hybridfree/eevblog-posts huggingface dataset:
SMPS Blowing Input Fuse - Page 1
Forum section: electronics / projects

author: Christopher
author_rank: Frequent Contributor
timestamp: November 12, 2015, 07:09:49 pm
content: HeyJust a quick question.. I work with power supplies but not directly troubleshooting them on a daily basis so I know a fair bit about the design and theory of them but not too far into troubleshooting them, especially without schematics.We have a rackmount system with off the shelf modules. There are three modules in a rack. Each module supplies 28V at 90A with all modules in parallel with some clever current sharing/diode ORing. One of the modules went !bang! and its output showed 48V. All the other modules in the rack are now not working.One module had exploded (Panasonic brand) caps. No blown input fuse. All seems OK with this one now, I am replacing the caps.The other modules all exhibit the same fault, blown or high resistance input fuse (T20A). I have tried replacing this and the PSU acts like a short across the line, with slowly increasing current. The output caps seem fine.I am powering it with a 300V bench supply slowly ramping it up and it can take it up to about 50Vdc input before the supply goes into current limit.I am guessing the main switching fets are short, drawing a lot of current through the transformer... I can measure the DC voltage on the bulk input caps.Any suggestions?
SMPS controller ic identification - Page 1
Forum section: electronics / projects

author: Jeroen3
author_rank: Super Contributor
timestamp: October 08, 2025, 07:32:10 pm
content: I have bought a pre-order mini pc. Unfortunately, due to being pre-order, it isn't perfect.You can fit is with 6 m.2 drives, but it's 3.3V rail struggles.See attached scope shot of the 12V (blue) and 3.3V (yellow() rail.As expected, the m.2 disks don't like this.My theory is overheating of 3.3V rail power supply IC's or inductor.I have identified the 3.3V to be coming from the switcher state PL3, the 2R2 next to the Winbond, with it's two mosfets left of it.However, this seems controlled by the chip calledMPTL 2961 A622, and I can't identify that one.It is supplied by the 12V rail as measured on the cap on the board edge near PQ1.Does anyone recognize it?It's an Intel N150 motherboard if that helps.

author: wraper
author_rank: Unknown
timestamp: October 08, 2025, 08:08:52 pm
content: MP2961, IMHO try adding more bulk capacitance to its output.

author: Jeroen3
author_rank: Super Contributor
timestamp: October 09, 2025, 07:04:15 pm
content: This looks plausible, but the other inductor is also wired to this chip, I suspect it is two-channel.Your schematic also shows 3.3Vin, which is the rail this chip creates. That makes no sense.

author: wraper
author_rank: Unknown
timestamp: October 09, 2025, 07:13:23 pm
content: It makes no sense only for a total lack of attention. If you look on schematic, it has 2 outputs and multiple config pins, so probably can be used for two separate rails or have 2 power phases. But that's not even the issue as 2R2 inductor is obviously driven by MOSFETS controlled by something else. Not to say if you google MP2961, you'll find your chip on photos.

author: Jeroen3
author_rank: Super Contributor
timestamp: October 09, 2025, 07:14:46 pm
content: I think it's an intelli-phase form an MP2964 on the other end of the board.The topology looks similar, but these still have internal fets, what my board appears not to have for this channel.https://www.monolithicpower.com/en/documentview/productdocument/index/version/2/document_type/Datasheet/lang/en/sku/MP2965/document_id/5134/--Ah, you mean SW1 and SW2 can also be independent... yes that's a possibility.Compared to that schematic this board lacks a lot of caps...The other side does have two 220uF polymers, and the standby LDO, that's possible where the 3.3Vin comes from.

author: wraper
author_rank: Unknown
timestamp: October 09, 2025, 07:20:26 pm
content: I edited my post while you replied.

author: Jeroen3
author_rank: Super Contributor
timestamp: October 09, 2025, 07:22:29 pm
content: Me too, very effectiveAnyway, top side. Not that great quality, bad lighting when I took this.

author: Jeroen3
author_rank: Super Contributor
timestamp: October 15, 2025, 06:27:30 pm
content: Ok I've been working on it, the problem is not thermal, the 3V rail just browns out.This rail is absolutely not sufficient to power the 6 nvme ssds you can fit. Even in idle without os running the drop is already 200mV.Then when accessed it just falls off to 2.8V and stuff locks up.Well then, I bought a lemon.
SMPS design Help - Page 1
Forum section: electronics / projects

author: alah
author_rank: Contributor
timestamp: November 26, 2018, 07:18:16 pm
content: Hi ALL; I have a 19v / 2A power supply which is blown.Id like to use the filtered DC and the HF xfrmr to build one. I have VR 431 and foto transistors but I need a simple circuit for the feedback. Im googling SMPS circuits and though I understand the basics of SMPS, I need some help. Thanks, Alberto from Venezuela.

author: xavier60
author_rank: Super Contributor
timestamp: November 26, 2018, 10:50:03 pm
content: The UC3842 is a basic flyback controller IC. It is still commonly used in cheap SMPS from China. What it mainly lacks compared to modern IC is the power saving ability when lightly loaded, green mode.If you choose the UC3842, be certain to put a 10K resistor between Gate and Source as well as all of the other things that you simultaneously must get right.Tell us more about the existing design.Extra; assuming that is the original is the flyback type.

author: xavier60
author_rank: Super Contributor
timestamp: November 26, 2018, 11:11:27 pm
content: Also, do you have the equipment to do this project safely? Isolation transformer and Variac.You also must have an oscilloscope, not to have one is working blind.

