MOSFET Variable Resistor for Vehicle Voltage Stabilization
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Solution Overview
Problem
The high inrush current during engine starting in vehicles with 'Stop/Start' systems causes significant voltage drops in the battery, compromising comfort and safety, and existing solutions like capacitors, voltage boosters, and filters are costly and inefficient, with mechanical relays introducing wear and EMC issues.
Innovation Solution
A system with a variable resistor composed of MOSFET transistors in parallel, controlled by a main current loop and voltage loop, connected in series with the battery and starter, operates in linear mode to stabilize the battery voltage by limiting the current peak, avoiding switching and mechanical wear.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If capacitors or voltage boosters are used to stabilize battery voltage during starting, then the voltage stability is improved, but the system cost increases substantially
Solution Approach 1:
The patent extracts and eliminates the need for complex voltage stabilization devices (capacitors, boosters) by using a fundamentally different approach - a simple series resistor that limits inrush current without requiring active voltage regulation components. This removes the costly equipment while maintaining voltage stability through passive current limiting.
Solution Approach 2:
The patent employs a simple, inexpensive resistor as a temporary measure during the starting phase. The resistor is only active during the brief starting period and can be a basic, low-cost component rather than an expensive, sophisticated voltage regulation system.
2Ease of operation
If mechanical relays are used to control current flow, then the current control is achieved, but the relay wear and EMC issues worsen
Solution Approach 1:
The patent replaces the mechanical relay system with an electronic field-effect transistor (FET) switch. This substitution eliminates moving parts, mechanical wear, and electromagnetic compatibility issues associated with mechanical relays, while providing precise electronic control of the current flow during starting cycles.
Solution Approach 2:
The patent uses a dynamically controllable FET switch that can rapidly adjust its resistance state based on real-time voltage and current conditions. This dynamic control allows the system to respond quickly to changing starting conditions without the mechanical inertia and wear associated with relay-based systems.
3Object-generated harmful factors
If high-power inductive filters are used to restrict inrush current, then the current peak is limited, but the battery voltage may fall below nominal value
Solution Approach 1:
The patent employs a feedback control system that continuously monitors battery voltage and inrush current levels. Based on this feedback, the FET switch dynamically adjusts its resistance to limit current peaks while preventing excessive voltage drops, maintaining the battery voltage within acceptable ranges throughout the starting process.
Solution Approach 2:
The patent changes the resistance parameter dynamically during the starting process. The FET switch transitions from a low-resistance state during normal operation to a high-resistance state during inrush current limitation, and then back to low resistance once the starting is complete. This parameter change allows current limiting without permanently affecting voltage levels.
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
Effectively maintains battery voltage above threshold levels, reducing current peaks and preventing battery damage, while avoiding additional costs and EMC issues, ensuring reliable operation and extended starter lifespan.
Implementation Method 1
A system with a variable resistor composed of MOSFET transistors in parallel, controlled by a main current loop and voltage loop, connected in series with the battery and starter, operates in linear mode to stabilize the battery voltage by limiting the current peak
Data Source
Figure 1a~1b
Figure 2
AI summary
The system of the invention is of the type consisting in limiting a variation in the voltage of a battery (3) powering the on-board electrical system (2) at the moment when a heat engine of the vehicle is started using an electric starter (4) connected to said system (2). The system of the invention includes a resistor (6) that can vary according to the voltage variation, said variable resistor (6) being connected in series with the battery (3) and the starter (4). According to another feature of the invention, the variable resistor (6) is controlled by a main current loop (7) according to a reference current intensity (Iref) generated by a voltage loop (8) according to the voltage variation in relation to a reference voltage (Uref). The variable resistor (6) is typically formed by multiple power transistors in parallel.