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DC Converter Needed

DC Converter Needed

DC Converter Needed

(OP)
I need a DC-DC converter which is capable of taking a wide input range from + 6-24 Vdc and giving a constant output of +9 Vdc, 150mA.

I have looked at various suppliers components and they all seem to have Vin ranges from 4.5 - 9 Vdc or 9 - 18 Vdc, and they're not suitable for my application purpose!!

the converter has to be fit on to a PCB a SIP8 package is needed.

any ideas of any device/converter that I might be able to use???

cheers

RE: DC Converter Needed

Bad news for you, HarryRai - I wanted the same thing several years ago - though I could have lived with 6-18V - and was forced to conclude that I'd have to roll my own. How about putting a shunt regulator in front of a standard 5V input DC-DC?

 

RE: DC Converter Needed

HarryRai,

Try the SEPIC converter. The x'fer function is:

     Vout/Vin = D/(1-D), where D = duty cycle

The circuit needs 2 inductors, and, the control loop is harder to stabilize than a regular buck or boost.


Bhuvan

RE: DC Converter Needed

Yes, that low input voltage is the problem for off the shelf findings.

What about one of those DCDC converters which uses two BJT's in a kind of multivibrator set-up, with the primary coil being used with a resistor and a cap somewhere to oscillate and get the primary current backwards-and-forwards-ing through the primary.

I've seen these often with low power dcdc's and they have minimal component count...and don't care too much about the low-end of your vin.

.....come to think of it, i just took apart a £1.27 compact fluorescent bulb and it had one of these two-BJT oscillators acting as a high frequency ballast in the base of the bulb....

...also, a recent company that i just finished with used one to provide an isolated 15V rail voltage in their new electric drive.

...and another  company that make electro microscopes still use them to this day.

RE: DC Converter Needed

The LTM8022 can not supply 9V out when you have 6V in. It is only a step-down converter, not a step-up.
The LM5118 is a buck-boost. It will work for your application. (that is, the LM5118 and 20 extra components)

DH

RE: DC Converter Needed

^^^^ ROFL!

Yeah, guys - don't forget all the extra components (and prototyping/debugging time) it takes when you want to roll your own here... Those little 1-2W encapsulated converters from V-Infinity, C&D, etc., sure are hard to beat when you consider price, pcb real estate and development time!
 

RE: DC Converter Needed

Dang I missed that step-up would be needed.  

Get out the parts bin.

Keith Cress
kcress - http://www.flaminsystems.com

RE: DC Converter Needed

for rolling your own........you could try a PIC micro acting as an oscillator (or whatever low component count oscillator you can get).

For PWM control, you need a flip-flop and two open collector comparators and a two input AND gate. If these three are not available on a single chip then that means using separate chips. Wire it up as a flyback

you can wire these up with one comparator switching on output overvoltage, the other on overcurrent, the flip-flop to avoid multiple turn on/off. and the AND gate to control the switch (AND gate fed from flip and also oscillator)......possibly use just a BJT at this low power...being driven on by the non CMOS AND gate...eg use 74 series

but at such low power the linear regulator looks good.

RE: DC Converter Needed

I'm trying to make a DC converter with a PIC16 or 32 for a local customer.  But that's another thread ;)

RE: DC Converter Needed

Use Madcow's suggestion (lm5118) or similiar IC. The LM5118 circuit would fit on a small pcb. Mount the circuit board vertically with SIP8 pin spacing. You might have some mechanical issues to deal with, but this would meet your specifications. I did something smiliar to this when replacing a 3 pin TO-220 linear regulator with a switcher.

DC

Dean Cooper
dclabseng.com

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