Capacitor-Based Current Measurement for Discontinuous DUT Loads
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Solution Overview
Problem
Conventional current measurement systems struggle to accurately measure electrical current with discontinuous and high dynamic range characteristics, particularly in low power consumption devices like battery-powered medical devices, due to the influence of non-switching currents and the inefficacy of input filter capacitors during standby mode.
Innovation Solution
A test system utilizing a power capacitor and a voltage regulator configured to operate in a current-isolated manner, with a controller managing switching elements to charge and discharge the capacitor, allowing precise calculation of current consumption based on sampled voltage values and discharge characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional current measurement systems are used to measure discontinuous current with high dynamic range, then the measurement system can operate continuously, but the measurement accuracy deteriorates due to non-switching currents and ineffective filter capacitors
Solution Approach 1:
The measurement process is divided into distinct charging and discharging phases. The capacitor is charged during one phase and discharged during another, allowing separate measurement of current characteristics. This segmentation enables accurate capture of discontinuous current profiles that conventional continuous measurement systems miss.
Solution Approach 2:
The capacitor is pre-charged to a known voltage state before the actual current measurement begins. This preliminary charging action establishes a controlled initial condition, ensuring that subsequent discharge measurements accurately reflect the device under test's current consumption without interference from unknown initial states.
2Use of energy by moving object
If the switching period is increased during standby mode, then the device reduces power consumption, but the input filter capacitors become ineffective and current measurement accuracy deteriorates
Solution Approach 1:
The measurement system uses periodic charging and discharging cycles of the capacitor. During standby mode, the system captures the periodic nature of the discontinuous current by measuring voltage changes during controlled charge and discharge phases, maintaining measurement accuracy even when the device operates with extended switching periods.
Solution Approach 2:
The capacitor serves as an intermediary energy storage element between the device under test and the measurement system. It decouples the measurement process from the direct current path, allowing accurate measurement of discontinuous current without being affected by the switching frequency or filter capacitor inefficacy during standby mode.
3Power
If a conventional voltage regulator is used, then the regulator can provide operating voltage, but the input current is always higher than output current due to internal power consumption
Solution Approach 1:
The voltage regulator's internal power consumption is extracted and separated from the measurement path. By using an external capacitor for charging and measuring only the discharge current through the regulator, the system isolates the regulator's quiescent current from the measurement, enabling accurate measurement of only the load current.
Solution Approach 2:
The capacitor serves itself by being charged from the regulator output and then discharging back through the regulator during measurement. This self-service cycle allows the capacitor to provide energy storage and current isolation functions without requiring additional active components, maintaining current matching accuracy while providing necessary operating voltage.
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
Enables accurate and isolated measurement of electrical current consumption in devices with high dynamic range, effectively addressing the limitations of conventional systems by isolating the current and minimizing leakage and quiescent effects on the accuracy of conventional systems, thereby enhancing measurement accuracy and precision.
Implementation Method 1
a power capacitor with a power terminal and a ground terminal and configured to provide capacitor voltage at the power terminal
Data Source
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AI summary
A test system for measuring electrical current consumption of a device under test (DUT) includes a capacitor with power and ground terminals; a voltage regulator with input and output terminals; first and second switching elements; and a controller. The voltage regulator generates a DUT operating voltage based on its input voltage. The first switching element is arranged between a direct current (DC) voltage source and the regulator input, and the second switching element is arranged between the DC voltage source and the capacitor. The controller operates the switching elements to charge the capacitor, and to configure the test system for measuring operating current of the DUT using the capacitor as the power source.