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iPhone display circuit repairing

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This video mainly explains the working principle of the display circuits of iPhone 11 Pro and Promax

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Let's first understand the characteristics of the displays of these two models

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Both iPhone 11 Pro and 11 Promax use OLED flexible screens

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The flexible screen is characterized by self-illumination

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The display power supply is not installed on the mainboard, but on the screen cable

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So we can't find the display power supply in the mainboard

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Display circuit working principle

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Step 1, when the battery is buckled or the adjustable power supply is connected,

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the main power supply will be generated

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The main power supply will provide the working voltage for the display,

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mainly to provide power for the display power on the screen

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Step 2, when we trigger the switch,

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the main power supply will first send 1.8V power supply to the display screen after receiving the power-on signal

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And then sends 3V and 1V power supply to the display screen to provide it with working voltage

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Step 3, when starting to the display circuit,

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the main power supply provides a 32KHz clock signal for the display

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Step 4, after the main power supply outputs the clock,

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sends a reset signal to the display

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Step 5, after all the working conditions of the display screen are normal,

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the CPU will send an interrupt signal to the display screen to notify the display screen to receive display data

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Step 6, after the CPU sends the interrupt signal,

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it will send display data to the display screen through the MIPI bus,

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and the display screen will display the image at this time

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Step 7, after the display is normal,

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it will send a TE signal to the CPU to prevent the dislocation of the display screen

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Among other detection signals,

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PANICB is the identification signal of the main power supply detection display screen

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If there is a problem with this signal,

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it will cause the assembly screen to be displayed,

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but the original screen will not be displayed

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ADCMUX is the signal used by the main power supply to monitor

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whether the power supply is working normally on the screen

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When the display power supply is working normally,

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it will send this signal to the main power supply

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If there is a problem with this signal, it will also cause no display

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PANEL_ID, identification signal,

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which is the ID used by the CPU to identify the display

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BSYNC is the touch synchronization signal sent by the display to the CPU

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If there is a problem with this signal,

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it will cause the display and touch to be out of sync

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In the working principle of the display circuit,

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if there is a problem with one of these signals,

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the screen will not display

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When troubleshooting no display failure,

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we need to measure all the working conditions of the display

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Ok, that's all for this video