What is a bidirectional thyristor

Bidirectional Thyristor, also known as BTR or Bi SCR, is a type of thyristor device that can conduct in two directions. It combines bidirectional conductivity with the controllability of SN65LV1023ADBR thyristor, enabling bidirectional control and conduction.

1、 Basic structure:

The basic structure of a bidirectional thyristor is similar to that of a regular thyristor, consisting of four layered semiconductor materials - P-type and N-type, arranged alternately. The structure of a bidirectional thyristor includes two PN junctions, one of which is the control junction and the other is the main junction. The control junction consists of a trigger electrode and a control electrode, while the main junction consists of a main electrode. The trigger electrode and control electrode are respectively used to control the switching action of the bidirectional thyristor.

2、 Advantages and disadvantages:

The advantages of bidirectional thyristors include:

1. Can conduct in two directions, achieving bidirectional control and bidirectional conduction;

2. Capable of withstanding high current, high voltage, and high temperature, suitable for high-power applications;

3. Can achieve fast switching and response time;

4. Small size, light weight, and high reliability.

The disadvantages of bidirectional thyristors include:

1. External circuits are required to provide control signals, and the control circuit is complex;

2. Nonlinear characteristics lead to waveform distortion;

3. The conduction voltage drop is high, resulting in significant power loss.

3、 Working principle:

The working principle of bidirectional thyristors is similar to that of ordinary thyristors. When a positive pulse signal is applied to the control electrode, the PN junction of the control junction will be broken down, forming a conductive channel. This leads to the breakdown of the PN junction of the main electrode, forming a bidirectional conductive channel that allows current to flow from the main electrode to the other main electrode. When the signal from the control electrode disappears, the bidirectional thyristor will remain conductive until the current drops to zero or until a reverse voltage is applied.

4、 Application:

Bidirectional thyristors are widely used in the fields of power control and power regulation, especially in AC circuits. Here are some common applications:

1. Voltage and current control of AC power supply.

2. Speed regulation and reverse control of electric motors.

3. Switching control of communication circuits.

4. Inverters and frequency converters in power systems.

5. Current control in power transmission and distribution systems.

5、 Inspection method:

When we need to check whether the bidirectional thyristor is working properly, the following methods can be used:

1. Resistance measurement method: Use a multimeter to measure the forward and reverse resistance of a bidirectional thyristor. Under normal circumstances, the forward resistance should be very small, close to a short circuit state; And the reverse resistance should be very large, close to an open circuit state. If the forward resistance is too high or the reverse resistance is too low, it indicates that the bidirectional thyristor may be damaged.

2. Voltage measurement method: Use a digital voltmeter or oscilloscope to measure the forward and reverse voltages of a bidirectional thyristor. Under normal circumstances, forward voltage should be able to conduct, while reverse voltage should be blocked. If the forward voltage cannot conduct or the reverse voltage cannot be blocked, it indicates that the bidirectional thyristor may be damaged.

3. Trigger current measurement method: Use a digital ammeter or oscilloscope to measure the trigger current of a bidirectional thyristor. Under normal circumstances, when the triggering current reaches a certain value, the bidirectional thyristor should conduct. If the triggering current cannot conduct, it indicates that the bidirectional thyristor may be damaged.

6、 Category:

Bidirectional thyristors can be divided into voltage control type, current control type, and hybrid control type according to their control methods; Divided into homopolar structure and heteropolar structure according to structural mode.

7、 Installation points:

When installing bidirectional thyristors, the following points should be noted:

1. Determine the polarity of a bidirectional thyristor: A bidirectional thyristor has two main polarities, anode and cathode. The anode is usually marked as A, and the cathode is usually marked as K. Before installation, carefully check the markings on the bidirectional thyristor to ensure proper connection.

2. Use a suitable heat sink: Bidirectional thyristors generate significant heat during operation, so a heat sink is needed to dissipate heat. The radiator should be selected with appropriate size and material to ensure that the bidirectional thyristor can effectively dissipate heat and prevent overheating damage.

3. Pay attention to insulation and insulation pads: The installation position of bidirectional thyristors must maintain insulation to prevent current leakage and short circuits. Insulation gaskets and insulation adhesive pads should be used during installation to isolate bidirectional thyristors and other metal components.

4. Connect the correct power source: Bidirectional thyristors typically require an external power source to control conduction and cutoff. When installing, make sure to connect the positive and negative poles correctly to avoid causing current backflow or short circuit.

5. Pay attention to current and voltage limitations: When installing bidirectional thyristors, ensure that the current and voltage are within the specified range. Exceeding the rated current and voltage of the bidirectional thyristor may result in component damage.

6. Regular inspection: After installation, the working status and heat dissipation of the bidirectional thyristor should be checked regularly. If any abnormalities are found, they should be repaired or replaced in a timely manner.

8、 Development history:

The development history of bidirectional thyristors can be traced back to the 1960s. The earliest bidirectional thyristor device was the Bilateral Triode Thyristor (BTT), invented by researchers at Bell Laboratories in the United States. Later, bidirectional thyristors (SCR) were developed and became the most commonly used bidirectional thyristor devices.

With the continuous development of technology, bidirectional triggered thyristors (GTOs) and bidirectional conducting thyristors (BRTs) have emerged one after another. Bidirectional triggered thyristors have higher triggering sensitivity and faster turn off speed, making them suitable for high-frequency AC circuits. The bidirectional conducting thyristor has a simpler structure and lower cost, making it suitable for some low-frequency applications. With the advancement of technology, the structure of bidirectional thyristors has been improved and optimized, and their performance has been enhanced.