How to design Arduino buck converter with feedback

Designing a buck converter with feedback control is a crucial skill in electronics, especially for projects requiring efficient voltage regulation. In this guide, we’ll explain how to create an Arduino-controlled buck converter, including the role of feedback and the components used. Whether you’re a beginner or an experienced hobbyist, this design will help you understand the interplay of hardware and software in power regulation.

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Why Use Feedback in Buck Converters?

Feedback is the cornerstone of stable voltage regulation. It ensures the output voltage remains consistent even when the input voltage or load changes. Arduino provides an excellent platform to implement feedback control systems due to its ease of programming and flexibility. If you're interested in advanced control techniques like adaptive control or fuzzy logic, these concepts can also be applied to refine your feedback loop further.

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Components You’ll Need

To build the buck converter, you will need the following components:

1. Arduino Board: Acts as the controller for the PWM signal.
2. TIP31C Transistor: Connects to Arduino's PWM pin to drive the MOSFET.
3. IRF4905 MOSFET: Handles the high current to the load.
4. SS34 Schottky Diode: Ensures fast switching and minimal power loss.
5. Inductor (100µH): Smoothens the current flow.
6. Capacitor (47µF): Filters out voltage ripples.
7. Resistor Network (15kΩ and 10kΩ): Creates a voltage divider for feedback.
8. 12V Battery and Bulb: Provides power and serves as the load.
9. Potentiometer (10kΩ): Adjusts the target voltage.

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Circuit Schematic

Below is the circuit diagram of the Arduino buck converter with feedback.

 

How It Works

Input and Feedback Mechanism

The potentiometer sets the desired output voltage, while the feedback pin reads the actual output voltage through a resistive voltage divider. This feedback mechanism enables the Arduino to adjust the PWM signal dynamically, ensuring the output voltage matches the target. You can explore the concept of feedforward control to enhance stability in more complex designs.

Role of Each Component

• SS34 Schottky Diode: With its low forward voltage drop, the SS34 improves efficiency and minimizes heat generation.
• Inductor and Capacitor: These work together to filter out noise and stabilize the output voltage.
• TIP31C and IRF4905: The TIP31C amplifies the Arduino's PWM signal to drive the IRF4905, a P-channel MOSFET that handles the high current load. To learn how you can use the TIP31C with Arduino see the TIP31C Transistor Guide for Arduino Projects and Arduino Speed Controller tutorials.
  

 For tips on designing the hardware side of a buck converter, you can refer to this detailed guide on designing buck converters.

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Software Implementation

The software is responsible for controlling the PWM signal based on the target and measured voltages. 

Below is the Arduino code for using Arduino as the feedback controller for the Buck Converter:

const int pwmPin = 9;          // PWM output to MOSFET
const int potPin = A0;         // Potentiometer pin for target voltage
const int feedbackPin = A1;    // Feedback voltage input
const int maxPWM = 255;        // Maximum PWM value
float maxPotVoltage = 5.0;     // Max potentiometer voltage (5V supply)
float maxFeedbackVoltage = 4.8; // Max feedback voltage due to the divider
float maxOutputVoltage = 12.0; // Max buck converter output voltage

void setup() {
  pinMode(pwmPin, OUTPUT);
  Serial.begin(9600);
}

void loop() {
  // Read the potentiometer value (0–5V) and map it to the target voltage range (0–12V)
  int potValue = analogRead(potPin); // Range 0–1023
  float targetVoltage = map(potValue, 0, 1023, 0, 12000) / 1000.0; // Map to 0–12V range

  // Read the feedback voltage (0–4.8V) and map it to the output voltage range (0–12V)
  int feedbackValue = analogRead(feedbackPin); // Range 0–1023
  float measuredVoltage = map(feedbackValue, 0, 1023, 0, 12000) / 1000.0; // Map to 0–12V range

  // Calculate the error
  float error = targetVoltage - measuredVoltage;

  // Calculate the PWM value (simple proportional control without constrain)
  int pwmValue = abs(error * 50); // Adjust 50 for control sensitivity

  // Output the PWM signal
  pwmValue = constrain(pwmValue, 0, maxPWM); // Constrain it to valid range
  analogWrite(pwmPin, pwmValue);

