Flash Current Control via Battery ESR Measurement
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Solution Overview
Problem
Handheld electronic devices with LED camera flashes powered by a single lithium ion battery often experience voltage drops (brown out) due to high current demand, leading to impaired system functions or resets, as the existing methods rely on worst-case assumptions rather than accurate measurements, limiting the flash's usefulness.
Innovation Solution
A method using a programmable current drive within a microprocessor to measure and calculate the maximum sustainable flash current by accounting for battery resistance, system loads, and environmental factors, allowing for real-time adjustments to maintain stable voltage during flash events.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If worst-case voltage drop assumptions are used to avoid brown out, then system reliability is improved, but flash usability deteriorates
Solution Approach 1:
The system performs real-time measurements of battery voltage, current, and temperature during flash operation, using this feedback to dynamically adjust flash current and predict sustainable flash duration. This replaces static worst-case assumptions with adaptive real-time monitoring, allowing the system to maximize flash usability while preventing brown out through continuous adjustment rather than conservative limiting.
Solution Approach 2:
The system changes multiple parameters including flash current, pulse width, and duty cycle based on real-time battery state measurements. By dynamically adjusting these parameters rather than using fixed worst-case limits, the system optimizes flash performance under varying battery conditions, resolving the contradiction between reliability and usability.
2Measurement precision
If real-time battery measurement and calculation is implemented, then flash current prediction accuracy is improved, but device complexity increases
Solution Approach 1:
The existing microprocessor and battery management circuitry are made multi-functional by using them for both normal device operation and flash current prediction. Rather than adding dedicated measurement hardware, the system leverages existing components to perform real-time battery characterization, reducing the complexity increase while achieving high prediction accuracy.
Solution Approach 2:
The system uses its own existing sensors and processing capabilities to perform self-diagnosis and real-time battery state assessment. The microprocessor utilizes available ADC channels and existing control logic to measure battery parameters and calculate sustainable flash current, eliminating the need for separate dedicated measurement systems.
3Stability of the object's composition
If flash current is reduced to avoid brown out, then system stability is improved, but flash performance deteriorates
Solution Approach 1:
The system transitions from static flash current limiting to dynamic real-time adjustment. Flash current is continuously modified based on measured battery voltage, current draw, and temperature during operation. This dynamic approach allows the system to maintain stability by adjusting current in real-time while maximizing flash performance when battery conditions permit, rather than using fixed conservative limits.
Solution Approach 2:
The system performs periodic measurements of battery state during flash operation and adjusts flash parameters accordingly. By continuously monitoring and periodically updating flash current based on real-time battery characteristics, the system maintains stability while optimizing performance, replacing static current reduction with adaptive periodic adjustment.
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 enables more accurate prediction and adjustment of flash current, reducing the likelihood of system resets and ensuring consistent flash operation without relying on worst-case assumptions, thus enhancing the device's usability under varying conditions.
Implementation Method 1
a camera capability has been added to many mobile phones and is likely to expand to other such handheld electronic devices. More recently, an LED camera flash capability has been added to a number of mobile phones that, along with the other mobile phone capabilities, is powered by a single lithium ion battery.
Implementation Method 2
The current drawn from operating an LED (light emitting diode) camera flash is enormous and can easily brown out the system under certain conditions. A lithium ion battery's ability to maintain its voltage is dependent upon such factors as the age of the battery and temperature; i.e., the equivalent series of resistance (ESR) of the battery varies with these parameters.
Implementation Method 3
an LED camera flash capability has been added to a number of mobile phones
Implementation Method 4
The current drawn from operating an LED (light emitting diode) camera flash is enormous
Data Source
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AI summary
A method and apparatus for maintaining a maximum sustained flash current over the whole length of a flash using a programmable current drive in a handheld portable device powered by a battery. The method involves measuring the battery voltage before and after a flash is initiated and calculating the equivalent series resistance (ESR) of the battery. The calculated ESR is then used to adjust the flash current. The process may be repeated to correct for errors in the flash current.