Switching Power Supply Battery Current Estimation
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Solution Overview
Problem
Direct measurement of battery current in battery-powered devices with switching power supplies is problematic due to the need for series elements, which add losses and complexity, making it challenging to estimate instantaneous and average battery currents effectively.
Innovation Solution
The solution involves estimating battery current based on switching power supply current by mirroring the current and using control circuitry to limit the battery current within acceptable thresholds, employing buck and boost switching power supply configurations to provide regulated output signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If direct current measurements are implemented to measure battery current, then measurement precision is improved, but device complexity increases due to the need for series elements
Solution Approach 1:
The patent uses an intermediary approach by measuring the voltage across a known resistance element (shunt resistor) in series with the battery, rather than measuring current directly. The current is derived indirectly through Ohm's Law (I = V/R), where the voltage measurement across the shunt resistor provides the battery current information without requiring complex direct current measurement circuitry
Solution Approach 2:
The patent replaces direct mechanical/electrical current measurement with a voltage measurement system. By substituting the direct current sensing mechanism with a voltage sensing mechanism across a known resistance, the system achieves current measurement precision while avoiding the complexity of direct current measurement circuits
2Measurement precision
If series elements are added for direct current measurement, then measurement precision is improved, but energy loss increases
Solution Approach 1:
The patent changes the measurement parameter from direct current to voltage across a shunt resistor. By measuring voltage instead of current directly, and using a low-value shunt resistor, the system minimizes power loss (P = I²R) while maintaining measurement precision through accurate voltage sensing
Solution Approach 2:
The patent employs a low-value shunt resistor that introduces minimal power loss into the system. This sacrificial resistance element is designed to have such low value that its power dissipation is negligible compared to the overall system power consumption, yet it provides sufficient voltage signal for accurate current measurement
3Device complexity
If battery current is not monitored, then device complexity is reduced, but reliability decreases due to inability to prevent maximum current exceedance
Solution Approach 1:
The patent implements a feedback mechanism where the measured battery current (derived from shunt voltage) is continuously monitored and fed back to the control system. This feedback enables the switching power supply to adjust its operation to prevent the battery current from exceeding maximum ratings, thereby ensuring reliability without requiring complex monitoring systems
Solution Approach 2:
The patent enables the power supply system to self-regulate battery current through integrated control circuitry that uses the shunt resistor measurements to automatically adjust switching duty cycle and prevent over-current conditions. The system serves itself by incorporating the measurement and control functions within the existing power supply architecture, adding minimal complexity while ensuring battery protection
Data Source
AI summary
The present invention relates to estimating a battery current supplied from a battery to a switching power supply, which provides a regulated output signal to a load, based on a switching power supply current in the switching power supply, and then controlling the regulated output signal to limit the battery current to within an acceptable threshold. The switching power supply current may be provided by one or more switching elements in the switching power supply. The switching elements may be mirrored to provide a mirrored switching power supply current, which is used to estimate the battery current. The estimated battery current may include an estimated average battery current, an estimated instantaneous battery current, or both.