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 four quantities of semiconductor materials, including 3 PN junctions corresponding to the Anode, Cathode, and control electrode Gate. These 3 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 operating status. Therefore, thyristors are popular in various electronic circuits, including controllable rectification, AC voltage regulation, contactless electronic switches, inverters, and frequency conversion.

The graphical symbol of a silicon-controlled rectifier is normally represented from 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 lightweight-controlled thyristors. The operating 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 utilized between the anode and cathode (the anode is connected to the favorable pole in the power supply, as well as the cathode is attached 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 will not light up. This shows that the thyristor is not 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 to the control electrode (known as 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, following the thyristor is excited, whether or not the voltage on the control electrode is taken away (that is, K is excited again), the indicator light still glows. This shows that the thyristor can carry on and conduct. At this time, so that you can stop the conductive thyristor, the power supply Ea must be stop 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, as well as the indicator light will not light up at the moment. This shows that the thyristor is not conducting and can reverse blocking.

5. In conclusion

1) If the thyristor is put through a reverse anode voltage, the thyristor is at a reverse blocking state no matter what voltage the gate is put through.

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

3) If the thyristor is excited, provided that there is a specific forward anode voltage, the thyristor will always be excited no matter the gate voltage. That is, following the thyristor is excited, the gate will lose its function. The gate only works as a trigger.

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

Working principle of thyristor

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

1. In case 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 turned off because BG1 has no base current. In case 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, 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 will 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 a vital positive feedback, causing both BG1 and BG2 to get in a saturated conduction state quickly. A large current appears inside the emitters of the two transistors, that is, the anode and cathode in the thyristor (how big the current is really dependant on how big the stress and how big Ea), so the thyristor is entirely excited. This conduction process is done in a really limited time.
2. Right after the thyristor is excited, its conductive state will be maintained from the positive feedback effect in the tube itself. Whether or not the forward voltage in the control electrode disappears, it is actually still inside 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 inadequate to maintain the positive feedback process. How you can decrease the anode current is to stop the forward power supply Ea or reverse the link of Ea. The minimum anode current needed to keep the thyristor inside the conducting state is known as the holding current in the thyristor. Therefore, strictly speaking, provided that the anode current is under the holding current, the thyristor could be turned off.

Exactly what is the difference between a transistor as well as a thyristor?

Structure

Transistors usually include a PNP or NPN structure made up 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 task of a transistor relies upon electrical signals to control its opening and closing, allowing fast switching operations.

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

Application areas

Transistors are popular in amplification, switches, oscillators, as well as other elements of electronic circuits.

Thyristors are mainly used 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 accomplish 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 in most cases have higher turn-off voltage and larger on-current.

To sum up, although transistors and thyristors can be used in similar applications sometimes, because of their different structures and operating principles, they have got noticeable variations in performance and utilize occasions.

Application scope of thyristor

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

Supplier

PDDN Photoelectron Technology Co., Ltd is an excellent thyristor supplier. It is 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 panel 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.