Neutral Conductor Precharge Circuit for AC Charging Devices
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Solution Overview
Problem
Existing AC charging devices for motor vehicles require multiple precharge circuits, one for each phase conductor, which complicates the design and increases costs, as they need to precharge smoothing capacitors to the mains voltage level without abrupt voltage breakdown.
Innovation Solution
The precharge circuit is arranged in the neutral conductor, connecting it to all phase conductors through a cross-connection line, allowing a single precharge circuit to precharge multiple smoothing capacitors, simplifying the design and eliminating the need for additional precharge circuits in phase conductors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a precharge circuit is arranged in each phase conductor, then each smoothing capacitor can be precharged independently, but the device complexity and component quantity increase
Solution Approach 1:
The patent merges three separate precharge circuits (one for each phase conductor) into a single precharge circuit located in the neutral conductor. This single precharge circuit uses a precharge resistor connected to all three smoothing capacitors through the rectifier, thereby precharging all capacitors simultaneously. This merging reduces the number of precharge circuits from three to one, simplifying the overall device structure while maintaining the essential precharging function.
Solution Approach 2:
The neutral conductor is given a dual function: it serves both as the standard neutral return path and as the carrier for the precharge circuit. By placing the precharge circuit in the neutral conductor, the same conductor performs two functions simultaneously, eliminating the need for separate precharge circuits in each phase conductor and reducing overall device complexity.
2Reliability
If multiple precharge circuits are used, then each phase can be precharged independently, but the manufacturing cost increases
Solution Approach 1:
The patent combines multiple precharge circuits into a single shared precharge circuit in the neutral conductor. This reduces the total number of precharge resistors and associated components from three to one, directly lowering material costs and assembly complexity while maintaining the voltage breakdown prevention function for all phase conductors.
Solution Approach 2:
The neutral conductor-based precharge circuit serves all three phase conductors simultaneously, making the precharge function universal rather than individual. This multi-functionality reduces the total component count and manufacturing steps required, thereby reducing production costs while achieving the same reliability outcome.
3Reliability
If precharge circuits are arranged in phase conductors, then the precharging function is distributed, but the device design becomes more complex
Solution Approach 1:
The patent consolidates the precharging function from three distributed circuits in phase conductors into a single centralized precharge circuit in the neutral conductor. This centralization simplifies the circuit arrangement by reducing the number of separate precharge paths from three to one, making the overall device design less complex while maintaining effective precharging of all smoothing capacitors.
Solution Approach 2:
The neutral conductor acts as an intermediary that connects the single precharge circuit to all three phase conductors through the rectifier. This intermediary role allows one precharge circuit to serve multiple phases without requiring direct integration into each phase conductor, thereby simplifying the overall circuit arrangement while maintaining functional distribution.
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
This configuration simplifies the AC charging device design, reduces the number of precharge circuits needed, and ensures safe operation by precharging all phases with a single circuit, enabling efficient energy transfer while avoiding voltage abruptness and reducing component costs.
Implementation Method 1
The precharge circuit in this case usually has just one precharge resistor in order to limit the current
Implementation Method 2
The smoothing capacitor reduces any residual ripple or an AC current component that remains after the AC current has been rectified
Implementation Method 3
The AC charging device is designed to receive AC current from a mains and (by rectifying the AC current) to output DC current
Data Source
AI summary
An alternating current (AC) charging device for a motor vehicle may include: a neutral conductor; a phase conductor; a rectifier; a smoothing capacitor electrically connected to the rectifier; a mains connection; a precharge circuit arranged between the mains connection and the smoothing capacitor, the precharge circuit precharging the smoothing capacitor; and a second phase conductor electrically connected to the phase conductor by a cross-connection line. The neutral conductor and the phase conductor are connected to the rectifier. The precharge circuit is disposed in the neutral conductor.