LCD Common Voltage Circuit Using PWM Duty Ratio Control
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Solution Overview
Problem
Conventional common voltage generating circuits for LCDs are large, complex, and lack precision in voltage adjustments due to a finite number of resistors, resulting in suboptimal display quality.
Innovation Solution
A common voltage generating circuit utilizing a square wave generating unit, diode, NOT gate, capacitors, and resistors, where the duty ratio of the square wave signal is modulated to generate a precise common voltage, eliminating the need for numerous resistors and enabling high-precision voltage adjustments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional voltage generating circuit with multiple resistors is used, then voltage division is achieved, but the circuit size and complexity increase
Solution Approach 1:
The patent changes the fundamental parameter from resistor count to PWM duty cycle ratio. By modulating the duty cycle of a square wave signal, the circuit can generate precise voltage adjustments without being limited by a finite number of resistors. This transforms a discrete component-based voltage division approach into a continuous control approach using pulse width modulation.
Solution Approach 2:
The patent replaces the mechanical/electrical system of multiple physical resistors with an electronic control system using PWM modulation. The voltage adjustment is achieved through digital control of the duty cycle rather than through physical selection of resistor values, thereby reducing circuit complexity while maintaining or improving precision.
2Measurement precision
If numerous resistors are used for voltage division, then voltage outputs can be generated, but the circuit size increases
Solution Approach 1:
The patent transforms the voltage control mechanism from resistor-based voltage division to PWM duty cycle modulation. This parameter change allows precise voltage control to be achieved through temporal modulation rather than spatial arrangement of multiple resistors, significantly reducing the circuit area required.
Solution Approach 2:
The patent employs periodic square wave signals with variable duty cycles to achieve voltage control. By using periodic action, the circuit can generate multiple voltage levels through temporal modulation of a single signal source, eliminating the need for multiple resistors and reducing the overall circuit footprint.
3Device complexity
If a finite number of resistors is used, then the circuit remains simple, but voltage adjustment precision is limited
Solution Approach 1:
The patent changes the control parameter from discrete resistor selection to continuous PWM duty cycle modulation. This allows the circuit to maintain simplicity with fewer components while achieving high precision voltage adjustments through variable duty cycle control of the square wave signal.
Solution Approach 2:
The patent makes a single PWM-controlled circuit perform the function that previously required multiple resistors. The square wave generating unit with adjustable duty cycle serves as a universal voltage control mechanism, replacing the need for multiple specialized resistors and enabling precise voltage adjustment with a unified simple circuit.
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 solution results in a compact, simple circuit capable of producing precise common voltage adjustments, enhancing the display quality of LCDs by allowing for more precise control over the common voltage.
Implementation Method 1
A duty ratio of the output by the square wave generating unit is capable of being modulated
Implementation Method 2
The output terminal of the square wave generating unit is coupled to the output terminal via the first resistor, a positive terminal of a diode, a negative terminal of the diode
Implementation Method 3
The positive terminal of the diode is grounded via a second capacitor, and the output terminal of the common voltage generating circuit is grounded via a third capacitor
Data Source
AI summary
A common voltage generating circuit includes a square wave generating unit, a diode, a NOT gate, a first capacitor, a second capacitor, a third capacitor, a first resistor, a second resistor, and an output terminal. The square wave generating unit includes an output terminal, which is coupled to the output terminal of the common voltage generating circuit via the first resistor, a positive terminal of the diode, a negative terminal of the diode, and the second resistor in series. The output terminal of the square wave generating unit is coupled to the negative terminal of the diode via the NOT gate and the first capacitor. The positive terminal of the diode is grounded via the second capacitor, and the output terminal of the common voltage generating circuit is grounded via the third capacitor. A duty ratio of the output square wave generating unit is capable of being modulated.