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I found some documentation about it but not exactly what I want:

Charge a laptop without explicit USB PD capability using USB PD

Does a USB PD source supply any voltage to a non USB PD compliant USB C device? If yes, how much?

Battery charging over USB-C (using USB-PD?)

The question is: Is it safe to charge/ plug DC-IN laptop (19.5V, 6.67A) with a USB PD 100W cable ? I'm not talking about plugin it in the USB-C port but really on the usual DC-IN laptop input port.

I have the proper 100W charger which goes with it and I bought also a USB-C - DC-IN power adapter. Will it work and is it safe ? (Maybe the PD cable will go default at 5V1.5A, so is it safe or it can burn something ?)

Thanks

Balobiana
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Safe is defined in 2 ways. Generally and Manufacturer approved.

No it is not safe according to the manufacturer. It's a non standard supply. Warranty could be denied. House catch on fire. Cats and dogs living together. According to the manufacturer.

Generally, it's probably okay. If your supply meets the voltage and current requirements, if it's clean and noise free, if it can support any current inrush surge. There is nothing particularly special about your average laptop power supply. Your PD supply being able to produce different voltages can be an issue if the trigger mechanism malfunctions, so quality is important. But the same quality issues apply to anything really.

Undervoltage like defaulting to the 5V is generally not ideal but probably won't cause harm. It would be better if the adapter does not pass through the voltage until it negotiates the proper voltage level though.

Side note your original supply is over 100W. Unless your laptop also accepts lower wattage supplies and your usb-c adapter signals that, then you shouldn't use it. If the laptop tries to pull more current than available it can lead to bad things.

Passerby
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The question is missing some details about the "power adapter" components involved, but in general using a generic DC power supply to charge a laptop is not a good idea and can damage the laptop. I'm assuming the power adapter is not approved by the laptop manufacturer, so I don't recommend it. Laptop battery charging circuits have specific input voltage and current requirements that must be met to operate properly.
Summary based on OP.

  1. Laptop does not support USB-PD charging, but instead only has a DC input jack for battery charging. The AC-DC power supply that came with the laptop has output rated for 19.5 VDC and 6.67 A maximum, which is 130W maximum. (Power = Voltage * Current)
  2. Desire to charge this laptop instead from a USB-PD 100W rated power supply and a 100W rated USB-PD type-c cable.
  3. Purchased a "USB-C - DC-IN power adapter" that has USB PD Type-C input and provides a DC output (ratings not specified).
    Question: is the DC output in this configuration suitable for charging the laptop?

Some potential pitfalls with the proposed setup that need to be checked:
A. The laptop normally uses a 130W power supply, but the proposed USB-PC power supply is only rated at 100W. This may result in the laptop to attempting to draw more current than the power supply can provide, but only the laptop vendor would have enough information about the charging circuit to know what would actually happen.

B. the output voltage and current (or power) specifications of the "USB-C - DC-IN power adapter" must be compatible with the laptop charging input specifications. Does this power adapter have a switch to select the DC output voltage? and if yes, can it output 20V or 19.5V? Selecting the proper output voltage is absolutely required. Also what type of cable will be used from the power adapter to the laptop DC input port, and what is it's rated max current? Many modern laptops require an electronic ID signal from their power supply (in addition to the DC power) to validate how much power is available. Does your laptop require such a signal? My laptop will operate from a DC input of the correct voltage, but does not charge the battery without the proper electronic ID present.

C. Assuming the USB-PD to DC power adapter is a "USB-PD trigger device" that simply requests/negotiates a certain voltage from the USB-PD power supply and then passes the VBUS power straight through to a DC load, the USB-PD supply itself must be able to supply the required 19.5VDC (or 20V). Check the specifications of the USB-PD charger for supported output modes, although all USB-PD chargers supplying over 50W should support a 20V output mode.

BK303
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It may work but beware of capacitance surge current effects.

The USB contacts when flash gold plating will burnout and get hot or as in the case of Lightning connectors burnout the gold to black then burn out the copper substrate even with 5V to an iPad with a few hundred surges connections.

But if the demand current is negotiated after contact, this negates the arc current.

Tony Stewart EE75
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