Just what is a thyristor?

A thyristor is a high-power semiconductor device, also referred to as a silicon-controlled rectifier. Its structure consists of four quantities of semiconductor components, including 3 PN junctions corresponding towards the Anode, Cathode, and control electrode Gate. These 3 poles would be the critical parts of the thyristor, letting it 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 popular in a variety of electronic circuits, including controllable rectification, AC voltage regulation, contactless electronic switches, inverters, and frequency conversion.

The graphical symbol of the semiconductor device is usually represented from the text symbol “V” or “VT” (in older standards, the letters “SCR”). Additionally, derivatives of thyristors include fast thyristors, bidirectional thyristors, reverse conduction thyristors, and lightweight-controlled thyristors. The operating condition from the thyristor is the fact when 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 in between the anode and cathode (the anode is linked to the favorable pole from the power supply, as well as the cathode is connected to the negative pole of the power supply). But no forward voltage is applied to the control pole (i.e., K is disconnected), as well as the indicator light does not light up. 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 used to the control electrode (called a trigger, and the applied voltage is referred to 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 turned on, even when the voltage in the control electrode is taken off (that is certainly, K is excited again), the indicator light still glows. This implies that the thyristor can still conduct. At the moment, so that you can cut off the conductive thyristor, the power supply Ea has to be stop or reversed.

4. Reverse blocking

As shown in Figure d above, although a forward voltage is applied for the control electrode, a reverse voltage is used between the anode and cathode, as well as the indicator light fails to glow at this time. This implies that the thyristor is not really conducting and may reverse blocking.

5. To sum up

1) Once the thyristor is subjected to 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 only conduct once the gate is put through a forward voltage. At the moment, the thyristor is in the forward conduction state, the thyristor characteristic, that is, the controllable characteristic.

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

4) When 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 ought to be applied involving the anode and also the cathode, plus an appropriate forward voltage also need to be applied involving the gate and the cathode. To turn off a conducting thyristor, the forward voltage between the anode and cathode should be shut down, or perhaps the voltage has to be reversed.

Working principle of thyristor

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

1. In case a forward voltage is applied in between the anode and cathode in the thyristor without applying a forward voltage for 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. In case a forward voltage is used for 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 their 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 brought to BG1 for amplification and then sent 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 sizable current appears within the emitters of these two transistors, which is, the anode and cathode of the thyristor (the dimensions of the current is really dependant on the size of the stress and the dimensions of Ea), and so the thyristor is entirely turned on. This conduction process is done in an exceedingly limited time.
2. Right after the thyristor is switched on, its conductive state will likely be maintained from the positive feedback effect of the tube itself. Even if the forward voltage in the control electrode disappears, it is still in the conductive state. Therefore, the purpose of the control electrode is just to trigger the thyristor to turn on. After the thyristor is excited, the control electrode loses its function.
3. The only method to turn off the turned-on thyristor is to decrease the anode current that it is not enough to keep the positive feedback process. How you can lessen the anode current is always to cut off the forward power supply Ea or reverse the connection of Ea. The minimum anode current required to keep your thyristor inside the conducting state is referred to as the holding current from the thyristor. Therefore, as it happens, as long as the anode current is under the holding current, the thyristor could be turned off.

What exactly is the difference between a transistor and a thyristor?

Structure

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

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

Functioning conditions:

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

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

Application areas

Transistors are widely used in amplification, switches, oscillators, and other aspects of electronic circuits.

Thyristors are mainly used in electronic circuits like 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 attain current amplification.

The thyristor is switched on or off by controlling the trigger voltage of the control electrode to realize the switching function.

Circuit parameters

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

To summarize, although transistors and thyristors can be used in similar applications in some instances, due to their different structures and working principles, they may have noticeable differences 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.
• Within the lighting field, thyristors can be utilized in dimmers and lightweight control devices.
• In induction cookers and electric water heaters, thyristors may be used to control the current flow to 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 actually one of the leading enterprises in the Home Accessory & Solar Power System, which is fully involved in the development of power industry, intelligent operation and maintenance handling of power plants, solar power 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.