author: alah
author_rank: Contributor
timestamp: November 30, 2018, 04:37:43 pm
content: Im working on a design ( not mine ). As soon as I have sufficient details Ill be back, Thanks.Oh, I dont have an oscilloscop and believe I never will.
SMPS filter cap choise - Page 1
Forum section: electronics / projects

author: ElectroWarrior
author_rank: Contributor
timestamp: October 19, 2013, 07:31:34 pm
content: Hey guys, it my first post on this forum!I am making a very simple buck converter to charge phones and such - the point behind the project is to make it as cheap as possible.There are some data on the project:- Converts 9VDC into 5VDC- Output current 500mA- Switching frequency 100kHz- RMS ripple current estimated to be 30mA- Max voltage ripple: 40mA- Max cap ESR 0.5OhmTo achieve the desired ripple i need a cap at minimum 33uF. I have been reading about filtercaps, and there is a lot of different advises out there. As I understand i only got aluminium electrolytic caps and tantalium to choose from.. I would prefer to use a aluminium due to the price, however i dont know how they respond at 100kHz frequency, and the further harmonics. Any advise or ideas?

author: ddavidebor
author_rank: Super Contributor
timestamp: October 19, 2013, 08:04:10 pm
content: They've a datasheet you can read

author: nctnico
author_rank: Super Contributor
timestamp: October 19, 2013, 08:19:04 pm
content: I'd recommend using SMT MLCC ceramic caps. 10uf is very affordable and results in a circuit which will last for a long time. A problem may be that the ESR of an MLCC ceramic cap is too low for the SMPS chip. Check the datasheet for information on which caps are recommend. I'd look into a different chip if it needs tantalum or electrolytic caps.

author: ElectroWarrior
author_rank: Contributor
timestamp: October 19, 2013, 10:03:12 pm
content: Thank you very much for the replies!Quote from: ddavidebor on October 19, 2013, 08:04:10 pmNot many datasheets on cheap electrolytic caps has much frequency information - or maybe i dont know how to read them right:)Regarding having multiple MLCC in parallel is a very good idea - Thank you! I looked into it, and it is actually quite cheap.I have never heard that buck controllers are filter cap ESR dependent.. could you possible elaborate?

author: Psi
author_rank: Super Contributor
timestamp: October 19, 2013, 11:24:44 pm
content: Quote from: nctnico on October 19, 2013, 08:19:04 pmHe can always add an external 0.1R resistor to the cap

author: Niklas
author_rank: Frequent Contributor
timestamp: October 20, 2013, 12:26:03 am
content: Check the datasheet of the Buck converter to see if there is some information about input and output capacitors. Some converters like more ESR on the output and some like less ESR. As Psi wrote, you can also add a series resistor to a low ESR capacitor to increase the amount of ESR that the Buck converter sees.If you go with ceramic capacitors, use X7R or something similar dielectrica. Y5V is not a good option.

author: ElectroWarrior
author_rank: Contributor
timestamp: October 20, 2013, 12:52:30 am
content: awesome! thank you.. I checked the datasheet, and there is no information about the ESR, however its also a very simple switcher.ill test it with and without a resistor.I choose a X5R, should be quite stable over 0-50 degree temperature range need:)Thanks for great advise!
smps hv spike problem - Page 1
Forum section: electronics / projects

author: 5282
author_rank: Regular Contributor
timestamp: July 11, 2018, 07:02:13 pm
content: i make some research on smps before i make on for 220v .so i powered my transistor with only 5v and reduce all component valuethe problem is in two things1- high voltage spike on transistor collector it's 50v and some time 30v and all this high voltage come from 5v suplly2- the high high frequency switching around 500khzhere is the oscilloscope screen shoot from transistor collector in attachment file

author: Miyuki
author_rank: Frequent Contributor
timestamp: July 11, 2018, 07:16:51 pm
content: "simple" 50 years agonow with integrated power controller like TNY and similar is no reason to experiment with self oscilating flyback it is beastwaveform look ok for this type of circuit maybe snubber is not tuned right or use bad componentsAnd how you probe it ? May be just ground lead induced noise

author: 5282
author_rank: Regular Contributor
timestamp: July 13, 2018, 10:34:44 am
content: thank you.i found the problem . i must to put load in the transformer output. to reduce the reverse voltage from transformer ..when i put the circuit in 220v the high reverse voltage kill the transistor. so i need load or feed back circuit

author: 5282
author_rank: Regular Contributor
timestamp: July 13, 2018, 10:43:05 am
content: here is my reverse voltage after i put load to transformer it's reduce from 50v to 12vpp. and i use good snubber circuit .the oscilloscope screen in attachment
SMPS improvement to reduce RFI - sanity check please - Page 1
Forum section: electronics / projects

author: de_light
author_rank: Regular Contributor
timestamp: February 23, 2021, 04:27:25 am
content: I bought a cheap Chinese SMPS (Mains to 12VDC,30A). Metal-cased. Intention is to use it to drive an amateur radio HF transceiver. Works okay for that purpose but puts out lots of HF RFI.I came across this interesting article on reducing RFI in SMPShttps://ka7oei.blogspot.com/2013/09/quieting-high-current-switching-power.html?m=1Scoping across the DC out + and - terminals, I could see an obvious 51Khz (presumably switching) signal and lots of ripple. Between chassis and DC - showed 1.56V p-p.Opening up the case showed some basic input EMI suppression: a class Y cap, class X and a single common-mode choke. On the output, there was a single 10nF (iirc) class Y cap connecting the DC - to earth/chassis ground.I pulled the three 3500uF output filtering caps (all which had dubious ESR) and replaced with a single 10,000uF 25V cap. I also soldered two 1uF 400V caps in parallel across the output class Y cap.This has essentially solved the problem. The switching noise between the chassis and DC negative is around 20mV peak to peak and the ripple is substantially reduced scoping across the DC output.My question is: how safe is this to do, bypassing the class Y cap? I'm on a 230VAC/50Hz mains supply. My (fairly beginners) thought process would be that if a fault were to develop (such as a power surge), the input side protection/transformer would fail before reaching my final output capacitor modification. Am I wrong?

