So what is a thyristor?

A thyristor is actually a high-power semiconductor device, also known as a silicon-controlled rectifier. Its structure includes four levels of semiconductor materials, including 3 PN junctions corresponding to the Anode, Cathode, and control electrode Gate. These 3 poles would be the critical parts from the thyristor, allowing it to 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 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 also include fast thyristors, bidirectional thyristors, reverse conduction thyristors, and lightweight-controlled thyristors. The working condition from the thyristor is the fact 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 is used involving the anode and cathode (the anode is linked to the favorable pole from the power supply, and also the cathode is linked to the negative pole from the power supply). But no forward voltage is used to 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 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 used to the control electrode (known as a trigger, and also the applied voltage is referred to as trigger voltage), the indicator light turns on. Which means that the transistor can control conduction.

3. Continuous conduction

As shown in Figure c above, right after the thyristor is turned on, even if the voltage in the control electrode is removed (that is certainly, K is turned on again), the indicator light still glows. This implies that the thyristor can still conduct. Currently, in order to cut off the conductive thyristor, the power supply Ea has to be cut off or reversed.

4. Reverse blocking

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

5. To sum up

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

2) Once the thyristor is put through a forward anode voltage, the thyristor will only conduct once the gate is put through a forward voltage. Currently, the thyristor is in the forward conduction state, the thyristor characteristic, that is certainly, the controllable characteristic.

3) Once the thyristor is turned on, so long as you will find a specific forward anode voltage, the thyristor will remain turned on no matter the gate voltage. Which is, right after the thyristor is turned 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 disorder for your thyristor to conduct is the fact a forward voltage ought to be applied involving the anode and also the cathode, plus an appropriate forward voltage ought to be applied involving the gate and also the cathode. To transform off a conducting thyristor, the forward voltage involving the anode and cathode has to be cut off, or the voltage has to be reversed.

Working principle of thyristor

A thyristor is basically a distinctive triode made up of three PN junctions. It could be equivalently viewed as comprising a PNP transistor (BG2) plus an NPN transistor (BG1).

1. When a forward voltage is used involving the anode and cathode from the thyristor without applying a forward voltage to 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 used to the control electrode at this time, BG1 is triggered to generate a base 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 likely be brought in 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 large current appears inside the emitters of these two transistors, that is certainly, the anode and cathode from the thyristor (how big the current is really dependant on how big the burden and how big Ea), so the thyristor is entirely turned on. This conduction process is finished in a really short period of time.
2. Following the thyristor is turned on, its conductive state will likely be maintained through the positive feedback effect from the tube itself. Even if the forward voltage from the control electrode disappears, it is actually still inside the conductive state. Therefore, the purpose of the control electrode is simply to trigger the thyristor to change on. After the thyristor is turned on, the control electrode loses its function.
3. The only method to switch off the turned-on thyristor is to reduce the anode current that it is not enough to keep the positive feedback process. How you can reduce the anode current is to cut off 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 referred to as the holding current from the thyristor. Therefore, as it happens, so long as the anode current is lower than the holding current, the thyristor could be switched off.

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

Structure

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

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

Operating conditions:

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

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

Application areas

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

Thyristors are mainly utilized in electronic circuits including 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 turned on or off by controlling 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 usually have higher turn-off voltage and larger on-current.

To sum up, although transistors and thyristors can be utilized in similar applications sometimes, due to their different structures and working principles, they may have noticeable variations in performance and make use of occasions.

Application scope of thyristor

• In power electronic equipment, thyristors can be utilized in frequency converters, motor controllers, welding machines, power supplies, etc.
• Within the lighting field, thyristors can be utilized in dimmers and lightweight control devices.
• In induction cookers and electric water heaters, thyristors can be used to control the current flow to the heating element.
• In electric vehicles, transistors can be utilized in motor controllers.

Supplier

PDDN Photoelectron Technology Co., Ltd is a superb thyristor supplier. It really is one from 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 management of power plants, solar power panel 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. If you are searching for high-quality thyristor, please feel free to contact us and send an inquiry.