Semiconductor Switch Control Device for Overcurrent Protection
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Solution Overview
Problem
Semiconductor switches in electric vehicles and hybrid electric vehicles face challenges in controlling overcurrents during short circuits, leading to overheating and difficulty in blocking currents effectively.
Innovation Solution
A semiconductor switch control device is designed with a first semiconductor switch between the power supply and load, a second semiconductor switch to regulate current, and a controller that applies a limiting gate voltage to the second switch when an overcurrent is detected, setting the current limit value between abnormal and maximum current values to manage and block excessive currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a semiconductor switch is used to replace mechanical relays for current control, then the switching speed and control precision are improved, but the device becomes vulnerable to overheating and damage during overcurrent conditions
Solution Approach 1:
The patent introduces a current-limiting circuit as an intermediary component between the power supply and the semiconductor switch. This circuit actively monitors the input current and intervenes when overcurrent conditions are detected, preventing the semiconductor switch from being directly exposed to damaging current levels while maintaining the benefits of semiconductor switching technology
Solution Approach 2:
The patent implements preliminary protective action by continuously monitoring the input current before it can reach dangerous levels. The control circuit detects overcurrent conditions in advance and activates the current-limiting mechanism proactively, preventing overheating before it occurs rather than reacting after damage has begun
2Productivity
If the current limit value is set close to the maximum current value to maximize power delivery, then the productivity is improved, but the temperature increase during overcurrent becomes excessive
Solution Approach 1:
The patent dynamically adjusts the current limit parameter based on operating conditions. By changing the current limit value adaptively rather than using a fixed threshold, the system can allow higher currents during normal operation to maximize productivity while automatically reducing the limit during conditions that would cause excessive temperature rise, thus optimizing both productivity and thermal management
3Temperature
If the current limit value is set too low to prevent overheating, then the temperature control is improved, but the current blocking capability during short circuit becomes insufficient
Solution Approach 1:
The patent implements dynamic current limiting where the current limit value is not fixed but adapts based on real-time monitoring of temperature, current magnitude, and duration. This dynamic approach allows the system to maintain lower current limits during conditions that would cause overheating while permitting higher current limits during brief transient conditions or when thermal margins are available, thus simultaneously achieving temperature control and maintaining adequate current blocking capability
Solution Approach 2:
The patent employs feedback control by continuously monitoring the semiconductor switch temperature and input current, then adjusting the current limit accordingly. This closed-loop feedback mechanism ensures that the current limit is optimized based on actual thermal conditions, preventing overheating while maintaining the ability to block excessive currents that could cause damage
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 solution effectively suppresses temperature increases in semiconductor switches during overcurrents, prevents erroneous blocking, and protects the switches from damage by limiting currents to safe levels, while maintaining low on-resistance and reducing power loss.
Implementation Method 1
a second semiconductor switch provided between the load and a cathode of the power supply to regulate the current flowing from the load to the power supply according to an applied setting gate voltage and limit a current flowing through the first semiconductor switch
Data Source
AI summary
The semiconductor switch control device includes a first FET provided between an anode of a battery and a load and a second FET arranged between a cathode of the battery and the load, in which in a case where a current value that is larger than an abnormal current value indicating that a first drain current flowing through the first FET is an overcurrent and smaller than a maximum current value of the first drain current that can be tolerated by the first FET is set as a current limit value, a limiting gate voltage for setting the current value of the first drain current to a current limit value is applied to the second FET.