The DIAC is a full-wave or bi-directional semiconductor switch that may be activated in both forward and reverse polarity. The acronym DIAC stands for Diode Alternating Current, which is an abbreviation of the phrases Diode and Alternating Current. When employed in AC switches, the DIAC is commonly used to aid even TRIAC triggering. As a result, they’re frequently seen in light dimmers like those used in home lighting. These electrical components are also often utilized in fluorescent light starter circuits. Because of the symmetry of its characteristic function curve, DIACs are also known as symmetrical trigger diodes. The DIAC is a fixed-voltage trigger diode that is used with Triacs to simplify gate control circuits or as the first component in fluorescent bulb ballasts.
DIAC circuits conducts current only after a certain breakdown voltage exceeded. The exact breakdown voltage will be determined by the component type’s specifications. When the DIAC breaks down, the component’s resistance drops sharply, resulting in a significant reduction in the voltage drop across the DIAC and a commensurate rise in current. Until the current flowing through the DIAC falls below a particular value known as the holding current, the DIAC will remain in its favorable condition. The DIAC reverts to a high resistance, non-conducting state when the current falls below the holding current.
The breakdown voltage of most DIACs is about 30 volts, however the exact specs will vary depending on the kind of device. The DIAC is frequently made as a two-layer or five-layer structure. Switching happens inside the three-layer structure when the reverse biased junction encounters reverse breakdown.
- Lamp dimmer circuit
- Heat control
- Universal Motor speed control