On-Board Charger Capacitor Precharge for Soft-Start Current Suppression
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Solution Overview
Problem
The presence of a bus capacitor in on-board chargers (OBCs) of electric vehicles leads to large instantaneous currents when starting the charging process, potentially damaging the OBC, and the addition of a soft-start circuit to mitigate this increases circuit complexity and hinders miniaturization.
Innovation Solution
A charger that precharges a capacitor using battery energy to reach a threshold voltage close to the input voltage, allowing for soft-start without a dedicated soft-start circuit, thereby simplifying the circuit and facilitating miniaturization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a soft-start circuit is disposed in the OBC to reduce access current, then the instantaneous current damage is prevented, but the circuit complexity increases and miniaturization is hindered
Solution Approach 1:
The soft-start function is merged with the existing DC-DC conversion circuit by utilizing the first capacitor that is already part of the circuit. The capacitor performs both its original filtering function and the additional soft-start function, eliminating the need for a separate soft-start circuit and reducing overall circuit complexity.
Solution Approach 2:
The first capacitor in the DC-DC conversion circuit is given multiple functions: it serves as both a filtering capacitor for the charging electric energy and as a soft-start capacitor to limit instantaneous current. This multi-functionality approach eliminates the need for dedicated soft-start components.
2Stability of the object's composition
If a bus capacitor is disposed in the OBC to filter charging electric energy, then the filtering function is achieved, but large instantaneous current is generated at startup that can damage the OBC
Solution Approach 1:
The first capacitor is precharged to a first threshold voltage before the charging pile begins to output charging electric energy. This preliminary charging action ensures that when charging starts, the voltage difference between the capacitor and the charging source is minimized, thereby preventing large instantaneous current while maintaining the filtering function.
Solution Approach 2:
The control module monitors the voltage of the first capacitor and compares it with the first threshold voltage. When the capacitor voltage reaches the threshold, the control module sends indication information to the charging pile to start outputting charging electric energy. This feedback mechanism ensures optimal timing for charging initiation, preventing instantaneous current surges.
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 approach effectively suppresses instantaneous currents during charging, protecting the charger and enabling miniaturization by eliminating the need for a separate soft-start circuit.
Implementation Method 1
a bus capacitor is disposed in the OBC, and the bus capacitor may filter the charging electric energy transmitted in the OBC
Implementation Method 2
The DC-DC conversion circuit is respectively connected to a charging pile and a battery system. One end of the DC-DC conversion circuit is configured to receive charging electric energy output by the charging pile, and the other end of the DC-DC conversion circuit is configured to output converted charging electric energy to the battery system
Implementation Method 3
the charger provided in this application may precharge the first capacitor by using the battery electric energy provided by the battery system, so that the capacitance voltage of the first capacitor reaches a voltage that is close to the charging electric energy input to the DC-DC conversion circuit
Implementation Method 4
The rectifier circuit may convert the received charging electric energy from the alternating current electric energy into direct current electric energy, and output the converted charging electric energy to the DC-DC conversion circuit
Data Source
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AI summary
A charger, a soft-start method, an electric vehicle, and a charging system are disclosed. The charger includes a control module, a DC-DC conversion circuit, and a first capacitor. When the electric vehicle is charged, the control module in the charger may first control the DC-DC conversion circuit to charge the first capacitor by using battery electric energy output by a battery system, and after determining that a capacitance voltage of the first capacitor reaches a first threshold voltage, indicate a charging pile to output charging electric energy. A soft-start circuit does not need to be disposed in a soft-start process of the charger, which helps simplify a circuit of the charger and implement a miniaturization design of the charger.