So what is a thyristor?

A thyristor is really a high-power semiconductor device, also known as 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 the critical parts in 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 commonly used in a variety of electronic circuits, including controllable rectification, AC voltage regulation, contactless electronic switches, inverters, and frequency conversion.

The graphical symbol of any semiconductor device is normally 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 light-weight-controlled thyristors. The operating condition in the thyristor is the fact each time 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 attached to the favorable pole in the power supply, and also the cathode is linked to the negative pole in the power supply). But no forward voltage is used towards the control pole (i.e., K is disconnected), and also the indicator light does not light up. This demonstrates that the thyristor is not really conducting and has forward blocking capability.

2. Controllable conduction

As shown in Figure b above, when K is closed, as well as a forward voltage is used towards the control electrode (called a trigger, and also the applied voltage is called trigger voltage), the indicator light switches on. Which means that the transistor can control conduction.

3. Continuous conduction

As shown in Figure c above, right after the thyristor is turned on, whether or not the voltage around the control electrode is removed (that is certainly, K is turned on again), the indicator light still glows. This demonstrates that the thyristor can carry on and conduct. Currently, in order 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 used towards the control electrode, a reverse voltage is used in between the anode and cathode, and also the indicator light does not light up at the moment. This demonstrates that the thyristor is not really conducting and can reverse blocking.

5. To sum up

1) If the thyristor is subjected to a reverse anode voltage, the thyristor is at a reverse blocking state no matter what voltage the gate is subjected to.

2) If the thyristor is subjected to a forward anode voltage, the thyristor will only conduct once the gate is subjected to a forward voltage. Currently, the thyristor is incorporated in the forward conduction state, which is the thyristor characteristic, that is certainly, the controllable characteristic.

3) If the thyristor is turned on, provided that you will find a specific forward anode voltage, the thyristor will remain turned on whatever the gate voltage. That is, right after the thyristor is turned on, 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 close to zero, the thyristor turns off.

5) The problem for your thyristor to conduct is the fact a forward voltage should be applied in between the anode and also the cathode, plus an appropriate forward voltage also need to 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 must be stop, or the voltage must be reversed.

Working principle of thyristor

A thyristor is essentially a distinctive triode made from three PN junctions. It could be equivalently thought to be consisting of a PNP transistor (BG2) plus an NPN transistor (BG1).

1. When a forward voltage is used in between the anode and cathode in the thyristor without applying a forward voltage towards the control electrode, although both BG1 and BG2 have forward voltage applied, the thyristor is still turned off because BG1 has no base current. When a forward voltage is used towards the control electrode at the moment, BG1 is triggered to create 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 delivered to BG1 for amplification 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 inside the emitters of these two transistors, that is certainly, the anode and cathode in the thyristor (the dimensions of the current is actually based on the dimensions of the burden and the dimensions of Ea), therefore the thyristor is completely turned on. This conduction process is finished in a very short period of time.
2. Right after the thyristor is turned on, its conductive state will likely be maintained from the positive feedback effect in the tube itself. Even if the forward voltage in the control electrode disappears, it really is still inside the conductive state. Therefore, the function of the control electrode is just to trigger the thyristor to turn on. Once the thyristor is turned on, the control electrode loses its function.
3. The only way to switch off the turned-on thyristor is to decrease the anode current that it is insufficient to keep up the positive feedback process. The best way to decrease the anode current is to stop the forward power supply Ea or reverse the bond of Ea. The minimum anode current needed to keep your thyristor inside the conducting state is called the holding current in the thyristor. Therefore, as it happens, provided that the anode current is less than the holding current, the thyristor may be turned 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.

Functioning conditions:

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

The thyristor requires a forward voltage as well as a trigger current on the gate to turn on or off.

Application areas

Transistors are commonly used in amplification, switches, oscillators, along with 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.

Way 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 usually have higher turn-off voltage and larger on-current.

To summarize, although transistors and thyristors can be utilized in similar applications in some instances, due to their different structures and operating principles, they have got noticeable variations in performance and make use of occasions.

Application scope of thyristor

• In power electronic equipment, thyristors can be utilized in frequency converters, motor controllers, welding machines, power supplies, etc.
• In the lighting field, thyristors can be utilized in dimmers and light-weight control devices.
• In induction cookers and electric water heaters, thyristors may 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 an excellent thyristor supplier. It is actually one in the leading enterprises in the Home Accessory & Solar Power System, which is fully active in the growth and development of power industry, intelligent operation and maintenance management of power plants, solar power 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.