gsich parent
Lenovo uses a resistor to check the PSU power, should be easy enough. Don't know what Dell is doing.
Looks like a one-wire protocol talking to a DS2501 chip
https://hclxing.wordpress.com/2014/02/09/hacking-a-dell-powe...
The author got almost everything correct except some minor parts. Using his charger as an example, it can be broken down as:
DELL 00 AC090 195 046 CN09T2157161543835EAL 03 .
046 is the output current 4.6A instead of his partitioned as 46(there are power supplies output more than 10 amps).
The 22 bytes is the Dell PPID, which should be also present on the charger's label or the box: CN: Manufactured in China, some of them are TH which means made in Thailand. 09T215: Dell Part Number. 71615: Manufacturing factory code. 438: 2004 or 2014, March, 8th (Dell use YMD 3 bytes thus it is a lossy conversion always). 35EAL: This should be the serial number.
The last part 03 is a CRC16 (x16 + x15 + x2 + 1) checksum.