Assume that the battery capacity is sufficient.
Desktop power output has several different voltages:
+3.3V: Motherboard
+5V: Circuits other than the hard disk and light drive motor
+12V: hard disk motor, fan, and other.
-12V: indicates some ancient serial port circuits
+5V usb keyboard switch the machine on and off
The power distribution of each appliance is very accurate and complex, and it is not a simple 12V connection, so if you want to use it, you can not spare the power supply.
Therefore, only the inverter can be raised to 220V AC voltage
notebook
For mainstream brands, the voltage is not enough, so two identical batteries can be connected in series, and the voltage is adjusted with a vacuum regulator circuit. Or a battery plugged into a booster plate