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Interpreting Robot Vacuum Cleaner from Perspective of Semiconductor Components

As an imported product, robot vacuum cleaner belongs to the "latecomers" of smart home products in the Chinese market. In recent years, as the functionality and technology of robot vacuum cleaner change, the cleaning coverage rate of mainstream robot vacuum has been significantly improved. Some flagship models even can reach zero error and the hair, dust, debris cleaning effect of these robots are far better than manual cleaning. Accordingly, the market demand increases year by year.


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According to Euromonitor and IFR, the global market scale of robot vacuum cleaner in 2019 is about $3.3 billion (approximately RMB 21.12 billion), rising to $5.5 billion (approximately RMB 35.2 billion) in 2020. With the market scale and penetration rate showing a year-on-year growth, the scale is estimated to reach $23.14 billion by 2024. Thanks to its huge consumer base, China has become the world's largest market for robot vacuum cleaner. In 2020, the sales volume in China is 9.41 billion yuan, with an explosive growth rate of 22% year-on-year.


Robot vacuum cleaner has a high degree of smartness in the category of service robots. In addition to basic features such as vacuuming and mopping, smart features have also been greatly enhanced. The successful application of AI visual recognition, dToF navigation, 3D structured light and other technologies enables a better user experience. At the same time, these new functionalities are providing many opportunities for the application of semiconductor components.



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The structure of a robot vacuum cleaner can be divided into five parts: system control module, motor module, sensor module, communication module and power module. The robot perceives the external environment through ultrasonic sensors and proximity sensors in the sensor module, feeds the collected data to the system control unit, and accordingly plans the overall operation track through the internal algorithm, achieving an overall smart cleaning solution of "positioning-framing-planning-cleaning". 



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Fig. 1 Application of robot vacuum cleaner



#1
Protection Solution for Charging End and Other Peripheral Interfaces




Smart robot vacuum cleaner can follow the optimal cleaning path for a complete cleaning on its own. When it runs out of power, it can automatically return to the charging pile. The protection of charging port is especially important. Since it is exposed on the outside, the internal circuitry is vulnerable to damage if there is no corresponding protection. In addition, many external interfaces and sensors such as buttons, USB ports, RF antennas and IO ports need to be ESD protected.

Protection principle: A combination of TVS and OVP is used for surge protection. When there is an abnormal transient high voltage at the charging end, the TVS on the input side will quickly clamp the high surge voltage to a lower level. When the input voltage still exceeds the OVP threshold voltage, OVP will quickly respond and cut off the main circuit to protect the back-end component from causing intermittent or permanent failure.




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Figure 2 Charging protection application



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#2
Power Module Application




Power module is the power source of a robot vacuum cleaner. Good power management enables the internal components of a sweeper to work under the most suitable voltage, further ensuring a stable operation of the whole system. 

Wayon LDO products are all in small packages with performances such as wide voltage input, low power consumption, low noise, and fast response, which can improve the overall efficiency of power modules and extend the lifespan of battery.



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Figure 3 Power converter



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#3
Driver and Signal MOSFET Application




How can we “drive” a robot vacuum cleaner to work for us? The answer is smart control plus smart drive. In a control/drive module, the most common way is to use a driver IC to directly drive the MOSFET. The drive capability of the IC, the parasitic capacitance of the MOSFET and the resistance value of the resistor will all affect the switching speed of the MOSFET.

It is very difficult to define which of the various MOSFETs is the best to drive a circuit. Depending on the customer's application, combined with manufacturers' products, continuous optimization of circuits and parameters makes a most suitable solution possible. For this reason, Wayon has developed a full range of drive-MOSFETs and signal-switching- MOSFETs to meet different needs.



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Figure 4: Driver application



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#4
Battery Protection Application




For a robot vacuum cleaner, Lithium battery is its "source of power". Overcharge, over discharge and over current can all affect the performance and lifespan of the battery. In worst case, it can even cause combustion and explosion. Each lithium battery is required to install a protection board, which consists of a special IC and a number of lithium protection MOSFETs, fuses and other external components. Damages to the battery can be effectively monitored and prevented through the protective loop, thereby avoid the danger caused by overcharge, over-discharge and short circuit.

Protection principle: In a battery protection circuit, SMD-type ceramic PTCs are connected in series. When the 1st level protection (in this case MOSFET) is overheated, the resistance of the ceramic PTC changes suddenly, thereby partial voltage increases greatly, which triggers the MOSFET to operate.



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Figure 5: 1st and 2nd level protection

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Figure 6: example of detailed 2nd level protection



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