Battery-Powered LED Driver Efficiency via Charge Pump Bypass
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Solution Overview
Problem
Power management in battery-powered devices like cellular telephones faces inefficiencies due to the limited operational time caused by voltage variations, which are exacerbated by the use of boost regulators and Pulse Width Modulation (PWM) techniques that require higher voltages and currents, leading to reduced battery life.
Innovation Solution
A charge pump system that bypasses the charge pump when battery voltage is sufficient to directly drive LEDs, engaging the charge pump only when the voltage drops below a threshold, combined with a multi-stage drive system using PWM and linear modes to optimize efficiency, allowing for higher efficiency levels of 90-97%.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If boost regulators are used to maintain LED illumination levels, then illumination consistency is improved, but power efficiency deteriorates (50-80% efficiency)
Solution Approach 1:
The patent segments the voltage regulation function into two distinct operational modes: a direct drive mode for high battery voltage and a charge pump mode for low battery voltage. This segmentation allows each mode to operate in its optimal efficiency range, avoiding the continuous energy loss inherent in traditional boost regulators.
Solution Approach 2:
The patent implements dynamic switching between two voltage drive approaches based on real-time battery voltage conditions. The system transitions from direct battery voltage drive to charge pump assisted drive when battery voltage drops below a threshold, optimizing power efficiency across the entire battery discharge cycle while maintaining consistent LED illumination.
2Adaptability or versatility
If PWM technique is used to control LED intensity, then variable intensity control is improved, but voltage and current requirements worsen (higher voltages and currents needed)
Solution Approach 1:
The patent applies partial action by using PWM only during the high battery voltage phase when direct drive is sufficient. During low voltage phases, the system switches to charge pump assisted direct drive, reducing the excessive voltage requirements of PWM while maintaining intensity control capability through duty cycle adjustment.
Solution Approach 2:
The patent changes the operating parameters dynamically by switching between PWM mode and charge pump assisted direct drive mode based on battery voltage levels. This parameter change allows the system to maintain LED intensity control while reducing peak voltage and current requirements during the battery discharge cycle.
3Loss of energy
If systems operate without boost regulators, then power efficiency is improved, but battery operational time worsens (limited operational time)
Solution Approach 1:
The patent implements preliminary action by proactively switching to charge pump assisted drive before the battery voltage becomes too low to operate LEDs. This preliminary intervention extends the usable battery voltage range, allowing the system to maintain efficient operation longer without requiring a full boost regulator throughout the entire discharge cycle.
Solution Approach 2:
The patent uses dynamic voltage threshold detection to switch between operational modes at optimal points in the battery discharge cycle. This dynamic approach maximizes the high-efficiency direct drive period while using charge pump assistance only when necessary, thereby extending overall battery operational time compared to static boost regulator approaches.
4Power
If charge pump is used to increase voltage, then voltage sufficiency is improved, but efficiency deteriorates compared to direct drive
Solution Approach 1:
The patent segments the voltage boosting function into a dedicated charge pump component that operates only when necessary. By separating the voltage elevation function from the continuous operation and activating it only during low battery voltage conditions, the system minimizes the cumulative energy loss while ensuring voltage sufficiency when needed.
Solution Approach 2:
The patent implements periodic activation of the charge pump based on battery voltage threshold crossings. Rather than continuous operation, the charge pump is activated periodically when voltage drops below the threshold and deactivated when voltage recovers, reducing overall energy loss while maintaining voltage sufficiency during critical periods.
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 significantly improves power efficiency by doubling LED driving circuit efficiency when the charge pump is bypassed and prolongs battery operation by minimizing the use of inefficient charge pumps, while maintaining desired illumination intensity.
Implementation Method 1
A charge pump, and a switch that bypasses the charge pump when battery output voltage is sufficient to directly drive an LED load
Data Source
AI summary
An apparatus and method is provided for optimizing LED driver efficiency. The present invention offers low cost solutions for powering LEDs while minimizing overall power dissipation in devices powered by a depletable power source. Low system cost is attained using a charge pump to increase LED drive voltage level and implementing combinations of drive techniques to overcome the inefficiency of the charge pump. A switch bypasses the charge pump when depletable power source output voltage is sufficient to directly drive an LED load. At certain output voltage levels, the switch can be opened causing the charge pump to boost drive voltage. The output voltage may also be PWM modulated to drive the LED load and, at some voltages, the depletable power source may drive the LED load directly. Efficiency levels of 90-97% are attainable.