Search for SMPS in Topics

SMPS formulas?

Are there any switched mode power supply formulas? I've been googling but I can't find anything... I need to know relation between duty cycle (I'm using square waves) frequency size (value) of the inductor output voltage output amperage how many amps should the inductor be rated for (is it how much your drawing?)

Topic by guyfrom7up    |  last reply

smps is sparking?

When i switch the computer system the smps is sparking

Question by smanics    |  last reply

can i convert 220v dc to 9v dc.....such that 9v is the power supply of 555 timer.....

No other  supply is given only 220v dc is given....current can 50mA

Question by aruntheaspire    |  last reply


Hello, i just started learning how a center tapped transformers/smps works and i did some test but now i am confused about the dual power distribution, i mean if a device input power rating is a centered tapped, say +12_0_-12 VDC, when we measure the +12 and -12 the voltage is 24VDC but we can't use the 24VDC on a single 12v:0v device it short circuits the transformer/smps. When we measure the +12 and the GND the voltage is 12VDC and we can even use the +12v:GND with a single 12VDC device, so my question is, does the center tapped device actually uses the 24VDC or the device splits the 24VDC into 12VDC/12VDC. Thank you. Sorry for my beautiful English, there is nothing to admire nu(:

Question by Lima79    |  last reply

SMPS H-Bridge trouble

Hi,  I've built a 1kW SMPS designed to take a 350V unsmoothed DC input and convert it to 3kV @ 300mA. The circuit is basically Uzzors2k's design seen here minus the overcurrent protection and smoothing capacitor (for now), however I accidentally wired the GDT outputs backwards so the gate resistors (33ohm 2W) are on the source. I have used alternate MOSFETs the latest attempt with FDPF16N50T's. I've had various problems with the circuit, primarily the MOSFET's exploding seemingly from overvoltage (evidence of flashover in some cases despite no evidence of secondary leakage (i dismantled the transformer to check)). During my last test I had a flashover between the drain and source pins of one of the FET's, in addition all of the gate resistors were smoking hot after, seems the gates had all been shorted (first time this happened, other occurrences were from case to ground). This happened despite the variac only being turned up to 40% which should be well well below the pin spacings maximum voltage tolerance. I have checked the drive signals, they are quite nice square waves at about +-15V with some oscillation on their rise. I have built SMPS's before, one is currently working with similar MOSFETs using a half bridge at 300W. Does anyone have any suggestions as to why these troubles are occurring or have any suggestions to fix it or have any alternative circuits that may be less troublesome (is a h-bridge easier to manage?)? Thanks, Stephen I​ just gave it another test with a H-bridge instead and the source of one of the FET's blew so it appears that there is just FET failure and maybe not arcing between drain and source.

Question by The MadScientist    |  last reply

SMPS failure, the Gates of the MOSFETs exploded?????? Answered

I've just build an SMPS using a TL494 chip using the power circuit from this circuit from uzzors2k, it's just a standard half bridge in my case using IRFP460's. The MOSFETs are driven through a small transformer that itself is driven with a H-bridge.  Yesterday I was trying it's first mains power test slowly ramping up the voltage with a variac when at about 180VAC i could hear some fizzling from the circuit and at 200V the GATE's of the MOSFET's exploded violently, at close inspection there was no shorts or flashovers and the gates were the only thing that was damaged at all. One thing i noticed later was the output waveform of the power transformer, unlike the signal waveform it didnt exhibit the same 96% duty cycle but a 100% with a lot of ringing on the rising peaks of the square wave, i know this can probably be fixed by reducing the duty cycle but i cant see how it could've blew up the gates. I've included some pictures so you can see what i mean by explode, as you can see on the left Fet the gate pin has completely blown off and the copper has melted slightly and the right image the same happened but i cracked the Fet open with a hammer to see if there were any clues inside. I really dont have a clue why this happened and would appreciate some help, thanks in advance.

Question by The MadScientist    |  last reply

SMP's Site just Launched!!!

