83 Replies Latest reply on Aug 7, 2014 9:32 AM by help911

    Ask the Expert, David Norton about AC-DC power supply and DC-DC converter applications

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      Thank You, Your Friends at element14 Community

       

      David Norton

      David holds a BSc. (Honors) in Electrical and Electronic Engineering and has 30 years of experience in the power supply industry.  His expertise is in AC-DC Power Supplies, DC-DC Converters, EMI Filters, Fault-Tolerant Power Systems and Switchmode Power Topologies.

        • Re: Ask the Expert, David Norton
          albertalchin

          Hallo

           

          I don't know if this is the place to ask but I am looking for transformer copper foil to turn my primary and secondary windings of n dc - dc full brige power supply and it has a lot of current on the secondary (200A)  where is a good place I can buy a 10m roll of the stuff. I am from south africa.

          • Re: Ask the Expert, David Norton
            yrault

            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

             

            Best  regards
            • Re: Ask the Expert, David Norton
              DeltaRay
              Aloha-David,  I need some manufacuturing direction for an Axial Flux Generator, do you know of any US based companies?
              • Re: Ask the Expert, David Norton
                Trout

                Kind of new to forums hope I posted this correctly.

                 

                I need a diode but don't know how to ascertain values.  It will be used on 12 volt DC (motorcycle).  This is an antique (35 yrs old) with electric start which will be on display and started remotely.  We want to temporarily supply power to the ignition from the starter solenoid while the engine is being started.  Once the engine runs and the oil pressure comes up it will close a switch and take over supplying the current.  We need to use a diode in the circut to prevent feedback to the starter solenoid once the 2nd circut comes on line.  If it is not isolated in this way then the starter will continue to be engaged with the engine running.  I know how diodes work but have no idea how to purchase one that will hold up.

                 

                Thanks, Trout

                  • Re: Ask the Expert, David Norton
                    Nortski

                    Hello Trout,

                     

                    Ideally you would need to find out what the current draw is, though I would not expect the ignition to draw more than 10A.  A 50V rated would give you some margin against any spikes..  Might be a case of trying one and seeing how hot its gets.  A general purpose type would be good enough.

                     

                    Thanks

                     

                    David

                  • Re: Ask the Expert, David Norton
                    satya

                    Dear Sir,

                     

                    Kindly suggest a way to protect microcontroller circuits from surges when the power supply is derived from the mains.

                     

                    With best regards,

                     

                    Satyabrata Das

                      • Re: Ask the Expert, David Norton
                        Nortski

                        Hello Satyabrata,

                         

                        There are two ways.  One would be to buy a power supply that meets EN61000-4 immunity.  It should be stated on the datasheet.  The other would be to buy an EMI filter that attentuates high voltage pulses and put that between the AC input and the power supply..  TDK-Lambda's MAW series has that feature.

                         

                        Thanks

                         

                        David

                      • Re: Ask the Expert, David Norton
                        Bengt

                        Hi David.

                        I hope that you are the right person to answer my questions.

                         

                        I'm designing a wireless measurement board. Some of the spec:

                         

                        - Battery powered from one Li-Ion cell.

                        - Bluetooth module

                        - 8 bit XMEGA low power microcontroller

                        - Low noise. ADC is 14 bits, VCC=3V so one LSB =180 µV

                        - Low power. Idle current is in µA range

                        - Small size, ~40x50 mm

                        I have designed some versions already but I have not found out the best way to do it yet.

                         

                        In one design I have non-isolated DC/DC-converters. This may generate noise but I can not compare because of other problems with the design in this board like a misplaced crystal close to an amplifier and no filters of signals between digital and anlogue. (SPI)

                        In all other designs I use linear regulators.

                        I know that if the Bluetooth module have to send with high power (longer range) there will be noise.

                        The GND planes are separated for digital, Bluetooth and analogue and only connected at the power supplies.

                        The power supplies is filtered on the input with a LC-filter and on the output with a PI-filter. The L is a multilayer ferrite. C is small for analogue as it is a constant current consumers but large for Bluetooth (~100µF)

                        During each sample the power can be high, like 100 mA depending of if the board also generate anything at the sampling (like light) or not. After that there will be some calculations or other software tasks and data transmitting to the Bluetooth module that takes ~100 µs but most of the time between the samples the system is idle.

