Motor Drive Control Device for Accurate Back-EMF Detection
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Solution Overview
Problem
The existing motor drive control devices for voice coil motors in hard disk devices face challenges in accurately detecting counter electromotive voltage due to temperature-induced resistance changes and manufacturing errors, leading to inaccuracies in speed control of the magnetic head, especially when integrated in high-density semiconductor integrated circuits with limited chip area.
Innovation Solution
A motor drive control device that includes a digital control unit, a digital/analog converter, a driver output unit, a drive current detection amplifier, and a counter electromotive voltage detection unit with digital multipliers and registers to calibrate and compensate for resistance variations and offset voltages, enabling precise detection of counter electromotive voltage and improving speed control accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a dedicated hardware circuit is used to detect counter electromotive voltage, then detection speed is improved, but temperature-induced resistance changes cause large errors in detected values
Solution Approach 1:
The patent replaces the dedicated hardware circuit (analog detection system) with a digital detection system using an analog-to-digital converter (ADC) and CPU. The counter electromotive voltage is converted to a digital signal and calculated through digital processing, eliminating the temperature sensitivity issues of analog hardware circuits while maintaining detection speed.
Solution Approach 2:
The patent implements a feedback mechanism where the detected counter electromotive voltage is used to control the magnetic head speed. The system continuously monitors the voltage and adjusts the drive signals accordingly, creating a closed-loop control system that compensates for measurement errors and improves overall detection accuracy.
2Measurement precision
If analog-to-digital converter and CPU are used to detect counter electromotive voltage, then temperature-induced errors are reduced, but chip area increases
Solution Approach 1:
The patent integrates multiple functions into a single semiconductor chip, including the ADC, CPU, and counter electromotive voltage detection circuitry. This multi-functional integration allows the system to achieve high detection accuracy while minimizing the overall chip area by sharing common resources and infrastructure.
Solution Approach 2:
The patent combines the ADC, CPU, and detection circuits into a unified integrated circuit structure. By merging these components onto a single chip with shared power supply, grounding, and control signal lines, the system reduces the total area occupation compared to separate discrete components.
3Area of stationary object
If integration density is increased in semiconductor integrated circuit, then chip area is reduced, but manufacturing precision requirements increase
Solution Approach 1:
The patent employs parameter optimization techniques during the design and manufacturing process, adjusting parameters such as transistor dimensions, interconnect widths, and doping concentrations to achieve the required integration density while maintaining manufacturing precision within feasible limits.
Solution Approach 2:
The patent incorporates calibration and compensation mechanisms that are pre-configured during manufacturing. These preliminary actions include setting reference values and implementing error correction algorithms that compensate for manufacturing variations, allowing high integration density without requiring extremely tight manufacturing tolerances.
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 solution enables high-accuracy detection of counter electromotive voltage, enhancing the precision of magnetic head speed control and reducing the area occupied in semiconductor integrated circuits, thus improving the overall performance and efficiency of the motor drive control system.
Implementation Method 1
a counter electromotive voltage generated in the voice coil motor during the movement is detected and, based on the detected counter electromotive voltage, the speed of the magnetic head during the load operation is controlled
Data Source
AI summary
When a motor drive control device is integrated in a semiconductor integrated circuit having a small chip area, calibration for improving the accuracy of detection of a counter electromotive voltage, which is for detecting the speed of a motor, is enabled. A first multiplier performs multiplication between a drive current detection signal and first gain information in a first register. A subtractor performs subtraction between a drive voltage command signal and a first multiplication result in the first multiplier. A second multiplier performs multiplication between a subtraction result in the subtractor and second gain information in a second register to generate counter electromotive voltage information as information on a second multiplication result. The drive voltage command signal in a control unit is set to a predetermined value to generate a condition which maintains the speed of the motor and a counter electromotive voltage at substantially zero.