Semiconductor Switching Control Circuit for Ignition Systems

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Solution Overview

Problem

The existing ignition systems for internal combustion engines face issues with erroneous temperature detection due to L load noise, leading to unnecessary overheat protection in semiconductor switching elements, which can result in inadequate protection during abnormal heat generation.

Innovation Solution

A control circuit for semiconductor switching elements that includes an overheat detection circuit, a current detection circuit, and an interruption circuit, which generates signals based on temperature and current thresholds to accurately determine when to turn off the semiconductor switching element, preventing unnecessary overheat protection.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If temperature detection is performed using a diode output signal, then overheat protection can be provided, but L load noise causes erroneous temperature detection leading to unnecessary overheat protection

Engineering Contradiction:

Improveoverheat protection reliabilityVSAvoidtemperature detection precision

Core Design Contradiction:

ReliabilityVSMeasurement precision

Solution Approach 1:

The patent introduces a current detection circuit as an intermediary to verify whether the semiconductor switching element is actually operating before triggering overheat protection. The interruption circuit acts as a mediator that requires both temperature and current conditions to be met before turning off the switching element, preventing false positives from L load noise.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If overheat protection is triggered based on diode output, then semiconductor switching element is protected, but unnecessary protection occurs due to L load noise

Engineering Contradiction:

Improvesemiconductor protectionVSAvoidignition system operation continuity

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

The patent implements a feedback mechanism where the current detection circuit continuously monitors the operating state and provides feedback to the interruption circuit. This feedback loop ensures that overheat protection is only activated when both temperature thresholds and current flow conditions are satisfied, preventing unnecessary interruptions of the ignition system.

Inventive Principle:

Principle #23Feedback

3Measurement precision

If temperature detection is performed continuously, then abnormal heat conditions can be detected, but L load noise during switching causes false detection

Engineering Contradiction:

Improvetemperature detection accuracyVSAvoidL load noise interference

Core Design Contradiction:

Measurement precisionVSObject-affected harmful factors

Solution Approach 1:

The patent applies preliminary action by requiring current detection to occur before triggering overheat protection. The current detection circuit prepares the condition verification in advance, ensuring that temperature readings are only acted upon when the switching element is actually conducting current, thus preempting false detections from L load noise during switching transitions.

Inventive Principle:

Principle #10Preliminary 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 solution ensures that the semiconductor switching element is only turned off when both a predetermined temperature and current threshold are met, effectively preventing erroneous overheat protection and ensuring timely intervention during abnormal heat conditions.

Implementation Method 1

the temperature of the semiconductor switching element is detected using a current signal obtained through a diode by utilizing temperature characteristic of the diode

Methodology Applied

Scientific EffectTemperature characteristic of diode:

Implementation Method 2

a displacement current (so-called L load noise) is generated in the diode in association with the turning-on operation of the semiconductor switching element due to the presence of the induction load

Methodology Applied

Scientific EffectDisplacement current generation:

Data Source

PatentUS10128735B2Control circuit for semiconductor switching element, and semiconductor device

Publication Date: 2018.11.13 MITSUBISHI ELECTRIC CORP

AI summary

A control circuit for a semiconductor switching element includes a control terminal, a main electrode terminal, and a current sensing terminal, and controls the semiconductor switching element including a diode connected to the main electrode terminal or the current sensing terminal. The control circuit includes an overheat detection circuit, a current detection circuit, and an interruption circuit. The overheat detection circuit outputs an overheat detection signal when a temperature detected based on an output of the diode is equal to or higher than a predetermined set temperature. The current detection circuit outputs a current detection signal when an output value of the current sensing terminal is equal to or greater than a predetermined set current value. The interruption circuit turns off the semiconductor switching element when both the overheat detection signal from the overheat detection circuit and the current detection signal from the current detection circuit are input.