Flash Driver Voltage Droop Control for Handheld Devices
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Solution Overview
Problem
Handheld electronic devices with flash capabilities often experience battery droop due to high current draws from the LED camera flash, leading to potential device resets or shutdowns, as existing methods rely on worst-case assumptions that limit flash usage and do not accurately estimate sustainable flash current.
Innovation Solution
A method that determines the battery temperature and calculates multiple voltage droops for various current loads, setting minimum voltage thresholds to adjust flash current dynamically, ensuring the battery voltage remains above the threshold during flash operation, thereby preventing resets and optimizing flash performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the flash draws high current for a long period to provide sufficient light output, then the illumination intensity is improved, but the battery voltage drops causing device resets or shutdowns
Solution Approach 1:
The flash driver dynamically adjusts the flash current based on real-time battery voltage monitoring. The system transitions from static worst-case assumptions to dynamic adaptive control, where the flash current is continuously modified according to actual battery conditions to prevent voltage droop while maximizing light output.
Solution Approach 2:
The system implements feedback control by monitoring battery voltage during flash operation and using this information to adjust the flash current. The feedback loop detects when voltage approaches dangerous levels and reduces current accordingly, creating a closed-loop control system that prevents device resets while maintaining optimal flash performance.
2Reliability
If the system uses worst-case assumptions to prevent battery droop, then the device reliability is improved, but the flash functionality is limited and productivity decreases
Solution Approach 1:
The system performs self-assessment of battery conditions through continuous voltage monitoring and ESR calculation. Rather than relying on conservative pre-calculated limits, the system independently evaluates actual battery state during operation and adjusts flash parameters accordingly, enabling more aggressive flash usage when battery conditions permit.
Solution Approach 2:
The system changes the operational parameters of the flash based on real-time battery condition assessment. By calculating actual ESR and monitoring voltage droop, the system dynamically modifies flash current, pulse width, and other parameters to optimize performance for each specific battery state, rather than using fixed conservative limits.
3Illumination intensity
If the battery voltage is allowed to drop to minimum levels, then the flash current can be increased for better illumination, but the device may reset or go into sleep mode
Solution Approach 1:
The system performs preliminary assessment of battery conditions before initiating flash operation. By calculating ESR and predicting voltage droop in advance, the system pre-determines safe flash parameters that will not cause voltage to drop below dangerous levels, preventing resets before they can occur.
Solution Approach 2:
The system builds a cushion of safety margin by continuously monitoring voltage and ESR, and by designing the flash control to operate with sufficient headroom above minimum voltage thresholds. This beforehand cushioning approach ensures that even under varying conditions, the voltage remains safely above reset thresholds while still allowing optimal flash performance.
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 allows for more accurate estimation of sustainable flash current, reducing the likelihood of device resets and enhancing flash functionality by dynamically adjusting the flash current based on real-time battery conditions, ensuring reliable operation without assuming worst-case scenarios.
Implementation Method 1
a battery having a voltage and a current flowing therefrom
Implementation Method 2
handheld electronic devices include a camera and a light emitting diode (LED) camera flash
Data Source
AI summary
A handheld electronic device includes a processor; a battery; a flash device; a number of loads powered by the battery; and a flash driver outputting a flash current to the flash device. The processor determines a temperature operatively associated with the battery and different voltage values corresponding to different combinations of the loads as a function of the determined temperature, and starts the flash device at a predetermined flash current value. The flash driver selects a corresponding different voltage value as a function of: (a) a determined number of the loads which are active, or (b) a current flowing from the battery; determines the battery voltage, and if the battery voltage is less than or equal to the corresponding different voltage value, reduces the flash current below the predetermined flash current value until the battery voltage is greater than the corresponding different voltage value.