Switching Regulator Current Limiting via Peak Sampling
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Solution Overview
Problem
Existing switching regulators face challenges in accurately limiting output current due to propagation delays in current sensing, leading to errors and increased power dissipation, especially as maximum current specifications increase.
Innovation Solution
An electronically implemented method and apparatus for current limiting in switching regulators, which involves sampling the inductor current relative to the switching of a transistor, adjusting the current limit threshold based on comparisons, and limiting the output current using a current limiting comparator and adjustment circuit, while minimizing propagation delays and quiescent current consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If larger devices are used to provide and sense higher currents, then maximum current capability is improved, but device size and power dissipation increase
Solution Approach 1:
The patent performs current sampling at a predetermined timing relative to the switching cycle, before the full current waveform is established. By sampling at this optimized moment and using a hold circuit to maintain the sampled value, the system achieves accurate current measurement without requiring continuously high-power sensing components, thereby reducing overall power dissipation while maintaining measurement precision.
2Measurement precision
If current limit threshold is dynamically adjusted based on sampled current, then current limiting accuracy is improved, but circuit complexity increases
Solution Approach 1:
The patent implements a feedback mechanism where the sampled current value is compared with a reference level, and the current limit threshold is dynamically adjusted based on this comparison. The hold circuit maintains the sampled value for continuous comparison, creating a closed-loop system that improves current limiting accuracy while using simple, integrated circuit elements rather than complex external components.
3Speed
If propagation delay in current sensing is reduced, then current limiting response time is improved, but measurement accuracy may deteriorate
Solution Approach 1:
The patent performs current sampling at a predetermined timing relative to the switching cycle, capturing the current value at an optimal moment before propagation delays affect the measurement. The hold circuit then maintains this pre-captured value, allowing the system to respond quickly to current conditions without sacrificing measurement accuracy, thus resolving the trade-off between response time and accuracy.
Data Source
AI summary
In one aspect, this disclosure relates to a method of controlling current output from a switching regulator to a load via an inductor. Inductor current information can be sampled at a peak level, such as just before a transistor configured to cause current to flow through the inductor is turned off. The sampled inductor current can be compared with a reference current, and a current limit threshold can be adjusted based on the comparison. The output current of the switching regulator can be controlled based on a comparison of the current limit threshold with an indicator of current flowing through the inductor. This method can accurately and efficiently limit current in a switching regulator.