DC-DC Converter Frequency Control for Wider VSS Adjustment
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Solution Overview
Problem
Conventional DC-DC converters in display devices face limitations in power saving capabilities due to minimum on-time constraints, which restrict the range of voltage level changes and duty ratio adjustments, especially in power saving modes where reduced luminance requires efficient power consumption reduction.
Innovation Solution
The DC-DC converter employs a switching frequency controller to adjust the switching frequency and duty ratio, allowing for increased voltage levels of the negative power supply voltage (VSS) by calculating a correction switching frequency based on the target voltage level, while optionally turning off the current sensor to reduce minimum on-time and prevent output ripples.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the voltage level of high potential voltage and/or low potential voltage is changed to reduce the difference therebetween for reducing power consumption, then power consumption is reduced, but the voltage level change is limited due to minimum on-time constraint
Solution Approach 1:
The patent dynamically adjusts the switching frequency based on the target voltage level. When a higher voltage level is required (for power saving mode), the switching frequency is increased proportionally to maintain the minimum on-time requirement. This dynamic frequency adjustment enables the DC-DC converter to achieve a wider voltage level adjustment range while satisfying the minimum on-time constraint, thereby improving power consumption efficiency.
Solution Approach 2:
The patent changes the switching frequency parameter in response to changes in the target voltage level. By establishing a proportional relationship between switching frequency and target voltage level, the system can adaptively adjust operating parameters to overcome the minimum on-time limitation, enabling broader voltage level changes for power saving purposes.
2Adaptability or versatility
If the switching frequency is increased to achieve higher target voltage levels, then the voltage level adjustment range is improved, but output ripples may be introduced
Solution Approach 1:
The patent employs feedback control by comparing the actual output voltage with the target voltage level and adjusting the switching frequency accordingly. The controller monitors the output voltage and modulates the switching frequency to maintain stability, preventing excessive output ripples while achieving the desired voltage level adjustment range.
Solution Approach 2:
The system dynamically balances switching frequency adjustment with output ripple suppression. By continuously adapting the switching frequency based on real-time voltage level requirements and stability conditions, the patent achieves wide voltage adjustment range while maintaining output stability and minimizing ripples.
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 stable generation of higher target voltage levels for VSS, reducing power consumption by optimizing the duty ratio and switching frequency, thereby enhancing the power saving capabilities of the display device without introducing output ripples.
Implementation Method 1
a transformer T coupled to the rectifier bridge and having a primary winding connected to a bridge output and having a center-tapped secondary winding having a center tap connected to a reference potential terminal and two output terminals
Data Source
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AI summary
A DC-DC converter may include: a first converter for converting an input voltage to generate a first power supply voltage; a duty ratio controller configured generate a duty ratio control signal for controlling a duty ratio of a switching pulse of the first converter; a switching frequency controller configured to generate a switching frequency control signal for controlling a driving frequency of the first converter corresponding to a switching frequency of the switching pulse; and a current sensor configured to sense current flowing through the first converter. The first converter is driven at a switching frequency of a first frequency in a first mode, based on the switching frequency control signal, and generates the first power supply voltage of a first level, based on the duty ratio control signal. The switching frequency controller determines whether to turn off the current sensor.