An electronic device which supplies electrical energy to a load. Can be AC or DC input. Typically DC output.
3
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5answers
279 views
Efficiency of a power supply
I need some info on efficiency of power supplies. Imagin a power supply with 91% efficiency that can provide a maximum of 800watts.
Does the rated 91% efficeincy is for all loads that going out from ...
1
vote
3answers
7k 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 ...
9
votes
2answers
2k views
How do the tiny AC->USB power supplies work?
The iPhone and Kindle both come with tiny power supplies that take in 120v AC and output around 5V at 0.85 to 1 amp. They seem to be too small and light to have a transformer, and generate very little ...
8
votes
7answers
19k views
What happens if I connect two different DC voltage sources in parallel?
I have a computer power supply that I'm hacking together as a bench supply. For this particular model to power on, I need a minimum load across both +5V and +12V.
"Easy," I thought, "I'll just ...
6
votes
1answer
4k 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 ...
6
votes
4answers
557 views
How is inductive wireless charging of a moving vehicle on a public road possible in efficient way?
Looks like one of the major problems of wireless energy transfer is efficiency. For example, Magne Charge high power charging system seems to have about 86% efficiency which means that quite a lot of ...
6
votes
3answers
769 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 ...
5
votes
4answers
578 views
How can a PSU be capable of providing more current than it draws from the mains
The supply cable that came with my PSU has a 13A fuse fitted inside it's plug. However on the side of the PSU it says it's cable of producing 30A of current at 5V. How is that possible when it only ...
5
votes
4answers
332 views
Obtaining 15 V from a single lithium polymer cell
I want to get 15V output from a 1 cell lithium polymer battery which has a voltage range of 3v-4v. I am thinking about using a 34063 to accomplish this. But will this work over a 1v range or do I ...
5
votes
3answers
1k 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 ...
4
votes
1answer
706 views
Current limiters using transistors and diodes
I have been experimenting with simulating current limiting circuits. I am trying to limit current to ~500mA given a fixed 4.8V source. I started a question based on a conventional 2-transistor current ...
3
votes
2answers
342 views
Calculating the True Power Factor in non-linear loads
In my circuit I am taking in 60 Hz 120 VAC from the power company and hooking it up to a AC/DC non-linear switching buck converter I am designing.
I know that:
true power factor = (displacement power ...
3
votes
2answers
637 views
Charging affects battery life?
I wish to understand how a battery charger may best be designed in order to maximise the life of Lithium Ion batteries. I have specified Lithium Ion batteries as they are what is used in most laptops ...
3
votes
3answers
1k 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 ...
3
votes
1answer
329 views
What's the need for higher frequency in inductive charging systems?
Consider an inductive charging system like Magne Charge - it has a rather huge "coupler" coil off the vehicle and a corresponding slot on the vehicle and the coils in the "coupler" and in the slot are ...
2
votes
4answers
815 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) ...
1
vote
1answer
2k 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
1answer
334 views
SMPS PCB Design Critic 2
Thanks for your patient help, I am learning a lot. This is my (final, I hope) re-designed layout. What do you think?
10-32V to 5V 1.2A SMPS Buck Regulator Design.
The IC is IFX91041 from infineon.
...
1
vote
3answers
408 views
High voltage/Mid current boost converter
I'm designing a regulator/converter that can generate -120/-108/+60Vdc for a current of 180mA each from a supply of 12Vdc or 24Vdc (5A like it's nothing, 15A tops) and I was choosing a MC34063 but the ...
10
votes
2answers
1k views
Is it safe to disassemble an unpowered PC power supply?
Once a typical PC power is unplugged, is there any danger of receiving a shock while disassembling it? Are there typically high voltages stored that one should be aware of?
context: removing a ...
8
votes
1answer
450 views
Understanding CS5463's basic circuit power supply
I'm trying to put the CS5463 chip functional using the example circuitry on page 41 of the datasheet (attached bellow):
Right now, I'm working on the top part of the circuit, which is the IC power ...
7
votes
2answers
197 views
Grounding and why charge leakage occurs
A basic nugget of info is missing in my end-to-end picture of how grounding works and why it's important. When a voltage is applied in a circuit the electric current starts flowing (or the field ...
6
votes
7answers
1k views
How can I turn on and off a switch every 20 minutes?
I want to make the above switch which will stay on for 20 minutes and then off for 20 minutes. This should be continuous. Actually, I want to place this switch for my air conditioner which I do not ...
6
votes
2answers
1k views
How Arduino Power supply works
Can someone please help me in the analysis of this arduino board power supply works
To my understanding,
1. In the presence of DC power through the DC jac, Dc voltage is fed to the MC33269 ...
6
votes
4answers
970 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 ...
6
votes
4answers
893 views
Some Power Supply Questions - Multiple Rails or Single Rail w/ multiple Outputs?
I'm interested in making myself a 12V power supply. I need one because I often go out to places with little or no power and need some electricity to power my gear (which is basically a telescope, a ...
5
votes
4answers
194 views
Can electronics be damaged by undervolting it?
I was wondering if there are some particularly important mechanism by which one can break electronics, when undervolting it. Its pretty obvious that lots of electronics will not work properly if ...
5
votes
3answers
3k views
Powering laptop from 12V sources without inverter
This question has two parts:
1) How inefficient is it to boost 12V to 120V and then back to 12V as in using a traditional car power inverter to power a laptop (i.e. the 12V car battery power is ...
