Questions tagged [power-supply]

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

Filter by
Sorted by
Tagged with
6
votes
3answers
617 views

Pass device selection for bench DC power supply

I'm designing a DC Bench Power Supply. This one will be 0-30V, 0-300mA, but I expect I'll try some heftier models once I've gotten this one worked out. I'm following the general design procedure ...
4
votes
2answers
1k views

Open a circuit when voltage exceeds a certain value?

General question I would like to protect a load against overvoltage by cutting one of its power lines when the voltage exceeds a set value. All the examples I have seen online present a way to ...
4
votes
3answers
15k views

LM317 based power supply with current limiting

I'm trying to build my own Bench Power Supply but I'm having a hard time to find a good design (circuit/project) for it. Here are my requirements: Input: main using a 18V 2A transformer Output: 0-...
16
votes
6answers
43k views

How do I convert 9 V DC to 5 V?

What's a good way to reduce the output from a 9V battery to the 1.8V to 5V required by an ATmega328 controller? The context is a small robotics platform with low power requirements (very slow movement)...
13
votes
3answers
10k views

OpAmps - Single Supply or Dual?

I'm trying to pick an op-amp and I'm having trouble figuring out if the op-amp needs a positive and a negative power supply or if I can connect it to ground and the positive supply. What do I need to ...
13
votes
5answers
10k views

What are the basics of making a rechargeable battery pack?

We have a device that runs off of a AC adapter, or a pack of 8 AA batteries. Since in normal use we use both, it would seem to make sense to have the battery pack recharge while using the AC adapter - ...
12
votes
5answers
35k views

Could a modified sine wave inverter destroy/damage the AC adapter for a laptop?

I recently encountered a scenario where I attempted to use a Energizer EN500 modified sine wave inverter to provide power to a Dell 180 watt AC adapter. The circuit powering the inverter was 12 volt, ...
8
votes
3answers
3k views

Help with power-loss protection using capacitor

I designing a circuit will store log data to an SD card. The information will be coming form a parent circuit that this one plugs into. The parent circuit will supply 5V to my daughter card. The ...
7
votes
4answers
2k views

How does a wireless charger work without a magnetic core passing through both “coils”?

Every time I hear the description of a wireless charging system it goes like this: "remember a transformer? It's the same here - one coil is in the base and another is in the device and when you put ...
5
votes
3answers
9k views

Ground loop? Switch mode power supply noise

I have a single 12V supply powering a 12V class D audio amplifier (Tripath TA2020 based, model 'SMSL SA-36') (C) and a very cheap 12V to 5V 2A rated switch mode converter (A). The 5V is used to power ...
5
votes
3answers
5k views

Is it safe, or even possible, to draw more power from a USB port than it was designed to provide

One of the products being shown a CES is a dongle intended to let you charge a tablet from a laptop USB port that normally wouldn't work because it didn't provide enough power. The CNET writeup ...
5
votes
3answers
4k views

Measuring voltage/current digitally on two separate power supply rails

I'm designing a dual-rail DC power supply, with the two rails completely separate (except for sharing a dual-secondary transformer). The main design should work as-is, only by adding a fuse + mains ...
5
votes
2answers
19k views

How to measure max current of a power supply

I have a 220V to 12V adapter. According to the adapter label, the max current can reach 1.5A. But I want to measure the max current it can reach without depending on the information written on the ...
3
votes
4answers
1k views

Delayed power supply startup

I would like to make a circuit that turns on a power supply to a microcontroller after holding down a button for a period of time (say 2 seconds). To make matters slightly more complicated, if ...
18
votes
4answers
17k views

What is “foldback short circuit protection” in a power supply?

