Sample-and-Hold Charger Current Sensing in Discontinuous Conduction
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Solution Overview
Problem
Existing technologies fail to effectively monitor and determine current in discontinuous conduction mode (DCM) in battery charging circuits, particularly in uninterruptible power supply (UPS), a battery charging circuit shares a converter with a booster circuit, and the current shape varies substantially, making it difficult to monitor and estimate the current used for battery charging.
Innovation Solution
A current monitoring system using a sample-and-hold circuit to generate a signal corresponding to the peak current, combined with two ADC channels and a controller to determine average current in both continuous and discontinuous conduction modes, utilizing additional properties like duty cycle and peak value to calculate average current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single ADC channel is used to monitor current, then the device complexity is reduced, but the measurement precision deteriorates because it cannot accurately capture current in both continuous and discontinuous conduction modes
Solution Approach 1:
The current monitoring function is segmented into two distinct ADC channels: a first ADC channel dedicated to sampling the S/H signal for DCM operation, and a second ADC channel for sampling the current signal in CCM operation. This segmentation allows each channel to be optimized for its specific conduction mode, improving measurement precision without requiring a single complex channel to handle both modes
Solution Approach 2:
The controller is designed with multi-functionality to determine average current using different methods based on the operating mode. It can switch between using the first ADC channel with S/H signal for DCM and the second ADC channel for CCM, making the system universally applicable to both conduction modes while maintaining measurement accuracy
2Measurement precision
If traditional current sampling is used without sample-and-hold circuit, then the device complexity is reduced, but the measurement precision deteriorates in discontinuous conduction mode where current peaks are unpredictable
Solution Approach 1:
The sample-and-hold circuit performs preliminary action by capturing and holding the peak current value before the ADC sampling occurs. This ensures that the peak current is preserved and ready for accurate measurement, addressing the issue of unpredictable current peak positions in DCM without requiring complex real-time tracking algorithms
Solution Approach 2:
The S/H circuit acts as an intermediary between the unpredictable current signal and the ADC sampler. It transforms the transient peak current into a stable held voltage signal that can be accurately sampled and processed, mediating the mismatch between the discontinuous current characteristics and the periodic ADC sampling
3Adaptability or versatility
If the charging circuit operates in discontinuous conduction mode, then the adaptability is improved for light load conditions, but the measurement precision deteriorates because current monitoring becomes difficult with discontinuous current shape
Solution Approach 1:
The monitoring system applies local quality by using different measurement approaches for different conduction modes. The first ADC channel with S/H signal is specifically optimized for DCM local conditions, while the second ADC channel is optimized for CCM local conditions, allowing accurate measurement in each specific operating regime
Solution Approach 2:
The system dynamically adapts its measurement method based on the conduction mode. The controller determines whether the circuit is in DCM or CCM and switches between using the first ADC channel (for DCM) or the second ADC channel (for CCM), enabling accurate current monitoring across varying load conditions
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables accurate monitoring of current in battery charging circuits, even in discontinuous conduction mode, by using a sample-and-hold technique with multiple ADC channels and a controller to calculate average current, improving control precision.
Implementation Method 1
a S/H circuit (sample-and-hold circuit) configured to generate a S/H signal, wherein the S/H signal corresponds to a peak value of current in the charging circuit within a switching period of the charging circuit
Data Source
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AI summary
A current monitoring system may include a sample-and-hold circuit to generate a sample-and-hold signal (S/H signal), where the S/H signal corresponds to a peak value of current in a charging circuit within a switching period of the charging circuit. The system may further include a first analog-to-digital channel (ADC channel) to sample the S/H signal and a second ADC channel configured to sample the current in the charging circuit. The system may then determine an average current of the charging circuit based on the first ADC channel when the charging circuit is operating in a discontinuous conduction mode, and determine the average current of the charging circuit based on the second ADC channel when the charging circuit is operating in a continuous conduction mode.