Semiconductor Pre-Charge Circuit for DC Bus Braking Energy

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Existing power converters face challenges in efficiently pre-charging capacitive networks and managing braking energy, particularly when using active front ends, which can lead to size and reliability issues due to the use of electromechanical contactors and parasitic inductance, and cannot handle reverse power flow without causing faults.

Innovation Solution

A pre-charge circuit using controllable semiconductor switches and pre-charge impedance, combined with a braking resistance assembly, that eliminates electromechanical contactors and manages energy dissipation, allowing for efficient pre-charging and reverse power handling without contactor-related issues.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If electromechanical contactors are used for pre-charging capacitive networks, then pre-charge function is achieved, but device size increases and reliability decreases due to parasitic inductance and contactor failure risks

Engineering Contradiction:

Improvepre-charge reliabilityVSAvoidcontactor structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent replaces electromechanical contactors with controllable semiconductor switches (such as IGBTs or MOSFETs) that have no moving parts. This substitution eliminates mechanical wear, contact resistance, and parasitic inductance issues inherent in contactor-based systems, thereby improving reliability while reducing device complexity.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent changes the switching mechanism from mechanical (contactor) to solid-state semiconductor devices. This parameter change enables precise control of the pre-charge process, eliminates contactor-related failures, and reduces parasitic inductance, directly addressing the reliability and complexity contradictions.

Inventive Principle:

Principle #35Parameter changes

2Productivity

If active front ends are used for power conversion, then power control efficiency is improved, but the system cannot handle reverse power flow without causing faults

Engineering Contradiction:

Improvepower conversion efficiencyVSAvoidreverse power flow handling

Core Design Contradiction:

ProductivityVSAdaptability or versatility

Solution Approach 1:

The patent designs the pre-charge circuit with controllable semiconductor switches that can operate bidirectionally. These switches serve dual functions: enabling pre-charge operation during startup and handling reverse power flow during regenerative braking or motor generation modes. This multi-functionality allows the Active Front End to efficiently manage both forward power conversion and reverse power flow without faults.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The patent implements dynamic control of semiconductor switches that can adapt their operating state based on power flow direction. The switches can be controlled to conduct current in either direction, enabling the system to dynamically respond to both motoring and generating modes, thereby achieving both high efficiency and versatility.

Inventive Principle:

Principle #15Dynamics

3Ease of manufacture

If traditional pre-charge circuits are used, then pre-charging is achieved, but space is wasted and cost increases due to additional components

Engineering Contradiction:

Improvemanufacturing costVSAvoidcircuit space

Core Design Contradiction:

Ease of manufactureVSVolume of moving object

Solution Approach 1:

The patent merges the pre-charge function with the main power conversion circuit by using the same controllable semiconductor switches for both pre-charging and power conversion operations. This integration eliminates the need for separate pre-charge contactors and associated components, thereby reducing both manufacturing cost and circuit space while maintaining ease of manufacture through standardized semiconductor devices.

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 solution provides reliable, space-saving, and cost-effective pre-charging with reduced failure rates, while enabling power converters to handle reverse power flow and fault conditions, improving operational efficiency and safety.

Implementation Method 1

a pre-charge impedance in parallel with the one or more pre-charge switches

Methodology Applied

Scientific EffectOhm's Law: Ohm's Law

Implementation Method 2

a braking resistance assembly electrically connected to the pre-charge circuit. The braking resistance assembly is configured to be electrically connected to the DC bus during the braking mode

Methodology Applied

Scientific EffectJoule Heating: Joule Heating

Data Source

PatentUS20260005620A1Pre-charge circuit and braking energy management for a power converter

Publication Date: 2026.01.01 EATON INTELLIGENT POWER LTD

AI summary

A system includes: a direct current (DC) bus; a converter connected to the DC bus; a capacitive network electrically connected to the DC bus; and an energy management apparatus configured to pre-charge the capacitive network in a pre-charge mode and to dissipate energy from the DC bus in a braking mode. The energy management apparatus includes: a pre-charge circuit configured to pre-charge the capacitive network, the pre-charge circuit including: one or more pre-charge switches, each pre-charge switch being a controllable semiconductor switch; and a pre-charge impedance in parallel with the one or more pre-charge switches; and a braking resistance assembly electrically connected to the pre-charge circuit. The braking resistance assembly is configured to be electrically connected to the DC bus during the braking mode.