In recent years, 180 ° motor control has received extensive attention and application due to its energy saving, quietness and low vibration, especially in the field of home appliances, such as range hoods, refrigerators, air conditioners and washing machines. Renesas Electronics has currently launched a series of 8-bit MCUs dedicated for inverter control. This article mainly introduces the main features of Renesas Electronics 8-bit MCU-uPD78F0712 and solutions for home appliance fans based on this MCU.
1. Applications and characteristics of 180 ° control
At present, household appliances such as water heaters and range hoods are generally required to have the characteristics of low noise, low loss, power saving and energy saving. Therefore, similar occasions are not suitable for AC asynchronous motors driven by inverters, but suitable for small The speed of the power brushless DC motor is adjusted.
Brushless DC motors are divided into BLDC with square wave control (120 ° control) and PMSM permanent magnet synchronous motor with sine wave control (180 ° control). The following table compares the control characteristics of each motor:
Table 1 Motor control characteristics
As can be seen from the above table, within the range of small power motors, 180 ° motor control has the advantages of low noise and high efficiency.
At present, the most advanced 180 ° control technology on the market is the frequency conversion technology based on the field-oriented vector. The FOC (field-oriented) vector control algorithm generates a vector-form phase voltage to control the stator current. The control principle is that a certain coordinate conversion can be used to Direct control of magnetic flux and torque realizes double closed-loop control of current and speed, which can achieve fast dynamic response without generating large current.
2. Application of 180 ° motor control in home appliances
â‘ Range hood
At present, it is more common on the market to have gear frequency conversion range hoods, and only a small number of hood manufacturers have begun to adopt 180 ° motor-controlled gearless frequency conversion range hoods.
Compared with other types of frequency conversion range hoods, 180 ° frequency conversion range hoods have the following characteristics:
1) The presence or absence of oil fume can be identified according to the sensor, and the suction of the range hood can be intelligently started and stopped without manual operation;
2) When frying, frying, or frying, the air volume of the range hood can be adjusted automatically according to the size of the range;
3) When stewing, boiling, steaming, and cooking, automatically reduce the suction speed to reduce power consumption;
4) Mute. The user can not feel the noise of the motor running; 5) The smaller size of the motor makes the range hood smaller.
â‘¡Water heater
In order to improve the safety of users, traditional household fast gas water heaters are mostly closed-burning strong exhaust water heaters with built-in blower devices, and the working noise is loud; in addition, due to uncomfortable pressure or improper setting of the burner, water The heat or water is too hot, and sometimes discomfort such as sudden cold and hot during the bath.
The motor operation of the 180 ° frequency conversion gas water heater is to adjust the speed according to the actual output heat load of the machine. The outlet temperature is relatively constant, and there is no need to manually adjust the heating speed. The 180 ° permanent magnet synchronous motor runs smoothly than the AC asynchronous motor, so the motor operation sound is also Relatively light.
â‘¢Air purifier
Ordinary air purifiers on the market have the problem of high noise and power consumption when turned on for a long time. In the case of the same cost, the motor noise of the 180 ° inverter air purifier is low, and it will automatically sense the cleanliness of the air according to the sensor, adjust the operation of the motor to drive the purification, save electricity, and save electricity.
In comparison, it is not difficult to see that the prospect of 180-degree motor control is better. Although the cost of variable-frequency motor control is relatively high, its high performance, quietness, and low loss provide escort conditions for its favorable promotion. Many home appliance manufacturers began to pay attention to and invested in 180 ° motor control to improve the efficiency of home appliances and reduce noise.
3. Renesas Electronics (Renesas Electronics) 8-bit MCU promotes motor design
The 180 ° inverter motor uses vector control for the motor to achieve the purpose of frequency conversion. Therefore, the MCU has high requirements, such as range hoods, water heaters, air purifiers, etc. need more auxiliary functions such as LCD display, delay control, etc. The MCU also needs some unique peripherals such as serial communication and powerful timers.
Renesas Electronics has developed a series of 8-bit MCUs including 78K0 / IY2, 78K0 / IA2, 78K0 / IB2, uPD78F0712, uPD78F0714, uPD789842 and uPD780988 for motor control. This series of products integrates internal hardware multipliers, timers, multiple general registers, programmable pulse generators, and independent frequency conversion control modules. The peripherals dedicated to motor control applications make them more suitable for small and medium-power 180 ° frequency conversion motors.
In the 180 ° variable frequency motor control algorithm, coordinate transformation and inverse transformation, multiplication and a lot of loop control are used, so the speed of the MCU is required to be fast, and the hardware multiplication / divider of the 8-bit MCU of Renesas Electronics can quickly perform FOC Vector control operation, PID drop and coordinate transformation.
This series of 8-bit MCUs have 6 external interrupts, which can quickly respond to external interrupts, such as sensor feedback information, which greatly reduces the cost of motor control solutions. It has 32 8-bit (or 16 16-bit) Bank structures The general-purpose register makes the operation efficiency higher.
The 180 ° frequency conversion motor is generally used in high-end household appliances. Renesas ’8-bit MCU programmable pulse generator (PPG) can specify the pulse width and pulse period. This can be directly used for the display of household appliance fan speed and air volume. Provide online self-programming function, and these MCUs do not need external EEPROM, and its own is enough.
In addition, these 8-bit MCUs of Renesas Electronics are equipped with 2 dedicated frequency conversion control modules, which can generate interrupts at any time in the PWM cycle, and can sample the current at any time according to user needs; External signal input can quickly stop the fan rotation under abnormal conditions; in addition, it also has programmable dead zone control (dead zone time range: 0.1 s ~ 25.6 s).
Figure 2 shows the main features of the 8-bit frequency conversion control MCU, Table 2 gives a detailed description of these functions.
Figure 2 MCU characteristics of Renesas Electronics
Table 2 Features of 8-bit MCU for frequency conversion control
Renesas Electronics 180 ° Variable Frequency Motor Control Scheme
Renesas Electronics has developed a set of unique functions based on 8-bit MCU uPD78F071x
180 ° vector control scheme HS / DC-8, Figure 2 shows the system configuration.
Figure 2 HS / DC-8 system configuration
HS / DC-8 uses the unique hardware functions of 8-bit MCU to realize 180 ° vector control (FOC), calculates the value of PWM duty cycle of vector control by feedback speed, and drives the power module with space vector PWM (SVPWM) output , Directly control the motor torque, the motor speed feedback uses Hall sensor.
HS / DC-8 driver is suitable for small power motors with rated capacity of 20W ~ 1KW, electrical angular frequency of 6 ~ 120Hz, and permanent magnetic flux below 0.5Wb.
Compared with other semiconductor manufacturers MCU HS / DC-8 motor control solutions have the following advantages:
ï¬ Low loss, the dedicated variable frequency control timer in the MCU can realize the low loss PWM mode of two-phase modulation, which can reduce the power switch tube loss in the inverter by about 30%, thereby extending the life of the driver
ï¬ High efficiency and low noise. Because the hardware multiplier of MCU can quickly implement the 180 ° vector control algorithm, automatic phase control is added to the program to ensure that the motor current is always kept at the minimum value for automatic control
ï¬ Rich protection and customization functions rely on the powerful timer function, rich IO function and AD function in MCU, such as dead zone protection, Hall type selection, frequency feedback pulse number selection, PWM initialization abnormal detection, Overvoltage protection, etc.
ï¬ Low cost, 8-bit MCU saves external EEPROM and internal hardware capture unit, making MCU cost lower
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