I am under quite some time pressure and I need to put together a document about how several DC/DC converters (preferably buck) with digital control compare to each other. I am pretty clueless, I have already pored over tons of datasheets, but I got little useful data, most of the converters out there have analog control. (Maybe I'm just so bad at finding anything on the web…)
What I need is something like the UCD74106 from TI. It should have an external PWM input which can come from e.g. a microcontroller.
The specs I am looking for are:
- V_in = 48 V
- V_out = 1.3 V to 24 V (programmable)
- single input/single output
- can be paralleled
- any power range
It would be nice to have datasheets with efficiency curves. Something like 'typical efficiency is blah-blah %' is not very helpful…
EDIT: Other examples of what I have in mind: NDM1-12-120 and NDM1-25-120, both from CUI
EDIT 2: I need the efficiency curves to see how the converter behaves at partial load. Also I am interested in finding the (approximative) load current at which the maximum efficiency is achieved (usually below rated current).
And yes, I need digital control! This has been explicitly stated in my assignment… The idea is to be able to reprogram the converters whenever necessary and to make them SMB/PMB capable.
I listed the datasheets to show, what I have found so far and to give an example of what I would like to have. Unfortunately 3 are not enough… I'd need a dozen or so.
Best Answer
Two things to think about.
First, even "analog" power supply control chips can be "digitally controlled", whatever that really means. A little external tweaking of the feedback and the output voltage can be varied. Many have shutdown inputs, but of course that can be accomplished other ways too.
Second, for fancy switching power supply control you can use a microcontroller directly, and obviously have all the digital control you care to program in. There are whole families of microcontrollers specifically intended for this sort of application. They have fast A/Ds, decent computer power, and fancy PWM modules that not only have high resolution but additional features like external shutdown modes, complementary outputs, etc. Check out the dsPIC 33F line from Microchip. All the high end switching power supply applications we've dealt with in recent years have had a microcontroller doing the closed loop control. Dedicated chips are more for simple power supplies, like running the microcontroller.