Stop Motion Pictures (SMP) site has just launched!! Everyone one should go visit! if you have any suggestions for a movie or for the site you can comment right from the feedback page!! AWESOME!! :)

Topic by amakerguy    |  last reply

SMPS to Bench Supply - Help

Hi There, I want to make a bench supply using my old SMPS. I have seen many tutorials and I've some questions which I need assistance with. My SMPS says 12 V @ 25 A, 5 V @ 10 A and so on.. In tutorials I see people soldering all the same colored wires to one output 12V, 5V, 3.3V and so on. So, if we do that and I connect a 12V device that operates @ 2A or 3A  to the 12V ouput @ 25A in SMPS that we make, will it fry my device. If so, how do we control the current to supply 12V @ 2A only. I want to make a bench supply with below specifications. Can I do that? 1. I want 2 to 3 outputs each for 12V, 5V and 3V. 2. I want to regulate the current for each such socket mentioned in clause 1 to 1A, 2A, 3A and so on.. Is that possible? If so, how any instructions? Thanks, Avinash B

Topic by goudavinash_b    |  last reply

Problem with a 30-0-30VDC @10amps transformer/SMPS and 400WATT RMS mono amp(not PMPO) Answered

First of all thank you so very much, i have successfully build my rectifier but now i am having a problem with it. Can a 30-0-30VDC @10amps transformer/SMPS, power a 400watt-RMS car sub @4ohms with a 400watt-rms mono amp. When i tested the 400watt subs, the gain is too low or am i doing something wrong here. This is my 400watt-rms amp... Thanks much, appreciated.

Question by Lima79    |  last reply

Sony VCR power supply ratings? Answered

I have got a Sony SLV-XA-130-MJ Video Cassette Recorder/Player. I have disassembled it and have got he SMPS out. It has got a sticker saying "1 - 468 - 039 - 42" "SR642 MALAYSIA" "580786" The output connector has 8 terminals. Does anyone know the output details. Can some one provide a link or something?

Question by ajithkpunnoose    |  last reply

Connecting Two Li-Ion Battery Charger? Answered

Hi, can I connect this(please see image) two Li-Ion battery charger in parallel, to increase the amp. Thank you. Regards. Sorry image not uploading. Here is the link.

Question by Lima79    |  last reply

when my system start there is a sound of sparking in smps?

When my system start there is a sound of sparking in smps?

Question    |  last reply

Calculating the ripple current of the output filter of a full bridge smps?

I have been designing an offline 100khz 720 watt full bridge converter for 24 volts dc out at 30 amps. I've calculated that at a minimum duty cycle of .3 and a voltage ripple of .03v I need a minimum of 7k uf. I read the output filter section of "The Power Supply Cookbook" and it gives  this equation to get the peak to peak current ripple: I(pk-pk)=(2*Iout)/(min duty cycle). with a duty cycle of .3 this gives me 200A ripple current. With four caps each would need to be about 2000uf and a ripple current of 50A, which would be expensive. I've only every built flyback and boost converters so I wonder if the equation for peak to peak current ripple is only meant for those topologies, or perhaps I've calculated wrong. Is there a different equation I need to use or have I done something wrong? Any tips for selecting capacitors and what chemistry to use (tantulum/aluminum)? Thanks in advance I'm new to forward mode converters!

Question by sk8aseth    |  last reply

charge battery

I have battery 1cell NI-MH AA 1.2 v 1500mAH   and i need to charge it by using smps and diode for detect peak voltage of battery   i prefer fast charge for maximum 2 hours for my project  how much voltage and current i need in output of smps ?

Question by omar kotrash    |  last reply

i have a second hand sony SMP-N200 web reader.i cant get netflix...grrrrr help me please?

I got this thing second hand..but i am trying to get it to read netflix.....i hear there was difficulty between sony and netflix...i hope this is not the case or i will have a useless christmas present

Question by maninamousesuit    |  last reply

PSU design (major revisions): Transformer calculations help?

