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The magic of DC-DC voltage conversion (2023)

crote
19 replies
12h41m

Between the resulting thermal management issues and reduced battery life, linear regulation is seldom worth the pain.

I'd argue the exact opposite. The article is targeting "enthusiasts", and a very large portion of enthusiast projects are going to be powered by a 5V USB charger and consume in the order of a few 100mA of power.

LDOs are dirt cheap, widely available, have pretty decent output characteristics, and incredibly easy to use. If you have basically unlimited 5V and want 100mA of 3.3V, why not use one?

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. You either have to use an (expensive!) fully-integrated module, or do a decent bit of math and part sourcing yourself. Neither option is exactly attractive to a hobbyist building a fairly simple one-off PCB.

quacksilver
15 replies
12h15m

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
11 replies
12h7m

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
8 replies
11h56m

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
7 replies
9h55m

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?

foldr
3 replies
8h59m

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
2 replies
5h29m

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
1 replies
5h1m

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.

arghwhat
0 replies
4h38m

Acoustic noise is one thing, but it's not at all outlandish to be within range of the EMI emitted from the same power supply which tells the same tale. What is outlandish is thinking anyone bothers listening in. :)

mschuster91
0 replies
9h47m

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
0 replies
9h29m

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

arghwhat
0 replies
7h3m

The noise would correlate with load, but this is the least of your worries.

Unless you have a proper RF testing lab and skilled EMC engineers at your disposal, the only thing you can do is stuff everything into a properly designed faraday cage.

jimmyswimmy
1 replies
6h34m

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
0 replies
3h19m

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.

Animats
2 replies
11h40m

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
0 replies
11h12m

All true, but for a hobbyist it probably isn't worth it if their goal is to just build some little audio project.

atoav
0 replies
11h4m

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.

roaringraster
0 replies
11h40m

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.

michaelt
0 replies
5h34m

> 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.

_fizz_buzz_
0 replies
9h0m

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.

Animats
15 replies
11h42m

DC-DC converters are hard, but fun. The basic concept is that when you put current through an inductor for a while, then disconnect it, you get a big voltage spike. That's a classic auto ignition system. You can put that spike through a diode and use it to charge a capacitor to get DC out. The neat thing about switching power supplies is that there's very little resistance in the power path. That's why the efficiencies are so good. The not-neat thing is that they are a dead short across the input for part of the cycle, which is why failures can cause fires and why you may need an inrush current limiter and/or a fuse.

There are boost converters, buck converters, and ones with transformers. With a transformer you can isolate the input from the output, which is mandatory for safety if you're driving the thing from the AC power line.

Here's one of mine. USB 5VDC in, 120 VDC out, to operate antique teletype machines that need 60mA 120VDC.[1] The basic circuit is simple, but there are multiple surface mount ferrite beads and small capacitors to keep the spikes from coming out via the input USB, output, or as RF. LTspice simulation was needed to pick the values for those, so as to minimize noise in both voltage and current.

[1] https://github.com/John-Nagle/ttyloopdriver/blob/master/boar...

petertodd
4 replies
8h25m

The basic concept is that when you put current through an inductor for a while, then disconnect it, you get a big voltage spike.

That's actually usually not true, as the vast majority of DC to DC converters are step-down converters: you do not want the voltage to spike. And in general, it isn't really a "spike".

A better way to think about what is happening is that passing a current from a power supply through an inductor transfers energy into the magnetic field. When you stop doing that, the magnetic field diminishes, transferring energy back into current. But this time, you direct the current into the circuit.

The trick is that by picking the timing and other parameters correctly, you can pick the voltage of the downstream current. Specifically, you can do this because the voltage across the inductor is a function of the slope of the strength of the magnetic field around the wire in the inductor. Pick a different slope, and you can pick a different voltage. Since you usually want a stable voltage, the graph of the magnetic field strength will be (roughly) a sawtooth, and the graph of the induced voltage will be (roughly) a square wave (I am simplifying here for understandability!). A sawtooth shape has a consistent current slope, which leads to a consistent voltage.

Terretta
3 replies
6h25m

DISCLAIMER: Described for entertainment value only. Some details omitted. Don't try this at home!

That energy transfer makes an “interesting” party trick.

Get the step up/down winding transformer from an old CRT TV. Get rid of other components*, and wire it with a 9 volt battery on one side, and connect the other with + to conducting surface on three sides of a box with - to the three opposing sides. Put a switch on the underside that opens the circuit.

