Circuit Arrangement with Temperature-Compensated Load Current Measurement
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Solution Overview
Problem
Current circuit arrangements for semiconductor power switches require complex and expensive sense cells or senseFETs for accurate load current measurement, which increases costs and complexity.
Innovation Solution
The circuit arrangement determines load current using a sense current and a scaling factor based on the resistance ratio of the sense element to the sense zone, with temperature compensation means, such as NTC resistors, to eliminate the need for integrated sense cells, allowing the use of cost-effective conventional circuit breakers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If an integrated sense cell or senseFET is used for load current measurement, then measurement precision is improved, but device complexity and manufacturing cost increase
Solution Approach 1:
The invention extracts the sense cell function from the power switch and implements it as a separate sense zone on the printed circuit board. This separation allows the power switch to be a simple conventional component while the sense zone provides the measurement function, resolving the contradiction between measurement precision and device complexity
Solution Approach 2:
The invention introduces a sense zone as an intermediary element between the power switch and the control circuit. This sense zone, formed by conductor tracks on the PCB, acts as a mediator that provides both the current measurement function and the thermal coupling, eliminating the need for integrated sense cells in the power switch itself
2Measurement precision
If an integrated sense cell is used for load current measurement, then measurement precision is improved, but manufacturing cost increases
Solution Approach 1:
By extracting the sense cell function from the expensive power switch and implementing it as a simple conductor track pattern on the PCB, the invention significantly reduces manufacturing costs while maintaining measurement precision
Solution Approach 2:
The sense zone is implemented using inexpensive conductor tracks on the PCB rather than expensive integrated sense cells. This approach uses cheap materials (copper traces on standard PCB substrate) to achieve the measurement function, resolving the cost contradiction
3Device complexity
If the sense zone resistance is used for scaling without temperature compensation, then device complexity is reduced, but measurement precision deteriorates due to temperature-dependent resistance changes
Solution Approach 1:
The invention implements feedback by continuously monitoring the temperature at the sense zone location and using this information to dynamically adjust the scaling factor. This closed-loop approach compensates for temperature-induced resistance changes, maintaining measurement precision without adding significant complexity
Solution Approach 2:
The invention changes the scaling factor parameter based on temperature conditions. By adjusting the scaling factor according to the measured temperature, the system compensates for resistance changes in the sense zone, maintaining measurement accuracy across varying temperatures
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
This solution enables reliable load current measurement and protection without integrated sense cells, reducing costs and complexity while maintaining accurate temperature compensation across various power switches.
Implementation Method 1
The means for compensating for changes in the scaling factor resulting from temperature changes can comprise an NTC (negative temperature coefficient) resistor, for example
Data Source
Figure 1
Figure 2~3
Figure 4
AI summary
The switching arrangement (10) has a circuit-breaker arranged on a printed circuit board (12), which has a control or evaluation unit (20) for a load current on the basis of determined scythe stream and a scaling factor. The control or evaluation unit has a device (24), over which the determination the load current due to changes of temperature in relation to the temperature given in advance, results to compensate changes of the scaling factor.