I am looking at buying a 24V power supply. Two of the options are these: PSP24-060S 24 VDC 2.5A (60W) power supply PSB24-060-P 24 VDC 2.5A (60W) power supply The first offers "foldback short circuit ...
11
votes
3answers
3k views

Simple \$12V_{AC}\$ to \$12V_{DC}\$ Rectifier

I want to convert a \$12V_{AC}\$ power supply output to use \$12V_{DC}\$ to power some outdoor LEDs. The power supply as it stands will light the LEDs (with a slight flicker from the reverse ...
9
votes
4answers
5k views

Precision CC CV circuit or power supply

I want to design a CC/CV (constant current/constant voltage) circuit in which I can set the voltage limit or current limit with DAC's 0 to 5V range. I know how to design variable CC circuits and CV: ...
8
votes
2answers
5k views

Driving a LED from a wide ranging input voltage

I have been working on a small linear power supply, capable of regulated output between 2V to 30V, using the LM338 IC. For the most part it is a simple implementation taken straight from the datasheet....
8
votes
1answer
691 views

Why does short distance wireless energy transfer have such low efficiency?

Wikipedia and numerous other sources cite the following statement about Magne Charge high-power inductive charging system: For example, the Magne Charge system employed high-frequency induction to ...
8
votes
4answers
625 views

BJT Puzzler: Common Emitter or Emitter Follower?

A few high-reputation members have disagreed on this in the context of other questions, so I thought I'd post it as a separate question. Question: Is the NPN BJT in this circuit configured as common ...
7
votes
1answer
3k views

What component of my phone charger produces chirps and how does it do that?

My Nokia cell phone is charged with a very lightweight compact charger similar to this AC-15 (can't find the one I actually use). While the battery is close to empty the charger works silently - just ...
6
votes
2answers
493 views

What is this RC local feedback configuration?

I'm studying power converter control loops using Christophe Basso's book Designing Control Loops for Linear and Switching Power Supplies. A very common pattern in the compensator circuits is a ...
6
votes
2answers
2k views

Is it safe to implement a split power supply from two identical AC/DC adapters? [duplicate]

If I have two identical AC/DC adapters(Such as laptop adapters) can I achieve this as in the following illustration? Would it be safe?:
6
votes
3answers
2k views

How should power be supplied for in-system programming?

I'm trying to program an ATmega328 with an AVR-ISP-MK2 from Olimex. The programmer has a setting for whether to supply power to the target board or not. The connector has +5V and GND pins. I wanted to ...
6
votes
5answers
1k views

What kind of DC power supply has least noise

I operate an MEG system (extremely sensitive magnetic sensors for measuring brain activity) and I recently found that the DC power source that feeds into our magnetic shielded room (power used for ...
5
votes
1answer
9k 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 ...
5
votes
3answers
1k views

Snubbing DCM (nonsynchronous) Buck converter

FINAL UPDATE: I've posted an outcome report below. I'm very satisfied with how this has come out and I learned a lot in the process. More details and before/after shots in the answer below. Thanks to ...
4
votes
2answers
911 views

Are we close to a pure DC (or hybrid) household? [closed]

This is a philosophical question. Over the last few years, many of the household devices, particularly those that are more mobile and etc are DC devices. Are we at some point where a DC household may ...
4
votes
2answers
535 views

Reducing volume for a split-phase 230VAC@60Hz sealed power supply providing 5VDC@50mA

I'm a hobbyist interested in re-designing and implementing a DC power supply providing a \$+5V_{DC}\pm 200mV\$ output with a current compliance of \$50mA\$ (I could live with \$30mA\$ successfully) ...
3
votes
4answers
10k views

Charging 3 AAs in series

I'm currently repairing a project built by someone else and want to avoid tinkering with it as much as possible. I am looking to recharge 3 AA NiMH batteries (at 1.2v each), that are in series. I ...
3
votes
5answers
3k views

Powering a breadboard with USB

I've recently become quite interested in building small breadboard computers. I've been reading a site that seems to be aimed for beginners, that builds a simple breadboard computer using the 6502 and ...
3
votes
4answers
9k views

5V and 3.3V power supply

I too want both supplies (3.3v and 5v) in my circuit and made these schematics: On 5v supply typical load current is ~8mA. On 3.3v it is ~30mA. Regulators are lm1117 in both cases,sot-23 packages ...
1
vote
5answers
7k views

How can I connect two different DC power sources together?

