Variable Voltage Control for Hybrid Vehicle Sub-Battery
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Solution Overview
Problem
Hybrid vehicles face inefficiencies in fuel consumption and alternator performance due to sub-battery discharge during idle stops and high RPM conditions, leading to errors in electric device operations and reduced fuel efficiency, with existing systems requiring additional sensors and increased costs.
Innovation Solution
A variable voltage control system comprising a main battery, sub-battery, and low-voltage DC/DC converter, where a power controller manages voltage supply based on vehicle states (idle stop, constant velocity, acceleration, and deceleration) using alternating low and reference voltages to prevent sub-battery discharge and optimize energy distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an alternator is used to charge the battery in hybrid vehicles, then the battery can be charged during operation, but sub-battery discharge occurs during idle stops and high RPM conditions leading to errors in electric device operations
Solution Approach 1:
The patent implements dynamic voltage control where the alternator output voltage is adjusted based on real-time operating conditions (idle stop, acceleration, deceleration, constant velocity). During idle stops, the voltage is reduced to prevent sub-battery discharge, while during high-demand conditions, voltage is increased to ensure adequate power supply. This dynamic adjustment resolves the contradiction by adapting the charging system to prevent energy loss when not needed while maintaining reliability when required.
Solution Approach 2:
The system changes the voltage parameter of the alternator output based on vehicle state. By monitoring operating conditions and adjusting the reference voltage accordingly, the system prevents sub-battery discharge during idle stops (by reducing voltage to prevent overcharging) while ensuring adequate voltage during acceleration and high-load conditions. This parameter change approach directly addresses both the reliability and energy loss concerns.
2Reliability
If the alternator increases RPM or engine torque to maintain voltage during high electric device load, then voltage stability is improved, but fuel efficiency deteriorates
Solution Approach 1:
The system dynamically adjusts alternator voltage output based on actual electric device load and vehicle state rather than maintaining constant high voltage. During normal operation, lower voltage suffices, but during high-load conditions (headlamps, wipers, A/C), the system increases voltage to maintain stability. This dynamic response ensures voltage stability only when necessary, minimizing fuel consumption during normal operation.
Solution Approach 2:
The alternator reference voltage is changed based on detected vehicle conditions and electric device load. The control unit monitors load requirements and adjusts the voltage parameter accordingly - maintaining stability when needed while reducing voltage output during normal operation to minimize energy consumption and improve fuel efficiency.
3Use of energy by moving object
If variable voltage control is implemented to prevent sub-battery discharge, then fuel efficiency improves, but additional sensors and control systems are required increasing cost
Solution Approach 1:
The control unit integrates multiple functions: it monitors vehicle state (idle stop, acceleration, deceleration), detects electric device load, controls alternator voltage output, and manages battery charging. By making the control unit multi-functional rather than adding separate dedicated systems, the patent achieves variable voltage control to improve fuel efficiency while minimizing the increase in device complexity and cost.
Solution Approach 2:
The patent combines the alternator control function with the existing battery management and vehicle state monitoring systems. Rather than creating a separate complex control system, the invention merges the voltage control logic into the existing control architecture, achieving fuel efficiency improvements while limiting the increase in overall system complexity.
4Reliability
If the alternator operates at high RPM to maintain constant voltage, then voltage output is stable, but alternator efficiency deteriorates in high RPM region
Solution Approach 1:
The system transitions from static constant voltage control to dynamic voltage control that adapts to operating conditions. During idle stops and normal operation, the alternator operates at lower RPM with reduced voltage output. During high-load conditions, RPM and voltage are increased as needed. This dynamic operation allows the alternator to run in its efficient RPM range most of the time while maintaining voltage stability when required.
Solution Approach 2:
The alternator operating parameters (voltage and RPM) are changed based on vehicle state and load conditions. Rather than maintaining constant high voltage and RPM, the system adjusts these parameters dynamically - reducing them during normal operation to improve alternator efficiency while increasing them during high-demand conditions to maintain voltage stability.
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
The system enhances fuel efficiency by preventing sub-battery discharge, reducing energy loss, and improving charging efficiency across various vehicle states, while minimizing errors in electric device operations and lowering operational costs.
Implementation Method 1
The LDC may convert the high-voltage power of the main battery into the low-voltage power to be supplied to the electronic devices
Data Source
AI summary
A system for controlling voltage to be supplied to electronic devices in a hybrid vehicle that includes: a main battery for storing power to be supplied to a motor of the vehicle; a sub-battery for storing power to be supplied to electronic devices of the vehicle; a low-voltage DC/DC converter (LDC) for converting a high voltage of the main battery into a low voltage and providing the low voltage to the sub-battery and the electronic devices; and a power controller for controlling power of the main battery, the LDC, and the sub-battery. The power controller controls the voltage to be supplied to the electronic devices with a low voltage, a reference voltage higher than the low voltage, and a high voltage higher than the reference voltage in accordance with an idle stop state, a constant velocity traveling state, an acceleration state, and a deceleration state of the vehicle.