We are Apogeeweb Semiconductor Electronic

WELCOME TO OUR BLOG

Home arrow Semiconductor Information arrow How to Reduce TRIAC Fault in Switching Circuits?

arrow left

arrow right

How to Reduce TRIAC Fault in Switching Circuits?

Author: Apogeeweb Date: 19 Jan 2021  796

triac application

Introduction

What is a triac? TRIAC (Triode for Alternating Current) is an electronic component that is widely used in alternating current power control. It is a three terminal electronic component that conducts current in either direction when triggered. TRIAC is able to switch high voltages and high levels of current, and over both parts of an AC waveform. This makes triac circuits ideal for use in a variety of applications where power switching is needed. You can find its applications in switching, phase control, chopper designs, brilliance control in lamps, speed control in fans, motors etc.

TRIAC Characteristics, TRIAC Structure and TRIAC Working

Catalog

Introduction

Ⅰ TRIAC vs Silicon Controlled Rectifiers (SCR)

Ⅱ TRIAC Structure and Symbol

Ⅲ How Do You Use a TRIAC

Ⅳ How Does a TRIAC Work?

4.1 TRIAC Leakage Current

4.2 Solutions


Ⅰ TRIAC vs Silicon Controlled Rectifiers (SCR)

Thyristor also called SCR stands for silicon controlled rectifier while TRIAC stands for triode for alternating current. The TRIAC has on and off state characteristics similar to SCR. The main difference between SCR and TRIAC is that thyristor is a unidirectional device while in TRIAC as a bidirectional device. A TRIAC is defined as a three terminal AC switch which is different from the other silicon controlled rectifiers (SCR) in the sense. They can turn and regulate both parts of the AC waveform easily. This makes this component appropriate for a variety of applications where control of AC power is needed. A dimmer circuit will be an example application, and we use it domestically as a ceiling fan regulator circuit. Also it can be used to regulate a motor or electric heater's input power. This is why TRIAC is used for applications of low to medium power, leaving SCR with high-power applications. While this is a very interesting system, a problem known as "leakage current" is present. And we'll talk more about this leakage current, its adverse effects, and some well-known ways to solve these problems in this article. But let's clear out the basics of TRIAC before that.

 

Ⅱ TRIAC Structure and Symbol

As for triac symbol, like any other electronic component, it consists of two SCRs linked in an antiparallel configuration, and if we look very closely at its symbol, it clearly reflects the TRIAC's bidirectional properties. Which you observe from the picture below.

triac symbol

The upgraded variant of the thyristor is the TRIAC. A thyristor can only control current in one direction, as you already know, but a TRIAC can control current in both negative and positive directions. TRIAC turns in each sine wave loop because of the existence of the sine wave, which means we can use the entire cycle, unlike SCRs. Like thyristor, a TRIAC has three terminals, but it becomes a little difficult to assign names to these terminals since they are related simply to the cathode and the anode of two SCRs. Two SCRs are also connected to the gate terminal, which is why it was called Anode 1 and Anode 2 or Main Terminal 1 and Main Terminal 2 (MT1 and MT2).
A multimeter can be used to test the health of a triac. First put the multimeter selector switch in a high resistance mode (100K), then connect the positive lead of multimeter to the MT1 terminal of triac and negative lead to the MT2 terminal of triac (there is no problem if you reverse the connection).

 

Ⅲ How Do You Use a TRIAC

Triacs are semiconductor devices that are widely used for switching medium power AC. Let's acquire a little knowledge of  TRIAC functions before going further. As the following figure shows you.

two-thyristor analogy

Two-thyristor Analogy

We have previously said that as a configuration of two SCRs, a TRIAC can be realized. The above image provides a little bit more clarity on the subject, but it is much more complex to work at the semiconductor level. A TRIAC can be activated in many ways, unlike SCR, regardless of the polarity of the terminals. Regardless of the polarity of the initiating pulse, it may also be activated. When working with TRIAC, one thing to remember is that when the MT2 and gate current are at the same polarity, the sensitivity of the trigger current is much greater. We can now move on to cleaning out our key issue of leakage current with the simple cleared out.

Triac Switching Circuit Example

Ⅳ How Does a TRIAC Work?

4.1 TRIAC Leakage Current

There is structural leakage current in the off state of thyristor, TRIAC, or any other solid-state AC switches, which is why a small amount of current flows through the load, this circuit is sufficient in some cases to charge a load circuit (Inductive) and causes it to flash spontaneously. We need to take careful care of the specifics and design the circuit accordingly to avoid this, and we will talk more about it in this section of this article.
If the voltage of MT2 reaches a certain rated threshold voltage (which can occur due to the transient state of high voltage), the leakage current between the two terminals may enter the point at which the TRIAC breaks into conduction mode. In this state, a sudden localized heat will be produced when a sudden increase in current flows through the TRIAC, so that the TRIAC can be destroyed. Incandescent lamps are most likely the source of strong inrush currents, with capacitive loads.

triac

4.2 Solutions

By applying one or more of the following methods, this condition can be avoided:
1) Maximum Temperature Ratings Tj max. ensure that the temperature is not surpassed. As temperature rises, the current of leakage through the system increases, we can eliminate/reduce this issue by integrating specific TRIAC brands for specific requirements.
2) By placing a broad value resistor from the gate to the cathode, we can reduce the TRIAC's sensitivity. This decreases the gate current, thereby reducing the current of leakage. It, on the other hand, increases the TRIAC turn-on time.
3) If it is not possible to implement the methods described above, we can use a TRIAC with a less sensitive gate during the off time and apply a small degree of reverse bias to the gate. In this process, we have to minimize the dissipation of power through the gate.
4) Depending on the form of load, another strategy for reducing leakage current is to fully eliminate the snubber circuit. The capacitor leakage also becomes the main source of leakage current, so we can decrease the current flow through the snubber and decrease the leakage current by removing the snubber network.
If you want to know more TRIAC info, you can check its Triac I-V Characteristics curves with more examples. Before try these methods to reduce current leakage, please remember safety first!

 

Frequently Asked Questions about TRIAC Basic and Its Applications

1. What is a triac used for?
The Triac is most commonly used semiconductor device for switching and power control of AC systems as the triac can be switched “ON” by either a positive or negative Gate pulse, regardless of the polarity of the AC supply at that time.

 

2. Which is an example of Triac?
TRIAC Applications
TRIAC is very commonly used in places where AC power has to be controlled for example, it is used in the speed regulators of ceiling fans, AC bulb dimmer circuits etc. Let us look into a simple TRIAC switching circuit to understand how it works practically.

 

3. What is triac and its characteristics?
A Triac is defined as a three terminal AC switch which is different from the other silicon controlled rectifiers in the sense that it can conduct in both the directions that is whether the applied gate signal is positive or negative, it will conduct. Thus, this device can be used for AC systems as a switch.

 

4. What is a triac switch?
A Triac is a high-speed solid-state device that can switch and control AC power in both directions of a sinusoidal waveform. Being a solid state device, thyristors can be used to control lamps, motors, or heaters etc.

 

5. What is the working principle of Triac?
The triac is another three-terminal ac switch that is triggered into conduction when a low-energy signal is applied to its gate terminal. Unlike the SCR, the triac conducts in either direction when turned on.

