To check if you have the correct power supply/ charger for your computer, check on the bottom of the laptop and the bottom of the charger for the following things:
Look on the bottom of the laptop sometimes under the battery for the Volts and Amps.
Look on the AC adaptors for the Volts and Amps.
Volts x Amps = Watts "V x A = W"
Match the wattage calculations on the AC adapter, and the computer. If your wattage supplied by the AC power adapter is less than the requirement on the computer, you need a higher wattage AC adapter.
Example:
Dell M7520
Volts:19.5
Amps: 9.23
19.5V x 9.23A = 179.985 or 180watts
AC adapter for M7520 output:
Volts:19.5
Amps: 9.23
19.5V x 9.23A = 179.985 or 180watts