What exactly is a thyristor?

A thyristor is really a high-power semiconductor device, also called a silicon-controlled rectifier. Its structure consists of 4 quantities of semiconductor components, including 3 PN junctions corresponding towards the Anode, Cathode, and control electrode Gate. These 3 poles would be the critical parts from 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 commonly used in a variety of electronic circuits, like controllable rectification, AC voltage regulation, contactless electronic switches, inverters, and frequency alteration.

The graphical symbol of any silicon-controlled rectifier is normally 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 light-weight-controlled thyristors. The working condition from the thyristor is that each time a forward voltage is used, the gate needs to 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 linked to the favorable pole from the power supply, and also the cathode is connected to the negative pole from the power supply). But no forward voltage is used towards the control pole (i.e., K is disconnected), and also the indicator light fails to illuminate. 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 used 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, right after the thyristor is switched on, even if the voltage around 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 carry on and conduct. Currently, to be able to shut down the conductive thyristor, the power supply Ea must be shut down or reversed.

4. Reverse blocking

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

5. To sum up

1) When the thyristor is subjected to a reverse anode voltage, the thyristor is in a reverse blocking state no matter what voltage the gate is subjected to.

2) When the thyristor is subjected to a forward anode voltage, the thyristor is only going to conduct if the gate is subjected to a forward voltage. Currently, the thyristor is in the forward conduction state, the thyristor characteristic, that is certainly, the controllable characteristic.

3) When the thyristor is switched on, so long as there is a specific forward anode voltage, the thyristor will stay switched on whatever the gate voltage. That is, right after the thyristor is switched on, the gate will lose its function. The gate only serves as a trigger.

4) When 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 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 change off a conducting thyristor, the forward voltage between the anode and cathode must be shut down, or perhaps the voltage must be reversed.

Working principle of thyristor

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

1. When a forward voltage is used between the anode and cathode from the thyristor without applying a forward voltage towards the control electrode, although both BG1 and BG2 have forward voltage applied, the thyristor is still turned off because BG1 has no base current. When a forward voltage is used towards the control electrode at this time, BG1 is triggered to generate basics current Ig. BG1 amplifies this current, and a ß1Ig current is obtained in its 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 sent to BG1 for amplification then sent to BG2 for amplification again. Such repeated amplification forms a crucial positive feedback, causing both BG1 and BG2 to get into a saturated conduction state quickly. A big current appears in the emitters of these two transistors, that is certainly, the anode and cathode from the thyristor (the dimensions of the current is in fact based on the dimensions of the load and the dimensions of Ea), so the thyristor is completely switched on. This conduction process is completed in an exceedingly limited time.
2. Right after the thyristor is switched on, its conductive state will be maintained through the positive feedback effect from the tube itself. Whether or not the forward voltage from the control electrode disappears, it really is still in the conductive state. Therefore, the purpose of the control electrode is simply to trigger the thyristor to turn on. When the thyristor is switched on, the control electrode loses its function.
3. The only way to shut off the turned-on thyristor is to decrease the anode current so that it is inadequate to keep the positive feedback process. The best way to decrease the anode current is to shut down the forward power supply Ea or reverse the connection of Ea. The minimum anode current required to keep your thyristor in the conducting state is called the holding current from the thyristor. Therefore, strictly speaking, so long as the anode current is lower than the holding current, the thyristor could be turned off.

Exactly 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.

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 and a trigger current in the gate to turn on or off.

Application areas

Transistors are commonly used in amplification, switches, oscillators, along with other facets 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 accomplish current amplification.

The thyristor is switched on or off by managing the trigger voltage from the control electrode to realize 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 can be used in similar applications in some cases, because of the different structures and working principles, they may have noticeable differences in performance and utilize occasions.

Application scope of thyristor

• In power electronic equipment, thyristors can be used in frequency converters, motor controllers, welding machines, power supplies, etc.
• In the lighting field, thyristors can be used in dimmers and light-weight 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 can be used in motor controllers.

Supplier

PDDN Photoelectron Technology Co., Ltd is a wonderful thyristor supplier. It is one from the leading enterprises in the Home Accessory & Solar Power System, that is fully active in the growth and development of power industry, intelligent operation and maintenance handling of power plants, solar power and related solar products manufacturing.

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.