Battery Charger Dynamic Switching Frequency Control
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Solution Overview
Problem
Conventional battery chargers using DC/DC converters in PWM mode maintain high switching frequencies to prevent overvoltage protection, leading to increased heat generation and size/cost issues when quickly charging lithium batteries with large currents, as they require large-capacity switching devices.
Innovation Solution
A battery charger that dynamically adjusts switching frequency from a lower to a higher frequency during the charge process, allowing for rapid charging with a smaller switching device by altering the switching frequency based on charge conditions, thereby reducing heat generation and component size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a high switching frequency is maintained to prevent overvoltage protection activation during constant voltage charging, then the battery can be charged to full capacity, but heat generation increases and requires larger-capacity switching devices
Solution Approach 1:
The patent applies dynamics by making the switching frequency adjustable rather than fixed. The controller dynamically changes the switching frequency from a first frequency during constant current charging to a second frequency during constant voltage charging, allowing the system to adapt to different charging stages and optimize both heat management and charging completeness.
Solution Approach 2:
The patent changes the switching frequency parameter based on charging conditions. By switching between different frequency values depending on the charging stage (constant current vs. constant voltage), the system optimizes the balance between heat generation and charging effectiveness without requiring oversized components.
2Productivity
If a large-capacity switching device is used to handle high current for rapid charging, then rapid charging is achieved, but the size and cost of the battery charger increase
Solution Approach 1:
The patent uses dynamic switching frequency adjustment to enable rapid charging with smaller components. By optimizing the switching frequency according to charging conditions, the system achieves high current capability without requiring permanently oversized switching devices, thus reducing charger weight and cost.
Solution Approach 2:
The patent changes operational parameters (switching frequency) to achieve rapid charging performance without permanently increasing component size. The switching device operates at different frequency levels depending on charging stage, allowing small-capacity devices to deliver large current when needed without the penalty of always being oversized.
3Temperature
If the switching frequency is lowered to reduce heat generation, then heat management is improved, but ripple voltage increases causing overvoltage protection activation
Solution Approach 1:
The patent applies dynamics by adjusting the switching frequency based on the charging stage. During constant current charging, a lower frequency reduces heat generation. During constant voltage charging, a higher frequency suppresses ripple voltage. This dynamic adjustment resolves the contradiction between heat management and ripple control.
Solution Approach 2:
The patent changes the switching frequency parameter according to charging conditions. By selecting appropriate frequency values for different charging stages, the system simultaneously achieves both heat reduction and ripple voltage control, preventing overvoltage protection activation while managing thermal performance.
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
This approach enables efficient rapid charging of lithium batteries with reduced heat generation and component size, maintaining safety by controlling ripple voltage and preventing overvoltage protection activation, while minimizing the size and cost of the charger.
Implementation Method 1
Battery chargers employed for charging a battery with a DC/DC converter generate a DC output voltage from a DC input voltage by controlling a semiconductor switching device such as a MOS-FET in a Pulse Width Modulation (PWM) manner
Implementation Method 2
Under PFM, the OFF duration is controlled while making the ON duration constant in order to change a switching frequency, thus controlling an output voltage within a certain range
Implementation Method 3
In addition to a switching device, a battery charger also includes an integrated circuit device for control, an inductor and a smoothing capacitor
Data Source
AI summary
A charge system is disclosed. A charge system includes a switching device and a controller. The switching device performs switching of a DC input voltage at a predetermined switching frequency to generate an output voltage, and the output voltage being utilized for charging said battery. The controller allows the switching device to operate at a first switching frequency immediately after starting of charge and at a second switching frequency when a frequency changing condition holds. The second switching frequency is higher than that of first switching frequency.