Specifically what is a thyristor?

A thyristor is a high-power semiconductor device, also called a silicon-controlled rectifier. Its structure includes 4 levels of semiconductor materials, including 3 PN junctions corresponding towards the Anode, Cathode, and control electrode Gate. These 3 poles would be the critical parts of 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 operating status. Therefore, thyristors are popular in different electronic circuits, including controllable rectification, AC voltage regulation, contactless electronic switches, inverters, and frequency conversion.

The graphical symbol of a semiconductor device is usually represented from 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 lightweight-controlled thyristors. The operating condition of the thyristor is that whenever a forward voltage is applied, 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 of the power supply, as well as the cathode is linked to the negative pole of 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 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, along with a forward voltage is applied towards the control electrode (referred to as a trigger, as well as the applied voltage is called trigger voltage), the indicator light turns on. This means that the transistor can control conduction.

3. Continuous conduction

As shown in Figure c above, after the thyristor is switched on, even when the voltage around the control electrode is removed (that is certainly, K is switched on again), the indicator light still glows. This demonstrates that the thyristor can continue to conduct. Currently, 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 applied towards the control electrode, a reverse voltage is applied between the anode and cathode, as well as the indicator light fails to 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 at a reverse blocking state no matter what voltage the gate is exposed to.

2) When the thyristor is exposed to a forward anode voltage, the thyristor will only conduct if the gate is exposed to a forward voltage. Currently, the thyristor is in the forward conduction state, which is the thyristor characteristic, that is certainly, the controllable characteristic.

3) When the thyristor is switched on, provided that there is a specific forward anode voltage, the thyristor will remain 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) When the thyristor is on, as well as the primary circuit voltage (or current) decreases to seal 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 perhaps the voltage should be reversed.

Working principle of thyristor

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

1. When a forward voltage is applied between the anode and cathode of 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 switched off because BG1 has no base current. When a forward voltage is applied towards the control electrode at the moment, BG1 is triggered to create basics current Ig. BG1 amplifies this current, along with 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 brought in the collector of BG2. This current is delivered to BG1 for amplification and then 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 sizable current appears within the emitters of the two transistors, that is certainly, the anode and cathode of the thyristor (the size of the current is actually determined by the size of the load and the size of Ea), therefore the thyristor is totally switched on. This conduction process is done in a very short time.
2. After the thyristor is switched on, its conductive state will likely be maintained from the positive feedback effect of the tube itself. Even when the forward voltage of the control electrode disappears, it is still within the conductive state. Therefore, the purpose of the control electrode is simply to trigger the thyristor to change on. Once the thyristor is switched on, the control electrode loses its function.
3. The only method to shut off the turned-on thyristor would be to lessen the anode current so that it is not enough to keep the positive feedback process. The way to lessen the anode current would be to shut down the forward power supply Ea or reverse the bond of Ea. The minimum anode current required to maintain the thyristor within the conducting state is called the holding current of the thyristor. Therefore, strictly speaking, provided that the anode current is less than the holding current, the thyristor may be switched off.

What exactly is the difference between a transistor along with a thyristor?

Structure

Transistors usually consist of a PNP or NPN structure composed of 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 requires a forward voltage along with a trigger current at the gate to change on or off.

Application areas

Transistors are popular in amplification, switches, oscillators, as well as other aspects of electronic circuits.

Thyristors are mostly 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 accomplish current amplification.

The thyristor is switched on or off by controlling the trigger voltage of the control electrode to realize the switching function.

Circuit parameters

The circuit parameters of thyristors are related to stability and reliability and in most cases 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 operating 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 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 superb thyristor supplier. It is one of the leading enterprises in the Home Accessory & Solar Power System, which is fully active in the progression of power industry, intelligent operation and maintenance handling of power plants, solar power 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.