To pick up a box generally requires touching two opposite sides. Opening the circuit dumps the field into the person picking it up who gets a momentary jolt.

It's enough to run through multiple people: hold hands in a ring of 2 - 10 people, and have two people at ends of the ring each press an opposite side of the box and pick it up, the whole ring gets the jolt!

As a grade school science experiment, have the experiment display say something along the lines of "Guess the weight" so people pick up the box and get a surprise.

For more about retro transformer circuits, see:

https://hackaday.com/2016/07/04/retrotechtacular-dc-to-dc-co...

This is sort of a single vibe (the switch opening) of a vibrator-transformer-rectifier transformer, to collapse the magnetic field that dumps into the still "closed" side through the person picking it up. No rectifier since it's not AC, it's just C. So the same principle, without the rest of the parts.

* WARNING: Don't look up the rest of the owl. Don't build this. Don't try this. Don't let anyone touch this.

PopAlongKid
1 replies
6h15m

Way, way back, when I was in fifth grade, my dad (who was part owner of a car repair shop) brought an ignition coil (the old kind, that was connected to a distributor for the spark plugs) into the classroom, and I guess a 12-volt car battery. All 25 of us students held hands in a large circle and got the jolt. this was part of the teacher's ongoing study of electricity, which also involved winding wire around a hollow cardboard cylinder to make a magnetizer/de-magnetizer tube.

Terretta
0 replies
5h44m

Yes! And same age when my dad taught me this.

(Wasn't it great learning in an age before cars had seatbelts, before push mowers had kill bars, and when nothing had warning labels?)

I was mostly tongue in cheek about the danger above, as the most dangerous step would be relieving a previously functional CRT of the transformer block. The CRT discharge can kill you.

Using an ignition coil should work (I didn't try it) and is likely safer to source if you're getting it from something assembled instead of from a used parts bin.

As for the rest of the owl, this is from memory, nearly half a century ago, so, yeah, disclaimers:

---

# How to Build a Prank Shock Box for a Science Exhibit

This fun project will surprise your friends with a harmless electric shock when they pick up a prank box to guess its weight. Here’s how you can build it and how it works.

## Materials:

- 9-volt battery

- Step-up transformer (designed to increase voltage)

\_ consider a flyback transformer from old CRT or auto ignition coil, talk to circuit electrician expert

- Switch (spring-loaded or pressure-based)

- Wires

- Small box (to hold the circuit)

- Electrical tape

- Conductive foil or metal strips for accessible sides of box

## How It Works:

This circuit uses a step-up transformer coil to generate a small electric shock when someone picks up the box. While transformers typically work with alternating current (AC), here you use direct current (DC) from the 9-volt battery. The trick happens when the circuit opens as the box is lifted, causing the transformer’s magnetic field to collapse and induce a voltage spike.

When the box is lifted, the switch opens, cutting off the current from the battery. This sudden interruption collapses the transformer’s magnetic field, generating a quick, harmless jolt.

## Steps to Build:

1. Assemble the Circuit:

- Connect the 9-volt battery to the primary side of the transformer, with a switch in between. The switch should stay closed when the box is at rest and open when it’s picked up.

- Wire the secondary side of the transformer to two sets of exposed contact points on the outside of the box: one set connected to the positive side and the other set to the negative side of the transformer.

2. Add Conductive Surfaces:

- To make it more effective, cover three sides or faces of the box with conductive material (like aluminum foil or metal strips) connected to the positive output of the transformer. Then cover the opposite three sides with conductive material connected to the negative output of the transformer.

- When someone picks up the box, their hands will naturally touch both a positive and negative side, allowing the shock to pass through them.

3. Install the Switch:

- Position the switch on the underside of the box so that it opens when the box is lifted. You can use a spring-loaded or pressure-based switch that triggers when the box is moved.

4. Test the Circuit:

- With the box resting, the current will flow through the transformer, building up a magnetic field. Once someone lifts the box, the circuit breaks, causing the field to collapse and induce the shock.

5. Secure the Box:

- Place and affix all the components securely inside the box, bringing your two wires through the sides and making sure the exposed contact points are positioned on opposite sides of the box. Tape down any loose wires.

## Science Explanation:

This project uses Faraday’s Law of Induction, which states that a changing magnetic field induces voltage. The transformer converts the collapsing magnetic field into a brief, high-voltage spike, delivering a small shock to whatever is completing the high side circuit when the low side circuit is opened. Although transformers usually work with AC, you’re using the moment when the DC current stops to mimic that effect.

https://en.wikipedia.org/wiki/Faraday%27s_law_of_induction

The conductive material on the box ensures that when someone lifts the box, their hands make contact with both the positive and negative sides, completing the circuit for the jolt.

