5 ms·

> Between the resulting thermal management issues and reduced battery life, linear regulation is seldom worth the pain. I'd argue the exact opposite. The artic

• quacksilver 2y ago
  Linear regulation is also very good when you have situations where you want to avoid generating unwanted noise or stray RF. Cheap buck converters are very noisy and annoying if you are building an audio or radio related project, or have such things nearby.
  • f1shy 2y ago
    In my experience, not only noise in the RF sense, but also audible. I put together a little audio amplifier, and the sound of the DC/DC makes it unusable in quiet situations. The 12kHz (coming physically from the converter, amplifier off) really hurts the ears!
    • arghwhat 2y ago
      That’s magnetostriction, components under switching load (caps, inductors) need to be secured in place with an appropriate glue/putty. Using a higher switching frequency can also help, plenty to choose from.
      • schoen 2y ago
        Can that also help with the emanations security issue where an adversary might be able to extract usable data from the audio produced by the electronic components?
        • mschuster91 2y ago
          TEMPEST and other side-channel hardening is hard to do if you lack access to anechoic/RF isolated chambers, sensitive scopes/microphones and knowledge.
        • kragen 2y ago
          yes, but the audio usually doesn't travel as far as the rf; you'd almost have to be in a situation where the adversary can't put equipment near you but has managed to subvert a microphone
        • foldr 2y ago
          The usable data would just be "DC-DC converter is on/off". In theory, if the converter uses a variable frequency or duty cycle, you might be able to extract some information about that too. But that's not very interesting.
          • arghwhat 2y ago
            A DC-DC converter always uses a variable duty cycle to maintain the target output voltage (or for CC, current). Without it, the voltage would vary wildly depending on load. For something like an audio amplifier, obtaining precise power supply load would in turn give you a curve over amplifier load, which effectively gives you the speaker amplitude. Input caps and filtering will likely remove the high frequency components entirely, but you might be able to construct at least part of the played waveform.
            • foldr 2y ago
              All good points. I would say that it's a fairly outlandish scenario where you are (i) close enough to the device to listen to the caps whining but (ii) can't measure actual voltages within the circuit (which could be a lot more informative) and (iii) can't just listen to the audio output of the device directly.
    • jimmyswimmy 2y ago
      The other answer about magnetostriction is technically correct (the best kind) but Misses the actual cause, which is subharmonic oscillation. This occurs when you have not stabilized your control loop properly and is often the result of inadequate phase margin. A simple fix may be to allow the control bandwidth by increasing capacitance at the work amplifier output. But this may also make the response too slow. For most people designing DCDC converters, this is the most difficult part to understand and correctly tune. If you get the parts selection right and carefully lay out the circuit, this is the one that they can't get right. It takes some understanding of control theory or careful testing and tweaking. And it's what drives a lot of folk to the expensive and relatively inflexible power modules.
      • megous 2y ago
        Noise can also come from pulse-skipping mode of regulation, if you draw too little power from the DC-DC converter, and can go away under higher load.
        • userbinator 2y ago
          This is why common "coil whine" heard in PC components can disappear when power-saving modes are disabled.
  • Animats 2y ago
    > Cheap buck converters are very noisy and annoying... Yes. This is why the good ones have more parts. It's a totally fixable problem, and the parts cost to fix it isn't high, but it takes extra engineering effort.
    • shiroiushi 2y ago
      All true, but for a hobbyist it probably isn't worth it if their goal is to just build some little audio project.
    • atoav 2y ago
      You are right. Yet, if you asked me how to get less noise on your audio circuit the LDO is the easier answer that will cost you less time to implement and likely give you the superior result. Especially for beginners without a ton of measuring equipment and experience having potentially bursty high frequency components in series can be an interesting way to not get the thing they were planning done, but instead have to deal with an entire new set of problems whose existence they didn't even know about. Technically you are correct, but "just slap a LDO on it" is probably the better advice.
      • Animats 2y ago
        Agreed. I had to learn a lot to build one. I had an application so unusual (driving antique teletype machines from a laptop) that I had to do a unique design. For most low-volume applications, it's not worth the trouble.
• roaringraster 2y ago
  And 3.3/5 is approximately 66% efficiency, which isn't too horrible. So even if you get your buck converter working, getting those 95%+ efficiency numbers you see in datasheets out of the circuit is not trivial.
• _fizz_buzz_ 2y ago
  If you have 5V and have to step down to 3.3V using an LDO is a very reasonable choice (at 100mA you have about 170mW losses). However if you have e.g. 24V and need to step down to 3.3V, an LDO can get annoyingly hot (at 100mA you now have over 2W losses). But I agree, this is really a "it depends" situation.
  • klysm 2y ago
    Most LDOs straight up won’t tolerate those conditions without very careful thermal management
• deleted 2y ago
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• michaelt 2y ago
  > On the other hand, buck converters require you to actually do some actual engineering. You can't just haphazardly throw in a single IC and expect it to work flawlessly on your first try. It used to be a hassle a few years ago - but these days you can haphazardly throw in a R-78K3.3-0.5 - which has the pinout of a classic three-pin 3.3v linear regulator, but it's actually an 80% efficient DC-DC converter with 500mA output and an input range that goes up to 36v. That's enough current even if you've got something like an ESP32 that needs 250mA - and for any type of hobby project, the $2.40 is fine.