Sensorless Fan Motor Driving Apparatus with Back-EMF Detection
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Solution Overview
Problem
Existing sensorless fan motor driving techniques lack versatility, as they are optimized for specific motor characteristics and struggle to start up various types of fan motors due to differences in rotational speed and torque, limiting their application across different devices.
Innovation Solution
A driving apparatus with a back electromotive force detection circuit, rotor position detection circuit, forced synchronization signal generating unit, and driving signal synthesizing circuit that generates driving control signals based on both rotation detection and forced synchronization signals, allowing the fan motor to start up in different modes depending on the presence of back electromotive force, ensuring operation across various fan motor types.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a position detection function is used to detect rotor position and generate driving signals, then the sensorless motor can rotate in the normal direction, but the driving apparatus lacks versatility and cannot start up different types of fan motors with varying characteristics
Solution Approach 1:
The driving apparatus dynamically switches between two startup modes: position detection mode and forced synchronization mode. The control unit selects the appropriate mode based on whether back electromotive force is detected during startup, allowing the system to adapt to different fan motor characteristics while maintaining reliable operation
Solution Approach 2:
The system changes operational parameters by switching between different driving methods. In position detection mode, the driving signal is generated based on detected rotor position. When back electromotive force is insufficient, the system transitions to forced synchronization mode where the driving signal follows a predetermined synchronization signal, effectively changing the control parameter to accommodate different motor types
2Reliability
If the driving apparatus is optimized for specific motor characteristics, then it can reliably start up that type of motor, but it cannot accommodate other types of fan motors with different rotational speeds and torque
Solution Approach 1:
The driving apparatus achieves universality by incorporating dual startup capabilities. The position detection circuit enables optimized startup for motors with sufficient back electromotive force, while the forced synchronization circuit provides a universal fallback mechanism for motors with varying characteristics, making the apparatus applicable to multiple fan motor types without requiring separate driving circuits for each
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The apparatus provides improved versatility by ensuring reliable startup of various sensorless fan motors, reducing the need for external capacitors and minimizing circuit size, while maintaining efficient operation across diverse fan motor characteristics.
Implementation Method 1
a back electromotive force detection circuit configured to compare, in a state in which the sensorless fan motor is rotating, a back electromotive force voltage that occurs at one terminal of each of the multiple coils
Data Source
AI summary
A BEMF detection circuit generates a rotation detection signal indicating a comparison result between electromotive force voltages VU through VW which occur at a terminal of respective multiple coils and an intermediate-point voltage VCOM. A rotor position detection circuit generates a rotor position detection signal indicating a stopped rotor position An internal start-up synchronization signal generating unit generates a predetermined-frequency forced synchronization signal. Upon receiving a fan motor start-up instruction, a driving signal synthesizing circuit generates a driving control signal based upon the rotor position detection signal. Thus, (1) when back electromotive force voltage occurs, a sensorless driving operation is started based upon the rotation detection signal; (2) when it does not occur, the driving control signal is generated based upon the forced synchronization signal. Subsequently, when it occurs, the sensorless driving operation is started based upon the rotation detection signal.