Specifically what is a thyristor?

A thyristor is actually a high-power semiconductor device, also known as a silicon-controlled rectifier. Its structure includes 4 levels of semiconductor components, including three PN junctions corresponding towards the Anode, Cathode, and control electrode Gate. These three 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 functioning status. Therefore, thyristors are popular in different electronic circuits, such as controllable rectification, AC voltage regulation, contactless electronic switches, inverters, and frequency alteration.

The graphical symbol of the silicon-controlled rectifier is normally represented through the text symbol “V” or “VT” (in older standards, the letters “SCR”). In addition, derivatives of thyristors include fast thyristors, bidirectional thyristors, reverse conduction thyristors, and light-weight-controlled thyristors. The functioning condition in the thyristor is the fact that when a forward voltage is applied, the gate should have a trigger current.

Characteristics of thyristor

1. Forward blocking

As shown in Figure a above, when an ahead voltage can be used involving the anode and cathode (the anode is linked to the favorable pole in the power supply, and the cathode is connected to the negative pole in the power supply). But no forward voltage is applied towards the control pole (i.e., K is disconnected), and the indicator light fails to glow. This implies 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 applied towards the control electrode (known as a trigger, and the applied voltage is known as 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 (which is, K is turned on again), the indicator light still glows. This implies that the thyristor can carry on and conduct. At this time, 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 applied towards the control electrode, a reverse voltage is applied involving the anode and cathode, and the indicator light fails to glow at this time. This implies that the thyristor will not be conducting and may reverse blocking.

5. In summary

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

2) Once the thyristor is subjected to a forward anode voltage, the thyristor will only conduct once the gate is subjected to a forward voltage. At this time, the thyristor is within the forward conduction state, the thyristor characteristic, which is, the controllable characteristic.

3) Once the thyristor is turned on, as long as there exists a specific forward anode voltage, the thyristor will remain turned on whatever the gate voltage. Which is, right after the thyristor is turned on, the gate will lose its function. The gate only functions as a trigger.

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

5) The problem for the thyristor to conduct is the fact that a forward voltage should be applied involving the anode and the cathode, as well as an appropriate forward voltage also need to be applied involving the gate and the cathode. To change off a conducting thyristor, the forward voltage involving the anode and cathode must be stop, or perhaps the voltage must be reversed.

Working principle of thyristor

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

1. If a forward voltage is applied involving 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. If a forward voltage is applied towards the control electrode at this time, BG1 is triggered to create 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 brought to BG1 for amplification then brought to BG2 for amplification again. Such repeated amplification forms an essential positive feedback, causing both BG1 and BG2 to get in a saturated conduction state quickly. A big current appears inside the emitters of these two transistors, which is, the anode and cathode in the thyristor (the dimensions of the current is actually based on the dimensions of the stress and the dimensions of Ea), therefore the thyristor is entirely turned on. This conduction process is finished in a really limited time.
2. After the thyristor is turned on, 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 really is still inside the conductive state. Therefore, the purpose of the control electrode is only to trigger the thyristor to transform on. Once the thyristor is turned on, the control electrode loses its function.
3. The only way to switch off the turned-on thyristor would be to lessen the anode current that it is inadequate to maintain the positive feedback process. How you can lessen the anode current would be to stop the forward power supply Ea or reverse the link of Ea. The minimum anode current necessary to keep the thyristor inside the conducting state is known as the holding current in the thyristor. Therefore, as it happens, as 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 include 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.

Working conditions:

The work of the 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 transform on or off.

Application areas

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

Thyristors are mainly used 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 accomplish current amplification.

The thyristor is turned on or off by managing the trigger voltage in 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 in some cases, because of their different structures and functioning principles, they have got noticeable variations in performance and use 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-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 a wonderful thyristor supplier. It is 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.