## Safety Note:

When done correctly, this project delivers a tiny, harmless jolt, similar to static electricity. Always use low power, an appropriate transformer, and avoid using higher voltages or currents. Consult with a TV repair expert or similar on your design before starting. DO NOT TOUCH ASSEMBLED CRTs. Let the TV repair person do it. She'll have parts anyway.

sfilmeyer
0 replies
3h32m

I initially misread this as you proposing using a car battery rather than a 9 volt battery, which sounds like a much less fun party trick.

rkagerer
3 replies
10h55m

Can't you also charge up capacitors then slam them together in series? Is there a name for that kind of supply?

caf
1 replies
10h42m

Yes, it's called a charge pump.

There's one specific sub-type called a Cockroft-Walton voltage amplifier.

hakonjdjohnsen
0 replies
10h40m

This is known as a charge pump, and is the third concept described in the linked article. The article only mention one flying capacitor, but you can use more than one and connect them in series to get a higher multiple of the input voltage.

Ben Eater also did a nice introduction to charge pumps by building a simple one on a breadboard: https://www.youtube.com/watch?v=4alV5LzHLE4&t=704s

amelius
2 replies
8h36m

I see you made a current limiter from a mosfet + resistor. I wonder if there are ready-made components that do the same, and also monitor overheating. Maybe not necessary in this case (because you're only limiting the inrush current, not a continuous current). There are current-limiting diodes but as far as I've seen they are only available for smaller currents.

michaelt
1 replies
8h16m

You can get single-chip current limiters for LED driver applications. A CL2N8-G for example.

In some applications you can also use almost any linear voltage regulator - put a resistor between your linear regulator's ground and output pins, and you'll get a constant current.

Of course if your application involves the amount of power dissipation that requires a heatsink, you'll probably end up with a discrete component for that anyway :)

amelius
0 replies
6h24m

Let's say I have a voltage source of 48V, and I want to limit current in my system to 4.5A, precisely, and with overheating protection. I could be wrong but I don't think the led-driver and voltage regulator solutions would fall in this range. Also, a heatsink would not be required if the duration in which the current needs limiting is small.

retrac
0 replies
2h57m

I think of it as synthesizing a sine wave (AC power) with DC pulses, using an inductor or capacitor for smoothing. The result is then rectified back to DC.

mindslight
0 replies
3h45m

DC-DC converters are not a "dead short across the input for part of the cycle" in normal operation - rather the voltage is across the inductor. If the switch stays on too long and the inductor reaches its saturation current, or one of the many other (cascading) failure modes, then can you end up with effectively a short across the input. This can happen to many kinds of electronics (eg a simple tantalum decoupling cap, or an IC's SCR latchup), but designing the power topology is a good place to think about these failure modes.

(Although going 5V->120V with USB as the power source, I can understand how "dead short" was a decent intuition)

kosma
0 replies
6h16m

That voltage spike only applies to flyback converter. Your typical buck/boost converter doesn't do that - the current waveform is a sawtooth, and voltage ripple is designed to be in the mV range.

hcfman
10 replies
12h3m

I've been working with audio recently and found so many of the devices that convert 3.7V to 5V for example inject noise into the rail that make's it in the microphone input source.

The battery support from pisource does this terribly. But so do many battery sources. It's not just microphones that get affected, but also other sensitive sensors like accelerometers.

I hope that other people making DC-DC convertors put some effort into making sure the supply is so clean so as to prevent this in future.

euroderf
8 replies
11h49m

Isn't this like 95% fixable with a capacitor ? Aren't there cables with small embedded caps ?

dragontamer
6 replies
11h37m

Oh hell no.

I think a lot of people are overly cautious of DC-DC conversion in this topic, but you've gone full-tilt in the opposite direction and are severely underestimating the problems that occur.

1. Its not "power-conversion" that's hard per se, its EMC that's very hard and not taught very well at a bachelor's level.

2. DC-DC Voltage Converters usually handle the entirety of your board's power, meaning they are the highest power component.

3. High power and high-frequency is a difficult EMC problem. This means that a bad design will absolutely send your electrons / energy out and radiate out like an antenna. And if things on the same board pick it up, it will be called crosstalk. And if things off-board pick it up, its called electromagnetic interference which almost certainly leads to a compliance problem.

