Semiconductor Relay Current Sensing Without Shunt Resistors
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Solution Overview
Problem
Current high-voltage relay systems in vehicles require additional components for current detection, leading to increased complexity and electrical power loss due to the use of shunt resistors for current sensing.
Innovation Solution
A semiconductor relay integrated with a voltage detection section and temperature sensors, which allows for current detection within the relay itself without additional components, reducing power loss and complexity by using the relay's bus bar resistance and temperature characteristics to calculate load current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a current sensor is installed separately from the high-voltage relay, then current detection function is achieved, but the number of components increases
Solution Approach 1:
The patent combines the current detection function with the high-voltage relay by integrating a voltage detection section that measures voltage across the relay's own bus bar. This merging eliminates the need for a separate current sensor, reducing component count while maintaining current detection capability through the relationship I = V/R where V is the measured voltage and R is the known bus bar resistance.
Solution Approach 2:
The high-voltage relay is designed to perform multiple functions: it serves as both the switching device for high-voltage circuits and as the current detection device. The bus bar, originally just a conductive element, becomes a dual-purpose component that both carries current and serves as the sensing element for current measurement through voltage detection.
2Measurement precision
If a shunt resistor is installed on the high-voltage path, then current detection is achieved, but electrical power loss increases
Solution Approach 1:
The system uses the high-voltage relay's own bus bar as the sensing element rather than requiring an external shunt resistor. The voltage detection section measures the voltage drop across the bus bar, and since the bus bar's resistance is already part of the circuit design, no additional power loss is introduced. The measurement is achieved using the existing structural components.
Solution Approach 2:
The patent changes the detection approach from direct current measurement (which would require a low-resistance shunt) to voltage measurement across the existing bus bar. By measuring voltage and calculating current through I = V/R, the system avoids the power loss associated with shunt resistors while achieving accurate current detection.
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 efficient current detection at high-voltage circuits without increasing the number of components, improving reliability and reducing power loss by eliminating the need for shunt resistors and additional detection sections.
Implementation Method 1
a bus bar having a resistance value that changes in accordance with temperature change
Implementation Method 2
a temperature sensor disposed on the bus bar and configured to detect a temperature of the bus bar
Implementation Method 3
a semiconductor switching element disposed on the electric path between the high-voltage battery and the high-voltage load and configured to open or close the electric path
Data Source
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AI summary
A semiconductor relay (16) includes a switching element (32) disposed on an electric path (4) between a high-voltage battery (2) and a high-voltage load (3) and configured to open and close the electric path (4), and a detection section (19) configured to detect a physical quantity related to load current (IL) flowing through the electric path (4). A vehicle current detection device (1A) includes the semiconductor relay (16), and a control circuit (17) configured to control the semiconductor relay (16), and the control circuit (17) detects the load current (IL) flowing through the electric path (4) based on the physical quantity detected by the detection section (19). With this configuration, the semiconductor relay and the vehicle current detection device can detect current at a high-voltage circuit without increase in the number of components.