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iPhone display circuit repairing

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This video mainly explains the working principle of the iPhone 12, 12 Pro, and 12 Promax display circuits

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Before explaining the principle,

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let's first understand the characteristics of these three models

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The working principle of the display circuit of these three models is the same,

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but the pins on the display connector are different

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The iPhone 12 series uses OLED flexible screens,

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so there is no backlight power supply in the mainboard,

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but there will be a display power chip in the mainboard

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Step 1, when the switch is triggered,

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the main power supply will output more than 30 power supplies,

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of which 1.8V power supply will provide the working voltage for the display screen

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Step 2, when the CPU working condition is normal,

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it will detect the display screen through the I2C bus

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Step 3, when starting on the display circuit,

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the main power supply sends out 3V, 1.2V and 1.0V power supply for the display

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Step 4, when starting to the display circuit,

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the main power supply is sending a clock signal for the display

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Step 5, the main power supply sends a reset signal to the display

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Step 6, after the display has power supply, clock signal and reset signal,

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the small circuit on the display starts to work,

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and sends power supply start signals VOUT12_EN and VOUT3_EN for the display power supply

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Step 7, after the display power supply receives the start signal,

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it will output PNVAR -7V power supply and PP4V6, PP7V3 power supply to the display screen

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Step 8, after all the power supply and working conditions of the display screen are met,

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the CPU will send a MIPI bus start signal to the display screen

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to notify the display to be ready to receive MIPI bus data

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Step 9, after the CPU sends the display data to the display,

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the display screen can display images at this time

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Step 10, after the display screen works normally,

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it will send a TE image synchronization signal to the CPU to prevent screen misalignment

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There are two other detection signals in the circuit diagram

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PANICB is the identification signal from the display power supply to the display screen

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The signal is sent from the main power supply to the display power supply,

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and then it is sent to the display screen

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If there is a problem with the signal, it will be displayed normally when using the assembled screen,

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but not when using the original screen

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PANEL_ID is the screen ID identification signal,

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which is sent from the display to the CPU to identify the ID code of the display

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In the working principles of the display screen,

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if there is a problem with one of these signals,

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it will cause no display fault

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During maintenance, it is necessary to measure all the working conditions of the display

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Ok, that's all for this video