                        The Bluetooth module have send bursts in the kHz range.

                         

                        Do you have any idea of what approach that might be best for this kind of power supply? The power must be very noise free but also consume almost nothing during idle.

                        DC/DC-converter or not is of course the most important question.

                        There to put and what type of filters is also important.

                          • Re: Ask the Expert, David Norton
                            Nortski

                            Hello Bengt,

                             

                            I would use something like Linear Tech's LTC3252, that is a dual output converter, but they probably have a single output version.  They claim to be low noise and have low standby currents.  Looks fairly simple to use.

                             

                            Thanks

                             

                            David

                          • Re: Ask the Expert, David Norton
                            hms

                            Hello David

                             

                            can you help me, I'm looking for a special PWM-Controller. It is for a Charger with a Microcontroller,  for some different batterie types, first Lead Acid Gel. It should work with a 24V DC Voltage, Output must be regulated in a Range from 2V up to 15V. Also the Output (Charging) Current must be regulated in a wide Range, up to 3 or more Amps. This should done with reference voltages, generated by the Microcontroller. Therefore all Error Amp Inputs must be free connectable, and not connected to any internal reference of the PWM-Controller. Furthermore i wish me an Output that can directly control a Power MOSFET as switcher, or an internal Power switcher. All Controllers that i found, has only one or two npn Transistor Outputs, and need additional Parts to control a Mosfet (UC3524, TL494).

                            Thanks, best Regards

                             

                            Holger

                              • Re: Ask the Expert, David Norton
                                Nortski

                                Hello Holger,

                                 

                                You may want to give Atmel a call.  They have some microcontrollers designed for power supply use (electronic ballasts for fluorescents).  Fairchild also have some I understand.

                                 

                                Thanks

                                 

                                David

                                  • Re: Ask the Expert, David Norton
                                    hms

                                    Hello David

                                     

                                    That's right, but these devices (AT90PWMxx) has not enough programm Space for the application that i have planned (only up to 16 kB).

                                    Furthermore there are some other  limitations (no I2C-Bus-Hardware-Interface for Communication with the HID-Module, and others). Thats why i favorize a design with separate Microcontroller an PWM-Controller.

                                     

                                    Thanks

                                     

                                    Best Regards

                                    Holger

                                      • Re: Ask the Expert, David Norton
                                        dtsai@916

                                        Hi, David

                                         

                                        Is it safe to use a Carol 12/4 SOOW wire (600 V) to hook up with an equipment requiring at least 20 A (recommended 25 A) 220 V, single phase power into a 30 A single phase breaker socket?  Since the equipment only requires 3 conductors (black, white, and green), is it OK to leave the red one in the cable without connecting it? My concern is that would the cable can carry the load of 20 A if I only use 3 of the 4 conductors?  Thx.

                                         

                                        Daniel

                                          • Re: Ask the Expert, David Norton
                                            Nortski

                                            Hello Daniel,

                                             

                                            I'm not that familiar with cables, but usually the current rating applies to each cable.  The 20A rating is for the National Electrical Code, if there is a possibility that the equipment will draw more (during overload or brown out conditions), then you should use a thicker gauge wire.  The only problem I see with using a 3 phase cable for a single phase application is that someone may see the 4 wire cable & hook up the equipment to three phase.

                                             

                                            If you have an electrician co-worker or friend, they will be able to give you the answers for certain.

                                             

                                            Thanks

                                             

                                            David

                                    • Re: Ask the Expert, David Norton
                                      denimageau

                                      Hello David,

                                       

                                      I'm looking for a DC-DC converter with this species :

                                      Vin = 12 Vdc

                                      Vout= 0 - 120 V dc

                                      I out =0- 1.5 A

                                      remote control via rs232

                                       

                                      i spent lot of time looking for that but it's not a standard converter. Could you give me some devices ?

