Page 2 of 5 FirstFirst 1234 ... LastLast
Results 11 to 20 of 42

Thread: Car SMPS Project

  1. #11
    Quote Originally Posted by Silvio View Post
    Hi bad boy, I think you made a good choice as that kind of setup is more robust and more forgiving. What I am aware of is the 3 farad capacitor. This can easily destroy you rectifier diodes during start up. The transformer itself will also give surge in the mains and may blow your fuse during switch on.

    If you want an easy soft start to build you can find one in my blog posts. I made this for my isolation transformer which was around 1500w.

    One other option is to connect the battery first before switching on the supply so that the battery will charge the capacitor instead.
    Please also note that the battery itself will act as a capacitor and smoothing down the ripple.

    I would include the soft start as this will help things to tame down a little bit at start up.

    Regards Silvio
    Thank you dear Silvio for your through explaination
    The diodes I'm using are capable of withstanding 2000A surge current for an half cycle of 50Hz but always it's a good idea to have a protection board

    Thanks again

  2. #12
    Quote Originally Posted by kegs View Post
    For rectifier the best place is from a PC POWER supply as they are high speed and paralleling several is a good bargain
    that was the first place I look but those diodes can only withstand 30 to 40A current and I know that paralleling diodes is not a good idea unless they are exactly the same

  3. #13
    I test my inverter with my car battery and here's the result :

    Without load : 172V in output << 12.9V input
    23W load : 152V in output << 12.9V input
    65W load : 147V in output << 12.87V input
    100W load : 145V in output << 12.75V input
    230W load : 132V in output << 12.56V input
    370W load : 118V in output << 12.38V input
    450W load : 110V in output << 12.13V input


    Here's my inverter's Schematic :
    new.jpg

    inverter frequency : 30 KHZ
    Transformer windings :
    Primary : 2+2 turns of 300 strands of 0.25mm wires ))
    Secondary : 12+12 turns (( 70 Strans of 0.22mm wires ))

    Is there something wrong with the schematic??? why the voltage drops is so high ???
    I even test it with higher input (15V) and at 600W the output voltage reach 136V
    ???
    Last edited by badboy_6120; 06-14-2018 at 04:23 PM.

  4. #14
    .... Silvio's Avatar
    Join Date
    Apr 2015
    Location
    Malta
    Posts
    530
    Blog Entries
    9
    Quote

    Is there something wrong with the schematic??? why the voltage drops is so high ???
    I even test it with higher input (15V) and at 600W the output voltage reach 136V
    ???


    Let us consider things a little bit
    According to the windings we have 2 turns Pri 12 turns sec So the ration is 12 /2 =6 The ratio is 1:6 This means that for 12v input the output voltage is 6 times higher so 12v X 6 = 72

    We have a double secondary so the output suppose to be 72 X 2 = 144v Now you have to consider that if the battery voltage is say 13v then the output be 13 X 6 = 78 78 X 2 = 156v
    Taking all this strait forward as shown above will indicate a specified voltage which is not true in reality. As you can see from every 1 volt lost in the input you are loosing 12v on the double output winding.

    This voltage drop is unavoidable because loses exist everywhere 1) in the winding itself 2) leakage inductance in the transformer 3) the switching transistors 4) the output diodes 5) The internal resistance of the battery, 6) the traces on the pcb and also the wiring from the battery to the inverter.

    The first light load as you saw lost a lot of voltage and it seems that that extra voltage without load is due to some spikes that generated this voltage are stored in the output capacitor. This extra voltage is dumped very quickly when loading the smps due to that this extra voltage has a very short pulse and not strong to sustain any load.

    To overcome this problem you need to compensate either from the input which is rather hard in a way as a lot of current is involved and traces must be kept short and wide as possible. You should also enhance them by putting a few 0.8mm bare copper wire and soldering them directly on the traces of the pcb to minimize resistance. I chose 0.8mm because of skin effect at 30 Khz.

    The other option is to make another turn or two on the secondary to get a higher voltage and add feedback to your circuit. If you intend to add feedback you must also include an output inductor. This will store voltage during short pulse on light load. Be careful as this has to be tailored for the best compromise between low and high loads.

    One last thing I like to mention if you are loading a continuous load things seem a bit harsh on the smps and the 3 farad capacitor will not work here. When loading with an amplifier this becomes a different story as the load is not continuous and now the 3 farad capacitor will come into play and will sustain the voltage much better as it will have time to charge up again between each interval of the varying load.
    The output capacitor has the same effect as the input. If you try to measure the output voltage with a working amplifier you will note that the output does not change that much.

    I hope this helps you understand much better

    Regards Silvio
    Last edited by Silvio; 06-14-2018 at 09:03 PM.

  5. #15
    thank you dear Silvio

    I increase each side of the secondary windings by 2 turns and the voltage drops seems to be normal now
    but I have a problem now and that's when I connect 15V at the input and I get only 110V at output
    and in this situation only three of the mosfets ( parallel) that are handling half of the cycle will get hot (under load) and the other side stay cool
    I think it's a problem with 500 Pot that handle dead time as when I set it to different value it changes the hot and cool side

    any idea?

