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Hello everyone, today we continue to analyze the timing of the Wistron 15221 motherboard.

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In the last lesson, we talked about the generation of the common point.

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The position number of the current-sensing resistor in the circuit is PR4402

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Both the front end and the back end of the resistor are connected to the charging chip

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The current flowing through the resistor is detected by the charging chip

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Let's look at the circuit diagram

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The first pin ACN and the second angle ACP of PU4404 are current detection pins

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They are respectively connected to the front end and back end of the current sense resistor

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The front end of the current-sensing resistor is called ACP,

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and the back-end of the current-sensing resistor is called ACN

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let's see the real thing

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I just found out through the circuit diagram that the first pin of the charging chip

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is connected to the back end of the resistor

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The second pin of the charging chip is connected to the front end

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of the current-sensing resistor, also called (ACP)

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After the power supply of the adapter is turned on through the MOS tube,

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it flows to the common point through the current detection resistor

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For example, the voltage at the front end of the resistor is 19.1V,

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and after passing through the resistor, it becomes 19V

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What is the current flowing through the resistor at this time?

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By Ohm's law it can be calculated

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Divide the voltage difference across the resistor by the resistance of the current-sense resistor

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Its resistance value is R010 written above, and the actual value is 0.01 ohms

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Through this calculation formula, it is finally calculated that the current flowing through the resistor is 10A

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The charging chip is charged by detecting the voltage difference across the resistor

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Real-time detection of the current supplied by the adapter to the supply point

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When there is overcurrent or short circuit at the common point,

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the charging chip will control the adapter isolation tube to cut off

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Because the common point has overcurrent and short circuit,

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if the adapter continues to supply power to the common point,

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the scope of the fault will be expanded.

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Therefore, when the charging chip detects the overcurrent of the common point,

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it will control to close the adapter isolation tube and prevent the adapter

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from continuing to supply power to the common point,

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so as to achieve the purpose of protection