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Thread: TL494 schematic by 0xff

  1. #1

    Smile TL494 schematic by 0xff

    Hi,

    I designed this circuit with discrete high side bootstrap driver. I decided not to use IR2110 or transformer gate drive.
    I dont know why but I hadn't luck with IR2110.

    Lets start with the controller part:



    I used the first error amplifier for feedback regulation and the 2nd for current limiting.
    I supply the IC with 15V zener diode feeded from 320V with two 68k 2W resistors in parallel. I think this is enough like its in IR2153.

    Now the power part:


  2. #2
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    Quote Originally Posted by expressel View Post
    Hi,

    I designed this circuit with discrete high side bootstrap driver. I decided not to use IR2110 or transformer gate drive.
    I dont know why but I hadn't luck with IR2110.

    Lets start with the controller part:



    I used the first error amplifier for feedback regulation and the 2nd for current limiting.
    I supply the IC with 15V zener diode feeded from 320V with two 68k 2W resistors in parallel. I think this is enough like its in IR2153.

    Now the power part:

    It looks good how about some tests and pics of the wave forms produced. The goal is a good drive current with a nice square and fast rise times.
    What is the intended power of this smps? I asking this because at higher than say 500w an auxiliary winding will be necessary to feed the 15v drive circuit.

  3. #3
    Thanks, I'll do a test when my new scope arrive. The intended power is 250W, I have many transformers from computer ATX supplies.

    I asking this because at higher than say 500w an auxiliary winding will be necessary to feed the 15v drive circuit.
    You mean that the zener can't provide the neccesary current for the gates?

    Oh I forgot to draw a snubber.
    Last edited by expressel; 01-08-2019 at 09:25 PM.

  4. #4
    p.jpg

    The high side, i should go like that.
    Or just on the ir2153.

  5. #5
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    Quote Originally Posted by kanon View Post
    p.jpg

    The high side, i should go like that.
    Or just on the ir2153.
    Hi Kanon the high side gate must be isolated from the low side gate and the ground for the high side drive must be in the centre of the half bridge. The bootstrap capacitor will have to give all the current needed to the high side.

    The ground path of the bootstrap capacitor will be when the low side fet conducts this will create a path to ground hence it will charge up between each cycle. This capacitor must not be too large as according to the frequency used it has to be fully charged. The higher the frequency the less time it has to charge. A value is set for correct operation.

    For a frequency between 50 and 100Khz a value of around 0.5 to 1 uF will suffice. It is important that you use a good quality capacitor here as this will take quite a beating. It could also be of a non polarized type like polypropylene film capacitor or an electrolytic of the gold or silver type marking with low ESR

    Total isolation can only be created with a gate drive transformer as the primary of the gate drive transformer is isolated from the gates of the fets. Another method is to use 2 separate drive chips fed from 2 independent 15v aux supplies thus one aux will have a common ground to the high voltage ground and the ground of the other aux will have a ground on the centre of the half bridge. This will become more complicated and is only used when there is the need of high gate current.

    However for your need a 0.47 uF bootstrap capacitor will be enough for the smps you are building as here you will be using medium power fets like IRF840 or IRF740.

  6. #6
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    Quote Originally Posted by expressel View Post
    Thanks, I'll do a test when my new scope arrive. The intended power is 250W, I have many transformers from computer ATX supplies.



    You mean that the zener can't provide the neccesary current for the gates?

    Oh I forgot to draw a snubber.
    Yes the resistor- zener arrangement will provide the necessary current needed in your case for a 250w smps driven from medium power fets.

    As for the snubber do not worry about it just see the wave forms across the primary and only include it if needed. If the wave forms are clean from spikes when loaded then you do not need it.
    Last edited by Silvio; 01-09-2019 at 09:35 AM.

  7. #7
    Thanks Silvio.

  8. #8
    Quote Originally Posted by kanon View Post
    p.jpg

    The high side, i should go like that.
    Or just on the ir2153.
    kanon, you are right that the totem pole must be connected to the source of the high side fet but the first transistor's emitter must be connected to ground because its controlled by the TL494.

    Like this:

    p2.jpgp2.jpg
    Last edited by expressel; 01-09-2019 at 06:48 PM.

  9. #9
    Here I upload more clean schematic. (:

    Attached Images Attached Images

  10. #10
    Last edited by expressel; 01-12-2019 at 07:43 AM.

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