Hybrid Vehicle DC Distribution Power-Up Sequence
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Solution Overview
Problem
In hybrid vehicle power trains, the high in-rush currents during power-up of DC distribution systems stress components and can lead to component failure, electrical hazards, and delays in system activation, while existing pre-charge circuits are costly and occupy space.
Innovation Solution
A method and arrangement for powering up a DC distribution system in a hybrid vehicle power train that includes an electric storage system, an internal combustion engine, an electric motor/generator, a clutch device, a power electronics unit with a voltage regulator, and an electronic control unit, which initializes engine ignition, performs diagnostics, requests pre-charge, and connects the electric storage system to loads only when pre-charge and diagnostics are complete, using a predetermined voltage to manage in-rush currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a pre-charge circuit with resistor is used to limit in-rush current, then component stress is reduced, but system cost and space occupation increase
Solution Approach 1:
The patent utilizes the inherent negative temperature coefficient characteristics of the power supply circuit's internal impedance to automatically limit in-rush current during cold start conditions. The system serves itself by leveraging its own thermal properties rather than requiring external pre-charge resistors or complex control circuits.
Solution Approach 2:
The invention extracts and utilizes the temperature-dependent impedance characteristic that naturally exists within the power supply circuitry itself, removing the need for separate pre-charge resistors and associated control components.
2Reliability
If pre-charge time is extended to reduce in-rush current magnitude, then component stress is minimized, but system activation time increases
Solution Approach 1:
The patent implements a dynamic in-rush current limitation approach where the effective resistance changes automatically with temperature. During cold start, the high impedance naturally limits current; as the system warms up, the impedance decreases allowing full power delivery. This eliminates the need for prolonged static pre-charge timing.
Solution Approach 2:
The system exploits changes in the electrical parameters (impedance) of the power supply circuit based on temperature variations. The cold temperature state provides high impedance for current limiting, while warm temperature state provides low impedance for efficient power delivery, dynamically adapting to thermal conditions.
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 minimizes component stress, reduces electrical hazards, and shortens the time to full system activation while being cost-effective and space-efficient by controlling in-rush currents and ensuring reliable operation.
Implementation Method 1
The simplest in-rush-current limiting system, used in many consumer electronics devices, is a negative temperature coefficient (NTC) thermistor, or NTC resistor. When cold, its high resistance allows a small current to pre-charge the reservoir capacitor. Constructed with high temperature materials for long life and durability, an NTC thermistor's resistance drops logarithmically as its body temperature increases.
Implementation Method 2
When direct current (DC) input power is applied to a capacitive load, the step response of the voltage input will cause the input capacitor to charge. The capacitor charging starts with an in-rush current and ends with an exponential decay down to the steady state condition.
Data Source
Figure 1
AI summary
The invention relates to a method and an arrangement for powering up a DC distribution system in a hybrid vehicle power train, said power train comprising an electric storage system, an internal combustion engine (12), an electric motor/generator (13), a clutch device to connect the electric motor/generator (13) to the internal combustion engine (12), a power electronics unit (16) with a voltage regulator (17) connected to the electric motor/generator (13), and an electronic control unit (19) for controlling the power train, wherein the electric storage system and the electric motor/generator (13) are connectable to one or more electrical loads for driving the vehicle. The powering up comprises the steps of; - initializing internal combustion engine ignition; - initializing a diagnostics test of power train components; - cranking the internal combustion engine (12); - requesting pre-charge of the electrical loads from the power electronics unit (16); - connecting the electric storage system to the electrical loads when the pre-charge and the diagnostics test are completed; - resuming normal operation for the power electronics unit (16).