Best approach to switching 12V in low-power MCU application

[Tuppe]

Hello,
I'd like to ask just a quick sanity check question about my approach in my design.
I'd need to know what is the most reasonable solution to switching high loads, such as 12V solenoids/relays within low-power(e.g. battery powered) system?

I'm planning to use 3.3V MCU(to save idle consumption), for which the load is driven with a boost converter. Is this unreasonable solution for proper electronics design?

Should I run the whole system under 12V and constantly buck the voltage for the MCU?
For some reason I couldn't be able to find 3-5V water valve.

In my application the load is going to be switched under a minute at a time and 5-10 times per day, but I'd like to know that when professional opinion about in which case it's wise to use a boost converter... For example, if the load is switched 50% of the time, is it wiser to use 12V system voltage instead or some other solution?

Thanks for reading!

 

[KlausST]

Hi,

There is no general answer. To calculate an optimized solution we need a lot of values.
All of battery (chemistry, voltage, capacity...and mor if you have)
All of load and control circuit

I suppose the power for the valve is much more than for the control circuit. Then i'd use an extra bosst regulator for the valve.
You might control the valve by using the "enable" function of the boost converter. But some boost converters can not swit h off the load completely - but you need this. Check datasheet.

Klaus

 

[Tuppe]

Okay, thanks Klaus for the info. Atleast I know that using boost converter for a 12V solenoid is a viable solution. I just wanted to make sure there isn't a better method that I've never heard before...

I suppose the power for the valve is much more than for the control circuit. Then i'd use an extra bosst regulator for the valve.
You might control the valve by using the "enable" function of the boost converter. But some boost converters can not swit h off the load completely - but you need this. Check datasheet.

I planned to power the entire boost converter using output transistor when needed. I don't see why I'd need it being on standby all the time.

What about if I had mains power at my disposal? Should it still make sense to use boost converter with 3.3V system voltage? As you said, it would depend on the application, but it would still a sensible option, right?
Because I need to have either regulator & regulator or regulator & boost-converter, so both should be sensible options just depending on the application?

 

[KlausST]

Hi,

Technical data are still a secret...

I don't see why I'd need it being on standby all the time.

If the smps controller has an "enable" pin, it is the easiest way to control the valve.

3.3V system voltage?

For the valve use the battery voltage and a boost converter. Don't use two regulators in series.

Klaus