I'm currently building a circuit used in a personal portable cooling system.
The fan is a 12v turbine fan (0.1A)
My plan is to use 2 9v batteries in series to give me 18v then use a buck-converter to step the voltage down to 12v.
My question is, if I have a switch between the turbine fan and the output of the buck converter, and turn the switch off, will the buck converter its self still slowly drain the batteries?
Or would it be best to have the power switch between the batteries and the buck converter?
Ideally due to the way the product will be implemented and used, it would be more user friendly to have the switch between the buck-converter and the turbine fan however if this would drain the batteries even when turned off, then I will need to have a little re-think.
Best Answer
Since the Buck converter will be running, the battery will get drained, if the switch is placed after the DC-DC output. you had mentioned placing the switch at the output is convenient, you can use the switch to shut down the buck converter also.
Most of DC-DC converter IC will have shutdown pins, which will put the device to low power mode in which it consume very low power, so you can combine this shutdown pin and the switch to reduce the power drain of the battery significantly