Adjustable shunt regulator – TL431
The TL431 Circuit detailed guide is a smart shunt zener diode used for reference voltage control in power supply circuits. In this article, understand the working principle, function, and practical application of TL431 in SMPS in an easy and professional way. Also, how this IC controls a power supply and what its common issues are. All troubleshooting.
Working principle TL431
The TL431 circuit is a must-have for every advanced power supply because it provides a precision reference to the feedback of the power supply, which allows the supply to provide a very stable output voltage. This three-pin IC consists of anode, cathode, and reference pins.
TL431 simple schematic
In the image below, it can be seen that two resistors, R1 and R2, are connected to its reference pin. Their job is to keep a fixed voltage of 2.5 volts on the reference pin. If there is even a slight change in the value of these resistors, the output voltage of the power supply can change.
TL431 schematic diagram
In the picture below, you can see this IC configured as a reference with three resistors in a power supply. You can also see their value in the red marking. In some circuits, you may have 2 resistors, and in some circuits, 3 resistors in series or parallel. It depends on the circuit. The actual goal should be 2.5 volts on the reference pin.
Circuit malfunction
In case of circuit failure, you may find a change in the main output voltage of the power supply, or the output voltage may have a blinking fault. In such a situation, you should test the voltage divider resistance by disconnecting it from the circuit. If it is fine, then replace the IC.
Pin connection
Conclusion
In the article TL431 Circuit Detailed Guide, we have explained how this IC works, especially its reference function. This is the most important point of this IC. A technician who understands it can solve many power supply problems.
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Shaukat Ali has over 30 years of experience in LED TV repair, specializing in chip-level repair work. He is an expert in Sony LED TVs, and also repairs other major brands like Samsung, TCL, Orient, and Haier. His expertise includes display panel faults, motherboard issues, power supply circuits, T-Con, and HDMI faults. Based in Lahore, he shares real-time fault finding cases from daily repair work to help technicians and learners with practical experience.
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