  6. #16
    .... Silvio's Avatar
    Join Date
    Apr 2015
    Location
    Malta
    Posts
    530
    Blog Entries
    9
    Quote Originally Posted by badboy_6120 View Post
    thank you dear Silvio

    I increase each side of the secondary windings by 2 turns and the voltage drops seems to be normal now
    but I have a problem now and that's when I connect 15V at the input and I get only 110V at output
    and in this situation only three of the mosfets ( parallel) that are handling half of the cycle will get hot (under load) and the other side stay cool
    I think it's a problem with 500 Pot that handle dead time as when I set it to different value it changes the hot and cool side

    any idea?
    Look closely what is happening. Check the gate drive on the mosfets and see that enough voltage is arriving at the gates >10v.
    If for any reason this voltage is lower than it can be the case that the mosfets are not getting fully switched on as they should and tend to heat up. Hook up the scope for this test.

    It could also be that the primary winding is not symmetrical and is causing this problem. Snubbers must be fitted here across each pair. See the wave form across the primary and search for any spikes on the waveform. These may prolong the switch off of the fets or may be disturbing the wave form at the gates. The dead time can be set for 2uS and left as it is. This should be enough for the time being. The larger the dead time the more power is lost.

    Regarding the 15v input it is a bit too much and it could be that the core will tend to saturate.
    Are you hearing some kind of clicking or whistling noises during high power output at 15v input?
    You can increase the frequency to overcome the saturation problem, try at 40Khz instead. The reason for this is that at a higher frequency less turns are needed for a given voltage. With the copper wire used in your setup skin effect is not an issue as this being only 0.25mm which can go to 100khz or more.

    Regards Silvio

  7. #17
    Quote Originally Posted by Silvio View Post
    Look closely what is happening. Check the gate drive on the mosfets and see that enough voltage is arriving at the gates >10v.
    If for any reason this voltage is lower than it can be the case that the mosfets are not getting fully switched on as they should and tend to heat up. Hook up the scope for this test.

    It could also be that the primary winding is not symmetrical and is causing this problem. Snubbers must be fitted here across each pair. See the wave form across the primary and search for any spikes on the waveform. These may prolong the switch off of the fets or may be disturbing the wave form at the gates. The dead time can be set for 2uS and left as it is. This should be enough for the time being. The larger the dead time the more power is lost.

    Regarding the 15v input it is a bit too much and it could be that the core will tend to saturate.
    Are you hearing some kind of clicking or whistling noises during high power output at 15v input?
    You can increase the frequency to overcome the saturation problem, try at 40Khz instead. The reason for this is that at a higher frequency less turns are needed for a given voltage. With the copper wire used in your setup skin effect is not an issue as this being only 0.25mm which can go to 100khz or more.

    Regards Silvio
    It turns out that the problem was from saturated transformer (as you mentioned) but I am getting 1500W without any problem with ETD59 in my half bridge smps with 1600 gauss
    and as I calculated I'm running the smps with 1600W at 15V in input
    (15*10^8)/(4*32000*2*3.68)

    am I missing something here? because I can't get more that 800W from the transformer without going into saturation

  8. #18
    [QUOTE=Silvio;15221]Look closely what is happening. Check the gate drive on the mosfets and see that enough voltage is arriving at the gates >10v.
    If for any reason this voltage is lower than it can be the case that the mosfets are not getting fully switched on as they should and tend to heat up. Hook up the scope for this test.

    It could also be that the primary winding is not symmetrical and is causing this problem. Snubbers must be fitted here across each pair. See the wave form across the primary and search for any spikes on the waveform. These may prolong the switch off of the fets or may be disturbing the wave form at the gates. The dead time can be set for 2uS and left as it is. This should be enough for the time being. The larger the dead time the more power is lost.

    Regarding the 15v input it is a bit too much and it could be that the core will tend to saturate.
    Are you hearing some kind of clicking or whistling noises during high power output at 15v input?
    You can increase the frequency to overcome the saturation problem, try at 40Khz instead. The reason for this is that at a higher frequency less turns are needed for a given voltage. With the copper wire used in your setup skin effect is not an issue as this being only 0.25mm which can go to 100khz or more.

    Regards Silvio[/QUOT

    The original diagram can be found @ http://sound.whsites.net/ Project 69

  9. #19
    .... Silvio's Avatar
    Join Date
    Apr 2015
    Location
    Malta
    Posts
    530
    Blog Entries
    9
    Hi bad boy well saturation will only occur if there is not sufficient number of turns,

    What is keeping you to try the inverter at a higher frequency? Try that and see if there is the same effect.

    If you have the same result I am afraid you have to add another turn to the primary winding

    Silvio
    Last edited by Silvio; 06-16-2018 at 06:02 AM.

  10. #20
    .... Silvio's Avatar
    Join Date
    Apr 2015
    Location
    Malta
    Posts
    530
    Blog Entries
    9
    @kegs

    @ kegs The circuit you mention on the link sent is a low power smps for a preamp (project 69)
    Link http://sound.whsites.net/project69.htm

Similar Threads

  1. 500W Smps project
    By ludo3232 in forum diysmps
    Replies: 23
    Last Post: 12-07-2015, 08:11 PM
  2. 1 KW SMPS Project Discussion
    By MicrosiM in forum diysmps
    Replies: 24
    Last Post: 02-28-2014, 02:44 AM
  3. My first SMPS project - help needed please
    By Venture in forum diysmps
    Replies: 3
    Last Post: 11-14-2013, 12:41 AM
  4. Questions about smps project
    By jm-31000 in forum diysmps
    Replies: 0
    Last Post: 04-20-2013, 06:48 AM
  5. Open SMPS Project 1kW
    By Murilo in forum diysmps
    Replies: 5
    Last Post: 07-26-2011, 12:08 PM

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •