Vehicle Inverter Ground Path to Prevent Relay Hindrance

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

The existing vehicle inverter devices face issues where the capacitor in the filter circuit is charged before the relay is switched to the on-state, potentially hindering the relay's operation.

Innovation Solution

A vehicle inverter device configuration where the control circuit causes only the lower arm switching element to be in the on-state, and electrically connects the control circuit and the negative bus bar through the upper arm ground line when DC power is supplied from a low-voltage source, preventing the filter capacitor from being charged by leakage current.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the relay is switched to the on-state before the capacitor is discharged, then the DC electric power can be supplied to the inverter device, but the relay operation may be hindered due to the charged capacitor

Engineering Contradiction:

Improverelay operation reliabilityVSAvoidrelay switching operation

Core Design Contradiction:

ReliabilityVSEase of operation

Solution Approach 1:

The control circuit performs preliminary discharge of the capacitor through the lower arm switching element before the relay is switched to the on-state. This preliminary action ensures the capacitor is discharged, preventing relay operation hindrance while enabling subsequent power supply

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

Instead of switching the relay on first and then discharging the capacitor, the invention inverts the sequence by discharging the capacitor first through the lower arm switching element, then switching the relay on. This reversed sequence eliminates the harmful effect of charged capacitor on relay operation

Inventive Principle:

Principle #13The other way round (Inversion)

2Reliability

If the capacitor of the filter circuit is charged before relay switching, then the filter circuit can function, but the relay switching operation is hindered

Engineering Contradiction:

Improvefilter circuit functionVSAvoidrelay switching operation

Core Design Contradiction:

ReliabilityVSEase of operation

Solution Approach 1:

The control circuit performs preliminary discharge of the capacitor through the lower arm switching element before relay switching. This ensures the capacitor is in a discharged state, allowing relay switching to proceed smoothly while maintaining filter circuit functionality

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The invention inverts the conventional sequence by discharging the capacitor first through the lower arm switching element, then switching the relay on. This reversed sequence resolves the conflict between filter circuit function and relay switching operation

Inventive Principle:

Principle #13The other way round (Inversion)

Data Source

PatentUS11745590B2Vehicle inverter device and vehicle fluid machine

Publication Date: 2023.09.05 TOYOTA INDUSTRIES CORP

AI summary

A vehicle inverter device for driving an electric motor using a vehicle electric power source. The vehicle inverter device includes an input terminal, a filter circuit including a capacitor, an inverter circuit, a positive bus bar, a negative bus bar, a control circuit, an upper arm ground line, and a low voltage electric power source circuit. The control circuit causes only a lower arm switching element to be in an on-state and electrically connects the control circuit and the negative bus bar through the upper arm ground line when a direct current electric power is supplied from the low-voltage electric power source circuit under a condition where a direct current electric power is not inputted to the input terminal.