Category Archives: buck converter

Circuit VR: An (Almost) Practical Buck Converter

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In the last installment of Circuit VR, we walked around a simplified buck converter. The main simplification was using a constant PWM signal. The result is that the output voltage is a fixed fraction of the input voltage. For a regulator, the pulse width will need to depend on the output voltage so that any changes in the output are self-correcting. So this time, we’ll make a regulator, although we’ll still use a few Spice elements you’d have to replace in a practical design. In particular, we’ll assume you can generate a triangle wave, which is easy enough, and produce …read more

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Open Hardware Takes Charge in Papua New Guinea

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You probably don’t think much about charging your phone. Just find an outlet, plug it in, and wait a while. Can’t find a cable or wall wart? A rainbow of cheap, candy-colored options awaits you down at the brightly-lit corner drugstore.

This scenario couldn’t be further from reality in third world countries like Papua New Guinea, where people living in remote jungles have cell phone coverage, but have to charge their phones by hooking them up directly to cheap solar panels and old car batteries.

[Marius Taciuc] wants to change all of that. At the suggestion of his friend [Brian], …read more

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Circuit VR: Simple Buck Converters

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The first thing I ever built without a kit was a 5 V regulated power supply using the old LM390K. That’s a classic linear regulator like a 7805. While they are simple, they waste a lot of energy as heat, especially if the input voltage goes higher. While there are still applications where linear regulators make sense, they are increasingly being replaced by switching power supplies that are much more efficient. How do switchers work? Well, you buy a switching power supply IC, add an inductor and you are done. Class dismissed. Oh wait… while that might be the best …read more

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Buck Converter Efficiency

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We always appreciate when someone takes the time to build something and then demonstrates what different design choices impact using the real hardware. Sure, you can work out the math and do simulations, but there’s something about having real hardware that makes it tangible. [Julian Ilett] recently posted two videos that fit this description. He built a buck converter and made measurements about its efficiency using different configurations.

The test setup is simple. He monitors the drive PWM with a scope and has power meters on the input and output. That makes it easy to measure the efficiency since it …read more

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A DIY 5V-3V Switching Converter in the Space of a TO-220 Package

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We’re suckers for miniaturization projects. Stuff anything into a small enough package and you’ve probably got our attention. Make that something both tiny and useful, like this 5-volt to 3.3-volt converter in a TO-220 sized package, and that’s something to get excited about. It’s a switch mode power supply that takes the same space as a traditional linear regulator.

Granted, the heavy lifting in [Kevin Hubbard]’s diminutive buck converter is done by a PAM2305 DC-DC step-down converter chip which needs only a few supporting components. But the engineering [Kevin] put into this to squeeze everything onto a scrap of PCB …read more

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Building a Portable Solar Powered Spot Welder: Charging Supercapacitors

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Before Lunar New Year, I had ordered two 3000 F, 2.7 V supercapacitors from China for about $4 each. I don’t actually remember why, but they arrived (unexpectedly) just before the holiday.

Supercapacitors (often called ultracapacitors) fill a niche somewhere between rechargeable lithium cells and ordinary capacitors. Ordinary capacitors have a low energy density, but a high power density: they can store and release energy very quickly. Lithium cells store a lot of energy, but charge and discharge at a comparatively low rate. By weight, supercapacitors store on the order of ten times less energy than lithium cells, and can …read more

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The uA723 As A Switch Mode Regulator

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If you are an electronic engineer or received an education in electronics that went beyond the very basics, there is a good chance that you will be familiar with the Fairchild μA723. This chip designed by the legendary Bob Widlar and released in 1967 is a kit-of-parts for building all sorts of voltage regulators. Aside from being a very useful device, it may owe some of its long life to appearing as a teaching example in Paul Horowitz and Winfield Hill’s seminal text, The Art Of Electronics. It’s a favourite chip of mine, and I have written about it …read more

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Power Your Guitar Pedals With Drill Batteries

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Guitar pedals are a great way to experiment with the sound of your instrument. However, they require electricity, and when you’re using more than a couple, it can get messy. Some will run on batteries, while others are thirstier for more current and will only work with a plugback. There are a great many solutions out there, but most people with more than a few pedals to power will end up going to some kind of mains powered solution. [Don] is here to show us that it’s not the only way.

Mains power is great for some things, but where …read more

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Coin-Sized LED Control

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EE and firmware developer [Enrico] had played with LEDs as a kid, burning out his fair share of them by applying too much current. With the benefit of his firmware chops, he set about creating a board that drives LEDs properly.

[Enrico]’s project centers around a Texas Instruments LM3405 buck controller. It accepts input voltage from anywhere from 3V to 20V and outputs up to 20V/15W to one or more LEDs. He built a ton of safety features into it like short-circuit and open-circuit immunity, temperature control, and auto-off switching when idle. He also created a LED board to test …read more

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Are You Down With MPPT? (Yeah, You Know Me.)

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Solar cells have gotten cheaper and cheaper, and are becoming an economically viable source of renewable energy in many parts of the world. Capturing the optimal amount of energy from a solar panel is a tricky business, however. First there are a raft of physical prerequisites to operating efficiently: the panel needs to be kept clean so the sun can reach the cells, the panel needs to point at the sun, and it’s best if they’re kept from getting too hot.

Along with these physical demands, solar panels are electrically finicky as well. In particular, the amount of power they …read more

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