Single Precharge Circuit for Multi-Phase AC Charging
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Solution Overview
Problem
Existing AC charging devices for motor vehicles require separate precharge circuits for each phase, leading to complexity and increased costs due to the need for multiple precharge circuits and components.
Innovation Solution
The precharge circuit is arranged between the mains connection of a first phase conductor and the connection section, allowing for a single precharge circuit to serve multiple phases, eliminating the need for additional precharge circuits in other phase conductors or the neutral conductor, and utilizing a switchable precharge circuit with a transistor and precharge resistor to control the charging process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If separate precharge circuits are provided for all phases of the AC charging device, then each phase can be precharged independently, but the device complexity and component count increase
Solution Approach 1:
The single precharge circuit is designed to serve multiple phases through cross-connection lines. The precharge circuit connected to the first phase conductor can precharge smoothing capacitors in all phases by utilizing the cross-connection switches and lines, making the precharge circuit universal across all phases rather than having dedicated circuits for each phase.
Solution Approach 2:
Multiple precharge functions for different phases are merged into a single precharge circuit. The patent combines the precharge functionality that would otherwise require separate circuits for each phase into one shared circuit, reducing overall device complexity while maintaining precharge capability for all phases through the cross-connection network.
2Device complexity
If a single precharge circuit serves multiple phases, then device complexity is reduced, but the precharge circuit must handle multiple phase connections and control logic
Solution Approach 1:
The precharging process is segmented into phase-specific operations controlled by individual cross-connection switches. Each phase can be precharged independently by controlling its respective cross-connection switch, allowing the single precharge circuit to handle multiple phases through divided, manageable control steps rather than complex simultaneous control.
Solution Approach 2:
The cross-connection switches enable dynamic reconfiguration of the circuit topology to connect the single precharge circuit to different phases as needed. The system dynamically adapts its connection structure based on which phase needs precharging, providing flexibility in controlling a single circuit to serve multiple functions.
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 design simplifies the AC charging device, reduces component count, and allows safe operation with fewer precharge circuits, enabling efficient charging across multiple branches with a single phase conductor connection, while ensuring safe disconnection and voltage regulation.
Implementation Method 1
The precharge circuit in this case usually has only one precharge resistor, which limits the charging current before the actual charging process
Implementation Method 2
The smoothing capacitor reduces any residual ripple or an AC current component that remains after the AC current has been rectified. The smoothing capacitor absorbs (or short-circuits) AC voltage components
Implementation Method 3
The precharge circuit is in particular switchable, for example by way of a transistor that is connected in series with a precharge resistor of the precharge circuit
Data Source
AI summary
An AC charging device for a motor vehicle has a neutral conductor, at least one phase conductor, and at least one rectifier. The neutral conductor and the phase conductor are connected to the rectifier and the rectifier is furthermore electrically connected to at least one smoothing capacitor. The AC charging device includes a precharge circuit arranged between a mains connection of the AC charging device and the smoothing capacitor. The precharge circuit is designed to precharge the smoothing capacitor. The phase conductor, in a connection section, is connected to at least one further phase conductor of the AC charging device by way of a cross-connection line, which has a cross-connection switch for disconnecting the phase conductor and the further phase conductor. The precharge circuit is arranged between a mains connection of a first phase conductor of the phase conductors and the connection section.