So what is a thyristor?

A thyristor is actually a high-power semiconductor device, also referred to as a silicon-controlled rectifier. Its structure consists of 4 quantities of semiconductor components, including 3 PN junctions corresponding to the Anode, Cathode, and control electrode Gate. These 3 poles are definitely 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 operating status. Therefore, thyristors are commonly used in a variety of electronic circuits, including controllable rectification, AC voltage regulation, contactless electronic switches, inverters, and frequency conversion.

The graphical symbol of the silicon-controlled rectifier is normally represented from 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-controlled thyristors. The operating condition in the thyristor is the fact that whenever 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 attached 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 applied to the control pole (i.e., K is disconnected), as well as the indicator light fails to glow. This implies 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 applied to the control electrode (referred to as a trigger, as well as the applied voltage is known as trigger voltage), the indicator light switches on. Because of this the transistor can control conduction.

3. Continuous conduction

As shown in Figure c above, right after the thyristor is excited, even when the voltage in the control electrode is taken away (that is certainly, K is excited again), the indicator light still glows. This implies that the thyristor can continue to conduct. Currently, in order 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 involving the anode and cathode, as well as the indicator light fails to glow at the moment. This implies that the thyristor is not really conducting and can reverse blocking.

5. In conclusion

1) Once the thyristor is exposed to a reverse anode voltage, the thyristor is in a reverse blocking state whatever voltage the gate is exposed to.

2) Once the thyristor is exposed to a forward anode voltage, the thyristor will simply conduct once the gate is exposed to a forward voltage. Currently, the thyristor is incorporated in the forward conduction state, the thyristor characteristic, that is certainly, the controllable characteristic.

3) Once the thyristor is excited, provided that there is a specific forward anode voltage, the thyristor will remain excited whatever the gate voltage. Which is, right after the thyristor is excited, the gate will lose its function. The gate only works as a trigger.

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

5) The disorder for your thyristor to conduct is the fact that a forward voltage needs to be applied involving the anode as well as the cathode, as well as an appropriate forward voltage should also be applied involving the gate as well as the cathode. To turn off a conducting thyristor, the forward voltage involving the anode and cathode should be shut down, or even the voltage should be reversed.

Working principle of thyristor

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

1. When a forward voltage is applied involving 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 turned off because BG1 has no base current. When a forward voltage is applied to the control electrode at the moment, 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 likely be brought in the collector of BG2. This current is brought to BG1 for amplification and then brought 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 big current appears inside the emitters of the two transistors, that is certainly, the anode and cathode in the thyristor (how big the current is really determined by how big the load and how big Ea), and so the thyristor is totally excited. This conduction process is completed in a really short period of time.
2. Right after the thyristor is excited, its conductive state will likely be maintained from 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 function of the control electrode is only to trigger the thyristor to transform on. When the thyristor is excited, the control electrode loses its function.
3. The only way to shut off the turned-on thyristor is to reduce the anode current so that it is inadequate to maintain the positive feedback process. How you can reduce the anode current is to shut down the forward power supply Ea or reverse the bond of Ea. The minimum anode current necessary to maintain the thyristor inside the conducting state is known as the holding current in the thyristor. Therefore, as it happens, provided that the anode current is under the holding current, the thyristor can be turned off.

What exactly is the distinction between a transistor along with a thyristor?

Structure

Transistors usually consist of 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 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 commonly used in amplification, switches, oscillators, as well as other elements of electronic circuits.

Thyristors are mostly 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 comprehend the switching function.

Circuit parameters

The circuit parameters of thyristors are related to 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 the different structures and operating principles, they may have 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 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 an excellent thyristor supplier. It is actually one in the leading enterprises in the Home Accessory & Solar Power System, which is fully involved in the progression 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 looking for high-quality thyristor, please feel free to contact us and send an inquiry.