PWM Sensor Interface Circuit for Low-Dissipation Multi-Input Sampling
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Solution Overview
Problem
Existing sensor interface circuits experience high dissipation, particularly for two-wire sensors, limiting the number of inputs they can process due to voltage differences between sensors and microcontrollers, which results in significant power consumption.
Innovation Solution
The implementation of a circuit with a duty cycle greater than 10% and preferably greater than 25%, featuring a capacitive impulse response in the inactive state, and an integrated circuit with conversion circuits that synchronize sampling instants with descending switching element control pulses to reduce power consumption by optimizing the duty cycle and switching frequency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a current limiter termination interface circuit is used to connect sensors with different supply voltage to a microcontroller, then signal compatibility is achieved, but power dissipation increases significantly
Solution Approach 1:
The patent applies periodic action by using pulse-width modulation (PWM) to periodically switch the current limiter termination on and off. The sensor output is sampled during specific windows within each PWM cycle, allowing the interface to achieve signal compatibility while dramatically reducing average power dissipation compared to continuous operation.
Solution Approach 2:
The patent implements dynamics by making the interface circuit's operational state variable rather than static. The current limiter termination dynamically switches between active and inactive states based on the PWM signal, allowing the system to adapt its power consumption level while maintaining signal integrity during active sampling periods.
2Productivity
If the number of sensor inputs in an interface circuit is increased, then processing capability improves, but power dissipation increases due to voltage difference
Solution Approach 1:
By implementing periodic sampling with PWM for each sensor input, the system can support multiple sensor inputs without proportionally increasing power dissipation. Each input is actively sampled only during its designated time window within the PWM cycle, allowing high productivity with reduced energy loss compared to continuous monitoring of all inputs.
Solution Approach 2:
The patent applies segmentation by dividing the sampling process into discrete time segments or windows, with each sensor input being sampled during its specific time slot within the PWM cycle. This temporal segmentation allows multiple inputs to be processed sequentially rather than simultaneously, reducing the total power dissipation while maintaining the ability to handle many inputs.
3Measurement precision
If continuous monitoring of sensor signals is performed, then signal accuracy is maintained, but power consumption increases
Solution Approach 1:
The patent resolves this contradiction by implementing periodic sampling instead of continuous monitoring. The PWM-based approach samples sensor signals at specific intervals during active windows, maintaining sufficient measurement precision for the application while dramatically reducing power consumption compared to continuous analog monitoring of all sensor inputs.
Solution Approach 2:
The patent maintains continuity of useful action by ensuring that during each PWM cycle, the relevant sensor signals are sampled at the appropriate moments. This continuous periodic sampling ensures that no critical signal transitions are missed while avoiding the energy waste of continuous monitoring, as the system continuously cycles through sampling all inputs in sequence.
Data Source
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AI summary
The invention relates to a circuit for converting the state of a sensor (2i) into a signal interpretable by an electronic circuit, comprising: a comparator (32) of the voltage level of an input terminal (30i) with respect to a reference level (REF), the sensor being intended to be connected between a terminal for applying a first supply voltage (V1) and the input terminal; a current limiting element (34) between said input terminal and ground; and a switching element (40) in series with the current source and intended to be controlled by a pulse train.