Switching Circuit Overcurrent Detection Without Sense Resistor Loss
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Solution Overview
Problem
Existing power semiconductor devices experience power loss due to the sense resistor when the power device is in an on state, which is not effectively addressed in current technologies for overcurrent detection in switching devices.
Innovation Solution
A circuit for a switching device is designed with two parallel paths, each containing a field effect transistor and an inductor, where the maximum current during conduction differs between the paths, allowing for overcurrent detection based on the voltage difference across the inductors, thereby reducing power loss without the need for a shunt resistor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a sense resistor is used for overcurrent detection, then overcurrent detection capability is improved, but power loss increases
Solution Approach 1:
The patent extracts the power loss problem by removing the sense resistor from the main current path. Instead of using a sense resistor that dissipates power, the invention uses the inherent parasitic inductance of the PCB layout and differential voltage measurement to detect overcurrent conditions without adding significant power loss to the system.
Solution Approach 2:
The patent introduces an intermediary approach by using the parasitic inductance of the PCB trace and differential voltage measurement as a mediator between the current flow and detection. This allows overcurrent detection without requiring a dedicated sense resistor that would cause power loss, effectively using the existing electromagnetic field characteristics as the detection medium.
2Measurement precision
If a sense resistor is used for overcurrent detection, then overcurrent detection capability is improved, but device complexity increases
Solution Approach 1:
The patent applies self-service by utilizing the parasitic inductance that naturally exists in the PCB layout and circuit traces. Instead of adding external sense resistors and complex detection circuits, the invention makes the existing parasitic elements serve the detection function, thereby reducing overall device complexity while maintaining detection capability.
Solution Approach 2:
The patent makes the parasitic inductance serve multiple functions: it acts as both the current path conductor and the detection element. The same PCB trace that carries the current also provides the inductive effect needed for overcurrent detection, eliminating the need for separate sense resistors and reducing circuit complexity.
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 proposed solution effectively suppresses power loss in switching devices by enabling accurate overcurrent detection while minimizing power consumption, thus improving the efficiency of the switching system.
Implementation Method 1
a first inductor connected to a source of the first field effect transistor... a second inductor connected to a source of the second field effect transistor... voltage difference between a voltage across the first inductor and a voltage across the second inductor
Data Source
AI summary
A power loss of a switching device is suppressed. Circuit for a switching device is used in switching device. Switching device includes first path and second path. First path includes first field effect transistor and first inductor. Second path includes second field effect transistor and second inductor. First path and second path are connected in parallel to power supply. A first maximum current that is a maximum current during conduction of first field effect transistor is smaller than a second maximum current that is a maximum current during conduction of second field effect transistor. Circuit for a switching device includes processing part. Processing part executes a specific operation according to a voltage difference between voltage across first inductor and voltage across second inductor.