---------------

1. Hobbyists don't care about compliance. So bam. We are already dealing with the biggest problem by simply not caring about it. (Maybe you can care and go into deeper studies, but... if you're a beginner just don't care. Learn this very difficult stuff later).

2. Prevent crosstalk by following good board design rules: have a 4-layer board. Use Power+Signal / GND / GND / Power+Signal stackup. Use two vias (one for signal-1 to signal-4 traversals), and a 2nd via for GND2 to GND3 traversal of the return current). Thinking of both the forward current and a tightly bound reverse current is basically all you need to do to avoid difficult crosstalk problems on board.

Done.

Point#2 requires deeper studies than is typical in bachelor's level electrical engineering. But it truly isn't very difficult once you learn the theory. Tight ground-planes reduce crosstalk (and EMI problems), and furthermore thinking of the return-current explicitly prevents problems.

Now you could have some truly difficult "ringing" from trace inductance and other such nasty problems... but that tends to occur beyond 100MHz. I'm thinking most beginners are going to be under 20MHz for most of their designs and thus never deal with those advanced "PDN" / Power Delivery Network problems.

Though if you do go into PDNs, its obviously a tough subject with huge amounts of study and reading involved. But most of the problems truly are at very high frequencies and/or at EMI compliance. Beginner Hobbyists avoid the most difficult issues entirely by nature of beginner (aka: low-speed) and hobbyist (and therefore don't have to follow regulators).

----------

I'm not a professional. But my understanding is that top-level EEs who work on PDNs will simulate the circuit-board itself to figure out trace inductances / capacitances in the board itself. (Closer planes of ground/power will create more capacitance. Long traces tend to increase trace inductance, etc. etc.). And tight simulations are the only way to truly understand the PCB and how it interacts at high frequencies with high-power.

But such methodologies are gross overkill for a 1MHz boost converter with a pre-made PCB Layout, and a list of capacitors + inductors already picked out for you. (ex: https://www.microchip.com/en-us/product/mcp1640)

Seriously: Page 17 (https://ww1.microchip.com/downloads/aemDocuments/documents/A...) already gives you the PCB-layout you need for this, with recommended components. Don't overthink it, just copy the design from the document.

Youden
3 replies
6h28m

Use Power+Signal / GND / GND / Power+Signal stackup.

I'm just a novice (maybe intermediate) so I'm wondering: the common 4-layer stackups available to hobbyists seem to be 1oz/0.5oz/0.5oz/1oz and I assume the outer layers have better thermal dissipation since they're only kept from the air by solder mask; so wouldn't it be better to put power/ground on the outer layers and keep signals in the middle?

Also maybe I'm weird and this is pointless but I typically put a filled copper zone tied to ground on every single layer, unless I have a reason to put some other kind of zone in a particular area. Is it necessary to have a full, dedicated ground plane, rather than ground + signal or ground + power?

aaronmdjones
1 replies
5h0m

so wouldn't it be better to put power/ground on the outer layers and keep signals in the middle?

Signals must never cross a break or split in the plane they're referencing (usually 0V or ""ground""). This creates huge EMI problems. Your proposal would have signals on layer 2 crossing a split in the ground plane on layer 1 (that split caused by power traces).

Some interesting material on the subject:

https://www.youtube.com/watch?v=ZYUYOXmo9UU

https://www.youtube.com/watch?v=QG0Apol-oj0

https://www.youtube.com/watch?v=ySuUZEjARPY

https://www.youtube.com/watch?v=0RyBCnowLsI

dragontamer
0 replies
5h4m

Ground fill is counterproductive on the signal layer.

If you accidentally get the return path on layer1 or layer4 instead of the designated layer2 or layer3, you've created noise.

Power+Signal / GND / GND / Power+Signal is about consistency and braindead-easy tracking of return paths. The return path for layer1 is always layer2. The return path of layer4 is always layer3.

Keeping track of both the forward signal (or power line) and the reversed return current (which was electrically induced onto the nearest reference plane) stops working if suddenly you have random reference ground-fill planes on the layer1 or layer4.

DO NOT put GND on layer1 or layer4 if you're doing this methodology.

---------------

Beginners likely aren't working with a hot enough circuit where thermal dissipation is an issue. If you do have thermal dissipation then I guess thermal ground on layer1 and layer4 ties with thermal vias will be needed.

In practice, the thermal resistance across the PCB cross section is better than beginners expect anyway. Thermal conductivity is just one attribute, the other attributes of heat movement are distance and cross sectional area.