Recently I have attempting to design a proper dual-rail power supply that will allow me to set a voltage as low as +-1V up to +-30V in 0.1V increments at (hopefully) 3 significant digits (at least for the lower voltage settings). Anyway, this supply is also going to be current limited to up to 5A,again, it can be set to just about anything. I plan on using an Arduino micro-controller to set the output. In order to do this, I plan on using the analogWrite functions, or better yet, a legit DAC. There will be 4 outputs from the Arduino that will set the power supply output by applying a 0-5V voltage on the input of the 2 current limits and 2 voltage sets. (one for the negative rail, one for the positive). However, I have kept running into the same problem: how do I plan on driving this linear power supply with up to 200W*? My first idea was to use a a MOT, due to their high-power capabilities, and re wind the secondary with the right number of turns to achieve this output. However, I have heard that these transformers are not optimal for continuous running due to their poor and cheap design. (losses are very high). My second idea was to search around for a 250VA transformer. However, even until now, the VA rating confuses me. How does VA compare to W? I know this has something to due with reactive power, real power, and apparent power. However, I have no intuition of any of these 'powers.' How would I go about calculating the correct size transformer for the job, also, I am going to assume this linear power supply has the properties of a resistive load, since it is rectified and smoothed with a filter capacitor, so practically nothing should react with the AC power. (unless there is something more to the full-bridge rectifier setup I am considering.) This is when I came across unwound toroidal cores found on eBay for $25, the perfect price range! However, this has raised more questions! to start off, beyond turns ratio, I do not know now many turns I need for the AC side of things. I know intuitively and from experience, mains-frequency transformers do not work with only one (or even few) winding(s). I think this has to do with saturation, but I'm no expert by any means. and the inductive reactance of the transformer's primary. How do I calculate losses, inductance, and other important parameters of a homemade transformer like this? Things get very nasty when I look back at rewinding an old transformer. Now I have all these questions about inductive reactance, power, currents, magnetic flux and saturation, but also, about determining the original power rating of something like a very old small welding transformer or one from a large 10A car-battery charger. Is it possible to approximate the power by measuring the dimensions of the core? How close will this approximation be?  After getting frustrated with this, I considered alternative approaches. What if I purchased 2 ~20V ~6A SMPS (switch mode power supplies) connected them in series, and connect the center tap of my linear supply to the joining point between the 2 SWPS's? Would this be unstable and be bad for the SMPS if a load was connected between the 'outputs' of this new center tapped supply? Would any sort of balancing be required? Also, a bigger problem includes how this will be connected to my linear PSU design. With a low voltage @ high currents, I would be wasting a LOT of power, power that has to be dissipated away from the transistors. This heat can approach 200W, which is company unreasonable! Anyway, I would them have to either a switching preregulator, or modify the SMPS's so the voltage can be controlled easily and varied between, say, 3V to 20V. absolute accuracy is not required, close enough, and rest of my PSU should handle it. This becomes seemingly impractical too, and many other considerations need to be made. What should I do? what are the calculations and factors I need to know? i do not have an LCR meter to measure inductance, so trial and error is out. Does anyone here have experience at this? Help would be greatly appreciated! *The 200W figure was calculated by taking 40V, (What I believe would be a safe to allow some slack for +-5V voltage drop across my 2 shunts and transistors) and multiplying it to 5A of current for the maximum power output. ------------------------------------------------------------------------------------------------------------------- I have added an image of my current design, and I have modularized it the best I could. The YELLOW is all my current power-management circuitry. Currently just a transformer with many taps, going to a currently-undesigned switch box that will change the voltage on the output, which is then rectified and enters a filtering capacitor, finally entering the circuit.  The GREEN field is the voltage set. It is the most major part of the PID feedback loop, along with the ORANGE field. It works simply by feeding a voltage to the positive of a op amp configured as a comparator, and with negative feedback from the output. It then outputs a signal to the transistor, turning it either more ON, or more OFF depending on how the output voltage compares to the +Vset. The negative portion is largely the same, but the input voltage needs to be inverted so the output voltage is set negative properly. I was not able to use less than 2 op amps for this portion, unfortunately. The ORANGE field is current set. It works by measuring the voltage drop across the shunt resistor, and outputting a unity voltage that is referenced to ground, instead of to the positive rail. (It took me forever to finalize and perfect that!!!) Anyway, this voltage is then fed into a op-amp configured as a comparator to drive the transistor. The BLUE field is my switching regulation topology, which is controlled by both the ORANGE and GREEN fields. Do you like my use of diodes as a super-simple voltage or current selection switch? the op amp that outputs a lower voltage is the one that gets 'listened to' by the transistors. This way, current and voltage mode enable properly. This does add a small problem when it comes to powering the op amps, all of them have to be powered off of slightly higher voltages to swing the full range due to the voltage drops of those diodes. In the PINK field is simply a single-transistor solution to a constant current load. This allows the regulator to be regulated even at very low voltage set levels. This is why I am able to achieve a +-0.5V on the output (at least within LTspice) Finally, and most unimportantly, the light PURPLE fields have a simple ultra high-gain difference amplifiers that will detect if the output current and current set are the same, and turn On or OFF the respective LEDs. The green LEDs are voltage-mode indicators, and the red LEDs are to show when current-limiting mode comes on.

