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.

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6
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1answer
5k views

Analog & Power Ground Planes Doubts

Working on a new board, I have to face some requirements to ensure the performance of the whole system once is manufactured. PCB is a 4-layer one, and it has both analog and digital components. But ...
48
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3answers
23k views

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 ...
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3answers
60k views

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- ...
12
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3answers
12k views

How to choose a inductor for a buck regulator circuit?

I am designing a buck-regulator circuit, with possibly the MAX16974 as the regulator. I have never done such a thing before, and actually not too much analog electronics at all. I got stuck at the ...
8
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1answer
1k views

Do AC inverter H bridges ever get driven this way?

There's a google competition going on at the moment called the little box challenge. It's to design a very efficient AC inverter. Basically the inverter is fed a DC voltage of a few hundred volts and ...
4
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5answers
4k views

SMPS gives “electric shock”

I built the following circuit, a reference VIPer22A circuit. It works fine but I have a little problem. It gives an electric shock on the secondary side. It's not a "line" shock (sticking your ...
6
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3answers
3k views

Why only 500VAC rating for this Y-capacitor?

I’ve been looking through a reference designs for an off-line flyback converters (this one by Texas Instruments and this one by Linear Technology). Both of them have a Y-capacitor between primary and ...
1
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1answer
182 views

Is there a good topology for splitting a DC power supply from a few LM2576 and LM2577?

So, this isn't the most serious project, more of a toy/hack, but I have a some LM2576 and LM2577 and I wanted to see if I could somehow get an adjustable dual rail (bipolar) supply out of them, for ...
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2answers
2k views

How to design a boost converter? And how to specify the inductor and capacitor values?

I want to design a boost converter with input of 48V and need to get to a voltage of 100V. How to select the inductor and capacitor values in it?
12
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4answers
9k views

Why is flyback air gap needed for energy storage?

Why do so many sources say something along the lines "since a flyback transformer stores energy, an air gap is needed"? I have seen this reasoning in textbooks and app notes. I thought air gaps ...
7
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2answers
3k views

Isolation transformer and scope when troubleshooting SMPS

I have a simple question, when troubleshooting a SMPS is highly adviced to use an Isolation transformer. But my question is this, if im using a scope to troubleshoot the "hot" side of my SMPS, both ...
5
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2answers
8k 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 ...
2
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1answer
2k views

Connecting power supplies in series

I need to draw approx 4 amps for 10-15 hours at a minimum of 18V. I have hooked up two 300 watt power supplies in series: +12V on one and +5V on the other: the output is only +15.8V rather than the ...
8
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2answers
10k views

How to calculate suitable dummy load for a power-supply?

A beginner question - feel free to shoot me down I'm looking to modify a retired AT SMPS to drive my ham-radio. This is to be achieved by tying all the +12V wires together so the maximum amperage may ...
3
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2answers
418 views

Bootstrap capacitor - Explanation

i'm taking a course in Switched-mode power supplies and I am a bit confused about the theoretical explanation of what is happening in increasing voltage using a bootstrapped capacitor. You connect a ...
14
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6answers
12k 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 ...
37
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6answers
37k views

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 ...
18
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2answers
20k 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 ...
12
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3answers
2k views

Why is the PCB so large on this SMPS?

In a post regarding heat dissipation in a linear regulator, one answer provided this nice little pin-equivalent smps. It was a great reply, and I'll likely order a few myself. I am wondering though, ...
7
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3answers
1k views

Critique my SMPS buck design

I'm using an LM2734 buck regulator to get +3.3V at 400mA. The datasheet is unclear on how to lay out the supply, so I tried to follow some common sense, keeping all power traces short where possible. ...
12
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3answers
24k views

What can cause a Drain-Source short in a FET?

Background: I am using a Si7456CDP N-channel MOSFET in a switching power supply. The power supply and load are housed in a plastic enclosure. Yesterday, the power supply and load were working ...
3
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2answers
483 views

smps transformer capacitance effects

What are effects of interwinding capacitance in smps power transformer? What is the influence? For example, i have 83khz smps transformer with windings made of litz wire. The capacitance between ...
12
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4answers
4k 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....
6
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2answers
512 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 ...
5
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3answers
2k 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 ...
3
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2answers
6k views

ATX power supply front-end: How does this work?

