Home appliance fan solution based on uPD78F0712

With the development of science and technology, 180° motor control is increasingly used in various fields, especially in the field of home appliances. Renesas Electronics has introduced a series of 8-bit MCUs for inverter control. This article mainly introduces the main features of Renesas Electronics 8-bit MCU-uPD78F0712 and the home appliance fan solution based on the MCU.

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1. Application and characteristics of 180° control

At present, household appliances such as water heaters, range hoods, etc. generally require low noise, low loss, and energy saving. Therefore, similarly, it is not suitable to use an AC asynchronous motor driven by a frequency converter, and is suitable for small use. Power brushless DC motor for speed regulation.

The brushless DC motor is divided into a square wave controlled BLDC and a sine wave controlled PMSM permanent magnet synchronous motor. The table below compares the control characteristics of each motor:

Table 1 Motor Control Features

As can be seen from the above table, 180° motor control has the advantages of low noise and high efficiency in the range of small power motors.

At present, the most advanced 180° control technology on the market is based on the variable frequency technology of magnetic field oriented vector. The FOC (Field Oriented) vector control algorithm generates vector phase voltage for controlling the stator current. The control principle is that it can be converted by certain coordinates. Direct control of flux and torque for dual closed-loop control of current and speed for fast dynamic response without large currents.

2.180° motor control in home appliances

1 range hood

The range hood, which is used in the family kitchen to absorb the cooking fumes generated during cooking, not only can perform the functional function well, but also has the decorative concept of blending the modern kitchen pattern. After the development of the range hood, the range hood has not been limited to the simple tools of the kitchen to remove the fumes, but to add more entertainment functions and functions, such as the addition of the TV display entertainment hood, and the integration with the smart home. The hood of the security system is equipped with a network-controlled network hood.

The design of the range hood should be easy to effectively remove the accumulated grease and dirt, and the surface of the casing should be as smooth as possible. Usually, the range hood needs to be fixed on the wall, so in addition to the keys, holes, hooks, etc., it is required to have a suitable device to fix it to the wall, and the device should be difficult to move or deform. Made of metal.

At present, the more common on the market is the gear shifter range hood. Only a small number of hood manufacturers have adopted the 180° motor-controlled gearless range hood.

Compared with other types of inverter hoods, 180° inverter hood has the following characteristics:

1) It can identify the presence or absence of soot according to the sensor, and intelligently start and stop the suction of the range hood without manual operation;

2) When frying, frying and frying, the air volume of the range hood can be automatically adjusted according to the amount of soot;

3) When stewing, braising, steaming, boiling, automatically reduce the suction speed and reduce the power consumption;

4) Silent. The user is not aware of the noise of the motor running; 5) The smaller volume of the motor makes the range hood smaller.

2 water heater

In order to improve the safety of users, the traditional domestic fast gas water heaters are now mostly closed-type combustion exhaust air heaters with built-in air blowing devices, which work loudly; in addition, water is often not present due to improper pressure or improper setting of the burner pressure. Heat or water is too hot, and sometimes in the process of bathing, there will be discomfort such as cold and heat.

The motor running of the 180° variable frequency gas water heater is to adjust the speed according to the actual output heat load of the machine. It is not necessary to manually adjust the heating speed. The 180° permanent magnet synchronous motor runs smoothly compared with the AC asynchronous motor, so the motor running sound is relatively light.

3 air purifier

Air purifier (also known as "air cleaner", air freshener) refers to the ability to adsorb, decompose or convert various air pollutants (generally including dust, pollen, odor, formaldehyde and other decoration pollution, bacteria, allergens). Etc.) Products that effectively improve air cleanliness are currently dominated by household and commercial air purifiers that remove indoor air pollution.

The common air purifiers on the market have large noise, and the problem of power consumption is long when the battery is turned on for a long time. At the same cost, the 180° variable frequency air purifier motor has low noise, and it automatically adjusts the motor's operation to clean, save power and save energy according to the sensor's perceived air cleanliness.

In contrast, it is easy 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 conditions for its favorable promotion. Many home appliance manufacturers have begun to pay attention to and invest in 180° motor control to improve the efficiency of home appliances and reduce noise.

Buying an air purifier is nothing more than trying to trade it for healthy and fresh air. Whether or not to use an air purifier is a basic prerequisite for determining whether it is desirable. The air purifier's outer casing, movement and purification technology will directly affect the safety of the air purifier. Purification technology should be chosen to be the same as positive and negative ions in nature, and there are 13 foreign institutions that have certified their safety ion purification technology.

