Step-up and step-down power supply

[ericmar]

step up power supply

Hi,

I plan to use either 4 cells of alkaline batteries (4 x 1.5V) or an AC adapter of +9V @ 2.2A as the main power source and step-up, step-down this power source to create few different voltage supplies (+12V, +3.3V and +1.8V).

My problem is should I be stepping down the +1.8V from the main power source or stepping down from the regulated +3.3V (which is first step-down from the +9V). This is because the voltage difference between +3.3V and +1.8V is only +1.5V while the voltage difference between the +9V and +1.8V is as high as +7.2V. I think there will be waste of energy for such a conversion, right?

How should I arrange it such that the power efficiency is optimum?

I decided to use a boost converter to step up the power source to +12V. As for the step-down part, I am not sure whether to use a Linear Regulator or a Buck converter to perform the step-down. Linear Regulator is easy to be used but the efficiency maybe lower. A buck converter can achieve much better efficiency but more complicated to build. Any suggestions?

Thanks for any help in advance.

Regards,
eric

 

[DrBob13]

Hi,
Personally I would use separate buck regulators from the raw supply for each of the step down voltages.
Bob.

 

[desertkids]

since you are using boost converter to step up to 12v, then it's better use boost converter to step down...and step down to 3.3V 1st then to lower voltage later.normally i do like this la...

 

[bryanwizard]

you can use charge pump for your 12V and use adjustable regulator for your 3.3volts