Display Data Driver Output Circuit for Fast Charge-Discharge Switching

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Solution Overview

Problem

Existing output circuits for liquid crystal display devices face delays in switching between charging and discharging operations, leading to potential image quality deterioration and uneven display due to differences in supply voltage ranges between differential stages and output stages.

Innovation Solution

An output circuit configuration with a differential amplifier circuit, an output amplifier circuit, and a control circuit that includes a third transistor and a switch, where the switch is kept on for a given period to prevent delays by ensuring the control terminal is conductive through a diode coupling mode, and then cut off, allowing for immediate switching between charging and discharging operations without delay.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the output circuit uses a conventional configuration with differential amplifier and output amplifier circuits, then the circuit can drive the data lines, but delays occur in switching between charging and discharging operations leading to image quality deterioration

Engineering Contradiction:

Improveimage quality consistencyVSAvoidswitching delay between charging and discharging operations

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The control circuit performs preliminary action by turning on the switch connected to the control terminal of the first transistor before the actual switching operation. This preliminary conduction state prepares the control terminal to immediately respond to input signal changes, eliminating delays in switching between charging and discharging operations of the data lines.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The control circuit dynamically changes the conduction state of the switch connected to the control terminal of the first transistor. By making the control terminal conductive during specific periods and non-conductive at other times, the circuit adapts its behavior to prevent delays during critical switching operations, thereby improving image quality consistency.

Inventive Principle:

Principle #15Dynamics

2Use of energy by moving object

If the supply voltage range of the output stage is reduced to lower power consumption, then power consumption decreases, but delays occur when switching between charging and discharging operations

Engineering Contradiction:

Improvepower consumption of output circuitVSAvoidswitching delay in output signal

Core Design Contradiction:

Use of energy by moving objectVSLoss of time

Solution Approach 1:

The invention changes the operational parameters of the output circuit by controlling the conduction state of the switch connected to the first transistor's control terminal. This parameter control ensures that the transistor remains conductive during critical switching periods, preventing delays in output signal switching while maintaining the reduced supply voltage range for lower power consumption.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The control circuit prepares the output stage for immediate switching by maintaining the control terminal of the first transistor in a conductive state during specific periods. This preliminary preparation eliminates delays when switching between charging and discharging operations, even while operating at reduced power consumption levels.

Inventive Principle:

Principle #10Preliminary action

3Speed

If the switch is kept on continuously to prevent switching delays, then switching responsiveness improves, but power consumption increases

Engineering Contradiction:

Improveswitching speed between charging and dischargingVSAvoidpower consumption of control circuit

Core Design Contradiction:

SpeedVSUse of energy by moving object

Solution Approach 1:

The control circuit applies periodic action by controlling the switch connected to the first transistor's control terminal to be conductive only during specific periods when switching operations are anticipated or occurring. This periodic conduction maintains switching speed while avoiding continuous power consumption, as the switch is turned off during periods when switching is not required.

Inventive Principle:

Principle #19Periodic action

Solution Approach 2:

The control circuit dynamically adjusts the conduction state of the switch based on operational requirements. The switch is made conductive during critical switching periods to ensure fast response, and non-conductive during other periods to reduce power consumption, creating a dynamic balance between speed and energy efficiency.

Inventive Principle:

Principle #15Dynamics

Data Source

PatentUS9892703B2Output circuit, data driver, and display device

Publication Date: 2018.02.13 RENESAS ELECTRONICS CORP

AI summary

A display device includes an output circuit including a differential amplifier circuit, an output amplifier circuit that includes a first transistor of the first conduction type coupled between the first supply terminal and the output terminal, and including a control terminal coupled to the differential amplifier circuit, a first control circuit, an input terminal, an output terminal, and first to third supply terminals to which first to third supply voltages are applied, wherein the third supply voltage is set to a voltage between the first supply voltage and the second supply voltage, or the second supply voltage, and wherein the first control circuit includes a third transistor and a first switch which are coupled in series between the first supply terminal and the control terminal of the first transistor.