Adaptive DC Link Capacitor Pre-Charge Using PWM Inrush Control
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Solution Overview
Problem
Existing pre-charge circuits in electric vehicles face issues with high inrush currents during power-up, which can damage system components, and rely on bulky resistors and electromechanical contactors that are expensive and slow, failing to adapt to varying battery voltages and discharge states.
Innovation Solution
An adaptive pre-charge control circuit using a high-voltage switch and control circuit with pulse width modulation (PWM) to manage current flow between the battery and DC link capacitor, adjusting the pre-charge threshold based on battery and capacitor voltages to ensure safe and efficient charging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional pre-charge circuits with bulky resistors and electromechanical contactors are used, then inrush current can be limited, but the system occupies more space, increases cost, and responds slowly
Solution Approach 1:
The patent extracts and removes the bulky resistor and electromechanical contactor from the pre-charge circuit, replacing them with a solid-state high-voltage switch controlled by PWM signals. This eliminates the need for large physical components while maintaining the inrush current limitation function through electronic control of the switch duty cycle.
Solution Approach 2:
The patent replaces the electromechanical contactor with a solid-state high-voltage switch that can be controlled electronically via PWM signals. This substitution eliminates mechanical wear, reduces response time, and removes the need for bulky components while achieving the same current limiting function through duty cycle control.
2Device complexity
If fixed pre-charge control is used, then circuit design is simple, but the system cannot adapt to varying battery voltages and discharge states
Solution Approach 1:
The patent implements dynamic pre-charge control by using PWM signals with variable duty cycles that adapt to real-time battery voltage conditions. The control circuit monitors battery voltage and discharge state, then adjusts the switch duty cycle dynamically to optimize pre-charge current, enabling the system to adapt to varying battery conditions rather than using a fixed control scheme.
Solution Approach 2:
The patent incorporates feedback control by monitoring battery voltage and discharge state, then using this information to adjust the PWM duty cycle of the high-voltage switch. This closed-loop approach allows the pre-charge circuit to automatically adapt to varying battery conditions, optimizing charging current based on real-time system state.
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 adaptive pre-charge control circuit effectively limits inrush currents, eliminates the need for bulky resistors, and provides fast, adaptive charging that adapts to battery conditions, ensuring safe and efficient power delivery to vehicle loads.
Implementation Method 1
The control circuit sends a pulse width modulated (PWM) signal to the high-voltage switch based on a difference between the electric battery voltage and the DC link capacitor voltage.
Implementation Method 2
The high-voltage switch controls the flow of current between an electric battery and a DC link capacitor.
Data Source
AI summary
An adaptive pre-charge control circuit includes include a high-voltage switch and a control circuit. The high-voltage switch controls the flow of current between an electric battery and a DC link capacitor, the electric battery to supply power to an electric vehicle. The DC link capacitor is made up of a sum of individual input capacitors of multiple subunits within an electric vehicle. The control circuit sends a PWM signal to the high-voltage switch based on a difference between an electric battery voltage and a DC link capacitor voltage.