Switching Converter Load Current Sensing with Adaptive Pulse Extension
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Solution Overview
Problem
Switching converters face challenges in accurately measuring load current over a wide range, which is crucial for estimating power consumption and preventing overheating, especially in mobile applications where load current variability is significant.
Innovation Solution
The apparatus and method employ time extension circuitry, logic circuitry, switch circuitry, and a load current meter to generate and filter signals based on the on-time of power switches and reference voltages, allowing for precise measurement of load current by switching between modes based on current thresholds, thereby extending pulse width in low-load conditions for higher resolution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a fixed measurement method is used for load current, then the measurement is simple, but the measurement precision deteriorates when load current varies widely
Solution Approach 1:
The measurement system dynamically switches between two measurement modes based on the load current magnitude. When load current is high, the system uses a first measurement method; when load current is low, it switches to a second measurement method with extended pulse width. This dynamic adaptation resolves the contradiction by optimizing measurement precision for each operating condition without requiring a completely separate system for each scenario.
Solution Approach 2:
The system changes the pulse width parameter based on the measurement mode. In the second mode for low load current, the pulse width is extended to improve measurement resolution. This parameter change allows the system to maintain high measurement precision across different load current ranges while using a single integrated measurement device.
2Measurement precision
If the pulse width is extended for low load current measurement, then the measurement resolution improves, but the measurement time increases
Solution Approach 1:
The system dynamically adjusts pulse width based on load current magnitude. For high load current, a shorter pulse width is used, reducing measurement time. For low load current, the pulse width is extended to improve resolution. This dynamic adjustment resolves the contradiction by applying extended measurement time only when necessary for low-current accuracy, rather than always using the longer pulse width.
Solution Approach 2:
The measurement system operates in periodic switching cycles, alternating between first and second modes based on load current conditions. This periodic switching allows the system to use extended pulse widths intermittently only when low-load measurement is required, minimizing overall measurement time while maintaining high resolution when needed.
3Measurement precision
If mode switching is implemented for different load ranges, then measurement accuracy across wide range improves, but control complexity increases
Solution Approach 1:
The measurement range is segmented into two distinct regions: high load current range and low load current range. Each region has a dedicated measurement method optimized for its characteristics. This segmentation simplifies the control logic by creating clear boundaries and decision criteria for mode switching, making the control system more manageable despite the multi-mode operation.
Solution Approach 2:
The system uses feedback from the measured load current to automatically determine which measurement mode to employ. The measured current value is compared against a threshold, and the mode is automatically switched accordingly. This feedback mechanism simplifies control complexity by using the measurement data itself to guide the mode selection, rather than requiring external complex control logic.
Data Source
AI summary
A method of measuring a load current provided to a load of a switching converter includes obtaining a first reference voltage defining a peak of an inductor current passing through an inductor of the switching converter, generating a pulse based on the first reference voltage and an on-time of at least one power switch of the switching converter, generating an output signal by filtering the pulse, and setting a second mode from a first mode when a value of the load current is less than a first threshold value based on the output signal. The generating of the pulse further includes generating the pulse having a width extended in proportion to the on-time in the second mode.