CR2016 battery

　　ARM controlled inverter power supply circuit design scheme

　　The inverter uses the ARM controller as the control core. The feedback signals of the output voltage and current are processed by the feedback circuit and then enter the on-chip AD of the ARM processor. After AD conversion and digital PI operation, the corresponding SPWM pulse signal is generated and the SPWM is changed. The modulation ratio can change the output voltage, thus completing the closed-loop control of the entire inverter.

　　1. SPWM solution selection

　　1.1. PWM power chip solution

　　Use ordinary PWM power control chips, such as SG3525, TL494, KA7500, etc. The advantage of this type of chip is that it can directly generate pulse width modulation signals, but its disadvantage is that the waveform linearity is not good, and the oscillation generator relies on the charge and discharge circuit. To generate waveforms, when a PWM chip is required to generate an SPWM signal, a lot of additional circuits are required.

　　1.2. CPU software solution

　　Using CPU to generate SPWM pulses, such as microcontroller, ARM or DSP, etc. The advantage of this method is that the pulse width can be adjusted through software. Not only is the accuracy high, but the peripheral circuit is also simple and cheap.

　　In conclusion, STM32F107 (ARM) is selected to complete the generation of SPWM pulses and control of the entire inverter.

　　2. System hardware circuit design

　　2.1CPU controller

　　The CPU is the core part of the entire inverter and is mainly responsible for feedback signal collection, digital PI closed-loop calculation, PWM wave output, parameter setting and external communication. The CPU uses the latest STM32F107 series ARM chip launched by ST Company. This series of chips uses ARM's 32-bit CortexM3 as the core, with a maximum frequency of 72MHz. The Cortex core has a single-cycle hardware multiplication and division unit, so it is suitable for high-speed data processing. The chip has three independent conversion cycles, a minimum of 1μs high-speed analog-to-digital converter, and three independent digital-to-analog converters with independent sample and hold circuits, so it is particularly suitable for three-phase motor control, digital power supply and network applications. The chip also comes with a wealth of communication units, including 1 Ethernet interface, 5 asynchronous serial interfaces, 1 USB slave device, 1 CAN device, I2C and SPI modules.

　　2.2 Drive and inverter circuit

　　The main inverter circuit is shown in Figure 2 and uses a single-phase full-bridge inverter circuit based on H-bridge. The single-phase full-bridge inverter circuit is mainly composed of four MOSFETs Q1, Q2, Q3, and Q4. If a load is added between AC and OUT, an inverter circuit is formed. By controlling Q1, Q2, Q3, and Q4 to turn on and off in a certain order, the desired sine waveform can be obtained.

　　For this design, the selection of the switch tube is mainly based on its rated voltage and rated current. Here, an IRFP460N channel enhanced MOS tube with a rated voltage of 500V and a rated current of 20A is selected as the switching tube. Can meet design requirements. In order to limit the drive current of the MOSFET gate, a current-limiting resistor needs to be connected in series with the gate to prevent device damage caused by overcurrent.

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