COG Source Driver Malfunction Prevention Circuit
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Solution Overview
Problem
The COG-form source driver integrated circuit in flat panel displays malfunctions due to an unstable output of the level shifter at the initial stage of the power sequence, leading to over-current flow and potential damage from a shorted path, caused by the sequential application of high and low voltages.
Innovation Solution
A malfunction prevention circuit is introduced, comprising level shifters and initialization circuits that initialize control signals to a constant voltage during a predetermined time when the low voltage is applied, preventing the shorted path and over-current flow by stabilizing the transmission gates of the multiplexer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a low voltage is applied after a high voltage in the power sequence, then the operation stability of internal circuits is improved, but the level shifter outputs control signals in a random state causing transmission gates to turn on and create shorted paths
Solution Approach 1:
The patent applies preliminary action by setting the initialization signal to enable the initialization circuit before the low voltage is fully applied to the level shifter. This preliminary initialization ensures that the control signal output terminal is pre-charged to a known high logic level state before the low voltage stabilizes, preventing random state output and subsequent shorted paths when the transmission gates switch.
2Reliability
If the initialization circuit is added to stabilize control signals, then the malfunction prevention is improved, but the device complexity increases
Solution Approach 1:
The patent applies universality by designing the initialization circuit to serve multiple functions: it initializes the control signal output terminal during power-up sequences, stabilizes the level shifter output before it drives the transmission gates, and prevents random state transitions. This multi-functional design reduces the need for separate dedicated circuits for each function, thereby limiting the increase in overall device complexity.
Data Source
AI summary
Provided is a malfunction prevention circuit for a COG-form source driver integrated circuit with a power sequence in which a low voltage is applied after a high voltage is applied. The malfunction prevention circuit includes: a level shifter configured to process an input signal using the low voltage and output a control signal using the high voltage; and an initialization circuit configured to initialize the control signal to a constant voltage while an initialization signal is enabled. The initialization signal is enabled during a predetermined time from the time at which the low voltage starts to be applied at the initial stage of the power sequence.