Q4025R5

Thyristors - TRIACs

A TRIAC (Triode for AC) is a type of thyristor that is a symmetrical three-terminal switch. It can be used to control the flow of current in an alternating current (AC) circuit. For example, it can be used to control the speed and power of AC motors and can also be used to prevent inverter overloading. The TRIAC is often referred to as a ‘four-quadrant switch’, because in a four-quadrant AC cycle, it can switch the current in both directions.

Q4025R5 Application Field and Working Principle

The Q4025R5 is a medium power static switching device with fast current turn-on and turn-off characteristics. It is suitable for use in AC power applications such as motor speed and current control, AC voltage regulation and fan speed control.

The Q4025R5 is a 20A, 25V TRIAC, which is the maximum trigger current it can withstand. It is made up of two PNPN thyristors, back-to-back connected. This configuration is known as a \'FRED\' (Flip-flop Relay Emulation Device). It has three pins, which are the gate, main terminal and auxiliary terminal. When the gate is triggered by an external device, such as a TRIAC driver IC, the current flows through it and is then transferred to the main terminal. This action will cause a voltage drop across the device, so the current output is proportional to the gate current.

During the on-state (t=0 to t=T) of the cycle, an external device (eg. TRIAC driver IC) will trigger the gate of the Q4025R5 TRIAC. The current passing through the device will then be switched on and will be conducted through the main terminal. The current will continue to flow as long as the external device is supplying it with current. At the off-state (t=T to t=2T), the external device will turn off the gate current, and the Q4025R5 will also turn off and thus allow no current to pass through the main terminal.

The main advantage of the Q4025R5 TRIAC is its ability to switch currents in both directions. This feature makes it ideal for controlling AC power applications such as motor speed and current control, AC voltage regulation and fan speed control. The Q4025R5 can also be used to prevent inverter overloading, as well as being used in household appliances and industrial controls.

Conclusion

The Q4025R5 is an efficient static switching device with fast current turn-on and turn-off characteristics. It is suitable for use in AC power applications such as motor speed and current control, AC voltage regulation and fan speed control. It is a symmetrical three-terminal switch that can switch the current in both directions and is ideal for preventing inverter overloading.