{"id":32376,"date":"2020-10-16T14:12:38","date_gmt":"2020-10-16T18:12:38","guid":{"rendered":"https:\/\/pappp.net\/?p=32376"},"modified":"2020-10-16T14:12:38","modified_gmt":"2020-10-16T18:12:38","slug":"interesting-but-disappointing-mini-buck-boards","status":"publish","type":"post","link":"https:\/\/pappp.net\/?p=32376","title":{"rendered":"Interesting (but disappointing) Mini Buck Boards"},"content":{"rendered":"\n<figure class=\"wp-block-image size-large\"><img loading=\"lazy\" decoding=\"async\" width=\"764\" height=\"1024\" src=\"https:\/\/pappp.net\/wp-content\/uploads\/2020\/10\/qskjbuck-764x1024.jpg\" alt=\"\" class=\"wp-image-32382\" srcset=\"https:\/\/pappp.net\/wp-content\/uploads\/2020\/10\/qskjbuck-764x1024.jpg 764w, https:\/\/pappp.net\/wp-content\/uploads\/2020\/10\/qskjbuck-224x300.jpg 224w, https:\/\/pappp.net\/wp-content\/uploads\/2020\/10\/qskjbuck-768x1029.jpg 768w, https:\/\/pappp.net\/wp-content\/uploads\/2020\/10\/qskjbuck-1146x1536.jpg 1146w, https:\/\/pappp.net\/wp-content\/uploads\/2020\/10\/qskjbuck-1528x2048.jpg 1528w, https:\/\/pappp.net\/wp-content\/uploads\/2020\/10\/qskjbuck.jpg 1560w\" sizes=\"auto, (max-width: 764px) 100vw, 764px\" \/><\/figure>\n\n\n\n<p>I needed some cheap little vregs recently and had run out of and\/or lost all of my useful-value 780x linear parts, so I decided to look at what people in this century use.\u00a0 <\/p>\n\n\n\n<p>I found some little buck boards roughly the size of a TO-220 package that looked exciting.  These particular ones are QSKJ Mini DC-DC Buck Step Down Module model &#8220;QS-1205CME-3A&#8221;, Vendor page <a href=\"https:\/\/www.qskj.cc\/shop\/product\/1941621-mini-dc-dc-buck-step-down-module-4-24v-12v-24v-to-5v-3a-power-module-qs-1205cme-3a-79148?page=3&#038;category=2661\">here<\/a>, mine were <a href=\"https:\/\/www.amazon.com\/gp\/product\/B0758ZTS61\">5pcs\/$9 from Amazon<\/a>.\n\n\n\n<\/p><p>Upon analysis they have serious issues with regulating under load, so the hunt for something decent continues, but the form-factor and advertised feature set are really compelling. <\/p>\n\n\n\n\n\n<p>Pros:<br \/>\n<ul>\n<li> High-efficiency high-frequency synchronous buck instead of a linear heater^H^H regulator. <\/li>\n<li>Solder-jumpers for 1.8,2.5,3.3,5,9,12V or a default (fiddly, tiny) adjustment pot output so you only have to stock one device &#8211; one easy-to-cut trace to disable adjustable mode. <\/li>\n<li>Tolerates 4.5-24V input as long as out &lt; in or so. <\/li>\n<li>Good stability to input voltage variation.<\/li>\n<li>~0.25V drop-out.<\/li>\n<li>Does appear to have a cutoff for over-current. <\/li>\n<li>No perceptible ripple under various load conditions.<\/li>\n<\/ul>\n<br \/>\n<\/p><p>Cons:<br \/>\n<ul>\n<li>Voltage regulation manages maybe 600mA at 5V before droop becomes unacceptable (&lt;4.8v).<\/li>\n<\/ul>\n\n\n\n<\/p><p>&#8230;and that makes it basically useless for most applications.  Test data below the fold. <br \/><br \/>Maybe it could be resolved with appropriate external capacitors and\/or offsetting the adjustable to regulate right at a known load or something, but not being drop-in really reduces their charm. <\/p>\n\n\n\n<p>Anyone know of a similar offering that doesn&#8217;t suck at output regulation?<br \/>(Rel: Anyone know if any of the low-end electronic loads are worthwhile?  I&#8217;m not looking to spend real-lab-instrument money, but it&#8217;s come up often enough lately that I want to be able to dissipate a couple 10s of Watts through a at least stepwise-controllable resistive load). <\/p>\n\n\n\n<!--more-->\n\n\n\n<p>Tests:<\/p>\n\n\n\n<p>Input stability and drop-out test: <br \/>Set 5V fixed output jumper<br \/>Input hooked to a gigantic bench supply<br \/>Output voltage and stability from a Tektronix MDO3012 oscilloscope showing both the bare waveform and DMM mode. <br \/>Output current by running through a BK 5492B bench meter<br \/>50\u2126 of resistors as a load  <\/p>\n\n\n\n<p>Input &#8211; Output<br \/>20 &#8211; 5.013<br \/>12 &#8211; 5.013<br \/>9 &#8211; 5.013<br \/>5 &#8211; 4.762<br \/>(and it doesn&#8217;t boost, so much under 5 cuts off) <\/p>\n\n\n\n<p>Large load test: <br \/>Input hooked to bench supply at 12V<br \/>Abomination USB AF-AF adapter to connect a USB to Alligator Clip cable to a &#8220;1A\/2A&#8221; load for testing USB Power supplies.  Hand DMMs in series and parallel for voltage\/current. <\/p>\n\n\n\n<p>12V input, dummy load for nominal 1A (apparently 5.33\u2126) and 2A (apparently 2.75\u2126) at 5v<br \/>(1A setting) 700mA@4.2V<br \/>(2A setting) 1A@2.3V (LOL)<br \/><\/p>\n","protected":false},"excerpt":{"rendered":"<p>I needed some cheap little vregs recently and had run out of and\/or lost all of my useful-value 780x linear parts, so I decided to look at what people in this century use.\u00a0 I found some little buck boards roughly &hellip; <a href=\"https:\/\/pappp.net\/?p=32376\">Continue reading <span class=\"meta-nav\">&rarr;<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[8,37,1,10],"tags":[],"class_list":["post-32376","post","type-post","status-publish","format-standard","hentry","category-diy","category-electronics","category-general","category-objects"],"_links":{"self":[{"href":"https:\/\/pappp.net\/index.php?rest_route=\/wp\/v2\/posts\/32376","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/pappp.net\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/pappp.net\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/pappp.net\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/pappp.net\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=32376"}],"version-history":[{"count":0,"href":"https:\/\/pappp.net\/index.php?rest_route=\/wp\/v2\/posts\/32376\/revisions"}],"wp:attachment":[{"href":"https:\/\/pappp.net\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=32376"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/pappp.net\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=32376"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/pappp.net\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=32376"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}