If you’re an electronics hobbyist or a professional looking to create a compact power supply, building a 20V Switch Mode Power Supply (SMPS) is a rewarding project. SMPS designs are efficient and widely used in modern devices due to their small size and energy-saving features. In this guide, we’ll walk you through constructing a simple 20V SMPS using the TNY267PN IC, perfect for powering your DIY electronics. Let’s get started!
What is a Switch Mode Power Supply (SMPS)?
A Switch Mode Power Supply (SMPS) is an electronic power converter that efficiently converts electrical power using switching devices. Unlike linear power supplies, SMPS regulates output voltage by switching the input at high frequencies, making it ideal for applications requiring a stable 20V output from a 100-240V AC input. This project is both educational and practical for home or workshop use.
Analyzing the Circuit Diagram
The schematic above details a 20V SMPS circuit with the following components and their roles:
- TNY267PN (U1): A TinySwitch-II IC that handles switching and regulation.
- Transformer (T1): A 140T transformer with 34swg primary and 27T 24swg secondary windings.
- D1 (1N4007 Diode): Rectifies the AC input to DC.
- D2 (BA159 Diode): Protects the circuit from reverse voltage.
- ZD1 (18V Zener Diode): Regulates the output voltage.
- R1 (10R 1W Resistor): Limits inrush current.
- R2 (100Ω Resistor): Sets the feedback loop with ZD1.
- R3 (47Ω Resistor): Stabilizes the output.
- C1 (10µF 400V Capacitor): Filters the input DC.
- C2 (100nF 25V Capacitor): Smooths the output.
- PCB17: A bridge rectifier for AC to DC conversion.
Step-by-Step Guide to Building the 20V SMPS
Materials Needed
- TNY267PN IC
- 140T transformer (34swg primary, 27T 24swg secondary)
- 1N4007 diode
- BA159 diode
- 18V Zener diode
- Resistors: 10Ω (1W), 100Ω, 47Ω
- Capacitors: 10µF (400V), 100nF (25V)
- Bridge rectifier (PCB17)
- Heat sink (for the IC)
- Breadboard or PCB
- Soldering iron, solder, and flux
- Multimeter for testing
- 100-240V AC power source
Assembly Instructions
- Prepare the Input Stage: Connect the 100-240V AC input to the PCB17 bridge rectifier. Add C1 (10µF 400V) across the rectified DC output and R1 (10Ω 1W) in series with the positive line.
- Mount the TNY267PN: Place the TNY267PN IC on the PCB or breadboard. Connect pin 1 to the rectified DC, pin 2 to ground, pin 3 to the feedback network, and pin 4 to the transformer.
- Wire the Transformer: Attach the primary winding (34swg) to pin 4 of the TNY267PN and the secondary winding (24swg) to the output stage. Ensure proper insulation of the windings.
- Add the Diode and Capacitor: Connect D2 (BA159) across the transformer secondary. Link C2 (100nF 25V) across the output for smoothing.
- Set Up the Feedback: Wire R2 (100Ω) and ZD1 (18V Zener) in series from the output to pin 3 of the TNY267PN. Add R3 (47Ω) from pin 3 to ground.
- Final Connections: Ensure all ground points are common. Attach the output terminals for +20V.
- Test the Circuit: Apply 100-240V AC and use a multimeter to verify a stable 20V DC output. Adjust components if needed.
Safety Tips
- Work with AC power cautiously to avoid electric shock.
- Use a heat sink on the TNY267PN to prevent overheating.
- Double-check all high-voltage connections before powering on.
How It Works
The TNY267PN switches the input DC at high frequency, driving the transformer to step down the voltage. The secondary winding, rectified by D2 and filtered by C2, produces a 20V output. The Zener diode and resistor network provide feedback to regulate the voltage, ensuring stability across the input range.
Applications of a 20V SMPS
- DIY Electronics: Power LED strips or microcontrollers.
- Portable Devices: Charge batteries or run small appliances.
- Workshops: Provide a reliable bench power supply.
Troubleshooting Common Issues
- No Output: Check the transformer windings and IC connections.
- Unstable Voltage: Verify the Zener diode and capacitor values.
- Overheating: Ensure proper ventilation and a suitable heat sink.
Why Use TNY267PN?
The TNY267PN is a compact, efficient IC designed for SMPS applications, offering built-in protection and minimal external components. It’s perfect for beginners and experts alike.
Conclusion
Building a 20V SMPS with the TNY267PN is a great way to master switch-mode power supplies. Follow this guide to create your efficient power source for various projects. For more electronics tutorials, visit www.a2ahelp.com. Got questions? Leave a comment below!
