Power Dissipation Control for Battery Charging Pass Devices
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Solution Overview
Problem
Existing charging systems face safety concerns due to excessive power dissipation by pass devices when used with third-party adapters, leading to potential damage or reduced lifespan, and current solutions like fuses or temperature shutdown circuits increase costs and are not economically viable for integrated power management.
Innovation Solution
A control apparatus that regulates power dissipation by using a controller with sensing circuits to monitor and control the charging current and power dissipation, employing a combination of NMOS and PMOS FETs to limit current and power, ensuring safe operation within predetermined thresholds, thereby preventing excessive power dissipation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a fuse is provided to protect the pass device, then the pass device is protected from excessive power dissipation, but the cost of the electronic device increases and the charging system cannot be reused once the fuse is disabled
Solution Approach 1:
The charging system performs self-protection through the controller monitoring power dissipation and automatically adjusting the drive current to keep the pass device within safe operating limits, eliminating the need for external protective devices like fuses
Solution Approach 2:
The controller continuously monitors the power dissipation of the pass device and uses feedback control to adjust the drive current, creating a closed-loop protection system that prevents excessive power dissipation without requiring additional protective components
2Reliability
If a temperature shutdown circuit is provided to protect the pass device, then the pass device is protected from thermal damage, but the cost of the electronic device increases and additional internal power dissipation occurs
Solution Approach 1:
The controller proactively limits the drive current to prevent the pass device from reaching dangerous temperature levels, rather than reacting after thermal damage has occurred. This preliminary action eliminates the need for temperature shutdown circuits
Solution Approach 2:
The patent replaces thermal protection mechanisms (temperature shutdown circuits, thermal sensors) with electrical control mechanisms (controller-based current limiting), eliminating the need for additional power dissipation and complex thermal management hardware
3Power
If higher power rated pass devices are used to cope with excessive power dissipation, then the pass device can handle higher power, but the physical package size increases and the cost of the electronic device increases
Solution Approach 1:
The system dynamically adjusts the drive current based on real-time power dissipation conditions, allowing a lower power rated pass device to safely handle variable power loads. The controller modulates the current to keep the pass device within its safe operating area, eliminating the need for oversized passive components
4Reliability
If OEM adapters with low regulated output voltages are used, then the charging system is protected from excessive power dissipation, but connection flexibility is reduced and the cost of the electronic device increases
Solution Approach 1:
The charging system performs self-protection by monitoring its own power dissipation and automatically limiting current when necessary, eliminating the need for proprietary adapters with restricted output specifications. This allows compatibility with third-party adapters while maintaining safety
Solution Approach 2:
The controller uses feedback from power dissipation sensing to dynamically adjust operating parameters, enabling safe operation with various adapter types and voltages. This feedback mechanism replaces the need for pre-configured low-voltage OEM adapters
Data Source
AI summary
In the field of battery charging for electronic devices, it is known to employ a number of measures to avoid excessive power dissipation by a pass device in a charging system. However, many of these measures are either incompatible with linear charging regimes or add cost to the adapter and/or charging system. The present invention provides a power dissipation measurement circuit for controlling a control device that acts in series with another, but maximum current limiting, control device to control drive current to the pass device so as to limit the power dissipated by the pass device to a maximum threshold value.