66% or better

Building a bipolar supply from a boost converter

This DC-DC Bipolar PSU was developed for use with a guitar effects pedal. [Obsolete Technology] needed to source both positive and negative 15V. This is pretty easy to do if you’re converting from mains, but he wanted a solution that could work with a lower-voltage AC/DC wall wort or even from batteries.

The part that pulls it all together is the LT3467. It’s a switching power regulator which offers a range of features configured by the layout of a handful of external passive components. It can put out 80 mA on each line (positive and negative). Also extremely useful for this application is the chip’s high frequency operation. Depending on the version, it switches at 1.3 or 2.1 MHz. This is high enough that it will not introduce audible noise into the audio system.

We’ve got an exercise bike whose negative supply for the LCD is blown. We’re going to try build this circuit, trimming it for our voltage needs, and get the contrast working again.

[Thanks Olli]

Comments

  1. Chris C. says:

    This thing on? I thought for sure a switcher running at such an unusually high frequency would illicit some interesting comments.

    And if not that, then surely someone else has noticed that Mike’s been hitting the homebrew. “Wall wort”, heh.

  2. Garbz says:

    1.3MHz will not introduce noise in the audible spectrum, that is true. But then neither will pretty much any other competently designed switcher at frequencies several orders of magnitude lower.

    The high frequency would place quite a serious restriction on component selection too.

  3. Tempestion says:

    I think that unit is rated for 100ma/ch not 80, cant see any limitations in passives to permit the 20ma difference. 1.3Mhz isnt really uncommon for most high efficiency switchers, I use 1+ Mhz reguarly in my design work. They’re a real pain for EMI though

  4. DainBramage1991 says:

    I hope that thing is in a shielded enclosure, because it’s likely to be producing a ton of RFI right across the top third of the AM broadcast band and all the way across the 160 meter ham band.

    Not a good way to make friends.

    • anyone says:

      I’d like to see what this puts out too. It might not be that bad or it might be really bad lol.

      BTW hackaday ops, I accidentally reported this comment and didn’t mean to. ummm…so please undo that “alert” as DainBramage has a legitimate comment.

  5. nxpguy says:

    Beautiful and so low cost, i’m going to build a few of these for my students in the analog lab, so they will power their projects from their laptops USB.
    Adding a few ferrite beads on the input and outputs and redesigning a more compact board will calm those who bother about EMI

  6. anyone says:

    I’m surprised at the lack of comments too. I guess because this site it usually littered with the same trendy adurino bullshit everyday, power supplies are overlooked.

    Thanks for posting. I have never used the LT3467 and now I know about it.

  7. NewCommentor1283 says:

    is that thing LEGAL?

    turn that thing on and expect the FCC to show up!

    i mean without a metal, grounded, case and ferrite beads on ALL the wires. extra inductors and capacitors maybe too.

    i had various suspicious vechicules circle when accidentaly jamming up a “small” portion of the VHF band… (bad homebrew tx) this thing would supposedly arouse more angry people, more quickly.

    my guess is he lives either in the middle of nowhere (noone 2 interfer with), or in the middle of a big city (anonimity)

    PS: in my country, VHF (TVband) is becoming the new CB band… noone is using it much as the new ATSC / digital-over-air is almost nonexistent. and analouge is reduced in sterength so only people within short distance can pick it up

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s