Voice Coil Motor Control for DC Offset and Coil Temperature
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Solution Overview
Problem
Conventional voice coil motor control systems face challenges in preventing coil damage due to DC offset-induced temperature rises, as existing threshold settings can lead to either frequent false stops or prolonged high temperatures, affecting vibration quality.
Innovation Solution
A motor control device that detects DC offsets and ambient temperatures, adjusts the drive voltage by setting temperature correction values, and controls vibration levels to prevent coil damage while maintaining appropriate vibration, using a sinusoidal waveform with reversed phase and integrated temperature detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the operation stop threshold is set low to detect DC offset early, then coil damage is prevented, but false stops occur frequently due to noise during normal operation
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the operation stop threshold based on the detected ambient temperature. As temperature increases, the threshold is raised to accommodate thermal noise, preventing false stops while still protecting against actual DC offset conditions that could cause coil damage
2Productivity
If the operation stop threshold is set high to avoid false stops, then operation continuity is maintained, but coil temperature rises excessively before threshold is reached
Solution Approach 1:
The patent dynamically changes the operation stop threshold parameter based on ambient temperature detection. When ambient temperature is high, the threshold is increased to maintain operation continuity. When ambient temperature is low, the threshold is lowered to prevent excessive coil temperature rise, thus resolving the contradiction between operation continuity and temperature control
3Ease of operation
If drive voltage is increased with temperature rise to maintain vibration output, then vibration level is maintained, but coil temperature rises more rapidly
Solution Approach 1:
The patent implements feedback control by continuously monitoring ambient temperature and using this information to adjust the operation stop threshold. This feedback mechanism allows the system to maintain appropriate protection levels while accounting for temperature-dependent variations in motor characteristics, preventing the need for excessive drive voltage increases
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 effectively prevents coil damage by stopping drive voltage application when DC offsets exceed thresholds and adjusts drive voltage based on temperature corrections, ensuring consistent vibration levels despite temperature changes.
Implementation Method 1
a tactile feedback technology in which an operation site is vibrated using a voice coil motor (VCM) or the like has been known
Implementation Method 2
DC offset detection means that detects a DC offset of the drive voltage
Implementation Method 3
ambient temperature detection means that detects an ambient temperature
Implementation Method 4
a DC current flows through the coil due to the DC offset, and a temperature rises. When the temperature rise becomes excessive, a coating film of the coil melts, leading to smoking and burning
Data Source
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AI summary
A motor control device (100) capable of securing an appropriate vibration amount while preventing burning of a coil due to a DC offset of a drive voltage is provided. The motor control device (100) includes: a waveform generation unit (110) and an amplifier (120) that generate a drive voltage of a voice coil motor (VCM) (200); a DC offset detection unit (130) that detects a DC offset of the drive voltage; a stop control unit (152) that stops application of the drive voltage to a motor coil (210) when the detected DC offset exceeds an operation stop threshold; a temperature correction value setting unit (154) that sets a temperature correction value corresponding to the DC offset when the detected DC offset is lower than the operation stop threshold; a thermistor (140) that detects an ambient temperature; and a vibration level control unit (156) that varies the drive voltage and controls an amplitude level based on the detected ambient temperature and the set temperature correction value.