There are five internationally accepted principles for air purification, physical, electrostatic, chemical, negative, and composite. In general, an air purifier that uses multiple purification methods at the same time will have a better purification effect. For example, large particles such as dust, odor, and pollen can be filtered by physical purification; while harmful substances such as allergens, viruses, and formaldehyde require chemical purification to purify them.

According to the purification method, it is divided from the active direction, the purification method is divided from the active direction, and there are three methods: active purification method (air purification) and passive purification method (fixed point purification) and active and passive composite purification. The passive purification method only has a purifying effect on the inhaled air; the active purification method has a purifying effect on the entire space. Active-passive composite purification is a combination of the two, and the effect is better.

3. Renesas Electronics 8-bit MCU promotes motor design

In the 180° inverter motor, the vector control is used for the motor to achieve the purpose of frequency conversion. Therefore, the requirements for the MCU are high, such as the range hood, water heater, air purifier, etc., which require more auxiliary functions such as liquid crystal display and delay control. MCUs also need some unique peripherals such as serial communication, powerful timers, and so on.

Renesas Electronics has developed a series of 8-bit MCUs including motor control including 78K0/IY2, 78K0/IA2, 78K0/IB2, uPD78F0712, uPD78F0714, uPD789842 and uPD780988. This series integrates internal hardware multipliers, timers, multiple general-purpose registers, programmable pulse generators, and independent variable frequency control modules. The peripherals dedicated to motor control applications make it suitable for medium and small power 180° variable frequency motors.

In the 180° inverter motor control algorithm, coordinate transformation and inverse transformation, multiplication operation and a large number of loop control are used. The hardware multiplier/divider of Renesas Electronics 8-bit MCU can quickly perform FOC vector control operation and PID fall generation. , coordinate transformation.

This series of 8-bit MCUs has 6 external interrupts, which can quickly respond to external interrupts, such as sensor feedback information, which greatly reduces the cost of the motor control scheme. It has 32 8-bit Bank structure general-purpose registers, which makes the operating efficiency higher.

180° inverter motor is generally used in medium and high-end household appliances. Renesas electronic 8-bit MCU programmable pulse generator can specify pulse width and pulse period, which can be directly used for home appliance fan speed and air volume display, while MCU provides online self-service. Programming features, and these MCUs do not require an external EEPROM, and it's already sufficient.

In addition, these 8-bit MCUs from Renesas Electronics have two dedicated variable frequency control modules that can generate interrupts at any time during the PWM cycle. The current can be sampled at any time according to user requirements and can be used to control PWM high-impedance output. External signal input can quickly stop fan rotation under abnormal conditions; it also has programmable dead zone control.

Figure 2 shows the main features of the 8-bit inverter control MCU, and Table 2 gives a detailed description of these functions.

Figure 2 Renesas Electronics' MCU Features

Table 2 8-bit MCU features for inverter control

Renesas Electronics 180° inverter motor control solution

Renesas Electronics has developed a unique feature based on the 8-bit MCU uPD78F071x

The 180° vector control scheme HS/DC-8, Figure 2 shows the system configuration.

Figure 2 HS/DC-8 system composition

The HS/DC-8 utilizes the unique hardware functions of the 8-bit MCU to implement 180° vector control (FOC), calculates the vector-controlled PWM duty cycle value by feedback speed, and uses the space vector PWM (SVPWM) output to drive the power module. Directly control the motor torque, and the motor's speed feedback uses a Hall sensor.

The HS/DC-8 driver is suitable for low-power motors with rated capacity of 20W~1KW, electrical angular frequency of 6~120Hz, and permanent magnetic flux of 0.5Wb or less.

The motor control scheme of the MCU HS/DC-8 compared to other semiconductor manufacturers has the following advantages:

Low loss, dedicated inverter control timer in MCU, can achieve two-phase modulation low-loss PWM mode, which can reduce the power switch loss in the inverter by about 30%, thus extending the life of the driver

High efficiency, low noise, the MCU hardware multiplier can quickly realize the 180° vector control algorithm, and the automatic phase control is added to the scheme to ensure that the motor current is always kept at the minimum value for automatic control.

Rich protection and customization functions depend on the powerful timer function, rich IO function and AD functions in the MCU, such as dead zone protection, Hall type selection, frequency feedback pulse number selection, PWM initialization abnormality detection, Pressure protection

Low cost, 8-bit MCU saves external EEPROM and internal hardware capture unit, reducing MCU cost