Sensorless Motor Drive Current Sampling with Frequency Synchronization
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Solution Overview
Problem
Existing motor driving apparatuses without sensors face challenges in precisely calculating phase currents flowing into motors, which affects efficient and stable motor operation, especially at high speeds.
Innovation Solution
A motor driving apparatus that includes an inverter converting DC power to AC power using a switching operation, a dc stage resistance element, and a control unit synchronizing the frequency of the voltage or rotating frequency of the motor with the sampling frequency of the phase current, allowing for precise calculation and control of the phase current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If sensorless method is used to reduce manufacturing cost, then manufacturing cost is reduced, but measurement precision of phase current deteriorates
Solution Approach 1:
A DC stage resistance element is introduced as an intermediary component between the DC stage capacitor and the inverter. This resistance element enables indirect measurement of phase currents by sampling the DC stage current, which flows through the resistance element. The control unit calculates phase currents based on sampled DC stage current values, providing accurate measurement without requiring additional sensors in the motor phases.
Solution Approach 2:
The DC stage resistance element serves multiple functions: it acts as both a current sampling resistor for measuring DC stage current and as part of the power conversion circuitry. By utilizing this existing component for dual purposes, the system achieves phase current measurement capability without adding separate measurement devices, thereby maintaining cost-effectiveness while improving measurement precision.
2Measurement precision
If phase current is sampled through dc stage resistance element, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The control unit implements a feedback mechanism where sampled DC stage current values are continuously processed to calculate phase currents, which then feed back into the control algorithm for adjusting inverter switching operations. This closed-loop feedback system enables accurate phase current measurement and control while managing complexity through systematic signal processing and control algorithms.
3Measurement precision
If sampling frequency is synchronized with motor rotating frequency, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The sampling frequency is made dynamic rather than fixed, automatically adjusting to synchronize with the motor's rotating frequency. The control unit monitors motor operating conditions and dynamically modifies the sampling rate to maintain optimal synchronization, ensuring accurate phase current measurement across varying speed conditions while adapting the system's behavior to operational requirements.
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 solution enables precise calculation of phase currents, improves motor control accuracy, and enhances transient response characteristics, allowing for stable high-speed motor operation and reduced torque ripple.
Implementation Method 1
an inverter converting DC power of a dc stage capacitor into AC power by a switching operation and outputting the converted AC power to a motor
Implementation Method 2
a dc stage resistance element disposed between the dc stage capacitor and the inverter, and a control unit controlling the inverter based on a phase current sampled through the dc stage resistance element
Data Source
AI summary
The present invention relates to a motor driving apparatus and a home appliance comprising the same. The motor driving apparatus according to an embodiment of the present invention comprises: an inverter which converts a direct current power source of a DC stage capacitor to an alternating current power source and outputs the converted alternating power source to a motor by a switching operation; a DC stage resistance device arranged between the DC stage capacitor and the inverter; and a control unit which controls the inverter on the basis of phase current sampled by means of the DC stage resistance device, wherein the control unit controls the frequency of voltage applied to the motor or the rotation frequency of the motor to be synchronized with the sampling frequency of the phase current sampled via the DC stage resistance device. Accordingly, it is possible to accurately calculate the phase current flowing through the motor by means of the DC stage resistance device.