DC Voltage Conversion - Page 1
Forum section: electronics / projects

author: Bones558
author_rank: Contributor
timestamp: July 08, 2023, 11:07:30 pm
content: I have a 9V 2.5A DC power supply. (If needed I can also get a 9V 3.5A DC supply.)I need to get an "odder" voltage out of it, 10V DC.How can I design a simple circuit to step-up from 9V to 10V?The more compact/smaller footprint the better.Thanks!

author: Konkedout
author_rank: Frequent Contributor
timestamp: July 09, 2023, 01:17:18 am
content: Basically you want some sort of boost converter. But you did not state how much current you need? How much output ripple voltage can you tolerate? Do you want to build a pcb?

author: Bones558
author_rank: Contributor
timestamp: July 10, 2023, 01:50:30 am
content: I need 1A at the 10V to be output.I have no idea what ripple current it can handle, this is for an old vintage electronic from the early 90s.I'm hoping to keep it small so I can put it inline as part of an adapter cable I'll build.Thanks.

author: ledtester
author_rank: Super Contributor
timestamp: July 10, 2023, 02:02:38 am
content: What exactly is the device? It is possible that it will work on 9V.Update: Also, do you know what kind of power supply the original supply was? Was it transformer based or a switching supply?

author: Konkedout
author_rank: Frequent Contributor
timestamp: July 10, 2023, 04:01:29 am
content: If you can start out with 9V; can you start out with 12V? That will be much simpler. You did not say whether you want to build a circuit board, but from the information you have provided, I suspect that you do not.Some $ expenditure is probably necessary unless you can just use 9V as suggested by another poster. To just make one piece, I think it makes the most sense to buy a 12V power supply and follow it with an adjustable Low Dropout Linear Regulator "LDO" adjusted for 10V. This will create 2W of heat when you have 12V input and 10V 1A output. So it will need a small heatsink. But this all sounds bigger than I think you have in mind.There is a lot more that can be said, but key bits of information are:Do you want to make a printed circuit board? (For something of small size, there are at least two good reasons why a handwired kluge will not work.)Can you start with 12V or maybe 15V instead of 9V? (For an LDO, 12V would definitely be better. If you wanted to go with the best technical solution, that would probably be a synchronous rectified buck regulator, and 12V inputmaybe marginally low for some of them to make 10V output.The boost converter making 10V output from 9V input is completely sound, but there are a lot fewer options out in the marketplace.

author: Bones558
author_rank: Contributor
timestamp: July 10, 2023, 04:17:41 am
content: Thanks for the info so far.To answer the questions posed...I have no problem making a PCB, as long as it is small/micro sized to be practical as in-line within a custom made cable.I need to start with 9V.The original power supply was a big wall brick plug from the 90s, so it was transformer based.

author: Nominal Animal
author_rank: Super Contributor
timestamp: July 10, 2023, 07:27:31 am
content: TI Webench suggested a circuit based onTPS61089RNRR(in VQFN-11) with caps (four in 1210, one in 0805, four in smaller), five resistors (one rated 125mW, the rest 63mW), and a Coilcraft XAL4030-332MEB 3.3µH inductor, that should boost 8.5V-9.5V to 10.0V at up to 1.5A, suggesting over 98% efficiency at or above 200mA. (I can't seem to be able to export the design. If the efficiency figure is correct, then even at 1.5A 10V output – 15W output – it'd generate less than 0.31W of waste heat, drawing only 1.7A 9V.)If you go toWebench, set Vin Min = 8.5, Vin Max = 9.5, Vout = 10, Iout Max = 1.5, Small Footprint, Design Parameters: Use Ceramic Capacitors, Use Shielded Inductors, and Show All Topologies, one of the results should be the TPS61089RNRR schematic with bill of materials. Or, use the Webench link in thedatasheet.If I were doing this, I'd design the board and order the board and board assembly from JLCPCB. They have TPS61089RNRR as an extended part, and it looks like CD73-3R3M inductor might be a suitable replacement for the Coilcraft inductor.I know nothing, though; me just a hobbyist.

author: mariush
author_rank: Super Contributor
timestamp: July 10, 2023, 11:31:04 am
content: Is this a one time thing?If so, you could probably open up your current power supply and change a feedback resistor to adjust the output voltage. A lot of power supplies use a cheap TL431 voltage reference and a couple resistors to compare the output voltage with the voltage reference voltage and adjust output voltage as needed. So by changing the ratio of those two resistors, you could make the power supply "think" the voltage is always low, and increase it to 10v.If you don't want to open the power supply, you could just use a 12v power supply and then use a simple cheap linear regulator to reduce 12v to 10v.If you want up to 3A of current, a basic LM1085 (or any 1085 adjustable, as it's done by lots of companies) will do that. The regulator will need to be heatsinked, as you'd dissipate (12v - 10v) x 3A = 6 watts of heat.