So what is a thyristor?

A thyristor is actually a high-power semiconductor device, also called a silicon-controlled rectifier. Its structure contains four levels of semiconductor materials, including three PN junctions corresponding to the Anode, Cathode, and control electrode Gate. These three poles are definitely the critical parts in 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 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 conversion.

The graphical symbol of the silicon-controlled rectifier is generally represented from the text symbol “V” or “VT” (in older standards, the letters “SCR”). Furthermore, derivatives of thyristors also have 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 needs 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 attached to the favorable pole in the power supply, and also 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), and also the indicator light will not illuminate. This demonstrates that the thyristor will not be 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 (referred to as a trigger, and also 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, whether or not the voltage on the control electrode is taken off (that is certainly, K is turned on again), the indicator light still glows. This demonstrates that the thyristor can carry on and conduct. At this time, in order to 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, and also the indicator light will not illuminate at this time. This demonstrates that the thyristor will not be conducting and may reverse blocking.

5. To sum up

1) If 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) If the thyristor is exposed to a forward anode voltage, the thyristor is only going to conduct if the gate is exposed to a forward voltage. At this time, the thyristor is incorporated in the forward conduction state, which is the thyristor characteristic, that is certainly, the controllable characteristic.

3) If the thyristor is turned on, provided that there exists 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 works as a trigger.

4) If the thyristor is on, and also the primary circuit voltage (or current) decreases to close to zero, the thyristor turns off.

5) The problem for that thyristor to conduct is the fact a forward voltage ought to be applied between the anode and also the cathode, plus an appropriate forward voltage should also be applied between the gate and also the cathode. To transform off a conducting thyristor, the forward voltage between the anode and cathode must be stop, or the voltage must be reversed.

Working principle of thyristor

A thyristor is basically an exclusive triode composed of three PN junctions. It could be equivalently regarded as consisting of a PNP transistor (BG2) plus an NPN transistor (BG1).

1. When 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 continues to be switched off because BG1 has no base current. When a forward voltage is applied to the control electrode at this time, BG1 is triggered to create a base current Ig. BG1 amplifies this current, as well as 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 sent to BG1 for amplification then sent to BG2 for amplification again. Such repeated amplification forms an essential positive feedback, causing both BG1 and BG2 to get into a saturated conduction state quickly. A large current appears within the emitters of the two transistors, that is certainly, the anode and cathode in the thyristor (the dimensions of the current is really based on the dimensions of the burden and the dimensions of Ea), so the thyristor is completely turned on. This conduction process is finished in an exceedingly short period of time.
2. Following the thyristor is turned on, its conductive state will be maintained from the positive feedback effect in the tube itself. Even if the forward voltage in the control electrode disappears, it is still within the conductive state. Therefore, the purpose of the control electrode is simply to trigger the thyristor to change on. When the thyristor is turned on, the control electrode loses its function.
3. The only way to shut off the turned-on thyristor is always to lessen the anode current that it is not enough to keep up the positive feedback process. How you can lessen the anode current is always to stop the forward power supply Ea or reverse the connection of Ea. The minimum anode current needed to maintain the thyristor within the conducting state is known as the holding current in the thyristor. Therefore, strictly speaking, provided that the anode current is less 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 contain 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.

Working conditions:

The job of the transistor depends on electrical signals to control its opening and closing, allowing fast switching operations.

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

Application areas

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

Thyristors are mostly found in electronic circuits including 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 attain current amplification.

The thyristor is turned on or off by manipulating 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 summarize, although transistors and thyristors may be used in similar applications in some instances, due to their different structures and functioning principles, they may have noticeable differences in performance and make use of 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 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 wonderful thyristor supplier. It really is one in the leading enterprises in the Home Accessory & Solar Power System, which is fully active in the growth and development 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.