Specifically what is a thyristor?

A thyristor is a high-power semiconductor device, also called a silicon-controlled rectifier. Its structure consists of four levels of semiconductor elements, including three PN junctions corresponding towards the Anode, Cathode, and control electrode Gate. These three poles are the critical parts in the thyristor, allowing it to 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 various electronic circuits, like controllable rectification, AC voltage regulation, contactless electronic switches, inverters, and frequency alteration.

The graphical symbol of any Thyristor is usually represented by the text symbol “V” or “VT” (in older standards, the letters “SCR”). Furthermore, derivatives of thyristors also include fast thyristors, bidirectional thyristors, reverse conduction thyristors, and light-weight-controlled thyristors. The functioning condition in the thyristor is the fact that each time 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 connected to the favorable pole in the power supply, as well as the cathode is connected to the negative pole in the power supply). But no forward voltage is used towards the control pole (i.e., K is disconnected), as well as the indicator light does not light up. This demonstrates that the thyristor will not be conducting and contains 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 (known as a trigger, as well as the applied voltage is known as 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 (which is, K is switched on again), the indicator light still glows. This demonstrates that the thyristor can continue to conduct. At the moment, to be able to shut down the conductive thyristor, the power supply Ea has to be shut down 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 involving the anode and cathode, as well as the indicator light does not light up at this time. This demonstrates that the thyristor will not be conducting and will reverse blocking.

5. To sum up

1) If the thyristor is subjected to a reverse anode voltage, the thyristor is in 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 simply conduct if the gate is subjected to a forward voltage. At the moment, the thyristor is in the forward conduction state, the thyristor characteristic, which is, the controllable characteristic.

3) If the thyristor is switched on, provided that there is a specific forward anode voltage, the thyristor will always be switched on no matter the gate voltage. That is, after the thyristor is switched on, the gate will lose its function. The gate only serves as a trigger.

4) If 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 your thyristor to conduct is the fact that a forward voltage should be applied involving the anode as well as the cathode, plus an appropriate forward voltage should also be applied involving the gate as well as the cathode. To change off a conducting thyristor, the forward voltage involving the anode and cathode has to be shut down, or perhaps the voltage has to be reversed.

Working principle of thyristor

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

1. If a forward voltage is used 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 is still switched off because BG1 has no base current. If a forward voltage is used towards the control electrode at this time, BG1 is triggered to produce basics 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 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 crucial positive feedback, causing both BG1 and BG2 to enter a saturated conduction state quickly. A sizable current appears in the emitters of the two transistors, which is, the anode and cathode in the thyristor (the size of the current is actually dependant on the size of the load and the size of Ea), therefore the thyristor is totally switched on. This conduction process is completed in a very short time.
2. Right after the thyristor is switched on, its conductive state will be maintained by the positive feedback effect in the tube itself. Even if the forward voltage in the control electrode disappears, it really is still in the conductive state. Therefore, the purpose of the control electrode is only to trigger the thyristor to transform on. When the thyristor is switched on, the control electrode loses its function.
3. The best way to turn off the turned-on thyristor is always 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 always to shut down the forward power supply Ea or reverse the connection of Ea. The minimum anode current required to keep the thyristor in the conducting state is known as 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 switched off.

What is the difference between a transistor along with a thyristor?

Structure

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

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

Application areas

Transistors are commonly used in amplification, switches, oscillators, as well as 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 attain current amplification.

The thyristor is switched on or off by manipulating 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 summarize, although transistors and thyristors can be utilized in similar applications sometimes, because of their different structures and functioning 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 can 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 really is one in the leading enterprises in the Home Accessory & Solar Power System, which is fully working in the growth and development of power industry, intelligent operation and maintenance control over power plants, solar power 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. Should you be looking for high-quality thyristor, please feel free to contact us and send an inquiry.