So the shape favors you up and down the PCB. Yes the fiberglass has worse thermal conductivity but you win on shape.

Max-q
1 replies
10h37m

We have a couple of challenges today. Hobbyists often go over 20MHz, because they put WiFi, BT or USB on their boards, giving EMC issues. Also, the speed of the modern ICs tend to be very high. If you have a 9600 Hz UART signal, that is not a 9600 Hz signal if it's a square wave with a modern IC with very short rise time on the pins. So a good old, slow serial line can with modern MCU emit noise up in the hundreds of MHz range.

So your PCB layout tips are important, even on slow circuits these days.

dragontamer
0 replies
4h59m

Unless a beginner plans to sell a design on the public, there is no EMC (compliance) issue.

Maybe EMI crosstalk. But WIFI and BT are supposed to eminate out like a radio and jump across boards. That's the point.

---------

USB is a matched impedance differential pair. Are beginners really running high speed USB differential pairs down their circuits today?

Because that's a really.... Erm.... strange.... definition of a beginner. IMO anyway.

magicalhippo
0 replies
9h31m

As the sibling comment mentions there are several aspects.

You'll need proper input filtering which may require a non-trivial filter network. You'll also need proper output filtering, which does include slapping a lot of capacitors on there, but also careful selection of those capacitors both type and size. Parasitic inductance of larger packages can mean they can't filter high frequencies, and MLCC capacitors have a DC bias which means the effective capacitance is significantly reduced when they have a DC bias on them which they will have in a DC-DC converter.

Then you need to take great care about component placement and board layout, to minimize the return path of the currents and such.

You can skip all of that and get a board that functions as a DC-DC converter if you measure it with a multimeter, but actually be horrible. And you just can't fix bad layout by slapping more capacitors on there. And even with a not terrible layout, you can't fix it by using the wrong kind of capacitors. Like anything through-hole is just not gonna pass.

klysm
0 replies
5h55m

Making a noise-free DC-DC converter is very difficult. Any buck/boost style converter is going to introduce ripple and switching noise into the system. This is inherently unavoidable, and it’s very sensitive to the layout of the board. Actively or passively filtering out all this broadband frequency content is far from trivial, and there is no general solution - only a large, high dimensional tradeoff space.

You’re right that noise is a concern for any analog circuitry though, and if you want to, you can spend a lot of money on specialized DC/DC converter modules with integrated inductors that do their best to eliminate this noise.

progbits
7 replies
12h19m

I can highly recommend the MIT 6.622 Power Electronics course recently released on OCW:

https://youtube.com/playlist?list=PLUl4u3cNGP62UTc77mJoubhDE...

https://ocw.mit.edu/courses/6-622-power-electronics-spring-2...

Prof. David Perreault is excellent. While the course gets into pretty advanced topics that simply won't matter unless you are designing multi-kW systems, it covers all the fundamentals and builds understanding from ground up so you will know what makes sense to use and when.

kleiba
3 replies
11h38m

Thank you!

I was just going to ask about recommended resources for getting into electronics. I've never been able to find anything that I personally found useful - often times, introductury courses are too basic and slow to keep me focused, or they lack exercises or are too theoretical, etc.

There are many hobbyists who have learned all that stuff and can design and implement their own circuits (say, audiophiles or model train enthusiasts), so obviously they have all been able to get there. But I have never managed to learn anything about electronics, although I would really like to.

progbits
1 replies
11h9m

Yeah it can be hard. As a self-taught hobbyist I've found a mix of university courses (not whole curriculum, just pick and choose and don't feel bad fast-forwarding over some of the math theory), books (art of electronics, practical electronics for inventors), and high quality youtube channels (eevblog, phil's lab, robert feranec, microtype engineering) to be a good way to learn.

Also eevblog forums are great. I don't post much but just reading through the discussions you get a lot.

My greatest annoyance is the flood of very low quality Arduino tutorials everywhere that polute the search results. Not to be ungrateful, Arduino got me into the hobby, but if you just learned about resistors last week the world doesn't need your blogpost on how to connect it to a breadboard.

Max-q
0 replies
10h47m

You probably know about this already, buy in case you missed it: The Arts of Electronics is a wonderful book on electronics, starting from zero, ending up at bachelor level EE.

I was introduced to the second edition (silver) when I attended college in the late 90s, and have later upgraded to the third edition (gold). It also has a companion book with more exercises and lab experiments.

