Differential Comparator Switching to Prevent DC Stress Offset
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Solution Overview
Problem
Conventional A/D converters with differential comparators experience stability deterioration and offset when subjected to long-term DC input, leading to inaccurate conversions and malfunctions due to DC stress fixation in the latch circuit.
Innovation Solution
A differential comparator design featuring complementary switch portions and latch circuits that periodically change output terminals, ensuring differential output signals are always output from the same terminals, preventing DC stress fixation and stability deterioration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of moving object
If a DC input is continuously inputted into an A/D converter including a differential comparator for a long time, then the latch circuit holds the output value, but stability deterioration occurs due to DC stress fixation
Solution Approach 1:
The patent implements periodic switching of the latch circuit's input/output terminals using switch portions. Instead of continuously holding the same output value, the circuit periodically exchanges the connection states of the latch terminals, causing the DC stress to alternate between different MOS transistors. This periodic action prevents any single transistor from being subjected to unidirectional DC stress for extended periods, thereby suppressing stability deterioration while maintaining continuous operation capability.
2Stability of the object's composition
If the latch circuit holds the output value for a long time, then the output is maintained, but offset occurs due to stability deterioration
Solution Approach 1:
The switch portions periodically exchange the input/output terminal connections of the latch circuit, causing the held output value to be maintained through alternating connection states rather than fixed unidirectional stress. This periodic switching maintains output stability while preventing offset by distributing DC stress alternately between complementary MOS transistors, thereby preserving measurement precision.
3Device complexity
If DC stress is fixed in one direction in the latch circuit, then the circuit operates simply, but stability deterioration and offset occur
Solution Approach 1:
The patent introduces dynamic switching elements (switch portions) that periodically change the connection states of the latch circuit terminals. This transforms the static DC stress condition into a dynamic alternating stress condition, where the stress direction changes periodically. The added dynamic element prevents stability deterioration while maintaining relatively simple circuit structure through systematic switching control.
Data Source
AI summary
In some examples, a differential comparator includes a differential amplifier configured to output differential output signals, a first switch portion configured to input the differential output signals from the differential amplifier and output the differential output signals from output terminals while alternatively changing over the output terminals, a latch portion configured to update and latch the differential output signals from the output terminals of the first switch portion, and a second switch portion configured to input output signals from the latch portion and output the latched output signals. The first switch portion and the second switch portion are changed over complementarily so that the differential output signals from the differential amplifier are always outputted from the same first and second output terminals of the second switch portion respectively.