Current Sensor Level Shifting for High-Voltage Sense Resistors
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Solution Overview
Problem
Conventional current sensors are bulky and expensive to manufacture, limiting their widespread adoption in efficient power management applications such as electric automobiles.
Innovation Solution
A current sensor utilizing a differential resistor level shift technique is implemented on a single silicon chip, featuring a circuit with upper and lower resistors and an amplifier to provide a compact and cost-effective solution, capable of handling high voltages and currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional current sensors (hall devices, magneto-impedance devices) are used, then current sensing capability is achieved, but the device becomes bulky and expensive to manufacture
Solution Approach 1:
The patent replaces mechanical/magnetic sensing systems (hall devices, magneto-impedance devices with spiral coils) with an electrical circuit system using resistors and an operational amplifier. The current sensing function is achieved through voltage division and amplification in an electrical domain, eliminating the need for magnetic cores, hall elements, and complex coil structures, thereby reducing device size and manufacturing cost
Solution Approach 2:
The patent changes the sensing parameter from magnetic field detection to voltage detection. By converting the current measurement problem into a voltage measurement problem through the sense resistor, and then using the resistor divider network to scale the voltage to suitable levels for the operational amplifier, the system achieves current sensing with simpler, smaller components
2Measurement precision
If a sense resistor is used to detect current, then current measurement is enabled, but voltage level shifting is required to match amplifier input requirements
Solution Approach 1:
The patent introduces an intermediary resistor divider network between the sense resistor and the operational amplifier. This intermediary circuit performs two functions: it scales the voltage from the sense resistor to match the amplifier's input voltage range, and it provides level shifting to ensure the amplifier operates within its common-mode voltage range. This intermediary solution simplifies the overall design compared to using complex level-shifting circuits
Solution Approach 2:
The operational amplifier is configured to perform multiple functions simultaneously: it amplifies the voltage signal from the resistor divider, provides level shifting to match input common-mode requirements, and offers impedance buffering. This multi-functionality reduces the need for additional dedicated circuits, simplifying the overall design
Data Source
AI summary
A circuit for sensing a current includes a first upper resistor having a first end coupled to a first end of a sense resistor, the sense resistor being configured to receive an input current. A second upper resistor has a first end coupled to a second end of the sense resistor, so that the sense resistor defines a first potential between the first and second ends of the sense resistor. A first lower resistor is provided between the first upper resistor and the ground. A second lower resistor is provided between the second upper resistor and the ground. An amplifier has a first input node and a second input node, the first input node being coupled to a node between the first upper resistor and the first lower resistor. The second input node is coupled to a node between the to the second upper resistor and the second lower resistor. The first and second input nodes defines a second potential corresponding to the first potential.