                                       

                                      Thanks

                                      • Re: Ask the Expert, David Norton
                                        elementjames

                                        i have a irfp204    mosfet  semi conductor it  says   

                                         

                                        irfp204

                                        r p748xb

                                        2v  7c                         were do i get some i need possably 6 and do the numbers translate to new ones

                                        • Re: Ask the Expert, David Norton
                                          alytle
                                          I have a phase control thyristor (SCR-SF300U13) with a gate trigger current (Igt) maximum rating of 260 ma.  A vendor replaced it with an SCR-T700 with a rating of 150 ma.  The SCR failed.  Is it possible that the replacement SCR failed due to the lower IGT rating?  The only other difference between the 2 SCR's is that the original had a peak forward gate voltage rating of 16 volts and the replacement is something less than that, but relatively close.  Did I get the wrong replacement?  Thanks,
                                            • Re: Ask the Expert, David Norton
                                              mberman

                                              Hi Allen,

                                              Our expertise lies in the application of commercial and industrial AC-DC power supplies and DC-DC converters.

                                              We are not prepared to answer questions about specific semiconductors or components used in these devices.

                                              May I suggest that you go back to the vendor who suggested the replacement SCR.

                                              Regards,

                                              Mel

                                            • Re: Ask the Expert, David Norton
                                              rcr22b

                                              I want to use two 7 event AC timers to control the same AC pump motor.

                                               

                                              How can I isolate each timer from the other?

                                                • Re: Ask the Expert, David Norton
                                                  mberman

                                                  Hello,

                                                  Don't understand why you need 7 different timers for the same motor.  Can't you combine some of the timing functions into one timer or a smaller number of timers?  Nonetheless, if you must use 7 different event timers to control the same motor, each timer must have "isolated contacts" that provide AC power to the motor when it requires the motor to operate. This can work if you wire it correctly.  For example, make sure you use the same AC power source for all 7 timers with the same Line and Neutral connections going to the motor.  In other words, make sure that in a worst case situation, that if 2 or more timers are "on" at the same time, they are providing exactly the same AC voltage to the motor from exactly the same AC source (same phase, etc.).  It's like have multiple power cords connected from the same wall outlet going to the same AC motor.  There would be no problem.

                                                  Regards,

                                                  Mel

                                                    • Re: Ask the Expert, David Norton
                                                      rcr22b

                                                      Thanks Mel,

                                                       

                                                      I was not very clear in my previous post.

                                                       

                                                      There are only two timing devices with 7 events for each one.

                                                       

                                                      But my original thought was the same as yours.

                                                       

                                                      Wire neutral to neutral and hot to hot using two male plugs to plug into each timer.

                                                       

                                                      What happens is that when the first event is activated it zeros the data in both timers.

                                                       

                                                      I'm doing something wrong or maybe the digital timers are not wired to allow such a simple work-around.

                                                       

                                                      Anyway thanks for your reply.

                                                  • Re: Ask the Expert, David Norton
                                                    jchere

                                                    David: I need to connect 2ea 12V batteries to a charger. I want the 1st battery to charge until its voltage equals the 2nd battery, then to charge both, but to isolate the 2nd from the 1st whenever the 1st voltage is lower than the 2nd.

                                                    In other words, I need an ideal diode. My idea is a compairitor and a power FET. Can you send me to such a circuit?

                                                    Thank you.

                                                      • Re: Ask the Expert, David Norton
                                                        mberman

                                                        Hi John,

                                                         

                                                        Our expertise is in the applications of AC-DC regulated power supplies and DC-DC converters.

                                                        Battery chargers are very specialized devices, as are your design goals.

                                                        Sorry, we do not provide circuit designs.

                                                        However, I feel you are on the right track by considering MOSFETs as electronic switches (ideal diodes).

                                                        Also, as you may know, Schottky diodes have a very low forward drop.

                                                        Make sure you provide enough heat-sinking for the these devices, depending upon your worst case charging current.

                                                         

                                                        All the Best,

                                                        Mel

                                                          • Re: Ask the Expert, David Norton
                                                            jchere

                                                            Hi Mel: Thank you for the reply, but it appears I didn't make my question clear enough.

                                                            I am not asking for a battery charger. All I am asking for is a switch/diode circuit.

                                                            Shotky diodes have about 0.45 volt foreward drop. A FET would have about 0.03 volt drop at 10 amps, or more than 10 times less.

                                                            All I am looking for is a circuit that turnes the FET on and off depending on the voltage between the input and output.

                                                            Thank you. John Christensen.

                                                        • Re: Ask the Expert, David Norton
                                                          TONYB58

                                                          I WANT TO BUILD  A PURE SINE WAVE INVERTER    48 VDC TO 120/240 VAC 10,000 WATTS @ 60 HTZ   TO RUN A HOUSE  OFF GRIDD CAN YOU DRAW A SCHEMATIC  AND A PARTS LIST?

                                                            • Re: Ask the Expert, David Norton
                                                              mberman

                                                              Hi Robert,

                                                               

                                                              Unless you have many years of experience in the field of AC-DC Inverters, I would recommend that you do not take on a 10,000 watt unit as you describe. I deal in AC-DC power supplies and DC-DC converters only, not inverters.

                                                              I don't think anyone would send you a schematic and parts list for this super high power Inverter.

                                                              Nonetheless, if you want to know more about this subject I suggest you contact an applications engineer at International Rectifier.

                                                              http://www.irf.com/indexnsw.html

                                                               

                                                              Regards,

                                                              Mel

                                                                • Re: Ask the Expert, David Norton
                                                                  Nortski

                                                                  Hi Robert

                                                                   

                                                                  Elgar / California Instruments has such products I believe.  (www.elgar.com)

                                                                   

                                                                  It costs several $100k to develop such products, so they will only sell you a complete unit.

                                                                   

                                                                  Best regards

                                                                   

                                                                  David

                                                                    • Re: Ask the Expert, David Norton
                                                                      ae_dee

                                                                      Hello David,

                                                                           I am looking for an AC/DC power supply with the following specs below.

                                                                      1.) Input Voltage of 85-265 Vac.
                                                                      2.) Output Voltage of 150Vdc
                                                                      3.) Max. load current of 1.67Amps.
                                                                      4.) Max output Power of 250 Watts
                                                                      5.) Min efficiency at full load of 85%
                                                                      6.) Output Voltage tolerance of +/- 1%
                                                                      7.) Line Regulation of 2%
                                                                      8.) Fully Encapsulated
                                                                      Where can i find this power supply? Thank you.
                                                                      Best regards,
                                                                      Adrian
                                                                        • Re: Ask the Expert, David Norton
                                                                          Nortski

                                                                          Hello Adrian,

                                                                           

                                                                          Sorry but I don't know of anyone that makes a 250W encapsulated AC-DC power supply. There are a number of LED types that are IP66/67 at that power range, but usually they are much lower output voltage.  Is there a reason you need it encapsulated?

                                                                           

                                                                          Thanks

                                                                           

                                                                          David

                                                                  • Re: Ask the Expert, David Norton
                                                                    seba

                                                                    Hello,

                                                                    I want to cerate  DC-DC converter from 12VDC to -300VDC. Output voltage must be stable as  possibile. Iout < 3mA. Uout will be reference votage for measurement system with 16bit  ADC. I try to do it with use flyback regulator with reversing amplifier on  feedback. Is  this a good way?

                                                                    I will be grateful for any help.

                                                                    Best  regards

                                                                                S.

                                                                      • Re: Ask the Expert, David Norton
                                                                        Nortski

                                                                        Hello S.T.

                                                                         

                                                                        If you need stability, then you will have to use feedback of some type.  A flyback is pretty much the simplest circuit to use for low power is you need isolation from input to output.

                                                                         

                                                                        TI have some good application notes available.

                                                                         

                                                                        Best regards,

                                                                         

                                                                        David

                                                                      • Re: Ask the Expert, David Norton
                                                                        seba

                                                                        Thank You, I will seek a similar application of the DC/DC converter (from +12VDC  to -300VDC) on TI Webpage.

                                                                        Best regards.

                                                                        S.

