Switching Regulator System.

I may be way off beam here...

Seems the battery is always driving the switching regulator which will consume power even when not driving the payload.

I'd throw away that part of the circuit. Set the solar array/regulator output to just above the max output volyage of the batteries and just diode OR the two (battery & solar/regulator) together....

That way the solar will always drive the payload if it is giving enough output...If solar drops out batteries take over.

It is V easy to forget to allow for the quiescent current in battery circuits...this is going 24/7 and can rapidly flatten a battery.

Sorry if I've oversdmplified or missed some thing as I only jsut glanced at the cct...(can't really read it....to blurry)

yeah, the original is crisp and clear, when posting here it got all messed up.

if you wish i can e mail it to you.

but I thought that a "Switching" type regulator uses zero power unless it's needed to do so. or am i led to belive wrong?

Joe
Near Space Sciences

there's a way it can be done... I suggest you post your pick in an MSN group forum or some other forum that will clearly show the detail and provide a link for members and non members to reply.

here's the location of the image,

http://www.qsl.net/wb9sbd/regsystem.jpg

Thank you very much.

Joe

I thought that a "Switching" type regulator uses zero power unless it's needed to do so

Del the cat is right, there's no free lunch... You have to set the output voltage of solar side regulator a bit higher than the battery voltage, connect them together via two low-drop fast diode (Schottky) and then set the necessary payload voltage with the second switching regulator.

I thought that a "Switching" type regulator uses zero power

Check the IC manufactures data sheet for quiescent current... I'll bet you a pint it isn't zero! (I'm hardly going to do it for you !)

You have to do the arithmetic with this sort of thing! You may be able to live with the quiescent...or it may flatten the battery before launch/lunch whichever is appropriate!

The whole concept seems odd unless this is a one off mission type thing...in which case reliability and weight are probably also significant. Both these will be improved by discarding half the circuit!

I will stick a note in here, that due to the application removing the two LEDs on the output stages of the switching power supplies (which are continuously drawing mA of current) would be a great start to extending the usable life of the batteries.

Battery circuit R1 and D2 are general protection devices and can most likely be removed (can AMC34063A really not handle the open circuit voltage of the 15V battery pack).

Just some points (there are plenty of ways to optimise the circuit for this specific application). I await more information on payload from the original poster.

Del/s right, you can remove half the circuit.? it will take some working, but, you can. if you're creative enough you can do it at a small cost. say, around a few pico Amps of draw... even smaller costs... but slightly more weight.

Your design shows the battery is always on with the solar unit making an added total of 23V supply? Its a very bad design in terms of switching.

what does the payload consume? and what is the nature of that power use... both smallest need and largest need?

um, guess, I think you were suppose to say increased combined potential amps, and the battery plays a supplementary role.

The Switching regulator will draw power from the battery unless it is disabled. Even then some of the ICs still draw a few uA. You have a couple of choices. 1) you can use an enable/disbable to enable one switching circuit at a time based on the output of the solar array. 2) you can use a single switching regulator and select the input source based on the output level of the solar array. Option two is better because you can eliminate the entire second switching regulator circuit. If you chose option two and diode "OR" the sources you will lose a little power in the diode. If you are in a real battle for power savings a saturated MOSFET switch will work well to save power in the input switching circuit.

We here thank You ALL for the help thus far. Maybe a bit of background is in order.


Please read on below. Yes I know it's a somewhat long, but please do. It explains what we are attempting to do.

I am the founder and program director of something called Near Space Sciences. We are a totally non-profit group of people that offer to students of all ages the chance to do actual "Space Exploration" Non-Profit is putting it mildly, most of our flights to the "Edge Of Space" send to the "Edge Of Space" , several hundreds of dollars of electronic equipment, and we do it all at no cost to the school or it's students.

Please take a visit to our website to see some of the fantastic imagery and programs we offer to the Schools and Students. It's at. http://www.qsl.net/wb9sbd/educators.html
The above link is our preferred site to view, but sometimes that server is flaky,, if it doesn't work check out a stripped down mirror site at http://www.mwt.net/~mayen1/educators.html

Our last Mission to the edge of space happened just a few weeks ago, on May 21^st.

We had a launch for several hundred boy & girl scouts at the Sauk County Wisconsin fair grounds.

This was our 43^rd flight to the "Edge Of Space" This flight made it all the way up to

102,528 feet! Yes One hundred two thousand, five hundred and twenty eight feet UP!

A short video of the launch can be seen at,, http://www.youtube.com/watch?v=NoUkgWOUbNQ


Ok, we have been asked many times by many groups to do a LONG duration flight. Most of our flights last three to four hours. But to do a LONG duration flight is way past our budget. It requires NASA type of funding for the balloon itself will cost several thousands of dollars. So sadly we have had to tell the students that it is beyond our possibilities. But recently we have been doing research on methods of a long duration flight.

One of the long term goals of Near Space Sciences is to achieve the ability to stay airborne for days-enough time to cross the Atlantic Ocean. Right now, we launch balloons that self destruct after 3 hours and rarely travel more than 300 miles from launch to touch down.

We think we have figured out a system to do this for some students.

But now we must have a power system to make the longer journey. hence the need for what we are trying to do. The battery will be a backup system for minimal beacon type of powers during the night. Once the sun comes back up that we can take as much power as possible from the solar array first. We are not looking at huge amounts of power here, less than a amp at 15vdc.

So we are willing to start over totally from scratch. if anyone has a design that will do what we want..

Anyone?

Joe Mayenschein
Near Space Sciences

To do a serious design we need to know EXACTLY what the load is..eg what voltage range it will work over, current requirement etc...ideally a full spec sheet, the nt he same for th battery pack and the solar panel....

Also how long it must be able to run for.

It should be relatively simple... but only when all the information is there.

Two words.... aim for these.

Simplicity and reliability.

If this info' is available, someone may help out... (I don't mind having a look..but I never make promises unless I will keep them...so no promise at this point)

Good luck Del

Ok,

Will post power demands when we finish the payload.

Everyone Thank You.

Joe

Hi

Too easy

Get rid of all regulation for the solar panel.

Connect panel output via diode to the junction of D1 & R2 on Lithium battery circuit.

Enjoy!

BernieB