Specifically what is a thyristor?

A thyristor is actually a high-power semiconductor device, also referred to as a silicon-controlled rectifier. Its structure contains 4 levels of semiconductor components, including three PN junctions corresponding to the Anode, Cathode, and control electrode Gate. These three poles would be the critical parts from 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 popular in various electronic circuits, including controllable rectification, AC voltage regulation, contactless electronic switches, inverters, and frequency alteration.

The graphical symbol of a Thyristor is usually represented through 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 from the thyristor is that when a forward voltage is used, 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 utilized between the anode and cathode (the anode is connected to the favorable pole from the power supply, as well as the cathode is connected to the negative pole from 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 demonstrates that the thyristor is not conducting and contains 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 known as trigger voltage), the indicator light turns on. Which means that the transistor can control conduction.

3. Continuous conduction

As shown in Figure c above, right after the thyristor is excited, whether or not the voltage on the control electrode is removed (which is, K is excited again), the indicator light still glows. This demonstrates that the thyristor can continue to conduct. At the moment, to be able to 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 used to the control electrode, a reverse voltage is used between the anode and cathode, as well as the indicator light does not light up at the moment. This demonstrates that the thyristor is not conducting and will reverse blocking.

5. In summary

1) When the thyristor is exposed to a reverse anode voltage, the thyristor is in a reverse blocking state regardless of what voltage the gate is exposed to.

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

3) When the thyristor is excited, as long as there exists a specific forward anode voltage, the thyristor will stay excited no matter the gate voltage. That is certainly, right after the thyristor is excited, the gate will lose its function. The gate only works as a trigger.

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

5) The problem for that thyristor to conduct is that a forward voltage ought to be applied between the anode as well as the cathode, and an appropriate forward voltage also need to be applied between the gate as well as the cathode. To transform off a conducting thyristor, the forward voltage between the anode and cathode should be shut down, or the voltage should be reversed.

Working principle of thyristor

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

1. When a forward voltage is used between the anode and cathode from 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 at the moment, BG1 is triggered to generate 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 likely 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 an essential positive feedback, causing both BG1 and BG2 to enter a saturated conduction state quickly. A large current appears in the emitters of these two transistors, which is, the anode and cathode from the thyristor (the size of the current is in fact determined by the size of the burden and the size of Ea), therefore the thyristor is totally excited. This conduction process is completed in a really limited time.
2. Following the thyristor is excited, its conductive state will likely be maintained through the positive feedback effect from the tube itself. Whether or not the forward voltage from the control electrode disappears, it really is still in the conductive state. Therefore, the purpose of the control electrode is only to trigger the thyristor to turn on. When the thyristor is excited, the control electrode loses its function.
3. The only way to switch off the turned-on thyristor is to lessen the anode current that it is not enough to maintain the positive feedback process. How you can lessen the anode current is to shut down the forward power supply Ea or reverse the bond of Ea. The minimum anode current required to keep the thyristor in the conducting state is known as the holding current from the thyristor. Therefore, as it happens, as long as the anode current is under the holding current, the thyristor could be switched off.

Exactly what is the distinction between a transistor as well as 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.

Functioning 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 as well as a trigger current on the gate to turn on or off.

Application areas

Transistors are popular in amplification, switches, oscillators, along with other elements of electronic circuits.

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

Way of working

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

The thyristor is excited or off by manipulating the trigger voltage from the control electrode to comprehend 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 may be used in similar applications in some cases, because of the different structures and functioning principles, they have got 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.
• Within the lighting field, thyristors may be used in dimmers and lightweight control devices.
• In induction cookers and electric water heaters, thyristors may 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 is actually one from the leading enterprises in the Home Accessory & Solar Power System, which is fully involved in the development of power industry, intelligent operation and maintenance handling 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. If you are searching for high-quality thyristor, please feel free to contact us and send an inquiry.