  // Debugging output
  Serial.print("Target Voltage: ");
  Serial.print(targetVoltage);
  Serial.print(" V, Measured Voltage: ");
  Serial.print(measuredVoltage);
  Serial.println(" V");
  Serial.print("PWM Value: ");
  Serial.println(pwmValue);
  Serial.print("Error: ");
  Serial.println(error);

  delay(100); // Delay for stability
}

1. pwmPin: Pin 9 is used to generate the PWM signal for driving the MOSFET.
2. potPin: Pin A0 reads the potentiometer value to set the target output voltage.
3. feedbackPin: Pin A1 reads the actual feedback voltage from the buck converter output.
4. maxPWM: The maximum value for the PWM duty cycle (8-bit resolution, 0–255).
5. maxPotVoltage and maxFeedbackVoltage: Maximum expected input voltage from the potentiometer and feedback divider.
6. maxOutputVoltage: The desired maximum buck converter output voltage (12V in this case).

• Configures pwmPin as an output to send PWM signals.
• Initializes serial communication for debugging.

1. Read Potentiometer Value:

   • The potentiometer value is read using analogRead(), which returns a value from 0 to 1023.
   • The map() function scales this range (0–5V) to the desired output voltage range (0–12V).

2. Read Feedback Voltage:

   • The actual output voltage is read from the feedback pin, which is scaled down using a voltage divider.
   • The map() function converts the range of the feedback voltage (0–4.8V) to the full output voltage range (0–12V).

3. Calculate the Error:

   • The error is the difference between the target voltage (set by the potentiometer) and the measured voltage (from feedback).

4. Calculate PWM Value:

   • The error is scaled by a constant (50), which determines the sensitivity of the control loop. A larger constant increases the response but may cause instability.
   • abs() ensures the PWM value is positive.
   • The constrain() function limits the PWM value to the valid range (0–255).

5. Output PWM Signal:

   • The PWM signal is sent to pwmPin using analogWrite().

6. Debugging Information:

   • Prints the target voltage, measured voltage, PWM value, and error to the serial monitor for real-time observation.

7. Delay:

   • A short delay (100 ms) adds stability to the loop by avoiding excessively frequent updates.

• Mapping and Scaling: Converts potentiometer and feedback readings into meaningful voltage ranges.
• Proportional Control: Adjusts the PWM value in proportion to the error. This is a basic control strategy.
• PWM Generation: Controls the duty cycle of the MOSFET gate to regulate the output voltage.

How It Works

• The potentiometer sets the desired output voltage.
• The feedback system continuously measures the actual output voltage.
• The control loop adjusts the PWM signal to minimize the error between the desired and actual voltages, ensuring stable output.

This structure is a foundation for implementing more sophisticated control techniques.

You can explore advanced control strategies like neural network control or optimal control for fine-tuning the output.

Testing and Troubleshooting

Once the circuit is assembled, upload the code and test it with a 12V battery and bulb as the load. Start by adjusting the potentiometer and observing the changes in the output voltage. If the output is unstable, revisiting the concepts of fuzzy logic control might help refine the feedback loop.

Video Demonstration

 The following video demonstrates how the Arduino buck converter with feedback circuit works to regulate output voltage. Using a TIP31C transistor, SS34 Schottky diode, and Arduino with a feedback loop, we show how the system adjusts the PWM signal to maintain the target voltage. This feedback-controlled system offers real-time adjustments, ensuring stable and accurate voltage regulation for various applications. Watch as we walk you through the setup, highlighting key components like the voltage divider and potentiometer, and explain how each part contributes to the overall functionality of the buck converter.

Applications and Future Enhancements

This buck converter design can be integrated into a wide range of projects, from robotics to automatic systems. To further enhance its capabilities, consider incorporating an automatic temperature adjustment system to protect the components under varying thermal conditions.

Conclusion

Building an Arduino-controlled buck converter with feedback is a rewarding project that combines hardware and software expertise. With components like the SS34 diode and TIP31C transistor, you can achieve efficient and stable voltage regulation. By integrating advanced techniques like adaptive control, this design can be scaled for more complex systems.

If you’re looking to delve deeper into control systems and their real-world applications, check out this adaptive control system tutorial.