Voltage Detection Circuit Using Modulated Current Injection
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Solution Overview
Problem
Existing voltage detection circuits face issues with decreased accuracy due to large amplitude pulse voltages causing offset voltages, leading to inaccurate disconnection detection in AD converters.
Innovation Solution
Incorporating a modulation signal generator, AD converter, current source, differentiator, multiplier, and integrator to detect disconnections by integrating fluctuating potential synchronized with a modulation signal, minimizing offset voltages through synchronized currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a frequency signal generation circuit generates a pulse voltage at a reference frequency to detect disconnection, then disconnection detection is enabled, but the large amplitude pulse voltage causes offset voltage increase leading to decreased voltage detection accuracy
Solution Approach 1:
The patent applies periodic action by using a modulation signal generator that outputs a periodic modulation signal to control the current source. The current source supplies current to the input terminal in synchronization with this periodic modulation signal, creating a periodic current injection pattern that enables disconnection detection without requiring large amplitude pulse voltages, thus avoiding offset voltage issues while maintaining detection reliability
Solution Approach 2:
The patent changes the parameter approach by transitioning from using large amplitude pulse voltages to using a modulation signal that varies current parameters over time. The modulation signal generator creates a time-varying current injection pattern that allows the AD converter to detect disconnection through integrated voltage fluctuations, thereby maintaining detection capability while improving voltage measurement accuracy by avoiding large offset voltages
2Reliability
If the input terminal of the AD converter is disconnected from the detection target device, then disconnection can be detected, but the potential at the input terminal fluctuates at the reference frequency causing detection errors
Solution Approach 1:
The patent implements feedback by using the output signal from the AD converter to feed back into the integration process. The integrated voltage signal from the AD converter output is fed back to the summing circuit, allowing the system to continuously monitor and adjust for fluctuations caused by disconnection, thereby maintaining measurement precision while enabling reliable disconnection detection through the feedback mechanism
Data Source
AI summary
A voltage detection circuit includes a modulation signal generator, an AD converter, a current source, a differentiator, a multiplier, and an integrator. The modulation signal generator generates a modulation signal. The AD converter converts a voltage applied between a first input wiring and a second input wiring into a digital value. The current source supplies a first current to the first input wiring and supplies a second current to the second input wiring. The first current changes based on the modulation signal, and the second current changes based on the modulation signal. The differentiator outputs a value acquired by differentiating an output value of the AD converter. The multiplier multiplies an output value of the differentiator by a value that varies positively and negatively according to the modulation signal. The integrator integrates an output value of the multiplier.