What is a thyristor?

A thyristor is really a high-power semiconductor device, also referred to as a silicon-controlled rectifier. Its structure includes four quantities of semiconductor elements, including 3 PN junctions corresponding to the Anode, Cathode, and control electrode Gate. These 3 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 functioning status. Therefore, thyristors are widely used in a variety of electronic circuits, including controllable rectification, AC voltage regulation, contactless electronic switches, inverters, and frequency conversion.

The graphical symbol of a Thyristor is generally represented through 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-weight-controlled thyristors. The functioning condition from the thyristor is the fact that 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 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 attached to the negative pole from 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 glow. This implies that the thyristor will not be conducting and it has 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, as well as the applied voltage is referred to as trigger voltage), the indicator light switches on. Which means that the transistor can control conduction.

3. Continuous conduction

As shown in Figure c above, after the thyristor is turned on, even if the voltage on the control electrode is removed (that is certainly, K is turned on again), the indicator light still glows. This implies that the thyristor can continue to conduct. At the moment, in order to shut down the conductive thyristor, the power supply Ea must be shut down 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 involving the anode and cathode, as well as the indicator light does not glow at this time. This implies that the thyristor will not be conducting and can reverse blocking.

5. To sum up

1) When the thyristor is subjected to a reverse anode voltage, the thyristor is within a reverse blocking state whatever voltage the gate is subjected to.

2) When the thyristor is subjected to a forward anode voltage, the thyristor will simply conduct once the gate is subjected to a forward voltage. At the moment, the thyristor is within the forward conduction state, which is the thyristor characteristic, that is certainly, the controllable characteristic.

3) When the thyristor is turned on, so long as you will find a specific forward anode voltage, the thyristor will always be turned on no matter the gate voltage. That is, after the thyristor is turned on, the gate will lose its function. The gate only functions as a trigger.

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

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

Working principle of thyristor

A thyristor is essentially a unique triode made from three PN junctions. It may be equivalently thought to be comprising a PNP transistor (BG2) as well as an NPN transistor (BG1).

1. If a forward voltage is applied involving the anode and cathode from the thyristor without applying a forward voltage to the control electrode, although both BG1 and BG2 have forward voltage applied, the thyristor is still switched off because BG1 has no base current. If a forward voltage is applied to the control electrode at this time, BG1 is triggered to create basics 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 will likely be introduced the collector of BG2. This current is delivered to BG1 for amplification then delivered 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 sizable current appears inside the emitters of the two transistors, that is certainly, the anode and cathode from the thyristor (the dimensions of the current is actually dependant on the dimensions of the load and the dimensions of Ea), therefore the thyristor is completely turned on. This conduction process is done in an exceedingly short time.
2. Following the thyristor is turned on, its conductive state will likely be maintained through the positive feedback effect from the tube itself. Even when the forward voltage from the control electrode disappears, it really is still inside the conductive state. Therefore, the purpose of the control electrode is only to trigger the thyristor to change on. After the thyristor is turned 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 maintain 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 the thyristor inside the conducting state is referred to as the holding current from the thyristor. Therefore, as it happens, so long as the anode current is less than the holding current, the thyristor could be switched off.

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

Structure

Transistors usually include a PNP or NPN structure made from 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 depends on electrical signals to control its closing and opening, allowing fast switching operations.

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

Application areas

Transistors are widely used in amplification, switches, oscillators, and 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.

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 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 sum up, although transistors and thyristors can be used in similar applications sometimes, because of their different structures and functioning principles, they have noticeable differences 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.
• In the lighting field, thyristors can be used in dimmers and light-weight control devices.
• In induction cookers and electric water heaters, thyristors can 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 actually one from the leading enterprises in the Home Accessory & Solar Power System, which can be fully working in the progression of power industry, intelligent operation and maintenance management of power plants, solar power panel 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. Should you be looking for high-quality thyristor, please feel free to contact us and send an inquiry.