Dual Feedback Loop for Precision High-Voltage Drift Control
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Solution Overview
Problem
High-voltage power supplies for instruments like mass spectrometers and electron microscopes face challenges in achieving precise output voltage due to noise and drift introduced by components in their feedback control loops, degrading instrument performance.
Innovation Solution
A dual feedback loop system is implemented, combining analog and digital feedback loops to improve precision, where an error amplifier receives a measurement signal and a DAC output signal to produce a control signal, and an ADC converts the measurement signal for digital processing, allowing the digital processor to calculate adjustments for the output voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a feedback control loop is implemented to achieve precise output voltage, then output voltage precision is improved, but noise and drift are introduced by components in the feedback loop
Solution Approach 1:
The feedback loop is segmented into two independent loops: an analog feedback loop for high-frequency noise reduction and a digital feedback loop for low-frequency drift correction. Each loop handles specific frequency ranges, allowing the system to achieve high precision without the noise and drift problems of a single unified loop.
Solution Approach 2:
A digital signal processor acts as an intermediary between the analog feedback components and the final output control. The DSP converts analog signals to digital, processes them through algorithms that eliminate noise and drift, then converts back to control the output, thereby mediating the harmful effects of analog components.
2Measurement precision
If multiple components are used in the feedback control loop to achieve precision, then output voltage precision is improved, but device complexity increases
Solution Approach 1:
The digital signal processor performs multiple functions: it converts analog-to-digital, implements feedback control algorithms, filters noise, corrects drift, and generates control signals. This multi-functionality reduces the need for separate dedicated components for each function, simplifying the overall device while maintaining high precision.
Solution Approach 2:
The patent replaces traditional analog mechanical/electrical feedback components with a digital processing system. Instead of using multiple analog components (op-amps, filters, regulators), the system uses digital algorithms running on a DSP to achieve the same control functions with fewer physical components.
Data Source
AI summary
A high-voltage (HV) power supply outputs an output voltage based on a control signal produced by a dual analog/digital feedback loop. The control signal is determined at least in part by an error amplifier that receives a measurement signal, proportionally attenuated from the output voltage, and a digital-to-analog converter (DAC) output signal. An analog-to-digital converter (ADC) also receives the measurement signal and transmits it in digitized form to a digital processor. The digital processor calculates a digital DAC data signal based on the measurement signal, and on a digital set-point input signal corresponding to a set-point voltage value of the output voltage desired to be outputted from the high-voltage source. A DAC receives the DAC data signal and converts it to the DAC output signal transmitted to the error amplifier.