I am trying to build an UPS for my laptop. My laptop doesn’t have a battery and battery port is damaged, only way I can power my laptop is from the DC port. But the problem is where I live power outages are frequent and it becomes really annoying while I am working.
I made an UPS circuit that will be connected between the DC adapter and the laptop, the circuit will be connected with 4s lithium-ion battery and includes a boost converter to get the needed voltage. So the circuit will switch between the battery power and the adapter.
I have provided the schematic here:
The problem I am having is while switching from the adapter to battery. The circuit is working fine, when I simulate a power outage, it switches to battery power, but there is a slight delay of about 0.5 sec to 1 sec, which means my laptop turns off, defeating the purpose. (I don’t know why it’s happening) I want it to switch instantly.
I have used a 6V relay to do the switching and used this mini buck converter to power the relay also added a free wheeling diode (not mentioned in the schematic) to protect the buck converter.
This is the boost converter I used.
The circuit can only charge or power the load; it can’t do both simultaneously. The charger is disconnected via the DPDT switch. This is the charger I used.
The SR560 Schottky diode is used to prevent reverse current flow to the boost converter and the adapter. And a 1000uf capacitor (not mentioned in the schematic) on the output to smooth out the voltage.