Thyristors

Thyristors are core semiconductor devices in the field of power electronics, mainly used for switch control and power regulation in high-voltage and high-current scenarios.

 

1. What are Thyristors?

Structure: It is composed of four layers of PNPN semiconductor materials, including three PN junctions, with three electrodes: anode (A), cathode (K), and gate (G).

Conduction Condition: Both the positive anode voltage and gate trigger current must be met. After conduction, the gate loses its control function, and the current is determined by the external circuit.

Shutdown Condition: It must be turned off by the reverse anode voltage or the current drops below the holding current.

 

2. What are the Types and Packaging Forms of Thyristors?

1) Function Classification:

Ordinary Thyristor (SCR): unidirectional conduction, suitable for DC circuit control.

Bidirectional Thyristor (TRIAC): Bidirectional conduction, used for AC control.

 

Gate Turn-off Thyristor (GTO): Active shutdown is achieved through gate signals.

‌Light-controlled Thyristor‌: Triggered by light signals, often used in high-voltage isolation scenarios.

 

2) ‌Package Type‌:

‌Metal package‌ (bolt-shaped, flat-plate shape) is suitable for high-power devices and has excellent heat-dissipation performance.

 

‌Plastic package/ceramic package‌: mostly used for small and medium-power devices.

 

3. What are the Core Advantages of Thyristors?

‌High Withstand Voltage and High Current‌: The maximum reverse breakdown voltage can reach 6000V, and the operating current can reach 1000A.

‌Fast Switching Characteristics‌: The conduction time is only microseconds, suitable for high-frequency chopping circuits.

‌Strong Overload Capacity‌: It can withstand overvoltage and overcurrent for a short time, and has high stability.

 

4. What are Thyristors Used for?

1) ‌Industrial Control‌:

AC voltage regulation (such as electric furnace temperature control).

 

Motor drive and variable frequency speed regulation.

 

2) ‌Power System‌:

Rectification and inversion in high-voltage DC transmission.

 

3) ‌Consumer Electronics‌:

Lighting dimming, home appliance power regulation.

 

5. Differences from Other Devices

Compared to transistors, the thyristor’s “half-controllability” makes it impossible to actively shut down through the gate, but it has a higher power handling capacity; and compared with bidirectional thyristors (TRIACs), ordinary thyristors only support unidirectional conduction.