author: T3sl4co1l
author_rank: Super Contributor
timestamp: February 23, 2021, 05:16:27 am
content: You've converted the output from, presumably fully isolated, to SELV only, i.e. no galvanic or surge voltage with respect to earth. If your applications are all ground referenced, this is not a problem.You wouldn't want to, for example, use it to power a mains-referenced project, just because it's handy.Tim

author: de_light
author_rank: Regular Contributor
timestamp: February 23, 2021, 05:20:45 am
content: Quote from: T3sl4co1l on February 23, 2021, 05:16:27 amI am looking to use this to power a single device, a Kenwood Ts590s transceiver which takes 13.6VDC either from a power supply or a battery.
SMPS Input Voltage Range - Page 1
Forum section: electronics / projects

author: washer
author_rank: Newbie
timestamp: June 09, 2012, 04:31:59 am
content: I've been looking through Ken Sherriff's great writeup on his iPhone charger teardown down -http://www.arcfn.com/2012/05/apple-iphone-charger-teardown-quality.htmlI've got a requirement for a wide range power supply in a project I'm working on with inputs ranging from 120V mains up to 277V rms mains (one leg of a three phase line). I'm new to SMPS and thought I could use the iPhone design as a jumping point. The load is pretty similar, I only need a 3.3V rail with no more than 2A.My big question right now is what determines the input voltage range for this topology? Is it the voltage of the power MOSFET? The flyback transformer?I've been looking through the datasheet for the L6565 controller and some of the app ckts in there as well -http://www.st.com/internet/com/TECHNICAL_RESOURCES/TECHNICAL_LITERATURE/DATASHEET/CD00002330.pdf.Those two circuits are 40W and 50W supplies, when I'm looking more around 5W, but they've been illustrative while I've been trying to dive in.So for a ~5W load and a 477V 3-phase, 4-wire source, what do I need to focus on changing? Am I on the right track?Thanks for any help!

author: johnmx
author_rank: Frequent Contributor
timestamp: June 09, 2012, 12:13:11 pm
content: That circuit is a flyback converter. The maximum input voltage depends mainly of the MOSFET breakdown voltage but also the minimum duty cycle.In this case, the maximum voltage applied to the main switching MOSFET is: input voltage + voltage across snubber circuit + leakage spike voltage due to leakage stored energy in the transformer core.
smps intermediate voltage or not? - Page 1
Forum section: electronics / projects

author: kars
author_rank: Contributor
timestamp: September 18, 2019, 09:43:53 am
content: hi all,For a project im working on an AC/DC SMPS.Quick specs:in: 230V AC 50HZout: 50VDC, ≈1A, 5VDC ≈10A, 3.3VDC ≈0.5Aive been concidering the following options: flyback converter with 3 transformer outputs for the voltages OR a flyback converter outputting an intermediate voltage (50V) and using a buck converter to generate the 5V rail.I do realize the latter one would lower the efficiency of the supply. the thing is im not shure if there are suitable transformers availible for the first optionWich of these options would you guys/girls/whatever reccomend? Do you have other suggestions?Thanks in advance!Kars

author: richard.cs
author_rank: Super Contributor
timestamp: September 18, 2019, 10:05:47 am
content: It depends a lot on the regulation accuracy required and the load variability. Multi-winding flyback converters normally have one well-regulated winding and the others loosely regulated. You could for example design it for a well regulated 5 V output, a loosely regulated 50 V, and then use a small buck converter to generate the 3.3 V from the 5 V.Another topology to consider, and which gives you all windings fully regulated, is a flyback outputting 50 V and a lower voltage, say 8 V, with the 50 V output being the regulated one. You then use buck converters for the low voltage supplies but only with a low voltage ratio which tends to allow higher efficiency. For the 5 V 10 A supply you will probably also want active rectification.

author: kars
author_rank: Contributor
timestamp: September 18, 2019, 10:25:26 am
content: Quote from: richard.cs on September 18, 2019, 10:05:47 amAh, now that suggestion of a piece of software makes sense! it indeed suggested a feedback block on only one of the windings.Quote from: richard.cs on September 18, 2019, 10:05:47 ami think im gonna go for this solution actually, that 5V winding needs better regulation than the 50V one. perfect!Thanks!

author: richard.cs
author_rank: Super Contributor
timestamp: September 18, 2019, 10:50:45 am
content: Quote from: kars on September 18, 2019, 10:25:26 amYou can take feedback from one winding or several (one only is common) but because the controller has only one control axis (total power into the transformer) controlling from multiple windings makes the regulation on all of them somewhat poor rather than one very good one and the others bad. The total error is the same (caused by varying load-related voltage drops in the different windings and rectifiers so they don't stay perfectly ratiometric) you just change how it is distributed. You can also introduce interesting stability problems if you take feedback from several windings or from a single winding which is lightly loaded compared with the others.
SMPS + linear supply interference - Page 1
Forum section: electronics / projects

author: lukasz.kostka
author_rank: Contributor
timestamp: May 08, 2020, 06:53:46 pm
content: Hi.I am working on a digital dummy load with DAC/ADC and a MCU. I'd like to use my radial 12V fan from an old server which takes up to 2,5 A peak. Linear regulators won't make it so I am left only with SMPS regulator. I am thinking about to leave only 12V for fan to reduce noise on linear / analog part. Does it make any sense ? Maybe I need to take car of something else ? I've never designed any SMPS regulator circuit before.
Smps load shut down  - Page 1
Forum section: electronics / projects

