Voltage Detecting Device Leak Current Compensation
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Solution Overview
Problem
High-precision voltage detection in battery systems is compromised by leak currents due to the operation of delta-sigma type A/D converters, which cause significant detection errors, and existing compensating circuits may fail, leading to erroneous operations.
Innovation Solution
A voltage detecting device with a differential voltage detecting circuit, a leak canceling circuit, and a failure diagnosing part that controls and diagnoses the leak canceling circuit to accurately compensate for leak currents and detect voltage deviations, ensuring precise voltage detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a delta-sigma type A/D converter is used for high-precision voltage detection, then measurement precision is improved, but leak current causes detection error
Solution Approach 1:
The patent converts the harmful leak current into a useful signal by using it to charge a capacitor. The capacitor voltage, which reflects the leak current magnitude, is then used to generate a compensating current that cancels out the original leak current, thereby transforming the harmful effect into a beneficial compensation mechanism
Solution Approach 2:
The patent introduces a capacitor as an intermediary element between the leak current source and the compensation circuit. This capacitor serves as a mediator that stores the leak current information and enables the generation of the compensating current without directly connecting the harmful leak current to the detection circuit
2Measurement precision
If a low-pass filter with high resistance resistor is used at the input stage, then measurement precision is improved, but voltage drop due to leak current causes detection error
Solution Approach 1:
The patent converts the energy loss in the form of voltage drop across the resistor into a useful compensating signal. By using the leak current that causes the voltage drop to charge a capacitor, the system generates a compensating current that offsets the original voltage drop, transforming the energy loss into a beneficial correction
3Measurement precision
If leak canceling circuit is added to compensate for leak current, then detection precision is improved, but system complexity increases
Solution Approach 1:
The patent merges the leak current compensation function with the existing voltage detection circuit by sharing common components such as the capacitor and operational amplifier. The compensation circuit is integrated into the detection path, allowing both functions to be performed by a unified circuit structure rather than separate independent circuits
Solution Approach 2:
The patent designs the compensation circuit to perform multiple functions: it compensates for leak current, maintains detection precision, and provides failure diagnosis capability. The same circuit components serve multiple purposes, reducing the need for additional dedicated components and simplifying the overall system
4Reliability
If failure diagnosis function is added to monitor leak canceling circuit, then reliability is improved, but device complexity increases
Solution Approach 1:
The patent implements a self-diagnosis mechanism where the system automatically monitors its own compensation circuit functionality. The failure diagnosis function uses the existing circuit components and signals to detect abnormalities in the leak current compensation, allowing the system to self-verify its operational status without requiring external monitoring equipment
Solution Approach 2:
The patent integrates the failure diagnosis function into the existing voltage detection and compensation circuitry. The same operational amplifier and capacitor used for compensation also serve the diagnosis function by providing signals that indicate the health status of the compensation circuit, eliminating the need for separate dedicated diagnosis components
Data Source
AI summary
A voltage detecting device detects a differential voltage between two input nodes having a non-zero common mode voltage. A differential voltage detecting circuit 5 detects the differential voltage by sampling each voltage of the input nodes and outputs a detection voltage indicating a detection result. A leak canceling circuit generates a compensating current, which flows in opposition to a leak current flowing out from the input nodes in correspondence to an operation of the differential voltage detecting circuit. An operation control part controls the leak canceling circuit to perform or stop a canceling operation. A failure diagnosing part performs a failure diagnosis about the leak canceling circuit based on a first detection value and a second detection value of the detection voltages, which are detected during periods when the leak canceling circuit performs and stops the canceling operation.