PFC Circulating Current Control for Fast DC Link Discharge

Solution Overview

Problem

Existing battery charging systems in electric vehicles require additional discharge circuits for safety, increasing system size and cost, and there is a need for a more efficient method to manage charging voltage to prevent fire risks.

Innovation Solution

A charging voltage control device using a power factor correction circuit, relay, link capacitor, and controller to generate and control circulating currents for safe and rapid discharge of DC voltage without additional circuits.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Speed

If an additional discharge circuit is installed for forced discharge, then fast discharge capability is improved, but system size and cost increase

Engineering Contradiction:

Improvedischarge speedVSAvoidsystem size

Core Design Contradiction:

SpeedVSDevice complexity

Solution Approach 1:

The patent merges the discharge function with the existing power factor correction circuit by enabling it to operate in reverse mode. The same circuit components (switching elements, link capacitor, control unit) are utilized for both power factor correction during charging and forced discharge during emergency situations, eliminating the need for a separate discharge circuit and reducing system size while maintaining fast discharge capability

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The power factor correction circuit is designed to perform multiple functions: it operates normally for power factor correction during charging, and can be switched to reverse mode to perform forced discharge when needed. This multi-functionality allows the single circuit to replace what would traditionally require separate dedicated circuits for both charging and emergency discharge operations

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Speed

If an additional discharge circuit is installed for forced discharge, then fast discharge capability is improved, but system cost increases

Engineering Contradiction:

Improvedischarge speedVSAvoidsystem cost

Core Design Contradiction:

SpeedVSEase of manufacture

Solution Approach 1:

The patent merges the discharge function with the existing power factor correction circuit by enabling it to operate in reverse mode. The same circuit components (switching elements, link capacitor, control unit) are utilized for both power factor correction during charging and forced discharge during emergency situations, eliminating the need for a separate discharge circuit and reducing system size while maintaining fast discharge capability

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The power factor correction circuit is designed to perform multiple functions: it operates normally for power factor correction during charging, and can be switched to reverse mode to perform forced discharge when needed. This multi-functionality allows the single circuit to replace what would traditionally require separate dedicated circuits for both charging and emergency discharge operations

Inventive Principle:

Principle #6Universality (Multi-functionality)

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 quick and controlled discharge of charging voltage, reducing fire risks and system complexity by utilizing circulating currents to consume power through passive elements, thus ensuring safety and efficiency.

Implementation Method 1

a power factor correction circuit converting a multi-phase alternating current (AC) voltage into a direct current (DC) voltage based on an operation of a plurality of switching elements

Methodology Applied

Scientific EffectElectromagnetic induction: Electromagnetic Induction

Implementation Method 2

a link capacitor to which a DC voltage converted by the power factor correction circuit is applied

Methodology Applied

Scientific EffectCapacitance: Capacitance

Implementation Method 3

discharge the DC voltage through power generated based on the circulation directions of the two or more circulating currents

Methodology Applied

Scientific EffectJoule heating: Joule Heating

Data Source

PatentUS20250326312A1Device and system for controlling charging voltage using circulating current

Publication Date: 2025.10.23 HL MANDO CORP

AI summary

The disclosure relates to a technology for controlling charging current using a circulating current and provides a charging voltage control device and system controlling a circulating current and comprising a power factor correction circuit converting a multi-phase alternating current (AC) voltage into a direct current (DC) voltage based on an operation of switching elements, a relay including at least one switch connected to the power factor correction circuit to control a current applied to each phase and a neutral line, a link capacitor to which a DC voltage converted by the power factor correction circuit is applied, and a controller generating circulating currents by controlling the operation of switching elements and the at least one switch when the link capacitor is required to be discharged and controlling circulation directions of the circulating currents to discharge the DC voltage through power generated based on the circulation directions of the circulating currents.