Qué es un DIAC | Qué es un TRIAC | Funcionamiento

Introduction to DIAC and its Symbol

This section introduces the DIAC (alternating current diode) as a semiconductor electronic component within the family of thyristors. It explains that the DIAC works as a bi-directional switch that can conduct in forward and reverse polarities above a certain voltage, known as the breakdown voltage. The symbol of the DIAC is also discussed.

Understanding the DIAC Symbol

• The DIAC is made up of two inverted diodes internally.

• Unlike ordinary diodes, it has more than two junctions of P and N material.

• The terminals are labeled A1 and A2 or MT1 and MT2 (Main Terminal).

• Being a bi-directional device, it can conduct current from A2 to A1 or vice versa.

Behavior of DIAC in a Circuit

This section explores how the DIAC behaves in a circuit using a small light bulb and a direct current source. It explains that below the breakdown voltage, the DIAC does not conduct but creates a voltage difference equal to that of the source. When the source voltage exceeds the breakdown voltage, the DIAC starts conducting.

Behavior in Circuit

• Below the breakdown voltage, no conduction occurs; instead, there is a voltage difference equal to that of the source.

• Once the source voltage reaches or exceeds the breakdown voltage, current starts flowing through both terminals.

• After conduction begins, most of the remaining voltage drops across the bulb while approximately 5V drops across the DIAC.

Application for Alternating Current

This section discusses how DIACs can be used for alternating current circuits. It demonstrates an example circuit with a transformer delivering a sinusoidal wave and shows how flickering occurs when crossing zero due to the DIAC's breakdown voltage.

Using DIAC for Alternating Current

• The DIAC conducts only when the voltage in the wave is greater than its breakdown voltage.

• In an alternating current circuit, the DIAC allows current to flow through the light bulb, causing it to flicker.

• The flickering effect is more noticeable with low-frequency waves but becomes imperceptible with higher-frequency electrical network waves.

Safety Precautions and Usage of DIAC

This section emphasizes the importance of caution when working with electricity and specifically circuits involving alternating current. It mentions that DIACs are not primarily power devices but are commonly used as activators for power elements like TRIACs.

Safety Precautions and Usage

• Electricity can be dangerous, especially when working with circuits involving alternating current.

• Caution is recommended when implementing circuits shown in the video.

• DIACs are not specifically power devices; they are often used as activators for power elements like TRIACs.

Voltage vs Current Graph of a DIAC

This section presents a graph illustrating the relationship between voltage and current in a DIAC. It explains that a certain breakdown voltage must be exceeded for the DIAC to conduct current.

Voltage vs Current Relationship

• The graph shows that a DIAC conducts current only after exceeding a specific breakdown voltage.

• The actual breakdown voltage depends on the component type specification.

Introduction to TRIAC and its Symbol

This section introduces the TRIAC (triode for alternating current) as a semiconductor electronic component within the family of thyristors. It explains that the TRIAC functions as a controlled bi-directional switch that can conduct in forward and reverse polarities. The terminals of gate or door, terminal 1, and terminal 2 are discussed.

Understanding the TRIAC Symbol

• The TRIAC has two inverted SCRs internally.

• It functions as a controlled bi-directional switch.

• The terminals are designated as gate or door, terminal 1, and terminal 2.

Behavior of TRIAC in a Circuit

This section explains how the TRIAC operates in a circuit using a light bulb. It describes how the TRIAC conducts current after receiving a trigger signal and turns off when the wave crosses zero. The angle of firing or activation determines the light intensity of the bulb.

Behavior in Circuit

• The TRIAC conducts current only after receiving a trigger signal at the gate terminal.

• Once triggered, it remains conducting until the wave crosses zero.

• Light intensity can be controlled by adjusting the angle of firing or activation of the TRIAC.

Dimmer Circuit with DIAC and TRIAC

This section presents an application example of a dimmer or intensity regulator circuit using both DIAC and TRIAC. It briefly explains each component's role in generating an activation pulse to control the light intensity of a bulb.

Dimmer Circuit Components

• The circuit includes components such as resistors, potentiometer, capacitor, DIAC, and TRIAC.

• The 10k resistor limits current and generates voltage drop for component protection.

• The potentiometer regulates voltage reaching the capacitor to charge or discharge it.

• The DIAC allows current flow when its breakdown voltage is reached by charging capacitor voltage.

• A 100 Ohm resistor acts as a current limiter for activating the TRIAC.

Timestamps have been associated with relevant sections to help navigate through specific parts of the video transcript.

Up to this point, we have already seen three types of thyristors, so let's look at some characteristics between them.

In this section, the speaker discusses the characteristics of different types of thyristors.

Characteristics of Thyristors

• Silicon Controlled Rectifier (SCR):

• Used for high-power applications.

• Can handle large currents and voltages.

• Once triggered, it remains conducting until the current drops below a certain threshold.

• Commonly used in power control circuits.

• Gate Turn-Off Thyristor (GTO):

• Similar to SCR but with an additional gate terminal.

• Can be turned off by applying a negative voltage to the gate terminal.

• Used in applications where fast switching is required.

• Triac:

• A bidirectional device that can conduct current in both directions.

• Used for AC power control applications.

• Can be triggered by either positive or negative voltage on its gate terminal.