Display Driving Circuit Boosting Module Slew Rate
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Solution Overview
Problem
Conventional driving circuits for display apparatuses experience a decrease in operational amplifier slew rates when operated under different differential difference amplifier codes, leading to discontinuity in gray level display due to varying equivalent resistor-capacitor loadings, which prevents the output voltage from reaching a steady state within an adequate charging period.
Innovation Solution
A driving circuit with a boosting module that decreases the equivalent time constant between the digital-to-analog converter and the operational amplifier, enabling a boosting period before the steady state is reached, and terminating it when the output voltage stabilizes, using a control unit and multiplexer to manage switch signals and ensure increased slew rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the conventional driving system changes conductions of switches to vary the output voltage of the operational amplifier, then the output voltage can be adjusted to different levels, but the slew rate of the operational amplifier is decreased due to increased equivalent time constant of the DAC
Solution Approach 1:
The patent applies dynamics by making the switch conduction states time-variable rather than static. During the boosting period, all switches are kept conductive to minimize the equivalent time constant and maximize the slew rate. After the boosting period, switches are turned off sequentially based on the DDA code to achieve the desired output voltage. This dynamic switching strategy resolves the contradiction by adapting the switch states to different operational phases.
Solution Approach 2:
The patent implements preliminary action by introducing a boosting period before the steady-state operation. During this preliminary phase, all switches are kept conductive to rapidly charge the input capacitors and establish the correct voltage levels. This preliminary charging action ensures that when the normal DDA operation begins, the operational amplifier is already at the correct operating point, avoiding gray level discontinuity and eliminating the need for prolonged charging periods during normal operation.
2Adaptability or versatility
If the operational amplifier is operated under different differential difference amplifier codes, then different output voltage levels are achieved, but gray level discontinuity occurs due to varying equivalent resistor-capacitor loadings causing different output slew rates
Solution Approach 1:
The boosting period serves as a preliminary action that prepares the operational amplifier for any DDA code transition. By keeping all switches conductive during this period, the system rapidly charges or discharges the input capacitors to the correct voltage levels before the actual DDA operation begins. This preliminary preparation ensures that regardless of which DDA code is applied, the operational amplifier starts from a stable, known state, preventing gray level discontinuity while maintaining full adaptability to different output voltage levels.
Solution Approach 2:
The patent applies preliminary anti-action by proactively counteracting the potential gray level discontinuity before it occurs. The boosting period with all switches conductive creates a counter-balancing effect that pre-charges or pre-discharges the capacitors to compensate for the varying equivalent RC loadings that would otherwise cause slew rate variations and gray level artifacts. This preliminary counter-action eliminates the harmful effect before the actual DDA conversion begins.
Data Source
AI summary
A driving circuit of display apparatus includes an operational amplifier (OP), comprising a plurality of input terminals; a digital-to-analog converter (DAC); a multiplexer, coupled to the OP and the DAC, comprising a plurality of switches; and a boosting module, configured to decrease an equivalent time constant between the DAC and the OP to increase an output slew rate of the OP in a boosting period; wherein the boosting period is enabled before a steady state of the OP.