Linear Regulator Current Isolation for Accurate DUT Measurement
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Solution Overview
Problem
Conventional current measurement systems struggle to accurately measure discontinuous electrical current with high dynamic range, particularly in low power consumption devices like battery-powered medical devices, due to the influence of non-switching currents and the use of conventional voltage regulators that do not match output and input currents.
Innovation Solution
A test system employing a linear voltage regulator with an isolated supply current and a power capacitor to measure current consumption, using a controller to regulate switching states and isolate the current path, ensuring accurate measurement by minimizing leakage and quiescent currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a conventional low-dropout or linear voltage regulator is used to provide operating power, then the regulator can source internal voltage reference and error amplifier, but the input current will always be higher than the output current
Solution Approach 1:
The voltage regulator is segmented into two independent power domains: the input voltage terminal supplies current only to the output terminal through the pass transistor, while a separate independent voltage supply powers the internal components (voltage reference source, error amplifier, buffer amplifier). This segmentation isolates the measurement current path from the regulator's internal current consumption, enabling accurate current measurement.
Solution Approach 2:
An independent voltage supply acts as an intermediary power source that provides operating power to the voltage reference source, error amplifier, and buffer amplifier without affecting the measurement current path. This intermediary supply allows the regulator to function properly while keeping the input current equal to the output current for accurate measurement.
2Use of energy by moving object
If the switching period is increased for low load currents during standby mode, then the device can operate in as-needed switching scheme, but the input filter capacitors become ineffective and the current measurement accuracy is adversely affected
Solution Approach 1:
The harmful non-switching currents and quiescent currents are extracted and isolated from the measurement current path by using the independent voltage supply to power the regulator's internal components. This extraction allows accurate measurement of the DUT's discontinuous current with high dynamic range by removing the regulator's current consumption from the measurement.
3Adaptability or versatility
If conventional current measurement systems are used to measure discontinuous current with high dynamic range, then the systems can measure continuous current, but the measurement accuracy suffers due to non-switching currents
Solution Approach 1:
The voltage regulator serves itself by using an independent voltage supply to power its internal components (voltage reference source, error amplifier, buffer amplifier), thereby eliminating the need for these components to draw current from the input terminal. This self-service approach enables the regulator to maintain input current equal to output current, allowing accurate measurement of discontinuous current with high dynamic range.
Data Source
AI summary
A linear voltage regulator is disclosed. The voltage regulator is configured and controlled such that its output current is substantially equal to the input current. A test system for measuring electrical current consumption of a device under test (DUT) is disclosed. The test system comprises a controller coupled to a power capacitor, a voltage regulator, and a switching circuit. The controller may be configured to: control the switching circuit to place the test system into a charging state to charge the power capacitor with the DC voltage source, at a first time point, control the switching circuit to place the test system into a measurement state such that the power capacitor provides the capacitor voltage to the voltage regulator, and at a second time point after the first time point, calculate electrical current provided by the power capacitor.