Actuator Driving Circuit Using Segmented Linear and PWM Control
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Solution Overview
Problem
Existing driving schemes for voice coil motors (VCMs) face challenges in balancing power consumption and accuracy, with linear schemes consuming more power but having higher output current accuracy, while PWM schemes have lower accuracy and generate noise due to current ripple, especially in low current regions.
Innovation Solution
The apparatus employs a control circuit that generates both current source and PWM signals to drive high-side and low-side switches, respectively, using feedback signals to optimize voltage levels and duty cycles, ensuring efficient power management and reduced noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If linear scheme is used to drive VCM, then output current accuracy is improved, but power consumption increases
Solution Approach 1:
The patent divides the driving scheme into two segments: high-side switch operates in linear mode for accuracy, low-side switch operates in PWM mode for power efficiency. This segmentation allows each switch to perform its optimal function, resolving the contradiction between accuracy and power consumption.
Solution Approach 2:
Different driving modes are applied to different parts of the system: the high-side switch uses linear driving with feedback control for high accuracy, while the low-side switch uses PWM for low power consumption. This local differentiation of quality resolves the contradiction by optimizing each component's operation mode according to its specific requirements.
2Use of energy by moving object
If PWM scheme is used to drive VCM, then power consumption is reduced, but output current accuracy deteriorates due to current ripple
Solution Approach 1:
The patent segments the PWM operation to apply it only to the low-side switch while keeping the high-side switch in linear mode. This segmentation allows power consumption reduction through PWM without sacrificing overall current accuracy, as the linear-mode high-side switch compensates for PWM-induced ripples.
Solution Approach 2:
The patent implements feedback control where the output current is monitored and used to adjust the high-side switch's linear driving. This feedback mechanism compensates for current ripples introduced by the low-side switch's PWM operation, maintaining accuracy while benefiting from reduced power consumption.
3Use of energy by moving object
If PWM scheme is used to drive VCM, then power consumption is reduced, but noise is generated due to switching on/off
Solution Approach 1:
The patent segments the switching operations so that the high-side switch operates in continuous linear mode without switching, eliminating noise from its operation. The low-side switch performs PWM switching for power efficiency, but the overall noise is reduced compared to full PWM operation.
4Measurement precision
If linear scheme is used to drive VCM, then output current accuracy is maintained, but device complexity increases due to feedback control requirements
Solution Approach 1:
The patent segments the feedback control requirements: full feedback control is applied to the high-side switch for accuracy, while the low-side switch uses simpler PWM control. This segmentation reduces overall control circuit complexity compared to implementing feedback control on both switches.
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 approach reduces power consumption and noise, maintaining high accuracy by minimizing discontinuous current mode non-linearity in low current regions, achieving a balance between linear and PWM driving schemes.
Implementation Method 1
a driving coil configured to generate magnetic force depending on driving signals
Implementation Method 2
the control circuit is further configured to control the driving circuit so that the high-side switch is operated as a current source using the first control signal
Implementation Method 3
the control circuit is further configured to control the driving circuit so that the low-side switch is driven in a pulse width modulation (PWM) scheme using the second control signal
Data Source
AI summary
An apparatus for driving an actuator includes a driving coil configured to generate magnetic force depending on driving signals, a control circuit configured to provide a first control signal and a second control signal, and a driving circuit including a high-side switch and a low-side switch connected to the driving coil, the high-side switch and the low-side switch configured to generate the driving signals based on the first and second control signals, respectively, and to provide the driving signals to the driving coil, wherein the control circuit is further configured to control the driving circuit so that the high-side switch is operated as a current source using the first control signal, and to control the driving circuit so that the low-side switch is driven in a pulse width modulation (PWM) scheme using the second control signal.