Diacs - definition
Diacs - definition
The Diacs is a symmetrical semiconductor element included in the group of non-linear bidirectional switches, mainly used in power control systems AC. Its structure is characterised by the absence of gate electrodes, which distinguishes it from the triacs with which it often works. It works on the switching principle - it conducts current only when a certain threshold voltage is reached in one of the polarisation directions, and then maintains conduction until the voltage drops below the holding value.
Diacs consist of a three-layer or five-layer semiconductor structure, allowing it to maintain symmetry with respect to the voltage applied to its electrodes. Thanks to this property, it maintains equal switching characteristics in both directions, making it particularly useful in AC circuits.
It is widely used as a triggering element for triacs in phase power control circuits such as lighting brightness controllers, motor speed controllers or heater temperature controllers. By delaying the moment the triac is switched on during each half-period of the supply voltage, the diacs allow modulation of the supplied energy, which translates into control of the rms value of the current.
Due to their simple design, high reliability and lack of need for active control, diacs are used in compact, energy-efficient and low-cost consumer electronics and Automation. Typical specifications of diacs include tripping voltages in the range of tens volts and the ability to conduct pulsed currents of several amperes (A).
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