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Questions tagged [power-supply]

An electronic device which supplies electrical energy to a load. Can be AC or DC input. Typically DC output.

-7
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3answers
2k views

Why graphical representation of a DC current/voltage is a straight line? [closed]

Why does graphical representation of a DC source always a straight line?
13
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6answers
11k views

Why do buck (step-down) switching regulators require an inductor and diode?

So, I understand, at least at a basic level, the method of operation of switching converters, both buck and boost. What puzzles me, though, is why buck converters in particular aren't simpler. Why ...
21
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6answers
25k views

Can the noise of any switching PSU be attenuated if I put linear regulator before the output?

A friend told me that noise of any switching PSU can be attenuated if I put linear regulator before output. Is that true? For example, if I want to power a +-12 V op-amp for an amplifier, I can ...
12
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1answer
23k views

How much current can you pull safely off a standard AAA battery?

This might be a stupid question. But how much current can you safely draw from a AAA battery. I am currently powering my project from a worktop power supply and it draws at 5V 0.45A during normal ...
13
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5answers
7k views

24VAC/5VDC power supply design

I am planning to create a water valve controller using an MCU and a set of solenoid-controlled valves. The solenoids run on 24VAC (40mA inrush, 20mA holding). The MCU is on a board that draws ~100mA, ...
9
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3answers
6k views

What is a good power electronics textbook? [closed]

I really want to learn as much as I can about power electronics, switching mode power supplies, and overall analog design. Unfortunately my universities computer engineering program is still ...
21
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6answers
20k views

Benchtop power supplies: linear vs switching? [closed]

I'm looking into getting a decent benchtop power supply ($150-300) for hobby-level electronic design and testing. I don't want to modify or use a computer ATX supply because I want: Adjustable ...
18
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2answers
19k views

What might be the cause of high pitch sound coming from a switching regulator circuit

We designed a switching regulator circuit using a 1.5Mhz, internal-switch, switching regulator (semtech.com/images/datasheet/sc185.pdf). Vin is 5V, Vout is 3V3. We have an input capacitor (47uf), an ...
13
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4answers
20k views

12V DC UPS for Network Equipment

My requirement is to keep running supply of low power devices like DSL modems, etc. Most of these devices input 12V/9V DC so i don't see the value in using ordinary UPS which converts DC to AC then ...
27
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7answers
32k views

How to find the ESR of a capacitor

I am building a power supply circuit, and the switching regulator (L4963) calls for a low-ESR output capacitor. The capacitor in question is C3 of the evaluation board circuit. What does "low" mean? ...
8
votes
4answers
15k views

Circuit to safely power-down Raspberry Pi

I want to use a Raspberry Pi as an XBMC server in the car. The XBMC docs say that you should always use the shutdown command before disconnecting the power. I don't want to have to (tell my wife to) ...
3
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3answers
9k views

Making LM317 output voltage adjustable down to 0 V

I want to design a variable voltage regulator that will get from it`s maximum output (lets say 10V) down to 0V (or very close) considering the input as regulated 12V (from a PC power supply). All the ...
22
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6answers
8k views

Voltage regulator vs. voltage reference

I need a cheap, somewhat accurate (~0.5%) voltage reference for some DACs. At first I was going to use a LDO voltage regulator (a TC1223 specifically) for this, it seems to fit the bill looking at the ...
13
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5answers
40k views

24V 3A from ATX power supply?

I am looking for a cheap way to get +24V DC max 3A from computer power supply. I prefer easy soldering solution like DIP, and standard components that do not need to be purchased over internet. Any ...
13
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2answers
20k views

How can I tell (easily) if my power supply is regulated/switched or unregulated/nonregulated?

I found this great blog post about unregulated vs. regulated and switched power supplies. I've got a specialized need for a Regulated 12v power supply and a handful of wall-warts and bricks laying ...
12
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1answer
2k views

Noise problem with buck/boost switching regulator

I am designing a electrical device for a research project (I'm a PhD student, but unfortunately not EE!). More info on the device can be found at http://iridia.ulb.ac.be/supp/IridiaSupp2012-002/ The ...
9
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3answers
5k views

How to dimension a power supply transformer?

I always hesitate when dimensioning a transformer for a DC power supply, and I guess I sometimes overdimension them. My confusion stems from the difference in transformer and DC voltage. If I need 10V ...
7
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2answers
3k views

Automotive power filtering, protection - feedback needed

I'm working on GPS tracker for automotive applications. Device should work in 9V-30V supply voltage range. In practice it will be fed from 12V car installation. This enforces the implementation of ...
6
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5answers
4k views

Ultra low noise power supply

I am trying to design an ultra low noise power supply for my sensitive circuit. The supply will provide 5V and 600mA. (Worst case, 200mA typical). My input voltage is 2V to 4V. My ripple target under ...
5
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3answers
10k views

Simplest possible 5V to +/- 10-15V converter (for op-amps)

Im looking for simplest possible solution to power op-amps from USB or phone charger. Requirements: +5V input voltage ±10V to ±15V output voltage at least 10mA output current on both rails (+/-) ...
13
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2answers
22k views

Converting passive USB Hub to powered USB Hub, by adding regulated wall-wart as power supply?

From a quick price-check on ebay, Passive (bus-powered) USB Hubs - ~ $2-$5 Powered (externally) USB Hubs - ~ $15-$20 My use-case is to expand the no. of USB ports on a ARM-based SBC, and to embed ...
11
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4answers
4k views

Is current flowing backwards a bad thing?

In the circuit below: I find it awkward that the direction of the current on the 2V power supply is running opposite to the direction of the current on the 5V power supply. In the 5V power supply the ...
10
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3answers
8k views

How do I design a device to automatically switch to the backup battery?

I've been told that many kinds of batteries work best if they are used until they are completely drained, and then recharged. (Edit: The "memory effect myth" is quite widespread. Batteries work just ...
10
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1answer
3k views

Simulating an automotive load dump with a bank of charged capacitors?

I've been working on a data logging device that will eventually go into my personal vehicle. I've scoured the interwebs and built what, in theory, should be a fairly stout power supply capable to ...
9
votes
2answers
16k views

What is the COM terminal on a DC Power Supply?

We have a HP E3631A power supply at my university's lab. There are 6 ports. My questions are as follows. What is the green port titled 240VDC Max? I was explained to an extent that it was the ground ...
9
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2answers
16k views

Calculating Power Loss in Switching Power Regulator?

I am new to the construction of DC/DC power supplies (still a university student) and have built basic supplies using simple linear voltage regulators. I have recently discovered the world of ...
9
votes
4answers
3k views

Different ways to digitally control an adjustable SMPS

I want to make a battery powered, adjustable SMPS for use in situations when I cannot have an outlet near me, so I would like some more information or suggestions about this topic. The SMPS chip I am ...
7
votes
4answers
4k views

LM317-based adj power supply output takes a while to stablize

I recently built-up a quick little LM317-based adjustable power supply schematic: However I've noticed the output can take several seconds (on the order of 10 or so) to "settle down" after turning ...
5
votes
2answers
2k views

Inductor selection for obtaining a noiseless analog power rail

I interface an image sensor, and the design schematic for power supply is: How do I choose one from the available 3uH inductors based on the specs? I figured the maximum current and dc resistance ...
5
votes
5answers
10k views

Selecting input voltage for 7805

I generally use switching 12V power supplies for my circuits since they are so common, but I understand the 7805 can take a lower input voltage. If I gave the 7805 a lower input voltage (i.e. 9V), I ...
4
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5answers
53k views

Why do we need 3 phase power supply?

Why do we need 3 phase? For the reason that voltage will never be zero in 3 phase? OR we need high voltage?
4
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3answers
741 views

What is the thought process for specifying an EMI bypass cap on line transformer secondary?

Update It turns out I had mistakenly interpreted the role of the capacitor in question here as an EMI filter for line noise. It looks like a capacitor in that position actually serves as a snubber ...
2
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2answers
4k views

High Voltage Series Pass Transistor - Low Voltage Control

I am having some difficulties getting my output stage to work correctly. Here is some info: I have a +48VDC source with a series pass transistor to drive a load between +45V and 0V. The control ...
2
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1answer
6k views

Dual polarity vs dual rail power supply

My previous post turned out to contain too many questions, so I'll focus on the main one first, and figure the rest out as needed. I'm looking at building a DC lab power supply, roughly 1.2-14 volts ...
1
vote
2answers
21k views

Connecting switch-mode power supplies in series to increase voltage [duplicate]

I have two identical 48 V switched power supplies, both of which can deliver the same current of, say, 4 A. Can I connect them in series to get 96 V at 4 A? Is this something ...
21
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2answers
654 views

Which way does electricity power a circuit?

