Battery Pack Voltage Bucking via PWM Discharge Control
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Solution Overview
Problem
Conventional battery discharge methods in battery packs for electric and hybrid vehicles face inefficiencies due to fixed discharge resistance, leading to reduced discharge effect and extended time, making it difficult to maintain voltage equilibrium within limited time.
Innovation Solution
A PWM control method is applied to a solid state relay and discharge resistance to maintain constant energy consumption, adjusting the switching section to ensure maximum current capacity is maintained, allowing for rapid discharge while securing operational stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If fixed discharge resistance is used, then device simplicity is maintained, but discharge effect decreases over time and discharge time is extended
Solution Approach 1:
The patent applies PWM (Pulse Width Modulation) control to dynamically adjust the discharge current through the fixed resistance. By varying the duty cycle of the PWM signal, the effective resistance changes over time, maintaining optimal discharge power even as battery voltage drops. This transforms a static resistance-based discharge system into a dynamic controlled system, resolving the contradiction between device simplicity and discharge effectiveness.
2Productivity
If discharge resistance is increased to maintain current capacity, then discharge speed improves, but power consumption increases and device damage risk increases
Solution Approach 1:
The patent employs periodic PWM switching to control the discharge process. Instead of applying continuous high current that would cause excessive power consumption and potential damage, the system applies current in periodic pulses with controlled duty cycles. This periodic action maintains high average discharge speed while limiting peak current and power consumption, preventing device damage and reducing harmful thermal effects.
3Productivity
If PWM control is applied, then discharge efficiency is improved and constant power is maintained, but device complexity increases
Solution Approach 1:
The patent implements PWM control by changing the temporal parameters of the discharge current (pulse width, duty cycle, frequency) rather than physically changing the resistance value. This parameter-based control approach maintains constant discharge power and high efficiency while avoiding the need for complex variable resistance circuits. The control circuit complexity is minimized by using standard PWM generation techniques with the existing fixed resistance component.
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 method enables rapid and stable discharge of batteries by maintaining constant discharge power irrespective of voltage drops, improving discharge efficiency and preventing device damage from excessive current.
Implementation Method 1
a discharge resistance (buck resistance) is connected to a battery exhibiting a higher voltage than a mean voltage so that energy of the battery is consumed through the resistance
Data Source
AI summary
An apparatus and method for discharging a voltage in a battery pack. The apparatus includes a discharge resistance connected to a discharge target battery of plural batteries in the battery pack and discharging a voltage of the discharge target battery, a switching section for connecting the discharge target battery and the discharge resistance, a voltage measuring section for measuring a voltage of the discharge target battery, and a control section for controlling the switching section depending on the measured voltage value of the battery. The method includes measuring a voltage of the discharge target battery, calculating a PWM duty rate of a switching section connecting the discharge target battery and a discharge resistance using the measured voltage value and a value of the discharge resistance, and controlling the switching section based on the duty rate to maintain an energy consumed in the discharge resistance to be constant.