Electric Vehicle Pre-charge Circuit Using Constant Current Source
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Solution Overview
Problem
Existing power battery pre-charge systems for electric vehicles face inefficiencies in charging due to resistance-capacitance structures, leading to long charging times and high failure rates, along with increased costs and space constraints in the distribution box, as well as challenges in selecting suitable pre-charge resistors for high voltage applications.
Innovation Solution
A power battery pre-charge system utilizing a current source circuit with a triode, resistors, and high-voltage MOSFET transistors to provide a constant charging current to a bus capacitor, reducing the peak current required for each MOSFET transistor and eliminating the need for high-voltage wiring and pre-charge resistors, thereby enhancing efficiency and reducing costs and failure rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a resistance-capacitance charging structure is used, then the pre-charge process can be implemented, but the charging time becomes long and charging efficiency becomes low
Solution Approach 1:
The patent changes the charging mode from resistance-capacitance (RC) charging to constant current charging. By using a current source circuit that maintains constant charging current regardless of voltage changes, the system achieves faster charging times and higher charging efficiency compared to traditional RC charging where current decreases exponentially as voltage increases.
Solution Approach 2:
The patent replaces the mechanical relay-based pre-charge system with an electronic current source circuit implementation. This substitution eliminates the need for mechanical switches and resistors, enabling precise control of charging current and significantly improving charging efficiency while reducing charging time.
2Reliability
If pre-charge relay and pre-charge resistor are added to the distribution box, then pre-charge function is achieved, but the cost increases and space becomes more cramped
Solution Approach 1:
The patent merges the pre-charge function into the existing power management integrated circuit (PMIC) or controller, eliminating the need for separate pre-charge relays and resistors in the distribution box. The current source circuit is integrated into the control system, reducing component count and simplifying the distribution box structure while maintaining pre-charge functionality.
Solution Approach 2:
The patent makes the power management controller multi-functional by enabling it to perform both power distribution control and pre-charge operations. The same control circuit that manages battery power distribution also generates the constant current for pre-charging, eliminating dedicated pre-charge components and reducing overall system complexity.
3Reliability
If pre-charge resistor is used to withstand high voltage, then pre-charge can be performed, but parameter waste occurs or overheat and failure rate increase
Solution Approach 1:
The patent replaces the passive resistor-based pre-charge method with an active electronic current source circuit. This substitution allows precise control of charging current, eliminating the need for high-power resistors that waste energy as heat. The electronic circuit efficiently transfers energy to the bus capacitor without significant losses.
Solution Approach 2:
The patent changes the operating parameters from high-voltage, low-current resistor-based charging to controlled constant current charging. By maintaining optimal current levels throughout the charging process regardless of voltage changes, the system avoids energy waste and prevents overheating issues associated with high-power resistors.
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 system achieves high pre-charge efficiency with reduced peak currents, lower costs, and lower failure rates by using electronic components instead of relays, and simplifies circuit diagnosis with constant charging currents that do not decrease with increased capacitance voltage.
Implementation Method 1
said power battery pre-charge device comprises a pre-charge circuit formed by a current source circuit and a bus capacitor C
Data Source
AI summary
The present invention proposes power battery pre-charge system and device for an electric vehicle, said power battery pre-charge device comprises a pre-charge circuit formed by a current source circuit and a bus capacitor, wherein said current source circuit provides a current for charging the bus capacitor, wherein said current source circuit includes a triode, a first resistor, a second resistor and at least two high-voltage MOSFET transistors. The power battery pre-charge system and device for an electric vehicle as disclosed in the present invention have high charging efficiency, low cost and low failure rate.