MOSFET Power Supply Cutoff Using Temperature-Tracking Resistors
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Solution Overview
Problem
Existing power supply control apparatuses for vehicles take a long time to calculate the current flowing through a MOSFET, leading to delayed switching off when the current is large, potentially causing overcurrent issues.
Innovation Solution
A power supply control apparatus that includes a resistor circuit, a current adjustment circuit, and a switch circuit. The resistor circuit adjusts current based on the voltage across the semiconductor switch and its resistance value, and the switch circuit turns off the semiconductor switch when the voltage across the resistor exceeds a predetermined value, regardless of the ambient temperature fluctuations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the computation element calculates the current flowing through the MOSFET based on voltage and temperature, then the control precision is improved, but the response time deteriorates
Solution Approach 1:
The patent introduces a resistor circuit as an intermediary element that converts the current flowing through the MOSFET into a proportional voltage signal. This voltage signal can be directly compared against a threshold voltage to determine whether to switch off the MOSFET, eliminating the need for complex calculation operations while maintaining accurate current monitoring capability.
Solution Approach 2:
The patent replaces the computational system (computation element performing mathematical calculations) with a direct electrical comparison system (voltage threshold comparison). This substitution eliminates calculation time delays while preserving the ability to accurately detect current conditions and trigger protective switching actions.
2Reliability
If the MOSFET is switched off immediately when current is large, then the reliability is improved, but the calculation time requirement increases the complexity
Solution Approach 1:
The resistor circuit serves as a mediator that provides a direct voltage representation of the MOSFET current. This voltage can be directly compared to a threshold voltage to determine overcurrent conditions, enabling immediate protective action without complex calculation systems, thus improving reliability while reducing control system complexity.
Solution Approach 2:
The resistor circuit automatically generates a voltage signal that is directly proportional to the MOSFET current, eliminating the need for external computation or processing. The system self-regulates by using the current itself to generate the control signal needed for overcurrent protection, simplifying the overall control architecture.
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 the semiconductor switch to be switched off at the appropriate timing without calculating the current, thereby preventing overcurrent and ensuring timely power supply control.
Implementation Method 1
a current adjustment circuit configured to adjust a current flowing through the resistor circuit to a value obtained by dividing a voltage across the semiconductor switch by a resistance value of the resistor circuit
Data Source
AI summary
A power supply control apparatus controls power supply from a DC power source to a load by switching on or off a power supply FET. The current adjustment circuit adjusts the current flowing through the resistor circuit to a value obtained by dividing the voltage between the drain and the source of the power supply FET by the resistance value of the resistor circuit. A drive circuit switches off the power supply FET when a voltage across the detection resistor exceeds a predetermined voltage. The on-resistance value of the power supply FET fluctuates according on the ambient temperature of the power supply FET. The resistance value of the resistor circuit fluctuates in the same direction as the on-resistance value according to the ambient temperature of the power supply FET.