Specifically what is a thyristor?

A thyristor is actually a high-power semiconductor device, also called 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 are the critical parts from 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 working status. Therefore, thyristors are widely used in various electronic circuits, like controllable rectification, AC voltage regulation, contactless electronic switches, inverters, and frequency conversion.

The graphical symbol of any Thyristor is usually represented through 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 working condition from the thyristor is the fact that each time 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 connected to the favorable pole from the power supply, as well as the cathode is linked to the negative pole from the power supply). But no forward voltage is applied towards the control pole (i.e., K is disconnected), as well as the indicator light does not illuminate. This demonstrates that the thyristor is not really conducting and contains forward blocking capability.

2. Controllable conduction

As shown in Figure b above, when K is closed, as well as a forward voltage is applied towards the control electrode (called a trigger, as well as the applied voltage is known as trigger voltage), the indicator light turns on. Because of this the transistor can control conduction.

3. Continuous conduction

As shown in Figure c above, after the thyristor is turned on, even when the voltage in the control electrode is removed (which is, K is turned on again), the indicator light still glows. This demonstrates that the thyristor can carry on and conduct. Currently, in order to cut off the conductive thyristor, the power supply Ea should be cut off 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, as well as the indicator light does not illuminate at the moment. This demonstrates that the thyristor is not really conducting and will reverse blocking.

5. In summary

1) Once the thyristor is exposed to a reverse anode voltage, the thyristor is within a reverse blocking state regardless of what voltage the gate is exposed to.

2) Once the thyristor is exposed to a forward anode voltage, the thyristor is only going to conduct once the gate is exposed to a forward voltage. Currently, the thyristor is incorporated in the forward conduction state, the thyristor characteristic, which is, the controllable characteristic.

3) Once the thyristor is turned on, as long as you will find a specific forward anode voltage, the thyristor will remain turned on regardless of the gate voltage. That is certainly, after the thyristor is turned on, the gate will lose its function. The gate only serves as a trigger.

4) Once the thyristor is on, as well as 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 that a forward voltage needs to 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 turn off a conducting thyristor, the forward voltage involving the anode and cathode should be cut off, or the voltage should be reversed.

Working principle of thyristor

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

1. In case a forward voltage is applied involving the anode and cathode from 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. In case a forward voltage is applied towards the control electrode at the moment, BG1 is triggered to create a base current Ig. BG1 amplifies this current, as well as a ß1Ig current is obtained in the 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 and 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 big current appears in the emitters of the two transistors, which is, the anode and cathode from the thyristor (how big the current is in fact determined by how big the load and how big Ea), and so the thyristor is entirely turned on. This conduction process is completed in an exceedingly short period of time.
2. Right after the thyristor is turned on, its conductive state is going to be maintained through the positive feedback effect from the tube itself. Even when the forward voltage from the control electrode disappears, it is still in the conductive state. Therefore, the purpose of the control electrode is simply to trigger the thyristor to turn on. After the thyristor is turned on, the control electrode loses its function.
3. The only method to shut off the turned-on thyristor is always to lessen the anode current so that it is inadequate to keep up the positive feedback process. The best way to lessen the anode current is always to cut off the forward power supply Ea or reverse the bond of Ea. The minimum anode current necessary to maintain the thyristor in the conducting state is known as the holding current from the thyristor. Therefore, strictly speaking, as long as the anode current is lower than the holding current, the thyristor could be switched off.

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

Structure

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

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

Functioning conditions:

The job of any transistor relies upon electrical signals to control its opening and closing, allowing fast switching operations.

The thyristor needs a forward voltage as well as a trigger current at the gate to turn on or off.

Application areas

Transistors are widely used in amplification, switches, oscillators, along with other facets of electronic circuits.

Thyristors are mostly found 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 accomplish current amplification.

The thyristor is turned on or off by managing the trigger voltage from the control electrode to understand the switching function.

Circuit parameters

The circuit parameters of thyristors are based on stability and reliability and in most cases have higher turn-off voltage and larger on-current.

To sum up, although transistors and thyristors may be used in similar applications in some instances, because of their different structures and working principles, they have got noticeable differences in performance and use occasions.

Application scope of thyristor

• In power electronic equipment, thyristors may be used in frequency converters, motor controllers, welding machines, power supplies, etc.
• In the lighting field, thyristors may be used in dimmers and light control devices.
• In induction cookers and electric water heaters, thyristors could be used to control the current flow towards the heating element.
• In electric vehicles, transistors may be used in motor controllers.

Supplier

PDDN Photoelectron Technology Co., Ltd is a superb thyristor supplier. It is one from the leading enterprises in the Home Accessory & Solar Power System, that is fully involved in the progression of power industry, intelligent operation and maintenance management of 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. Should you be looking for high-quality thyristor, please feel free to contact us and send an inquiry.