author: davelectronic
author_rank: Frequent Contributor
timestamp: March 10, 2019, 11:43:28 am
content: I'm trying to see if I can find a solution for a converted dell psu that shuts down with anything beyond a 50 watt halogen lamp load. This is the dell power brick that was originally powering the dell optiplex usff 745 / 760.It's rated at 12 Volts 18 Amps, I've loaded it up with 50 watt lamp load and it's fine. But adding a second lamp, and it won't stay on, rather shutting down. I don't have a modest to large inductive load to try that, incase it was a resistive only issue. I think it might be seeing the higher resistive load as a short in the output.What's thoughts on this , any ideas appreciated. If it is seeing that 100 watt load as a short, what might be a likely solution ? Would some kind of soft start remedy this problem, or maybe something in the power supplys feedback circuit. After looking at the under side of the pcb, reverse engineering this psu is probably beyond my ability. Just a way to add load and keep it running would be great. I've got remote and sense wires connected right at the load connection. And have tried removing sense feedback wire, but it makes no difference. I did think it might be adding the second lamp suddenly was the problem, but even connected from the start it won't power that 100 watt resistive load.Thoughts appreciated and thanks for reading.Ps. I have converted server power supplys over the years, and none shut down with 100 watt load. And I've even got up to 500 watts running fine on converted server power supplys. Just at a loss why this 12 Volt 18 Amp shuts down at 100 watts load, but happily runs a 50 watt load.

author: MagicSmoker
author_rank: Super Contributor
timestamp: March 10, 2019, 12:20:28 pm
content: Halogen lamps - any incandescent lamp, actually - have a much lower resistance when cold. Something like a 16:1 change from 25C to the normal operating temp (2500C?).

author: davelectronic
author_rank: Frequent Contributor
timestamp: March 10, 2019, 01:52:51 pm
content: So the cold incandescent halogen lamp is seen by the smps as a short circuit in the output stage ? Any ideas how to get round this, with this type of load ? Or maybe there isn't a way with this supply in particular.

author: MagicSmoker
author_rank: Super Contributor
timestamp: March 10, 2019, 07:25:23 pm
content: The best solution is to modify the smps feedback loop so it operates in constant current mode when overloaded. Most cheap/commodity switchers go into hiccup mode when overloaded and these can have a tough time with incandescent lamps.A next-best solution - more in the class of kludge - is to lengthen the soft-start time (usually only requires increasing a capacitor value) and make sure the lamp is connected to the smps before turning it on. You'll likely need a soft-start time in the range of 100-500ms.Third-best - and really kludgey - is to put a fixed resistance in series with the lamp during startup then short it out with a relay or SCR or whatever after the filament heats to at least a dull red.
SMPS Output Capacitor Selection For Ripple Current (SEPIC) - Page 1
Forum section: electronics / projects

author: alexturner
author_rank: Contributor
timestamp: August 01, 2021, 02:42:57 am
content: I'm designing a SEPIC converter based on a wide input voltage range SMPS controller (LTC3758). The requirement is for a wide input voltage (10-60V) with a fixed output of 28V @ 1.5A. I'm trying to determine Cout selection which per the data sheet, is the same for a SEPIC converter as it is a Boost converter.The equation for ripple current across the output capacitor is the square root of the ratio of the max duty cycle multiplied by output current. However the max duty cycle is a factor of voltage only and doesn't consider frequency or capacitance.This current calc yields an output ripple of 2.4A which is challenging to achieve with SMD capacitors and doesn't seem correct. How does one best determine the output capacitors for a SEPIC circuit as such and what is the effect of increased capacitance and frequency on this selection (if any)? Surely the derivative would be a better determination here, is this just a bad datasheet?

author: T3sl4co1l
author_rank: Super Contributor
timestamp: August 01, 2021, 02:37:15 pm
content: Show the equation.Was F, C, etc. not factored out in a previous step?Tim
smps output circuitry design - Page 1
Forum section: electronics / projects

author: jackbob
author_rank: Regular Contributor
timestamp: September 10, 2012, 03:58:47 am
content: Hey guys, so about a week or so ago i made a post about components in smps output circuitry. Anyways after a bit of time this is a circuit I designed for a smps I plan to build. I would like feedback on what you think, if it looks good and if there are any components or values that seem they could be improved. some notes....(1) the transformer is actually a single transformer but i had to add two to get a single transformer with center taps on each side (2)U1 should be labeled Q2 (3) there is no driver for the mosfets in this schematic but the tl494 outputs will be connected to the diode and resistor at the gate of each FET (4)C 2,3,4,5 are snubber caps and their values may not be appropriate. (5) the output is isolated but uses common grounds with the inputs in the schematic for simplicity. (6) the output is about +-60vdc to ground and is stored in C16, 17, 18, 19. Sorry for the poorly drawn schematic I just copied what i had on paper in 15 minutes. A .png image of the schematic is attached. Again this is only the output circuitry no drivers. Thank you all for your input.
SMPS over current protection - Page 1
Forum section: electronics / projects

author: mirokamh
author_rank: Newbie
timestamp: February 18, 2017, 12:28:58 pm
content: Hello.I am building a power supply for my school project. It's 80V 10A supply, with TL494 and two-switch forward topology. It has 2 types of current regulation. First is just sensing a voltage drop at shunt resistor, this works great. It's set to 10A. But second one is sensing current by using small current toroidal transformer placed on primary winding of power transformer. Then, it controlls MOSFET Q11 placed at output of supply, and in case of short, it should ground Gate of Q11 through Q10 and close it. This is just spike current protection, and it's set to 13A. But my problem is, that in case of short at the optput, Q11 don't close quickly enough and current from output capacitors just destroys it. So my question is: is there any MOSFET that is capable of handling this voltage and current which can close quicker? Or is this just bad designed circuit?Schematic is in attachment. Thank you for replies

