Commutation Diode Temperature Sensing via Reverse Current Waveform

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Solution Overview

Problem

Existing methods for determining the temperature of power semiconductor devices in power electronics are not sufficiently accurate and reliable, particularly in monitoring the depletion region of diodes within commutation circuits.

Innovation Solution

A method that involves monitoring the current waveform during a reverse current in a diode within a commutation circuit, determining the difference between the circuit current and the extremal current value caused by the reverse current, and using this difference to calculate the temperature of the depletion region, optionally incorporating load current and intermediate circuit voltage for increased accuracy.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If NTC temperature sensors are integrated into the power electronics, then temperature measurement capability is provided, but device complexity and reliability concerns arise

Engineering Contradiction:

Improvetemperature measurementVSAvoiddevice complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The power semiconductor device itself is used to determine its own temperature by monitoring its reverse current characteristics, eliminating the need for separate temperature sensors. The device serves its own measurement function through its inherent electrical properties.

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

Physical temperature sensors (mechanical/thermal components) are replaced by electrical measurement methods that use the semiconductor's own electrical characteristics (reverse current) to infer temperature, substituting a thermal measurement system with an electrical one.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Ease of operation

If temperature-dependent electrical semiconductor properties are used to determine temperature, then non-contact temperature measurement is achieved, but measurement precision is insufficient

Engineering Contradiction:

Improvetemperature measurement methodVSAvoidtemperature determination accuracy

Core Design Contradiction:

Ease of operationVSMeasurement precision

Solution Approach 1:

The method utilizes changes in electrical parameters (reverse current characteristics) with temperature, specifically monitoring how the reverse current waveform changes as temperature varies, to accurately determine the temperature of the depletion region.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The reverse current acts as an intermediary parameter that indirectly reveals the temperature of the depletion region. By measuring the reverse current characteristics, the temperature information is obtained without direct thermal contact, improving both ease of operation and precision.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Reliability

If existing temperature determination methods are used, then temperature monitoring is provided, but reliability of temperature determination is not sufficient

Engineering Contradiction:

Improvetemperature monitoring capabilityVSAvoidtemperature determination reliability

Core Design Contradiction:

ReliabilityVSMeasurement precision

Solution Approach 1:

The method continuously monitors the reverse current characteristics and uses this feedback to accurately determine temperature, enabling reliable real-time temperature monitoring of the power semiconductor device during operation.

Inventive Principle:

Principle #23Feedback

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

Provides a reliable and accurate method for determining the temperature of the depletion region of diodes in power electronics, enhancing protection against thermal overload by improving the precision of temperature measurement.

Implementation Method 1

a temperature of a depletion region of the second diode is determined as a function of this difference

Methodology Applied

Scientific EffectTemperature-dependent electrical semiconductor property:

Data Source

PatentEP3948193B1Method and device for determining the temperature of a power electronics unit

Publication Date: 2025.12.17 ROBERT BOSCH GMBH

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AI summary

The invention relates to a method for determining the temperature of a power electronics unit (1) which has at least one commutator circuit (2) and a load (3) which is powered/can be powered by the commutator circuit (2). The commutator circuit (2) comprises a first semiconductor switch device (4), which has a first semiconductor switch (5) and optionally a first diode (6), and a second diode (9), wherein the second diode (9) and the load (3) are connected in parallel to the first semiconductor switch (5). The curve of an electric current flowing through the second diode (9) is monitored at least when a reverse current is produced in the second diode (9) after the semiconductor switch (5) has been switched so as to become conductive. On the basis of the current curve, the temperature of a barrier layer of the second diode (9) is determined. A difference between a current value of a circuit current flowing through the commutator circuit (2) and an extremal current value {Imax) produced by the reverse current is ascertained on the basis of the current curve, and the temperature of the barrier layer of the second diode (9) is determined on the basis of the difference.