Help with DC Audio Op Amp Power Supply - Page 1
Forum section: electronics / beginners

author: lilJohn
author_rank: Contributor
timestamp: October 18, 2020, 02:37:04 am
content: Hey All,Just a novice electronics hobbyist first-time posting here. I have 4 questions regarding building a power supply for some audio projects I want to do without having to deal with virtual grounding by voltage splitting. I found this adjustable "positive & negative DC-DC boost-buck converter", ~10 W Positive-Negative Dual-Rail Output Board, on eBay1where I have identified the IC as an XL60192. Note I managed to find the power rating in another listing of the same item.My questions are:1) Given that the board1(Figure 1) clearly has 3 discrete inductors, how does said breakout board implement the differential mode inductor specified by the manufacturer (Figure 2) if at all? I am probably going to go for one of these if no one can figure a schematic of the board (just that I have to wait for a bit more than a month where as if I made a PCB I could play with it within a week or two).2) Anyone that already has this board know the specifications for L1A, L1B, and L1C on the board (Figure 3)? Given that the manufacturer has specified 47 µH/5 A inductors for their previous applications2I am inclined to assume the example implementation for the positive-negative dual-rail output also uses 47 µH/5 A and whoever written was too lazy?3a) Is it even necessary to implement a differential mode inductor (Figure 3)?3b) Given the designer for the example board seems to have implemented 3 independent inductors, I imagine said 3 inductors would just be relatively largely-sized inductors just for noise filtering?Figure 1. The XL6019 board1.Disclaimer: Reproduced without explicit permission from the item lister.Figure 2. Manufacturer example implementation for a Positive-Negative Dual-Rail Voltage output.Figure 18onpage 11of the Datasheet[sup2.Disclaimer: Reproduced without explicit permission from the IC manufacturer.Figure 3. 3 Inductors for the manufacturer example implementation. Source is the same asFigure 2.Disclaimer: Reproduced without explicit permission from the IC manufacturer.I have also attached a PDF of the XL6019 Datasheet and the figures.Edits: Managed to get images to appear inline with text.Links1~10 W Positive-Negative Dual-Rail Output Board Link:https://www.ebay.com/itm/5V-6V-9V-10V-12V-15V-24V-Positive-Negative-Dual-DC-DC-Boost-Buck-Converter/1241949624692XL6019 Datasheet Link:http://www.xlsemi.com/datasheet/XL6019%20datasheet-English.pdf

author: ledtester
author_rank: Super Contributor
timestamp: October 18, 2020, 07:46:33 am
content: This looks very similar to a kit reviewed in these two videos:https://youtu.be/XMnjllRMoy4https://youtu.be/LyCYFk4Gh0AThe first video goes into more depth on the design theory (starting around 9:40). In particular, a paper is found which states (but does not explain) that the inductors do not need to be coupled for this design to work.There are some performance measurements in the Banggood customer comments:https://www.banggood.com/Original-Hiland-DIY-USB-Boost-Single-Turn-Dual-Power-Linear-Regulator-Multiple-Output-Power-Module-Kit-p-1022517.htmlLook for one made by "jeever" on 2018-02-09 08:21:33. Google translate seems to do a good job translating it into English.

author: Le_Bassiste
author_rank: Frequent Contributor
timestamp: October 18, 2020, 12:35:13 pm
content: this is not about differential inductors, but individual inductors that store and release energy at different switching phases of the converter. google "SEPIC" for the principle of operation.CDC and C23 do the grunt work of energy transfer, hence an extra (omissible) core would just assist the energy transfer and would give a benefit in efficiency.

author: David Hess
author_rank: Super Contributor
timestamp: October 19, 2020, 03:09:33 pm
content: Quote from: lilJohn on October 18, 2020, 02:37:04 amSEPIC converters commonly use coupled inductors because the volt-second product across each one is identical, but this is not required and individual inductors will also work. Using a single inductor core with multiple windings is usually less expensive.QuoteNo, the inductors in a SEPIC converter store significant energy and participate in power transfer.

author: lilJohn
author_rank: Contributor
timestamp: October 20, 2020, 01:36:01 am
content: Quote from: ledtester on October 18, 2020, 07:46:33 amHey, thanks for forwarding these links! Especially loved the overview of and further information on SEPIC-Ćuk and the Module Kit was very useful!Quote from: Le_Bassiste on October 18, 2020, 12:35:13 pmHehe, I just noticed I completely glossed over the term "SEPIC + -" Converter on the datasheet. Quite interesting that for the past week when I googled for something along the lines of "negative DC voltage output" or "negative DC voltage from positive DC voltage" the articles (i.e. Quora, Reddit, some IC manufacturer websites, and some blogs) always presented my options to be limited to: a charge pump (low power output, i.e. ~100 mA most for |12 V| iirc), buck-boost converter (see "some IC with dual-supply output" but change it to single-supply output and decrease the cost a bit), or some IC with dual-supply output(~$4 if <100 mA and/or ~|5.5| V and up to ~$10 if both ~100 mA and >|10 V|). I guess I am just too obsessed with cost and reliability and the charge pump wasn't up to spec.Quote from: David Hess on October 19, 2020, 03:09:33 pmSweet, thanks!edit: changed "~50 mA" to further specify low power when talking about the specs of a charge pump on market or making one oneself.