Poly-phase Energy Meter Using Shared ADCs to Reduce Die Space
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Solution Overview
Problem
Existing poly-phase electric energy meters require either large and expensive high-resolution ADCs for synchronous processing or complex phase adjustments in sequential processing, which are inefficient in terms of space and cost.
Innovation Solution
A poly-phase electric energy meter design using two shared ADCs with synchronous multiplexers and de-multiplexers, eliminating the need for phase adjustments between current and voltage samples by ensuring synchronized digital sampling across all phases.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If separate input channels with ADCs are used for each current and voltage input signal, then high accuracy is achieved, but die space and cost increase
Solution Approach 1:
The patent combines multiple input signals (three current signals and three voltage signals) into two shared ADC channels. The first ADC channel processes all current input signals through a multiplexer, while the second ADC channel processes all voltage input signals through a multiplexer. This merging approach maintains high measurement accuracy while significantly reducing the number of ADCs required from six to two, thereby reducing die space and cost.
Solution Approach 2:
Each ADC channel is designed to be universal and multi-functional, handling multiple different input signals. The first ADC channel universally processes Ia, Ib, and Ic current signals by sequentially switching them through the multiplexer. Similarly, the second ADC channel universally processes Va, Vb, and Vc voltage signals. This multi-functionality allows a single ADC channel to replace what would traditionally require multiple dedicated ADC channels.
2Area of stationary object
If a single high-resolution ADC with multiplexer is used, then die space is reduced, but phase adjustment complexity increases
Solution Approach 1:
The patent segments the input signals into two distinct groups: current signals (Ia, Ib, Ic) and voltage signals (Va, Vb, Vc). Each group is assigned to a separate ADC channel with its own multiplexer. This segmentation allows synchronous sampling of both groups, eliminating the need for complex phase adjustments that would be required if all signals were multiplexed through a single ADC channel.
Solution Approach 2:
The multiplexers in both ADC channels operate synchronously with periodic switching, ensuring that current and voltage samples are obtained at the same time instants. This periodic synchronous action maintains the temporal relationship between current and voltage samples, eliminating phase adjustment requirements while still achieving die space reduction through shared ADC resources.
3Area of stationary object
If sequential sampling with single ADC is used, then die space is reduced, but phase correction requirements increase
Solution Approach 1:
The patent merges the sampling operations of multiple signals into two synchronized ADC channels. By combining all current signals into one channel and all voltage signals into another channel, both operating synchronously, the system achieves die space reduction similar to sequential sampling but without the phase correction complexity, as both channels sample at the same time instants.
Data Source
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AI summary
A poly-phase electric energy meter comprises a front-end (12) that converts analog current input signals and analog voltage input signals to digital current and voltage samples and a micro-controller for computing power consumed. The front end includes first and second input channels. Each input channel has a multiplexer, an analog-digital converter, a demultiplexer and a set of data registers. The first input channel receives current input and the second input channel receives voltage inputs. A multiplexer control causes the first and second channels to sequentially sample the current and voltage for one phase at a time and store digital data in corresponding data registers. The micro-controller computes energy consumed from the simultaneous current and voltage samples.