Since I have never made a brushless motor before, I chose the basic camp this time. Although this project is based on the example project, many improvements have been made based on my own understanding.

1. Power supply part

        The first is the power supply. Since I don’t have a high-power adjustable power supply, I thought of using a mobile phone’s fast charger to provide power. Today’s chargers can easily reach hundreds of watts, so it should be no problem to bring an ordinary brushless motor. This project uses the CH224K chip to draw power from the charger. You can use a jumper cap to switch 9V/12V/20V. These three voltages should be completely sufficient for beginners. Since the Type-C interface is inherently anti-reverse connection, the anti-reverse connection diode can be omitted.

        Then there is the 10V step-down part. The original design used LM2596, but it was too large. And because of the low switching frequency, larger inductors and input and output capacitors were needed, which exacerbated the size problem. Here I switched to the synchronous rectification RY8411, which has greatly improved the size and efficiency, and even lower the cost.

        5V and 3.3V use LDO. I happen to have 78M05 and SPX1117 here, so I used them. Compared with the original design, the advantage is that the output capacitor can use MLCC instead of expensive tantalum capacitors.

2.MOS tube and drive circuit

        The MOS tube I use is Yangjie's YJQ50N03B. This is a sample that Yangjie gave away in Lichuang Mall before, and I just used it this time. YJQ50N03B uses a DFN3*3 package, which is very compact and has an on-resistance of only 6mΩ. After running continuously for half an hour, the biological temperature sensor (hand) was used to test, and the temperature showed almost no change.

        I replaced the gate driver with EG2133, which can directly drive three sets of half-bridges, greatly reducing the area occupied and lower cost.

        A 12V ESD diode is connected in parallel to the gate of each MOS to prevent accidental explosion of the tube. Put the heat shrink tube on the NTC thermistor pin and extend it to the MOS tube to detect the temperature in real time.

3. Current detection and overcurrent protection

        Current detection uses a dedicated current detection amplifier INA180A2. Compared with LM358, it has lower input offset voltage, higher gain accuracy and larger output voltage swing without input bias voltage. Only one decoupling capacitor is required for peripheral components, which greatly simplifies the design and improves measurement accuracy. The fixed gain of INA180A2 is as high as 50 V/V, so the sampling resistor can use a lower 20mΩ, reducing the probability of heat burnout.

        Compared with STM32F030 and F103, CW32F030 has a hardware voltage comparator, so the overcurrent protection can directly use the internal voltage comparator to compare the output voltage of INA180 with the output voltage of the internal voltage divider resistor. When the current is greater than the preset value, it can be directly issued to ATIM. The braking command has a faster response speed than software overcurrent protection, reducing the probability of accidental burnout.

4. Back electromotive force detection

        The back electromotive force detection reduces the attenuation factor to increase the sensitivity of zero-crossing detection, and the clamping diode is replaced with a TVS diode with lower junction capacitance and faster response to reduce the probability of pin burnout.

5. MCU

        Since the ADC is quite important in this design, the analog power supply uses capacitors and magnetic beads for pi-type filtering.

6. PCB

        Due to the above-mentioned volume-optimized design and the deletion of some interfaces that I don't use, the power board and driver board can be integrated on the same 10*10cm board, and there is still plenty of space.

7. Physical display

Overview:

Hardware overcurrent protection:

More details are shown in the video. There are two videos, one is a sensor driver with Hall, and the other is a sensorless driver without Hall.

        Finally, I would like to thank Lichuang and Xinyuan Semiconductor for providing this opportunity, which allows me to learn in depth about brushless motors. I would also like to thank Mr. Li for his sample project, which brought me a lot of inspiration and help. It can be said that this design stands on the shoulders of giants.