How to Design a Reliable Power Supply Circuit with LM338

Power supply design is a crucial step in almost every electronics project. If you are looking for a simple, adjustable and reliable voltage regulator, the LM338 is an excellent choice. The LM338 is known for its high current capacity and thermal protection, helping to create robust and efficient power supplies.

In this guide, we’ll show you the basics of designing power supply circuits using the LM338 and how to find quality LM338 ICs and components, so you can design power supply circuits with confidence.

What is LM338?

LM338 is a 3-cell adjustable voltage regulator. It provides an output voltage from 1.2 V to 32 V and an output current of up to 5 A.

It is an improved version of the LM317, ideal for high current applications such as battery chargers, solid state power supplies and motor controllers.

The LM338 controller and accessories are available from DRex Electronics.

Main features of the LM338

• ✅ Adjustable output voltage (1.2 V-32 V)
• ✅ Output current up to 5 A
• ✅ Built-in current limiting and thermal shutdown
• ✅ Overload protection
• ✅ Easy to use, only a few external components

LM338 main power supply circuit

🧰 Necessary components:

• LM338 integrated circuit
• 2 resistors (R1 and R2)
• Capacitors (input and output)
• Heat exchanger (important for large loads)
• Diode (additional protection)
• Transformer + bridge converter (for AC and DC conversion).

🔧 Circuit design steps:

1. AC current balancing coming up
   • Use the transformer to reduce the AC voltage.
   • Use a rectifier to convert AC voltage to DC voltage.
   • Add a large filter capacitor (e.g. 4700 µF) to balance the DC current.
2. Connect the LM338 voltage regulator
   • input pins to the balanced DC output.
   • The output pin produces a regulated voltage.
   • Thecontrol pins are connected to the voltage dividers (R1 and R2).
   • Use default values, e.g. R1 = 240 Ω, and adjust R2 to set the output voltage.
3. Setting the output voltage
   • Use the formula VOUT = 1,25 V x (1 + R1R2).
   • Add an output capacitor (usually 10 µF or more) to ensure stability.
4. Add thermal protection
   • Equip the LM338 with a heat sink. It may heat up under high load.
   • Add a fan if necessary.
5. Additional protection
   • Add a diode between output and input to protect against reverse current.
   • Add a diode between the control terminal and the output to protect against capacitor discharge.

Advantages of using LM338 in power supply design

• Higher amperage than LM317 or 7805.
• Adjustable output for flexible design
• Simple design with minimal components
• Ideal for regulated DC power supplies for stationary machines.
• Built-in protection for long term reliability

Applications for LM338 based power supplies

• 📱 Battery chargers
• Battery chargers DC desktop power supplies
• 💡 LED controllers
• 🛠️ DIY electronics projects
• 🚗 Automotive Circuits
• Industrial controllers and sensors

Buy LM338 and its components

At DRexElectronics you can find:

• LM338 original voltage regulators
• The original parts of the original original parts are availablefrom us.
• connectors, protection diodes and circuit board accessories
• transformer modules for a.c. inputs

We offer worldwide delivery, competitive pricing and support for OEMs, start-ups and hobbyists.

Tips for stability design

• To keep noise to a minimum, cables should be short and the layout compact.
• Use high quality electrolytic capacitors for inputs and outputs.
• Always use a suitable heat sink to withstand high loads.
• Use a multitrimming resistor in R2 to ensure accurate output voltage.

Conclusion

The LM338 is an efficient and flexible voltage regulator. It can be used to build stable and safe regulated power supplies with high amperes. The LM338 is a reliable choice whether you are powering a motor, charging a battery or creating a power supply for a laboratory bench.

🛒 Start building your LM338-based power supply today with quality components from DRex Electronics.