Design Buck-Boost Converter Using ESP32 Module with Feedback Loop

A buck-boost converter is a switch-mode DC-DC converter that provides an output voltage greater than or less than the input voltage. The process of reducing the voltage then its input voltage is called Buck and where the output voltage is increased in terms of its input voltage then it is called as Boost. The arrangement of a buck-boost converter circuit is similar to that of the buck converter and boost converter circuits; it’s a combination of both buck and boost circuit.

Objective: To build a controller to switch between the Buck-Boost operations and control the output voltage by varying the Duty cycle by providing required PWM value from microcontroller.

Buck – Boost Converter Basic:

Buck Converter: Buck converter is a dc-to-dc converter designed to perform the step down conversion to perform the step down conversion of applied dc input.

Boost Converter: Boost converter performs the step up conversion of voltage from its input to load.

So as per the working of Buck and Boost Converter the Step down and Step-up of the voltage at the output depends on the Duty Cycle(square wave) applied to the switch (i.e. mosfet ) by varying PWM value.

For Buck Converter:

Vo = Vin * Duty Cycle 

For Boost Converter:

Vo =11-Duty Cycle*Vin

Hardware Requirements

• ESP32 Microcontroller
• Potentiometer 
• Inductors and Capacitors 
• MOSFETs
• Diodes
• Jumper Wires

Designing the Buck-Boost Converter With Feedback Circuit

In buck boost combination circuit when S1 is shorted, the circuit works as a boost converter providing the output voltage of 1/(1-D)*Vin and when S2 is shorted, the circuit works as a buck converter with an output voltage of D*Vin.

By adding feedback from the output and input terminals and giving it back to ESP32, we can make an automatic buck-boost converter circuit that automatically adjusts the output voltage which keeps it constant throughout the operation. In addition to the previous circuit, we have to use a voltage divider for input and output voltage sensing and to provide this data to the analog input pins of the ESP32.

Input voltage data goes to the ESP32 analog pin and the output voltage goes to another analog pin . Also, note that we use Schottky diodes to minimize diode losses; 1N5817 Schottky diodes are perfect for such applications.

Thus we have made an automatic buck-boost converter that automatically stabilizes the output voltage with the help of feedback-based input and output voltage sensing. Using ESP32.

Upload the Following Code After Building the Circuit in ESP32

#define vin_pin A1

#define output_voltage_sense A2

#define input_voltage_sense A0

#define boost_pin 5

#define buck_pin 6

int raw_vin="0," raw_vout="0," raw_iout="0;

float Vout_max="13.0," Iout_max="1.0," Vout_min="11.1," Iout_min="0.1,Vin_thresold=10.5;

float Iout_sense;

float Vout_sense;

float Vin_sense;

uint8_t duty_cycle = 25;

String mode="";

bool startup="true;

unsigned int count="0;

void setup() {

 // put your setup code here, to run once:

Serial.begin(115200);

 TCCR0B = TCCR0B & 0b11111000 | 0x01;

 analogWrite(buck_pin,255);

analogWrite(boost_pin,0);

}

void loop() {

 if(Serial.available()) {

 String data = Serial.readString();

 Vout_max = data.toInt();

 Vout_max = Vout_max/10;

 Serial.print("Vout_max= ");

 Serial.println(Vout_max);

 }

 for(int i="0;i"<10;i++) {

raw_iout += analogRead(input_voltage_sense)-513;

raw_vin += analogRead(vin_pin);

raw_vout += analogRead(output_voltage_sense);

 }

 raw_iout=raw_iout/10;

 raw_vout=raw_vout/10;

 raw_vin=raw_vin/10;

 Iout_sense=float(raw_iout)*0.0586;

 Vout_sense=float(raw_vout)*0.046;

 Vin_sense=float(raw_vin)*0.046;

if(count>100) {

Serial.print("Vin= ");Serial.println(Vin_sense);

Serial.print("Vout= ");Serial.println(Vout_sense);

Serial.print("Iout= ");Serial.println(Iout_sense);

Serial.print("Duty cycle=" ");Serial.println(duty_cycle);

Serial.print("Converter MODE : ");Serial.println(mode);

count=0;

}

if(startup==false) {

regulate(Iout_sense, Vin_sense, Vout_sense);

auto_cutoff(Iout_sense,Vin_sense, Vout_sense);

}

else {

 soft_start();

}

delay(600);

count++;

}

void regulate(float Iout, float Vin, float Vout) {

if(Vout_max<Vin) {

 mode="";

 mode="Buck mode";

 analogWrite(boost_pin,0);

 if((Iout<Iout_max && Iout>Iout_min) && (Vout<Vout_max)) {

 if(duty_cycle<250) {

 duty_cycle+=2;

 }

 analogWrite(buck_pin,255-duty_cycle);

 }

 else if((Iout>Iout_max) || (Vout>Vout_max)) {

 if(duty_cycle>2) {

 duty_cycle-=2;

 }

 analogWrite(buck_pin,255-duty_cycle);

 }

}

else if(Vout_max>Vin) {

 mode="";

 mode="Boost mode";

 analogWrite(buck_pin,0);

 if((Iout<Iout_max) && (Vout<Vout_max)) {

 if(duty_cycle<220) {

 duty_cycle+=2;

 }

 analogWrite(boost_pin,duty_cycle);

 }

 else if((Iout>Iout_max) || (Vout>Vout_max)) {

 if(duty_cycle>4) {

 duty_cycle-=2;

 }

 analogWrite(boost_pin,duty_cycle);

 }

}

}

void auto_cutoff(float Iout,float Vin, float Vout){

 if((Vout>=Vout_max) && (Iout<Iout_min) || (Vin<Vin_thresold)) {

 analogWrite(boost_pin,0);

 analogWrite(buck_pin,255);

 Serial.println("Charging Completed.");

 delay(64000);

 }

}

void soft_start() {

 if(Vout_sense<=Vout_min) {

 regulate(Iout_sense, Vin_sense, Vout_sense);

Serial.print("Vin= ");Serial.println(Vin_sense);

Serial.print("Vout= ");Serial.println(Vout_sense);

Serial.print("Iout= ");Serial.println(Iout_sense);

Serial.print("Duty cycle=" ");Serial.println(duty_cycle);

Serial.print("Converter MODE : ");Serial.println(mode);

Serial.println("Soft Start Activated");

 delay(64000);

 }

 else {

 startup=false;

 }

Thus, we Designed a Buck-Boost Converter with feedback loop using ESP32. There are various applications of this Buck-Boost converter such as It is used in the self regulating power supplies, It is used in the Battery power systems, Adaptive control applications, Power amplifier applications. 

If you are building a Buck-Boost converter and looking for electronic components such as ESP32 and other microcontroller by trusted brands such as Espressif, and other components reach out electronics components suppliers in India- Campus Component today!