The masterpiece of a beautiful power engineer: CNC single chip pure sine inverter

　　I have been studying pure hardware inverters before, but this thing is getting more and more complicated, and the functions are not rich, so I came up with a method to implement SPWM with a single-chip microcomputer

　　The only microcontroller I had was the STC12C5410AD with PWM module, so I used it. Half a year ago, someone helped me select this small microcontroller with both PWM and AD. It is a rare gem for a small microcontroller inverter!

　　This microcontroller has a serial port download function. It does not require a dedicated programmer. You only need to use a RS232 level to TLL level converter (MAX232, which can be made by yourself, and the cost does not exceed 10 yuan) to connect the computer serial port and the microcontroller, which is convenient for friends to imitate.

　　The functions implemented this time are as follows:

　　1. SPWM wave output (two channels, two CD4011 with dead zone and reverse rear drive H bridge are required externally)

　　2. Closed-loop voltage regulation (DC feedback)

　　3. Output voltage detection (output voltage deviation is too large to alarm)

　　4. Output current detection (output current too large alarm)

　　5. Output short circuit protection (it is planned to adopt advanced tube voltage drop short circuit detection method. After detecting a short circuit, only a very narrow detection pulse is output in each power frequency cycle, and the output is restored immediately after the short circuit disappears)

　　6. Battery voltage detection (reminder and alarm for abnormal battery voltage or even shut down the inverter)

　　7.Serial communication function (convenient to connect to a computer to check the working status of the inverter)

　　8. External shutdown function (the MCU can be shut down using an external signal to improve expandability)

　　The program is written in C language, completely by myself! Now it is still lacking the improvement of serial communication function and the coefficients in the calculation formula of output current and voltage determined according to the hardware.

　　Other functions are valid in breadboard simulation test

　　Output SPWM wave

　　Assume the waveform when the load is short-circuited:

　　Test program on breadboard, the long line is the serial port

　　Now I have increased the SPWM frequency by 5 times to 20KHz, with 160 points per half cycle!

　　By the way, the startup bug and the protection circuit bug were fixed

　　The following waveform was tested on a breadboard using an RC filter (all the way in reverse):

　　The actual measured frequency is 23KHz. Here is a picture to prove it (a random cycle)

　　I stayed up until 2:30 last night and finally finished soldering the circuit using a universal board. The circuit diagram was just something I imagined during class...

　　This is the circuit diagram and the actual picture

　　The fourth last perfboard is used up, and the H-bridge of IRFP460 is being built:

　　Test desktop: