Voltage Regulating:Large input range

[SLK]

Hello,

I am relatively new to power electronics, so I am hoping that I would
get some help.

I am trying to design a power circuit that has an input range of
approximately 10 to 85 V DC. The desired output voltage is 12V at
about 2-3 Amps.

If anyone anyone could help me with any suggestions, I'd really
appreciate that. The nearest I came to was Maxim MAX5003 IC which has
the wide input range but locks below 25V. Is anyone aware of any part
that would pass the whole range or is there any way I could switch
between the MAX and another power circuit based on the input supply?

Thanks in advance,
SLK

 

[Robert Baer]

Hello,

I am relatively new to power electronics, so I am hoping that I would
get some help.

I am trying to design a power circuit that has an input range of
approximately 10 to 85 V DC. The desired output voltage is 12V at
about 2-3 Amps.

If anyone anyone could help me with any suggestions, I'd really
appreciate that. The nearest I came to was Maxim MAX5003 IC which has
the wide input range but locks below 25V. Is anyone aware of any part
that would pass the whole range or is there any way I could switch
between the MAX and another power circuit based on the input supply?

Thanks in advance,
SLK

Since the input voltage can go below the desired output, a composite
buck-boost or Cuk circuit seems advisable.
There are a lot of BICMOS switchmode regulator ICs that work; the
UCC2801 has a turn-on threshold of 9.4V and is specified at 10V supply.
The neat thing is that it has a built-in zener (about 14V if i
remember), so a series current limiting supply resistor (30mA max) helps
to achieve the wide range.
Check out the UCCx800/1/2/3/4/5 series from TI.
Besides, TI actually *makes* and *sells* the parts they advertise;
Maxim has a nasty habit of not providing a number of their advertised
parts, and distributors cannot even get samples.