Variable Voltage VCM Driver for OIS Thermal Management
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Solution Overview
Problem
Conventional VCM drivers in portable camera devices, such as smartphones and tablets, generate excessive heat due to high power consumption, especially during low output current conditions, leading to undesirable thermal conditions affecting nearby heat-sensitive components.
Innovation Solution
The power supply input voltage of the VCM driver is varied based on the expected level of activity of the OIS actuator, with higher voltage during high activity and lower voltage during low activity, and continuously adjusted as a function of the camera's operating mode and user context, using a variable voltage regulator and sensor data.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the power supply input voltage is kept fixed at a high level to enable maximum output current capability, then the driver can source maximum current during demanding modes, but excessive heat is generated during low output current conditions
Solution Approach 1:
The power supply input voltage to the VCM driver is dynamically adjusted based on the expected activity level of the OIS actuator. The processor varies the voltage between a first level (enabling maximum current) and a second level (reducing heat during low activity), thereby making the power supply adaptive rather than static. This resolves the contradiction by allowing the system to have high power capability when needed while minimizing heat generation during normal operation.
Solution Approach 2:
The invention changes the voltage parameter of the power supply input to the VCM driver based on operating conditions. By switching between two voltage levels (first voltage level for high performance, second voltage level for low power), the system adapts its electrical parameters to match the actual demand, thus reducing unnecessary power dissipation and heat generation during low-activity periods while maintaining the capability to deliver maximum current when required.
2Temperature
If the power supply input voltage is lowered to reduce heat generation during low output current, then power efficiency improves, but the driver cannot source maximum output current when needed
Solution Approach 1:
The system dynamically switches the power supply voltage level based on real-time assessment of OIS actuator activity. When low activity is detected, the voltage is reduced to minimize heat; when high activity is anticipated (such as during video capture with vibration), the voltage is raised to enable maximum current output. This dynamic adaptation resolves the contradiction by ensuring the driver has sufficient power capability exactly when needed while minimizing thermal issues during normal operation.
Solution Approach 2:
The processor determines the expected activity level of the OIS actuator in advance and adjusts the power supply voltage accordingly before the high-current demand occurs. This preliminary adjustment ensures that when maximum output current is needed, the driver is already powered at the appropriate voltage level to deliver it, thus maintaining performance capability while optimizing power efficiency during intervening low-activity periods.
3Power
If the driver is designed for high performance to handle video capture mode with strong vibration, then maximum output current can be sourced, but the driver generates excessive heat during preview and still capture modes
Solution Approach 1:
The power supply voltage to the VCM driver is made dynamic rather than fixed, adjusting according to the camera operation mode and expected OIS activity. During preview and still capture modes with low OIS activity, the voltage is reduced to minimize power consumption. During video capture mode with strong vibration where high OIS activity is expected, the voltage is increased to enable maximum output current. This dynamic power management resolves the contradiction between high performance capability and low power consumption during normal operation.
Solution Approach 2:
The invention changes the voltage parameter of the power supply based on the camera operation mode. By switching between a first voltage level (for high performance during video capture) and a second voltage level (for low power during preview/still capture), the system adapts its electrical characteristics to match the actual operational requirements, thus eliminating unnecessary power consumption during low-activity modes while maintaining the capability to deliver high current when needed.
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 heat generation and improves power efficiency, minimizing thermal issues in tightly packaged portable devices by maintaining a low voltage headroom during low output current conditions, thereby enhancing the performance and longevity of the camera device.
Implementation Method 1
The actuator contains a voice coil motor (VCM) that is driven by a VCM driver (circuit)
Data Source
AI summary
In a portable camera device, a variable voltage regulator produces a power supply voltage of a VCM driver circuit that conducts the coil current of a VCM actuator as part of an optical image stabilization (OIS) mechanism. A processor signals the variable voltage regulator to increase the power supply voltage when the camera device transitions from still capture mode or preview mode to video capture mode, where the increase causes an increase in stroke of the VCM OIS actuator. Other embodiments are also described and claimed.