Active Discharging Module for Electric Car DC-Link Safety

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Solution Overview

Problem

Existing electric car systems face safety risks due to the failure of discharging modules to discharge DC-link capacitors in case of power failure or control module malfunctioning, which can lead to unsafe power levels for drivers and maintenance crews.

Innovation Solution

An active discharging module is introduced, comprising a discharging subcircuit connected in parallel with the DC-link capacitor, featuring a power switching transistor and a first switch that can automatically turn on and off to discharge the capacitor without an independent control module, ensuring safe power levels even in power failure scenarios.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a control module is used to control the discharging module, then the discharging function can be controlled, but the system becomes vulnerable to control module malfunctioning which prevents discharging

Engineering Contradiction:

Improvedischarging reliabilityVSAvoidcontrol module dependency

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The discharging module is designed to automatically activate when the contactor opens, without requiring control signals from the control module. The discharging transistor's gate is directly connected to the contactor, enabling the system to self-regulate the discharging process based on the contactor state, thereby eliminating control module dependency while maintaining reliability

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

Instead of using active control signals to enable discharging, the invention inverts the logic by using the contactor's open state (a passive condition) to automatically trigger discharging. This inversion ensures that discharging occurs automatically when the main power connection is broken, preventing the scenario where control module failure prevents discharging

Inventive Principle:

Principle #13The other way round (Inversion)

2Reliability

If the discharging module is activated after power failure, then safety can be maintained, but the response time may be delayed

Engineering Contradiction:

Improvesafety assuranceVSAvoiddischarging response time

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The discharging circuit is pre-configured with the discharging transistor's gate directly connected to the contactor, so that the discharging path is ready to activate immediately when the contactor opens. This preliminary arrangement eliminates any delay associated with control module processing or power failure detection, as the discharging action is mechanically coupled to the contactor operation

Inventive Principle:

Principle #10Preliminary action

3Device complexity

If an independent control module is eliminated, then the system becomes simpler and more reliable, but the automatic discharging function must be built into the circuit design

Engineering Contradiction:

Improvecontrol module countVSAvoidcircuit design complexity

Core Design Contradiction:

Device complexityVSEase of manufacture

Solution Approach 1:

The discharging control function is merged with the contactor circuit by directly connecting the discharging transistor's gate to the contactor. This integration eliminates the need for a separate control module and its associated control wiring, reducing overall system complexity while maintaining the automatic discharging function through the unified contactor-based control mechanism

Inventive Principle:

Principle #5Merging (Combining)

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

The active discharging module effectively and automatically discharges the DC-link capacitor, ensuring personal safety by eliminating the need for a separate control module and maintaining safe power levels during system malfunctions or power losses.

Implementation Method 1

said discharging resistor being used for absorbing the discharging current released via said discharging subcircuit from said DC-link capacitor

Methodology Applied

Scientific EffectJoule heating: Joule Heating

Data Source

PatentUS11318843B2Electric car, active discharging module, driving apparatus and electric drive system thereof

Publication Date: 2022.05.03 NIO CO LTD

AI summary

The present application relates to an electric car and an active discharging module, a driving apparatus, and an electric drive system thereof. said active discharging module comprises a discharging subcircuit, which is connected in parallel with the DC-link capacitor of the electric car, and a first switch, which is connected to an actuating apparatus of the electric car and the discharging subcircuit respectively. The discharging subcircuit comprises a discharging resistor and a power switching transistor which are connected in series, wherein the first switch may turn off the power switching transistor after the actuating apparatus is turned on, and turn on the power switching transistor after the actuating apparatus is turned off. Said driving apparatus comprises any one of the above active discharging modules. Said electric drive system comprises any one of the above driving apparatuses. Said electric car comprises any one of the above electric drive system.