Switching Converter Low-Load Current Measurement by Clock Counting
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Solution Overview
Problem
Existing switching converters face challenges in accurately measuring small load currents, which are difficult to quantify using analog methods, especially in applications requiring high power efficiency like mobile devices.
Innovation Solution
An apparatus and method that includes a pulse generation circuit, a reference current generation circuit, and a clock generation circuit to generate a control pulse, reference current, and clock signal, respectively, with a counter to count cycles during the switching period, compensating for leakage currents to accurately measure load currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If analog measurement methods are used for load current, then the measurement process is simple, but measurement precision deteriorates for small load currents
Solution Approach 1:
The patent replaces the analog measurement system with a digital measurement system. Instead of using analog circuits to directly measure load current, the invention converts the current measurement into a digital counting operation by generating clock signals proportional to the load current and counting them over a switching period. This substitution of analog measurement with digital counting significantly improves measurement precision for small currents while managing circuit complexity through systematic design.
Solution Approach 2:
The patent changes the measurement parameter from direct analog current measurement to digital pulse counting. By converting the load current into a frequency-proportional clock signal and then counting the cycles, the system transforms a difficult-to-measure small current into a easily countable digital quantity, thereby improving measurement precision without excessive complexity increase.
2Measurement precision
If clock generation circuit is used to measure small load current, then measurement precision improves, but leakage current errors increase
Solution Approach 1:
The patent acknowledges the leakage current as an inevitable harmful factor in the clock generation circuit but converts it into a manageable parameter. By generating a compensation clock signal that accounts for the leakage current effects, the system transforms the harmful leakage into a correctable error source, thereby maintaining measurement precision and reliability simultaneously.
Solution Approach 2:
The patent implements a feedback mechanism where the actual clock signal generated (which includes leakage current effects) is used to create a compensation signal. This feedback approach allows the system to automatically adjust for leakage current variations, maintaining measurement accuracy despite the presence of leakage in the clock generation circuit.
Data Source
AI summary
An apparatus configured to measure a load current provided to a load of a switching converter includes a pulse generation circuit configured to generate a control pulse based on a power switch driving signal of the switching converter, a reference current generation circuit configured to generate a reference current based on the control pulse, a clock generation circuit configured to generate a clock signal based on the control pulse and the reference current, and a clock counter configured to count the number of cycles of the clock signal during a switching period of the switching converter. The reference current generation circuit is configured to adjust the reference current to compensate for a leakage current generated in the clock generation circuit during the switching period.