I've been trying to educate myself on general power supply operation and stumbled across several schematics for ATX power supplies. In general I understand how a SMPS operates, and an ATX PS is just ...
2
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2answers
700 views

Digital SMPS Vs. Analog SMPS

There are several ways to implement the current/voltage control for an SMPS. The easy way I see is to use an ASIC/PMIC to manage the control loop. One of the other methods would be implement a PID ...
19
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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 ...
8
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2answers
16k 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 ...
7
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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?
3
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1answer
1k views

Flyback Transformer core heating up

I am designing a Discontinous conduction mode flyback converter, 100kHz using UC3844 IC with the spec. 220V,50Hz to 5V 5A. The issue is that after testing it for an hour, the transformer starts ...
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3answers
2k views

Coupling between hot ground and cold ground

When reading thru the power supply schematic of a sharp brand television, I noticed the link between the low voltage ground and the mains rectified DC ground. What is the purpose of this? Don't we ...
0
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2answers
16k views

SMPS schematic - transformer calculator

I found this schematic for a simple SMPS. I want to use it to build a 24V/2-3A power supply for a soldering station. How are the turns on the transformer calculated? For the primary I can use $$...
10
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2answers
1k views

Can connecting of AC adaptor first into device, then into mains pose a risk of voltage spike?

Manuals of several various electronic devices I came across recommend connecting their AC adaptor first into the device, then into mains. I always thought the reverse order is safer because I thought ...
9
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2answers
8k views

Power supply noise in audio

I have what is surely a classic problem with regard to power supply switching noise and audio but I am unable to sort myth from reality with regard to what I found so far on the topic. Setup: I have ...
5
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2answers
3k views

Relay not switching immediately from switching power supply to battery backup

WARNING This project as currently described is badly flawed in a number of ways that are liable to lead to complete failure of the equipment. As it is stated that it is intended to be used in a life ...
4
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2answers
1k 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 ...
3
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2answers
8k 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 ...
3
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3answers
6k views

What is the need for an inductor coil in a smps-buck converter?

Here is the figure: All tutorials have an inductor in smsp-buck. But when I simulate without an inductor I see a similar plot. Why not use only a capacitor?
3
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5answers
8k views

Can two ATX SMPS be connected in series to get +10 and +24V DC

Can two ATX SMPS be connected in series to get +10 and +24V DC (from 5V and 12DC output of each SMPS) Needing lots of current at 24V with atleast 5A so cannot use -5V or -12V inside SMPS as negative ...
2
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3answers
1k views

What is the advantage of a switching over a linear power supply?

I want to build my own switching power supply. I already know how to make a 10 Ampere Linear supply, and I'm wondering if I should bother. What do I have to learn to do a switching supply? What makes ...
2
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2answers
1k views

switching noise from ltc3780

I have currently built a buck-boost converter using LTC3780 on a breadboard following this deisgn. The circuit is calculated and designed to accommodate the input voltage given in the schematic. I ...
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1answer
3k views

alternative fix to: How can I calculate a Joule Thief

This is based on the original question: "How can I calculate a Joule Thief. How Can I calculate a Joule Thief. Since the gain of common emitter voltage amplifier and it will depend widely on the ...
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2answers
600 views

Switch between two power supplies

[![enter image description here][1]][1]I am trying to build a simple circuit to power a load with two different power supplies (5 V and 0.7 V). When one is active the other one is not and it's ...
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1answer
81 views

My circuit doesn't respond properly to the duty cycle [closed]

my circuit is shown on the picture. the problem is the output of the mosfet does't work as desired. For example, If I use Vin=100V and the duty cycle is 50%, the output is Vout=19V. Anyway, the ...
21
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6answers
26k 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 ...
16
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1answer
14k views

How important is self-resonant frequency for an inductor when used in a fast (~3MHz) buck SMPS?

I'm using the LM2734Z, a 3 MHz buck regulator. It's really fast which means it has a small inductor. One of the things I'm wondering is how important is the self-resonant frequency of the inductor? I'...
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 ...
16
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6answers
50k views

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 ...
8
votes
4answers
29k views

555 timer boost converter doesn't meet spec

I've been messing around with nixie tubes lately which requires a high voltage source (~150V-200V) to turn on. I searched around for a simple high voltage generator and found this circuit which uses ...