Active Discharge Circuit With Thermistor-Led Power Dissipation
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Solution Overview
Problem
Existing active discharge devices for electrical energy storage in motor vehicles dissipate most of the discharge power in the switch, leading to potential overheating and reduced lifespan, as the power dissipated by the switch is significant due to thermal coupling with the thermistor.
Innovation Solution
The control device provides a control signal independently of the thermistor's resistance, allowing the thermistor to have a high resistance, thereby dissipating most of the discharge power, and the switch only dissipates a small part, with thermal decoupling and strategic placement reducing heat transfer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the thermistor is thermally coupled to the switch with low resistance, then the control signal is stable, but the switch dissipates most of the discharge power causing overheating and reduced lifespan
Solution Approach 1:
The patent extracts the thermistor from the thermal field of the switch by increasing the spatial separation between them. This allows the thermistor to perform its function of providing a stable control signal while being thermally decoupled from the switch, preventing the switch from overheating during discharge operations.
Solution Approach 2:
The patent introduces a thermal barrier or insulation structure as an intermediary between the thermistor and the switch. This intermediary element blocks heat transfer from the switch to the thermistor, allowing the thermistor to maintain its resistance characteristics for stable control signaling while the switch can dissipate heat independently.
2Reliability
If the thermistor resistance is low to maintain control signal, then the control is stable, but the switch must dissipate significant power reducing its lifespan
Solution Approach 1:
The patent extracts the thermistor from the thermal field of the switch by increasing the spatial separation between them. This allows the thermistor to perform its function of providing a stable control signal while being thermally decoupled from the switch, preventing the switch from overheating during discharge operations.
Solution Approach 2:
The patent changes the resistance parameter of the thermistor to a high resistance value. This allows the thermistor to provide adequate control signaling with minimal current draw, thereby reducing the power dissipation burden on the switch while maintaining control stability.
3Ease of operation
If the thermistor is placed close to the switch for thermal coupling, then the control device can regulate discharge current, but the switch overheats due to significant power dissipation
Solution Approach 1:
The patent extracts the thermistor from the thermal field of the switch by increasing the spatial separation between them. This allows the thermistor to perform its function of providing a stable control signal while being thermally decoupled from the switch, preventing the switch from overheating during discharge operations.
Solution Approach 2:
The patent introduces a thermal barrier or insulation structure as an intermediary between the thermistor and the switch. This intermediary element blocks heat transfer from the switch to the thermistor, allowing the thermistor to maintain its resistance characteristics for stable control signaling while the switch can dissipate heat independently.
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 design significantly reduces the power dissipated by the switch, minimizing the risk of overheating and extending its lifespan while ensuring safe and efficient discharge of electrical energy.
Implementation Method 1
the thermistor can be chosen with a very high resistance, enabling it to dissipate most of the discharge power
Implementation Method 2
the thermistor's temperature increases due to thermal coupling between the switch and the thermistor. This leads to an increase in the thermistor's resistance
Data Source
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AI summary
This device (200) for actively discharging an electrical energy storage device (C1) comprises: - a branch (204) comprising first and second ends (206, 208) intended to be connected respectively to positive and negative terminals of the electrical energy storage device (C1), and, between the two ends (206, 208), a thermistor (210) having resistance that increases with the temperature of the thermistor (210) and a switch (212) designed to receive a control signal (vGS) to change from an open state to a closed state, the thermistor (210) and the switch (212) being connected to each other such that, when the switch (212) is in the closed state, a discharge current (iD) enters via the first end (206), passes through the thermistor (210) and the switch (212) in succession and exits via the second end (208); and - a control device (214) for the switch (212). The control device (214) is connected to the switch (212) so as to provide the control signal (vGS) regardless of the resistance of the thermistor (210).