Abstract: This paper introduces the features and working principles of Motorola's MC33035 and MC33039 chips specifically designed for brushless DC motor control. The system design consists of two main parts: a control circuit and a power drive circuit. The control circuit, based on the MC33035/33039, receives the feedback position signal, combines it with the speed setpoint, determines the energized winding, and outputs switching signals. In the drive circuit design, a three-phase Y-connected fully controlled circuit is adopted, composed of six high-speed MOSFET switches. Experiments show that the motor operates stably. Keywords: brushless DC motor; MC33035/33039; control circuit; drive circuit[b][align=center]Design of control system for Brushless DC Motors SUN GuanQun;SHI Ming;TONG LinYi;XU YiPing[/align][/b] Abstract: It introduces the MOTORALA company used for the characteristics of the chip MC33035 and MC33039 which control the brushless direct current motor exclusively and its work principle. The system design divides into two major parts: the control circuit and the power driver circuit, the control circuit take MC33035/33039 as the core, receive feedback position signal, with the judgment speed to the quota synthesis, the judgment circular telegram winding and produces the switching signal. In the actuation circuit design, uses the three-phase Y joint all to control the electric circuit, uses six high speed MOSFET switching valve to compose. Through the experiment, the electric motor movement stable is reliable. Keywords: Brushless DC Motor; MC33035/33039; Control circuit; Drive circuit 1. Introduction Permanent magnet brushless DC motors are a new type of mechatronic motor that has rapidly matured in recent years. This motor consists of a stator, rotor, and Hall effect sensors for rotor position detection. Due to the absence of an excitation device, it boasts high efficiency, simple structure, and excellent operating characteristics. Furthermore, it offers advantages such as smaller size, higher reliability, easier control, wider application range, and more convenient manufacturing and maintenance, making the research of brushless motors of great significance. This system design utilizes voltage regulation for speed control, adjusting the voltage by changing the duty cycle of the PWM power supply. This design employs the MC33035, a dedicated control chip for brushless DC motors. It can decode the position signal detected by the Hall effect sensor and also features auxiliary functions such as overcurrent, overheat, undervoltage, and forward/reverse selection. The system requires simple peripheral circuitry, eliminating the need for designers to use discrete components to construct large analog circuits, which would otherwise complicate system design and debugging and require a large circuit board area. The MC33035 and MC33039 integrated chips can easily perform forward and reverse rotation, start-up, dynamic braking, overcurrent protection, three-phase drive signal generation, and simple closed-loop control of motor speed for brushless DC motors. The brushless DC motor control system constructed using dedicated integrated chips features high integration, high speed, and comprehensive protection functions. The drive circuit structure is simple, resulting in fewer external components and simpler wiring, significantly reducing the inverter size. 2. System Principle This closed-loop speed control system uses three Hall effect integrated circuits as rotor position sensors. The reference voltage (6.24V) at pin 8 of the MC33035 is used as their power supply. The output signal of the Hall effect integrated circuits is sent to the MC33035 and MC33039. The system control structure block diagram is shown in Figure 1. The output of the MC33039 is smoothed by a low-pass filter and introduced into the inverting input of the error amplifier of the MC33035. The speed command signal is input to the non-inverting input of the error amplifier of the MC33035 through an integrator, thus forming the closed-loop speed control of the system. [align=center]Figure 1 System Control Principle[/align] 3. Control Circuit Design The MC33035 has a wide operating power supply voltage range, between 10V and 30V, and contains an internal reference voltage of 6.25V. The rotor position decoder inside the MC33035 is mainly used to monitor the three sensor inputs so that the system can correctly provide the correct timing for the high-end and low-end drive inputs. The sensor inputs can be directly connected to open-collector Hall effect switches or optocouplers. In addition, the circuit also contains pull-up resistors, and its input is compatible with TTL levels with a typical threshold value of 2.2V. Three-phase motors controlled by the MC33035 series can operate in the four most common sensor phases. The 60°/120° selection provided by the MC33035 allows the MC33035 to easily control motors with sensor phases of 60°, 120°, 240°, or 300°. The MC33035's three sensor inputs have eight possible input code combinations, six of which are valid rotor positions, while the other two are invalid. These six valid input codes allow the decoder to determine the motor rotor position within a 60° electrical phase