Electrical Engineering Stack Exchange
Electrical Engineering Stack Exchange

Questions tagged [switch-mode-power-supply]

A switch-mode power supply (SMPS) switches been fully-on and fully-off states quickly to maintain voltage regulation. They offer lower power dissipation and run cooler than linear regulators that continually dissipate power through a transistor.

Switching Power Supply Design
ISBN: 978-0071482721 (3rd Ed.) by Abraham Pressman, Keith Billings, Taylor Morey

2890 questions
74
votes
3 answers

What is the ideal way to handle data pins D+ and D- on a USB power adapter to be compatible with fast charging on devices?

I have found that many USB wall chargers use a resistive voltage divider to set the D+ and D- pins to a specific voltage, usually between 2 and 3 volts. Other USB wall chargers short the D+ and D- pins together with no connection to anything else. …
ArraysStartAtSeven
  • 907
  • 2
  • 8
  • 9
73
votes
3 answers

What does the Y capacitor in a SMPS do?

It seems that a well-designed SMPS has a capacitor connecting the ground planes of the primary and secondary sides of the transformer, such as the C13 capacitor here. What is the purpose of this capacitor? I've let myself understand that it's for…
Dolda2000
  • 895
  • 1
  • 8
  • 9
54
votes
13 answers

What kind of components in a computer power supply can explode loudly?

Today I heard a loud bang that tripped the circuit breaker in my server room. It must have been really loud because I could hear it 2 rooms away through 2 heavy doors and it was like a firecracker going off right next to me. Long story short, it…
user81993
  • 831
  • 1
  • 9
  • 14
42
votes
6 answers

Can an audio circuit be powered by a switched-mode power supply?

Most audio circuits are powered with large, heavy transformers and a small ripple after smoothing. SMPS are smaller and more efficient. EMI can be shielded by a metal enclosure and the output filtered for noise suppression. Especially where the…
Rob Kam
  • 1,305
  • 4
  • 19
  • 27
30
votes
4 answers

Why do smaller loads require larger inductors in buck regulators?

The MC34063 Application Note lists the equation for calculating minimum inductor size as follows: $$L_{min} = \frac{V_{in} - V_{sat} - V_{out}}{I_{pk}(switch)} t_{on}$$ But this implies that as Ipk(switch) (eg, the maximum switch current) decreases,…
Nick Johnson
  • 7,739
  • 3
  • 28
  • 44
28
votes
1 answer

Unusual chemical reaction on PCB (SMPS circuit)

I have a PCB with smps circuit on it 220V to 5V (using Viper22a). Here is the schematic: And here is the board layout: In the yellow circle region, I am seeing some sort of white deposition in a few PCBs(bottom layer). Please see the images…
Whiskeyjack
  • 7,946
  • 8
  • 53
  • 91
27
votes
4 answers

Spacecraft Power Supply Frequency

I know that aircraft sometimes employ a 400Hz AC system to save weight on transformers, so I'd imagine that spacecraft might employ a similar technique. I'm wondering if anyone in the aerospace field can confirm 400Hz or higher frequency operation…
RYS
  • 1,018
  • 7
  • 15
26
votes
6 answers

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 use a switching-mode power supply (SMPS), say, with a…
sekharan
  • 1,087
  • 2
  • 15
  • 25
23
votes
6 answers

What are some common/popular/go-to switching voltage regulators?

So I've used the popular linear regulators (7805, LM317, LD1117, etc), but I'd like to learn more about switching regulators. Are there any "must have" switching regulators out there that are as popular, as ubiquitous as those common linear ones?
Craig
  • 1,596
  • 2
  • 16
  • 21
22
votes
5 answers

How to safely ground a switching power supply with floating outputs?

I just received a 120VAC to 5VDC (20A) switching power supply (the kind with a passively ventilated metal casing) for use with a microcontroller project I'm working on (driving long LED strips). I've wired up Line-Neutral-Ground correctly to a…
MartyMacGyver
  • 704
  • 1
  • 8
  • 19
21
votes
2 answers

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 output capacitor (47uf) and an inductor (1uH). The…
SomethingBetter
  • 2,260
  • 7
  • 26
  • 33
20
votes
2 answers

Why did they use ultrafast diodes in a 50 or 60 Hz bridge?

This is again from an HP power supply (PSU). The incoming 230 V is rectified into 340 VDC and is fed to a switched-mode supply. The odd thing here is that the manual for that unit, HP6023A, has different diodes for CR1, CR3, and CR2, CR4. CR1 and…
AndersG
  • 526
  • 3
  • 10
20
votes
2 answers

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 converters to feed a strange craving to understand…
scanny
  • 7,062
  • 5
  • 47
  • 87
19
votes
6 answers

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 not build a buck converter as a switch that charges…
Nick Johnson
  • 7,739
  • 3
  • 28
  • 44
18
votes
2 answers

Why is a lower switching frequency more efficient?

I'm designing a 10V to 3.3V step-down converter. Looking at the LT8610, the applications example shows two similar circuits that have different switching frequencies. The Efficiency vs Frequency plot shows that a lower switching frequency is…
Atav32
  • 745
  • 2
  • 9
  • 21
1
2 3
…
99 100