A/D Converter Sequencer Input Switching
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Solution Overview
Problem
Existing A/D converters, operational amplifiers, and back electromotive force monitoring circuits face limitations in processing speed, circuit scale reduction, and linearity of offset adjustment, as well as accuracy in monitoring back electromotive force.
Innovation Solution
The proposed solutions include an A/D converter with a sequencer that performs input switching without waiting for A/D conversion completion, an operational amplifier with an offset current generator for precise offset adjustment, and a back electromotive force monitoring circuit that generates a speed detection voltage by biasing the back electromotive force with a reference voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the sequencer waits for A/D conversion completion before performing input switching, then the A/D conversion processing can be completed accurately, but the processing speed decreases
Solution Approach 1:
The sequencer performs input switching processing in advance on completion of sample hold processing, rather than waiting for the entire A/D conversion to complete. This preliminary action allows the next input signal to be ready before the current conversion finishes, eliminating idle waiting time and improving processing speed
2Device complexity
If the operational amplifier uses a conventional offset adjustment method, then the circuit can be implemented, but the circuit scale is large and linearity of offset adjustment is poor
Solution Approach 1:
The patent changes the parameter domain from voltage-based offset adjustment to current-based offset adjustment. By using offset currents that are added to input currents in a current summing node, the circuit achieves better linearity and reduced complexity compared to conventional voltage adjustment methods
3Measurement precision
If the back electromotive force monitoring circuit directly monitors the back electromotive force, then the monitoring can be performed, but the accuracy is insufficient
Solution Approach 1:
The patent introduces a speed detection voltage as an intermediary parameter. Instead of directly monitoring the back electromotive force, the circuit generates a speed detection voltage based on motor speed, which then serves as the basis for generating motor control signals. This intermediary approach improves monitoring accuracy while keeping the circuit structure manageable
Data Source
AI summary
An A/D converter has an analog multiplexer stage which selects one of a plurality of first analog signals as a second analog signal, an amplifier stage which amplifies the second analog signal to generate a third analog signal, an A/D conversion stage which converts the third analog signal into a digital signal, and a sequencer which controls those stages. The sequencer performs input switching processing in the analog multiplexer stage on completion of sample hold processing by the A/D conversion stage, when performing a plurality of times of A/D conversion processing sequentially, without waiting for completion of the A/D conversion processing.