Differential Voltage Measurement for Power Switch Junction Temperature

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Solution Overview

Problem

Conventional techniques for detecting 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 with detection pins that measure voltage drops across power switches and matched circuit elements, allowing for accurate determination of junction temperature by calculating resistance using Ohm's law and mapping it to temperature through a defined relationship.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If external temperature sensors (NTC thermistors or semiconductor-based sensors) are mounted close to the power switch, then temperature measurement is enabled, but measurement precision deteriorates because these sensors measure housing temperature or nearby temperature rather than the actual junction temperature

Engineering Contradiction:

Improvetemperature measurement precisionVSAvoidtemperature detection accuracy

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The patent replaces the mechanical/physical contact-based temperature sensing method (mounting external sensors on the housing) with an electrical measurement method. By measuring the voltage drop across the power switch and calculating resistance using Ohm's law, the system derives junction temperature through the defined relationship between resistance and temperature. This substitution eliminates the need for external physical sensors and provides direct junction temperature measurement.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent introduces voltage drop measurement as an intermediary parameter to indirectly determine junction temperature. Instead of directly measuring temperature with external sensors, the system measures the voltage drop across the power switch, calculates resistance, and then maps this resistance value to temperature through a predefined relationship. This intermediary measurement approach enables accurate junction temperature detection without physical contact.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Loss of time

If external temperature sensors are used to monitor power switch temperature, then temperature monitoring is achieved, but response time deteriorates due to intrinsic delay in measuring housing temperature rather than junction temperature

Engineering Contradiction:

Improvetemperature detection response timeVSAvoidtemperature monitoring timeliness

Core Design Contradiction:

Loss of timeVSReliability

Solution Approach 1:

The patent replaces the slow thermal conduction-based measurement method (external sensors measuring housing temperature) with an instantaneous electrical measurement method. By measuring voltage drop and calculating resistance in real-time, the system achieves immediate junction temperature detection without the thermal lag inherent in external sensor approaches.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The power switch itself serves as the sensing element in this approach. The voltage drop across the power switch naturally reflects its junction temperature through the resistance-temperature relationship, eliminating the need for separate external sensing components and their associated response delays. The device being monitored provides its own temperature information through its electrical characteristics.

Inventive Principle:

Principle #25Self-service

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

Enables precise temperature monitoring of power switches, enhancing safety and operational control by providing timely and accurate temperature readings.

Implementation Method 1

a first detection pin configured to receive a first signal associated with the power switch, wherein the first signal indicates a voltage drop over the power switch and a voltage drop over one or more other circuit elements

Methodology Applied

Scientific EffectVoltage drop measurement: Ohm's Law

Implementation Method 2

a second detection pin configured to receive a second signal, wherein the second signal indicates a voltage drop over one or more matched circuit elements, wherein the one or more matched circuit elements associated with the second signal are substantially identical to the one or more other circuit elements associated with the first signal

Methodology Applied

Scientific EffectDifferential measurement:

Data Source

PatentUS11569798B2Differential techniques for measuring voltage over a power switch

Publication Date: 2023.01.31 INFINEON TECHNOLOGIES AG

AI summary

A driver circuit is configured to deliver drive signals from an output pin to a power switch to control ON/OFF switching of the power switch. A first detection pin of the driver circuit is configured to receive a first signal associated with the power switch, wherein the first signal indicates a voltage drop over the power switch and a voltage drop over one or more other circuit elements. A second detection pin is configured to receive a second signal, wherein the second signal indicates a voltage drop over one or more matched circuit elements, wherein the one or more matched circuit elements associated with the second signal are substantially identical to the one or more other circuit elements associated with the first signal. The driver circuit is configured to determine the voltage drop over the power switch based on a difference between the first signal and the second signal.