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Thread: Higher current voltage doubler

  1. #1
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    Higher current voltage doubler

    The Godlyke Iso has decent current output listed in the specs - maybe uses a switched inductor rather than charge pump? Does anyone know what is used? Looking at doubler/programmable IC specs I haven't come across any step-up devices that handle this kind of current. Plenty of high-current step-down, though.

    Godlyke Iso-Pump Voltage Converter | Godlyke Power Pump

    EDIT: just seen the LT1372 which looks like a pretty good candidate.
    Last edited by Mick Bailey; 09-05-2017 at 12:45 PM.

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    Here's an update;

    I bought some CS5173 devices and breadboarded an 18v converter. It works superbly and I can pull 500mA. These devices operate differently to what I'd assumed; You don't get a doubler - you preset the output voltage and the device maintains this regardless. So if you want 9v to 18v a simple resistive divider across the output sets the output voltage via a feedback loop where you need it. Now, if the input voltage drops, it maintains the output voltage and compensates by pulling more current from the input. For such a tiny IC I think it's pretty impressive. I'm mixing SMD and through-hole right now, but the circuit could be made really tiny with full SMD. The inductor is the only thing that's a little clunky - it needs to be relatively high current at 2A. All rather inexpensive, too.

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    That's a one nice chip you have there.
    I'd expect something along the MC34063 lines if that was a mass/asian product, but that's just a guess. Your chip looks 100 times less headache in comparison.
    Last edited by darkfenriz; 09-08-2017 at 11:55 AM.

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    Quote Originally Posted by Mick Bailey View Post
    ...CS5173 devices...
    560 kHz? Wow. I hadn't realized that today's switch-mode power supplies had switching frequencies all the way up in the old AM radio band!

    -Gnobuddy

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    No wonder I can't find a place in the house to play my @$&#ing Tele... dammit.

    Justin
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    Senior Member Enzo's Avatar
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    SMPS even run into the Megahertz these days.
    Education is what you're left with after you have forgotten what you have learned.

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    Quote Originally Posted by Enzo View Post
    SMPS even run into the Megahertz these days.
    Crazy, right? I remember them whistling at a few kilohertz (well within the audio range) not so many years ago. I wonder what's allowed the rapid frequency increase, maybe faster power MOSFETs?

    I saw some old (analogue, big-iron) power supplies recently, cased in a hefty steel box measuring maybe 14 in x 8 in x 8 in, and weighing maybe 15 - 20 kg (33 - 44 lbs). They were rated for 12V, 6A DC maximum output (72 watts). Today a laptop SMPS the size and weight of a small bar of bath soap puts out more power, and it's cleaner and better regulated, too. Amazing!

    -Gnobuddy

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    Senior Member Enzo's Avatar
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    Everything has gotten better, and advanced the art.
    Education is what you're left with after you have forgotten what you have learned.

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    Hard to believe this little chip will switch 1.5A at that frequency. It will also do split-rail supplies and much more. Here's how my (slightly clumsy) prototype worked out;

    img_20170909_102037580.jpg
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  10. #10
    "Thermionic Apocalypse" -JT nickb's Avatar
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    I feel kinda mean posting this after your hard work and you did a nice job too... but...

    You might want check these out. 150w! I used a few for battery powered portable amps. It could save you time and effort in the future. Crazy cheap.

    s-l500.jpg

    Need 350v 40W ?

    s-l1600.jpg



    Smaller & lower power?
    s-l500lp.jpg


    Mick Bailey likes this.
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    Thanks for the suggestion. The idea was to replace the 240v mains supply in a couple of pedals, so they need to be small. The smallest unit doesn't look like it would give 9v to 18v conversion at 500mA (actual draw 460mA). I'll order some of those high-current units as I can use them in another project. You have to laugh at how cheap these things are.

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    Quote Originally Posted by Mick Bailey View Post
    You have to laugh at how cheap these things are.
    The flip side being that traditional 60-Hz transformers are very rapidly headed for extinction, at least in the sizes where we might be interested in them. We already have to go to speciality sources to find transformers that work with valve-friendly power supply voltages and output impedances; what happens when E-I cores are in such small demand that they stop being manufactured?

    A bit closer to the topic of this thread: a lot of HP inkjet printers use a 32V DC power supply. Some of these power supplies have both +16V and +32V rails. Most of the smaller ones have the DC output isolated from the incoming (2-wire) AC mains. I find these HP inket power supplies quite frequently at local thrift stores, and they tend to be very cheap, because nobody wants them.

    Well, almost nobody. I've successfully used these as +/- 16V DC supplies to run op-amp based circuitry. They work well, with just a little extra RC filtering to remove low-level switching noise on the supply rails. They might be a good way to power guitar FX pedals too, either using the +16V rail, or you could custom-design your own pedals for either split +/- 16V rails, or a +32V rail.

    -Gnobuddy

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    I have quite a few players running their pedal boards off laptop power supplies. I run them into a distribution box and add extra linear regulators to give 12v and 9v outputs. The isolation from incoming mains and ground on some (though not all) laptop supplies means no ground loops. The big advantage is they can carry a spare at low cost and they're much more robust and better quality than most stompbox supplies. I always check though that the outputs aren't elevated to 80v above ground due to the internal EMI cap if one is fitted.

