Just what is a thyristor?

A thyristor is a high-power semiconductor device, also referred to as a silicon-controlled rectifier. Its structure includes four levels of semiconductor components, including 3 PN junctions corresponding towards the Anode, Cathode, and control electrode Gate. These 3 poles are 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 a variety of electronic circuits, including controllable rectification, AC voltage regulation, contactless electronic switches, inverters, and frequency conversion.

The graphical symbol of a 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-weight-controlled thyristors. The working condition of 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 is utilized between the anode and cathode (the anode is attached to the favorable pole of the power supply, as well as the cathode is attached to the negative pole of the power supply). But no forward voltage is applied towards the control pole (i.e., K is disconnected), as well as the indicator light fails to illuminate. This implies that the thyristor is not really 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 towards the control electrode (referred to as a trigger, as well as the applied voltage is referred to 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 switched on, whether or not the voltage around the control electrode is removed (that is certainly, K is switched on again), the indicator light still glows. This implies that the thyristor can continue to conduct. At this time, so that you can shut down the conductive thyristor, the power supply Ea has to be shut down or reversed.

4. Reverse blocking

As shown in Figure d above, although a forward voltage is applied towards the control electrode, a reverse voltage is applied between the anode and cathode, as well as the indicator light fails to illuminate at the moment. This implies that the thyristor is not really conducting and may reverse blocking.

5. In summary

1) When the thyristor is subjected to a reverse anode voltage, the thyristor is in 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 only conduct once the gate is subjected to a forward voltage. At this time, 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 regardless of the gate voltage. Which is, after the thyristor is switched on, the gate will lose its function. The gate only works as a trigger.

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

5) The problem for that thyristor to conduct is the fact that a forward voltage should be applied between the anode as well as the cathode, and an appropriate forward voltage should also be applied between the gate as well as the cathode. To change off a conducting thyristor, the forward voltage between the anode and cathode has to be shut down, or the voltage has to be reversed.

Working principle of thyristor

A thyristor is actually a unique triode composed of three PN junctions. It could be equivalently regarded as comprising a PNP transistor (BG2) and an NPN transistor (BG1).

1. When a forward voltage is applied between the anode and cathode of the thyristor without applying a forward voltage towards 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 towards the control electrode at the moment, BG1 is triggered to generate basics 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 brought to BG1 for amplification and after that brought to BG2 for amplification again. Such repeated amplification forms a crucial positive feedback, causing both BG1 and BG2 to enter a saturated conduction state quickly. A big current appears within the emitters of the two transistors, that is certainly, the anode and cathode of the thyristor (how big the current is actually dependant on how big the stress and how big Ea), therefore the thyristor is entirely switched on. This conduction process is done in an exceedingly short period of time.
2. After the thyristor is switched on, its conductive state will 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 within the conductive state. Therefore, the purpose of the control electrode is only to trigger the thyristor to transform on. When the thyristor is switched on, the control electrode loses its function.
3. The only method to switch off the turned-on thyristor is always to lessen the anode current 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 link of Ea. The minimum anode current necessary to keep your thyristor within the conducting state is referred to as the holding current of the thyristor. Therefore, as it happens, so long as the anode current is less than the holding current, the thyristor can be switched off.

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

Structure

Transistors usually include a PNP or NPN structure composed of three semiconductor materials.

The thyristor is composed of four PNPN structures of semiconductor materials, including anode, cathode, and control electrode.

Working conditions:

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

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

Application areas

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

Thyristors are mostly utilized 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 attain current amplification.

The thyristor is switched on or off by managing the trigger voltage of the control electrode to comprehend 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 summarize, although transistors and thyristors may be used in similar applications in some instances, because of their different structures and working 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.
• Inside the lighting field, thyristors may be used in dimmers and light-weight control devices.
• In induction cookers and electric water heaters, thyristors may be used to control the current flow towards 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 of the leading enterprises in the Home Accessory & Solar Power System, that is fully active in the development of power industry, intelligent operation and maintenance management of power plants, solar panel 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. If you are searching for high-quality thyristor, please feel free to contact us and send an inquiry.