# Simple circuits 1.5 V DC to 9 V DC

Anyone got any super simple circuit designs for converting 1.5 V DC to 9 V DC? Maybe something that uses a couple of transistors would be good?

• Why do you need 9V DC? I hope it's not to feed it into another power regulator which then regulates it down to 5V
– davr
Dec 22, 2009 at 16:24
• how much current do you need? 10mA? 1A? what's your input range? (1.5V +/- ____ ?) Dec 22, 2009 at 16:42
• @Michel Keijzers please stop making silly edits to ancient questions Dec 18, 2018 at 20:10

If you just need a few milliamps, it looks like maybe the NCP1403 would do. Otherwise, TI doesn't seem to have anything besides the TL499A; maybe Linear Tech or Maxim or Micrel or National Semiconductor would have something useful.

edit: Linear has the LT1615-1, looks promising but pricey as most of Linear's stuff is. I don't like Maxim (have been burned by pricey unobtainable products too many times).

National has the LM2621.

Consider using the 1.5V of an AAA battery directly, along with a low-voltage version of a 555 (e.g. TLC551 -- not a typo, it's a little different from TLC555 -- or LMC555 or ZSCT555), and a buzzer/piezo rated at 1.5V.... the latter is kinda difficult to find (I guess they spec 15Vp-p usually) and we ran into the same problem on a project at work. You'll get twice the peak-to-peak voltage if you drive both sides of the piezo. Drive one end from the 555 directly, the other end from an inverted version of the 555 output: pick a 74xx14 from a logic series that can run off 1.5V and has high drive capability. You can generally parallel up the output of inverters with identical inputs (for a home project fine, on a "real" project i'd probably put some 1-5ohm resistors in series to limit short circuit current somewhat)

It may not be as LOUD as running the piezo off 9V but maybe that's ok.... :-)

• Thanks for all the extra info! I'm just trying to power a 555 timer with a AAA battery, the timer is hooked up to a piezoelectric buzzer less than a centimeter wide, it's a little square wave buzzer type thing. I'm just trying to keep it small so I can mount it in a badge, it's a project I'm doing with my little brother.
– Jim
Dec 22, 2009 at 23:10
• oh! In that case, you might want to consider looking at a different version of the 555 + a buzzer, something that would work on a single AAA battery. It would save you the efficiency hit of a switching converter. Dec 22, 2009 at 23:53
• ...e.g. TLC555 works off of 2V (focus.ti.com/docs/prod/folders/print/tlc555.html), not quite but almost there. Dec 22, 2009 at 23:54
• Cool I'll probably look for both, I'll go to my local electronics store today and see what's available. The 551 sounds good, but I'd also like to try the voltage controller method also, I don't need the battery to last that long.
– Jim
Dec 23, 2009 at 10:25

I did a brief review of the TL499A, and I believe (from the data sheet) it will do what you need:

http://focus.ti.com/docs/prod/folders/print/tl499a.html

There is a DIP package available, and the data sheet gives a pretty complete application example on page 4. Mouser shows these chips available for \$1.50 with plenty of availability.

You should definitely figure out your current requirements as well. Handy charts are in the data sheet to help you determine if this chip can supply the current you need.

• that's great Lou, it should do the job perfectly. cheers
– Jim
Dec 22, 2009 at 15:46
• Glad to hear it! It looks like you'll need to do some playing with the resistor values to get what you want, now that I look at the doc more closely, but once you figure out the resistances you can probably fix all that down with precision resistors. I wouldn't mind seeing the final values for future reference, this would be a great reference for battery-powered applications.
– Lou
Dec 22, 2009 at 15:49
• Hmmm. I'm suspicious. I like TI but the datasheet looks really weird for a switching regulator (where's the description of timing = either specified as a switching frequency, or via hysteretic control?), and it also looks like you need a VSERIES_IN1 that is at least 4.5V. Dec 22, 2009 at 16:40
• I did a quick web search of "TL499A 1.5v to 9v" and came up with this AVRFreaks article which deals with using a TL499A to get 9V from a AAA battery: avrfreaks.net/… Apparently it works, but the posters were getting better results with two batteries (3v).
– Lou
Dec 22, 2009 at 17:04
• yah, agreed -- efficiency in switching regulators always goes down when you deal with lower voltages in/out, or if you have a larger ratio between in/out voltages w/o a transformer (e.g. if the switching duty cycle is close to 0 or 1.). Dec 22, 2009 at 17:26

I had a look at the 551 timers and I don't think they will be that loud when hooked up to a regular piezo buzzer. So I've decided to try and boost the voltage, I couldn't find most of the ICs available locally at short notice, but I did manage to find some NCP1403s that can be delivered tomorrow. So I'll try them out with the trusty 555 timer and I'll let y'all know if it works well. The only thing I'm worried about is the lack of current!