Ordering & Quality

Photo Mfr. Part # Company Description Package PDF Qty Pricing
(USD)
10A07-T 10A07-T Company:Diodes Incorporated Remark:Rectifiers 10A 1000V Package:N/A
N/A
In Stock:On Order
Inquiry
Price:
1+: $0.79000
10+: $0.65100
100+: $0.42000
500+: $0.42000
1000+: $0.33600
Inquiry
STP80NF55-08 STP80NF55-08 Company:STMicroelectronics Remark:MOSFET N-Ch 55 Volt 80 Amp Package:N/A
N/A
In Stock:On Order
Inquiry
Price:
1+: $2.35000
10+: $1.99000
100+: $1.55000
250+: $1.50000
500+: $1.31000
1000+: $1.12000
2000+: $1.09000
5000+: $1.02000
10000+: $0.98000
Inquiry
STW88N65M5 STW88N65M5 Company:STMicroelectronics Remark:MOSFET N-Ch 650V 0.024 Ohm 84A MDMesh M5 Package:N/A
N/A
In Stock:On Order
Inquiry
Price:
1+: $13.30000
10+: $12.22000
25+: $11.71000
100+: $10.13000
250+: $9.81000
500+: $9.18000
1000+: $8.42000
Inquiry
SPP20N60S5 SPP20N60S5 Company:Infineon Technologies Remark:MOSFET N-Ch 600V 20A TO220-3 CoolMOS S5 Package:N/A
N/A
In Stock:On Order
Inquiry
Price:
1+: $5.06000
10+: $4.30000
100+: $3.44000
500+: $3.06000
1000+: $2.88000
2500+: $2.79000
Inquiry
STW4N150 STW4N150 Company:STMicroelectronics Remark:MOSFET N-channel 1500 V PowerMesh Package:N/A
N/A
In Stock:On Order
Inquiry
Price:
1+: $6.62000
10+: $5.70000
100+: $4.73000
250+: $4.45000
500+: $4.17000
1000+: $3.75000
2500+: $3.61000
Inquiry
NRVBS3200T3G Company:ON Semiconductor Remark:Schottky Diodes & Rectifiers 3A, 200V SCHOTTKY RECT. Package:N/A
N/A
In Stock:On Order
Inquiry
Price:
1+: $1.08000
10+: $0.92300
100+: $0.69200
250+: $0.67200
500+: $0.58700
1000+: $0.47800
2500+: $0.46400
5000+: $0.42800
10000+: $0.40900
Inquiry
MMSZ4699T1G MMSZ4699T1G Company:ON Semiconductor Remark:Zener Diodes 12V 500mW Package:N/A
N/A
In Stock:On Order
Inquiry
Price:
1+: $0.21000
10+: $0.18300
100+: $0.06300
1000+: $0.04400
3000+: $0.03400
9000+: $0.02900
24000+: $0.02700
45000+: $0.02300
99000+: $0.02100
Inquiry
6A10-T Company:Diodes Incorporated Remark:Rectifiers 1000V 6A Package:N/A
N/A
In Stock:On Order
Inquiry
Price:
1+: $0.42000
10+: $0.34300
100+: $0.21000
500+: $0.21000
1000+: $0.16200
2500+: $0.13800
Inquiry

Related Articles

2018 Semiconductor Market Forecast --The Semiconductor Market is Going through a Big Shuffle

Apogeeweb 12 Mar 2018  3040

 Warm hints: The word in this article is about 2800 words and  reading time is about 13 minutes. SummaryThis paper is mainly about the semiconductor market forecast in 2018.Actually, the se...

Continue reading »

Design scheme of intelligent energy saving plugs based on AVR

Apogeeweb 5 Jan 2018  2232

Warm hints: The word in this article is about 2800 and  reading time is about 15 minutes. SummaryThe standby energy consumption of computer external equipment (such as printer, scanner, ste...

Continue reading »

​From Sand to Chip - Chip Formation Process

Apogeeweb 3 Apr 2018  2565

Warm hints: The word in this article is about 4500 words and reading time is about 25 minutes SummaryThis paper mainly explain the process of chip formation.How did sand become a chip? Before beginni...

Continue reading »

Two Major Types of IC Packages Analyses

Apogeeweb 18 Jan 2021  495

IntroductionIC packaging refers to the material that contains a semiconductor device. The package is a case that surrounds the circuit material to protect it from corrosion or physical damage and allo...

Continue reading »

How to Identify Pulse Circuit Diagram

Apogeeweb 29 Jan 2018  7801

SummaryThere are a wide range of electrical pulse shape, sch as a rectangular, triangular, zigzag, bell, staircase and spire-shaped, the most representative of which is the rectangular pulse. Pulse ci...

Continue reading »

Iris Recognition Technology:Principle and Application

Apogeeweb 5 Nov 2018  2498

Warm hints: The word in this article is about 3000 words and reading time is about 15 minutes. SummaryBiometric recognition is the most convenient and safe identification technology at present. It do...

Continue reading »

pinglun 0 comment

Leave a Reply

Your email address will not be published.

 
 
   
 
code image
Rating: poor fair good very good excellent

# 0 1 2 3 4 5 6 7 8 9 A B C D E F G H I J K L M N O P Q R S T U V W X Y Z