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iPhone display circuit repairing

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This video mainly explains the working principle of the display circuit of iPhone XS and XS Max models

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Before learning the principle, let's first understand the characteristics of these two models

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These two models use OLED flexible screens, which are characterized by self-illumination

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So there is no backlight chip in the mainboard

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And the display power supply of these two models is installed on the screen

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The picture shows the iPhone XS display screen,

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and there is a small iron piece in the middle of the screen cable

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After we remove the small iron piece,

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this IC chip is the display power supply

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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 screen,

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which mainly supplies power for the display power supply on the display screen

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Step 2, when the power is turned on,

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the main power supply will output more than 30 channels of power supplies

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Among them, the 1.8V power supply will first provide the working voltage for the display screen

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Step 3, when starting to the display circuit,

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the main power supply will output 3V, 1V and 1.1V power supply of the display

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The 1.1V power supply is converted by 1.26V through the conversion tube

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and then sent to the display screen

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Step 4, the main power supply starts to the display circuit,

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after outputting the power supply of the display screen,

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the main power supply outputs a reset signal to the display screen

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Step 5, after the display has power supply and the reset signal,

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the display power on the display starts to work

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After working normally, it will output a ready signal to the CPU

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Step 6, after the CPU receives the ready signal,

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it will send an interrupt signal to the display to notify the display to be ready to receive display data

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Step 7, after the CPU sends the interrupt signal,

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it sends display data to the display screen through the MIPI bus,

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and the display screen will display the pictures

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Among other detection signals,

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PANICB is the signal of the main power identifying the screen

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If there is a problem with this signal,

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the assembled screen can be displayed, but the original screen will not be displayed

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ADCMUX is the signal sent by the display power supply on the display to the main power supply

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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 this signal is abnormal, it will also cause no display

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PANEL_ID, this signal is the ID identification signal sent by the display to the CPU

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The CPU uses this signal to identify the ID code of the display

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In the working principle of the display screen, if a signal is abnormal,

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it will cause no display

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When we repair the no display failure, we need to measure all the signals

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Ok, that's it for this lesson