So what is a thyristor?

A thyristor is a high-power semiconductor device, also referred to as a silicon-controlled rectifier. Its structure includes 4 quantities of semiconductor elements, including 3 PN junctions corresponding for 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 different electronic circuits, including controllable rectification, AC voltage regulation, contactless electronic switches, inverters, and frequency conversion.

The graphical symbol of any Thyristor is usually represented from the text symbol “V” or “VT” (in older standards, the letters “SCR”). In addition, derivatives of thyristors also include fast thyristors, bidirectional thyristors, reverse conduction thyristors, and lightweight-controlled thyristors. The working condition of the thyristor is 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 is utilized in between the anode and cathode (the anode is connected to the favorable pole of the power supply, and also the cathode is linked to the negative pole of the power supply). But no forward voltage is applied for the control pole (i.e., K is disconnected), and also the indicator light does not light up. This implies 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, and a forward voltage is applied for the control electrode (called a trigger, and also the applied voltage is known as trigger voltage), the indicator light turns on. Which means that the transistor can control conduction.

3. Continuous conduction

As shown in Figure c above, after the thyristor is switched on, whether or not the voltage in the control electrode is taken away (that is certainly, K is switched on again), the indicator light still glows. This implies that the thyristor can continue to conduct. Currently, to be able 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 for the control electrode, a reverse voltage is applied in between the anode and cathode, and also the indicator light does not light up at this time. This implies that the thyristor will not be conducting and will reverse blocking.

5. To sum up

1) When the thyristor is put through a reverse anode voltage, the thyristor is in a reverse blocking state regardless of what voltage the gate is put through.

2) When the thyristor is put through a forward anode voltage, the thyristor will only conduct when the gate is put through a forward voltage. Currently, the thyristor is incorporated in the forward conduction state, the thyristor characteristic, that is certainly, the controllable characteristic.

3) When the thyristor is switched on, so long as you will find a specific forward anode voltage, the thyristor will always be switched on whatever the gate voltage. Which is, after the thyristor is switched on, the gate will lose its function. The gate only functions as a trigger.

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

5) The condition for your thyristor to conduct is that a forward voltage should be applied in between the anode and also the cathode, as well as an appropriate forward voltage also need to be applied in between the gate and also the cathode. To transform off a conducting thyristor, the forward voltage in between the anode and cathode should be shut down, or the voltage should be reversed.

Working principle of thyristor

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

1. When a forward voltage is applied in between the anode and cathode of the thyristor without applying a forward voltage for the control electrode, although both BG1 and BG2 have forward voltage applied, the thyristor is still switched off because BG1 has no base current. When a forward voltage is applied for the control electrode at this time, BG1 is triggered to produce basics current Ig. BG1 amplifies this current, and a ß1Ig current is obtained in their 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 sent 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 enter a saturated conduction state quickly. A big current appears in the emitters of the two transistors, that is certainly, the anode and cathode of the thyristor (the dimensions of the current is actually based on the dimensions of the burden and the dimensions of Ea), therefore the thyristor is totally switched on. This conduction process is finished in a really limited time.
2. Following the thyristor is switched on, its conductive state is going to be maintained from the positive feedback effect of the tube itself. Even when the forward voltage of the control electrode disappears, it is actually still in the conductive state. Therefore, the function of the control electrode is simply to trigger the thyristor to turn on. After the thyristor is switched on, the control electrode loses its function.
3. The best way 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. How you can lessen the anode current is always to shut down the forward power supply Ea or reverse the connection of Ea. The minimum anode current necessary to keep your thyristor in the conducting state is known as the holding current of the thyristor. Therefore, strictly speaking, so long as the anode current is less than the holding current, the thyristor can be switched off.

What is the distinction between a transistor and a thyristor?

Structure

Transistors usually include a PNP or NPN structure made from three semiconductor materials.

The thyristor consists 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 closing and opening, allowing fast switching operations.

The thyristor demands a forward voltage and a trigger current at the gate to turn on or off.

Application areas

Transistors are popular in amplification, switches, oscillators, along with other aspects of electronic circuits.

Thyristors are mainly found in electronic circuits including controlled rectification, AC voltage regulation, contactless electronic switches, inverters, and frequency conversions.

Method of working

The transistor controls the collector current by holding the base current to achieve current amplification.

The thyristor is switched on or off by manipulating the trigger voltage of 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 cases, due to their different structures and working principles, they have got 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.
• Within the lighting field, thyristors may be used in dimmers and lightweight control devices.
• In induction cookers and electric water heaters, thyristors could be used to control the current flow for 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 of the leading enterprises in the Home Accessory & Solar Power System, that is fully involved in the development of power industry, intelligent operation and maintenance management of power plants, solar power and related solar products manufacturing.

It accepts payment via Charge 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.