Battery Protection Circuit Floating Ground Switching
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Solution Overview
Problem
Conventional battery protection circuits for embedded batteries in mobile devices face issues due to an electrically floating ground terminal when switching from an external power source to an embedded battery, leading to potential failure in recognizing control signals and maintaining accurate charge and discharge protection, especially with the limitations of PMOS transistors in providing low on-resistance for fast charging.
Innovation Solution
A signal processing circuit with a first circuit coupled between a power terminal and a first ground terminal and a second circuit coupled between the power terminal and a second ground terminal, utilizing NMOS transistors to maintain control signal magnitude and interpret high or low voltages correctly, ensuring proper connection or disconnection of the embedded battery, and incorporating a logic circuit to manage the switch device between the ground terminals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If PMOS transistors are used in the battery protection circuit, then the circuit can provide charge and discharge protection, but the on-resistance is high which limits fast charging capability
Solution Approach 1:
The patent changes the transistor type from PMOS to NMOS, fundamentally altering the electrical parameters of the switching device. NMOS transistors provide lower on-resistance compared to PMOS, enabling fast charging while maintaining protection functionality. This parameter change resolves the contradiction by selecting a transistor type that inherently provides both low resistance and adequate protection capability.
2Power
If NMOS transistors are used to provide low on-resistance for fast charging, then fast charging capability is improved, but the control signal recognition fails due to floating ground terminal
Solution Approach 1:
The patent introduces a ground switching device as an intermediary component that actively manages the connection between the floating ground terminal and the reference ground. This intermediary ensures that control signals are properly referenced during switching operations, resolving the recognition failure issue while allowing NMOS transistors to provide low on-resistance for fast charging.
3Adaptability or versatility
If the ground terminal is disconnected during switching, then the battery can be isolated for external power supply, but the ground terminal becomes electrically floating causing control signal interpretation errors
Solution Approach 1:
The patent implements dynamic ground management where the ground switching device actively changes the grounding state based on operational requirements. During normal operation, the ground terminal is connected for stable control signals. During switching to external power, the ground terminal is dynamically disconnected and then reconnected through the ground switching device, ensuring proper signal reference is restored. This dynamic approach maintains adaptability while preventing information loss.
Data Source
AI summary
A signal processing circuit includes a first circuit coupled between a power terminal and a first ground terminal and a second circuit coupled between the power terminal and a second ground terminal. The signal processing circuit is configured to receive a first signal at a voltage level relative to the first ground terminal and, in response to the first signal, provide a second signal at a voltage level relative to the second ground terminal. The signal processing circuit can be used in a battery protection circuit for a mobile device having an embedded battery. The battery protection circuit is configured with two NMOS transistors to allow the cell phone circuit to switch between the embedded battery and an external power source.