Specifically what is a thyristor?

A thyristor is actually a high-power semiconductor device, also called a silicon-controlled rectifier. Its structure contains 4 quantities of semiconductor elements, including three PN junctions corresponding towards the Anode, Cathode, and control electrode Gate. These three poles are the critical parts in 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 operating status. Therefore, thyristors are popular in a variety of electronic circuits, like controllable rectification, AC voltage regulation, contactless electronic switches, inverters, and frequency conversion.

The graphical symbol of any semiconductor device is usually represented through the text symbol “V” or “VT” (in older standards, the letters “SCR”). Additionally, derivatives of thyristors also have fast thyristors, bidirectional thyristors, reverse conduction thyristors, and light-controlled thyristors. The operating condition in the thyristor is the fact that when 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 linked to the favorable pole in the power supply, and the cathode is linked to the negative pole in the power supply). But no forward voltage is applied towards the control pole (i.e., K is disconnected), and the indicator light will not glow. This shows that the thyristor will not be conducting and has forward blocking capability.

2. Controllable conduction

As shown in Figure b above, when K is closed, along with a forward voltage is applied towards the control electrode (known as a trigger, and 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, right after the thyristor is turned on, whether or not the voltage around the control electrode is taken off (that is certainly, K is turned on again), the indicator light still glows. This shows that the thyristor can still conduct. At this time, in order to cut off the conductive thyristor, the power supply Ea must be cut off 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 the indicator light will not glow at the moment. This shows that the thyristor will not be conducting and will reverse blocking.

5. In summary

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

2) When the thyristor is exposed to a forward anode voltage, the thyristor is only going to conduct if the gate is exposed to a forward voltage. At this time, the thyristor is within the forward conduction state, the thyristor characteristic, that is certainly, the controllable characteristic.

3) When the thyristor is turned on, provided that there is a specific forward anode voltage, the thyristor will stay turned on no matter the gate voltage. That is, right 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, and the primary circuit voltage (or current) decreases to close to zero, the thyristor turns off.

5) The disorder for that thyristor to conduct is the fact that a forward voltage should be applied between the anode and the cathode, plus an appropriate forward voltage ought to be applied between the gate and the cathode. To turn off a conducting thyristor, the forward voltage between the anode and cathode must be cut off, or even the voltage must be reversed.

Working principle of thyristor

A thyristor is basically an exclusive triode made up of three PN junctions. It can be equivalently regarded as composed of a PNP transistor (BG2) plus an NPN transistor (BG1).

1. When a forward voltage is applied between the anode and cathode in 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 at the moment, BG1 is triggered to generate basics current Ig. BG1 amplifies this current, along with 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 likely be brought in the collector of BG2. This current is sent to BG1 for amplification 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 sizable current appears in the emitters of these two transistors, that is certainly, the anode and cathode in the thyristor (how big the current is actually dependant on how big the load and how big Ea), therefore the thyristor is entirely turned on. This conduction process is done in a very short period of time.
2. After the thyristor is turned on, its conductive state will likely be maintained through the positive feedback effect in the tube itself. Whether or not the forward voltage in the control electrode disappears, it is actually still in the conductive state. Therefore, the purpose of the control electrode is simply to trigger the thyristor to transform on. When the thyristor is turned on, the control electrode loses its function.
3. The only method to switch off the turned-on thyristor is always to reduce the anode current so that it is inadequate to keep up the positive feedback process. How you can reduce the anode current is always to cut off the forward power supply Ea or reverse the link of Ea. The minimum anode current required to keep the thyristor in the conducting state is referred to as the holding current in the thyristor. Therefore, strictly speaking, provided that the anode current is less than the holding current, the thyristor may be switched off.

What is the distinction between a transistor along with a thyristor?

Structure

Transistors usually contain a PNP or NPN structure made up of three semiconductor materials.

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

Functioning conditions:

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

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

Application areas

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

Thyristors are mainly utilized in electronic circuits like 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 accomplish current amplification.

The thyristor is turned on or off by managing the trigger voltage in the control electrode to comprehend the switching function.

Circuit parameters

The circuit parameters of thyristors are related to stability and reliability and usually have higher turn-off voltage and larger on-current.

To sum up, although transistors and thyristors may be used in similar applications in some cases, because of their different structures and operating 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.
• Within the lighting field, thyristors may be used in dimmers and light control devices.
• In induction cookers and electric water heaters, thyristors can 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 an excellent thyristor supplier. It really is one in the leading enterprises in the Home Accessory & Solar Power System, which can be fully involved in the growth and development of power industry, intelligent operation and maintenance handling of 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.