How USB-C charging works? Lenovo Yoga7

[ktmmotocross]

Hello guys.
As there are more and more USB-C charging laptops i want to ask if somebody know how to diagnose it or how it works.

as example i have this Lenovo yoga 7 nm-D131 that not detect charger so charger voltage not goes up to 20V but stay at 5V and no current passing

[mon2]

Re: How USB-C charging works? Lenovo Yoga7

Power delivery is about single wire communication of the BMC pins (CCx) on the Type C connector.

Often these pins / contacts get damaged due to cross shorts during pulling / insertion of the type C connector at an angle.

Remove all power. Meter in diode mode.

Red meter probe, yes red, to ground.
Black meter probe to point to test.

Check the diode readings of:

TBTA_CC1
TBTA_CC2

TBTB_CC1
TBTB_CC2

The first point of contact from the outside world will be the power delivery controller onboard. This is often a stand alone device that negotiates the power delivery contract with the external power adapter. Be sure that the external power adapter is suitable to power the board (suggest 100W or higher). The adapter does not have to be the original but should be a known good one.

We used the model from LVSUN for years (purchased it for $20 USD at the HK fair). Worked fine till some scum in California sold us a defective macbook logic board with pulled parts and BGA shorts. Ebay refunded the entire purchase but it killed our power adapter.