EV Charging Protection Circuit for AC/DC Voltage Mixing
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Solution Overview
Problem
Current battery junction boxes in electric vehicles are susceptible to inadvertent mixing of AC and DC electrical power, which can lead to potential damage due to improper handling of high-voltage DC batteries and external AC charging stations.
Innovation Solution
A protection circuit comprising an analog-to-digital converter, control circuit, and processor that digitizes high-voltage signals to determine if they represent AC or DC voltage, controlling contactors to prevent mixing by opening or closing them accordingly, using hardware and software components for continuous monitoring and redundancy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If AC and DC charging paths are combined in a single battery junction box, then charging system integration is improved, but risk of voltage mixing increases
Solution Approach 1:
The battery junction box is segmented into separate AC and DC charging paths with distinct contactors (AC contactor and DC contactor). Each path has its own protection circuitry and control logic, physically separating the AC and DC domains to prevent inadvertent mixing while maintaining integrated charging capability.
Solution Approach 2:
A processor acts as an intermediary between the charging system and contactors, continuously monitoring voltage signals and controlling contactor operation. The processor receives voltage type detection signals, determines whether AC or DC voltage is present, and asserts or negates control signals to appropriate contactors to prevent voltage mixing.
2Reliability
If continuous voltage monitoring is implemented, then protection reliability is improved, but system complexity increases
Solution Approach 1:
The processor performs multiple functions: it monitors voltage signals, determines voltage type (AC or DC), controls both AC and DC contactors, and coordinates with the control circuit. This multi-functionality reduces the need for separate dedicated circuits for each function, maintaining reliability while managing system complexity.
Solution Approach 2:
The protection system uses the existing voltage sensing infrastructure to provide self-monitoring and self-protection. The processor continuously samples voltage signals and automatically adjusts contactor states based on detected voltage type, eliminating the need for external monitoring equipment or manual intervention.
3Measurement precision
If hardware and software components are used for monitoring, then detection accuracy is improved, but manufacturing complexity increases
Solution Approach 1:
An analog-to-digital converter serves as an intermediary between the analog voltage sensing circuitry and the digital processor. This converter accurately translates analog voltage signals into digital values for precise AC/DC voltage type determination by the processor, maintaining detection accuracy while enabling digital processing.
Solution Approach 2:
The protection circuit combines hardware voltage sensing components with software-based voltage type determination algorithms in the processor. The hardware provides continuous analog voltage monitoring while the software analyzes the digitized signals to determine voltage type, creating a hybrid system that leverages the strengths of both approaches.
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
Effectively prevents the mixing of AC and DC voltages within electric vehicles, safeguarding the vehicle and charging infrastructure by ensuring appropriate contactor operation based on voltage type detection.
Implementation Method 1
The analog-to-digital converter is operational to generate a sequence of digital values by digitizing a high-voltage signal
Implementation Method 2
the protection circuit includes a bandpass filter circuit connected between the charging socket and the analog-to-digital converter
Implementation Method 3
the protection circuit includes a capacitive coupler circuit between the charging socket and the bandpass filter circuit
Data Source
AI summary
A protection circuit includes an analog-to-digital converter, a processor, and a control circuit. The analog-to-digital converter generates a sequence of digital values by digitizing a high-voltage signal within a high-voltage area of a vehicle. The control circuit controls multiple contactors coupled to the charging socket in response to a configuration signal. The processor determines if the sequence of digital values represents one of an alternating voltage and a steady-state voltage, asserts the configuration signal to command the control circuit to close a pair of DC contactors in response to the sequence of digital values representing the steady-state voltage, and negates the configuration signal to command the control circuit to open the pair of DC contactors in response to the sequence of digital values representing the alternating voltage to prevent a mixture of the alternating voltage and the steady-state voltage in the high-voltage area.