window. The MC33035's forward/reverse outputs can change the motor's direction of rotation by flipping the voltage on the stator windings. When the input state changes, the specified sensor input code changes from high to low, altering the rectification timing to change the motor's rotation direction. Motor on/off control is achieved via output enable. When this pin is open, the built-in pull-up resistor connected to the positive power supply will initiate the top and bottom drive output timings. When this pin is grounded, the top drive output will be turned off, and the bottom drive will be forced low, thus stopping the motor. The operating principles and methods of the error amplifier, oscillator, pulse width modulation, current limiting circuit, on-chip voltage reference, undervoltage lockout circuit, drive output circuit, and thermal shutdown circuits in the MC33035 are basically similar to those of other similar chips. The MC33035's peripheral circuit is shown in Figure 2. [align=center]Figure 2 MC33035 Peripheral Circuit[/align] As shown in the figure, we supply a 24V power supply. The F/R control rotates the motor. The forward/reverse output can change the motor direction by flipping the voltage on the stator winding. When the input state changes, the specified sensor input code will change from high to low, thereby changing the rectification timing to make the motor change its rotation direction. The motor on/off control can be implemented by the output enable pin 7. When this pin is open, the built-in pull-up resistor connected to the positive power supply will start the top and bottom drive output timing. When this pin is grounded, the top drive output will be turned off, and the bottom drive will be forced low, thereby stopping the motor. Since the MC33035's 8 pins provide a standard 6.25V voltage output, this voltage can be used to power Hall effect devices and other devices. In this system, the generation of the PWM signal is easy, and the frequency of the PWM signal can be adjusted by an external circuit. Its frequency is determined by a formula. R5 is a variable resistor. By adjusting R5, the frequency of the PWM signal can be changed. The required pulse width modulation (PWM) signal can be generated simply by adding a capacitor, a resistor, and an adjustable potentiometer to the MC33035. Since the MC33035's 8-pin output is a standard 6.25V voltage, an RC oscillator is formed by R6 and C1. Therefore, the input at pin 10 is approximately a triangular wave, the frequency of which is determined by the voltage. R5 is a potentiometer that controls the brushless motor's speed. Changing the voltage at pin 11 relative to ground through this potentiometer changes the motor's speed. Operational amplifier 1 is externally connected as a follower, so the voltage at pin 11 relative to ground is the inverting input voltage of comparator 2. Changing the voltage at pin 11 relative to ground through potentiometer R5 changes the duty cycle of the square wave output of comparator 2, resulting in the desired PWM signal output. Pin 14 is the fault output terminal. L1 is used as a fault indicator. When an invalid sensor input code, overcurrent, undervoltage, internal chip overheating, or low-level enable pin occurs, the LED illuminates as an alarm, and the system is automatically locked. Normal operation can only be restored after the fault is cleared and the system is reset. R6 and C1 determine the internal oscillator frequency (i.e., the PWM modulation frequency). The output of the speed setting potentiometer W is input to the non-inverting input of the error amplifier of the MC33035 after integrator. Its inverting input is connected to the output. In this way, the error amplifier forms a unity-gain voltage follower, thereby completing the speed control of the system. Pin 8 is connected to an NPN transistor. When the voltage at pin 8 is high, the transistor conducts, providing voltage to the MC33039 and the Hall sensor. Electrolytic capacitor C2 serves as a filter to prevent current backflow. When the input voltage at pin 17 of the MC33035 is below 9.1V, since pin 17 is connected to the non-inverting input of an internal comparator, and the inverting input of this comparator is the internal 9.1V standard voltage, the MC33035, through an AND gate, blocks all three outputs of the lower bridge, turning off all three power transistors of the lower bridge, stopping the motor and providing undervoltage protection. Overheat protection and other functions are handled by the chip's internal circuitry, eliminating the need for external circuitry. The brushless DC motor in this system has three built-in Hall effect sensors to detect the rotor position. Once the commutation is determined, the motor speed can be calculated based on the signal. The sensor outputs are directly connected to pins 4, 5, and 6 of the MC33035. During normal motor operation, the Hall sensors generate three overlapping signals with a pulse width of 180 electrical degrees, resulting in six forced commutation points. The MC33035 decodes these three Hall signals to ensure correct motor commutation. When pin 11 of the MC33035 is grounded, the motor speed is 0, thus achieving braking. The MC330399 is a brushless motor