Busbar Current Sensing With Temperature Compensation
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Solution Overview
Problem
Existing technologies fail to address the challenge of providing a precise and efficient current sensing system that can handle high currents in hybrid and electric vehicles, particularly in traction inverters, on-board chargers, and DC/DC converters, where the shunt resistor-based methods result in significant power dissipation and heating, necessitating a more efficient and compact solution.
Innovation Solution
A current sensing system utilizing a busbar made of copper alloy, with integrated temperature compensation, replaces the shunt resistor, employing an isolated amplifier and signal conditioning circuit to minimize power dissipation and maintain accuracy, thereby eliminating the need for separate shunt resistors and hall sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a shunt resistor is used for current measurement, then current sensing is achieved, but power losses and heating increase due to voltage drop across the resistor
Solution Approach 1:
The busbar is designed to serve dual functions: as a current-carrying conductor and as a sensing element for current measurement. By integrating the sensing function into the existing busbar structure, the patent eliminates the need for separate shunt resistors, thereby reducing power losses while maintaining measurement capability through voltage sensing across the busbar's inherent resistance
Solution Approach 2:
The busbar is transformed into a multi-functional component that simultaneously performs electrical connection and current sensing functions. This universal application reduces the total number of components and minimizes energy losses associated with dedicated shunt resistors
2Loss of energy
If a shunt resistor with low resistance value is used, then power losses are reduced, but the resistor becomes smaller and lighter which may compromise accuracy and drift characteristics
Solution Approach 1:
An isolated amplifier is introduced as an intermediary device to sense the voltage across the busbar without direct galvanic connection to the high-current path. This mediator enables accurate voltage measurement while maintaining electrical isolation, allowing the use of low-resistance busbars without compromising measurement precision or safety
3Device complexity
If the busbar is used as sensing element, then separate shunt resistor is avoided saving space and cost, but temperature dependency of resistance affects measurement accuracy
Solution Approach 1:
The patent compensates for temperature-induced resistance changes by introducing a temperature compensation circuit that adjusts the sensing parameters. By dynamically compensating for temperature effects, the system maintains measurement accuracy despite using the temperature-dependent busbar as the sensing element
Solution Approach 2:
A separate temperature compensation circuit is implemented that mirrors and counteracts the temperature effects on the busbar resistance. This compensation mechanism creates a corrected measurement signal that reflects actual current rather than temperature-induced resistance variations
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
The system achieves precise overcurrent detection with minimal power loss and reduced size, offering cost-effective and efficient current sensing by compensating for temperature-dependent resistance variations using a hardware-based solution.
Implementation Method 1
the amplifier is configured to sense a voltage difference or voltage drop across a section of the busbar caused by a current flow in the current path
Implementation Method 2
the temperature compensation circuit effects as a temperature dependent resistance with a temperature coefficient which has an opposite sign as the resistance of the busbar
Data Source
AI summary
A current sensing system includes a busbar connected in a current path between a power supply and a load. The busbar includes a temperature dependent resistance with a specific temperature coefficient. An amplifier is configured to sense a voltage difference across a section of the busbar caused by a current in the current path. The current sensing system includes a temperature compensation circuit, wherein the temperature compensation circuit is effective as a temperature dependent resistance with a temperature coefficient which has a sign opposite from the resistance of the busbar. A first input of a comparator is directly or indirectly connected to a second terminal of the signal conditioning circuit. The current sensing system includes a logic circuitry, which is configured to control a state of a switch, which is disposed in the current path dependent on an output signal of the comparator.