Specifically what is a thyristor?

A thyristor is really a high-power semiconductor device, also called a silicon-controlled rectifier. Its structure includes four quantities of semiconductor components, including 3 PN junctions corresponding to the Anode, Cathode, and control electrode Gate. These 3 poles are 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 widely used in a variety of electronic circuits, such as controllable rectification, AC voltage regulation, contactless electronic switches, inverters, and frequency alteration.

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

Characteristics of thyristor

1. Forward blocking

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

3. Continuous conduction

As shown in Figure c above, following the thyristor is turned on, whether or not the voltage in the control electrode is taken away (which is, K is turned on again), the indicator light still glows. This implies that the thyristor can carry on and conduct. Currently, 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 to the control electrode, a reverse voltage is applied involving the anode and cathode, as well as the indicator light will not light up currently. This implies that the thyristor is not really conducting and can reverse blocking.

5. In conclusion

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

2) Once 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. Currently, the thyristor is within the forward conduction state, which is the thyristor characteristic, which is, the controllable characteristic.

3) Once the thyristor is turned on, so long as there exists a specific forward anode voltage, the thyristor will remain turned on no matter the gate voltage. Which is, following the thyristor is turned 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 seal to zero, the thyristor turns off.

5) The condition for that thyristor to conduct is the fact that a forward voltage should be applied involving the anode as well as the cathode, as well as an appropriate forward voltage ought to be applied involving the gate as well as the cathode. To turn off a conducting thyristor, the forward voltage involving the anode and cathode must be stop, or perhaps the voltage must be reversed.

Working principle of thyristor

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

1. When a forward voltage is applied involving the anode and cathode in the thyristor without applying a forward voltage to the control electrode, although both BG1 and BG2 have forward voltage applied, the thyristor remains switched off because BG1 has no base current. When a forward voltage is applied to the control electrode currently, BG1 is triggered to produce a base current Ig. BG1 amplifies this current, and a ß1Ig current is obtained in the 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 delivered to BG1 for amplification and after that delivered to BG2 for amplification again. Such repeated amplification forms a vital positive feedback, causing both BG1 and BG2 to get in a saturated conduction state quickly. A big current appears in the emitters of these two transistors, which is, the anode and cathode in the thyristor (the dimensions of the current is in fact determined by the dimensions of the stress and the dimensions of Ea), so the thyristor is entirely turned on. This conduction process is completed in an exceedingly short period of time.
2. Following the thyristor is turned on, its conductive state will likely be maintained by the positive feedback effect in the tube itself. Even when the forward voltage in the control electrode disappears, it is actually still in the conductive state. Therefore, the function of the control electrode is just to trigger the thyristor to transform on. After the thyristor is turned on, the control electrode loses its function.
3. The only way to shut off the turned-on thyristor is always to reduce the anode current that it is inadequate to maintain the positive feedback process. The best way to reduce the anode current is always to stop the forward power supply Ea or reverse the bond of Ea. The minimum anode current necessary to keep the thyristor in the conducting state is referred to as the holding current in the thyristor. Therefore, strictly speaking, so long as the anode current is under the holding current, the thyristor can be switched off.

Exactly what is the distinction between a transistor and a thyristor?

Structure

Transistors usually consist of a PNP or NPN structure made up 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 relies upon electrical signals to control its closing and opening, allowing fast switching operations.

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

Application areas

Transistors are widely used in amplification, switches, oscillators, along with other aspects 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 attain current amplification.

The thyristor is turned on or off by manipulating the trigger voltage in the control electrode to realize 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 summarize, although transistors and thyristors can be used in similar applications sometimes, due to their different structures and functioning principles, they have got noticeable differences in performance and make use of 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 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 handling of power plants, solar 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. Should you be looking for high-quality thyristor, please feel free to contact us and send an inquiry.