2020 National College Student Electronic Design Competition Question B_UPS Power Supply_Provincial First Work

This open source is the work I made in the e-sports competition this year (2020). I am honored to win the provincial first prize in this year’s Sichuan competition area.

First, let’s analyze the topic;

It can be seen from this picture that our entire system has two power input terminals, one is 220V AC mains power, and the other is 24V DC power supply for energy storage components. We have an output, which is AC output.

According to the requirements, we know that we output 30V AC and need to do output feedback, power switching circuit, etc.

Our plan is: the front-stage 220V input first passes through the autotransformer and then passes through the isolation transformer to output the required 29V-43V AC input.

First stage: The AC input goes through an active rectifier ( I just have one of the LT4320 ) and outputs 40-60V DC.

Second stage: 40-60V DC power passes through a BUCK circuit and is stabilized to 25V. The BUCK here does not use a microcontroller, but uses a TL494 hardware square wave solution.

Level 3: Here we have the power switching circuit. We used two Nmos to make the power switching circuit, that is, when the 25V power supply is supplied, the battery power supply is disconnected. When 25V disappears, it switches to battery power supply, and the result is a non-inductive switching.

Level 4: We use the Boost circuit. We added voltage detection and current detection after Boost boost. Because this question requires closed looping of the output. Because the output AC voltage of the subsequent inverter circuit and the input DC are linear when the current is constant. Because the conversion from DC to AC mainly depends on the modulation degree of the SPWM of the main control. Therefore, we can achieve a closed loop by measuring a set of data, that is, the relationship between current and voltage. Of course, the measured current is a half-cosine transform. We can average the half cycle to get the output current.

Level 5: We use the H full-bridge inverter circuit.

Control level: We use the STM32F334 chip for control, which mainly controls the output of the Boost circuit, that is, the regulation of the PID, and the generation of the SPWM of the subsequent stage inverter. and current feedback control and voltage monitoring.

Display level: We use a 4.3-inch serial port screen for display. It can realize functions such as system status monitoring, PID adjustment and current compensation adjustment.

I haven’t finished writing it yet. I’m a bit busy right now. I’ll write it again later.