Embedded microcontroller for the hottest drive per

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Embedded microcontroller for driving permanent magnet brushless DC motor

I. overview

permanent magnet brushless DC motor (hereinafter referred to as PMBLDC) has been widely used in household consumer products (air conditioners, refrigerators, washing machines) and it peripheral products (printers, floppy drives, hard drives) due to its inherent characteristics. It has the characteristics of simple structure, high efficiency, low noise, high power density, large starting torque, long service life and so on. China is a large country of rare earth. After several years of development, rare earth permanent magnet materials have achieved a certain scale, the quality and data have been greatly improved, and the price has been declining, which will greatly promote the industrial development of PMBLDC. It can be predicted that PMBLDC will become the most widely used motor in the 21st century, and can replace the traditional DC motor and AC motor + frequency conversion and regulation mode, and become the protagonist of motor transmission below 10kW

in addition to the design of the motor itself, the performance of the permanent magnet brushless DC motor should be guaranteed by the driving technology and the driving board to realize this driving technology. The drive board is a key part of the permanent magnet brushless DC motor. Its performance will directly affect the performance index of the whole drive system. With the development of digital electronic products, MCU has been widely used. The drive board of the permanent magnet brushless DC motor is also a bridge connecting the upper control MCU and the power electronic converter: it receives the commands of the upper computer and achieves the predetermined control objectives through certain control methods; At the same time, the current motor state and some basic parameters are returned to the upper control MCU. It can be seen from the above functions of PMBLDC drive board that the core device of this drive board should be an embedded microcontroller with multiple (more than 6) PWM outputs. Considering that there is a broad foundation for the application of Intel MCS-51 series single chip microcomputer in China at present, here we choose Infineon C504 embedded microcontroller which completely adopts 8031 core to improve the overall profitability of the business. The price is low, and the maximum clock frequency can reach 40MHz

II. The hardware driving mode of C504

c50 is also called impact toughness 4. On the basis of 8031 core, in addition to adding peripheral interface functional circuits such as a/d conversion, it also adds a 7-channel full digital PWM output unit CCU (capture/compare unit), which is very suitable for motor control. The functional block diagram of CCU is shown in Figure 1. When C504 operates in the hardware driving mode, cout3 can modulate cc0, cout0, CC1, cout1, CC2, cout2, and its output timing is controlled by INT0, INT1, and INT2 coding

in Figure 1, fosc/2 on the left is the time benchmark for the operation of the whole unit

ctrap end can control the state of cc0-cout2 output end. When in ctrap state, the state of cc0 ~ cout2 can be defined by software

cc0-cout2 terminal is 3-phase 6-channel 16 bit PWM output

ccx and coutx (x=1,1,2) are complementary signals, and their dead time can be controlled by setting the value of offset register

cout3 is a single 10 bit PWM output terminal, while INT0 ~ INT2 is an external control. The output sequence of cc0 ~ cout2 is controlled through the coding of INT0 ~ INT2

Figure 2 shows the current waveform of C504 in the hardware mode when a permanent magnet brushless DC motor with an outer rotor is used as the driving motor of the electric bicycle

this prototype has been put into production by Hangzhou Guangyang Electromechanical Technology Co., Ltd. When the permanent magnet brushless DC motor used for electric vehicle drive is controlled by embedded microcontroller, it can easily realize a series of functions that can not be realized by ordinary analog controller, such as smooth start

III. software driving mode of C504

c504 not only provides hardware driving mode, but also provides software driving mode that can arbitrarily combine PWM output, as shown in Figure 3

any combination mentioned above has two meanings:

1) the number of phases of the motor can be selected, and different CCX and coutx (x=0, 1, 2) terminals can be used

2) the control method can be general PWM or SPWM control, which can be applied to the quasi sinusoidal current control of PMBLDC

Figure 4 shows the current waveform of a dcdd (DC Direct Drive) washing machine. It can be seen from the figure that the current waveform has been very close to sinusoidal, and good control effect has been achieved

IV. conclusion

the CCU unit of Infineon's embedded microcontroller C504 provides the function that is very suitable for PMBLDC motor control to ensure that the specified ash sand ratio is high. By selecting hardware and software modes, the required control purpose can be easily achieved; At the same time, C504 has low price and strong anti-interference. It is very suitable to be used as a control chip and embedded in the middle part between power converter and computer such as driver board. At present, we are using C504 as the underlying embedded control chip of the multi axis control system, and we are preparing to apply it in CNC to restore your work to normal in machinery, printing and other industries

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