Pre-Charging Circuit Using PWM Control to Reduce PCBA Area
Solution Overview
Problem
Conventional pre-charging circuits in battery management systems for new energy vehicles require numerous current limiting resistors, leading to increased area occupation on printed circuit boards, high thermal power consumption, and elevated costs due to the need for specialized heat dissipation, which complicates the pre-charging process.
Innovation Solution
A pre-charging circuit comprising a controller, a PWM control unit, and a drive unit that detects current in the battery management system and adjusts the pre-charging time of the load capacitor by outputting control signals and PWM signals to control the main switch, allowing for efficient pre-charging while reducing the number of current limiting resistors and optimizing heat management.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional pre-charging circuits use a large quantity of current limiting resistors, then the pre-charging function is achieved, but the area occupation on PCBA increases and thermal power consumption becomes large
Solution Approach 1:
The patent extracts the current limiting function from traditional passive resistors and transfers it to an active control mechanism. The controller regulates the pre-charging current through PWM control of the main relay, eliminating the need for physical current limiting resistors on the PCBA.
Solution Approach 2:
The patent replaces the passive electrical component system (resistors) with an active control system (controller + PWM signal + main relay control). This substitution transforms the pre-charging mechanism from a passive resistive limitation to an active electronic control process.
2Reliability
If conventional pre-charging circuits use a large quantity of current limiting resistors, then the pre-charging function is achieved, but thermal power consumption becomes large requiring special heat dissipation treatment
Solution Approach 1:
The patent removes the energy-dissipating resistors from the circuit and replaces them with a control system that regulates current flow. The main relay is controlled to open/close at appropriate moments, preventing excessive current without converting electrical energy into waste heat through resistors.
Solution Approach 2:
The patent converts the potential harmful effect of uncontrolled current into a beneficial controlled pre-charging process. By using PWM control to gradually charge the capacitor, the system transforms what would be a harmful current surge into a useful, controlled charging process that protects the relay while minimizing energy waste.
3Reliability
If conventional pre-charging circuits use current limiting resistors, then pre-charging is achieved, but the housing needs extra space for thermal pad mounting increasing costs
Solution Approach 1:
The patent extracts and eliminates the need for thermal management infrastructure (thermal pads, heat sinks, special housing features) by removing the heat-generating resistors. The control-based pre-charging approach eliminates the thermal management subsystem entirely.
4Productivity
If PWM control is used to adjust pre-charging time, then pre-charging speed is improved, but control complexity increases
Solution Approach 1:
The patent makes the existing controller perform multiple functions: it not only controls the main relay switching but also generates PWM signals for pre-charging control and monitors current through ADC sampling. This multi-functionality avoids adding separate dedicated pre-charging control circuits, thereby limiting the increase in overall system complexity.
Solution Approach 2:
The controller autonomously determines when to start and stop pre-charging by monitoring the capacitor voltage and current conditions. The system self-regulates the pre-charging process without requiring external intervention or complex external control circuits, as the controller independently manages the entire pre-charging sequence.
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 solution reduces costs and thermal management complexities by dynamically adjusting the pre-charging time, enabling faster and more efficient pre-charging of the load capacitor while minimizing the failure rate of the main switch.
Implementation Method 1
a sampling unit configured to detect a current existent in the battery management system circuit when the main switch is turned on
Data Source
AI summary
This application relates to a pre-charging circuit and a method thereof. The pre-charging circuit includes a controller, a PWM control unit, and a drive unit. The controller and the PWM control unit are electrically connected to the drive unit, and the drive unit is connected to a main switch of a battery management system circuit. When the main switch is turned on, the PWM control unit detects a current in the battery management system circuit and outputs a control signal to the drive unit according to the current. The controller outputs a preset PWM signal to the drive unit, which then turns the main switch off or on according to the received control signal and the PWM signal, to pre-charge a load capacitor of the battery management system circuit when the main switch (S1) is turned on, thereby implementing fast pre-charging by adjusting a pre-charging time of the load capacitor.