What ICs to order for beginner SMPS building? - Page 1
Forum section: electronics / beginners

author: hydrogen18
author_rank: Contributor
timestamp: October 10, 2017, 09:40:20 pm
content: This year I have finally had the opportunity to work on some electronics project. I haven't really had time to do this since I was a teenager. I bought a two channel oscilloscope, got some DC power supplies for my bench and got some decent multimeters. I also managed to build PCBs from single clad boards using my own designs from Fritzing.I've built a few different fun circuits for SMPS using 555s and TL494s. Neither of these are particularly desirable it seems. The 555 obviously has no feedback and the TL494 has a pecuilar issue with dead time. Although it has good feedback provisions for CC/CV designs, the dead time minimum is problematic. It has variable dead time but the minimum winds up being some large value. This leads to lots of oscillation when the circuit is off. For example, in this project:https://electronics.stackexchange.com/questions/282276/eliminating-mosfet-drain-voltage-spikes-in-a-push-pull-power-supplyI have tons of common components like capacitors, resistors, transistors, and MOSFETs. So what ICs should I order for SMPS control? I also need to purchase some MOSFET gate drivers since lots of controllers can't drive a gate high/low directly. It'd be preferable if I could buy ICs that can do flyback type designs or push-pull. It sort of dawned on me that experimenting with flyback designs is a cheaper way to learn. DIP packaging is preferred, but I can work with SMD components if need be.

author: mrpackethead
author_rank: Super Contributor
timestamp: October 10, 2017, 09:56:31 pm
content: Have a play with somethign like Texas Instruments Web Bench.. it will help you design some circuits, and select IC's.

author: Benta
author_rank: Super Contributor
timestamp: October 10, 2017, 09:59:35 pm
content: Majority opinion on this forum is: 555, it will solve everything.But seriously: there is no "one size fits all". Define your application and topology, then use the "sample" function at the major suppliers.For straight buck converters, the "Simple Switchers" from TI cover most needs.

author: bd139
author_rank: Super Contributor
timestamp: October 10, 2017, 10:09:23 pm
content: MC34063, while shunned by a lot of people, is a reasonable little IC. Available for 20x quantities from China for $1https://www.onsemi.com/pub/Collateral/AN920-D.PDFIt's functional but not particularly pretty and supports a number of topologies.You can use CC/CV for these easily. I have built a few LED drivers with them and negative rail inverters etc.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: October 10, 2017, 10:54:09 pm
content: Ideas:https://imgur.com/gallery/SoYtht4Tim

author: bd139
author_rank: Super Contributor
timestamp: October 11, 2017, 07:15:30 am
content: Sure they’re noisy and they occasionally explode but that’s part of the funAt $0.05 though you gotta seriously weigh that up vs an LT1073 for example in non critical applications.

author: mrpackethead
author_rank: Super Contributor
timestamp: October 11, 2017, 08:46:05 am
content: Quote from: bd139 on October 10, 2017, 10:09:23 pmThats 20 for $1. Cheap. and actually can ge thtem as little as 0.025 if you look hard and are happy or a no name version.

author: bd139
author_rank: Super Contributor
timestamp: October 11, 2017, 09:54:19 am
content: T3sl4co1l is perfectly correct on all points other than two.Firstly, cost. The only real cost is actually China Post when you need to get your shitty large inductors shipped. They're quite heavy. And your external switch if you want some serious power output. Really though you can build the entire supply for $0.15 easily. I doubt you can find a single IC that fits in that at volume cost.Secondly, stability and ease of use. The 34063 is unconditionally stable. It is pretty difficult to get it to not work with the crappiest board layout, the crappiest caps and the crappiest source impedance. Some of the nicer ICs are terribly tetchy with certain loads. As an example, try driving a load on the end of 6 feet of wire with an LT1073. It WILL oscillate unless you stick a quite frankly very expensive tant on the output. 34063? Meh just works with a shitty $0.01 electrolytic.

author: james_s
author_rank: Super Contributor
timestamp: October 20, 2017, 11:40:12 pm
content: What exactly is your goal? What kind of SMPS?I've used the TL434 and a clone from another manufacture, they're older ICs but for a while were ubiquitous in computer power supplies. They're well established parts that do what they're supposed to do.