LCD Backlight Driving Circuit Synchronization
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Solution Overview
Problem
Conventional LCD backlight driving circuits with multiple PWM controlling integrated circuits suffer from asynchronization, leading to interference signals and noise, resulting in defects like flickering due to the lack of priority between high and low signals.
Innovation Solution
A driving circuit that includes a fundamental wave generator, pulse width modulation comparator, signal synchronizer, and driving signal generator, which synchronizes the phases of driving signals by adjusting the connection node and output terminal based on the power level of the LCD backlight, ensuring synchronized operation of PWM controlling integrated circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If multiple PWM controlling integrated circuits are used in parallel to enhance driving capacity, then the driving capacity of the LCD backlight is improved, but asynchronization occurs between the circuits leading to interference signals and noise
Solution Approach 1:
A signal synchronizer circuit is introduced as an intermediary component between the PWM controlling integrated circuits and the backlight system. This synchronizer receives clock signals from each PWM controller and generates synchronized enable signals that coordinate the operation of multiple circuits, eliminating phase differences and preventing interference signals and noise while maintaining enhanced driving capacity
Solution Approach 2:
The signal synchronizer implements a feedback mechanism by monitoring the clock signals from multiple PWM controllers and adjusting the enable signals accordingly. This feedback loop ensures that all PWM controllers operate in synchronization, preventing asynchronization issues while maintaining the improved driving capacity provided by parallel operation
2Device complexity
If multiple PWM controlling integrated circuits operate independently, then device complexity is reduced, but interference signals and noise occur due to lack of phase synchronization
Solution Approach 1:
The signal synchronizer serves as a minimal-complexity intermediary that coordinates multiple PWM controllers without requiring complex control logic in each controller. It receives simple clock signals and generates synchronized enable signals, adding minimal complexity while effectively eliminating interference signals and noise
Solution Approach 2:
The synchronization function is merged into a separate dedicated circuit (signal synchronizer) rather than embedding complex synchronization logic within each PWM controller. This merging approach reduces overall system complexity by centralizing the synchronization function while effectively preventing interference signals and noise
3Ease of operation
If high and low signals are output without priority, then ease of operation is improved, but asynchronization occurs leading to flickering defects
Solution Approach 1:
The signal synchronizer implements periodic action by using clock signals with specific periods to control the timing of enable signals. This periodic control ensures that high and low signals are output in a synchronized manner across multiple PWM controllers, preventing asynchronization and flickering while maintaining operational flexibility
Solution Approach 2:
The signal synchronizer performs preliminary action by generating enable signals in advance based on clock signals before the PWM controllers output their driving signals. This preliminary synchronization ensures that all controllers are ready to operate in phase, preventing asynchronization and flickering defects while maintaining ease of operation
Data Source
AI summary
In a driving circuit for an LCD backlight, a fundamental wave generator generates a triangle wave signal and a square wave signal in accordance with time constant of a time constant circuit including a time constant capacitor. A PWM comparator compares a difference signal between a feedback voltage and a preset reference voltage with the triangle wave signal to generate a PWM signal in response to the comparison result. A signal synchronizer sets a connection node between the time constant capacitor and the fundamental wave generator and an output terminal of the square wave signal in accordance with a power level of the LCD backlight. Also, a driving signal generator generates a driving signal in response to the square wave signal from the fundamental wave generator and the PWM signal from the PWM comparator. The driving circuit enables PWM controlling integrated circuits to be synchronized together.