Design Of Variable Frequency Variable Voltage Power Supply Based On Microcontroller

Soft switching variable voltage variable frequency technology which realized by the combination of rectifier and inverter circuit is one of the most active research in today's power electronics field, it has a wide range of applications, including AC motor speed control and power supply etc. areas. Power supply has an extremely important position in any electronic equipment, however, the energy form they needed is different. Therefore, the research on variable voltage variable frequency power supply is of great theoretical and practical value.A VVVF power supply system based on microcontroller (PIC18F4431) is presented in this thesis. The input of the power supply is public grid's 220V50Hz AC, through rectifier and filter circuit transform into DC, then inverter to AC which amplitude ranged from 110V to 220V and frequency ranged from 40Hz to 70 Hz, then output to other device. A unipolar equal-area sinusoidal pulse width modulation and hybrid look-up table methods are used in this design to generate SPWM signal by software calculating, and real-time sampling the RMS of output voltage to form closed loop control system, so digital control of the VVVF is realized. The control signals amplified by floating channel bootstrap drive circuits, then provide gate drive to Power MOSFET, through turn-on and turn-off the switches, to realize inverter. Meanwhile, to ensure the safe and reliable operation, an output over-current, input under-voltage, over heating and other self protection function is also contained in the system. The design has simple structure, complete function, and meets the development trend of high frequency, modularization, digitization and greening, and has the characteristic of good waveform, small size, high efficiency, high precision, high reliability, wide input range and wide output frequency range, and has a good practical value.The structure and principle of the VVVF power supply is introduced firstly in this paper, and then around the main circuit module, drive and external module, control module, the details of the hardware and software design principle is discussed. Finally, the output parameters of the power supply such as waveform and efficiency were analyzed. The test results indicate that the design of VVVF power supply is feasible and the goal is basically achieved.