Temperature-Dependent Circuit for Switching Element Actuation

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Solution Overview

Problem

Existing circuit arrangements for controlling power semiconductor switches fail to account for temperature-dependent switching behavior, leading to increased switching losses at higher temperatures and potential electromagnetic interference and overvoltages due to mismatched switching speeds.

Innovation Solution

A circuit arrangement with a temperature-dependent component, such as a resistor with a negative temperature coefficient, is used in conjunction with a second switching element and resistors to dynamically adjust the series resistance and control voltage, allowing for temperature-dependent activation of the switching element, thereby minimizing switching losses and preventing overvoltages.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of energy

If a low series resistor is used to reduce switching losses at high temperature, then switching losses are minimized, but electromagnetic interference and overvoltages occur at low temperature due to excessively fast switching edges

Engineering Contradiction:
Improveswitching lossesVSAvoidelectromagnetic interference and overvoltages
Core Design Contradiction:
Loss of energyVSObject-affected harmful factors

Solution Approach 1:

The patent applies the dynamics principle by making the series resistance value changeable based on temperature conditions. The circuit dynamically adjusts the resistance between a first resistance value (at low temperature) and a second resistance value (at high temperature) through temperature-dependent components and switching elements, allowing optimal switching performance across different temperature ranges while avoiding both excessive switching losses and harmful electromagnetic interference

Inventive Principle:
Principle #15Dynamics

Solution Approach 2:

The patent implements parameter changes by varying the series resistance parameter according to temperature. The circuit monitors temperature conditions and adjusts the effective series resistance value accordingly - using a higher resistance at low temperatures to dampen switching edges and prevent overvoltages, and a lower resistance at high temperatures to minimize switching losses, thus adapting the electrical parameter to environmental conditions

Inventive Principle:
Principle #35Parameter changes

2Object-affected harmful factors

If a high series resistor is used to prevent electromagnetic interference at low temperature, then electromagnetic interference is suppressed, but switching losses increase at high temperature due to reduced switching speed

Engineering Contradiction:
Improveelectromagnetic interferenceVSAvoidswitching losses
Core Design Contradiction:
Object-affected harmful factorsVSLoss of energy

Solution Approach 1:

The circuit dynamically switches between different resistance configurations based on temperature. At low temperatures, a higher series resistance is applied to suppress electromagnetic interference and dampen switching edges. At high temperatures, the circuit transitions to a lower resistance configuration to enable faster switching and reduce switching losses, thus adapting the resistance value to operational conditions in real-time

Inventive Principle:
Principle #15Dynamics

Solution Approach 2:

The series resistance parameter is changed according to temperature conditions. The circuit uses temperature-dependent components to detect temperature changes and adjusts the effective series resistance accordingly - maintaining a higher resistance value when temperatures are low to prevent electromagnetic interference, and reducing the resistance value when temperatures rise to minimize energy losses during switching

Inventive Principle:
Principle #35Parameter changes

3Device complexity

If a fixed series resistor is used for switching control, then circuit simplicity is maintained, but temperature-dependent switching behavior cannot be compensated

Engineering Contradiction:
Improvecircuit simplicityVSAvoidswitching behavior consistency
Core Design Contradiction:
Device complexityVSReliability

Solution Approach 1:

The patent segments the series resistance function into multiple resistance elements (first series resistor, second series resistor, third series resistor) that can be selectively activated based on temperature conditions. This segmentation allows the circuit to achieve temperature-dependent switching control by combining different resistance segments, balancing the need for reliability across temperature ranges with acceptable circuit complexity

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The patent introduces temperature-dependent components (such as thermistors or temperature sensors) as intermediaries between the fixed voltage source and the switching element. These intermediary components detect temperature changes and trigger appropriate resistance switching, enabling temperature compensation without requiring direct complex control logic, thus maintaining reasonable circuit simplicity while improving switching behavior consistency

Inventive Principle:
Principle #24Intermediary (Mediator)

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 stable and efficient switching behavior across varying temperatures, reducing switching losses and preventing harmful electromagnetic interference by dynamically adjusting the series resistance and control voltage, ensuring consistent operation of the switching element.

Implementation Method 1

A temperature-dependent component can be embodied in a variety of ways, for example as a circuit made up of operational amplifiers that are driven as a function of temperature. A temperature-dependent resistor, for example, can have a positive or a negative temperature coefficient. In the case of a temperature-dependent resistor with a negative temperature coefficient (NTC), the value of the resistor decreases with increasing temperature

Methodology Applied
Scientific EffectNegative temperature coefficient (NTC): Thermistor

Data Source

PatentEP3381127B1Circuit arrangement for the temperature-dependent actuation of a switching element
Publication Date: 2021.10.20 ROBERT BOSCH GMBH
  • EP3381127B1 patent drawingFigure 1~2
  • EP3381127B1 patent drawingFigure 3~4
  • EP3381127B1 patent drawingFigure 5~6

AI summary

The invention relates to a circuit arrangement (100) for the temperature-dependent actuation of a first switching element (S1), comprising an input terminal (EA) for accepting an input potential, an output terminal (AA) for transferring an output potential to a first control terminal (G1) of the first switching element (S1), and a temperature-dependent component (RT) which is connected between the input terminal (EA) and the output terminal (AA).