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In this lesson, we will talk about which circuits are related to no trigger

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As we mentioned earlier, the relevant circuit is the power-on circuit

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The first is the battery

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The battery provides a positive voltage

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We said that it is 4.3 volts at its highest

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This battery supplies power to the MOS tube in the charging chip,

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which is turned on under the control of the charging chip,

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and outputs a main power supply called VPH_PWR, or VBAT_SYS

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The charging chip converts the battery into the main power supply,

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and this main power supply is supplied to the power supply chip

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At this time, the power chip needs to work on standby,

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and it will give a voltage to the power-on button signal

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This voltage is 1.8 volts for Xiaomi and Huawei,

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and the voltage of Oppo phones is equal to the battery voltage,

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it is about 4 volts

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When we give it a voltage of 1.8V,

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we press the power button

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the power button signal is called PWRON, or KYPD_PWR

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Xiaomi's power button signal is called PHONE_ON_N

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As for Huawei, generally these codes are the power button signals

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We connect the power button signal to the ground wire,

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which is equivalent to pressing the power button

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Here's 1.8 or 4.3 volts

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As long as it is pulled down to the ground, more than 5 seconds

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Then, the power supply will output power to the CPU，

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temporary storage and the hard disk

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At this time, there will be a current

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So no trigger is no current response

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What is it related to? W e have to distinguish

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It has nothing to do with the part on the right

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Generally, we only consider 2 parts

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One part is here, converts from the battery power to the main power supply

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And the other part is the power chip itself

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From the circuit is here, here

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Whether the positive pole of the battery is normal,

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the main power supply is normal, and whether the power chip itself is normal

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Because if the power chip is abnormal,

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it has no way to output voltage to the power-on signal,

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even if there is main power supply to it

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First, the positive electrode of the battery

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Second, the main power supply

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Third, the power chip

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The line from the battery button to the power chip, this is the fourth

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We only consider these four parts

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That is, whether the voltage of the positive electrode of the battery is normal

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After the positive voltage of the battery is normal,

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whether the main power supply voltage is normal

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That is, whether its voltage has been pulled down,

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whether there is a problem, and whether the voltage can not be measured

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After these circuits are normal,

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we will see if there is any problem with the power chip itself

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If there is no problem, after getting the main power supply,

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it will output power to the power-on button signal

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The next thing to consider is the line from the power-on button to the power chip,

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also called the power-on signal line

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When we repair no trigger fault, we only consider these 4 circuits,

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including the positive electrode of the battery,

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the main power supply, the power chip itself, and the power-on signal line

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The power-on signal line is the line from the power-on button to the power supply,

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Okay, that's it for this lesson