Question by -max-    |  last reply

Tube headphone amp

I want to build a tube headphone amp. Is it possible to make a smps (switch mode power suply) to power it? It would be like a mix between old and new technology!

Topic by dwj300    |  last reply

how i can reduce output current?

I have SMPS  with output ratingd 24v dc and 5A.  The other one is 12v dc motor which has max input current is 200ma with load.  How i can connect these both itoms?

Question by ParthP14    |  last reply

The classic IRFP250N vs FDP33N25? Which one is best for high power SMPS? Answered

I have an idea to start selling some powermax singing arc kits. In the kit I plan to include all the parts including a printed PCB to create an audio modulated flyback driver. I figure to start off with, since I have no clue what demand would be, I want to play it safe and only get enough parts for 10 - 25 quantity, which works out to be about $40, or about $4 a piece, not including custom PCBs. However, at >$2, the IRFP250 is not cheap even in 10's of quantities on Digikey. Looking to shave off pennies, I found the FDP33N25 for about half the cost of the classic IRFP250N and best part is that it appears to have simalar specs, and in some ways it looks like the FDP33N25 is even better! Bolded parameters are the (I think) prefered values. I do not know much about selecting the best transistor for the job, but I did compare the specs below: IRFP250N: 85mΩ Rds ON, 30A, 200Vds, 2800pf gate capacitance, TO-247, 0.65 *C/W FDP33N25: 94mΩ Rds ON, 33A, 250Vds, 2135pf gate capacitance, TO-220, 0.80 *C/W One thing I am concerned about power loss and therefore switching speed, so the MOSFET must be driven with a 15KHz to 40KHz square wave with very sharp rise and fall speeds. I was able to reduce power dissipation in my last circuit by simply shortening the wire carrying the signal to the gate, as well as adding a complementary pair of NPN and PNP transistors to the output of the 555 timer. That seemed to lower the drive impedance and switch the mosfet more rapidly, but considering that I still need to use active cooling and a brick sized heatsink, I think I can do better. Any suggestions?

Question by -max-    |  last reply

SSTC MOSFET over heating?

The following images shows my SSTC work, it is based on steve wards mini SSTC. But the problem is that the MOSFETs seem to heat up in like 3-4 sec of running. Input voltage is 220v AC(rectified and filtered later using a SMPS line filter).

Question by jasshopper    |  last reply

How to make or design this?

I want to make a CFL inverter powered by 12 voltage battery and a 220 voltage AC. Some people say it signal transformer or SMPS transformer that’s why I did not mention the name of it. To make and design the transformer what is the formula and materials is needed? Please! Please!!  Please!!! Help me to design this transformer. Thanks in Advance.

Question by robi_ncc    |  last reply

Charging a 8kj capacitor bank

Hello I have a 8 kj capacitor bank and am looking to charge it with dc power I was wondering if I could use a power supply such as this: Any feedback will be helpful Thank You-TDC

Topic by ThinkDesignConstruct    |  last reply

how can i use a lenovo 3000h series monitor separately...

I have   a lenovo 3000h series desktop..the cpu has gone bad ever the monitor is still intact ...i have a problem.. the monitor takes power thru the smps (pic shown ) thru the gray cable attached from the monitor ...i wish to use the monitor as a stand alone ....plz help ...

Question by dark_angel000    |  last reply


I have a 4v 0.5Ah lead acid battery. I have made some jouel thief circuit before. I have a torrid from a old SMPS. Now I want to use them as USB 5v supply to charge phone. How to make a converter????

