Liquid Crystal Panel Driving Circuit UVLO Timing Control
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Solution Overview
Problem
Liquid crystal panel driving circuits face instability due to sudden voltage drops, leading to incomplete discharge of power supply voltages, which can cause timing disorders and irreversible damage during restarts, affecting user experience.
Innovation Solution
A liquid crystal panel driving circuit incorporating a pulse width modulation integrated circuit with an RC circuit, a latch, and logic gates that fully charges a capacitor during normal operation, ensuring complete discharge and controlled restarts by adjusting resistor and capacitor values to prevent output timing disorders.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the PWM IC is used with standard UVLO protection, then the IC is turned off when voltage drops below UVLO value, but the output voltages cannot be discharged completely during short voltage droops, causing timing disorders and potential damage
Solution Approach 1:
The patent applies preliminary action by requiring the power supply voltage to not only drop below UVLO but also remain there for a predetermined time period before the PWM IC is turned off. This advance timing requirement ensures that short voltage droops do not trigger premature shutdown, allowing complete discharge of output voltages and preventing timing disorders while maintaining protection against genuine power failures
Solution Approach 2:
The patent implements beforehand cushioning by introducing a time delay mechanism that cushions against the harmful effects of short voltage droops. The predetermined time period acts as a buffer that distinguishes between transient voltage fluctuations and sustained power failures, preventing unnecessary IC shutdown and avoiding the harmful effects of timing disorders and output abnormalities
2Speed
If the PWM IC restarts immediately after voltage recovery, then the system responds quickly to power restoration, but incomplete discharge of power supply voltages causes timing disorders and abnormal output
Solution Approach 1:
The patent applies preliminary action by implementing a predetermined time period requirement before the PWM IC can restart after voltage recovery. This ensures that the power supply voltages have sufficient time to discharge completely before restart, preventing timing disorders and output abnormalities while maintaining a defined restart response protocol
3Loss of time
If the UVLO threshold is lowered to allow restart at lower voltages, then the system can restart earlier, but the power supply voltage may not have discharged sufficiently, causing timing disorders
Solution Approach 1:
The patent applies preliminary action by requiring a predetermined time period to elapse during which the power supply voltage remains below UVLO before restart is permitted. This time-based preliminary condition ensures sufficient discharge of power supply voltages and maintains timing synchronization, preventing the harmful effects of premature restart even if the voltage threshold is lowered
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
The solution ensures reliable operation and enhanced user experience by preventing output timing disorders and ensuring complete discharge of power supply voltages, allowing the liquid crystal panel driving circuit to restart safely only when the power supply voltage falls below a safe point, thus maintaining normal operation.
Implementation Method 1
an RC circuit (resistor-capacitor circuit) 2. The input terminal of the RC circuit 2 is connected to a power supply voltage VDD, and an output terminal is connected to the latch 1
Implementation Method 2
a comparator 11, wherein a positive input terminal of the comparator 11 is connected to a reference voltage, and a negative input terminal of the comparator 11 is connected between the first resistor and the second resistor
Implementation Method 3
a light-emitting diode 12, wherein an anode of the light-emitting diode 12 is connected to an output terminal of the comparator 11, and a cathode of the light-emitting diode 12 is connected to the latch 1
Data Source
AI summary
A liquid crystal panel driving circuit is provided. The circuit includes a pulse width modulation integrated circuit, including an input terminal, a first resistor, a second resistor, a comparator, a light-emitting diode, a latch, a RC circuit and a power supply voltage. Wherein the input terminal is connected to a ground terminal through the first resistor and the second resistor which are serially connected, a positive input terminal of the comparator is connected to a reference voltage, and a negative input terminal of the comparator is connected between the first resistor and the second resistor, an anode of the light-emitting diode is connected to an output terminal of the comparator, and a cathode of the light-emitting diode is connected to the latch, and an input terminal and an output terminal of the RC circuit are respectively connected to the power supply voltage and the latch.