Voltage Sensing Circuit Leakage Cancellation
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Solution Overview
Problem
Existing voltage sensing circuits face challenges in accurately sensing battery voltage due to leakage current errors caused by low-pass filters, leading to increased circuit area and consumption current when trying to compensate for these errors.
Innovation Solution
A voltage sensing circuit with a differential configuration that includes a difference voltage sensing circuit and a leakage cancelling circuit, using complementary switching of sensing capacitors and compensation capacitors to minimize leaked charge and reduce the compensation voltage, thereby reducing the circuit area and consumption current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a low-pass filter with high resistance value is used to sense battery voltage, then the voltage sensing accuracy is improved, but leakage current increases causing sensing error
Solution Approach 1:
The patent converts the harmful leakage current into a useful compensation signal. By detecting the voltage drop caused by leakage current across the high resistance value, the system generates a compensation current that flows in the opposite direction to cancel the leakage effect, thereby maintaining sensing accuracy without sacrificing the benefits of high resistance filtering.
Solution Approach 2:
The patent applies preliminary anti-action by pre-calculating and applying a compensation current before the leakage current causes significant sensing error. The compensation circuit proactively counteracts the expected leakage effect by generating an opposing current based on the known characteristics of the low-pass filter and sensing circuitry.
2Measurement precision
If a compensation circuit is provided to cancel leakage current, then sensing accuracy is improved, but circuit area and consumption current increase
Solution Approach 1:
The patent merges the compensation circuit functionality with the existing voltage sensing circuitry. The compensation current generation is integrated into the same operational amplifier and capacitor network used for voltage sensing, eliminating the need for separate compensation components and reducing overall circuit area while maintaining sensing accuracy.
3Measurement precision
If a compensation circuit is provided to cancel leakage current, then sensing accuracy is improved, but consumption current increases
Solution Approach 1:
The patent implements self-service by using the leakage current itself as the source for generating the compensation current. The operational amplifier detects the voltage drop caused by leakage and automatically generates the compensating current without requiring external power sources or additional active elements, thereby improving sensing accuracy while minimizing additional consumption current.
Data Source
AI summary
A voltage sensing circuit includes a difference voltage sensing circuit and a leakage cancelling circuit. The difference voltage sensing circuit includes two sensing capacitors, a first sensing switch, a second sensing switch, and a third sensing switch. A first group including the first sensing switch and the second sensing switch and a second group including the third sensing switch are complementally turned on and turned off. The leakage cancelling circuit includes two compensation capacitors, a first compensation switch, a second compensation switch, and a third compensation switch. A third group including the first compensation switch and the second compensation switch and a fourth group including the third compensation switch are complementally turned on and turned off.