How can I connecting two different DC power sources together? for example 15Vdc(5Amp) with 5Vdc(2Amp). I want to make one DC source (20Vdc,7Amp) by more powerful supplies.
19
votes
2answers
1k views

How does this wall-wart switcher work?

UPDATE I've provided a full outcome report in one of the answers below with an updated schematic and description of the operating principles as I've come to understand it. I'm studying switching ...
13
votes
2answers
34k views

What is the use of magnets around electrical cables?

I haven't seen any for a while now, but a couples of year ago I saw some several times: cylindrical magnets around electrical wires. I'm not talking about specialized equipments but items of everyday ...
11
votes
3answers
3k views

A 1USD 11W led bulb circuit and parts analysis

I know this is not a huge deal, but still I want to do it because for Three reasons: 1, it only costs 1 usd. Yep, this is a very cheap led bulb, and I need to take it apart to see if it's trust worthy....
9
votes
4answers
29k views

Can I use multiple 18650 batteries in parallel with a standard MicroUSB 3.7V charger board?

There is this Bluetooth Audio Reciever/Amplifier board that I'm looking to get from ebay, and according to the diagram, there's a MicroUSB 3.7V lithium battery charger component in it. With my ...
8
votes
1answer
4k views

7 port powered USB hub backfeeding to my PC

I just bought two 7 port usb hubs: LogiLink UA0124. Just to run into a strange situation. I did some servicing to my PC today and disconnected the main power cord from the PSU. Only to find out that ...
8
votes
2answers
15k views

Operating a Switched Mode Power Supply without a Load

Background I'm a second year student at university, and wanted a simple power supply to test a couple pet projects without going all the way to the lab. I picked up a Power-One MPU150-4350 on the ...
8
votes
1answer
3k 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 ...
8
votes
7answers
18k 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 ...
7
votes
1answer
2k views

What is the purpose of parallel RC network in the bridge rectifier output?

Can anybody explain the necessity of the RC network shown in the figure. I found this in circuit for a logic power supply using Fly-Back converter?
7
votes
2answers
15k views

LM317 Heat sink, how big?

Thanks to the help of a few of the other guys I have my AC to DC rectifier working, and the rest of the power supply working. Now while testing the power supply, my 18V AC transformer gets rectified ...
6
votes
4answers
2k views

Is it dangerous if I do not connect the ATX shield to ground?

I'm living in an Asian country and there isn't a ground connection provided on sockets here. There is only L (live) and N (neutral) so I need to use a 3-to-2 converter. It means that the ATX case does ...
5
votes
1answer
6k views

Adding a battery backup to a circuit with external power supply

I want to add a LiPo rechargeable battery backup to an existing RTC circuit, but I can't alter the preexisting circuit. Basically, the regulator, D2 and RTC (Existing Circuit) are all fixed and can ...
4
votes
1answer
8k views

Best way to filter DC-DC output noise

This question has rised due to the below issue, where a analog design board was scraped due to too much noise from switching regulators eliminating-those-unwanted-op-amptia-outputs the design which ...
4
votes
3answers
456 views

How would you detect vampire/standby power?

Is it possible to detect when a device is consuming power in a stand-by or nominally off state? For example if I leave my charger plugged in, detect that a small amount of current is being drawn and ...
3
votes
2answers
3k views

How long will a battery last based on these numbers

Hi I asked this question on SU but seemed to have gotten into a bit of trouble, I was referenced here. I am getting into doing hardware build based on things like microcontrollers and microprocessors....
2
votes
3answers
2k views

Switching between power supplies - USB dominant

I'm trying to create a data logger. I want the data logger to be able to run in 2 modes. Bench mode (usb powered 5V) Field mode (externally powered 3.3 - 12V) Bench mode is active whenever power is ...
2
votes
2answers
14k views

how can i increase the output current in a transformerless power supply?

I am designing a 12VDC, 200mA transformerless power supply using 1N4007(diode) for rectification, a ceramic capacitor 475k and 10R resistor for limiting, a zener diode (1N4742A) for a regulated output....