Hybrid Engine Start Control for Low-Voltage Battery Isolation
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Solution Overview
Problem
Hybrid vehicles face safety concerns and high costs due to voltage drops during thermal engine starting when the low voltage battery is faulty, as existing solutions are either expensive, bulky, or difficult to control, and may compromise safety functions like electric power steering.
Innovation Solution
A method and power supply system that uses a direct current-direct current converter to maintain on-board network voltage, with a switch to isolate the low voltage battery and starter when voltage thresholds are reached, alerting the user and preventing engine start in faulty conditions, and transitioning to a degraded mode.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a second storage means is added to safely isolate the on-board network from the starter, then safety is improved, but device complexity, weight, and energy consumption increase
Solution Approach 1:
The patent extracts the faulty low voltage battery from the power supply circuit by opening connection switches when voltage thresholds are exceeded. This isolates the problematic component without requiring additional storage means, maintaining safety while reducing system complexity.
Solution Approach 2:
The patent introduces a direct current-direct current converter as an intermediary component between the high voltage traction battery and the on-board network. This converter acts as a mediator to provide power during starter activation, replacing the need for a second storage means and reducing overall system complexity.
2Reliability
If a very high power converter is used to ensure starting voltage, then voltage stability is improved, but device complexity and cost increase
Solution Approach 1:
The patent employs dynamic control of the direct current-direct current converter, adjusting its operation based on real-time voltage measurements. The converter's power output is modulated according to the actual needs of the starter and on-board network, allowing a smaller converter to achieve the same effect as a continuously high-power converter would.
Solution Approach 2:
The patent changes the operational parameters of the converter based on battery voltage thresholds. When voltage drops below threshold S1 or rises above threshold S2, the connection switches are opened, dynamically adjusting the power flow parameters to maintain voltage stability without requiring excessive converter capacity.
3Ease of operation
If the low voltage battery is used during starter activation, then ease of operation is maintained, but voltage drops occur that disrupt safety functions
Solution Approach 1:
The patent implements preliminary protection by continuously monitoring battery voltage and preemptively opening connection switches when voltage approaches critical thresholds. This prevents voltage drops before they can occur, protecting safety functions from disruption while maintaining normal operation during healthy battery conditions.
Solution Approach 2:
The direct current-direct current converter serves as an intermediary power source that supplements or replaces the low voltage battery during starter activation. This mediator component provides the additional current needed to prevent voltage drops, allowing the low voltage battery to continue operating without causing harmful voltage sags.
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
Ensures safe starting of the thermal engine at low cost, preventing voltage drops that could disrupt safety functions, while alerting users to battery wear and preventing reactivation in faulty states, thus maintaining safety and reducing system complexity and expense.
Implementation Method 1
a direct current-direct current converter CONV, the input of which is connected to the high voltage traction battery
Data Source
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AI summary
The invention concerns a method for starting an internal combustion engine of a hybrid vehicle comprising a starter, a DC-DC converter, and a low-voltage battery connected in parallel to said on-board network, said method comprising the steps of: -activating (E1) the starter, -comparing (E4) the supply voltage (Valim) of the on-board network with a first predetermined low threshold (S1), -opening (E5) a switch (COM) comprising at least one transistor to isolate the on-board network from said low-voltage battery and from the starter when said supply voltage (Valim) of the on-board network is less than or equal to said first predetermined low threshold (S1), said step of opening (E5) being followed by steps of: -deactivating (E6) said starter, -and closing (E7) said switch (COM).