• State Resolved
  • Locked Locked
  • Replies 8 replies
  • Answers 2 answers
  • Subscribers 65 subscribers
  • Views 1776 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

7805 DC to DC switching regulator

Anonymous
Anonymous
Guru 17045 points
Other Parts Discussed in Thread: TPSM84203

Can anyone tell me how this circuit works?

  • 0
    TI__Guru 71526 points

    Hello again Andy,

      There is no circuit diagram visible in your post.  You must first click the Insert Code, Attach Files and more...          at the bottom right of the dialogue box.  A toolbar will then appear, you can click the 'attach clip' icon to add the graphics file. 

    We'll be glad to look at this as soon as we can see the circuit in question! 

    Regards,

    ~Leonard  

  • 0
    TI__Genius 9550 points
    Andy,
    we can't find your schematic and your description is too simple, so can't give more anwer.
  • 0
    TI__Expert 4875 points
    Hi Handy,

    Are you talking about TPSM84203? It is a TO-220 power module with a 400kHz 28V DCDC buck regulator integrated. The inductor is also integrated in the module. It is targeting on replacing 7805 type LDO for better efficiency and thermal. As you may know, switching regulator will have better efficiency than linear regulator. Let me know what is the specific question you are asking.
  • 0 in reply to Anthony Lang
    TI__Genius 9550 points
    Handy,
    your question is not clear, so i will close this thread. Please open a new thread or clarify your question in this thread.
  • Anonymous
    0 Anonymous in reply to Jason Wang (BSR-MV)
    Guru 17045 points

    This is the circuit, it is from an old TI datasheet I happened to find in a collection of datasheets I had printed off and so I built it and verified that it works and the output voltage seems to be that of the linear regulator's and Zener's voltages added together.     

  • Anonymous
    0 Anonymous in reply to LeonardEllis
    Guru 17045 points
    Thanks for the help, this information enabled me to insert the file.
  • 0 in reply to Anonymous
    TI__Expert 4875 points
    Hi Handy,

    I think seldom people will use the schematic you attached nowadays. Is the pinout of L78 like Vin for pin1, GND for pin2 and Vout for pin3? If so, you circuit uses the charging and discharging period of input cap(0.33uF) to turn on and off transistor. You are using L78 to control a buck switching regulator. But since the switching frequency is not controllable and low, the inductor and output capacitor are using big value. The cost and size will be a big problem.

    TI has a lot of buck switching regulator ICs and modules. The power switches are all integrated. For the module, inductor is also integrated. With high switching frequency, our device size and cost is very optimized. I would recommend you to directly choose a switching regulator. TPSM84203/05/12 will be a good start for you. It is a 28Vin 3.3V/5V/12V fixed output power module. It is pin to pin with L78.
  • Anonymous
    0 Anonymous in reply to Anthony Lang
    Guru 17045 points

    Okay, thank you for the explanation, I will look into the TPSM84203 and yes, the pinout is 1Vin, 2 Vout, and 3 Gnd.