Sensorless BLDC Motor Startup Using Peak Current Rotor Position Estimation
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Solution Overview
Problem
Sensorless BLDC motor systems face challenges in estimating the initial position of the rotor due to the inability to detect back-electromotive force (BEMF) voltage before rotational operation, affecting operational stability.
Innovation Solution
A motor driver and drive system that sequentially drives three-phase coils through an inverter in various operation modes to detect maximum peak currents, estimating the initial rotor position based on these currents and determining the starting position for stable motor operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If sensorless BLDC motor system uses BEMF voltage detection to estimate rotor position, then operational stability is improved, but the method cannot be applied before rotational operation starts
Solution Approach 1:
The patent applies preliminary action by performing current sensing and peak value detection during the startup phase before the motor begins rotation. The motor driver sequentially drives each phase coil and detects the current peak values in advance, allowing the initial rotor position to be determined before rotational operation commences, thus enabling sensorless control initialization without requiring BEMF voltage which is only available during rotation
2Measurement precision
If Hall sensor is used to detect rotor position, then initial position detection is accurate, but device complexity and cost increase
Solution Approach 1:
The patent applies self-service by utilizing the motor's own phase coils and current sensing capabilities to determine rotor position. The existing motor driver circuitry sequentially drives the phase coils and senses the resulting currents, using the detected peak values to calculate initial rotor position. This eliminates the need for external Hall sensors or additional position detection devices, allowing the motor system to determine its own initial position using resources already present in the system
3Device complexity
If sensorless BLDC motor starts without initial position estimation, then device complexity is reduced, but operational stability deteriorates
Solution Approach 1:
The patent applies preliminary action by implementing a startup sequence where the motor driver sequentially drives each phase coil (first phase coil, second phase coil, third phase coil) and detects current peak values before the motor begins rotation. The initial rotor position is calculated based on these pre-detected peak values, ensuring accurate position estimation is completed in advance, allowing stable sensorless commutation to commence without requiring complex position detection hardware
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 enables stable and efficient initial rotor position estimation, enhancing operational stability and reducing power consumption by using open-loop control to quickly reach target speed before switching to closed-loop control.
Implementation Method 1
The BLDC motor may perform electronic commutation for changing a direction of a current flowing through coils of an armature and form a continuous rotational magnetic field which rotates the rotor
Implementation Method 2
estimating the position of the rotor by detecting a back-electromotive force (BEMF) voltage formed in a three-phase coils when a motor is driven
Data Source
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AI summary
The present disclosure relates to a motor driver capable of simply estimating an initial position of a rotor, and the motor driver according to one embodiment may include a gate driver for sequentially driving three-phase coils of a motor in first to sixth operation modes through an inverter for driving the three-phase coils and an initial position detector for detecting a maximum peak value among first to sixth currents by sensing the first to sixth currents flowing through two-phase coils among the three-phase coils through the inverter in each of the first to sixth operation modes and determine a starting position of a rotor of the motor based on the detected maximum peak value.