author: NiHaoMike
author_rank: Super Contributor
timestamp: February 18, 2017, 07:00:21 pm
content: Change R49 to 10 ohms or so and change Q14 to a small SCR. You'll also have to find a way to have the SCR disable the switcher, resetting when the secondary capacitors have discharged.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: February 18, 2017, 08:18:16 pm
content: More the current sense shunt earlier, so it senses the inductor current (or the ground return current through the diode and secondary).Close the TL494 loop on this only. Tie off the unused TL494 error amp.Add an external op-amp, and close its loop around output voltage.This is a small change, subtle even, but it does revolutionary things for the stability, and safety, of the circuit!Remove the IRFP150 output current regulator. It'll blow up some day, and then stop working anyway.Tim

author: NiHaoMike
author_rank: Super Contributor
timestamp: February 18, 2017, 09:56:32 pm
content: I think the intent of the output MOSFET is to protect the load from the output caps if something goes wrong. E.g. the PSU is used to power prototype hardware.

author: mirokamh
author_rank: Newbie
timestamp: February 19, 2017, 09:14:54 am
content: That's right, idea was that mosfet will close qucker than output capacitors discharge. I can try to use SCR with small gate resistor. Thanks for advices
SMPS Problems going from Low-side to High-side current sensing - Page 1
Forum section: electronics / projects

author: kilowatt21
author_rank: Newbie
timestamp: February 21, 2017, 07:08:41 pm
content: Hi everyone,i'm making a smps with CV/CC 0.1-20V (0.1-5A @ 0.1-10V) (0.1-2.5A @ 10-20V) (don't want to overload it because i need passive cooling).all op amps are lm321(could they be to slow?).i designed the prototype board and started working on it, all went well with cv part. Power supply goes from 0.1 to 20V with resistive loads at even higher currents then needed so i know that the main switcher chip (LMR14050) is capable. To clean up the output ripple i added a filter for op amp supply rail, increased main input capacitence, added more ceramic capacitors to the output and it all seem to be great with CV.when i started to work on CC part of control it didn't go so well.. after going thru a bunch of different current shunt monitors (ina214, ina193, max4376...) on the high side o found that when i tried to measure current on a low side (with 10k pull-up to 5V at sense line for lower current stability), it worked just fine. Current control goes down to 100mA no problem at any voltage (once i removed both 1000uF caps of the output).When i tried to control in CC mode the current would change depending on output voltage (set at 1A, read 0.8A@15V, 3A@2V), i read about common mode voltage, but i don't think that's the problem, i think something is wrong in my control loop.At low currents it would go into huge oscillation (5 Vpp at just a few hertz).i sat around this board for around three weeks, would use a help by now.. thanks for any suggestions and sorry for my English.

author: MagicSmoker
author_rank: Super Contributor
timestamp: February 21, 2017, 10:40:25 pm
content: This is almost certainly the result of a common mode range violation. In high side current sensing both inputs of the op-amp have to operate near the positive rail so Vcc needs to be higher than that voltage unless the common mode input range includes Vcc (or Vdd, if a FET amplifier).
SMPS problems - Page 1
Forum section: electronics / projects

author: 5321488
author_rank: Contributor
timestamp: October 18, 2017, 06:24:23 am
content: Hi everyone,I built an SMPS from an article I found online, schematic attached (the one Dave used for his nixie sub counter,https://threeneurons.wordpress.com/nixie-power-supply/hv-supply-kit/). I'm not getting the desired output voltage at all, and Q2 and L1 are becoming very hot. I've checked and checked and checked the circuit and it seems fine, and Q2 is still testing ok. I added a resistor in series with L1 but while it solved the heat it didn't produce any decent output voltage.If someone was able to have a look and spot any issues I'd really appreciate it.

author: Circlotron
author_rank: Super Contributor
timestamp: October 18, 2017, 06:37:16 am
content: The IRF630 looks like it is drawn upside down. Big problems if it is actually connected this way.

author: tautech
author_rank: Super Contributor
timestamp: October 18, 2017, 06:40:39 am
content: https://www.onsemi.com/pub/Collateral/MC34063A-D.PDFLook where the inductor is on P8.

author: Circlotron
author_rank: Super Contributor
timestamp: October 18, 2017, 06:53:31 am
content: No, the OPs cct is basically the same as the one in fig 9.

author: eblc1388
author_rank: Frequent Contributor
timestamp: October 18, 2017, 07:10:40 am
content: The connection of the IRF630 is wrong in the original circuit. See the correct one below.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: October 18, 2017, 07:14:57 am
content: Holey moley, a TIFF disguised as a JPG!Fixed:Yeah, that's upside-down. Note the diode (which is redundant, because note the arrow into the MOSFET junction indicating the body diode too!) shorting the inductor to GND.Q1 is backwards, too.Tim

author: eblc1388
author_rank: Frequent Contributor
timestamp: October 18, 2017, 07:33:48 am
content: Good catch on Q1, missed that.

author: 5321488
author_rank: Contributor
timestamp: October 18, 2017, 07:36:17 am
content: Ah thanks so much!! Just switched both, Q2 and L1 are working perfectly, but Q1 is now hot after switching it around. I would agree now that it seems backwards, but should I switch it back?EDIT: forget that, its actually D1 now super hot. Any ideas?

