Decoupling Circuit for EV Battery Charging Without Input Insulation

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Solution Overview

Problem

Existing charging devices for in-vehicle batteries fail to properly charge the battery when the input and output terminals of the charging circuit are not insulated, as current flows from the vehicle body to the earth through the coupling capacitor, preventing charging due to potential earth faults.

Innovation Solution

A charging device incorporating an insulation resistance detecting circuit, a leak current detecting circuit, and a decoupling circuit that decouples the insulation resistance detecting circuit from the battery or vehicle body during charging, preventing current flow through the coupling capacitor and allowing charging even without insulation between the input and output terminals.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If the charging circuit converts alternating current to direct current without insulating the input and output terminals, then charging efficiency is improved, but current flows from the vehicle body to the earth through the coupling capacitor, preventing proper charging

Engineering Contradiction:

Improvecharging efficiencyVSAvoidcharging stability

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The patent introduces a decoupling circuit as an intermediary component between the insulation resistance detection circuit and the charging circuit. This decoupling circuit includes a switch that can disconnect the coupling capacitor from the detection circuit during charging operations, thereby mediating between the need for continuous insulation monitoring and the need for stable charging without false earth fault detections

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent implements dynamic switching of the decoupling circuit based on the charging state. The switch in the decoupling circuit is controlled to disconnect during charging operations and connect during insulation resistance detection phases, making the system configuration dynamic rather than static to accommodate different operational requirements

Inventive Principle:

Principle #15Dynamics

2Reliability

If the insulation resistance detecting circuit remains connected during charging, then insulation monitoring is maintained, but false earth fault detection occurs due to current flow through the coupling capacitor

Engineering Contradiction:

Improveinsulation monitoring capabilityVSAvoidfalse earth fault detection

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent implements periodic switching between insulation resistance detection mode and charging mode. The decoupling circuit switch is periodically opened during charging to prevent false earth fault detection, and closed during insulation resistance detection phases, creating a periodic operational pattern that alternates between these two functions

Inventive Principle:

Principle #19Periodic action

Solution Approach 2:

The patent extracts the coupling capacitor from the active circuit path during charging operations by opening the switch in the decoupling circuit. This removes the source of the false earth fault detection signal from the circuit during charging, eliminating the harmful effect while preserving the insulation monitoring capability when needed

Inventive Principle:

Principle #2Taking out (Extraction)

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 proper charging of the battery by reducing the likelihood of current flow through the coupling capacitor, ensuring safe and efficient charging even when the charging circuit's terminals are not insulated, while also detecting leak currents to prevent insufficient insulation issues.

Implementation Method 1

The insulation resistance detecting circuit includes a coupling capacitor. The insulation resistance detecting circuit is disposed between the battery and a vehicle body for detecting an insulation resistance between the battery and the vehicle body.

Methodology Applied

Scientific EffectCapacitance: Capacitance

Implementation Method 2

The decoupling circuit decouples the insulation resistance detecting circuit from one of the battery and the vehicle body during a charging of the battery

Methodology Applied

Scientific EffectElectrical insulation:

Data Source

PatentUS9350179B2Charging device

Publication Date: 2016.05.24 DENSO CORP

AI summary

A charging device for a battery of a vehicle includes an insulation resistance detecting circuit, a charging circuit, a leak current detecting circuit and a decoupling circuit. The insulation resistance detecting circuit includes a coupling capacitor, and is disposed between the battery and a vehicle body for detecting an insulation resistance between the battery and the vehicle body. The charging circuit converts an alternating current supplied from an alternating current source into a direct current and charges the battery in a state without insulting the input terminal and the output terminal and in a state where the vehicle body is coupled to an earth. The leak current detecting circuit detects a leak current between the charging circuit and the earth. The decoupling circuit decouples the insulation resistance detecting circuit from one of the battery and the vehicle body during a charging of the battery.