Components Required – 

Fig. 1: List of Components required for Open Loop Non – Isolated Inverting Buck- Boost Converter 

Block Diagram – 

Fig. 2: Block Diagram of Open Loop Inverting Buck-Boost Converter

Circuit Connections – 

1. DC source –

2. Oscillator and Switching Mechanism –

3. Energy Storage Element – 

4. Output Filtering Element –

5. Mode Selection –

How the circuit works – 

  

Testing the circuit – 

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//Program to

Code for Buck Converter with Input voltage = 12V and Adjustable and regulated Output voltage from 5V to 9V

This code will generate a PWM (Pulse Width Modulation)signal of 20kHz with 50% duty cycle

and can adjust the duty cycle as per the desired output voltage.

 */


#define TOP 799                          // Fosc = Fclk/(N*(1+TOP)); Fclk = 16MHz, Fosc = 20kHz

#define CMP_VALUE_HALF_DUTY 399          // 50% duty cycle

#define FeedbackPin A5                   // Adjustable pin of potentiometer at A5

#define Inputpin A4                     // feedback pin of Voltage Divider at A4

#define R1plusR2_resistor 2.5            // variable of R1+R2 value

#define R1_resistor 1.0                 // variable of R1 value

#define PWM 9                           // PWM(Pulse Width Modulation) wave at pin 9 


//// function declaration  

float Map_Feedback();                        // function to map feedback values

float Mapping_output_voltage();         //function to map potentiometer values


float Mapping_output_voltage(){                            // function definition 

 int Input_Read = analogRead(Inputpin);                     
//reading analog voltage from potentiometer and converting it to digital values in between 0 to 1023

 float Compare_voltage = (((Input_Read*(1.0)/1024)*4)+5);   
// mapping the digital value into analog voltage of 5V to 9V

 return(Compare_voltage);                                   // return the calculated output voltage

}


float Map_Feedback() {                                   // function definition                          

  int Digital_Read = analogRead(FeedbackPin);      
 // reading analog voltage form 0 to 5.2V and converting it to digital values in between 0 to 1023

  float ADC_READ = (Digital_Read/1024.0)*5.2;                           
// mapping the digital value into analog voltage of 0 to 5.2V

  float mapping_result = (ADC_READ*(R1plusR2_resistor/R1_resistor));     // calculating the actual output voltage 

  return(mapping_result);                                              // return the calculated output voltage

}


void setup() {

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

  pinMode(PWM,OUTPUT);                        // set 9 pin as output 

  pinMode(FeedbackPin,INPUT);                 // set A5 pin as input

  pinMode(Inputpin,INPUT);                 // set A4 pin as input         

  TCCR1A = 0;                                 //reset the register

  TCCR1B = 0;                                 //reset the register

  TCNT1 = 0;                                   //reset the register

  TCCR1A |= (1<<COM1A1);                        // set output at non inverting mode

  TCCR1A |= (1<<WGM11);                        // selecting Fast PWM mode

  ICR1 = TOP;                                   // setting frequency to 20KHz

  TCCR1B |= (1<< CS10)|(1<<WGM12)|(1<<WGM13);     //Timer Starts

  OCR1A = CMP_VALUE_HALF_DUTY;                  // setting PWM of 50% duty cycle

  delay(1000);                                  // delay for compensating the hardware transient time with software

}


void loop() {

  // put your main code here, to run repeatedly:

  float Compare_voltage_input = Mapping_output_voltage();   //read potentiometer value

  float actual_output_voltage = Map_Feedback();               // read feedback pin value       


  if(actual_output_voltage > Compare_voltage_input){   
//comparing actual output voltage with desired output voltage to find error in voltage

    OCR1A ++;                                           // if error is positive the duty cycle is increased but it is decreased for 

  }                                                    //P-MOSFET  as it is triggered by low voltage

  else if(actual_output_voltage < Compare_voltage_input){

    OCR1A --;                                             // if error is negative the duty cycle is increased

  }

}
###