closed-loop speed controller specifically designed by Motorola to work with the MC33035. It is an 8-pin dual in-line package (DIP) narrow integrated circuit. The MC330399 processes the input rotor position signal code to generate a speed voltage signal proportional to the actual motor speed. The three-phase position detection signals (SA, SB, SC) from the motor rotor position detector are sent to the MC33035. After processing by the chip's internal decoding circuit and combining the control logic signal states of the forward/reverse control terminal, start/stop control terminal, braking control terminal, and current detection terminal, the six original control signals for the inverter's three-phase upper and lower bridge arm switching devices are generated. Among them, the three-phase lower bridge switch signal is further processed by pulse width modulation according to the brushless DC motor speed control mechanism. The processed three-phase lower bridge PWM control signals (AB, BB, CB) and three-phase upper bridge control signals (AT, BT, CT) are amplified and applied to the six switching transistors of the inverter to generate the three-phase square wave AC current required for normal motor operation. Meanwhile, the rotor position detection signal is also fed into the MC33039, converted by an F/V converter to obtain a pulse signal FOUT with a frequency proportional to the motor speed. This signal is filtered by a simple RC network to form a speed feedback signal. A simple P regulator can be constructed using the error amplifier in the MC33035 to achieve closed-loop control of the motor speed. In practical applications, various external PI and PID control circuits can be used to achieve complex closed-loop control, as shown in Figure 3. [align=center] Figure 3 Circuit diagram of the closed-loop control system constructed by MC33039[/align] The number of pulses output from pin 5 of the MC33039 is 12 pulses per revolution of the motor. The timing element is selected according to the maximum motor speed. Assume the maximum speed is 3500 r/min, or 58 r/s. At this point, the number of pulses output per second is 58 × 12 = 696. That is, its frequency is approximately 700Hz, and the period is approximately 1.4ms. According to the MC33039 datasheet, the timing component parameters are R21 = 100KΩ, C4 = 0.01uF, and the monostable circuit generates a pulse width of 1340ns. Pin 8 is connected to the reference voltage of the MC33035. The output from pin 5 is connected to pin 12 of the MC33035 (the inverting input of the error amplifier) ​​via a 100kΩ resistor. The amplifier gain is 10 times at this point, and the 0.1μF capacitor acts as a filter for smoothing. MC33035 oscillator parameters: resistor 5.1kΩ, capacitor 0.1μF, PWM frequency approximately 2.4kHz. This system uses a non-inductive resistor (0.04Ω, 0.5W) for current sensing, connected to pin 9 via a 1.1kΩ resistor. Since pin 22 is grounded and at a low level, the control circuit operates under a 120° sensor electrical phase input state. 4. Drive Circuit Design [align=center] Figure 4 Drive Circuit Diagram[/align] As shown in Figure 4, the three drive signals output from the lower bridge can directly drive the IRF530 N AC power MOSFET, and the three drive signals from the upper bridge can directly drive the IRF9530 P AC power MOSFET. The signals from pins 1, 2, and 24 of the MC33035 are amplified by the IRF9530, and the signals from pins 19, 20, and 21 are amplified by the IRF530 to drive the brushless DC motor. A, B, and C are connected in a delta configuration with the three-phase windings of the brushless DC motor. 5. Experimental Results [align=center] Figure 5 Drive Signals[/align] The two drive signals in Figure 5 belong to the drive signals of the upper and lower MOSFETs of a certain bridge wall. Comparison shows that each switch conducts for 120° in one cycle, and the two drive signals cannot overlap. 6. Conclusion The DC brushless motor control system designed in this paper is implemented purely in hardware. It features simplicity, reliability, small size, and low cost. Especially when combined with the MC33039 to form a closed-loop speed control, its speed regulation performance is excellent. However, because the MC33035's PWM modulation method adjusts the duty cycle, it is difficult to improve the output current waveform, resulting in some torque ripple during motor operation. In summary, the MC33035 is very suitable for controlling low-power brushless motors, especially for servo mechanisms and mechatronic speed control devices. References: [1] Zhang Chen. Principles and Applications of DC Brushless Motors (Second Edition). Beijing: Machinery Industry Press. 2004. [2] Tan Jiancheng. Dedicated Integrated Circuits for Motor Control. Beijing: Machinery Industry Press. 1997. [3] Wan Guoqing, Xu Qingquan, Cui Xiaoyun. MC33035 Brushless Motor Drive Controller and Application [A]. Journal of Changzhou Institute of Technology, 2005, 18 (5): 36-39. [4] Wei Min, Ji Xiaoyin. Application of MC33035 in DC Brushless Motor Control. Electrical Engineering Technology Magazine, 2004, 11: 83-85. [5] Pan Jian. Principles and Applications of MC33035 Brushless DC Motor Controller [B]. 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