Ask Mel Berman, from TDK-Lambda a question about AC-DC power supply and DC-DC converter applications

thanks,wish more people can get support from Mel Berman .

Hi,

I'm searching a charger component for a battery  pack of 2 cell LiFePO4 (7,2V or 7,4V) from USB supply.

Havee you  got reference of a charger component who integer step up regulator, or a  step up regulator who can start in short circuit?

Thanks

Thank  you, but your suggested solution is not very stable without feedback. And I want to use this converter as a source of reference  voltage -300V (minus 300V).

Anyway thank You.

Best regards.

S.

Hi Mel,

Have a power supply question here.

A few years back there was a AC/DC 12 volt power supply listed on this site.  It was one that I used, made a board for for and has worked very well. I found a site that has a full description of the schematic.

http://www.circuit-projects.com/battery/car-charger-for-12v-batteries.html

I recently had a charger/voltage regulator go out on a lawn tractor (dealer say's he'll be happy to replace for $80).  The tractor has a alternator output of 28V, 10A I am trying to make this circuit work for the tractor, however the input voltage to the bridge rectifier is so variable (based on engine RPM's).  I understand this circuit.  I would like to utilize the 10A if headlights, clutches, etc. are engaged, I may need the output.  Modifications that were made to my original design was to put a 2N6397TG2N6397TG in the place of the Q1.   I realize it is a comparator circuit of sorts, but I am unsure as to regulating the voltage in front of the Q1 without the use of a 7812 (too low of a rating), if I could find a 13.5V 10A voltage reg, I had might as well go buy the part from the dealer (cost factor).  Any suggestions?

Ps. I would like to keep the LED functionalty

Dave

Q for Mel Berman: As a part of my project , a home automation product  -  a smart switch which replaces the existing mechanical switch  , i want to make a power supply from mains for the internal circuitry operation. The only two terminals  available for me are  one is the Line and the other is  one end of the load .During Swicth Off position , there will be 230v ac available across the switch which i will rectify to get the required dc. During switch ON position I will have current ,which i have to convert to voltage abd get the supply . As the final size of the product is critical , am facing difficulties to implement these two especially the CT portion.

Thanks

abdul haseeb

Question to Mr Berman  Is it somehow possible to construct a DC-DC converter that can take an input voltage from 0.2-0.6V and up it to 5v? What Im thinking of here is a single PV-cell that can deliver 4W...  The converter doesent have to start from the input, because I will have a battery backup to run a MC.  Best Regards  Rasmu Hildonen

Hi Mel,

I would like to step down the power supply from 48Vdc to 28Vdc and the typical current is 12.5A. Do you have any solution?

Thanks.

Hi, Mel, i have car audio amplifier , and in it is blown FEP16DTD. And i cannot get it in EUROPE, maybe you could help me?

Or just search google.

Hi Mel,

I'm using the FPS1000-48 AC-DC supply (two of them to supply symetrical +/-55V)

And now I'm redesigning the power source and want to get rid of the proprietary connector on the FPS version. I've found the RFE series power supplies with screw terminals.

Can you please confirm that the RFE1000-48-YRFE1000-48-Y could be a direct replacement for the FPS1000-48 ?

If not can you suggest a 1000W power supply for my scenario? (2 modules in series with center tap to make symmetrical output voltage, voltage trimable up to ~60V)

(I'm using the supply to power our industrial amplifier (6x300VA) for a synthetic mains generator, so the current draw from the supplies copies a 50Hz sine wave.)

Thanks,

Miki

Hi Mel,

   what is a good choice to design a Led Power Supply with 115-230V input and 12V output (constant voltage) with hight power factor and efficiency? I'm looking for a reference design or tool to obtain up to 60W (ON semiconductor, Linear T., T.I., ST...) for a test. Can you help me?

Linkswitch 613.... I would just like to purchase a ready made ac-dc converter modual; universal mains in and 5V 1W out worst.   Do these exist in a small outline (vis. the off the shelf modual that works at 72Vdc in)?   I can just shoehorn in a setup using the linkswitch 613 which is more powerful than I need.

The 613 worked, but I had to play with that clamping /damping cct. to get a proper result at each end of the mains-in spread.  I'm using the recommended cct....   why do these never quite work?

What might I have over-looked?

