What is a thyristor?

A thyristor is a high-power semiconductor device, also called a silicon-controlled rectifier. Its structure includes 4 quantities of semiconductor elements, including three PN junctions corresponding towards the Anode, Cathode, and control electrode Gate. These three poles are definitely 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, such as controllable rectification, AC voltage regulation, contactless electronic switches, inverters, and frequency alteration.

The graphical symbol of any silicon-controlled rectifier is generally represented by the text symbol “V” or “VT” (in older standards, the letters “SCR”). Furthermore, derivatives of thyristors also have fast thyristors, bidirectional thyristors, reverse conduction thyristors, and light-weight-controlled thyristors. The functioning condition in the thyristor is the fact 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 can be used involving the anode and cathode (the anode is attached to the favorable pole in the power supply, as well as the cathode is attached 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 implies that the thyristor will not be conducting and contains forward blocking capability.

2. Controllable conduction

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

3. Continuous conduction

As shown in Figure c above, following the thyristor is excited, whether or not the voltage around the control electrode is taken away (that is certainly, K is excited again), the indicator light still glows. This implies that the thyristor can carry on and conduct. At the moment, so that you can stop the conductive thyristor, the power supply Ea has to be stop 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 involving the anode and cathode, as well as the indicator light fails to glow at this time. This implies that the thyristor will not be conducting and will reverse blocking.

5. In conclusion

1) If 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) If the thyristor is put through a forward anode voltage, the thyristor will simply conduct when 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) If the thyristor is excited, as long as you will find a specific forward anode voltage, the thyristor will always be excited no matter the gate voltage. Which is, following the thyristor is excited, the gate will lose its function. The gate only functions as a trigger.

4) If 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 that thyristor to conduct is the fact a forward voltage should be applied involving the anode as well as the cathode, and an appropriate forward voltage should also be applied involving the gate as well as the cathode. To transform off a conducting thyristor, the forward voltage involving the anode and cathode has to be stop, or even the voltage has to be reversed.

Working principle of thyristor

A thyristor is basically a unique triode made up of three PN junctions. It can be equivalently regarded as comprising a PNP transistor (BG2) and an NPN transistor (BG1).

1. In case a forward voltage is applied involving 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 continues to be turned off because BG1 has no base current. In case a forward voltage is applied towards the control electrode at this time, BG1 is triggered to generate 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 brought to BG1 for amplification and after that brought to BG2 for amplification again. Such repeated amplification forms a crucial positive feedback, causing both BG1 and BG2 to enter a saturated conduction state quickly. A sizable current appears within the emitters of these two transistors, that is certainly, the anode and cathode in the thyristor (the dimensions of the current is actually determined by the dimensions of the stress and the dimensions of Ea), and so the thyristor is totally excited. This conduction process is completed in a really short time.
2. After the thyristor is excited, its conductive state is going to be maintained by the positive feedback effect in the tube itself. Whether or not the forward voltage in the control electrode disappears, it is still within the conductive state. Therefore, the function of the control electrode is only to trigger the thyristor to turn on. After the thyristor is excited, the control electrode loses its function.
3. The best way to shut off the turned-on thyristor would be to reduce the anode current so that it is insufficient to keep up the positive feedback process. The way to reduce the anode current would be to stop the forward power supply Ea or reverse the bond of Ea. The minimum anode current necessary to keep the thyristor within the conducting state is known as the holding current in the thyristor. Therefore, as it happens, as long as the anode current is under the holding current, the thyristor can be turned off.

What exactly is the distinction between a transistor and a thyristor?

Structure

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

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

Functioning conditions:

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

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

Application areas

Transistors are commonly used in amplification, switches, oscillators, along with other facets of electronic circuits.

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

Means of working

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

The thyristor is excited or off by managing the trigger voltage in the control electrode to comprehend 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 may be used in similar applications in some instances, because of the different structures and functioning principles, they may have noticeable differences in performance and utilize 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 light-weight control devices.
• In induction cookers and electric water heaters, thyristors may 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 is one in the leading enterprises in the Home Accessory & Solar Power System, that is fully working in the growth and development of power industry, intelligent operation and maintenance handling of power plants, solar power panel 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.