So what is a thyristor?

A thyristor is a high-power semiconductor device, also called a silicon-controlled rectifier. Its structure consists of four quantities of semiconductor elements, including 3 PN junctions corresponding towards the Anode, Cathode, and control electrode Gate. These 3 poles are definitely 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 functioning status. Therefore, thyristors are commonly used in different electronic circuits, such as controllable rectification, AC voltage regulation, contactless electronic switches, inverters, and frequency conversion.

The graphical symbol of any semiconductor device is generally represented from the text symbol “V” or “VT” (in older standards, the letters “SCR”). Furthermore, derivatives of thyristors include fast thyristors, bidirectional thyristors, reverse conduction thyristors, and lightweight-controlled thyristors. The functioning condition of 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 utilized involving the anode and cathode (the anode is attached 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 will not light up. This shows that the thyristor is not conducting and it has 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 (known as a trigger, as well as the applied voltage is called trigger voltage), the indicator light turns on. Which 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 taken away (that is certainly, K is switched on again), the indicator light still glows. This shows that the thyristor can still conduct. At this time, to be able to cut off the conductive thyristor, the power supply Ea has to be cut off 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 will not light up at the moment. This shows that the thyristor is not conducting and will reverse blocking.

5. In conclusion

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

2) When the thyristor is subjected to a forward anode voltage, the thyristor will simply conduct once the gate is subjected to a forward voltage. At this time, the thyristor is within the forward conduction state, the thyristor characteristic, that is certainly, the controllable characteristic.

3) When the thyristor is switched on, so long as you will find a specific forward anode voltage, the thyristor will always be switched on no matter the gate voltage. Which is, after the thyristor is switched on, the gate will lose its function. The gate only serves 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 disorder 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 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 cut off, or perhaps the voltage has to be reversed.

Working principle of thyristor

A thyristor is essentially a unique triode composed of three PN junctions. It may be equivalently viewed 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 of the thyristor without applying a forward voltage towards the control electrode, although both BG1 and BG2 have forward voltage applied, the thyristor remains turned off because BG1 has no base current. When a forward voltage is applied towards the control electrode at the moment, BG1 is triggered to produce basics 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 is going to be brought in the collector of BG2. This current is sent to BG1 for amplification and then sent to BG2 for amplification again. Such repeated amplification forms an essential positive feedback, causing both BG1 and BG2 to get into a saturated conduction state quickly. A large current appears in the emitters of these two transistors, that is certainly, the anode and cathode of the thyristor (the size of the current is really dependant on the size of the stress and the size of Ea), therefore the thyristor is totally switched on. This conduction process is done in a really limited time.
2. After the thyristor is switched on, its conductive state is going to be maintained from the positive feedback effect of the tube itself. Whether or not the forward voltage of the control electrode disappears, it really is still in the conductive state. Therefore, the function of the control electrode is simply to trigger the thyristor to turn on. Once the thyristor is switched on, the control electrode loses its function.
3. The best way to switch off the turned-on thyristor is always to reduce the anode current so that it is insufficient to keep up the positive feedback process. The best way to reduce the anode current is always to cut off 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 called the holding current of the thyristor. Therefore, as it happens, so long as the anode current is less than the holding current, the thyristor can be turned off.

Exactly what is the distinction between a transistor and 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.

Functioning conditions:

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

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

Application areas

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

Thyristors are mainly found in electronic circuits such as 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 attain current amplification.

The thyristor is switched on or off by manipulating the trigger voltage of 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 can be utilized in similar applications in some cases, because of the different structures and functioning principles, they may have noticeable variations in performance and utilize occasions.

Application scope of thyristor

• In power electronic equipment, thyristors can be utilized in frequency converters, motor controllers, welding machines, power supplies, etc.
• Within the lighting field, thyristors can be utilized 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 can be utilized in motor controllers.

Supplier

PDDN Photoelectron Technology Co., Ltd is a superb thyristor supplier. It really is one of the leading enterprises in the Home Accessory & Solar Power System, that is fully involved in the progression of power industry, intelligent operation and maintenance control over power plants, solar panel 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.