    A while back I dropped on a batch of new medical-grade supplies. Don't know what they were intended for but there was no noise at all on the output and inside they were built really well with the highest possible parts quality, construction and screening.

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    Quote Originally Posted by Mick Bailey View Post
    I have quite a few players running their pedal boards off laptop power supplies. I run them into a distribution box and add extra linear regulators to give 12v and 9v outputs. The isolation from incoming mains and ground on some (though not all) laptop supplies means no ground loops. The big advantage is they can carry a spare at low cost and they're much more robust and better quality than most stompbox supplies. I always check though that the outputs aren't elevated to 80v above ground due to the internal EMI cap if one is fitted.

    A while back I dropped on a batch of new medical-grade supplies. Don't know what they were intended for but there was no noise at all on the output and inside they were built really well with the highest possible parts quality, construction and screening.
    Medical grade is the best as you don't want any sparks should a patient be using oxygen.

    nosaj

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    Senior Member Enzo's Avatar
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    More than that, you don't want ANY leakage current on the unit that might interfere with a pacemaker or sensitive monitoring equipment connected to the patient. And of course maximum protection from the mains.
    Education is what you're left with after you have forgotten what you have learned.

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    Well, my boost converter didn't actually work out when installed in a pedal. I installed it in a TC Electronics stereo chorus/flanger as a testbed and it powered up just fine, but I though I had a fault with the compander or BBD device. The pedal was super-silent with nothing being played, but when I played anything there was a load of hash, clock noise and distortion that accompanied the notes. After lengthy experiments I disconnected the converter and used a regular 18v DC supply with no problem. When I reconnected the converter and scoped the pedal there was 500-odd khz all over the place, so this will be interfering with the BBD clock signal and causing all kinds of intermodulation. Even the leads from the converter have 12mV of RF on them.

    Damn.

    Anyhow, I'll see what some ferrite beads and a screening can will achieve.

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    Quote Originally Posted by Mick Bailey View Post
    Anyhow, I'll see what some ferrite beads and a screening can will achieve.
    Wrong wrong wrong. Solve the problem where it happens.

    1. The boost inductor should be EE, EI or toroid, unshielded drum is not recomended, but usually not the biggest source of problems.
    2. The boost diode must be hyperfast or schottky. Equally important is the small package and minimized leadout area. SMD (such as DO-214AA or DO-214AC) is best, upright mounted with huge lleadout loop is no-no.
    3. Input and output caps must not be small aluminium electrolytics. Tantalums, X7R, Y5V are acceptable, bigger low-ESR aluminium electrolytics might be acceptable.
    4. Short and simple ground path is required, preferable a plane.

    Screening cans and ferrite beads are helpful at dozens of MHz, your problems are at 100's of kHz.

    Disclaimer: not being dismissive, rather helpful
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  18. #18
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    The caps (low-ESR Panansonic intended for SMPS) and diode are as per application notes. Inductor is a standard drum. You can see my layout in post #9. By comparison I have a rather crude DIY boost converter built from discrete components that's in a strung-out layout and no noise.

    I re-read the documentation and it says "A core geometry like a rod or barrel is prone to generating high magnetic field radiation" then goes on to say "To reduce the noise generated by the inductor, insert a 1.0 uF ceramic capacitor between VCC and ground as close as possible to the chip. I don't have that capacitor but will see if that makes any difference.

  19. #19
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    Here's a follow-up;

    The original layout turned out to be fine. The suggested cap didn't make any difference, but I needed a 200pf cap between pin 1 and ground and this took away most of the noise. I then subbed in a toroidal inductor and this fixed the rest. I would redesign the layout anyhow now I know more about how these things operate. There are two grounds - one for the switching side and another 'clean' ground which should be used to tie the divider resistors. The application notes shows these tied together in the schematic, but the narrative suggests separating them.

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    Great job, these little animals are so unforgiving re components and layout, you never know what trick makes them behave.

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    Quote Originally Posted by Mick Bailey View Post
    The original layout turned out to be fine. The suggested cap didn't make any difference, but I needed a 200pf cap between pin 1 and ground and this took away most of the noise. I then subbed in a toroidal inductor and this fixed the rest. I would redesign the layout anyhow now I know more about how these things operate. There are two grounds - one for the switching side and another 'clean' ground which should be used to tie the divider resistors. The application notes shows these tied together in the schematic, but the narrative suggests separating them.
    The grounds should be separated but finally at some point they have to be connected.
    The datasheet of CS5173 explains the analog ground:
    "Analog ground. This pin provides a clean ground for the controller circuitry and should not be in the path of large currents. The output voltage sensing resistors should be connected to this ground pin. This pin is connected to the IC substrate."
    and provides guidelines for the layout:
    "Separate the low current signal grounds from the power grounds. Use single point grounding or ground plane construction for the best results"
    It means that that the power ground (high current) should be separated from the analog ground (low current) but finally they should be connected. I hope that you did it in this way. For the power ground it is suggested to use a ground plane, which suggests that better layout could be achieved with SMD version of the circuit.

    Mark

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    Thanks for the clarification - I haven't yet done an SMD layout. The grounding reminds me of automotive ignition circuits where there's a heavy ground current when switching the coil primary that can interfere with the microprocessor due to 'ground bounce' if not properly designed.

    I've seen the artwork for the development board so this should provide a reference layout.

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