For everyone that wants to learn EE, it is highly recommend. Just beware: there are fake copies for sale on Amazon, so be sure you get a genuine copy.

tzs
0 replies
3h14m

The MITx version of MIT's 6.002, "Circuits and Electronics", is excellent. Its on MIT's OpenCourseWare [1], and on EdX where a session is starting today [2]. The EdX is divided into three parts, and that is part 1. Here are parts 2 [3] and 3 [4].

Caveat: when I took it at EdX the textbook was available online for free during the course, and it is an excellent textbook that I found very useful. That was back when all the MOOC platforms weren't too worried about monetization.

Now the textbook is only free online for people enrolled in the "verified certificate track" of the course, which is $189. The book is $64.97 for the paperback or DRM-free PDF [5]. I'm not sure how well the course works without the book.

[1] https://ocw.mit.edu/courses/6-002-circuits-and-electronics-s...

[2] https://www.edx.org/learn/circuits/massachusetts-institute-o...

[3] https://www.edx.org/learn/circuits/massachusetts-institute-o...

[4] https://www.edx.org/learn/electronics/massachusetts-institut...

[5] https://shop.elsevier.com/books/foundations-of-analog-and-di...

tecleandor
1 replies
6h57m

What's the starting level? My electronics knowledge is very basic and I'd like to start "designing" some simple power circuits.

I know the basics of resistors, diodes, capacitors, transistors... And I could explain the most simple classic power supply: transformer, full wave rectification, capacitors and so on. I've built basic digital circuits (LDO + arduino/ESP + leds and stuff) and know some basic physics. I'm good soldering, though :D

EricE
0 replies
1h12m

Checkout bigclivedotcom on youtube - he reverse engineers circuits all the time in entertaining and accessible ways; a great way to learn through practical applications.

nraynaud
0 replies
6h35m

funny, it got recently suggested to me too. I really feel like youtube is not individualizing the recommendations.

3dGrabber
7 replies
11h20m

There exists an interesting connection between Boost Converters and Hydraulic Rams [1]. A Hydraulic Ram is device that can pump water from a stream to a higher location by harnessing the kinetic energy of the stream, no other power source required.

The equations for the two devices are essentially the same, only the units change.

1 https://en.wikipedia.org/wiki/Hydraulic_ram

agumonkey
5 replies
8h46m

I love analogies between fields like this.

nraynaud
2 replies
6h38m

There is a whole area of multi-domain simulation, where the simulator seamlessly jumps from one form of energy to another as long as the units match. I have always loved that.

agumonkey
0 replies
4h21m

oh nice

SoftTalker
1 replies
3h16m

Water flows in pipes, valves, etc. concepts transfer to a lot of basic electrical circuits and concepts. E.g. voltage is analogous to pressure. Current is analogous to the volume of water flowing. Bigger pipe (wire) can carry more current. Valves are like switches or resistors. It works to de-mystify concepts for kids who have no concept of what electricity is but can think about water flowing in a pipe.

agumonkey
0 replies
1h35m

The base analogy working is cool but that other mechanisms on top also work similarly is what amazes me.

wrycoder
0 replies
11m

Current is analogous to momentum, because electron drift has net momentum.

moffkalast
5 replies
9h20m

96% efficiency sounds great on paper for synchronous converters, but as SBC current draw just keeps increasing and BLDC motors can run at higher voltages it starts to create a major heating problem when you have to supply both from the same source.

Something like 12V down to 5V at 5A creates a managable amount of heat, but going higher, 20V, 30V on the battery side and things start to melt all around from heat losses from that large a drop. In some cases I've had to resort to using cascaded rails, stepping first down to 24, then 24 to 12 and then 12 to 5 just to keep the heating spread between different buck converters even if it multiplies losses. Would love to hear what the expert solution is to this that isn't just a massive heatsink.

posterboy
1 replies
7h0m

you forgot to mention it should fit under a thumbnail, probably

moffkalast
0 replies
39m

It would be a nice plus :P

Honestly the size isn't such a big deal, as long as it doesn't weigh as much as two African elephants like the average mains PSU of this amperage.

moffkalast
0 replies
40m

current range 0 ~ 6.5A

Fuse recommended (5A)

I see they are very confident about going to 6A. These ratings are often just "yeah it can technically do that but it will reach 100 degrees during it", for any kind of stable continuous draw you just have to halve the rating to be safe.

mschuster91
0 replies
8h28m

Would love to hear what the expert solution is to this that isn't just a massive heatsink.