                                                                        • Re: Ask the Expert, David Norton
                                                                          Shifty

                                                                          Hi,

                                                                           

                                                                          I wonder if you can point me in the right direction.

                                                                           

                                                                          I have been asked to assist a team traveling in artic conditions, by assembling a battery charging system for camera batterys. At the moment the prefered power source is Solar.

                                                                           

                                                                          Ideally the system should be simple and light weight.

                                                                           

                                                                          The battery in question a Sony BP U30 or (BP U60). Its a 14.4V, 1.95Ah  Lithiun Ion battery, to supply a 12V camera and 13.5 Watt power consumption.

                                                                           

                                                                          My inital thoughts have been to look thorugh a host of battery charger IC's and can see that would be a bit beyond my technical limits without putting in a bit of study. Not only that it is a bit complicated. Keeping things simple is quite important considering the remote locations the team are likley to find themselves. I have examined a already pre-build battery charger, and it is very straight forward. A 240V Ac to 16.8V Dc supply with a couple of diodes to show if the battery is charging or not.

                                                                           

                                                                          My understanding of charging technolgy is that Lithium Ion are contstant voltage batterys in order to charge. As long as you have a high enough current source and maintain a constant charge voltage, 20% over the battery nominal voltage it should charge quite well.

                                                                           

                                                                          So I was thinking of assembling a solar cell array, and feed them in to a DC to DC convertor outputing 16-17V DC. The input to the convertor should handle the variation of input from the solar cells and as long as I have enough to give the required amps... it 'Should' work..

                                                                           

                                                                          Can I ask if basic approch is sound or am I likley to blow thigs up?

                                                                           

                                                                          Thanks

                                                                           

                                                                          Liam

                                                                          • Re: Ask the Expert, David Norton
                                                                            cllerici

                                                                            Hello David,

                                                                            can you help me finding a cheapher solution to insulated measure DC voltage up to 1000V ?

                                                                             

                                                                            Thank you and Best Regards

                                                                            Claudio

                                                                            • Re: Ask the Expert, David Norton
                                                                              riscy00

                                                                              Hi David, happy new year 2011!

                                                                               

                                                                              I'm working on a project related to oil/gas, where I'm driving solenoid to open and close MUD fluids.

                                                                               

                                                                              The solenoid is about 22R static resistance, 24V, est 25W. I have 26V-50V unregulated power, 2A. 

                                                                               

                                                                              Based on investigation, there is two methos

                                                                              (a) Large cap bank which is pre-charged and then disposed into solenoid with powerful kick leaving with holding current. This disadvantage of this that it is not efficient and cap bank is too large.

                                                                              (b) PWM, where it control the voltage and current into solenoid during the kick and then steady state.

                                                                               

                                                                              I/P power is variable, so its need 24V buck regulator, however with PWM this can do buck regulator as well.

                                                                               

                                                                              My only issue with the PWM is the kick part, I seen TI part DRV102F/500DRV102F/500, where PWM take place after the kick, but does not seem to regulate 24V. I'm trying to avoid large caps.

                                                                               

                                                                              I need some working parameter / solution that is used to drive the solenoid so I can get some confidence with this concept.

                                                                               

                                                                              I'm also looking into dedicated MCU with PWM to take charge of the feedback.

                                                                              • Re: Ask the Expert, David Norton
                                                                                stairm

                                                                                David,

                                                                                I would like to power a 0.5 ohm heating element at 40 watts to use as a Hot Wire Ignition test. Can this be done simply by placing it in series with a 1 ohm resistor and powering it with a 15 volt, 15 amp power supply? I figure setting the supply at 13.4 volts will get me roughly 40 watts at the element. Am I missing something here? Do you have a recommendation on a power source that could do this?

                                                                                Mike

                                                                                • Re: Ask the Expert, David Norton
                                                                                  weld407

                                                                                  I am looking for 2 relays for Jack plate on my boat  they made by Tyco  VF4A-35F11-Z07 relay need to find and but 2 of these littl babies

                                                                                  can you help me on this or do have a new part #

                                                                                  • Re: Ask the Expert, David Norton
                                                                                    GALE

                                                                                    HI David,

                                                                                     

                                                                                    Have some old & new Sorensen DC power supplies the manual for the new power supply SGA 40-125  (0-40VDC 0-125 AMPS) says that you need to protect the power supply from inductive kickback  & back EMF.  We use these power supplies for testing our PMDC motors & gearmotors and we have not been protecting the older Sorensens like a DCR40-70 and I do not think it has caused any problems but the manual for the olders ones does not have this statement.