author: eblc1388
author_rank: Frequent Contributor
timestamp: October 18, 2017, 08:07:07 am
content: You can try place in series a 22 ohm resistor between the cathode of 1N914 and the emitter of MPSA55.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: October 18, 2017, 09:04:00 am
content: Might be worth checking if you've shorted any components at this point. Check the transistors, diode, controller sure why not?Tim
SMPS PWM VS SELF OSCILLATION - Page 1
Forum section: electronics / projects

author: 5282
author_rank: Regular Contributor
timestamp: July 14, 2018, 06:53:33 pm
content: HELLOWHAT IS THE DIFFERENT BETWEEN USING PWM IC CHIP IN SMPS LIKE UC3842 OR USING SMPS SINGLE TRANSISTOR SELF OSCILLATION FEEDBACK CIRCUIT.

author: 5282
author_rank: Regular Contributor
timestamp: July 14, 2018, 07:44:39 pm
content: WHYYY?

author: Miyuki
author_rank: Frequent Contributor
timestamp: July 14, 2018, 07:52:13 pm
content: We are almost 20 years in 21st centry
SMPS recommendation: 18-32Vin, Isolated 6Vout at 1A.......... - Page 1
Forum section: electronics / projects

author: Smokey
author_rank: Super Contributor
timestamp: December 29, 2022, 02:18:44 am
content: All of my go-to parts for something like this are out of stock everywhere. Fun.Either I can't get the chips, or I can't get the magnetics (or I'm just a terrible designer, which can also be true).Main target goal here is low BOM cost, since I need a few of these per system (like around 36)...Rough spec, as stated in topic:18-32VDC InputIsolated 6V out at 1A maxForward or Flyback, I don't care much. It's going to be post regulated (constant current) and used to charge a battery cell, so regulation and ripple requirements are pretty relaxed.Preferably off the shelf transformer.I was looking at something out of the box like a power-over-ethernet converter, since those parts appear to be more in stock. But I don't want to pay for PoE features I'm most certainly not using if there are other less expensive options.In these crappy smps shortage times, what would you guys do for something like this, especially for an inexpensive solution with off the shelf magnetics?

author: Martinn
author_rank: Frequent Contributor
timestamp: December 29, 2022, 09:05:43 pm
content: Not sure... did you check LCSC? Their search is terrible, buthttps://www.lcsc.com/products/DC-DC-Converters_484.html?keyword=flybackThis onehttps://www.lcsc.com/product-detail/DC-DC-Converters_XLSEMI-XL6008E1_C73012.htmlas flyback with a POE transformer and optocoupler/TL431 feedback?POE transformer example:https://www.lcsc.com/product-detail/Power-Transformer_HANRUN-Zhongshan-HanRun-Elec-HR051067_C93830.html- Martin
SMPS Replacement - Page 1
Forum section: electronics / projects

author: Poroit
author_rank: Frequent Contributor
timestamp: November 03, 2024, 05:10:47 am
content: G'day Members,For the past 10 years I have been repairing 25 year old SMPS from Aircraft Test Sets.They can be a mongrel at times due to their mechanical assembly.(PFC and PWM mounted on Vertical Daughter Board)Has anyone come across a more recent SMPS that could possibly be retrofitted?ADTS 405 Power Requirement.InputSingle phase AC in the range 90-260 VFrequency range 47-440 HzDC power option ..24 to 30 VADTS 405F ..500 VAOutputs5V DC @ 1A24V DC @ 3A+/- 15V DC @ 1AComparator Output 5V DC
Smps ripple current definition - Page 1
Forum section: electronics / projects

author: sahko123
author_rank: Frequent Contributor
timestamp: April 09, 2022, 09:55:14 pm
content: I'm currently designing a 120ish watt smps for which I a tiny transformer (only for a micro and the smps controller) in calculating the inductor value I need the ripple current through it.Would the ripple current be defined as the largest peak to peak current draw of the power supply, roughly 5amps pk to pk for a 24v output for a 340vdc input, since the load is a pwm controlled soldering iron (jbc t245). So do I take 5amps as the pk to pk ripple current through the inductor?

author: Terry Bites
author_rank: Super Contributor
timestamp: April 11, 2022, 05:36:06 pm
content: See this handy App note from TIhttps://www.ti.com/lit/pdf/slva477?keyMatch=BASIC%20CALCULATION%20OF%20A%20BUCK%20CONVERTERS%20POWER%20STAGE

author: bson
author_rank: Unknown
timestamp: April 11, 2022, 06:44:17 pm
content: It's the standard deviation.

author: TimFox
author_rank: Super Contributor
timestamp: April 11, 2022, 07:22:08 pm
content: Otherwise known as the rms value of the varying component.
SMPS Single PWM output translation into separate MOSFET gate outs - Page 1
Forum section: electronics / projects

author: Jovan1
author_rank: Newbie
timestamp: May 03, 2022, 01:37:59 pm
content: Well hello, ive come about an interesting problem and a solution to it (i hope), im utilizing an SMPS buck controller which does not have separate top and bottom gate outs, rather it has a single PWM out. The idea is to hook the PWM up to a power stage with integrated mosfets, where +5V HIGH on PWM represents TG=on BG=off, 0V LOW on PWM represents TG=off BG=on. Now, the power stages i could use with a single PWM input are either too expensive or unavailable, so i decided on a power stage with TG and BG inputs, basically two MOSFETS in one package. Now, of course i cannot hook up PWM to both TG and BG, this would result in both TG and BG turnign on when only TG should. What I have devised to get around this problem is a circuit which firstly inverts PWM so that where 0V LOW on original pwm represents BG on, on inverted PWM BG on is represented as +5V HIGH, this line goes straight to BG. The inverted PWM line hooks up to another inverter referenced to SW instead of GND, this inverter inverts the inverted PWM so that it is the same as on the output of the controller, difference being that LOW is not GND, but SW, this line ges straight into TG. I have attached the schematic of the described circuit to this post, i hope that some knowledgeable people will point out flaws and errors in this circuit and/or suggest how to improve and/or simplify it. Thanks very much for reading

