Back EMF Detector Circuit Gain Adjustment for HDD Speed Detection
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing semiconductor integrated circuits for hard disk drive units require external CPU digital correction for accurate back electromotive force (EMF) detection, which is inefficient and prone to errors due to temperature changes affecting parasitic resistance ratios, especially during loading and unloading operations.
Innovation Solution
A semiconductor integrated circuit with an internal adjustment unit that adjusts the gain of the back EMF detector circuit to maintain a compensation condition by setting non-zero currents through the motor during calibration, allowing for accurate speed detection without external CPU correction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If external CPU digital correction is used for back EMF detection, then measurement precision is improved, but device complexity increases and reliability decreases due to temperature-induced resistance ratio changes
Solution Approach 1:
The patent replaces the external CPU digital correction system with an internal analog gain adjustment mechanism. The back EMF detector circuit's gain is automatically adjusted by an adjustment unit based on temperature or operating conditions, eliminating the need for digital processing and external correction algorithms while maintaining detection precision across varying temperatures.
Solution Approach 2:
The back EMF detector circuit performs self-correction through internal gain adjustment. The adjustment unit automatically modifies the circuit's gain based on detected temperature or resistance ratio changes, enabling the system to compensate for its own errors without external intervention, thereby improving reliability under temperature variations.
2Measurement precision
If external CPU correction is implemented, then measurement precision improves, but ease of operation deteriorates due to required digital processing
Solution Approach 1:
The patent replaces complex digital processing operations with a simple analog gain adjustment mechanism. The adjustment unit automatically modifies the back EMF detector's gain based on temperature or resistance ratio, eliminating the need for external CPU intervention and digital correction algorithms, thereby simplifying operation while maintaining precision.
3Device complexity
If analog gain adjustment is implemented internally, then device complexity decreases, but manufacturing precision requirements increase
Solution Approach 1:
The patent adjusts the gain parameter of the back EMF detector circuit based on temperature or resistance ratio changes. The adjustment unit dynamically modifies electrical parameters (gain) to compensate for manufacturing variations and temperature effects, reducing the impact of manufacturing precision limitations while maintaining overall system performance.
4Measurement precision
If calibration operation with non-zero current is performed, then measurement precision improves, but use of energy increases during calibration
Solution Approach 1:
The patent performs calibration operations during manufacturing or initial setup to establish accurate gain values stored in memory. This preliminary calibration ensures high measurement precision during normal operation without requiring continuous energy-intensive calibration, as the stored calibration data is reused during regular back EMF detection.
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 calibration of the back EMF detection, maintaining linearity and preventing errors during loading and unloading operations by internally adjusting the gain to compensate for temperature-induced resistance ratio changes, thus eliminating the need for external digital correction.
Implementation Method 1
detecting a back electromotive force generated in the voice coil motor at the time of the movement
Implementation Method 2
compensate an error involved in the detection value of the back electromotive force which arises from the change of the parasitic resistance of the VCM (VCM resistance) due to a temperature change
Data Source
AI summary
The present invention realizes a calibration operation for detecting a motor speed, without employing digital correcting by an external CPU. The calibration operation calculates a comparison reference value corresponding to aback EMF detection signal of a back EMF detector circuit when a zero current flows through a motor and when an arm is fixed. Accordingly, the back EMF detection signal of the back EMF detector circuit is set as the first value and the second value responding to the non-zero current flowing through the motor, and the semiconductor integrated circuit calculates the comparison reference value from the first value and the second value. The difference between the comparison reference value and the comparison input value as the back EMF detection signal of the back EMF detector circuit is reduced by adjusting the gain of an internal amplifier of the back EMF detector circuit by an adjustment unit.