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 materials, including three PN junctions corresponding towards the Anode, Cathode, and control electrode Gate. These three 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 functioning status. Therefore, thyristors are popular in a variety of electronic circuits, such as controllable rectification, AC voltage regulation, contactless electronic switches, inverters, and frequency alteration.

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 lightweight-controlled thyristors. The functioning condition of the thyristor is that each time 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 used between the anode and cathode (the anode is connected to the favorable pole of the power supply, and also 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), and also the indicator light does not light up. This implies that the thyristor is not really conducting and has forward blocking capability.

2. Controllable conduction

As shown in Figure b above, when K is closed, and a forward voltage is applied towards the control electrode (known 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, following the thyristor is switched on, even if the voltage on the control electrode is taken off (that is certainly, K is switched on again), the indicator light still glows. This implies that the thyristor can still 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, and also the indicator light does not light up currently. This implies that the thyristor is not really conducting and will reverse blocking.

5. In summary

1) Once the thyristor is subjected to a reverse anode voltage, the thyristor is within a reverse blocking state regardless of what voltage the gate is subjected to.

2) Once the thyristor is subjected to a forward anode voltage, the thyristor will only conduct if the gate is subjected to a forward voltage. At this time, the thyristor is within the forward conduction state, which is the thyristor characteristic, that is certainly, the controllable characteristic.

3) Once the thyristor is switched on, as long as there is a specific forward anode voltage, the thyristor will remain switched on no matter the gate voltage. That is certainly, following the thyristor is switched on, the gate will lose its function. The gate only serves as a trigger.

4) Once 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 that a forward voltage needs to be applied between the anode and also the cathode, as well as 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 has to be shut down, or the voltage has to be reversed.

Working principle of thyristor

A thyristor is basically an exclusive triode made from three PN junctions. It could be equivalently regarded as comprising a PNP transistor (BG2) as well as 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 remains switched off because BG1 has no base current. When a forward voltage is applied towards the control electrode currently, BG1 is triggered to generate a base current Ig. BG1 amplifies this current, and a ß1Ig current is obtained in the 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 delivered to BG1 for amplification and then delivered 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 large current appears in the emitters of the two transistors, that is certainly, the anode and cathode of the thyristor (how big the current is really determined by how big the burden and how big Ea), so the thyristor is entirely switched on. This conduction process is done in a really short period of time.
2. After 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 still in the conductive state. Therefore, the function of the control electrode is only to trigger the thyristor to transform on. Once the thyristor is switched on, the control electrode loses its function.
3. The only method to shut off the turned-on thyristor is to decrease the anode current so that it is inadequate to keep the positive feedback process. How you can decrease the anode current is to shut down the forward power supply Ea or reverse the bond of Ea. The minimum anode current required to maintain the thyristor in the conducting state is called the holding current of the thyristor. Therefore, strictly speaking, as long as the anode current is lower than the holding current, the thyristor could be switched 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 is made up of four PNPN structures of semiconductor materials, including anode, cathode, and control electrode.

Working conditions:

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

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

Application areas

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

Thyristors are mainly utilized in electronic circuits such as 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 switched on or off by controlling the trigger voltage of the control electrode to understand 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 sometimes, because of the different structures and functioning principles, they 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.
• In 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 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, which can be fully involved in the progression of power industry, intelligent operation and maintenance control over power plants, solar power 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.