Question by Soumojit    |  last reply

Minecraft mod: Cannon mod 1.7.3

Here is how to make your Minecrafting life much easier than it already is: This mod was created by Berkin and with his help I made this trailer.  It's been well received by the community and reviewed by some big Minecraft channels to boot. Instructions and download:;_token=AKuQGt9jVpiIlrLQ6vqJwEPQGzx8MTMxNTE5MjQ3NkAxMzE1MTA2MDc2

Topic by DJ Radio    |  last reply

Best LED driver?

I need to driver (5) 1watt white LEDs (forward voltage of 3.2~3.5v) and current of 350mA. I guess the best way would be to connect them all in series and somehow give them power. This is meant to be powered off of the wall socket (whether through SMPS or a capacitor or a resistor or a transformer or anything.). My question is what's the best way to drive them? I've never really used high power LEDs before. I'd also prefer to be able to adjust the brightness...

Topic by guyfrom7up    |  last reply

Instructable program stability?

WHY does the screen jump up and down when trying to read an instructable??? Its almost impossible to read. It would appear to be linked to the "adds" that are loaded. "Adds" meaning links to other stuff. Debian 8.4 on brand new G750JM completely stripped of any Micro$ software. Single boot. i7-4710HQ CPU @ 2.50GHz 3.16.0-4-amd64 (#1 SMP Debian 3.16.7-ckt25-2 (2016-04-08)) 16 G RAM with 93% free Invidea GTX860M video Joe

Question by joebog1    |  last reply

How many peltier module i have to use for removing heat load of 250 watt?

 i am using peltier modules  12706   ( vmax  15 v, Imax  6 A)               by checking it was running at   12 v  and 3.5 A and   peltier module 12715  ( Vmax  15V ,  I max  15 A )           was  running at  12 v  and 5.5 A I am using computer SMPS to run this peltiers so i can only get 12 v max is there any way to increase voltage to 15 volt.

Question by YogeshK33    |  last reply

Looking for cheap LiPo 3s low voltagle cutoof/balance circuit

Looking to add portability to a boombox project I built. Want to just grab a LiPo r/c pack and use a 3a 12v SMPS to charge it with. Know of a good battery protection circuit? This will be going to a non tech minded friend. So I'd like him to just be able to plug in the PSU when he is home without the worry of overcharging and be able to run it until the low voltage cut off is hit without worrying about killing the batteries. Any suggestions? It would be for this Thanks

Topic by Cancerkazoo    |  last reply

Need a protection circuit?

Hi i am making my own speaker system. i am using this amp the issue im facing is that a few days ago i power this amp with a smps 12v 1amp supply and it was working fine till something went wrong with the psu and there was a spark in the psu, the major problem which occurred  was that this caused a surge which travelled through the amp to my audio source which in this case was my computer. i ended up frying my sound card . can anyone help me make some kind of protection circuit which allows audio signals to pass through but does not let current from the psu pass through.

Question by cfrek    |  last reply

Program stability

I origionally posted this in questions, Instructable program stability? FACEBOOK TWITTER EMAIL Flag WHY does the screen jump up and down when trying to read an instructable??? Its almost impossible to read. It would appear to be linked to the "adds" that are loaded. "Adds" meaning links to other stuff. Debian 8.4 on brand new G750JM completely stripped of any Micro$ software. Single boot. i7-4710HQ CPU @ 2.50GHz 3.16.0-4-amd64 (#1 SMP Debian 3.16.7-ckt25-2 (2016-04-08)) 16 G RAM with 93% free Invidea GTX860M video I believe I have found the "bug"  It appears that the video entitled "Share what you make" keeps loading and loading and loading, This stream runs like this Is there anyway to stop this? Joe

Topic by joebog1    |  last reply

Cheap and portable >12V >10A PSU for small tesla coil? any good topload sugestions?