Geoff

Mel,

I'm using an LMC7660 charge pump to provide power to an LM4562NA/NOPB.LM4562NA/NOPB. op amp in an audio EQ. The problem is the LMC7660 operates at 10khz and provides a whine onto Vee. My question is ;  if I use a low pass filter  to cut out the 10khz what would be the ideal choice of components to remove the hum and try to maintain some sort of efficiency. Ideally squeezing out as much power as I can. I was thinking around R=47ohm (to limit Volt drop) and changing Cr to around 33uf  and putting the same filter on the V supply to the charge pump giving good roll off but I don't know what effect this will have on the device ? Any ideas?

Hi Mel,

Please can you help me choose a suitable switching regulator? I need to step a DC42V lithium ion battery current down to 4.2V to drive a GSM modem. Most of the time the GSM modem only uses about 2mA of power but it occasionally bursts up to 2A for short 4ms periods during transmission. I need the conversion to be as efficient as possible so as not to flatten the lithium ion battery. I tried an Allegro A8499 but it kept cutting out when the 2A transission bursts happened. Do you know any switching regulators that are suitable for this kind of conversion.

Thankyou and best regards,

Harley

Hi Mel Berman!

I am working with an EL wire. I have set-up a circuit similar to that of Jeri Elsworth EL WIRE POWER SUPPLIES. (link http://www.youtube.com/watch?v=AcXHx5ikjM4) It works great. Now I am looking online to purchase a trasnformer for this circuit so that i can make a friend one too. I can't seem to find any small transfromers. The one I am using currently from salavged parts measuring 14mm X 14mm X 16mm and was PCB mounted. Also I know that this trasnformer has a single coils on each side with one being centered tapped. Originally the circuit I pulled the transfromer from was battery operated with an input of 3VDC and step-up to 115VAC. (where the EL wire used to go)

Since I wasn't satisfied with it's brigness level on the original circuit. I used Jeri's circuit to provide the system with 5VDC and stepped up to 140VAC for the EL wire. I have also set up the time constant so taht the resistor is variable with the Capacito making the frequency adjustable. Now the big question is, what sort of power transfromer would you recomend for this project.

Thanks in Adavanced,

-Josue Cruz-Lambert

Can I ask a question of Mel Berman of TDK Lambda,

About high frequency ac input rectification?

Hi, I would like to have a high dc voltage output of 5KV and low ampere, how can i fabricate a dc-dc converter?

Hi, I'm not sure if I'm asking this in the right place, but here goes.

Does anyone know where I can find a battery clip that holds 4 cr2032 button cells?

I've been looking around and can only find ones that hold a single cell

anything constructive appreciated Thank you

Hello Mel,

I am building a DC-DC converter to convert the 14.8v 6A power coming from a professional camera battery to 9V 2.5A used by a DLR, I am trying to build this converter using the LM317 since it's the only easily available power regulator (which I don't have to order 2500pcs to place an order), the problem is the LM317 can only output 1.5A max, can I build the circuit using 2 of them and connecting the outputs of each circuit in paralel to get 9V 3A, is there going to be any kind of problem that may fry the camera?

Thank you

Oscar

Can i use a buck converter and boost converter in the same circuit ? I want to boost 4 nicad cells up to maybe 9 to 12 volts and use that for 1 part of the circuit, then drop it down to 5 volts for another part of the circuit. I am thinking of doing it this way so I can get a steady voltage supply to the different parts of the circuit. Or should i just start with 12 volts and then drop it down to 5 volts ?

I am building an Altoids USB power supply. I have an LM7805 converting down to 5v at 1 amp. But It's like 40% efficient. I am getting an LM2596 which has 150Khz oscillator and 3amp output. Now would charging an Ipod at 3 amps be bad for the battery, or would the ipod just take 1amp and leave the other 2 amps alone. Because most USB ports dont output more than 1 amp. If this is bad for USB devices with batteries, How would I lower the amperage but not the voltage?

Hi Mel,

I hope you're still answering questions here. I want to build a simple unregulated DC supply for a 115vdc 1.4 amp motor. From what I've gleaned from the web, I need about a 150vdc 1000 uF filtering cap. These seem to be very expensive! $200-300. Am I looking at the wrong type of caps? Do I need a cap at all?

Thanks,

Ron