So what is a thyristor?

A thyristor is actually a high-power semiconductor device, also known as a silicon-controlled rectifier. Its structure includes four quantities of semiconductor materials, including three PN junctions corresponding towards the Anode, Cathode, and control electrode Gate. These three poles would be the critical parts in 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 functioning status. Therefore, thyristors are commonly used in a variety of electronic circuits, including controllable rectification, AC voltage regulation, contactless electronic switches, inverters, and frequency alteration.

The graphical symbol of any silicon-controlled rectifier is normally represented from the text symbol “V” or “VT” (in older standards, the letters “SCR”). Furthermore, 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 when a forward voltage is applied, the gate should have a trigger current.

Characteristics of thyristor

1. Forward blocking

As shown in Figure a above, when an ahead voltage is utilized in between the anode and cathode (the anode is linked to the favorable pole in the power supply, as well as the cathode is linked to the negative pole in the power supply). But no forward voltage is applied towards the control pole (i.e., K is disconnected), as well as the indicator light fails to glow. This demonstrates that the thyristor is not really conducting and has forward blocking capability.

2. Controllable conduction

As shown in Figure b above, when K is closed, along with a forward voltage is applied towards the control electrode (known as a trigger, as well as the applied voltage is called trigger voltage), the indicator light turns on. Which means that the transistor can control conduction.

3. Continuous conduction

As shown in Figure c above, after the thyristor is switched on, even if the voltage around the control electrode is removed (which is, K is switched on again), the indicator light still glows. This demonstrates that the thyristor can continue to conduct. At this time, so that you can shut down the conductive thyristor, the power supply Ea should be shut down or reversed.

4. Reverse blocking

As shown in Figure d above, although a forward voltage is applied towards the control electrode, a reverse voltage is applied in between the anode and cathode, as well as the indicator light fails to glow currently. This demonstrates that the thyristor is not really conducting and may reverse blocking.

5. In conclusion

1) Once the thyristor is put through a reverse anode voltage, the thyristor is at 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 is only going to conduct when the gate is put through a forward voltage. At this time, the thyristor is in the forward conduction state, which is the thyristor characteristic, which is, the controllable characteristic.

3) Once the thyristor is switched on, as long as there exists 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 functions 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 condition for the thyristor to conduct is the fact that a forward voltage needs to be applied in between the anode as well as the cathode, and an appropriate forward voltage should also be applied in between the gate as well as the cathode. To transform off a conducting thyristor, the forward voltage in between the anode and cathode should be shut down, or even the voltage should be reversed.

Working principle of thyristor

A thyristor is actually a distinctive triode composed of three PN junctions. It can be equivalently viewed as comprising a PNP transistor (BG2) and 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 towards 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 applied towards the control electrode currently, BG1 is triggered to produce basics current Ig. BG1 amplifies this current, along with a ß1Ig current is obtained in their collector. This current is precisely the base current of BG2. After amplification by BG2, a ß1ß2Ig current will likely be brought in the collector of BG2. This current is sent to BG1 for amplification and then sent to BG2 for amplification again. Such repeated amplification forms an essential positive feedback, causing both BG1 and BG2 to get into a saturated conduction state quickly. A big current appears inside the emitters of these two transistors, which is, the anode and cathode in the thyristor (how big the current is actually determined by how big the burden and how big Ea), therefore the thyristor is entirely switched on. This conduction process is completed in a really short time.
2. Following the thyristor is switched on, its conductive state will likely be maintained from the positive feedback effect in the tube itself. Even when the forward voltage in the control electrode disappears, it is still inside the conductive state. Therefore, the purpose of the control electrode is only to trigger the thyristor to turn on. When the thyristor is switched on, the control electrode loses its function.
3. The only way to switch off the turned-on thyristor would be to reduce the anode current that it is not enough to maintain the positive feedback process. How you can reduce the anode current would be to shut down the forward power supply Ea or reverse the link of Ea. The minimum anode current needed to keep your thyristor inside the conducting state is called the holding current in the thyristor. Therefore, as it happens, as long as the anode current is lower than the holding current, the thyristor may be switched off.

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

Structure

Transistors usually consist of 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 any transistor relies on electrical signals to control its opening and closing, 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 mainly utilized in electronic circuits including 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 switched on 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 in most cases have higher turn-off voltage and larger on-current.

To sum up, although transistors and thyristors may be used in similar applications sometimes, because of their different structures and functioning principles, they have got noticeable variations 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.
• Inside the lighting field, thyristors may be used in dimmers and lightweight control devices.
• In induction cookers and electric water heaters, thyristors could be used to control the current flow towards the heating element.
• In electric vehicles, transistors may be used 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 can be fully working in the progression of power industry, intelligent operation and maintenance management of power plants, solar panel 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. If you are searching for high-quality thyristor, please feel free to contact us and send an inquiry.