Power Supply Circuit Discharge Pulse Timing for IGZO Display Ghosting
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Solution Overview
Problem
In on-vehicle liquid crystal display devices with IGZO liquid crystal panels, the discharge process is often incomplete due to the simultaneous or premature fall of control signals and power supply voltages, leading to display abnormalities like ghosting.
Innovation Solution
A power supply circuit incorporating a voltage boosting circuit, capacitor, logic circuit, delay circuit, and resistor to generate a discharge pulse and ensure correct signal timing, along with diodes and a reset IC for stable voltage management, enables complete discharge even when power supply turns off.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the power supply voltage falls simultaneously or before the control signal falls, then the power supply turns off quickly, but the discharge cannot be performed correctly and charge cannot be fully drawn out
Solution Approach 1:
The discharge operation is triggered by the control signal falling edge before the power supply voltage completely falls. By initiating the discharge pulse generation in advance while the power supply voltage is still sufficient, the system ensures that the high voltage needed for discharge is available. The discharge transistor is turned on based on the control signal timing, allowing charge to be drawn out from pixels and scanning line drive circuit before the power supply voltage drops to ground level.
2Speed
If the control signal and power supply voltage fall in almost the same period, then the power supply turns off rapidly, but the high voltage for discharge cannot be generated
Solution Approach 1:
The discharge operation is initiated at the moment the control signal falls, which occurs before or during the power supply voltage fall. By triggering the discharge transistor at this timing, the system generates the high voltage pulse for discharge while the power supply voltage is still sufficiently high. This allows the discharge function to be performed correctly even during rapid power supply turn-off.
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
Ensures reliable discharge of charges from pixels and scanning line drive circuits, preventing display abnormalities and maintaining panel integrity.
Implementation Method 1
a capacitor provided between a power supply wiring for outputting the second power supply voltage and a ground
Implementation Method 2
a voltage boosting circuit configured to boost a supplied first power supply voltage to a second power supply voltage used in a drive circuit
Implementation Method 3
a resistor provided between an input terminal of the delay circuit and the ground
Data Source
AI summary
A power supply circuit includes a voltage boosting circuit for boosting a supplied first power supply voltage to a second power supply voltage used in a drive circuit of a display device, a capacitor provided between a power supply wiring for outputting the second power supply voltage and a ground, a logic circuit for outputting a high-level signal when the first power supply voltage and a supplied first control signal are at a high level, a delay circuit for outputting a signal obtained by delaying an output signal of the logic circuit as a second control signal used for an operation control of the drive circuit, and a resistor provided between an input terminal of the delay circuit and the ground. The power supply circuit may include a first diode on the power supply wiring, or may include a second diode having an anode terminal connected to an output terminal of the second control signal and a cathode terminal connected to the input terminal of the delay circuit.