A smaller heatsink with active cooling and parallel MOSFETs. At a certain power level, it's just physically impossible to rely on convection cooling alone - just look at audio amps or your average CPU/GPU... banks of MOSFETs, caps and inductors it is. While the BOM part count may be higher, you need lower-capability parts.

The danger is, you need to carefully grade and match the MOSFETs, otherwise you risk them failing sequentially in a very short time if you're operating too close to their rated current - one burns out, the load distributes to the others, and then they fail because they cannot handle the additional load (or one fails into dead short instead of open, which instantly kills all of the others).

mglz
4 replies
8h56m

For beginners it is super annoying that many tutorials say "there is a magical switch or oscillator here which is integral to the function of the boost converter, but we will not tell you how to actually realize it". Additionally, that needs to work at the voltage level you are starting out from and in many cases should be galvanically isolated from the converter. This is a lot to keep in mind and it is actually not trivial.

The answer here is usually to find an IC that works at your desired input voltage or to have a linear regulator provide a small amount of power for the PWM generator. Also be wary of just running with an AI generated answer. Claude 3.5 Sonnet suggest you connect an Arduino straight to 230V and after some back and forth generates circuits which contain strange elements like "antiparallel diodes" which makes no sense.

posterboy
1 replies
7h37m

sounds like a spherical cow on a frictionless plane.

mglz
0 replies
4h50m

It is a very hairy cow, which likes to bite and is stuck in the mud. Also it has a wierd high-frequency response. There is a description of tractors to get it out, but we'll skip how the controls work for now.

awjlogan
1 replies
7h4m

The TI Power Designer[0] is a great resource. Obviously it will only show you TI parts, but it's very helpful to get a base design. You can filter by complexity (roughly BoM count), size, cost etc based on the parameters (input voltage range, output voltage range, power etc). The designs usually have a reference layout as well.

0: https://webench.ti.com/power-designer/

mglz
0 replies
4h50m

Very convenient, thank you!

kbouck
3 replies
6h52m

I want to power my 12V devices with USB PD. Looks like 12V is optional in the spec and is supported only by some devices (eg. UGREEN), and not by others (eg. Anker)

Given a USB PD power supply which supports 15V but not 12V, and a usb-c/barrel-jack cable configured to negotiate for 15V, what would be the simplest (yet safe) circuit i could add via barrel jack to regulate the to voltage down to safe/consistent 12V?

is a simple linear voltage regulator (LM7812) sufficient? would i need capacitors to smooth it out?

klysm
0 replies
6h0m

A 3V drop over an LDO is usually reasonable with low enough currents. Some LDOs require capacitors to be stable, and it’s usually a good idea to have some capacitance on your power rails anyway.

_Microft
0 replies
4h46m

It might be cheaper to get a power supply that supports later PD standards? E.g. IKEA is selling some cheap here for either 8€ (Sjöss, 1 USB-C port (max. 30W, up to 3A)) or 15€ (Sjöss, 2 USB-C port (combined power output of 45W, up to 3A, also on a single port)). Both support PD 3.0 and PPS (that's the fanciest PD standard that implements requesting arbitrary voltages from the power supply) They also stock nice and cheap USB-C cables. These power supplies work fine with USB-PD trigger boards set to 12V.

15155
0 replies
5h26m

The one important thing missing from your query here is:

How much current do you need?

If you need, say, >100A, the possible architecture looks very different than ~1A or less.

minkles
2 replies
5h37m

Lots of things in here which kill me a little:

1. You don't get a voltage spike when you disconnect an inductor. The field collapses and induces a current. If you measure it across a high impedance then it looks like a voltage spike. If you measure it across a low impedance then it's not necessarily much of a spike. Ergo depends on load impedance.

2. SMPS designs are not necessarily noisier than linear power supplies. It's always a design trade off. In fact you see SMPS in all modern RF test gear which is generally far more sensitive and has far more bandwidth than anything back when linear supplies were common. Also there is a lot of noise coming off the diodes in a basic bridge rectifier as well! Noise is a whole-system design consideration that has to be made.

3. Don't use any LLMs for designing circuits. Please go read a book on it designed by experts, not stuff scraped from thousands of idiots. I've seen some horrible stuff out there.

4. I'm sure I'll come up with more over time.

hwillis
0 replies
5h26m

If you measure it across a high impedance then it looks like a voltage spike. If you measure it across a low impedance then it's not necessarily much of a spike.

"Disconnect" implies an open circuit and high impedance.

Workaccount2
0 replies
3h40m

This is really nit-picky.