author: T3sl4co1l
author_rank: Super Contributor
timestamp: May 03, 2022, 02:00:35 pm
content: Heh no, not quite like that. There are a couple things missing:- Dual transistor inverters have enormous shoot-through- High side +V needs to be bootstrapped to source, not fixed(!)- No delay (output shoot-through prevention), UVLO, etc. protection shownJust get a gate driver chip with complementary outputs, e.g.https://www.ti.com/lit/ds/symlink/tps28225.pdfTim

author: Jovan1
author_rank: Newbie
timestamp: May 03, 2022, 03:28:13 pm
content: Oh, well thats convenient, didnt know those existed. Yeah, i thought the delay might be a problem and possibly short out everything by turning on both MOSFETS on for a split second, forgot about the bootstrap cap, oops. Thanks for your help
SMPS start up problem  - Page 1
Forum section: electronics / projects

author: whatty
author_rank: Contributor
timestamp: March 22, 2023, 09:17:21 am
content: Hi,Hi i have attached the schematic as shown in schematic i have connected all components in bread board.What issue i have faced: When R5 start-up resistor was 18k the controller starts up and there was output at the secondary but the resistor R5 heats up after some time it was burned. The measured voltage across vcc of IC is 8.4v above which the voltage doesn't goes upThen i changed the resistor R5 to 100K but there was no output at the secondary and measured the voltage across vcc of ic it was 4v above that it was not going.After i took out startup resistor and ran it under external lab bench power supply the output and everything works well there is no output voltage across auxiliary does this is due to improper flux linkage between primary and auxiliary....?I measured the leakage inductance between primary and tie all secondary and auxiliary together it was 130uh primary inductance is 840uh so this gives a coupling factor of 0.92 .I have given image of winding order which is done in transformer.I have attached both the image and schematic pdf.(Previously i had started a thread start-up resistor yes it was me please pardon me i didn't find any response hence started new)

author: Eraldo
author_rank: Regular Contributor
timestamp: March 24, 2023, 07:48:35 am
content: First of all what is the output voltage of the transformer since assuming it is 30v the power dissipation would be only 0.05wNext can you check the current consumption of the ic when connectet to the bench psu? From the datasheet of the ic, it is capable of outputting a max of 1 amp and with a 18k resistor it would never come even close to that (again assuming the 30v transformer it would be less than 2 mA)In this case i would try to use a 12v (or 9) linear regulator. Higher current capabilities and more stable voltages.Also just in case, check that C3 in case it's making a short circuit.Good luck

author: capacitor_explosion
author_rank: Contributor
timestamp: August 07, 2023, 12:25:33 pm
content: Hello Whatty , I think your issue lies in the fact that LT1246-7 has a very specific Start up threshold voltage which I don't think you have accounted for . Even if you have choosen the correct resistor (R5 should be above 100Ohms 10W ) the device starts , you need to design the auxiliary winding to be above the minimum operating voltage stated in the datasheet (is not the same as UVLO) .Let us know the progress .Simo
SMPS surge rating and X caps - Page 1
Forum section: electronics / projects

author: blueskull
author_rank: Unknown
timestamp: April 03, 2017, 06:56:48 am
content: Does all SMPS input caps have to be X1/X2 rated? Can I just use a regular cap to do the trick?I mean, anyway if a surge comes, the MOV will blow up first, so what's the point of mandating a 4kV tested cap in parallel with a 400V MOV?I am talking about X caps, not Y caps. There is no shock hazard. I am also talking about after fuse, not before fuse.Also, I'm talking about moisture guarded film caps, not MLCCs, so don't worry about vibration/deflection/stress/cracking/delamination.

author: wraper
author_rank: Unknown
timestamp: April 03, 2017, 08:01:20 am
content: Quote from: blueskull on April 03, 2017, 06:56:48 amThere is explosion and fire hazard, yes they must be X rated. X caps are not 4kV tested.First search result, 1.3kV test, Continuous DC voltage* (general guide): 630 Vhttp://www.wima.com/EN/WIMA_MP_3-X2.pdf

author: David Hess
author_rank: Super Contributor
timestamp: April 03, 2017, 11:07:15 am
content: It is more of a safety issue; X and Y rated capacitors are required for line side applications. Both have to fail without starting a fire and Y capacitors have to fail open to prevent shorts to ground.Before X and Y rated capacitors were available, suitably derated paper, plastic, and ceramic capacitors were used.

author: wraper
author_rank: Unknown
timestamp: April 03, 2017, 11:09:46 am
content: Quote from: blueskull on April 03, 2017, 08:35:43 amOvervoltage is not required to cause explosion or fire.

author: madires
author_rank: Super Contributor
timestamp: April 03, 2017, 11:47:17 am
content: Quote from: wraper on April 03, 2017, 08:01:20 amEach class has to withstand a specific impulse voltage. For X2 it's 2.5kV. Here we go:https://www.illinoiscapacitor.com/pdf/Papers/EMI_RFI_suppression_capacitors.pdf.

