Possible power supply project. - Page 1
Forum section: electronics / projects

author: davelectronic
author_rank: Frequent Contributor
timestamp: January 26, 2019, 12:53:57 am
content: I've been meaning to try something with a power supply idea. But I'm uncertain over a couple of possible issues.So what I have is a couple of 135 watt 19.5 Volts power bricks, I was going to try and put a small unit together with a project box. I would be looking to drop the 19.5 Volts to a usable 13.80 Volts. I know I must stay with in the psu bricks power limit, even at a reduced voltage. As a fixed voltage output, I was going to use a buck converter, and small led panel meter in the project box.The couple of obstacles are the possible switching noise of the converter, and the input to the project box. The power brick is a hp model of 135 watts with a barrel Jack of 7.4mm OD and 5mm ID, I can't seem to find a chassis socket for this size connector. I could change the interface arrangement to multipole metal connectors, but then the psu brick can't be used as a PC power supply anymore. Not tragic I know, but would be cool to keep the psu bricks input contact scheme.The other unknown is noise of the dc to dc buck converter, the main use of this project box adapter, if you can call it that, would be powering RF equipment. Things like transceivers and scanners. At the present time I don't have use of an oscilloscope to test the buck converter under load. Below is a picture of the converter, I know it needs cooling to achieve higher currents. I wouldn't be pushing it the the maximum ratings of 8 to 10 Amps, typically 5 to 6 Amps , and even then at a 50% duty cycle for transceivers use.Is it feasible to use a buck converter like this ? And any info on a 7.4mm x 5.0mm chassis socket would be handy.Thanks for reading, any help appreciated.

author: cdev
author_rank: Super Contributor
timestamp: January 26, 2019, 01:19:37 am
content: Are those converters "unconditionally stable"?I remember there was one specific thing that could happen and now I forget what it is. Maybe I'm wrong.Also, you never get something for nothing tradeoff wise. For the typical uses, they are very hard to beat, especially when you need the ability to adjust current. However, they may be noisy for RF without some additional care taken to filter out noise.Also, make sure those heatsinks get a good airflow around them.

author: sleemanj
author_rank: Super Contributor
timestamp: January 26, 2019, 01:44:20 am
content: This aliexpress sellerhas a 7.4x5.0 female to 5.5x2.1 male adapter (option F).No relation, not purchased, just the first I found.

author: davelectronic
author_rank: Frequent Contributor
timestamp: January 26, 2019, 02:56:24 am
content: Thank you for the replys and links. I'm not certain on there stability, purchase ratings look good across Amazon and eBay. I know there is something mentioned about non isolation, at least I think it's that. The dc chassis socket link, thanks for that, but it would add to the length of the plug chain. Must be a 7.4mm x 5.0mm dc chassis socket somewhere in the world. Thanks again for your help.

author: davelectronic
author_rank: Frequent Contributor
timestamp: January 26, 2019, 03:00:20 am
content: Just as much as I can find on these converters. Not much, but might hold a clew as to noise issues maybe.8A DC-DC BUCK CONVERTER STEP DOWN 8-40V TO 1.25-36V WITH CURRENT CONTROL XL4016EXAMPLE APPLICATIONS:• High-power, constant current LED driver• Battery charger• Vehicle-mounted power supply• Low voltage system power supplySPECIFICATIONS:Non-isolated step-down CC CV Buck module with on-board red/green LED load indicatorInput voltage: DC 8V - 40VOutput voltage:DC 1.25V - 36VOutput current: 8A continuous, 10A peak (switch current limit, with cooling)Output power: 288W continuous.No-load current: ~ 2.1mAConversion efficiency: ~ 96%Operating temperature: -40 °c to +85 °cProtections: thermal shutdown/current limit/output short/input over-voltageDimensions: 65 x 47 x 22mm (L x W x H)On-board LED load indications: red = load present (eg. 'battery charging'), green = no load (eg. 'battery charged' or output disconnected)

author: sleemanj
author_rank: Super Contributor
timestamp: January 26, 2019, 04:42:35 am
content: https://item.taobao.com/item.htm?spm=2013.1.0.0.2420e293DWiHhI&id=539342461709

author: davelectronic
author_rank: Frequent Contributor
timestamp: January 26, 2019, 12:02:44 pm
content: Thank you for the link, that certainly looks like the socket module.Not sure about the seller, but worth a try on purchasing a couple.

author: elecdonia
author_rank: Frequent Contributor
timestamp: March 20, 2019, 04:28:45 pm
content: I've been researching these "DC-DC converter modules" which are readily available from a vast number of Asian vendors. The prices are incredibly low, sometimes < 1.00 USD. Performance and quality are, of course, rather variable.I am conducting detailed tests with a number of these modules and will be posting my results and recommendations here on this forum.My particular interest is in small DC-DC converter modules which have very low "quiescent" current when lightly loaded. I am searching for units with "no-load" input current <10 mA.DC-DC converter modules with the "buck-boost" architecture, often referred to as "SEPIC," can permit operation with any raw input voltage source between 5V and 24V, while producing a regulated output voltage of either 5V or 3.3V. This is very convenient for many small projects containing Arduino MCU boards along with small LCD displays, sensor devices, small relays to control larger loads, etc.The reason for preferring a "switching regulator" is that linear regulator IC chips, such as the LM1117 or 7805 often found on Arduino boards, are very inefficient when converting a 12-15V input into the 5V or 3.3V required by the Arduino and associated circuitry.Another weakness of Arduino "on the board" linear regulators is that many of the Arduino low-cost "clone" board manufacturers are using mislabeled and unspecified voltage regulator IC chips. These may have specs and performance very different from the regulators found on "genuine" Arduino boards. For example I recently obtained a large amount of Arduino Pro Mini clone boards from Asia. Their on-board voltage regulator IC chips all failed catastrophically (with copious smoke and popping noises) when 12V was applied to the "Vraw" input pin on the Pro Mini board. The regulators on these Arduino clone boards could only handle maximum input voltages of 9-10V. In contrast genuine Arduino boards come with regulators which can accommodate up to 15V of input.I would like my projects to accommodate any input voltage between 5 and 24V without failure or malfunction. My goal is to be able to grab any old power supply brick that I can find and use it. The most common output voltages for small AC-DC power supply units are: 5V, 9V, 12V, and 15V. So I would like to come up with a design for a cheap, small, and efficient input voltage regulator that will supply power to the Arduino and its peripherals from any source voltage between 5V and (ideally) up to about 24V.Best regards