Battery Precharge Circuit Using a Second Battery Before Relay Closure
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Solution Overview
Problem
In electric vehicles, the electric circuit may break down due to high current when powered by a battery with a voltage difference that is not within a predetermined range, necessitating a solution to safely transition the main relay to a closed state.
Innovation Solution
A precharge apparatus that includes a first battery, an electric circuit, a relay, and a control section to control the exchange of electric power, bypassing the main relay by using a second battery to supply power to the electric circuit while the relay is open and switching to a closed state when the voltage reaches a target value.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the main relay is switched from open state to closed state to power the electric circuit, then the electric circuit can be powered by the battery, but the electric circuit may break down due to high current when the voltage difference is not within a predetermined range
Solution Approach 1:
The precharge apparatus performs preliminary voltage boosting of the electric circuit before closing the main relay. The control section activates the precharge relay to connect the precharge inductor, which boosts the voltage of the electric circuit to a predetermined level before the main relay is closed, preventing high current damage when the voltage difference is excessive.
Solution Approach 2:
The precharge inductor acts as an intermediary component between the battery and the electric circuit. It temporarily stores and releases energy to bridge the voltage gap, allowing smooth power transfer without direct connection that would cause high current surge.
2Reliability
If a precharge relay and precharge inductor are added to boost voltage before main relay closure, then high current damage is prevented, but the device complexity increases
Solution Approach 1:
The precharge inductor is designed to serve multiple functions: it acts as a precharge inductor for voltage boosting, and simultaneously functions as a chopper inductor for DC-DC conversion during battery charging. This multi-functionality reduces the need for separate components and simplifies the overall system structure.
Solution Approach 2:
The precharge relay and precharge inductor are integrated into the existing battery relay and DC-DC converter circuitry. The control section manages both the precharge operation and DC-DC conversion using a unified control strategy, merging multiple functions into a single coordinated system rather than separate independent subsystems.
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 precharge apparatus prevents electric circuit breakdown by gradually increasing the voltage to the target value, allowing the main relay to be bypassed and ensuring safe power transfer.
Implementation Method 1
a second battery; and a control section configured to control exchange of the electric power among the relay, the second battery, and the electric circuit
Implementation Method 2
a relay configured to switch electric power supply from the first battery to the electric circuit
Data Source
AI summary
A precharge apparatus includes a first battery, an electric circuit configured to be supplied with electric power from the first battery, a relay configured to switch electric power supply from the first battery to the electric circuit, a second battery, and a control section configured to control exchange of electric power among the relay, the second battery, and the electric circuit, wherein the control section causes the second battery to supply electric power to the electric circuit while the relay is in an open state, and when a voltage level of the electric circuit reaches a predetermined value or higher, controls the relay to a closed state.