author: Gyro
author_rank: Super Contributor
timestamp: April 03, 2017, 02:11:12 pm
content: MOVs are known limited life components - they will degrade with time and are not guaranteed to protect against all shapes and energies of spike / surge waveforms. X and Y caps are also designed to provide the required safety characteristicsthroughout life.The question must be academic anyway - the use of non safety rated capacitors in locations that require them is simplyNot allowed. As a product designer, you could end up going to jail if the worst happened through deliberate negligence.Safety! is the message that should come from this thread.
SMPS Thermal sensor position - Page 1
Forum section: electronics / projects

author: innkeeper
author_rank: Unknown
timestamp: May 25, 2020, 08:51:50 pm
content: I have a Meanwell style Chinese power supply that has a thermal switch to control the fan.Thing is, the thermal switch is just tucked into the output inductor.Meanwell themselves seem to have their sensor on the pcb and using some kind of solid sliastic type material to 'glue' it to the inductor. (not a thermal epoxy, it is just that hard type silastic compound)This particular supply seems well put together, and not your typical cheap Chinese supply, even using quality caps... so this was the one thing that seemed, odd.Is this the right place to put such a thermal switch. or would it be better mounted to the case?Is this typical? I am used to seeing thermal switches or sensors on the heat sink. though the heat sink here would be the case itself.

author: uer166
author_rank: Super Contributor
timestamp: May 25, 2020, 10:42:19 pm
content: If the inductor happens to be the hottest part, then surely this is the best possible location of the thermistor? If the FETs are the hottest, then best place would be on-PCB for SMD FETs or heatsink if they're TO-220. This seems like a great quality supply, at least visually, and the fact that they spent extra effort to thermally protect the inductor is great.

author: TimNJ
author_rank: Super Contributor
timestamp: May 26, 2020, 04:04:44 pm
content: Probably don't need to add anything more to uer166's response, but in general, the magnetic components are often the most stressed components on a power supply. Of course, it really depends. For some power supplies with very limited space, there is no option but to use a smaller core size and let the inductors/transformer run hot. In this case, space doesn't seem to be so much of an issue, but still may be the case.
SMPS topology? - Page 1
Forum section: electronics / projects

author: Colt45
author_rank: Contributor
timestamp: July 15, 2022, 06:25:39 am
content: I'm not all that familiar with non-flyback isolated SMPSes. This is the "A40 preregulator" (24V offline converter) from a piece of HP test equipment. Looking around it seems similar to a forward converter, but I don't see any with the big fat toroid from one transformer leg to ground.quickly traced, partial schematic:I don't really see how this works, I don't believe I made an error tracing it.The big toroid is completely roasted to a crisp. With no load it doesn't seem to heat up fast/much, with 4A load it is >150C in tens of seconds, with full system load it is hiccuping.

author: Wolfram
author_rank: Frequent Contributor
timestamp: July 15, 2022, 10:34:36 am
content: It looks like it's related to a current doubling rectifier. Only one end of the transformer is connected to ground through the inductor, but as long as the ripple current in the output inductor is significantly smaller than the load current, this should not lead to too much asymmetry in the current waveform.
SMPS Transformer Failure - Page 1
Forum section: electronics / projects

author: b2theory
author_rank: Contributor
timestamp: January 06, 2017, 12:17:27 am
content: Any thoughts on the mechanism that would cause the primary inductance of a ferrite core (E core) transformer to drop from 1mH to roughly 50uH?

author: Zero999
author_rank: Super Contributor
timestamp: January 06, 2017, 12:23:27 am
content: A shorted turn, either on the primary or secondary winding.

author: b2theory
author_rank: Contributor
timestamp: January 06, 2017, 12:35:45 am
content: Quote from: Hero999 on January 06, 2017, 12:23:27 amBoth the primary and secondary have lost equivalent inductance.

author: drussell
author_rank: Super Contributor
timestamp: January 06, 2017, 02:52:58 am
content: Quote from: b2theory on January 06, 2017, 12:35:45 amWell, obviously...It is a transformer... The primary and the secondary can "see" each other...

author: Zero999
author_rank: Super Contributor
timestamp: January 06, 2017, 09:11:59 pm
content: Unfortunately, there's no way of telling whether the shorted turn is on the primary or secondary winding. If you know the DC resistance of the windings of a good transformer, of the same type, then you'll stand a chance: the resistance will drop due to a shorted turn, but otherwise you're out of luck.

author: xavier60
author_rank: Super Contributor
timestamp: January 07, 2017, 06:28:40 am
content: The primary winding can be damaged by high fault current caused by switching transistor failure in mains powered SMPSs. I suspect that high temperature melts the enamel coating on the wire.
SMPS Transformer - Page 1
Forum section: electronics / projects

author: safarir
author_rank: Regular Contributor
timestamp: June 28, 2010, 12:08:38 am
content: Hi everyone,I plan on building a simple and small off-line power supply using the NCP101X serie of chip. A read a lot of app note but I am stock at the transformer.I know exactly the specification of the transformer I need but I can't figure out where to find one/how to build one. I know nearly nothing about transformer and I am looking for great ressource about the subject.Thanks a lot

author: saturation
author_rank: Super Contributor
timestamp: June 28, 2010, 10:47:29 am
content: http://www.falco.com/products/1/smps.asp

author: safarir
author_rank: Regular Contributor
timestamp: June 28, 2010, 12:41:57 pm
content: Thanks a lot Saturation, that a very good start

author: Pyr0Beast
author_rank: Contributor
timestamp: July 01, 2010, 08:32:42 pm
content: Voltage and current, primary and secondary, working frequency ?You can easily steal one from a dead PSU and rewind it for a start.

author: safarir
author_rank: Regular Contributor
timestamp: July 01, 2010, 08:56:26 pm
content: I just find a exellent application note:http://www.irf.com/technical-info/appnotes/an-1024.pdf

author: Scutarius
author_rank: Regular Contributor
timestamp: July 06, 2010, 04:53:09 pm
content: I will recommend you PI expert software