Multi-Input ADC Sampling for Precise PWM-Triggered Measurements
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Solution Overview
Problem
Existing analog-to-digital converters (ADCs) are limited in capturing current and voltage measurements at precise times relative to pulse width modulation (PWM) signals, as they sequentially take samples following a trigger event, leading to timing inaccuracies in power supply applications with multiple PWM signals occurring at random times.
Innovation Solution
The implementation of a system with multiple sample and hold circuits and trigger selection circuits allows each analog input to be sampled and held until the ADC is ready to convert, ensuring precise timing alignment with PWM signals, using a combination of sample and hold circuits, analog multiplexers, and ADCs to manage multiple trigger sources and convert signals into digital values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If an ADC sequentially takes samples following a trigger event, then the ADC can convert analog signals to digital values, but the timing accuracy of measurements relative to PWM signals deteriorates
Solution Approach 1:
The system divides the ADC functionality into separate components: multiple independent sample and hold circuits (one for each analog input) and a shared ADC converter. Each sample and hold circuit operates independently to capture samples at precise trigger times, while the ADC sequentially converts them. This segmentation allows timing-accurate sampling without requiring multiple full ADC systems.
Solution Approach 2:
The sample and hold circuits perform preliminary sampling and holding of analog signals at the exact moment of trigger events, before the ADC conversion occurs. This preliminary action ensures that the timing relationship between PWM signals and measurements is captured accurately, while the ADC conversion can proceed sequentially without timing constraints.
2Adaptability or versatility
If multiple PWM signals occur at random times, then the system can control multiple power circuits, but the ADC cannot capture samples at the precise required times
Solution Approach 1:
The system uses a universal sample and hold architecture where each analog input has its own sample and hold circuit that can be independently triggered. This allows the system to handle multiple PWM signals at different times with different requirements, while maintaining precise timing for each measurement through dedicated trigger inputs for each sample and hold circuit.
3Productivity
If the ADC takes sequential samples after a trigger, then the conversion process can be completed, but the timing relationship with PWM signals becomes inaccurate
Solution Approach 1:
The system separates the sampling function from the conversion function. Multiple sample and hold circuits operate in parallel to capture samples at different times independently, preserving timing relationships. The ADC then converts these samples sequentially at its own pace without affecting the already-captured timing accuracy of each sample.
Data Source
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AI summary
An analog-to-digital conversion apparatus for converting a plurality of analog input signals may include a plurality of analog input, a plurality of sample and hold circuits, one or more analog-to-digital converters (ADCs), a plurality of trigger selection circuits, and one or more analog multiplexers. The analog inputs may receive an analog input signals. The sample and hold circuits may include an input selectively coupled to at least one of the plurality of input and an output. The analog-to-digital converters (ADCs) may include an input and an output. The trigger selection circuits may selectively couple one of the inputs to one of the sample and hold circuits. The analog multiplexers may include a plurality of inputs selectively coupled to one or more of the sample and hold circuit outputs and an output coupled to one of the one or more analog-to-digital-converters.