LV Bus Voltage Control for Fast Auxiliary Battery Disconnect Detection
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing strategies for detecting disconnected or intermittently connected auxiliary batteries in electrified vehicles are slow and may not meet the stringent requirements of autonomous vehicles, particularly for features requiring ASIL C or ASIL D levels, as they rely on large load changes that take tens of seconds to detect such conditions.
Innovation Solution
A controller is programmed to control a voltage converter to provide an oscillating output voltage with a peak amplitude less than a threshold and monitor current variations to rapidly detect battery disconnection or poor connections by generating diagnostic signals when current thresholds are not met, using a DC/DC converter to convert high-voltage to low-voltage bus power.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If existing detection strategies relying on large load changes are used, then the system can detect battery disconnection conditions, but the detection time is slow (taking tens of seconds) and may not meet ASIL C or ASIL D requirements
Solution Approach 1:
The patent applies periodic action by implementing an oscillating voltage test signal (sine wave or square wave) with a frequency of 1 Hz and peak-to-peak amplitude of less than 2% of the target voltage. This periodic voltage variation enables rapid detection of battery connection status by monitoring current response to the oscillating signal, reducing detection time from tens of seconds to significantly faster response while meeting ASIL C or ASIL D requirements
Solution Approach 2:
The patent changes the voltage parameter from a static large load change approach to a dynamic oscillating voltage signal with controlled amplitude (less than 2% peak-to-peak variation). This parameter change allows the system to detect battery disconnection by measuring current response to the oscillating voltage, achieving both rapid detection and high reliability without requiring large load changes that would take tens of seconds
2Speed
If oscillating voltage with small amplitude is applied for rapid detection, then detection speed improves, but the voltage variation must be kept below threshold to avoid affecting battery operation
Solution Approach 1:
The patent precisely controls the oscillating voltage parameters: frequency set to 1 Hz and peak-to-peak amplitude limited to less than 2% of the target voltage (e.g., less than 0.2V for a 13V lead-acid battery). This controlled parameter change enables rapid detection through current monitoring while keeping voltage variations small enough not to disrupt normal battery operation or exceed operational thresholds
Solution Approach 2:
The patent employs feedback by continuously monitoring the current response to the oscillating voltage signal and comparing it against expected values. The controller analyzes the current variation magnitude and generates diagnostic signals when the response indicates disconnection or poor connection. This feedback mechanism enables rapid detection while automatically adjusting for the small voltage variations to maintain detection sensitivity without affecting battery operation
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
Facilitates rapid and reliable detection of battery disconnection or poor connections, meeting the requirements for autonomous vehicles by providing robust and fast diagnostic signals through current monitoring, thereby ensuring reliable operation of vehicle systems.
Implementation Method 1
A DC/DC voltage converter is controlled to deliver power from the HV traction battery to the LV bus at a desired voltage
Data Source
AI summary
An electrified vehicle includes a traction battery coupled to an electric machine that provides propulsive force, an auxiliary battery, a voltage converter coupled to the traction battery and configured to convert traction battery voltage to auxiliary battery voltage, and a controller programmed to control the voltage converter to provide either a non-oscillating voltage above a first voltage threshold, or an oscillating voltage having a peak below the first voltage threshold based on a vehicle start signal and a vehicle brake pedal position signal. The controller may control the voltage converter to provide the non-oscillating voltage in response to the vehicle start signal being received while the brake pedal position signal indicates a released brake pedal, and to provide the oscillating voltage in response to the vehicle start signal being received while the brake pedal position signal indicates a depressed brake pedal.