches, oscillators, along with 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 attain current amplification.

The thyristor is excited or off by managing the trigger voltage in the control electrode to understand the switching function.

Circuit parameters

The circuit parameters of thyristors are based on stability and reliability and often have higher turn-off voltage and larger on-current.

To summarize, although transistors and thyristors can be utilized in similar applications in some cases, because of their different structures and functioning principles, they have noticeable variations in performance and utilize 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 may 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 really is one in 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 management of power plants, solar power and related solar products manufacturing.

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