Dual-Stage Error Amplifier Switching for Offset-Free Current Measurement
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Solution Overview
Problem
Error amplifier devices with intrinsic offset between inputs cause malfunctions in feedback or control loops, especially when used to supply a measurement current proportional to a power current, leading to inaccurate measurements due to inherent errors.
Innovation Solution
The implementation of an error amplifier device with two stages, each comprising an operational amplifier, calibration circuit, and switch control, which alternates between calibration and error amplification phases to compensate for input offsets, ensuring accurate measurement current proportional to the power current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional error amplifier device is used in a feedback or control loop, then the device can provide error amplification function, but the intrinsic offset between inputs causes measurement inaccuracy and control malfunction
Solution Approach 1:
The patent applies preliminary action by performing offset calibration before the error amplifier is used in its normal amplification function. The calibration phase pre-adjusts the input offset voltage to zero using a dedicated calibration circuit that generates compensating signals, ensuring that subsequent measurements and control operations are not affected by offset errors.
Solution Approach 2:
The patent implements feedback through an automatic calibration mechanism that continuously monitors and adjusts the input offset voltage. The calibration circuit receives feedback about the offset condition and automatically generates compensating signals to nullify the offset, maintaining measurement precision without requiring manual intervention.
2Measurement precision
If an error amplifier device with intrinsic offset is used to supply measurement current proportional to power current, then the amplification function is provided, but the inherent offset causes inaccurate measurement current
Solution Approach 1:
The patent segments the error amplifier device into two distinct operational phases: a calibration phase for offset compensation and a normal amplification phase for measurement current supply. This segmentation is achieved through phase control signals that switch the amplifier between calibration mode (where offset is nulled) and amplification mode (where measurement current is provided), allowing each function to be optimized independently.
Solution Approach 2:
The patent introduces a calibration circuit as an intermediary component that generates compensating signals to counteract the input offset voltage. This calibration circuit acts as a mediator between the offset error and the amplification function, automatically adjusting the offset without interfering with the normal measurement current supply operation.
3Measurement precision
If calibration circuit is added to compensate for input offset, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent merges the calibration function and amplification function into a single error amplifier device that operates in alternating phases. The same amplifier core is used for both offset calibration and measurement current amplification, with phase control signals switching between the two functions. This merging reduces the need for separate dedicated circuits and minimizes overall device complexity while maintaining measurement precision.
Solution Approach 2:
The error amplifier device is designed with multi-functionality, serving both as an offset calibration system and as a measurement current amplifier. The calibration circuit and amplification circuit share common components and operate sequentially under phase control, allowing one device to perform multiple functions without requiring entirely separate systems for each function.
Data Source
AI summary
The present disclosure relates to a device comprising two error amplifier stages having their first inputs interconnected, their second inputs interconnected and their outputs coupled to an output of the device, each stage comprising an operational amplifier; a circuit for calibrating the amplifier; a switch coupling an input of the amplifier to the first input; a switch coupling another input of the amplifier to the second input; a switch coupling an output of the amplifier to the stage output; a switch having on state which short-circuits the inputs of the amplifier; and a switch coupling the output of the amplifier to the calibration circuit.