CNC power supply produced by sHMIctrl smart screen

The DP28 CNC power supply is a continuation of the design ideas of the DP50 CNC power supply, and is a CNC power supply example produced with the shmictrl smart screen. Although this CNC power supply is positioned in the DIY market, the screen source code and the source code of stm32f072 are all developed, which means that this solution is used The screen end and control end (stm32 implementation), combined with various back-end implementations, can fully achieve the purpose of rapid development of various commercial power supplies;

performance

• Small CNC power supply in DC-DC mode
• Input voltage 9 ~ 24V, output 6 ~ 20V, maximum current 3A
• Simple and clear structure
• For control, we are not going to use PWM to control the voltage (I personally feel that the stability and risk do not meet the requirements), but use a standard DAC to control it.

Fundamental analysis

• The DC-DC part uses the famous 3R33 module that is most familiar to electronic enthusiasts and has the most information.
• In terms of MCU selection, I originally wanted to use the original stm32F100c8t6, ​​but found that the price of F100 has gone through the roof. Later, after screening, I found that F072 has 2 DACs and the price is not expensive, so I decided to use 072.
• The screen and the auxiliary microcontroller use serial communication, so that the E1 ~ E6 ports are free and can be integrated with the T12 white light soldering iron.

interface

Circuit explanation

24V to 5V part:

This part does not need to be explained, standard dc-dc conversion

Current amplification part:

Standard op amp amplifier circuit, it should be noted that C3 is added to prevent self-excitation;

Microcontroller part:

Note: PA11 PA12 is reserved and not used here.

Power control section

LM358 forms a comparator to obtain the comparison result between the set voltage and current and the actual voltage and current.

The comparison result is summed by two diodes and modulated at the ADJ terminal of 3R33

Note that the two capacitors C7 and C14 prevent self-excitation by changing the phase of the op amp;

C8 is the upper arm capacitance of the voltage dividing resistor, used to prevent high-voltage pulse problems caused by modulation;

Modification of 3R33:

The three components shown in the picture are removed;

physical object

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