Design Of Variable Frequency Variable Voltage Power Supply

Power Supply is very important for any electronic equipment.In many fields,the power used by electronic equipments is converted from public power grid in some methods instead of gotten from power grid directly.And the amplitude,frequency, stability and the controlling methods are different from one equipment to another,such as communication equipments power,UPS,medical power and so on,all of which are converted from public power according to a sequence including rectifying,filtering and inverting.The main study purpose of this thesis is to design a VFVV power supply,the main function of which is to output variable amplitude ranged from 110V to 220V and the variable frequency ranged from 40Hz to 70Hz according to public power grid.In order to reach to VFVV performance,this design utilizes MCU to produce PWM pulse.In order to producing the controlling signal,the carrier wave timer and the PWM pulse switch timer are set up With the calculated PWM pulse switching time in the timer interruption program.To ensure the voltage accuracy,this system makes use of feedback control strategy.According this strategy,the system samples voltage on the load,with the converting sequence,the sampling chip ADC0809 can get the DC voltage which ranged from 0V to 5V.With the sampled voltage data,the reference voltage value set previously and some algorithm,MCU controls the output signal,and we can get certain frequency and voltage AC finally.The main content of this paper includes two parts:hardware design and software design.(1) The hardware design is consisted of circuit schematic,PCB design and debugging all function modules which include main circuit,driver circuit,main board power supply,feedback circuit,keys board and display board.The core module of the system is the inverter circuit named H Bridge which is composed of 4 Power MOSFET droved by IR2110,and this driver chip IR2110 is controlled by MCU AT89C52.(2) The software is composed of control strategy design,function module design and testing the whole system performance.All the software system is based on MCU. According to the single-polar SPWM strategy,we can change the output voltage easily, and the Harmonic is also reduced effectively.