Detection method for bidirectional trigger diode transition voltage

A bidirectional trigger diode (also known as a bidirectional thyristor, bidirectional thyristor, or DIAC) is an electronic component that can conduct electricity in two directions. Unlike unidirectional trigger diodes (DIACs), bidirectional trigger diodes do not have an "anode" and a "cathode", but instead have two electrodes, commonly referred to as A1 and A2 or MT1 and MT2. Its characteristic is that it has similar electrical characteristics in both directions. Bidirectional trigger diodes are widely used in AC circuits as trigger components for control devices, such as dimmers, motor speed controllers, and electronic switches.

Working principle of bidirectional trigger diode

The operation of a bidirectional trigger diode depends on its V-I (voltage current) characteristics. Under normal circumstances, a bidirectional trigger diode exhibits a high impedance state in both directions, thereby preventing the flow of current. When the voltage between the electrodes increases to a certain degree (known as the transition voltage or trigger voltage), the bidirectional trigger diode will suddenly transition from a high resistance state to a low resistance state, allowing current to flow through. This transformation occurred very quickly, allowing bidirectional trigger diodes to be used as high-speed switches.

Detection method for bidirectional trigger diode transition voltage

The transition voltage of a bidirectional trigger diode is one of its important parameters, which usually requires precise measurement. Here are several common detection methods:

1. DC voltage testing method: Connect an adjustable DC power supply to both ends of a bidirectional trigger diode and connect a current detection instrument (such as a milliampere meter) in series. Gradually increase the output voltage of the power supply until a sudden increase in current is observed, at which point the voltage is the transition voltage. This method is simple and intuitive, but may not be suitable for bidirectional trigger diodes with very low transition voltages.

2. AC bridge method: The use of AC bridge method can provide more accurate measurements. In this method, bidirectional trigger diodes are placed in a specific bridge circuit to balance the bridge by adjusting other components of the bridge. When the bridge is balanced, the AC voltage passing through the bridge is the transition voltage of the bidirectional trigger diode. The advantage of this method is that it can measure the transition voltage under AC conditions, which is closer to the actual working conditions of bidirectional trigger diodes.

3. Oscilloscope method: Connect a bidirectional trigger diode to a circuit formed between a resistor and a power source, and use an oscilloscope to monitor the voltage across the bidirectional trigger diode. By gradually increasing the power supply voltage until the oscilloscope displays a voltage jump, the transition voltage can be determined. This method can visually observe the occurrence of transition voltage and can be used for dynamic testing.

4. Pulse testing method: Considering that bidirectional trigger diodes may be used under high-speed switching conditions, pulse testing method can provide a measurement method that simulates actual working conditions. By applying short pulse voltage to the bidirectional trigger diode and monitoring its response using devices such as oscilloscopes, the transition voltage can be determined. This method is particularly suitable for testing the dynamic characteristics of bidirectional trigger diodes.

summarize

Bidirectional trigger diode is an important electronic component widely used in various control and regulation circuits. Accurately measuring its transition voltage is crucial for ensuring the normal operation of the circuit. By using the above-mentioned common detection methods, the turning voltage of bidirectional trigger diodes can be effectively determined, providing accurate reference data for their application in practical circuits. Each method has its own applicable scenarios and advantages and disadvantages. In practical applications, the most suitable detection method should be selected based on specific needs and conditions.