PIC12F675 Boost Converter
Category: Switch Mode Power Supplies (SMPS)
Designer: RANA MUHAMMAD ADNAN KHALIL
Notes
This circuit is simulated in Proteus 7.10. While code is written in MpLab X IDE using XC8 compiler. The microcontroller used in this project is PIC12F675. A boost converter is made by generating PWM through microcontroller. The working of this project is given below. 1. To understand the working of this circuit, first see previous circuit "PWM Generator With Duty Cycle Control". 2. In this circuit, a boost converter is made using PIC12F675. 3. The output voltage Vo formula for boost converter is Vo = Vin/(1-D) where D is duty cycle (0.1 to 0.9). 4. To derive the mosfet Q1 (IRF3205), a npn transistor Q2 (2N3904) is used, because Q1 should operate in saturation or cutt-off region. 5. The input voltage of boost converter is 12V, and output voltage is greater than 12V. 6. The resistor R1 is the load resistor, switching circuit should be operate with some load, otherwise the control is difficult. 7. The output voltage can be controlled by changing the duty cycle or mosfet Q1 through potentiometer RV1. 8. When the duty cycle is 50%, the output voltage will be exactly double of input voltage (use above equation for duty cycle and output voltage relation). 9. The frequency can also be changed by changing RV2. 10. The value of inductor is selected according to switching frequency, and it is inversely proportional. 11. The capacitors C1, C2, C3 and C5 are filter capacitors. 12. The LED D2 is used as indication of output voltages. 13. When the mosfet Q1 is ON, it connects the inductor L1 to ground, and inductor is charged and stores electrical energy in the form of current (i.e (1/2)*L*I^2). 14. When the mosfet Q1 is OFF, the inductor releases its energy, and inductor energy is added in input voltage, so the output voltage is greater than the input voltage. 15. The current direction can be seen using arrows. 16. The diode D1 is used to block the reverse voltages, because output voltage is greater than the input voltage. 17. To Calculate the values of output inductor and capacitor download the "FDAC Filter Design" app from google play store. Application: 1. This circuit can be used to understand the concept of a boost converter. 2. Thic circuit can be used as variable step-up or boost converter for DC input. Download these files to perform more experiments.