The fundamental action of a boost converter is from the inductors "voltage spike" behavior. The lowest noise linear regulator is less noisy than the lowest noise smps.

I agree though that LLM's are not good at circuit design.

londons_explore
2 replies
7h6m

I have often wondered if ideas from a buck/boost converter could be applied to a mechanical gearbox. Voltage and current in electrical circuits (where voltage x current = power) is completely analogous to torque and speed in mechanical shafts (where torque * speed = power). Every electrical component has a physical counterpart. Spring = capacitor. Inductor = mass with momentum. Resistor = friction brake.

The goal would be a variable ratio gearbox using a fully mechanical system, using a spring and a hammer type mechanism to convert one torque/speed to another torque/speed.

This is already done in impact wrenches, but I would hope that rather than having an impact rate of say 5 Hz, you have an impact rate of 50 kHz or more, allowing a smooth conversion from one speed to another.

Obviously, the difficulty is in the details - designing parts to withstand 50k hammers per second for years of operating without failing from fatigue.

Various other mechanical things already operate at high mechanical frequencies. SAW filters vibrate things mechanically at Ghz and don't suffer fatigue failures.

hwillis
1 replies
5h13m

You're overcomplicating it; you only need a single clutch and in/out springs[1] to do this. If you're spinning at 4000 rpm and your springs cover 6 degrees of rotation, then your clutch needs to be able to actuate at 4000 Hz.

When the clutch is engaged, the engine-side springs compress to supply the torque and match the speed difference. When it's disengaged, the springs expand back out as it returns to engine speed. The obvious problem is that clutches do not smoothly click on and off like a transistor.

However there are more specialized devices that use stick-slip dynamics like piezo actuators. Since there is a much more rapid transition between "on"/"off", they can be very efficient and allow relatively weak devices to exert very large forces. They're just only able to take very small steps.

[1] Labeled 4 here: https://haynes.com/en-gb/sites/default/files/styles/blog_lan...

londons_explore
0 replies
7m

When it's disengaged, the springs expand back out as it returns to engine speed.

What is it?

I think you need an intermediate flywheel, with springs and clutches on each side. The intermediate flywheel's mass is tiny, so might be formed by just the masses of the springs and clutch mechanism.

ziofill
0 replies
9h15m

I'm a theoretical physicist and I swear electrical stuff is so hard to understand! I have a lot of respect for electrical engineers ^^' (and electricians)

stonethrowaway
0 replies
2h2m

Friendly warning to people who aren’t electronics savvy: this blog post is written in a “now draw the owl” sort of way. I’m not sure who the audience is. Anyone who can read this stuff at the level presented inherently knows most of this and then some. Everyone else will need a book and that book will cover this material as it’s fairly fundamental and will derive equations used in here as well so you can make sense of it.

shellback3
0 replies
3h10m

Interesting, but I had expected to see a comparison of generating DC voltages using tubes, which were used in my university Electronics course, with solid state. In those days to generate a DC voltage from another DC voltage required generating an AC voltage from the DC and then rectifying it.

mikewarot
0 replies
9h53m

I've learned that the magic search word for 150ish volt boost converters is "Nixie".

My friend needed that voltage for a Geiger counter B+ battery replacement.

marcodiego
0 replies
4h39m

A commonly used alternative in the microcontroller world is to simply stack a few diodes. Very simple alternative which I have seen being used a few times.

exar0815
0 replies
11h47m

I do work in automotive EMC testing and it's nearly always the voltage conversion at fault when you fail tests or influence other devices.

Buck-Boost converters are a noisy and finicky thing, and not easy to debug if you use a monolithic IC from the cheapest vendor. Quite annoying discussions.

cushychicken
0 replies
5h38m

A decent article, but there’s a ton of misunderstanding in the comment section.

For one thing: LDOs can be more efficient than buck converters, especially at very low current consumptions. If you’re drawing sub 1 mA, like a battery powered system, an LDO is going to be a more efficient step down converter, because it doesn’t have switching losses. Bucks are only better choices for stepping down voltage at higher currents because the switching losses become negligible.

Second: a ton of people here are vastly exaggerating the difficulty of designing a step down buck converter. Integrated designs from TI or analog devices will tell you all the compensating components, output capacitor values, inductor values, etc. for common step down output voltages. Most will include reference layouts with a four layer six layer or even two layer stack up for optimal performance. It’s really not that hard to get a one spin win out of most common buck designs.

Don’t be afraid. Just follow the manual. You’ll be fine.