AC-DC Converter Discharge Path Using Internal Switching Components

Solution Overview

Problem

Existing on-board chargers for electric vehicles face challenges in efficiently and safely discharging energy from capacitors after charging, with passive discharging being slow and active discharging requiring additional circuits, increasing complexity and cost.

Innovation Solution

A single-phase and three-phase compatible AC-DC conversion circuit using internal power switching components and a pre-charge resistor, with pulse width modulation to optimize duty cycle, providing a discharge path without additional components.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If passive discharging is used with dummy load, then no additional circuits are required, but discharge time becomes quite long

Engineering Contradiction:

Improvecircuit complexityVSAvoiddischarge time

Core Design Contradiction:

Device complexityVSLoss of time

Solution Approach 1:

The system dynamically switches between passive discharging mode (using dummy load) and active discharging mode (using power switching components) based on real-time voltage detection. When capacitor voltage exceeds a threshold, the control unit activates the active discharging path, enabling the system to adapt its discharging characteristics rather than being fixed in one mode.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The power switching components and dummy load serve dual functions: during normal operation they perform their primary power conversion role, and during discharge they form an active discharging circuit. This multi-functionality eliminates the need for dedicated discharge components while achieving fast discharge performance.

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Loss of time

If active discharging is used with additional parallel circuit, then discharge time is shortened, but circuit cost and complexity increase

Engineering Contradiction:

Improvedischarge timeVSAvoidcircuit complexity

Core Design Contradiction:

Loss of timeVSDevice complexity

Solution Approach 1:

The power switching components and dummy load serve dual functions: during normal operation they perform their primary power conversion role, and during discharge they form an active discharging circuit. This multi-functionality eliminates the need for dedicated discharge components while achieving fast discharge performance.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The system uses its own internal power switching components and existing dummy load to create the discharging path, rather than relying on external or additional dedicated discharge components. The control unit orchestrates these existing components to serve the discharge function, making the system self-sufficient.

Inventive Principle:

Principle #25Self-service

3Loss of time

If active discharging is used with additional parallel circuit, then discharge time is shortened, but circuit cost increases

Engineering Contradiction:

Improvedischarge timeVSAvoidcircuit cost

Core Design Contradiction:

Loss of timeVSEase of manufacture

Solution Approach 1:

The power switching components and dummy load serve dual functions: during normal operation they perform their primary power conversion role, and during discharge they form an active discharging circuit. This multi-functionality eliminates the need for dedicated discharge components while achieving fast discharge performance.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The discharging function is merged with the existing power conversion circuitry rather than being implemented as a separate system. The same power switching components, capacitors, and dummy load that constitute the normal operating circuit are combined to perform both power conversion and active discharging functions.

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

Enables efficient and safe active discharging of capacitors without additional circuit components, reducing current stress and improving system reliability, while maintaining compatibility with both single-phase and three-phase charging conditions.

Implementation Method 1

the capacitor assembly discharges through the pre-charge resistor on the discharge path

Methodology Applied

Scientific EffectJoule heating: Joule Heating

Data Source

PatentUS11569754B2Single-phase and three-phase compatible AC-DC conversion circuit and method of controlling charge and discharge thereof

Publication Date: 2023.01.31 DELTA ELECTRONICS INC(CN)

AI summary

A single-phase and three-phase compatible AC-DC conversion circuit includes a first switching component, a second switching component, a third switching component, three switch bridge arms, a fourth switching component, a pre-charge resistor, a capacitor assembly, and a control unit. Each switch bridge arm has an upper switch and a lower switch connected in series. The fourth switching component is coupled between a first phase of a three-phase power source and a common-connected node of the switch bridge arm corresponding to a second phase of the three-phase power source. The control unit turns on the fourth switching component, turns on the upper switch coupled to the first switching component, and turns on the lower switch coupled to the fourth switching component to provide a discharge path so that the capacitor assembly discharges through the pre-charge resistor on the discharge path.