With the continuous advancement of electronic technology, the demand for high-performance semiconductor components in power control and protection devices is steadily increasing. SIDACs, a special type of switching thyristor, play a crucial role in the electronics industry due to their unique electrical characteristics and reliable performance. This article provides an overview of SIDACs, covering their definition, working principle, key features and advantages, as well as their applications.

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I. What is a SIDAC?

A SIDAC (Silicon Diode for Alternating Current) is a bidirectional triggering device made from five layers of semiconductor material, belonging to the thyristor family. Its structure allows it to conduct under voltage of either polarity, making it particularly suitable for AC circuits. The SIDAC has a relatively fixed triggering voltage; once this voltage is reached, the device quickly switches to its conducting state, creating a low-impedance path.

II. Working Principle

Internally, the SIDAC resembles a PNPN thyristor. When the applied voltage rises gradually to its specified breakdown voltage, avalanche breakdown occurs inside the device, causing a rapid increase in current and switching the SIDAC into conduction mode. During conduction, the voltage across the device drops quickly below the holding voltage, maintaining a low-impedance state. When the current falls below the holding current threshold, the SIDAC automatically switches off, returning to its high-impedance state. This process repeats during each positive and negative half-cycle of the AC signal, enabling bidirectional switching.

III. Features and Advantages

· Bidirectional conduction: Operates normally during both positive and negative half-cycles of AC without requiring external triggering signals. · High breakdown voltage: Suitable for high-voltage applications, ensuring safe and stable circuit operation. · Self-resetting capability: Automatically returns to its off-state after current interruption without needing external reset circuitry. · Fast response: Rapidly switches on once breakdown voltage is reached, ensuring timely activation of protection mechanisms. · Simple structure and low cost: Facilitates mass production and broad application.

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