Working with some circuits this summer, I ran into what everyone eventually does: Current flows from + to - despite the electrons flowing (well, bumping into eachother) from - to +. I understand the ...
16
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5answers
2k views

Is this negative regulator really meant to be an inverted positive regulator?

Project: make a power supply that can replace the 240V AC supply shown, so that I don't die when messing with the board that this connects to. I'm only interested in the part inside the yellow box; ...
15
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4answers
4k views

Why are laptop power supplies marked “IT equipment only”?

Laptops are often shipped with switching power supplies that among other have a phrase for use with information equipment only on their body. Why can't I use the same power supply to power a motor or ...
12
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4answers
6k views

Why would a power supply unit with insulating case and galvanic separation need a grounded power cord?

Recently I witnessed an external IBM laptor power supply that looked like a usual switched-mode power brick (rather small and lightweight for it more than 50 watts power) in plastic case but had a ...
12
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8answers
6k views

Apple power supply: thick AC cable, thin DC cable - why?

Apple power supply consists of a very thick, inflexible AC cable (wall outlet to converter) and a very thin, flexible DC cable (converter to computer): Why? The currents through the cables should be ...
10
votes
2answers
2k views

Routing a buck/boost DC/DC converter

I need some help with the layout of a power supply. I botched the first two iterations as I do not have the necessary experience, and I would like to avoid another costly run. For the sake of ...
10
votes
2answers
9k views

How Arduino Power supply works

Can someone please help me in the analysis of this arduino board power supply works To my understanding, In the presence of DC power through the DC jac, Dc voltage is fed to the MC33269 regulator to ...
10
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2answers
13k views

Can an ATX PSU power a USB port directly?

I'm going to build a benchtop PSU from an ATX PSU, and I would like to add a USB charging port on it. It should be able to power an Arduino or charge my (non-Apple) phone. (I know Apple devices ...
10
votes
3answers
1k views

What to do about very hot planar inductor?

What I'm doing: I am designing a DCDC converter to generate ±24v from an incoming supply of 18v - 36v. For this I am using the TI TPS54160, and following the document Create a Split Rail Power Supply ...
9
votes
6answers
5k views

Prevent overcurrent while filter capacitor is charged

I have this circuit: On start-up, the power supply experiences an overcurrent condition, because when the capacitor is charged, it looks like a short circuit as seen from the power supply. How can I ...
9
votes
4answers
12k views

How practical would a car booster using supercapacitors be?

Currently car boosters (a portable unit charged of an outlet and then connected to the car electrical system to start a car when the car battery is dead) typically use batteries - lead-acid, Li-Ion or ...
7
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2answers
9k views

Splitting a power supply between two circuits

I have two separate circuit boards (clock & radio) that I'd like to place within the same enclosure. One takes 12V, and the other needs 3V. How can I utilize one AC adapter to power both boards ...
7
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2answers
65k views

Converting Power/Watts in DC to Power/Watts in AC?

How can we convert Watts in DC to Watts in AC? for e.g A device needs 1A and 12V DC input i.e (1A x 12V = 12 Watts) 12 Watts DC. If we use an AC to DC adapter/converter to generate 1A,12V (12Watts) DC ...
6
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3answers
12k views

5V to 160V DC converter

I need a DC-DC convertor to bring a 5V input up to 160V DC output. Does anybody know off any of the shelf parts that would manage this? The high output needs to supply minimal current (uA) we really ...
6
votes
3answers
38k views

Converting a DPS800 server PSU into a standalone 12V PSU

I recently got my hands on 2 server PSUs from a HP Proliant DL380-G5. HP model DPS-800GB A REV 06M Series HSTNS-PD05 Partno: 379123-001 (They appear to be made by Delta, going from the logo on the ...