Battery Charger Architecture with Segmented Power Path Switch
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Solution Overview
Problem
Existing battery chargers for Li-ion batteries often require a system voltage significantly higher than the final charge voltage to ensure sufficient headroom for linear regulator operation, leading to unnecessary power wastage and reduced efficiency.
Innovation Solution
A battery charger architecture that includes a segmented power path switch and advanced control circuitry to minimize voltage drops and current overshoots, allowing the system voltage to be set exactly to the final charge voltage, reducing unnecessary power consumption and extending battery life by isolating the battery from the system load when an external power source is available.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a higher system voltage is used to ensure sufficient headroom for linear regulator operation, then the regulator can operate reliably, but power wastage increases and efficiency decreases
Solution Approach 1:
The patent implements dynamic voltage adjustment where the system voltage is not fixed but adapts based on charging conditions. The voltage is raised above the final charge voltage only when needed for regulator headroom during charging operations, and lowered when not needed to reduce power consumption. This dynamic adjustment resolves the contradiction by making the voltage level conditional rather than static.
Solution Approach 2:
The patent changes the system voltage parameter dynamically during operation. Specifically, it adjusts the voltage to be higher than the final charge voltage when charging is active to ensure regulator headroom, and lowers it when charging is complete or not active. This parameter change allows the system to maintain reliability during charging while reducing energy loss during other states.
2Power
If the system voltage is set significantly higher than the final charge voltage, then sufficient headroom is available for regulator operation, but the efficiency of the charging system decreases
Solution Approach 1:
The system dynamically adjusts voltage based on operational state. During charging, the voltage is maintained higher to provide necessary headroom for the linear regulator. After charging completes or when not actively charging, the voltage is reduced to minimize power consumption. This dynamic behavior ensures sufficient power headroom when needed while maintaining high charging efficiency by avoiding continuous high voltage operation.
3Adaptability or versatility
If the battery remains connected to the system load, then the battery can power the system when external power is unavailable, but the battery discharges unnecessarily when external power is available
Solution Approach 1:
The patent implements preliminary action by proactively isolating the battery from the system load using a power path switch when external power is detected to be available. This prevents the battery from discharging unnecessarily while external power is supplying the system. The isolation action is taken in advance before any significant discharge can occur, preserving battery life while maintaining system operability.
Solution Approach 2:
The patent extracts the battery from the power path when external power is available by using a power path switch to isolate them. This separation allows the external power to directly supply the system load without drawing current from the battery. The battery is taken out of the active power path but remains available as a backup, resolving the contradiction between flexibility and battery life preservation.
Data Source
AI summary
A control circuit for use in a battery charger circuit that includes a switching voltage regulator, with the control circuit having a constant current charging mode and a constant voltage charging mode. A switcher controller is provided which configured to control a state of a top side switching transistor and a low side transistor of the switching voltage regulator in response to at least one error signal. A power path transistor switch is disposed intermediate an output of the switching voltage regulator and a first node for receiving a first terminal of a battery to be charged. Feedback circuitry is further provided to produce a first error signal relating to a difference between a first voltage and a first target voltage, with the first voltage being between the output of the switching voltage regulator and a second node for receiving a second terminal of the battery to be charged, with the first error signal being used by the switcher controller when the control circuit is in the constant voltage charging mode for controlling the top and low side switching transistors.