Display Driving Circuit Power Reduction via Charge Recovery Switching

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Solution Overview

Problem

Existing data-line driving circuits for display devices face challenges in reducing power consumption due to abnormal current generation during electric charge recovery, which can negate the power-saving benefits intended by previous methods.

Innovation Solution

Incorporating a first switch to shut off the connection path between the grayscale signal output circuit and the digital-analog conversion circuit, a second switch to shut off the grayscale voltage supply, and a third switch to short-circuit the grayscale signal lines for charge recovery, thereby preventing abnormal current flow between different grayscale voltage lines.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of energy

If the grayscale voltage is continuously supplied to the digital-analog conversion circuit during electric charge recovery, then the power consumption is reduced by short-circuiting the output wirings, but abnormal current is generated between different grayscale voltage lines

Engineering Contradiction:

Improvepower consumptionVSAvoidabnormal current

Core Design Contradiction:

Loss of energyVSObject-generated harmful factors

Solution Approach 1:

The patent extracts and removes the harmful abnormal current from the system by shutting off the grayscale voltage supply during electric charge recovery. The control circuit detects when recovery is needed and disables the grayscale voltage output, isolating the harmful current path while preserving the beneficial charge recovery function.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent applies preliminary anti-action by preventing the abnormal current from generating in the first place. The control circuit anticipates the charge recovery operation and proactively shuts off the grayscale voltage supply before the short-circuiting occurs, thereby preventing the harmful current flow that would otherwise result from the interaction between the voltage supply and the short-circuit path.

Inventive Principle:

Principle #9Preliminary anti-action

2Productivity

If the number of outputs of the data-line driving circuit is increased, then the display device performance is improved, but the power consumption increases

Engineering Contradiction:

Improvenumber of outputsVSAvoidpower consumption

Core Design Contradiction:

ProductivityVSUse of energy by moving object

Solution Approach 1:

The patent applies periodic action by implementing intermittent operation of the grayscale voltage output. Instead of continuous supply, the voltage is supplied periodically - active during normal operation and shut off during electric charge recovery periods. This periodic on/off pattern reduces average power consumption while maintaining the required output capability for high-resolution displays.

Inventive Principle:

Principle #19Periodic action

Solution Approach 2:

The patent implements discarding and recovering by temporarily discarding the grayscale voltage supply during charge recovery operations. The electric charge in the output wirings is recovered through short-circuiting, and the voltage supply is resumed after recovery. This cyclic discarding and recovering of the voltage supply reduces overall power consumption in high-output driving circuits.

Inventive Principle:

Principle #34Discarding and recovering

3Loss of energy

If the electric charge is recovered by short-circuiting the output wirings, then the power consumption is reduced, but the voltage exceeds the threshold voltage of transistors causing abnormal current

Engineering Contradiction:

Improvepower consumptionVSAvoidvoltage control

Core Design Contradiction:

Loss of energyVSReliability

Solution Approach 1:

The patent removes the problematic voltage supply during the charge recovery process. By shutting off the grayscale voltage output when short-circuiting occurs, the patent extracts the harmful element (excessive voltage) from the system, preventing it from exceeding transistor threshold voltages and causing abnormal current flow.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent applies beforehand cushioning by preparing the system state before charge recovery. The control circuit detects when recovery is needed and preemptively shuts off the voltage supply, cushioning against the potential harm of voltage exceeding threshold levels. This prior action prevents the reliability issue before it can manifest.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

Data Source

PatentUS8174543B2Display device driving circuit of which power consumption is reduced, control method thereof, and display device using the same

Publication Date: 2012.05.08 RENESAS ELECTRONICS CORP

AI summary

A display device driving circuit includes: a grayscale signal output circuit, grayscale signal lines, a grayscale voltage output circuit, grayscale voltage lines, a digital-analog conversion circuit, a first to third switches. The grayscale signal output circuit outputs complementary signals as a digital grayscale signal. The grayscale signal lines receive the complementary signals. The grayscale voltage output circuit outputs analog grayscale voltages. The grayscale voltage lines receive the analog grayscale voltages. The digital-analog conversion circuit selects and outputs one of the analog grayscale voltages in response to the complementary signals. The first switch shuts off a first connection path between the grayscale signal output circuit and the digital-analog conversion circuit. The second switch shuts off a second connection path between the grayscale voltage output circuit and the digital-analog conversion circuit. The third switch connects a third connection path between one of a pair of the grayscale signal lines to the other. The pair transfers a pair of the complementary signals.