What is DIAC?
DIAC stands for Diode for Alternating Current. It is a type of two-terminal solid-state device that is used to trigger a thyristor or triac. DIAC is a type of bidirectional diode that can conduct current in both directions, making it suitable for AC circuits. It is a semiconductor device that is similar in construction to a diode, but unlike a diode, it is symmetrical and has low breakover voltage.
DIAC is a four-layer PNPN device that is made up of two back-to-back diodes connected in parallel. When a voltage is applied to the device, the current does not flow until a certain voltage, known as the breakover voltage, is reached. Once the voltage reaches the breakover voltage, the device switches on and conducts current in both directions without any external triggering.
How does DIAC work?
DIAC is a bidirectional device that can conduct current in both directions, making it suitable for use in AC circuits. The device is typically used as a triggering device for thyristors and triacs. When a voltage is applied to the device, it does not conduct until the voltage reaches a certain level known as the breakover voltage.
Once the voltage reaches the breakover voltage, the device switches on and conducts current in both directions. The breakover voltage is a function of the device’s design and the surrounding circuitry. DIACs can be used to trigger a thyristor or triac at a precise moment in the AC cycle, enabling precise control of the load current.
Uses of DIAC
DIACs are used in a variety of applications, including lamp dimming, motor speed control, and power supply regulation. They are also used in circuits that require precise AC triggering, such as in triac-based light dimming circuits, where a DIAC is used to trigger a triac to control the amount of light emitted by a lamp.
DIACs are also used in switch mode power supplies, where they are used to control the output voltage. In these circuits, a DIAC is connected in series with a capacitor, and the voltage across the capacitor is used to trigger a triac. The output voltage can then be regulated by varying the time at which the triac is triggered.
Example of DIAC circuit
One example of a DIAC circuit is a light dimmer circuit. In this circuit, a DIAC is connected in series with a potentiometer and a triac. The potentiometer is used to vary the voltage applied to the DIAC, which in turn varies the time at which the triac is triggered. The amount of light emitted by the lamp can then be varied by adjusting the potentiometer.
Another example of a DIAC circuit is a power supply regulator circuit. In this circuit, a DIAC is connected in series with a capacitor and a triac. The voltage across the capacitor is used to trigger the triac, which in turn controls the output voltage. The output voltage can then be regulated by varying the amount of time that the triac is triggered.
