USB Charging State Control in Mobile Devices
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Solution Overview
Problem
Mobile electronic devices face challenges in supporting both USB charging state and suspend state functions, particularly due to insufficient current during the suspend state, which leads to improper battery charger enablement and non-compliance with USB specifications.
Innovation Solution
A method and apparatus that utilize a USB interface, a processing device, a battery charger, and a timing circuit to manage the charging state by generating enable signals based on enumeration acknowledgement and timing, ensuring compliance with USB specifications and efficient power management between charging and suspend states.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the battery charger is enabled during device suspend state to maintain power supply, then the device can operate continuously, but the current consumption exceeds the USB specification limit of 500 μA
Solution Approach 1:
The system dynamically adjusts the battery charger's operational state based on the device's power mode. During suspend state, the charger is disabled to meet USB current limits, while during active state, the charger is enabled to provide sufficient power for operation and battery recharging. This dynamic switching resolves the contradiction between continuous operation and current consumption limits.
Solution Approach 2:
The system uses the enumeration acknowledgement signal from the USB host to automatically determine whether to enable the battery charger. The device self-regulates its power consumption by interpreting the host's enumeration response, enabling the charger only when the host confirms it can provide sufficient current, thereby adhering to USB specifications while maintaining operational reliability.
2Use of energy by moving object
If the battery charger is disabled during device suspend state to comply with USB current limits, then current consumption is reduced, but the device cannot maintain operation
Solution Approach 1:
The system dynamically switches between suspend and active states based on power availability. When the battery charger is disabled during suspend state, the device enters a low-power mode that conserves energy. When the charger is enabled during active state, the device can operate reliably with sufficient current. This dynamic state management resolves the contradiction between current consumption and operational reliability.
Solution Approach 2:
The system automatically manages its own power state by monitoring the battery charger's enablement status. When the charger is disabled, the device self-regulates to suspend state to conserve energy. When the charger is enabled, the device self-activates to operational state. This self-service mechanism ensures the device maintains reliability while adhering to USB current limits.
3Speed
If the device initiates enumeration immediately upon VBUS detection to power up, then the device can start operation quickly, but the battery charger may be improperly enabled during suspend state
Solution Approach 1:
The system uses feedback from the enumeration acknowledgement signal to control the battery charger's enablement. Instead of immediately enabling the charger upon VBUS detection, the system waits for the host's enumeration response. This feedback mechanism ensures the charger is only enabled when the host confirms it can provide sufficient current, preventing improper enablement during suspend state while maintaining quick startup when conditions are appropriate.
Solution Approach 2:
The system performs preliminary enumeration communication with the USB host before enabling the battery charger. This preliminary action allows the device to confirm power availability and negotiate the appropriate charging state in advance, ensuring the charger is only enabled when proper conditions are met, thereby maintaining both startup speed and charging state reliability.
Data Source
AI summary
In accordance with the teachings described herein, a method and apparatus for handling a charging state in a mobile electronic device is provided. A universal serial bus (USB) interface may be used for connecting the mobile device to a USB host. A processing device may be used to execute programs and to control operation of the mobile device. The processing device may be operable to receive an enumeration acknowledgement signal from the USB host via the USB interface and generate an enable signal upon receiving the enumeration acknowledgement signal. A rechargeable battery may be used to power the processing device. A battery charger may be used to receive a USB bus voltage from the USB interface and use the USB bus voltage to power the processing device and to charge the rechargeable battery. The battery charger may be further operable to receive a charge enable signal that enables and disables the battery charger from powering the processing device and charging the rechargeable battery. A timing circuit may be used to detect the USB bus voltage and to measure the passage of a pre-determined amount of time upon detecting the USB bus voltage. A battery charger enabling circuit may be used to generate the charge enable signal to control the battery charger, the battery charger enabling the battery charger if the timer has measured the passage of the pre-determined amount of time or the enable signal is received from the processing device.