Linear Resonant Actuator Drive Without Zero-Crossing Noise
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Solution Overview
Problem
Existing natural frequency (F0) tracking technologies in linear resonant actuators cause high audio noise, reduce average drive signal amplitude, and require additional circuits or compensation due to zero-crossing windowing, leading to increased chip cost and reliability issues.
Innovation Solution
A linear resonant actuator driving apparatus that calculates back electromotive force using voltage and current to adjust drive waveform frequency and amplitude in real-time, avoiding zero-crossing interruptions and enabling precise control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If zero-crossing windowing is used to detect back electromotive force, then natural frequency tracking is achieved, but additional harmonic components are caused resulting in high audio noise
Solution Approach 1:
The patent applies preliminary action by pre-charging the capacitor to a voltage equal to the supply voltage before the zero-crossing detection period. This preparatory charging ensures that when the drive circuit is turned off for zero-crossing detection, the capacitor maintains sufficient voltage level, preventing the need to extend the zero-crossing window duration. Consequently, back electromotive force detection can be completed within a standard time window without causing additional harmonic components, thereby eliminating audio noise while maintaining natural frequency tracking precision.
2Measurement precision
If zero-crossing windowing time is increased to improve detection accuracy, then natural frequency tracking precision is improved, but the final average drive signal amplitude decreases
Solution Approach 1:
The patent applies preliminary action by pre-charging the capacitor to a voltage equal to the supply voltage before the zero-crossing detection period. This preparatory charging ensures that when the drive circuit is turned off for zero-crossing detection, the capacitor maintains sufficient voltage level, allowing detection to be completed within a standard time window without extending the duration. Consequently, the drive signal amplitude is preserved while achieving accurate natural frequency tracking.
3Measurement precision
If zero-crossing windowing is used for back electromotive force detection, then natural frequency tracking is achieved, but parasitic diode conduction occurs affecting detection accuracy
Solution Approach 1:
The patent applies preliminary action by pre-charging the capacitor to a voltage equal to the supply voltage before the zero-crossing detection period. This ensures that during the brief zero-crossing detection window, the capacitor maintains sufficient voltage to prevent the output transistor's parasitic diode from conducting. By maintaining this pre-charged state, the detection can be completed within the standard time window without extending duration, thereby preventing parasitic diode conduction and ensuring reliable back electromotive force detection.
4Measurement precision
If zero-crossing detection is implemented, then natural frequency tracking is achieved, but additional discharge circuits or increased device spacing are required increasing chip cost
Solution Approach 1:
The patent applies preliminary action by pre-charging the capacitor to a voltage equal to the supply voltage before the zero-crossing detection period. This ensures that during the standard-duration zero-crossing detection window, the capacitor maintains sufficient voltage to prevent parasitic diode conduction. By preventing diode conduction through this preliminary charging action, the patent eliminates the need for additional discharge circuits or increased device spacing, thereby reducing chip structure complexity and cost while maintaining accurate natural frequency tracking.
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
Achieves higher precision and faster control of linear resonant actuators by detecting back electromotive force continuously, maintaining optimal amplitude and frequency without stopping the drive circuit, thus reducing noise and chip costs.
Implementation Method 1
The drive is provided by an LRA driver chip. The driver chip applies an excitation current to the coil, generating a magnetic field that pushes the magnetic oscillator to move in a certain direction.
Implementation Method 2
detect the back electromotive force generated by the movement of the LRA oscillator
Data Source
AI summary
A linear resonant actuator driving apparatus and method. An input end of an electromotive force calculation module is connected to a detection module, an output end of the electromotive force calculation module is connected to an input end of a phase calculation module, an input end of a signal processing module is connected to an output end of the phase calculation module, an input end of an amplitude calculation module is connected to the output end of the electromotive force calculation module, an output end of the amplitude calculation module is connected to the input end of the signal processing module, an input end of the drive circuit is connected to an output end of the signal processing module, and an output end of a drive circuit is connected to an actuator.