4
votes
1answer
127 views
How to protect an electronic construction kit (a toy) from damages?
As I child, I had this electronic construction kit called Elektronik 1. It was manufectured in former Czechoslovakia, based on resistors, diodes, bjt transistors, capacitors, an LW+SW radio antenna ...
4
votes
2answers
201 views
Switching a Large Current with a Tiny Switch
I have a SPDT switch that can switch .3A @ 5V. I would like to use it to switch 1A @ 9V which will then be fed into a 7805 linear regulator.
This is the design that I have come up with.
I have run ...
4
votes
1answer
602 views
How can I simulate and handle an automotive load dump?
Long story short, I'm designing a little device to monitor a sensor or two in my car. I'm not an EE, but I'm a stickler for knowing things will work right and that I won't have wasted my time and ...
4
votes
2answers
867 views
How to lay out a schematic for review? Please critique
So, because I haven't posted a schematic for review before, I have no idea how to do it. Apparently, my previous attempt was poor. I got some actionable feedback, but I'm looking for more!
I would be ...
4
votes
1answer
315 views
Why do 0v have to be connected when using two power supplies and ULN2803A?
The other day I was playing with a ULN2803a and a stepper motor. I spent ages trying to work out why it wasn't working and why i was reading ~14V as an output on the PIC I was using. So why did I ...
4
votes
4answers
2k views
how to build a low-voltage disconnect switch for DC 12.4V 70A?
How can I make a device that will make the power connected as long as the voltage of the power-supply keeps over 12.4 V (adjustable) and disconnect it if it falls below?
It also must connect the ...
3
votes
5answers
502 views
7805 regulator outputting 4v instead of 5v
I followed a tutorial on sparkfun to put together 5v power supply. But for some reason I'm only reading 4v coming out of the regulator. I know it's not the regulator because this is the second one ...
3
votes
3answers
213 views
Calculate power supply on distance
I need to provide 12V DC to a DC brushless motors that need 12V 30A at distance of 30m from the source.
The cables I can us are 20 Gauge, I know that the cables are loosing power, how can I ...
3
votes
1answer
213 views
What is the capacity of capacitors in this power supply circuit?
Imagine the following circuit with two capacitors and diodes acting as passive PFC.
My question is what is the capacity of these two capacitors? I mean compared to a circuit with just a single ...
3
votes
1answer
218 views
Battery in parallel with main power source
I have a system that is powered by a main voltage supply and I want to connect it to a battery for backup, in case of power outage.
I need to know what would happen if I connect the system with the ...
3
votes
3answers
962 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 ...
3
votes
2answers
205 views
How to properly isolate multiple power supplies
Say you have a single 110V AC supply and need to use it for a number of devices, each requiring very different characterists. For me personally these are: a direct use of the 110V AC supply for a ...
3
votes
2answers
181 views
cable jacket melts
I am new to hardware.
My breadboard just arrived and I am trying to light up my LED. I used computer power supply for power (red wire for + black for -) and used strands of LAN cable for connect LED ...
2
votes
3answers
162 views
Help me identify the adapter jack
just met an industrial computer which has the following power adapter jack. how to identify this jack and where to find? (actually there are lots of different jacks here and there, how to identify ...
2
votes
2answers
549 views
TL494CN and error amplifier
I'm designing a PWM output for a DC motor and I'm using
TL494CN chip.
It got two error amplifiers and one feedback. I can't understand why there
are error amplifiers and a feedback there? What does ...
2
votes
1answer
693 views
Power MOSFETs and Gate drivers
I'm trying to finally apply what I learned at university in the course of power electronics.
However I find that both that course and most of the books / online references are lacking on some points.
...
2
votes
2answers
113 views
Is there a way to miniaturize cell-phone power adapter
Is there a way to miniaturize a cell-phone power adapter to be not bigger than 1-3 cubic centimeters? Is there a way to do so by using more expensive parts or something like that?
I'm talking about ...
2
votes
1answer
276 views
Capacitor in series and parallel to diagnose APC Smart UPS 1000VA
Brother having APC Smart UPS 1000VA and I noticing high pitched buzzing noise coming from UPS: I think it from power filter capacitor - tall one you see on LHS of picture:
(Picture all sourcing from ...
2
votes
1answer
193 views
Possible to use a Double Layer Capacitor (SuperCap) instead of Electrolytic?
I'm working with a 3V/100mA circuit design that requires short but infrequent bursts of nearly 200mA. A larger power supply is out of the question.
A Capacitor plantation of about 4000uF would cover ...
2
votes
2answers
163 views
What to look in a desktop/small DC Power Supply?
I'm looking for the most adequate power supply that can go between ~0-30v and ~0-5A. These are going to be used for software development for automotive infotainment systems and the operation specs for ...
2
votes
3answers
795 views
Modifying a soldering iron for lower power
I have a 60W soldering iron, which is too much heat for typical electronic soldering purposes. I find myself constantly switching it on and off using a powerstrip to control its temperature so it does ...
1
vote
3answers
363 views
DVD player power supply circuit strange behavior. Need help to understand root cause
I have an old (~8 yrs) Cyberhome dirt cheap DVD player that worked well for the time I was using it. I bought it in 2004 from a Best Buy and was using it regularly till 2010. After we got a new DVD ...
