Specifically what is a thyristor?

A thyristor is really a high-power semiconductor device, also known as a silicon-controlled rectifier. Its structure includes 4 quantities of semiconductor elements, including three PN junctions corresponding towards the Anode, Cathode, and control electrode Gate. These three poles would be 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 a variety of electronic circuits, such as controllable rectification, AC voltage regulation, contactless electronic switches, inverters, and frequency conversion.

The graphical symbol of any Thyristor is generally represented by the text symbol “V” or “VT” (in older standards, the letters “SCR”). In addition, derivatives of thyristors also include fast thyristors, bidirectional thyristors, reverse conduction thyristors, and lightweight-controlled thyristors. The functioning condition in the thyristor is the fact that whenever 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 used 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 will not light up. This shows 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, along with a forward voltage is used towards the control electrode (known as a trigger, and also 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 excited, even when the voltage on the control electrode is removed (that is, K is excited again), the indicator light still glows. This shows that the thyristor can still conduct. At the moment, 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 also the indicator light will not light up at the moment. This shows that the thyristor is not really conducting and will reverse blocking.

5. In summary

1) If the thyristor is put through a reverse anode voltage, the thyristor is within 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 simply conduct when the gate is put through a forward voltage. At the moment, the thyristor is within the forward conduction state, the thyristor characteristic, that is, the controllable characteristic.

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

4) If the thyristor is on, and also 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 ought to be applied between the anode and also the cathode, as well as an appropriate forward voltage ought to be applied between the gate and also the cathode. To transform off a conducting thyristor, the forward voltage between the anode and cathode should be stop, or even the voltage should be reversed.

Working principle of thyristor

A thyristor is actually an exclusive triode made up of three PN junctions. It could be equivalently viewed as comprising a PNP transistor (BG2) as well as an NPN transistor (BG1).

1. When 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 continues to be 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, along with a ß1Ig current is obtained in its collector. This current is precisely the base current of BG2. After amplification by BG2, a ß1ß2Ig current is going to be brought in 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 large current appears within the emitters of the two transistors, that is, the anode and cathode in the thyristor (the dimensions of the current is in fact determined by the dimensions of the load and the dimensions of Ea), therefore the thyristor is completely excited. This conduction process is finished in an exceedingly short time.
2. Right after the thyristor is excited, its conductive state is going to be maintained by the positive feedback effect in the tube itself. Even when the forward voltage in the control electrode disappears, it really is still within the conductive state. Therefore, the function of the control electrode is just to trigger the thyristor to transform on. Once the thyristor is excited, the control electrode loses its function.
3. The only way to switch off the turned-on thyristor is always to decrease the anode current that it is inadequate to maintain the positive feedback process. The way to decrease the anode current is always to stop the forward power supply Ea or reverse the bond of Ea. The minimum anode current required to keep the thyristor within the conducting state is known as the holding current in the thyristor. Therefore, strictly speaking, as long as the anode current is less than the holding current, the thyristor can be turned off.

Exactly what is the distinction between a transistor along with a thyristor?

Structure

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

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

Operating conditions:

The work 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 at the gate to transform on or off.

Application areas

Transistors are commonly used in amplification, switches, oscillators, along with other elements of electronic circuits.

Thyristors are mainly found in electronic circuits such as controlled rectification, AC voltage regulation, contactless electronic switches, inverters, and frequency conversions.

Means 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 understand 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 used in similar applications in some instances, because of the different structures and functioning principles, they have noticeable variations in performance and use occasions.

Application scope of thyristor

• In power electronic equipment, thyristors can be used in frequency converters, motor controllers, welding machines, power supplies, etc.
• In the lighting field, thyristors can 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 can be used in motor controllers.

Supplier

PDDN Photoelectron Technology Co., Ltd is a wonderful thyristor supplier. It is actually one in the leading enterprises in the Home Accessory & Solar Power System, which can be fully involved in the progression 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.