Parallel Semiconductor Switch Circuit for Half-On Failure Protection
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Solution Overview
Problem
Existing load control devices using semiconductor switches face challenges in detecting and preventing overheating due to half-on failures, which can lead to prolonged heat generation and potential circuit failure, especially when the host ECU is in a stopped or intermittent state.
Innovation Solution
A load control device with a parallel switch circuit comprising two semiconductor switches, where a common ON-OFF control signal is applied to both switches, and a failure detection unit and current interruption unit work together to interrupt power supply when a failure is detected, ensuring that current is concentrated on the switch with lower resistance, thereby preventing overheating.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a temperature detection unit is disposed outside the semiconductor switch to detect heat generation, then half-on failure can be detected, but there is a large delay in detection time due to heat propagation delay
Solution Approach 1:
The temperature detection unit is nested inside the semiconductor switch package, with the detection unit positioned in thermal contact with the semiconductor switch die. This allows the temperature detection unit to directly measure the temperature at the heat generation source without waiting for heat to propagate to an external location, thereby eliminating detection delay while maintaining reliable failure detection capability
Solution Approach 2:
A thermal coupling structure acts as an intermediary between the semiconductor switch die and the temperature detection unit, efficiently transferring heat from the switch to the detector. This intermediary ensures rapid and accurate temperature measurement while maintaining electrical isolation, resolving the contradiction between reliable detection and fast response time
2Use of energy by stationary object
If the host ECU is in a stopped state or intermittent operation state to save energy, then power consumption is reduced, but the time until failure such as heating is detected becomes long
Solution Approach 1:
The temperature detection unit continuously monitors the semiconductor switch temperature independently of the host ECU operation state. The detection unit operates autonomously using minimal power, automatically detecting temperature rises and triggering failure alerts even when the main system is in low-power mode, thus maintaining reliability without significantly increasing power consumption
Solution Approach 2:
The temperature detection unit provides continuous feedback on the semiconductor switch temperature to the control system. This feedback mechanism enables the system to detect failures immediately regardless of ECU operation state, as the temperature monitoring operates independently and continuously, preventing the delay that would occur during stopped or intermittent operation periods
3Device complexity
If a single semiconductor switch is used to control load energization, then the device structure is simple, but a half-on failure can cause large current to continue flowing and generate excessive heat
Solution Approach 1:
The single semiconductor switch is divided into multiple parallel switches, each with its own temperature detection unit. This segmentation allows the system to isolate and detect failures in individual switches, preventing a single point of failure from causing excessive heat generation across the entire load control circuit, while maintaining relatively simple overall structure
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 configuration effectively prevents overheating by quickly detecting failures and interrupting current flow, reducing temperature rises and preventing damage to the semiconductor switches, even in cases of half-on failures, and allows for safe operation during emergencies.
Implementation Method 1
it is expected that a delay of the time from occurrence of the half-on failure inside the semiconductor switch to actual detection of the half-on failure is large due to a delay of heat propagation
Implementation Method 2
a large amount of heat may be generated by the resistance inside the failed semiconductor switch due to an influence of a large current that continues to flow through the load
Data Source
AI summary
A load control device includes an energization circuit unit connected between a power source and a load and configured to switch ON and OFF of energization of the load, a failure detection unit connected to a downstream side of the energization circuit unit, a current interruption unit connected to an upstream side of the energization circuit unit and configured to interrupt supply of current of the power source to the energization circuit unit based on an input from the failure detection unit, and a control unit configured to supply an ON-OFF control signal to the energization circuit unit. The energization circuit unit includes a first semiconductor switch and a second semiconductor switch which are connected in parallel to each other. The control unit supplies a common ON-OFF control signal to the first semiconductor switch and the second semiconductor switch.