Just what is a thyristor?

A thyristor is really a high-power semiconductor device, also known as a silicon-controlled rectifier. Its structure includes four levels of semiconductor components, 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 widely used in different electronic circuits, including controllable rectification, AC voltage regulation, contactless electronic switches, inverters, and frequency conversion.

The graphical symbol of a Thyristor is usually represented through 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 in the thyristor is the fact when a forward voltage is used, 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 between the anode and cathode (the anode is linked 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 used to the control pole (i.e., K is disconnected), and also the indicator light fails to light up. This implies that the thyristor is not conducting and it has forward blocking capability.

2. Controllable conduction

As shown in Figure b above, when K is closed, and a forward voltage is used to the control electrode (referred to as a trigger, and also the applied voltage is called trigger voltage), the indicator light turns on. This means that the transistor can control conduction.

3. Continuous conduction

As shown in Figure c above, after the thyristor is turned on, even when the voltage in the control electrode is removed (that is, K is turned on again), the indicator light still glows. This implies that the thyristor can continue to conduct. Currently, to be able to stop the conductive thyristor, the power supply Ea should be stop or reversed.

4. Reverse blocking

As shown in Figure d above, although a forward voltage is used to the control electrode, a reverse voltage is used between the anode and cathode, and also the indicator light fails to light up at this time. This implies that the thyristor is not conducting and will reverse blocking.

5. To sum up

1) If 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) If the thyristor is subjected to a forward anode voltage, the thyristor will simply conduct if the gate is subjected to a forward voltage. Currently, the thyristor is within the forward conduction state, which is the thyristor characteristic, that is, the controllable characteristic.

3) If the thyristor is turned on, so long as there is a specific forward anode voltage, the thyristor will always be 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 needs 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 should be stop, or perhaps the voltage should be reversed.

Working principle of thyristor

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

1. When a forward voltage is used 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 turned off because BG1 has no base current. When a forward voltage is used to the control electrode at this time, BG1 is triggered to create a base 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 will be brought in 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 sizable current appears inside the emitters of the two transistors, that is, the anode and cathode in the thyristor (how big the current is actually determined by how big the burden and how big Ea), so the thyristor is entirely turned on. This conduction process is done in a really short time.
2. Following the thyristor is turned on, its conductive state will be maintained through the positive feedback effect in the tube itself. Even when the forward voltage in 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 transform on. When the thyristor is turned on, the control electrode loses its function.
3. The best way to turn off the turned-on thyristor would be to lessen the anode current that it is not enough to keep up the positive feedback process. The way to lessen the anode current would be to stop the forward power supply Ea or reverse the link of Ea. The minimum anode current needed to keep your thyristor inside the conducting state is called the holding current in the thyristor. Therefore, as it happens, so long as the anode current is lower than the holding current, the thyristor can be turned off.

Exactly what is the distinction between a transistor and a thyristor?

Structure

Transistors usually consist of 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.

Working conditions:

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

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

Application areas

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

Thyristors are mostly utilized 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 turned on or off by manipulating the trigger voltage in the control electrode to understand the switching function.

Circuit parameters

The circuit parameters of thyristors are based on 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, because of the different structures and operating principles, they may have noticeable variations 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.
• Inside the lighting field, thyristors may 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 may be used in motor controllers.

Supplier

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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.