                                                                                    So since we have this new power supply how do I select the proper diodes to protect a 0-40VDC 0-125amp power supply?  The manual states that they should be rated greater than the supply's output voltage & current - is that all I need to make my selection because I was looking at Newarks website and I am not sure what kind of diodes to get - what about Vishay Formerly IR - 301ura80 -800V300a stud round junction?

                                                                                    Thanks,

                                                                                    gale

                                                                                    • Re: Ask the Expert, David Norton
                                                                                      maxmax

                                                                                      How to measure the DC current from a pulse transformer? The pulse width is 10 ms and maybe 20A. i dont know the voltage, i only know full load power are 125 W/s

                                                                                      • Re: Ask the Expert, David Norton
                                                                                        brdprinting

                                                                                        I have a machine that has a four output power pack in it. 5VDC, 5VDC, 8.5VDC AND 24VDC.  The 8.5 volt leg is only producing 6.6 volts when plugged into the disply board that it operates.  It does show 8.5 v with no load.  To make sure the power pack was producing the amps that it needed I stacked 6 "D" size Energizer batteries to make a 9 volt power pack. ( it produced 9.2)  I diconected the 8.5 volt output of the machines power pack and substituted my battery strip.  The machine proformed like a champ for about 2.5 hours until the battery strip output droped down to about 7.2 volts.  Turning the battery strip of for a for a short time and then back on brought us back to life for about 90 seconds.  This inticates to me that just the 8.5 volt leg is the only part of the powerpack that is failing.  I think I could get this all up and running with a 9 volt linear power supply that puts out as much as my battery strip.  What do you think I might need to pull this off?  Or am I not seeing all the problems this solution might cause?

                                                                                         

                                                                                        Thanks for your help on this

                                                                                        Karl

                                                                                        • Re: Ask the Expert, David Norton
                                                                                          Loshogans

                                                                                          Dave, Do you have any motor run capacitors? here is what I am looking for 6uf, 15uf, 30uf,, 60u,f 70uf, 5% to 10% tolerance 10,000 @125  four tab post, 480v to 660v film type  not dry type

                                                                                          • Re: Ask the Expert, David Norton
                                                                                            NeepGlass

                                                                                            I recently purchased some

                                                                                            Order Number: 186542

                                                                                             

                                                                                            Part No:
                                                                                            01N5044

                                                                                             

                                                                                            Manufacturer Part No:
                                                                                            V15H16-CZ100-KV15H16-CZ100-K

                                                                                             

                                                                                            Description: MICRO SWITCH, PIN PLUNGER, SPDT 16A 250V; Microswitch Type:Standard; Actuator Style:Pin Plunger; Operating Force Max:100gf; Contact Voltage AC Nom:250V; Contact Current Max:16A; Switch Terminals:Quick Connect; Circuitry:SPDT

                                                                                             

                                                                                            the switch type that I purchased, to my knowledge comes in two styles momentary (a switch that is in a on position when compressed) and a maintained switch (compression to turn it on and then compression to turn it off) and your sight does not have that info listed per item. the support line told me that i was ordering the right switch but when I got it in it is a momentary switch and what i need is a maintained with the same specifications (ie. size and switch type)

                                                                                            could you tell me wich item you carry that is the right switch for me  PLEASE  PLEASE   PLEASE

                                                                                             

                                                                                            thank you

                                                                                            jacob

                                                                                            • Re: Ask the Expert, David Norton about AC-DC power supply and DC-DC converter applications
                                                                                              kevinpsc

                                                                                              Dear David

                                                                                               

                                                                                              I am looking for a Sintex 45S capacitor, or an equivalent component. Until it melted, it was functioning as a motor start capacitor in a Little Giant 1/3rd HP swimming pool cover pump, model number APCP-1700G. I have tried searching everywhere for an electrical component supplier who stocks it, but cannot find one and Franklin Electronics who manufacture the pump have so far been completely unhelpful. Because it melted so badly, most of the specification on the label has been destroyed, which makes it difficult to know what alternative to search for. However, I can just about make out that it is AC 450V 50/60. There may be a further part to the model number of C2A - 8, but the damage is so bad it's not clear.

