Power Supply Current Measurement Circuit with Parallel Sense Resistors
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Solution Overview
Problem
Existing power supply and measurement circuits are limited in continuously measuring current over a large dynamic range due to the need for multiple resistors or sensitive equipment, and previous solutions introduce slow switching and transient issues during range changes.
Innovation Solution
A power supply with a current measurement circuit using a set of two or more sense resistors in parallel, controlled by switching circuitry and a controller to manage impedance changes, allowing continuous current measurement across a wide range while maintaining consistent voltage output through a high-speed regulator.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple sense resistors with different impedances are used to measure current over a large dynamic range, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The measurement circuit is segmented into multiple sense resistors with different impedance ranges, each optimized for specific current ranges. The controller selectively activates appropriate resistors based on detected current levels, allowing precise measurement across a wide dynamic range without requiring all resistors to be simultaneously connected, thus managing circuit complexity.
Solution Approach 2:
The measurement circuit dynamically switches between different sense resistors based on the current being measured. The controller monitors current levels and activates the appropriate resistor configuration, transforming a static complex circuit into a dynamic system that adapts its complexity to the measurement requirements.
2Object-affected harmful factors
If soft switching method is used to reduce transient voltages during resistor switching, then harmful factors are reduced, but switching speed decreases
Solution Approach 1:
A current source circuit acts as an intermediary between the sense resistors and the measurement system. This intermediary maintains a substantially constant current during switching transitions, preventing transient voltage spikes that would otherwise occur when switching between resistors of different impedances. The constant current source absorbs the switching transients while maintaining stable measurement conditions.
3Device complexity
If multiplexed system with single resistor at a time is used, then device complexity is reduced, but measurement reliability decreases
Solution Approach 1:
The measurement system maintains continuous operation by having the current source continuously active and switching between sense resistors without interrupting the measurement process. The controller seamlessly transitions between different resistor configurations while maintaining constant current flow, ensuring uninterrupted measurement capability across the full dynamic range.
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 continuous current measurement over a wide dynamic range with rapid switching, avoiding delays and abrupt voltage changes, using low-cost equipment that can handle varying loads without the need for expensive, sensitive ADCs, and maintaining a consistent supply.
Implementation Method 1
When measuring current via sense resistors
Implementation Method 2
switching circuitry, responsive to a control signal to connect one or more of the sense resistors between the supply voltage terminal and the output voltage terminal
Data Source
AI summary
A power supply is described having a current measurement circuit connected between a supply voltage terminal and an output voltage terminal of the power supply. The current measurement circuit comprises a set of two or more sense resistors in a parallel configuration, first and second ones of the sense resistors having different impedances. Switching circuitry is provided, which is responsive to a control signal to connect one or more of the sense resistors between the supply voltage terminal and the output voltage terminal. A controller is operable to generate the control signal in dependence on a measured current level across the set of sense resistors. In this way, by switching the resistors in and out of the circuit, the voltage drop across the measurement circuit can be kept to a desired range.