Programmable Flash Current Drive for Battery Brownout Prevention
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Solution Overview
Problem
Handheld electronic devices with LED camera flashes often experience system brownouts due to high current draw, leading to impaired operation or device resets, as the existing methods rely on worst-case assumptions rather than accurate measurements of sustainable flash current.
Innovation Solution
A method using a programmable current drive and microprocessor to measure and calculate the maximum sustainable flash current by accounting for battery voltage, temperature, and system loads, allowing for precise adjustment of flash current to prevent brownouts and ensure device stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If worst-case assumptions are used to avoid brownout, then system reliability is improved, but flash usability is severely limited
Solution Approach 1:
The system continuously monitors battery voltage during flash operation and uses this feedback to dynamically adjust the flash current in real-time. The microprocessor reads the battery voltage at multiple points during the flash cycle and modifies the current drive accordingly, allowing the system to adapt to actual battery conditions rather than relying on worst-case assumptions. This feedback mechanism enables the system to maximize flash performance while preventing brownout by responding to actual voltage drops.
Solution Approach 2:
The flash current is made dynamic rather than fixed. The system adjusts the current drive level during the flash operation based on real-time battery voltage measurements. The microprocessor modifies the current setpoint during the flash cycle to account for voltage drops, temperature changes, and other system conditions. This dynamic adjustment allows the system to optimize flash performance for each specific operating condition rather than using a static conservative current level.
2Illumination intensity
If flash current is increased to improve illumination, then illumination intensity is improved, but battery voltage drops causing brownout
Solution Approach 1:
The system performs periodic measurements of battery voltage during the flash operation and adjusts the current drive between these measurement points. The microprocessor reads the battery voltage at multiple discrete points during the flash cycle (such as at 10% and 90% through the flash duration) and uses this information to modulate the current drive. This periodic sampling and adjustment allows the system to maintain high illumination while preventing voltage drops that would cause brownout.
Solution Approach 2:
The system changes the electrical parameters of the flash operation dynamically. The microprocessor adjusts the current drive level, flash duration, and other parameters based on real-time monitoring of battery voltage, temperature, and system load conditions. By modifying these parameters during operation rather than using fixed values, the system optimizes illumination intensity while maintaining system stability under varying battery and environmental conditions.
3Measurement precision
If battery voltage is monitored continuously to adjust flash current, then flash current accuracy is improved, but device complexity increases
Solution Approach 1:
The existing microprocessor and voltage measurement infrastructure in the device is utilized for multiple purposes. The same hardware components that handle general device control and power management are also employed for monitoring battery voltage during flash operation and adjusting current drive. By making the existing components multi-functional rather than adding dedicated dedicated measurement and control circuitry, the system achieves precise flash current control without proportionally increasing device complexity.
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 and adjustment of flash current, reducing the likelihood of device resets and maintaining system functionality under varying conditions without relying on worst-case assumptions, thereby enhancing the usability of LED flashes in handheld devices.
Implementation Method 1
an LED camera flash capability has been added to a number of mobile phones
Implementation Method 2
powered by a single lithium ion battery
Data Source
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.