So what is a thyristor?

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

The graphical symbol of any silicon-controlled rectifier is usually represented through 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 of the thyristor is that when a forward voltage is used, 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 linked to the favorable pole of the power supply, and also the cathode is attached to the negative pole of the power supply). But no forward voltage is used for the control pole (i.e., K is disconnected), and also the indicator light does not glow. This shows that the thyristor is not really conducting and it 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 for the control electrode (referred to as a trigger, and also the applied voltage is known as trigger voltage), the indicator light turns on. Because of this 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 shows that the thyristor can still conduct. At this time, in order to cut off the conductive thyristor, the power supply Ea should be cut off or reversed.

4. Reverse blocking

As shown in Figure d above, although a forward voltage is used for the control electrode, a reverse voltage is used involving the anode and cathode, and also the indicator light does not glow at this time. This shows that the thyristor is not really conducting and will reverse blocking.

5. In conclusion

1) If the thyristor is exposed to a reverse anode voltage, the thyristor is within a reverse blocking state regardless of what voltage the gate is exposed to.

2) If the thyristor is exposed to a forward anode voltage, the thyristor will only conduct once the gate is exposed to a forward voltage. At this time, the thyristor is incorporated in the forward conduction state, the thyristor characteristic, that is certainly, the controllable characteristic.

3) If the thyristor is switched on, provided that there exists a specific forward anode voltage, the thyristor will always be switched on regardless of 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) If the thyristor is on, and also the primary circuit voltage (or current) decreases to close to zero, the thyristor turns off.

5) The condition for that thyristor to conduct is that a forward voltage needs to be applied involving the anode and also the cathode, as well as an appropriate forward voltage ought to be applied involving the gate and also the cathode. To change off a conducting thyristor, the forward voltage involving the anode and cathode should be cut off, or the voltage should be reversed.

Working principle of thyristor

A thyristor is basically a unique triode made up of three PN junctions. It can be equivalently viewed as consisting of a PNP transistor (BG2) as well as an NPN transistor (BG1).

1. When a forward voltage is used involving the anode and cathode of the thyristor without applying a forward voltage for the control electrode, although both BG1 and BG2 have forward voltage applied, the thyristor is still switched off because BG1 has no base current. When a forward voltage is used for the control electrode at this time, BG1 is triggered to create a base 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 and after that delivered to BG2 for amplification again. Such repeated amplification forms a vital positive feedback, causing both BG1 and BG2 to get into a saturated conduction state quickly. A sizable current appears in the emitters of these two transistors, that is certainly, the anode and cathode of the thyristor (how big the current is actually dependant on how big the load and how big Ea), and so the thyristor is totally switched on. This conduction process is done in an exceedingly limited time.
2. After the thyristor is switched on, its conductive state will likely be maintained through the positive feedback effect of the tube itself. Whether or not the forward voltage of the control electrode disappears, it is still in the conductive state. Therefore, the purpose of the control electrode is just to trigger the thyristor to turn on. Once the thyristor is switched on, the control electrode loses its function.
3. The best way to shut off the turned-on thyristor is to reduce the anode current so that it is not enough to keep up the positive feedback process. The best way to reduce the anode current is to cut off the forward power supply Ea or reverse the link of Ea. The minimum anode current needed to maintain the thyristor in the conducting state is known as the holding current of the thyristor. Therefore, as it happens, provided that the anode current is under the holding current, the thyristor may be switched off.

What exactly is the distinction between a transistor as well as a thyristor?

Structure

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

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

Operating conditions:

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

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

Application areas

Transistors are commonly used in amplification, switches, oscillators, and other facets of electronic circuits.

Thyristors are mainly found in electronic circuits like 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 managing 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 sum up, although transistors and thyristors can be utilized in similar applications sometimes, due to their different structures and functioning principles, they may have 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.
• Inside the lighting field, thyristors can be utilized in dimmers and light control devices.
• In induction cookers and electric water heaters, thyristors can be used to control the current flow for 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 is actually one of the leading enterprises in the Home Accessory & Solar Power System, which can be fully active in the growth and development of power industry, intelligent operation and maintenance control over power plants, solar power 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 searching for high-quality thyristor, please feel free to contact us and send an inquiry.