I am currently planning a small tesla coil (15 inches high, hopefully 5-12 inch sparks) I would like to make the unit small (desktop size). I decided to build the coil around a ZVS-driven flyback transformer rather than a standard NST or Oil burner transformer due to several advantages the ZVS circuit can offer: battery operation, smaller size, simpler math, no requirement to "match" the capacitance with the transformer, and since I have almost all the parts necessary to build another ZVS driver, why not!? The ZVS driver drive a DC flyback at approximately 15KV, which will then charge a homemade capacitor (I will not invest in a true MMC because it will put stress on the capacitors and connections, not mentioning the price of better quality film capacitors.) I have determined the dielectric breakdown of a few household items (plastic wrap, lids, lunch bags, etc. I assume they are low-density polyethylene) with my ZVS singing arc assumed to be at 8-10KV, and figured one layer of 5x7 inch compressed between 8 layers of plastic wrap gives an approximate capacitance of 0.7nF (sitting flat on a table with a few books to compress the plates closer together) to 1.44nF (after being rolled up very tightly. However, the breakdown voltage of this may be too low. I have yet to test this with my singing arc project)  The Capacitor will be several layers of plastic wrap sandwiched between layers of aluminum foil, which will be cut 3/4 inch shorter on all 4 sides, and after approximately 8-15 layers have been added, the capacitor will be sandwiched between 2 wooden boards with bolts on all 4 sides to permanently compress the capacitor to achieve approximately 10nF +- 5nF. This compression method might even help me fine-tune my tesla coil!  the aluminum plates will be tabbed, so that when they are stacked, the tabs will face opposite directions.  I might even submerge the capacitor in oil and pull a vacuum on it if I feel it will be necessary. However, I have not constructed a HV capacitor before, so I do not know how well this design will work. Does anyone have some experience in this matter? And lastly, my Power supply section to power the project: Has anyone built a ZVS-based tesla coil here? I see them all over youtube, with outputs ranging from millimeters (similar to my slayer exciter project)  to over a foot long! However, they never state what their PSU is rated for, or use 12 Lead Acid batteries, which I feel would be a bit impractical. So my question is: To get the output I desire, how many volts and amps should my power supply be rated for? I am thinking either a 24V 10A Switchmode supply from amazon, with the voltage adjust maxed out, or a 28V 10.8A SMPS, or a cheaper 24V 15A. SMPS. I thought about making a unregulated supply with a large transformer and a high-amperage full-wave bridge rectifier, but this cost more, and I cant be certain on it's quality. Can SMPS be used? can the amperage be below 10A? most importantly, does anyone have good data on current draw @ given voltages @ given # of turns on the inductor and flyback?

Question by -max-    |  last reply

DTH satellite receiver problem

I have a DTH satellite receiver which has a burnt SMPS power supply (image attached). I replaced the burnt components but again when powered with 220V ac supply to test the output voltages the same components burnt again within a few seconds. I could not figure out what is the actual faulty part. If anyone has any suggestion please feel free to answer. My second problem is the satellite receiver board (image attached) has 6 pins for power connection but I could not figure out what voltage is to be applied to which pin. So I was unable to use a separate power supply for the receiver board. The part number can be seen from the image itself. Please look at the receiver board and help me if anyone has any idea about this board. I tried searching in google with the part number but could not find the same board. Please help me. Any suggestion is welcome. Satellite receiver: Hicway ali M3328C(10039)-11

Question by smandal13    |  last reply

How do I bring this massive motor back to life? Answered

I have an old, fairly large treadmill motor lying around, and I would like to put it to good use again. However, I have a bit of a problem- the control board is missing, and I don't want to have to get a new one.... The motor has a sticker that says: P.M. D.C. Motor Model-C3354B3304 (judging by the number of hits that I got on eBay, this model is probably fairly popular) ICON P/N M- 190528 21.4 AMPS E62788 CW Rotation INS. Class H OPEN CONST. EXTERNAL FAN 1.5 HP CONT. DUTY @ 95 DC ICON Health and Fitness. (On the far right, it says "2.65 HP") ................................................................ What would be the cheapest way to get this working? I was thinking of getting a bridge rectifier with, adding an inductance to lower the current draw, and connecting some old caps from a computer SMPS to smooth the output, but I don't quite know if this will work. Can someone lend a hand?

