Semiconductor Switch Control Device Using Body Diode Voltage for Thermal Monitoring
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Solution Overview
Problem
Conventional semiconductor switch control devices in electric and hybrid electric vehicles face challenges in accurately determining the temperature state of semiconductor switches, leading to inefficiencies in thermal management and potential overheating.
Innovation Solution
A semiconductor switch control device is designed with a forward switch and a backward switch, each equipped with a body diode, where the controller determines the temperature state based on the forward voltage of the body diode, allowing for accurate temperature measurement and failure detection, and includes a precharge circuit for constant current control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If semiconductor switches are used to replace mechanical relays, then the response speed and control precision are improved, but the temperature monitoring accuracy and thermal management capability deteriorate
Solution Approach 1:
The patent introduces a body diode as an intermediary element within the semiconductor switch structure. This body diode serves as a mediator that provides temperature information through its forward voltage characteristics, enabling indirect but accurate temperature monitoring without adding external sensing components that would slow down the switch response.
Solution Approach 2:
The semiconductor switch structure is designed to monitor its own temperature through the body diode's forward voltage characteristics. The switch essentially serves itself by using an inherent component (the body diode) to provide temperature feedback, eliminating the need for separate temperature sensors and their associated wiring that could affect response time.
2Reliability
If temperature monitoring is implemented using conventional methods, then the thermal management is maintained, but the measurement accuracy and reliability deteriorate
Solution Approach 1:
The patent utilizes the temperature-dependent forward voltage characteristic of the body diode as the monitoring parameter. By measuring changes in forward voltage (which varies predictably with temperature), the system achieves accurate temperature measurement. This parameter change approach is more reliable than conventional resistance-based methods because the forward voltage has a stronger and more linear temperature dependency.
Solution Approach 2:
The patent replaces mechanical or resistance-based temperature sensing methods with an electrical voltage measurement approach. Instead of using thermistors or RTDs that require physical connections and complex circuits, the system uses the body diode's forward voltage drop, which can be measured electrically with high precision and integrated directly into the control circuitry.
3Reliability
If thermal design margins are increased to prevent overheating, then the reliability is improved, but the device complexity and size increase
Solution Approach 1:
The patent implements a feedback mechanism where the controller continuously monitors the forward voltage of the body diode and uses this information to determine the temperature state of the semiconductor switch. Based on this real-time feedback, the controller can adjust operating parameters or trigger protective actions when temperature thresholds are approached, enabling active thermal management rather than relying on conservative static design margins.
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 precise temperature monitoring and failure detection, preventing overheating and improving the performance and reliability of semiconductor switches by eliminating the need for large thermal design margins.
Implementation Method 1
the controller determines a temperature state of the semiconductor switch module based on a forward voltage of the body diode of the forward switch
Implementation Method 2
a precharge circuit that controls the backward switch and allows a constant precharge current to flow
Data Source
AI summary
A semiconductor switch control device includes a first FET and a second FET arranged adjacent to each other, in which source terminals are connected in series. A drain terminal of the first FET is connected to a high voltage battery, and a drain terminal of the second FET is connected to a high voltage load. A controller determines a temperature state of a minus-side main relay including the second FET based on a forward voltage of a body diode of the first FET.