Sensorless Rotor Position Detection in Single-Phase BLDC Motors

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Solution Overview

Problem

Single-phase BLDC motors face increased manufacturing costs, larger size, and environmental restrictions due to the use of position detecting sensors, and suffer from prolonged initial driving times without precise position detection.

Innovation Solution

A method and apparatus that detect the position of a rotor magnetic pole by applying a high frequency voltage and measuring changes in current magnitude, eliminating the need for position detecting sensors like Hall sensors, using a high frequency eliminator and magnetic pole detector to determine the polarity of the stator and rotor magnetic poles.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If a position detecting sensor such as a Hall sensor is installed to detect the rotor magnetic pole position, then the detection precision is improved, but the manufacturing cost is increased and the motor size is enlarged

Engineering Contradiction:

Improvedetection precisionVSAvoidmanufacturing cost and motor size

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent extracts the position detection function from the physical sensor (Hall sensor) and implements it through signal processing of the drive waveform. By analyzing the relationship between the drive waveform and back electromotive force waveform, the system determines rotor position without requiring a separate position detecting sensor, thereby reducing manufacturing cost and motor size while maintaining detection precision.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent makes the drive circuit serve multiple functions: it not only drives the motor but also detects the rotor magnetic pole position by analyzing the back electromotive force waveform generated during normal operation. This multi-functionality eliminates the need for dedicated position sensing hardware, resolving the contradiction between detection precision and device complexity.

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Device complexity

If a sensor-less detection method is used to reduce manufacturing cost and motor size, then the device complexity is reduced, but the initial driving time is prolonged due to arbitrary driving

Engineering Contradiction:

Improvemanufacturing cost and motor sizeVSAvoidinitial driving time

Core Design Contradiction:

Device complexityVSLoss of time

Solution Approach 1:

The patent employs feedback by continuously monitoring the back electromotive force waveform during the initial driving phase. By detecting the zero-crossing point of the back electromotive force and comparing it with the drive waveform, the system identifies the actual rotor position and adjusts the driving direction accordingly. This feedback mechanism eliminates the need for prolonged arbitrary driving, significantly reducing initial driving time while maintaining the simplicity of sensor-less operation.

Inventive Principle:

Principle #23Feedback

3Difficulty of detecting and measuring

If arbitrary driving is performed to generate reverse electromotive force for direction detection, then the detection capability is improved, but the productivity is reduced due to extended startup time

Engineering Contradiction:

Improvedetection capabilityVSAvoidstartup speed

Core Design Contradiction:

Difficulty of detecting and measuringVSProductivity

Solution Approach 1:

The patent performs preliminary detection of the rotor magnetic pole position by analyzing the back electromotive force waveform characteristics before initiating full driving operation. By identifying the zero-crossing point and determining the correct driving direction in advance, the system avoids the need for prolonged arbitrary driving and direction corrections, thereby improving startup speed and productivity while maintaining accurate detection capability.

Inventive Principle:

Principle #10Preliminary action

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

This approach reduces manufacturing costs, allows for a smaller motor design, eliminates environmental restrictions, and enables quick and accurate initial driving by determining the rotor position without sensors, reducing overcurrent risks and improving operational precision.

Implementation Method 1

analyzing an offset current by removing a high frequency component included in a current waveform

Methodology Applied

Scientific EffectHigh frequency elimination: Filter (electronic)

Implementation Method 2

determining a stator magnetic pole formed by the current flow in a specific direction and a rotor magnetic pole adjacent to the stator

Methodology Applied

Scientific EffectMagnetic field detection: Magnetic Field

Data Source

PatentEP3783794B1Method and apparatus for detecting rotor magnetic pole position in a single-phase BLDC motor

Publication Date: 2022.09.07 LG ELECTRONICS INC

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AI summary

The present disclosure relates to a method and an apparatus for detecting a rotor magnetic pole of a single-phase BLDC motor. The method and apparatus for detecting a rotor magnetic pole of a single-phase BLDC motor may quickly and precisely initially drive the single-phase BLDC motor by detecting a position of a magnetic pole of a rotor adjacent to a stator by applying a high frequency voltage to the single-phase BLDC motor and analyzing a magnitude of a flowing current.