Capacitive Load Charging Using Cable Inductance and Pulse Switching
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Solution Overview
Problem
The use of large capacitors in electrical systems to reduce power supply voltage fluctuations leads to inrush currents that can damage transistors when charging, and traditional fuses have variability issues, resulting in oversized cables that occupy more space and weight in vehicles.
Innovation Solution
A system utilizing a controller to repeatedly turn on and off transistors, leveraging parasitic inductance in cables to continue charging capacitors, and replacing melting fuses with solid-state switches to manage current more precisely, allowing for smaller gauge wires.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a large capacitor is used to reduce power supply voltage fluctuations, then power supply stability is improved, but the charging time increases and inrush current damages transistor
Solution Approach 1:
The controller repeatedly turns the transistor on and off in periodic cycles to charge the capacitor. During each on-period, current flows to charge the capacitor; during each off-period, the parasitic inductance continues charging. This periodic switching enables large capacitors to be charged effectively without excessive inrush current damage.
Solution Approach 2:
The patent converts the harmful parasitic inductance in the cable into a beneficial charging element. By timing the transistor switching to coincide with the inductive energy release, the parasitic inductance becomes an auxiliary capacitor charger, reducing the overall charging time and enabling faster charge of large capacitors.
2Reliability
If traditional fuses are used for current protection, then transistor damage from inrush current is prevented, but cable size increases due to variability issues
Solution Approach 1:
The controller monitors the current through the transistor and adjusts the switching timing based on feedback signals. This feedback mechanism enables precise control of the charging process, protecting the transistor from damage while optimizing the cable size by eliminating the need for oversized cables required by traditional fuse-based protection.
Solution Approach 2:
The patent replaces the mechanical fuse-based protection system with an electronic controller that uses solid-state switching and feedback control. This substitution eliminates the need for oversized cables while maintaining reliable transistor protection, reducing both weight and space requirements.
3Productivity
If the transistor is turned on continuously to charge the capacitor, then charging speed is improved, but inrush current damages the transistor
Solution Approach 1:
The transistor is switched on and off periodically rather than remaining continuously on. This periodic operation allows the capacitor to charge during on-periods while the parasitic inductance continues charging during off-periods, achieving fast charging without sustained inrush current that would damage the transistor.
Solution Approach 2:
The controller anticipates the inrush current issue by pre-timing the transistor switching. The transistor is turned on at optimal moments when the parasitic inductance can assist charging, and turned off before inrush current reaches damaging levels, preventing transistor damage while maintaining charging speed.
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 reduces the risk of transistor damage from inrush currents and minimizes cable size and weight by efficiently charging capacitors while maintaining reliable current management.
Implementation Method 1
The cable has a parasitic inductance. Each time the transistor is turned off, inductive energy in the parasitic inductance continues to charge the capacitor.
Implementation Method 2
Each time the transistor is turned off, inductive energy in the parasitic inductance continues to charge the capacitor.
Implementation Method 3
The system also includes a diode coupled between the second current terminal and a supply reference terminal.
Data Source
AI summary
A system includes a transistor having a control input and first and second current terminals. The system also includes a diode coupled between the second current terminal and a supply reference terminal. An electronics unit has a supply voltage terminal. The electronics unit has a capacitor coupled between the supply voltage terminal and the supply reference terminal. A cable has a length of at least one meter and is coupled between the transistor and the electronics unit. The cable has a parasitic inductance. A controller has a current sense input and a control output. The current sense input is coupled to the first current terminal, and the control output is coupled to the control input. The controller is configured to repeatedly turn on and off the transistor to charge the capacitor. Each time the transistor is turned off, inductive energy in the parasitic inductance continues to charge the capacitor.