Specifically what is a thyristor?

A thyristor is a high-power semiconductor device, also known as a silicon-controlled rectifier. Its structure includes four quantities of semiconductor components, including three PN junctions corresponding towards the Anode, Cathode, and control electrode Gate. These three poles are definitely 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 operating status. Therefore, thyristors are widely used in a variety of electronic circuits, like controllable rectification, AC voltage regulation, contactless electronic switches, inverters, and frequency alteration.

The graphical symbol of the semiconductor device is usually represented from the text symbol “V” or “VT” (in older standards, the letters “SCR”). In addition, derivatives of thyristors also include fast thyristors, bidirectional thyristors, reverse conduction thyristors, and light-controlled thyristors. The operating condition of the thyristor is the fact when 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 can be used between the anode and cathode (the anode is connected to the favorable pole of the power supply, and also the cathode is connected 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 will not light up. This implies that the thyristor will not be conducting and contains 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 (called a trigger, and also the applied voltage is called trigger voltage), the indicator light switches on. Which means that the transistor can control conduction.

3. Continuous conduction

As shown in Figure c above, following 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 implies that the thyristor can carry on and conduct. Currently, in order to shut down the conductive thyristor, the power supply Ea should 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 will not light up currently. This implies that the thyristor will not be conducting and may reverse blocking.

5. To sum up

1) If the thyristor is put through a reverse anode voltage, the thyristor is at a reverse blocking state whatever voltage the gate is put through.

2) If the thyristor is put through a forward anode voltage, the thyristor will only conduct when the gate is put through a forward voltage. Currently, the thyristor is within the forward conduction state, which is the thyristor characteristic, that is certainly, the controllable characteristic.

3) If the thyristor is turned on, so long as there is a specific forward anode voltage, the thyristor will stay turned on whatever the gate voltage. That is, following 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 seal to zero, the thyristor turns off.

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

Working principle of thyristor

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

1. If 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 turned off because BG1 has no base current. If a forward voltage is applied towards the control electrode currently, BG1 is triggered to produce 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 introduced 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 vital positive feedback, causing both BG1 and BG2 to get in a saturated conduction state quickly. A big current appears inside the emitters of the two transistors, that is certainly, the anode and cathode of the thyristor (how big the current is really based on how big the burden and how big Ea), so the thyristor is completely turned on. This conduction process is done in a very short period of time.
2. Right after the thyristor is turned 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 inside the conductive state. Therefore, the function of the control electrode is just to trigger the thyristor to transform on. Once the thyristor is turned on, the control electrode loses its function.
3. The best way to switch off the turned-on thyristor would be to lessen the anode current so that it is insufficient to keep up the positive feedback process. The best way to lessen the anode current would be to shut down the forward power supply Ea or reverse the link of Ea. The minimum anode current required to keep the thyristor inside the conducting state is called the holding current of the thyristor. Therefore, as it happens, so long as the anode current is under the holding current, the thyristor may be turned off.

What is the difference between a transistor and a thyristor?

Structure

Transistors usually include 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.

Operating conditions:

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

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

Application areas

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

Thyristors are mainly found in electronic circuits like 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 achieve current amplification.

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

Circuit parameters

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

To summarize, although transistors and thyristors can be utilized in similar applications sometimes, due to their different structures and operating principles, they have noticeable differences in performance and utilize occasions.

Application scope of thyristor

• In power electronic equipment, thyristors can be utilized in frequency converters, motor controllers, welding machines, power supplies, etc.
• Inside the lighting field, thyristors can be utilized 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 can be utilized in motor controllers.

Supplier

PDDN Photoelectron Technology Co., Ltd is an excellent thyristor supplier. It really is one of the leading enterprises in the Home Accessory & Solar Power System, which is 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 looking for high-quality thyristor, please feel free to contact us and send an inquiry.