DC Converter Needed 1

[HarryRai]

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

 

[Renovator1]

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?

 

[bhuvan]

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

 

[marginal]

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.

 

[itsmoked]

Ahh.. You just have to look in the right places..

Here you go:

http://www.linear.com/pc/downloadDocument.do?navId=H0,C1,C1003,C1424,P49779,D25690

Keith Cress
kcress -

http://www.flaminsystems.com

 

[Madcow]

you beat me to it again, itsmoked.

here is another one

http://www.national.com/pf/LM/LM5118.html

 

[itsmoked]

muwhAHAHAAAAaaaaaa.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[DHambley]

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

 

[Renovator1]

^^^^ 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!

 

[itsmoked]

Dang I missed that step-up would be needed.

Get out the parts bin.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[Fluorescence]

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.

 

[fsmyth]

http://hmin.tripod.com/als/andysm/pages/sw-regs6.html#DWN62

Find the SO version of the 494; it is roughly the same size
as a SIP8 device. Adjust the 5.1k to pin 1 as necessary.
<als>

 

[GonzaloEE]

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

 

[DCLabs]

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