PIC12F675 Flyback 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 flyback 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". New circuits are added daily. Comeback daily to get new amazing circuits. 2. In this circuit, a flyback converter is made using PIC12F675 (it is used just to generate PWM, if you have some other source of PWM then you can use that source). 3. The output voltage Vo formula for flyback converter is Vo = Vin*Ns*D/(Np*(1-D)) where D is duty cycle (0.1 to 0.45). 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. This circuit is design to step down 12Vdc to 5Vdc input voltage of flyback converter is 12V, and output voltage is less than 12V (that is around 5V as shown in animation). 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 of mosfet Q1 through potentiometer RV1. 8. It is recommended that the duty cycle should be less than 50%. 9. The frequency can also be changed by changing RV2. 10. The value of transformer inductance 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 transformer primary inductor to ground, and inductor is charged and stores electrical energy. 14. When the mosfet Q1 is OFF, the inductor (primary side of transformer) releases its energy, and inductor energy transferred to output voltage, so the D1 conducts when the Q1 is OFF. 15. The current direction can be seen using arrows. 16. The diode D1 is used to block the reverse voltages, when Q1 is ON the diode D1 is reverese biased. Application: 1. This circuit can be used to understand the concept of a flyback converter. 2. This circuit can be used as variable flyback converter for DC input upto 100W. Download these files to perform more experiments. Come back daily to get new amazing circuits.