Hybrid Vehicle DC-DC Converter Cold Cranking Control
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Solution Overview
Problem
Hybrid vehicles experience sudden voltage drops in auxiliary batteries during cold cranking, leading to overcurrent supply and unstable headlight brightness due to inadequate control of low voltage DC-DC converters.
Innovation Solution
A system and method that includes a voltage sensor and controller to detect voltage changes in auxiliary batteries, adjusting the DC-DC converter's output voltage command to prevent overcurrent and maintain stable power supply during cold cranking, by setting the output voltage command to match the detected voltage and adjusting rates of change based on voltage comparisons.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the LDC performs general output voltage control during cold cranking, then the output voltage is maintained at a normal level, but overcurrent is supplied to the auxiliary battery causing unstable operation
Solution Approach 1:
The control method dynamically adjusts the output voltage command of the LDC based on the detected auxiliary battery voltage. When cold cranking is detected, the output voltage command is adjusted to match the fluctuating auxiliary battery voltage, transforming the static voltage control into a dynamic adaptive control that follows battery voltage changes
Solution Approach 2:
The system continuously detects the auxiliary battery voltage and uses this feedback to adjust the LDC output voltage command. The controller compares the detected voltage with the output voltage command and modifies the command accordingly, creating a closed-loop feedback control system that prevents overcurrent conditions
2Device complexity
If the LDC maintains normal output voltage during cold cranking, then the voltage regulation is simple, but a dimming phenomenon occurs due to voltage difference between auxiliary battery and LDC output
Solution Approach 1:
The control system uses feedback from the auxiliary battery voltage detection to continuously adjust the LDC output voltage command. This closed-loop control ensures that the LDC output voltage matches the auxiliary battery voltage, eliminating voltage differences that cause headlight dimming while maintaining relatively simple control logic
Solution Approach 2:
The system changes the output voltage parameter of the LDC dynamically based on the detected auxiliary battery voltage. By adjusting the output voltage command to match the battery voltage, the system maintains stable power delivery to lighting loads without complex control mechanisms
3Power
If the LDC increases power output to compensate for auxiliary battery voltage drop, then the power supply is enhanced, but overcurrent conditions worsen during cold cranking
Solution Approach 1:
The system detects the auxiliary battery voltage and uses this feedback to adjust the LDC output voltage command downward when cold cranking is detected. This feedback control prevents the LDC from supplying excessive power that would cause overcurrent, instead matching the power output to the actual battery voltage level
Solution Approach 2:
The control method detects cold cranking conditions in advance and preemptively adjusts the output voltage command to match the expected low battery voltage. This preliminary anti-action prevents overcurrent from occurring in the first place, rather than reacting after the problem arises
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
Prevents overcurrent and stabilizes the power supply to auxiliary batteries, ensuring safe vehicle operation and preventing dimming phenomena during cold cranking by accurately managing the low voltage DC-DC converter's output.
Implementation Method 1
a DC-DC converter configured to down-convert and output a voltage of the main battery
Implementation Method 2
a voltage sensor configured to detect a voltage of the auxiliary battery
Data Source
AI summary
A method of controlling a low voltage DC-DC converter of a hybrid vehicle includes determining whether cold cranking of the hybrid vehicle occurs based on a size and a rate of change of a detection value obtained by detecting a voltage of the auxiliary battery, a first adjusting operation of setting an output voltage command of the low voltage DC-DC converter to substantially the same value as the detection value and adjusting an output voltage of the low voltage DC-DC converter when determining that cold cranking occurs in the determining, and a second adjusting operation of adjusting the output voltage command and adjusting an output voltage of the low voltage DC-DC converter based on whether the detection value is increased or reduced and a comparison result between the detection value and a size of the output voltage command.