Charging Interface Circuit With Two-Stage Surge and EMC Protection
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Solution Overview
Problem
Charging devices for new energy electric vehicles face inaccuracies in electric quantity metering and pollution of the power grid due to excessive input surge current, lacking effective EMC protection solutions.
Innovation Solution
A charging device interface circuit is designed with a two-stage differential mode protection unit, common mode protection unit, and lightning protection unit, incorporating varistors, inductors, capacitors, and a gas discharge tube to reduce surge current and enhance EMC protection, preventing differential mode, common mode interference, and lightning strikes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If no protective design is added to the charging device interface, then the device complexity is low, but the input surge current becomes excessively high causing inaccurate electric quantity metering and power grid pollution
Solution Approach 1:
The protection unit is divided into two distinct stages: a first-stage differential mode protection unit and a second-stage common mode protection unit. Each stage addresses specific types of surge currents independently, allowing for targeted protection without excessive complexity. The segmentation enables precise control over different surge current components while maintaining a manageable overall structure.
Solution Approach 2:
A protection unit is introduced as an intermediary component between the AC input interface and the internal circuitry. This intermediary structure includes differential mode and common mode protection units that filter and suppress surge currents before they reach the sensitive metering and power conversion components, thereby protecting the system without requiring complete redesign of the entire interface.
2Object-affected harmful factors
If a protective design is added to reduce surge current, then the electric quantity metering accuracy improves, but the device complexity increases
Solution Approach 1:
Different protection mechanisms are applied to different modes of surge current: differential mode protection handles line-to-neutral surges, while common mode protection handles line-to-ground surges. Each protection unit is optimized for its specific function with appropriate components (varistors, inductors, capacitors), allowing localized optimization without requiring the entire system to be overly complex.
Solution Approach 2:
The protection unit combines multiple types of protective components including varistors (MOV1, MOV2), inductors (L1, L2), and capacitors (CX1, CX2, CY1, CY2) working together in a composite structure. This composite approach leverages the complementary characteristics of different components to achieve comprehensive surge current suppression across multiple modes simultaneously.
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 effectively reduces input surge current, enhances EMC protection, and improves the working performance of charging devices by preventing interference and ensuring accurate electric quantity metering, thereby reducing pollution to the power grid.
Implementation Method 1
the first-stage differential mode protection unit includes a large through-current varistor MOV1; and the second-stage differential mode protection unit includes a small through-current varistor MOV2
Implementation Method 2
a first end of the third varistor MOV3 and a first end of the fourth varistor MOV4 are connected to a first end of the ceramic gas discharge tube GDT1; and a second end of the ceramic gas discharge tube GDT1 is grounded
Data Source
AI summary
A charging device interface circuit and a charging device, and the charging device interface circuit includes an AC input interface, a differential mode protection unit, a common mode protection unit and an AC/DC power conversion unit; the AC input interface is configured to be connected to alternating current; the differential mode protection unit includes a first-stage differential mode protection unit and a second-stage differential mode protection unit; the first-stage differential mode protection unit is connected to the AC input interface; the second-stage differential mode protection unit is connected to the first-stage differential mode protection unit; the common mode protection unit is connected in parallel with the second-stage differential-mode protection unit; an AC end of the AC/DC power conversion unit is connected to the common mode protection unit; and a DC end of the AC/DC power conversion unit is connected to an apparatus to be charged.