                                                                                               

                                                                                              Thanks

                                                                                               

                                                                                              Kevin

                                                                                              • Re: Ask the Expert, David Norton about AC-DC power supply and DC-DC converter applications
                                                                                                Gordon132

                                                                                                Hi David,
                                                                                                I'm building an induction heater but want to be able to control the power. I came across a suggestion on the internet to control the phase of one side of an H Bridge which seems quite a neat way of doing it but no circuits. It could almost certainly be done using a uP but it isn't in my skill bag and I can't find anything anywhere to do it discretely. I came up with a design which I can simulate in Tina-TI and LTSpice but thought I'd pass it by you before I go re inventing the wheel. I'll briefly outline the design. I have two linear ramp generators created from 555 timers. I feed one with the 100kHz signal direct, the other with the signal inverted (which is one of the outputs to the bridge). This gives me a linear ramp for each half cycle. I feed this into two comparators which have the same reference voltage. The outputs of the comparators go into a set/reset flip flop which provides the output for the other side of the bridge. By varying the comparator reference voltage I can vary the phase from almost in phase to 180 degrees out of phase.

                                                                                                 

                                                                                                Q1) Will phase controlling one side of the bridge work as a power control?
                                                                                                Q2) Is there an established way of doing this that you know about?
                                                                                                Q3) Is there a better way of doing this? What I've come up with would on the face of it seem to work but would be highly dependent on matching components and keeping them all at the same temperature.

                                                                                                 

                                                                                                I look forward to your comments.

                                                                                                 

                                                                                                Gordon

                                                                                                • Re: Ask the Expert, David Norton about AC-DC power supply and DC-DC converter applications
                                                                                                  Hofstad

                                                                                                  Hello,

                                                                                                   

                                                                                                  so i am working on lighting the XYAB buttons on an Xbox 360 wireless controller, but i am having problems finding a power source, i can only find a power source above 3.6v(white led) when i connect the charging cable(5v-usb), but i want the LED's to light when i don't have the cable connected. So i guess I'm asking if there is a way to increase the voltage from the battery(2,7v fully charged)up to 5v?

                                                                                                   

                                                                                                  Thanks, Hofstad.

                                                                                                   

                                                                                                   

                                                                                                  Edit: I whuld think something like THIS might do the trick, and then from 20v, resistor it down so it can run 4 LED's? or maybe buffers?

                                                                                                  • Re: Ask the Expert, David Norton about AC-DC power supply and DC-DC converter applications
                                                                                                    RandyStewart

                                                                                                    Hi David,

                                                                                                     

                                                                                                    I have a very old blower motor from the early 1950's. 

                                                                                                    It will no longer start.  It will buzz.  I think the capacitor is out.  Has not run for maybe 8 years since the stopped using it.

                                                                                                     

                                                                                                    Motor made by The Louis Allis Co. - Milwaukee, Wis.

                                                                                                    Single Phase Capacitor Start induction run motor integral mounted starting unit dual voltage

                                                                                                    Motor:  .75 hp  Type:  OGCU  Frame:  203  Class: P  PMP 175  Volts:  115/230  Amps:  11.4/5.7

                                                                                                    Rated for continuous operation

                                                                                                     

                                                                                                    Capacitor is 3 5/8" long x 2 1/16" diameter.  Black

                                                                                                    Has written on side:

                                                                                                     

                                                                                                    ETS 250

                                                                                                    233-281 MFD

                                                                                                    60 cycles

                                                                                                    125 VAC

                                                                                                    Cornell Dubilier

                                                                                                    KF

                                                                                                     

                                                                                                    Can you help us find a capacitor for this old motor?

