So what is a thyristor?

A thyristor is really a high-power semiconductor device, also referred to as a silicon-controlled rectifier. Its structure includes 4 levels of semiconductor materials, including three PN junctions corresponding to 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, including controllable rectification, AC voltage regulation, contactless electronic switches, inverters, and frequency alteration.

The graphical symbol of a semiconductor device is normally represented by 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 light-controlled thyristors. The functioning condition in the thyristor is the fact each time a forward voltage is applied, 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 used 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 applied to the control pole (i.e., K is disconnected), and the indicator light will not illuminate. 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, as well as a forward voltage is applied to the control electrode (known as a trigger, and the applied voltage is called trigger voltage), the indicator light turns on. Because of this the transistor can control conduction.

3. Continuous conduction

As shown in Figure c above, right after the thyristor is excited, whether or not the voltage around the control electrode is taken away (that is certainly, K is excited again), the indicator light still glows. This implies that the thyristor can still conduct. At this time, to be able to shut down the conductive thyristor, the power supply Ea should be shut down or reversed.

4. Reverse blocking

As shown in Figure d above, although a forward voltage is applied to the control electrode, a reverse voltage is applied between the anode and cathode, and the indicator light will not illuminate at this time. This implies that the thyristor will not be conducting and may reverse blocking.

5. In summary

1) If the thyristor is subjected to a reverse anode voltage, the thyristor is at a reverse blocking state whatever voltage the gate is subjected to.

2) If the thyristor is subjected to a forward anode voltage, the thyristor is only going to conduct when the gate is subjected to a forward voltage. At this time, the thyristor is within the forward conduction state, the thyristor characteristic, that is certainly, the controllable characteristic.

3) If the thyristor is excited, so long as you will find a specific forward anode voltage, the thyristor will stay excited no matter the gate voltage. Which is, right after the thyristor is excited, the gate will lose its function. The gate only serves 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 problem for your thyristor to conduct is the fact a forward voltage ought to be applied between the anode and the cathode, and an appropriate forward voltage should also be applied between the gate and the cathode. To change off a conducting thyristor, the forward voltage between the anode and cathode should be shut down, or perhaps the voltage should be reversed.

Working principle of thyristor

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

1. If a forward voltage is applied between the anode and cathode in the thyristor without applying a forward voltage to 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 applied to the control electrode at this time, BG1 is triggered to generate 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 is going to be introduced 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 enter a saturated conduction state quickly. A big current appears within the emitters of these two transistors, that is certainly, the anode and cathode in the thyristor (the size of the current is actually determined by the size of the load and the size of Ea), therefore the thyristor is entirely excited. This conduction process is completed in an exceedingly short time.
2. Following 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 is actually still within the conductive state. Therefore, the purpose of the control electrode is only to trigger the thyristor to turn on. Once the thyristor is excited, the control electrode loses its function.
3. The only way to turn off the turned-on thyristor is always to decrease the anode current so that it is inadequate to maintain the positive feedback process. The best way to decrease the anode current is always to shut down the forward power supply Ea or reverse the connection of Ea. The minimum anode current necessary to keep the thyristor within the conducting state is called the holding current in the thyristor. Therefore, strictly speaking, so long as the anode current is less than the holding current, the thyristor may be switched off.

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

Structure

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

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

Functioning conditions:

The work of a transistor depends on electrical signals to control its closing and opening, 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, as well as other elements of electronic circuits.

Thyristors are mainly found in electronic circuits including 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 achieve 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 related to stability and reliability and often have higher turn-off voltage and larger on-current.

To summarize, although transistors and thyristors can be utilized in similar applications in some instances, because of the different structures and functioning principles, they may have noticeable variations in performance and utilize 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 could be used to control the current flow to 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 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 handling of power plants, solar power and related solar products manufacturing.

It accepts payment via Charge 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 looking for high-quality thyristor, please feel free to contact us and send an inquiry.