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Thyristors - TRIACs

A TRIAC, or Triode for Alternating Current, is a type of thyristor, or a semiconductor device with three terminals. It is capable of controlling high voltages and currents. TRIACs are capable of controlling alternating current in either direction, whereas a regular thyristor switched on only when the gate current was of the same polarity as the anode current. The QK008RH4 is a specially designed TRIAC, with three terminals - Gate, Anode and Cathode.

Application Field

The QK008RH4 TRIAC is primarily used in light dimmers and electronic motor speed controllers. These applications usually require switching between AC mains voltage and low voltage control signals. The TRIAC allows the capacitive and inductive loads of the light dimmers and motor controllers to be connected without compromising safety, as the load current is limited to a maximum ratings.

Working Principle

The workings of the QK008RH4 TRIAC start with the gate voltage, which is usually supplied from an external source. The gate voltage then activates the TRIAC, which results in it allowing current to flow in both directions. When the anode has more charge than the cathode, the forward current flow is conducted through the TRIAC. When the cathode has more charge than the anode, the TRIAC is said to be in its reverse blocking state. In the blocking state, the TRIAC will not conduct, regardless of the gate voltage.

The QK008RH4 TRIAC works by regulating the voltage applied to its terminals. This is done by controlling the current flowing through the TRIAC, which is in turn regulated by the gate voltage. The gate voltage can be adjusted on AC mains voltage to regulate the level of current in the circuit and ultimately the output voltage.

In summary, the QK008RH4 TRIAC is used in dimmer and controller applications to regulate the level of voltage and current in the circuit, ensuring the output voltage is controlled and that all components remain safe. The TRIAC is activated by the gate voltage, which when applied, allows current to flow in both directions.

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