Power Switching Circuit Synchronizes Display Brightness
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Solution Overview
Problem
Conventional power switching circuits for display devices, such as OLEDs and TFT-LCDs, fail to maintain uniform brightness across pixels due to asynchronous operation between the power switching circuit and the pixel driving timing, resulting in irregular brightness variations over time and location.
Innovation Solution
A power switching circuit that synchronizes the pulse control signal with the timing signal driving the load, using a frequency control circuit to generate a second reference signal and a pulse modulation circuit to ensure uniform power voltage delivery across pixel regions, employing PWM or PFM to maintain average voltage within a target range, and incorporating a feedback circuit to stabilize output power.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Extent of automation
If the power switching circuit uses an internal oscillator to generate operating frequency, then the power circuit can operate independently, but the brightness uniformity across pixels deteriorates due to asynchronous operation with pixel driving timing
Solution Approach 1:
The patent employs a feedback mechanism where the pixel driving timing signal is used to synchronize the power switching circuit's operation. The controller adjusts the power switching timing based on feedback from the pixel driving sequence, ensuring that power delivery is synchronized with pixel activation across different regions, thereby maintaining brightness uniformity while preserving independent operation capability
Solution Approach 2:
The patent changes the operating parameters of the power switching circuit by synchronizing its switching frequency and phase with the pixel driving timing signal. This parameter adjustment aligns the power delivery cycles with the pixel scanning sequence, eliminating the brightness non-uniformity caused by asynchronous operation while maintaining the circuit's independent functionality
2Device complexity
If the power switching circuit operates at a fixed frequency from internal oscillator, then the circuit design is simplified, but the output voltage average value varies across different pixel regions causing brightness non-uniformity
Solution Approach 1:
The patent introduces dynamic adjustment to the power switching circuit by making the switching timing dependent on the pixel driving timing signal. Instead of a completely fixed frequency operation, the circuit dynamically synchronizes its switching cycles with the pixel scanning sequence, allowing the effective output voltage to remain uniform across different pixel regions while keeping the overall circuit design relatively simple
3Productivity
If the pixel driving timing and power switching timing are asynchronous, then the two circuits can operate independently, but the effective output voltage varies across different time intervals and pixel regions
Solution Approach 1:
The patent uses the pixel driving timing signal as a reference feedback to synchronize the power switching circuit. This feedback mechanism ensures that the power switching operations are coordinated with the pixel driving sequence, maintaining both independent circuit operation capability and consistent output voltage delivery across different time intervals and pixel regions
Data Source
AI summary
A power switching circuit and a method for controlling the same are disclosed herein. The power switching circuit includes a frequency control circuit, a pulse modulation circuit, and a switching convertor. The frequency control circuit receives a first reference signal driving a load, from a timing controller, and generates a second reference signal based on the first reference signal. The pulse modulation circuit generates a pulse control signal by performing pulse width modulation (PWM) or pulse frequency modulation (PFM) on the second reference signal. The switching convertor generates the voltage of output power by switching a switching element connected to the output power, in response to the pulse control signal. The pulse control signal is synchronized with the first reference signal driving the load.