So what is a thyristor?

A thyristor is really a high-power semiconductor device, also called a silicon-controlled rectifier. Its structure consists of 4 levels of semiconductor materials, 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 popular 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 generally represented through 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 operating condition in 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 between the anode and cathode (the anode is linked to the favorable pole in the power supply, and 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 the indicator light does not illuminate. This shows that the thyristor will not be conducting and has forward blocking capability.

2. Controllable conduction

As shown in Figure b above, when K is closed, along with a forward voltage is used towards the control electrode (referred to as a trigger, and 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, following the thyristor is excited, even when the voltage on the control electrode is taken away (that is, K is excited again), the indicator light still glows. This shows that the thyristor can carry on and conduct. At this time, so that you can stop the conductive thyristor, the power supply Ea should 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 between the anode and cathode, and the indicator light does not illuminate at this time. This shows that the thyristor will not be conducting and may reverse blocking.

5. In summary

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

2) If the thyristor is put through a forward anode voltage, the thyristor will only conduct if the gate is put through a forward voltage. At this time, the thyristor is within the forward conduction state, the thyristor characteristic, that is, the controllable characteristic.

3) If the thyristor is excited, so long as there exists a specific forward anode voltage, the thyristor will always be excited whatever the gate voltage. Which is, following the thyristor is excited, the gate will lose its function. The gate only works as a trigger.

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

5) The condition for your thyristor to conduct is the fact that a forward voltage ought to be applied between the anode and the cathode, and an appropriate forward voltage ought to be applied between the gate and the cathode. To transform off a conducting thyristor, the forward voltage between the anode and cathode should be stop, or the voltage should be reversed.

Working principle of thyristor

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

1. In case a forward voltage is used 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 remains switched off because BG1 has no base current. In case a forward voltage is used towards the control electrode at this time, BG1 is triggered to generate a base current Ig. BG1 amplifies this current, along with 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 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 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 these two transistors, that is, the anode and cathode in the thyristor (the dimensions of the current is really based on the dimensions of the burden and the dimensions of Ea), and so the thyristor is totally excited. This conduction process is finished in a really short time.
2. After the thyristor is excited, its conductive state will be maintained through the positive feedback effect in the tube itself. Whether or not the forward voltage in the control electrode disappears, it is actually still within the conductive state. Therefore, the function of the control electrode is simply to trigger the thyristor to turn on. After the thyristor is excited, the control electrode loses its function.
3. The best way to shut off the turned-on thyristor would be to reduce the anode current so that it is inadequate to keep up the positive feedback process. The best way to reduce the anode current would be to stop the forward power supply Ea or reverse the link of Ea. The minimum anode current needed to keep the thyristor within the conducting state is called the holding current in the thyristor. Therefore, as it happens, so long as the anode current is under the holding current, the thyristor may be switched off.

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

Structure

Transistors usually contain a PNP or NPN structure made from three semiconductor materials.

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

Functioning conditions:

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

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

Application areas

Transistors are popular in amplification, switches, oscillators, and 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.

Way of working

The transistor controls the collector current by holding the base current to accomplish current amplification.

The thyristor is excited or off by controlling 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 may be used in similar applications in some cases, because of the different structures and operating principles, they may have noticeable variations 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.
• Inside the lighting field, thyristors may be used in dimmers and lightweight control devices.
• In induction cookers and electric water heaters, thyristors can 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 an excellent thyristor supplier. It is actually one in the leading enterprises in the Home Accessory & Solar Power System, which is fully involved in the development of power industry, intelligent operation and maintenance management 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. If you are searching for high-quality thyristor, please feel free to contact us and send an inquiry.