Question by Shagglepuff    |  last reply

Minecraft LP

Hey guys, just wanted to let you know that I've started a minecraft LP. That's pretty much where I talk while playing minecraft and share my take on the game. I'm going to be releasing episodes once a week, usually more than that. I only have one episode up so far but check it out and if you like it, subscribe or just look out for new epsiodes, I'll probably have a second one up by tonight. Here's the link to the first episode: On a related note, I also have a less formal series going up which is just my friend and I playing survival multiplayer. I won't be releasing episodes of that series as constantly as my single player but that one's a little more fun and we're basically just messing around. If you're interested in that, here's the link to the first episode: Also, I might get some other people to play with us in the multiplayer survival world so if you'd like to participate in that send me a PM and we'll see. Thanks for reading and don't forget to subscribe if you like the videos.

Topic by jollex    |  last reply

Help me with my 3D printer

ISSUE: Stepper motors are not working when connected with RAMPS 1.4.OBSERVATION: The LED lights(LED 2,3,4) in the RAMPS 1.4 and Stepper motor are not powering up.PRATICES: I use Arduino mega 2560 and installed marlin firmware in it. And I bought a RAMPS 1.4 in a local electronic dealer. I placed the RAMPS over Arduino mega 2560. For testing I just connected 2 NEMA 17 stepper motors with RAMPS. When USB port connection is given from laptop to arudino board, a LED light is ON in Arduino board(L) and in RAMPS(LED 1). I use SMPS 12V 20A as a PSU for RAMPS. But in RAMPS the LED 2,3,4 is not switched ON. I checked the input voltage to the RAMPS using micrometer and it shows 11.75V. But there is no output from the RAMPS.Also I installed and tried Repetier firmware and grbl but it doesn't work.When I flashed Arduino with grbl, in this case all the LED lights in arduino and RAMPS 1.4 is switch ON. I use Candle GRBL software to test the stepper motors.And I replaced and tested with another RAMPS which is bought from Amazon but the problem remains unchanged.Hereby I attached images of circuit connections. kindly give some suggestions at the earliest.Thanks and regardsBaalaji V

Question by Baalaji V  

BJT vs MOSFET? Answered

-- background: In my perpetual pursuit for designing the best, cheapest, & best performing flyback (line transformer) driver, I've decided to try out some big BJTs, which appear to have higher voltage & current ratings @ considerably lower cost. In the past, I have tried MJE3055's, which work OK, and allow the generation of thin blue arcs from a 12V supply for a few minutes until the transistor dies due to high voltage kickback or overheating. The FDP33N25 gives good results but is somewhat unreliable at 24V. So I decided to give these alluring "PHE13009" 400V 12A rated NPN BJT's a try. However driving the transistor adequately seems to be the problem. (I didn't realize these transistors would require like 5A base current w/ only HFe of 2!) It seems like almost all the "good" driver schematics utilize large $$$ FETs or even IGBTs, but almost every CRT, plasma globe, and ballast (SMPS) I took apart seem to prefer high power BJTs probably due to this exact cost difference. I was only able to get simalar performance to my 33N25 MOSFET when I stuck an additional TIP120 in as an additional darlington stage, which worked very nicely (white hot arcs) for about 1 second, then it popped! :( Since the collectors are tied together they are all exposed to >200V transients, I am sure that's what killed it. I substituted that transistor for another PHE13009 to see what would happen and with a third driving stage (2N2222) I could get somewhat acceptable results but I know I can do better. >:) - My actual questions:  * The GDP of this transistor is 40MHz, seems fast to me. (certainly faster than the 2MHz GDP of the 2N3055 which works well in my slayer exciter.) and MOSFETs have significant gate charge. ECE2630 glossed over transistors mentioning BJTs are faster, (small signal ones, anyway :P ) and some internet sources agree, but I am finding lots of sources saying the opposite! What's the deal? Which one "faster?"  * How to traditional BJTs compare to IBGTs? Which are faster/better? The datasheet for this transistor explicitly mentions its use for "high frequency ballast and switch mode applications" which implies that it is well suited for my needs. It also includes a several inductor test circuits, but other than that the datasheet is pretty bare-bones.  I'm actually a little disappointed the HFe is so low (around 2-3) @ >10A. I may require more windings on my primary and a 48v supply. (not ideal) * I know I will dissipate a little more heat due to the base current, and something I didn't consider was heat dissipated in the resistor biasing/controlling the base. (like 12V at several amps just to drive the damn thing!!) so it is worth the cost benefit of $0.5? Is there a configuration I could use that makes driving the transistor easier?

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