Segment LCD Control Unit Using PWM Integration
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Solution Overview
Problem
Existing segment liquid crystal display (LCD) control methods using general purpose microcontrollers are limited to only two discrete voltage levels, which restricts the flexibility and contrast improvement between visible and invisible segments, especially in dynamically driven LCDs with a large number of backplane electrodes.
Innovation Solution
A control unit that generates pulse-width-modulated control signals with two voltage levels and a variable duty cycle, integrated using an integrator to produce more than two discrete voltage levels, allowing for flexible control of segment LCDs without the need for an application-specific interface, using a general purpose microcontroller.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If pulse-width modulation with integration is used to generate multiple voltage levels, then the contrast between visible and invisible segments is improved, but the device complexity increases due to the need for an integrator circuit
Solution Approach 1:
An integrator circuit is introduced as an intermediary component between the pulse-width modulated signal source and the LCD electrodes. This integrator converts the PWM signal into multiple discrete voltage levels, enabling improved segment contrast while maintaining compatibility with general-purpose microcontrollers that can only generate two voltage levels.
2Ease of manufacture
If a general purpose microcontroller is used without application-specific interface, then the cost is reduced, but the ability to control segment LCDs with multiple voltage levels is limited
Solution Approach 1:
The integrator circuit serves as a mediator that bridges the capability gap between general-purpose microcontrollers (which can only output two voltage levels) and segment LCDs (which require multiple voltage levels for optimal performance). This allows cost-effective use of general-purpose microcontrollers while achieving the versatility needed for advanced LCD control.
Solution Approach 2:
The system changes the parameter of voltage levels from two discrete levels (capable of general-purpose microcontrollers) to multiple discrete levels (required for optimal LCD performance) through the integration process. By varying the duty cycle of the PWM signal, the integrator produces different average voltage levels, enabling precise control of multiple LCD segments.
3Device complexity
If dynamically driven segment LCDs with large number of backplane electrodes are used, then the number of electrodes controlling the LCD is reduced, but the contrast between visible and invisible segments decreases when viewed at an angle
Solution Approach 1:
The patent applies parameter changes by varying the duty cycle of pulse-width modulated signals to generate multiple discrete voltage levels. This enables precise control of the voltage applied to each segment, maintaining high contrast ratios even in dynamically driven LCDs with many backplane electrodes. The ability to apply different voltage levels compensates for the viewing angle effects that normally degrade contrast in such displays.
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 solution enhances the contrast between visible and invisible segments by generating multiple discrete voltage levels, improving the control of dynamically driven segment LCDs with greater flexibility and reduced costs compared to traditional methods.
Implementation Method 1
integrating, by the integrator, the pulse-width-modulated control signal to obtain an integrated control signal having more than two discrete voltage levels corresponding to different duty cycle values
Data Source
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AI summary
A unit (10; 11; 12; 13) used to control a segment liquid crystal display (15; 16). The segment liquid crystal display (15; 16) includes at least a backplane electrode (20) and at least a front plane electrode (25) both associated with a same segment of the segment liquid crystal display (15; 16). The unit (10; 11; 12; 13) includes a controller (30; 40; 50) in order to generate a pulse-width- modulated control signal (35) that has two voltage levels and a variable duty cycle. The unit (10; 1; 12; 13) further includes an integrator (60; 61) to integrate the pulse-width-modulated control signal (35) and to provide an integrated control signal (90) which has more than two discrete voltage levels corresponding to different variable duty cycle values. An output of the unit (10; 11; 2; 13) supplies the integrated control signal (90) to the at least a backplane electrode (20) or to the at least a front plane electrode (25) so that visibility of the same segment in the segment liquid crystal display (15; 16) can be controlled. By having a pulse-width-modulated control signal (35) with only two voltage levels and different duty cycle values generated by the controller (30; 40; 50), and by having the integrator (60; 61) integrating said pulse-width-modulated control signal (35), more than two different discrete voltage levels are generated to control the at least a backplane electrode (20) or at least a front plane electrode (25) without the need to use an application specific segment liquid crystal interface in the unit (10; 11; 12; 13), thereby abating the cost of implementation of the unit (10; 11; 12; 13).