Power Switch Voltage Sensing for Junction Temperature Measurement

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Solution Overview

Problem

Conventional techniques for monitoring the junction temperature of power switches are imprecise and delayed, often relying on external components that measure housing temperature rather than the actual junction temperature.

Innovation Solution

A driver circuit that performs two or more voltage measurements at specific times, allowing for accurate determination of the voltage drop over the power switch by comparing signals when current is and isn't passing through, enabling precise temperature measurement using Ohm's law and temperature-resistance mapping.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If external temperature sensors (NTC thermistors or semiconductor-based sensors) are mounted close to the power switch, then temperature monitoring is enabled, but measurement precision is insufficient and response time is delayed

Engineering Contradiction:

Improvetemperature monitoring capabilityVSAvoidjunction temperature measurement accuracy

Core Design Contradiction:

ReliabilityVSMeasurement precision

Solution Approach 1:

The patent replaces mechanical/physical temperature sensors (NTC thermistors, semiconductor-based sensors) with an electrical measurement system that uses voltage drop measurements across the power switch. By measuring the voltage drop at zero current and comparing it to voltage drop at operating current, the system calculates resistance and derives temperature through Ohm's law and temperature-resistance relationships, eliminating the need for external physical sensors and achieving direct junction temperature measurement.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Difficulty of detecting and measuring

If external temperature sensors are used to monitor power switch temperature, then temperature detection is achieved, but response time is delayed due to intrinsic delay in measuring housing temperature

Engineering Contradiction:

Improvetemperature detection capabilityVSAvoidtemperature measurement response time

Core Design Contradiction:

Difficulty of detecting and measuringVSLoss of time

Solution Approach 1:

The patent replaces slow-responding physical temperature sensors with rapid electrical voltage measurements. The voltage drop across the power switch can be measured instantaneously using standard voltage measurement circuits, providing real-time temperature information without the thermal inertia and response delays inherent in physical temperature sensors mounted on the housing.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent performs a preliminary voltage measurement at zero current to establish a baseline voltage drop value before the power switch operates. This preliminary measurement is stored and later used to calculate temperature during operation by comparing against the operating voltage drop, enabling rapid temperature determination without requiring continuous complex measurements.

Inventive Principle:

Principle #10Preliminary action

3Measurement precision

If voltage measurements are performed during power switch operation to determine temperature, then precise junction temperature measurement is achieved, but measurement complexity increases due to timing requirements

Engineering Contradiction:

Improvevoltage drop measurement accuracyVSAvoidmeasurement circuit and timing control complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent employs periodic measurement cycles where voltage across the power switch is measured at specific intervals - once during the off-state (zero current) and once during the on-state (operating current). This periodic measurement approach, synchronized with the power switch operation, enables accurate temperature determination while keeping the measurement system relatively simple and avoiding continuous complex monitoring.

Inventive Principle:

Principle #19Periodic action

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 method provides accurate and timely temperature measurements of power switches, enhancing safety and operational control by precisely indicating junction temperature, which is crucial for reliable power switch operation, especially in high-temperature applications like electric vehicles.

Implementation Method 1

determine the resistance of the power switch based on Ohm's law

Methodology Applied

Scientific EffectOhm's Law: Ohm's Law

Implementation Method 2

The resistance, in turn, can be mapped to an indication of temperature of the power switch which may be a more precise indication of junction temperature

Methodology Applied

Scientific EffectTemperature-resistance relationship: Thermal Expansion

Data Source

PatentUS11867762B1Techniques for measuring voltage over a power switch using zero current detection point

Publication Date: 2024.01.09 INFINEON TECHNOLOGIES AG

AI summary

A method may comprise: controlling ON/OFF switching of a power switch via a driver circuit; receiving a first signal on a detection pin associated with the power switch, wherein the first signal corresponds to a first point in time when current is not passing through the power switch and wherein the first signal indicates a first voltage drop over one or more other circuit elements; receiving a second signal on the detection pin, wherein the second signal, wherein the second signal corresponds to a second point in time when current is passing through the power switch and wherein the second signal indicates a voltage drop over the power elements; and determining the voltage drop over the power switch based on a difference between the first signal and the second signal.