Specifically what is a thyristor?

A thyristor is actually a high-power semiconductor device, also known as a silicon-controlled rectifier. Its structure consists of 4 levels of semiconductor materials, including 3 PN junctions corresponding to the Anode, Cathode, and control electrode Gate. These 3 poles would be the critical parts from 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, like controllable rectification, AC voltage regulation, contactless electronic switches, inverters, and frequency conversion.

The graphical symbol of a silicon-controlled rectifier is normally represented through 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-controlled thyristors. The functioning condition from the thyristor is the fact that whenever 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 in between the anode and cathode (the anode is linked to the favorable pole from the power supply, and also the cathode is linked to the negative pole from the power supply). But no forward voltage is used to the control pole (i.e., K is disconnected), and also the indicator light will not glow. This implies that the thyristor is not really 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 (known as a trigger, and also the applied voltage is called trigger voltage), the indicator light turns on. Because of this 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 removed (that is, K is excited again), the indicator light still glows. This implies that the thyristor can continue to 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 to the control electrode, a reverse voltage is used in between the anode and cathode, and also the indicator light will not glow at this time. This implies that the thyristor is not really conducting and will reverse blocking.

5. In conclusion

1) If the thyristor is exposed to a reverse anode voltage, the thyristor is in a reverse blocking state whatever voltage the gate is exposed to.

2) If the thyristor is exposed to a forward anode voltage, the thyristor is only going to conduct when the gate is exposed to a forward voltage. At the moment, the thyristor is in the forward conduction state, the thyristor characteristic, that is, the controllable characteristic.

3) If the thyristor is excited, as long as there is a specific forward anode voltage, the thyristor will always be excited no matter the gate voltage. That is certainly, following the thyristor is excited, the gate will lose its function. The gate only functions as a trigger.

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

5) The problem for the thyristor to conduct is the fact that a forward voltage ought 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 turn off a conducting thyristor, the forward voltage in between the anode and cathode has to be shut down, or perhaps the voltage has to be reversed.

Working principle of thyristor

A thyristor is actually a distinctive triode made from three PN junctions. It may be equivalently thought to be comprising a PNP transistor (BG2) as well as an NPN transistor (BG1).

1. When a forward voltage is used in 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 this time, BG1 is triggered to generate a base current Ig. BG1 amplifies this current, as well as 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 be brought in the collector of BG2. This current is delivered to BG1 for amplification and after that delivered 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 inside the emitters of these two transistors, that is, the anode and cathode from the thyristor (the dimensions of the current is really determined by the dimensions of the burden and the dimensions of Ea), so the thyristor is completely excited. This conduction process is finished in a very limited time.
2. Following the thyristor is excited, its conductive state will be maintained through the positive feedback effect from the tube itself. Even when the forward voltage from the control electrode disappears, it is actually still inside the conductive state. Therefore, the purpose of the control electrode is just to trigger the thyristor to transform on. After the thyristor is excited, the control electrode loses its function.
3. The only method to shut off the turned-on thyristor would be to decrease the anode current so that it is inadequate to keep up the positive feedback process. The best way to decrease the anode current would be to shut down the forward power supply Ea or reverse the connection of Ea. The minimum anode current needed to maintain the thyristor inside the conducting state is called 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 made from three semiconductor materials.

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

Working conditions:

The task of a transistor relies upon electrical signals to control its closing and opening, allowing fast switching operations.

The thyristor needs a forward voltage as well as a trigger current at the gate to transform 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 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 excited or off by managing the trigger voltage from the control electrode to realize 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 used in similar applications in some cases, because of their different structures and functioning principles, they have noticeable differences in performance and utilize occasions.

Application scope of thyristor

• In power electronic equipment, thyristors can be used in frequency converters, motor controllers, welding machines, power supplies, etc.
• Inside the lighting field, thyristors can be used in dimmers and light 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 can be used in motor controllers.

Supplier

PDDN Photoelectron Technology Co., Ltd is an excellent thyristor supplier. It is actually one from the leading enterprises in the Home Accessory & Solar Power System, which is fully working in the development of power industry, intelligent operation and maintenance handling of power plants, solar panel and related solar products manufacturing.

It accepts payment via Bank 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 looking for high-quality thyristor, please feel free to contact us and send an inquiry.