Two-way thyristor working principle

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Introduction: This article details the working principle of two-way thyristor , and some interesting knowledge about its English name. Radisson and folks are rushing to make up for it~~

First, the working principle of two-way thyristor - - Introduction

Bidirectional thyristor (TRIAC) is a three-terminal thyristor switch with unidirectional conductivity. It is an ideal AC switching device based on common thyristor (SCR) with only one trigger. The device can replace two thyristors with reverse polarity in parallel.

Second, the working principle of two -way thyristor - - structure

The two-way thyristor is a three-terminal component as shown in the following figure. The three terminals are T1, T2 and G, respectively. T1 (second terminal) and T2 (first terminal) are collectively referred to as main terminal, and G is a control pole. When the voltages of the control electrode G and the first terminal T2 with respect to the second terminal T1 are both positive values, T2 acts as an anode and T1 is a cathode; conversely, when the control electrode G and the first terminal T2 are opposite to the second terminal T1 When the voltage is negative, T1 acts as the anode and T2 acts as the cathode.

As long as the control thyristor enters the signal, T1 and T2 can be turned on regardless of the forward or reverse voltage. Otherwise, if there is no trigger signal at the control pole, T1 and T2 are in the off state.

Third, the working principle of two-way thyristor

When the anode is applied with a forward voltage, the BG1 and BG2 tubes are in an amplified state. At this time, the forward trigger signal is input from the G terminal of the triac of the triac, so that the base current ib2 of the BG2 tube passes, and the amplification is performed by the BG2 tube. After that, its collector current is ic2=β2ib2. While ic2 flows along the circuit to the base of BG1, there is ib1=ic2, and the current is amplified by the BG1 tube, and the collector current of BG1 is ic1=β1ib1=β1β2ib2. This current flows back to the base of BG2, causing the base current ib2 of BG2 to increase, resulting in a positive feedback that causes the current to plummet, causing the thyristor to saturate and conduct. Since positive feedback is formed in the circuit, the thyristor cannot be turned off after being turned on, and even if the current at the G terminal of the control electrode disappears, the thyristor can maintain the conduction state.

The thyristor has only two states of conduction and shutdown, and has switching characteristics, but there are certain preconditions for the realization of such switching characteristics. When the anode potential is always higher than the cathode potential, and there is sufficient forward voltage and current at the G terminal of the control electrode, the thyristor can be converted from the off state to the on state; when the anode potential is always higher than the cathode potential, and the anode When the current is greater than the holding current, the conduction state of the thyristor can be maintained; when the anode potential is lower than the cathode potential, or the anode current is lower than the holding current, the conduction state of the thyristor can be changed to the off state.

Extended reading:

Two-way thyristor English name

The English name of the two-way thyristor is TRIAC, which is translated as a three-terminal thyristor switch. Since the three-terminal TRIode and the AC semiconductor switch are ACsemiconductorswitch, there is a short name of “TRIAC”. However, the abbreviation of the two-way thyristor is not the same for each company. Let's take a closer look at the "English alias" of the two-way thyristor.

BCR: bidirectional Bi-directional, control Controlled, rectifier Rectifier, so it can be translated as bidirectional control rectifier, ie bidirectional thyristor. At present, the typical manufacturer of bidirectional thyristors named by BCR is Mitsubishi of Japan. The bidirectional thyristors produced by them include BCR1AM-12, BCR8KM, BCR08AM and so on.

BT: Bidirectional bi-directional, three-terminal Triode, which reflects the characteristics of two-way thyristor. At present, many companies use "BT" to name the two-way thyristor product model, such as ST, Netherlands Philips-Philips, etc. The two-way thyristor has BT131-600D, BT134-600E, BT136-600E, BT138-600E, BT139-600E and so on.

The following is an article about the working principle of two-way thyristor recommended by Xiaobian. Come and poke up.~~~

1. Working principle and schematic diagram of two-way thyristor

2. Design and application analysis of two-way thyristor

3. Principle and application of two-way thyristor structure

4, the characteristics and use of two-way thyristor

Thyristor