Capacitance Measurement Circuit Using Voltage Threshold Detection
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing energy storage devices with capacitors as backup power supplies face challenges in accurately determining capacitance degradation, leading to insufficient power supply during voltage drops due to errors in measuring high voltages, which affects the determination of characteristic degradation and the reliability of backup power systems.
Innovation Solution
An energy storage device incorporating a charging circuit, first and second comparators, and a control circuit that calculates capacitance based on the period and voltage change width between predetermined voltages, using a voltage-dividing circuit to reduce high voltages to manageable levels for the comparators, allowing for accurate determination of capacitance and characteristic degradation without the need for high-precision A/D converters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a general A/D converter with 10-bit resolution is used to measure high voltage (50V) in the energy storage device, then the device complexity is reduced and cost is lowered, but the measurement precision deteriorates due to large capture errors (±245 mV) that make capacitance determination inaccurate
Solution Approach 1:
The high voltage measurement range is segmented into multiple discrete voltage levels (first predetermined voltage Vc1 and second predetermined voltage Vc2). Instead of attempting to measure the entire high voltage range with high precision, the invention divides the measurement into discrete segments using comparators that detect when voltage reaches specific threshold levels, thereby achieving accurate capacitance measurement without requiring high-precision A/D conversion across the full voltage range.
Solution Approach 2:
The invention changes the measurement parameter from continuous voltage magnitude measurement to discrete voltage level transition detection. By monitoring the time it takes for voltage to transition between predetermined levels during constant current charging, the system achieves accurate capacitance determination using low-precision comparators rather than high-precision voltage measurement, thus resolving the contradiction between device simplicity and measurement accuracy.
2Measurement precision
If an oscilloscope-based measuring instrument is built into the energy storage device to achieve high capacitance measurement accuracy, then the measurement precision improves, but the device complexity and cost increase significantly making it unrealistic for backup power supply applications
Solution Approach 1:
The invention extracts only the essential measurement function needed for capacitance determination from a full oscilloscope system. Instead of implementing a complete oscilloscope with display and analysis capabilities, the patent isolates and implements only the voltage detection and timing measurement functions using simple comparators and control circuitry, thereby achieving adequate measurement precision without the excessive complexity of a full oscilloscope.
Solution Approach 2:
The invention creates a simplified functional copy of the oscilloscope's measurement capability. Rather than implementing the full oscilloscope hardware, the system replicates the essential measurement function by using comparators to detect voltage levels and a control circuit to measure the time interval, producing accurate capacitance data without the complexity of the original oscilloscope-based approach.
3Measurement precision
If the A/D converter captures voltage with high resolution to reduce measurement error, then the measurement precision improves, but the device complexity increases due to the need for high-precision components and calibration systems
Solution Approach 1:
The invention inverts the conventional measurement approach by not measuring voltage directly with high precision. Instead, it measures time with high precision (using the control circuit to timestamp voltage level transitions) while accepting low-precision voltage detection (using simple comparators). This inversion of measurement focus - measuring time rather than voltage magnitude - achieves high measurement precision without requiring high-precision voltage components.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution enables precise calculation of capacitance and determination of characteristic degradation with high accuracy, ensuring reliable backup power supply even during voltage drops, by simplifying the circuit configuration and reducing errors associated with conventional A/D converter limitations.
Implementation Method 1
a first comparator 41, an output of which is inverted when voltage Vc of the energy storage section 25 reaches first predetermined voltage Vc1
Implementation Method 2
a second comparator 43, an output of which is inverted when voltage Vc of the energy storage section 25 reaches second predetermined voltage Vc2
Implementation Method 3
the control circuit 53 obtains a period tm from an inversion of an output of the first comparator 41 to an inversion of an output of the second comparator 43 when the energy storage section 25 is charged with constant current Ics
Data Source
AI summary
In an energy storage device, a charging circuit is electrically coupled to the energy storage section. A first comparator is electrically coupled to an energy storage section, and its output is inverted when voltage Vc of the energy storage section reaches first predetermined voltage Vc1. A second comparator is electrically coupled to the energy storage section, and its output is inverted when voltage Vc of the energy storage section reaches second predetermined voltage Vc2. A control circuit is electrically coupled to the first comparator and the second comparator. The control circuit obtains period tm from inversion of the output of the first comparator to the output of the second comparator. Capacitance C of the energy storage section is calculated based on this period tm and voltage change width ΔVc between the first predetermined voltage Vc1 and the second predetermined voltage Vc2.