Display Driver Demultiplexer Parasitic Capacitance Management
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Solution Overview
Problem
The challenge is to reduce heat generation and power consumption in display drivers for compact liquid crystal displays, particularly when driving multiple source lines in time division mode, which requires high-speed output amplifiers and results in increased heat and power usage.
Innovation Solution
A display driver design that incorporates a demultiplexer with first and second switches, a voltage multiplexing part, and a controller to manage the connection of driving voltages and connection control signals, allowing for efficient charging and discharging of parasitic capacitance, thereby reducing the current output and power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If time division driving is used to drive multiple source lines with one output amplifier, then the number of external terminals is reduced, but heat generation and power consumption increase due to high-speed charging and discharging of parasitic capacitance
Solution Approach 1:
The patent applies preliminary action by pre-charging the parasitic capacitance of the demultiplexer and wiring before the actual data line charging. The output amplifier charges the parasitic capacitance of the demultiplexer and wiring in advance during the connection period, so that when the data line needs to be charged, the capacitance is already prepared, reducing the energy required during the actual data transmission phase.
Solution Approach 2:
The patent implements continuity of useful action by maintaining the output amplifier in a continuous low-current charging state throughout the entire period, rather than switching to high-current pulses. The amplifier continuously charges the parasitic capacitance at a low current level, ensuring that the capacitance is always ready without requiring high-speed switching operations that consume excessive energy.
2Device complexity
If time division driving is used to drive multiple source lines with one output amplifier, then the number of external terminals is reduced, but heat generation increases due to high-speed charging and discharging of parasitic capacitance
Solution Approach 1:
The output amplifier performs preliminary charging of the parasitic capacitance in advance before the data line switching occurs. By charging the capacitance of the demultiplexer and wiring beforehand at a low current level, the system avoids the need for high-speed high-current charging operations that generate excessive heat during the actual data transmission.
Solution Approach 2:
The patent employs periodic action by alternating between connection periods and disconnection periods in a cyclic manner. During connection periods, the output amplifier continuously charges the parasitic capacitance at low current. During disconnection periods, the amplifier is turned off or operates at minimal current. This periodic operation pattern reduces average power consumption and heat generation compared to continuous high-speed switching.
3Productivity
If drive time per source line is shortened to enable time division driving, then multiple source lines can be driven by one amplifier, but the amplifier must operate at higher speeds increasing power consumption
Solution Approach 1:
The system performs preliminary charging of the parasitic capacitance during the connection period before the actual data line charging is needed. The output amplifier charges the capacitance of the demultiplexer and wiring in advance at a low current level, so that when the data line needs to be driven, the capacitance is already prepared, eliminating the need for high-power fast charging operations.
Solution Approach 2:
The patent implements continuous useful action by maintaining a constant low-current charging state throughout the connection period. Instead of using intermittent high-current pulses to achieve fast charging, the amplifier continuously charges the parasitic capacitance at a low, steady current level, which reduces peak power requirements while still achieving the necessary charging in time for data line operation.
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 reduces power consumption and heat generation by utilizing accumulated electric charge in parasitic capacitance, allowing for sequential driving of data lines and efficient supply of connection control signals, leading to lower amplifier output current and reduced heat and power usage in the display driver.
Implementation Method 1
an output amplifier that can charge and discharge a parasitic capacitance of a display device in a high speed is required
Data Source
AI summary
A display driver drives a display device including a plurality of data lines and a demultiplexer. The demultiplexer includes a plurality of first switches connected to the respective plurality of data lines, and a series of driving voltages including a plurality of driving voltages is supplied via a first wiring. The demultiplexer supplies the plurality of driving voltages to the respective plurality of data lines via the plurality of first switches. The display driver includes: a voltage multiplexing part that generates the series of driving voltages; a second switch connected between the voltage multiplexing part and the first wiring; and a controller connected to the plurality of first switches and the second switch. The controller switches the second switch from an on state to an off state during a first period and sets the two first switches corresponding to the two data lines to the on state such that the two data lines and the first wiring are connected during a second period that is a part of the first period and in which the second switch is in the off state.