                                                                                                     

                                                                                                    Thanks,

                                                                                                    Randy

                                                                                                    • Re: Ask the Expert, David Norton about AC-DC power supply and DC-DC converter applications
                                                                                                      Srom

                                                                                                      Hello David, I´m Looking for a power supply (127 Vca to 12 Vcd) with battery backup. Could you help me with a supplier or with information?

                                                                                                      I want to make an "UPS" for a solution.

                                                                                                      Best Regards.

                                                                                                      • Re: Ask the Expert, David Norton about AC-DC power supply and DC-DC converter applications
                                                                                                        tomacno1

                                                                                                        Hello, I need help repairing my american made inverter plasma cutter.  The IGBT in this unit has failed. The #'s on the face of the IGBT are unreadeable.   The plasma has a 120 volt - 20 amp input rating.

                                                                                                        The  IGBT is a  to-247ac style

                                                                                                        . Do you have any suggestions for a  replacement or any particular values I should consider when choosing a replacement?

                                                                                                         

                                                                                                        Thanks,Thomas

                                                                                                        • Re: Ask the Expert, David Norton about AC-DC power supply and DC-DC converter applications
                                                                                                          MosheSh

                                                                                                          I need a small indicator light that will show when a current is (YES) running thru a wire or NOT.

                                                                                                           

                                                                                                          In my case I need it for better control of mechanical equipment of 120 volts 15 amperes max. on an alternate current.

                                                                                                           

                                                                                                          Please email architect7@jps.net

                                                                                                          Or call: 510-725-7205

                                                                                                          Moshe Shafrir

                                                                                                          General Contractor

                                                                                                          • Re: Ask the Expert, David Norton about AC-DC power supply and DC-DC converter applications
                                                                                                            1tguy

                                                                                                            This is an imbarrasingly simple question. I am working to regulate a 12 volt 7 Amp battery. I used a 7812 Voltage Regulator with a simple aluminum heat sink and it blew up very quickly. I cannot find what the input current limitations are on this device. I wanted to keep this simple, can you suggest a solution? Thank you.

                                                                                                            • Re: Ask the Expert, David Norton about AC-DC power supply and DC-DC converter applications
                                                                                                              WJ_ANG

                                                                                                              I would like to have a high dc voltage output of 1.5KV and low ampere, how can i fabricate this?

                                                                                                              • Re: Ask the Expert, David Norton about AC-DC power supply and DC-DC converter applications

                                                                                                                Hi,

                                                                                                                 

                                                                                                                I need some technical support to guide me for a purchase of either LTC3588-1 or DC1459B-ADC1459B-ALTC3588EMSE-1 Demo Board | Piezoelectric Generator Power Supply).


                                                                                                                We want to harvest energy from a piezo sensor which is producing voltage in range of 1V and current in micro-ampere range. Whether the above mentioned electronic items prove helpful for us?


                                                                                                                Please suggest so that we can place the order as early as possible.


                                                                                                                Regards,

                                                                                                                ========

                                                                                                                 

                                                                                                                NAVEET KAUR

                                                                                                                Research Scholar

                                                                                                                Department of Civil Engineering

                                                                                                                Indian Institute of Technology Delhi

                                                                                                                Hauz Khas New Delhi 110 016 (INDIA)


                                                                                                                • Re: Ask the Expert, David Norton about AC-DC power supply and DC-DC converter applications
                                                                                                                  help911

                                                                                                                  Hi,


                                                                                                                  I'm not sure if you are the right person to ask but I need help. Firstly know nothing about motors so please bear with me. I have 6 big circular wooden cut outs that I want to rotate independently of one another but I don't know how to pick the right motor for them. The cut outs made of mdf are 1210mm in diameter. They are about 5 kgs in weight and they will be rotating off center. I have tried to calculate the torque and inertia etc, but I'm not sure if my calculations are right nor am I sure if I have understood the physics of it all. Could someone please help me choose the right motor? Honestly at this point I don't care bout how fast or show the motor rotates. I just want it to be able to rotate my piece 360 degrees.

                                                                                                                   

                                                                                                                  Any help would be greatly appreciated.