• Re: quad 1/2 bridge

    From Jan Panteltje@21:1/5 to JL@gct.com on Mon Sep 23 14:59:25 2024
    On a sunny day (Mon, 23 Sep 2024 07:15:43 -0700) it happened john larkin <JL@gct.com> wrote in <abt2fj53dcek89n4f9b67c9ca0a1nd8cgn@4ax.com>:


    https://www.digikey.com/en/products/detail/texas-instruments/DRV8962DDWR/18724317

    Four half-bridge switchers for about $5. Current and thermal limiting.
    I was about to dremel and test my own half-bridge driver, but won't
    now. I guess I'll have to shuffle up the abstraction stack.

    There must be something cool that these could be used for. A
    16-channel power supply?

    4 channel audio amp?

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  • From john larkin@21:1/5 to All on Mon Sep 23 07:15:43 2024
    https://www.digikey.com/en/products/detail/texas-instruments/DRV8962DDWR/18724317

    Four half-bridge switchers for about $5. Current and thermal limiting.
    I was about to dremel and test my own half-bridge driver, but won't
    now. I guess I'll have to shuffle up the abstraction stack.

    There must be something cool that these could be used for. A
    16-channel power supply?

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From john larkin@21:1/5 to All on Mon Sep 23 08:24:06 2024
    On Mon, 23 Sep 2024 14:59:25 GMT, Jan Panteltje <alien@comet.invalid>
    wrote:

    On a sunny day (Mon, 23 Sep 2024 07:15:43 -0700) it happened john larkin ><JL@gct.com> wrote in <abt2fj53dcek89n4f9b67c9ca0a1nd8cgn@4ax.com>:

    https://www.digikey.com/en/products/detail/texas-instruments/DRV8962DDWR/18724317

    Four half-bridge switchers for about $5. Current and thermal limiting.
    I was about to dremel and test my own half-bridge driver, but won't
    now. I guess I'll have to shuffle up the abstraction stack.

    There must be something cool that these could be used for. A
    16-channel power supply?

    4 channel audio amp?

    Half-bridge audio amps can be tricky. At that price, may as well go full-bridge. A half-bridge switcher can pump power uphill, back into
    the power supply.

    I wonder if we can get our little RP2040 cpu chip to do a multichannel closed-loop supply, and maybe generate spread-spectrum PWM on 8
    channels.

    Phil, the 8962 data sheet discusses driving TECs.

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  • From Phil Hobbs@21:1/5 to john larkin on Mon Sep 23 17:32:21 2024
    john larkin <JL@gct.com> wrote:

    https://www.digikey.com/en/products/detail/texas-instruments/DRV8962DDWR/18724317

    Four half-bridge switchers for about $5. Current and thermal limiting.
    I was about to dremel and test my own half-bridge driver, but won't
    now. I guess I'll have to shuffle up the abstraction stack.

    There must be something cool that these could be used for. A
    16-channel power supply?



    In that package, they’re probably intended for driving LED strings in displays, where board space is not a problem.

    Cheers

    Phil Hobbs

    --
    Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC / Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics

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  • From john larkin@21:1/5 to pcdhSpamMeSenseless@electrooptical. on Mon Sep 23 11:13:21 2024
    On Mon, 23 Sep 2024 17:32:21 -0000 (UTC), Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:

    john larkin <JL@gct.com> wrote:

    https://www.digikey.com/en/products/detail/texas-instruments/DRV8962DDWR/18724317

    Four half-bridge switchers for about $5. Current and thermal limiting.
    I was about to dremel and test my own half-bridge driver, but won't
    now. I guess I'll have to shuffle up the abstraction stack.

    There must be something cool that these could be used for. A
    16-channel power supply?



    In that package, they’re probably intended for driving LED strings in >displays, where board space is not a problem.

    Cheers

    Phil Hobbs

    It's a lot smaller than the four 1/2 bridges I was considering. Each
    had an SO8 driver chip, two dpak fets, and a bunch of discretes.

    I was about to Dremel this:

    https://www.dropbox.com/scl/fi/8g85gtxx4ic0vj91rircr/X100A.jpg?rlkey=9a2f2jcv91b68utemrnekonq9&raw=1

    That chip will need cooling somehow. I'll run the eval board and see
    how hot it gets.

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  • From Phil Hobbs@21:1/5 to john larkin on Mon Sep 23 18:24:19 2024
    john larkin <JL@gct.com> wrote:
    On Mon, 23 Sep 2024 14:59:25 GMT, Jan Panteltje <alien@comet.invalid>
    wrote:

    On a sunny day (Mon, 23 Sep 2024 07:15:43 -0700) it happened john larkin
    <JL@gct.com> wrote in <abt2fj53dcek89n4f9b67c9ca0a1nd8cgn@4ax.com>:


    https://www.digikey.com/en/products/detail/texas-instruments/DRV8962DDWR/18724317

    Four half-bridge switchers for about $5. Current and thermal limiting.
    I was about to dremel and test my own half-bridge driver, but won't
    now. I guess I'll have to shuffle up the abstraction stack.

    There must be something cool that these could be used for. A
    16-channel power supply?

    4 channel audio amp?

    Half-bridge audio amps can be tricky. At that price, may as well go full-bridge. A half-bridge switcher can pump power uphill, back into
    the power supply.

    I wonder if we can get our little RP2040 cpu chip to do a multichannel closed-loop supply, and maybe generate spread-spectrum PWM on 8
    channels.

    Phil, the 8962 data sheet discusses driving TECs.

    Thanks.

    I rarely have the luxury of using a barefoot switcher for TECs. The
    capacitance from the supply to the cold plate is tens of nanofarads, and
    anyway a small TEC runs way under 5V in normal use, so it usually needs a
    buck.

    We have a couple of nice canned designs that use variations on Class H,
    i.e. a fast buck switcher with a very low-Vsat linear stage that gets rid
    of the ripple.

    The switcher control is stupid simple. The MCU DAC is summed with the
    switcher feedback network. The MCU very slowly drops the output voltage
    until the analog loop rails, bumps it up by 200mV or so, then starts
    dropping it again. You wouldn’t do that with an audio amp, but it works great for thermal control.

    For cooling-only, we use a two-pole BJT current source (like a BJT gyrator
    but with two poles).

    For use near ambient, as with diode lasers, we use a slightly more
    complicated thing, an asymmetrical BJT bridge. One side is a complementary current conveyor (current in, current out) and the other is a regular voltage-output complementary class-B that keeps the load terminals moving symmetrically. (All that is to say that one side comes out the collectors
    and the other comes out the emitters.)

    This approach allows current sensing in all four legs, which turns out to
    be very handy—besides short circuit protection, it also lets you have different current limits in the heating and cooling directions.

    The other trick is choosing the polarity so the voltage-output side is
    sourcing current when cooling. The control amp runs off the higher rail, so
    the NPN’s V_CE can go way into saturation. This isn’t an issue on the current conveyor side.

    Both fit into under a square inch, including pours, and can drive the usual 2-3A TECs to their limits.

    Cheers

    Phil Hobbs
    --
    Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC / Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics

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