DIY Electronic Project: Building a Compact Power Supply with the TNY255GN
Introduction
The TNY255GN is a highly integrated, off-line switcher IC designed for use in low-power applications, including power supplies for consumer electronics, LED drivers, and battery chargers. It combines a high-voltage power MOSFET, a current sense resistor, and a control circuit in a single package, making it ideal for creating compact and efficient power supplies. In this DIY project, we will build a simple, low-power switch-mode power supply using the TNY255GN to convert an AC input voltage into a regulated DC output voltage. This project is perfect for hobbyists interested in power electronics.

Components Needed
TNY255GN Integrated Circuit
Transformer (TNY255GN compatible)
Diodes (1N4007 for rectification)
Capacitors (220µF, 100µF, and 0.1µF)
Resistors (various values for feedback and voltage setting)
Heat sink (for the TNY255GN)
Breadboard or PCB for assembly
AC power source (e.g., wall adapter or transformer)
Load (e.g., LED, small motor)
Multimeter (for testing)
Understanding the TNY255GN
The TNY255GN is part of the TinySwitch family, designed for low-power switch-mode power supply applications. It operates at a wide input voltage range (up to 265V AC) and provides a regulated output voltage with minimal external components. Key features include low standby power consumption, built-in thermal shutdown, and current limiting. Its compact size makes it suitable for applications where space is a premium.

Schematic Overview
Here’s a simplified schematic of the power supply circuit using the TNY255GN:

Circuit Connections
AC Input:

Connect the AC power source to a diode bridge rectifier to convert AC voltage into DC voltage. This is typically done using four diodes (1N4007) arranged in a bridge configuration.
Filtering:

Connect a filtering capacitor (220µF) after the diode bridge to smooth out the rectified voltage. This capacitor will help stabilize the DC voltage.
TNY255GN Connections:

Connect the filtered DC voltage to the VDD pin of the TNY255GN. This pin powers the chip and must be connected to the appropriate voltage range.
The TNY255GN also has an output pin that connects to a transformer. The transformer helps to step down the voltage to the desired level for your load.
Output Filtering:

Connect an output capacitor (100µF) after the transformer to further stabilize the output voltage. This capacitor ensures that the output remains steady even with varying load conditions.
Resistors and Feedback:

Use resistors to set the feedback voltage for the output regulation according to the TNY255GN datasheet. The feedback pin helps maintain a constant output voltage by adjusting the switching behavior of the IC.
Heat Sink:

Attach a heat sink to the TNY255GN if the application requires higher power levels to prevent overheating.
Testing the Circuit
Once you have assembled the circuit, connect it to an AC power source and measure the output voltage with a multimeter. Verify that the output voltage meets your specifications. Connect a load, such as an LED or small motor, to test the power supply under operational conditions.

Troubleshooting Tips
No Output Voltage: Ensure all connections are correct and that the AC input is functional. Check the diode bridge for correct orientation.
Output Voltage Too High/Low: Adjust the feedback resistors based on the specifications in the datasheet to achieve the desired output voltage.
Safety Precautions
When working with AC voltage, always take necessary safety precautions. Ensure the power supply is unplugged while assembling the circuit, and use insulated tools to avoid electric shock.

Conclusion
This DIY project illustrates how to create a compact power supply using the TNY255GN switch-mode power supply IC. By following these steps, you can gain valuable experience in power electronics and circuit design. Once you’re comfortable with this setup, consider expanding the project by adding features such as overvoltage protection, adjustable output voltage, or integrating a microcontroller for more advanced power management.
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