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LM5021: Not getting desired ouput in TINA

Ashokraj Pilli
Prodigy 210 points
Part Number: LM5021
Other Parts Discussed in Thread: TL431

Hi, 

          I am trying to design AC to DC converter with flyback topology. With input RMS voltage =240V, ouput 24V, 2A. I have used web bench power supply to design this circuit. I have simulated the circuit in TINA but I am not getting desired ouptut. I would like to know the following : 

  1. Web bench has showed this component (LM5021) has capabilities to operate with 240 to 340VPeak to peak. My doubt is in the datasheet of LM5021 the maximum input voltage for VIN is 30V. Does this component has the capabilities to convert VRMS 240 to 24V ? If not this component can you recommend some other component which has tina spice model. 
  2. I would like to know why am I not getting desired output when I have designed the circuit similar to web bench power supply. Is something wrong with Web bench or it is the issue with TINA or my circuit designing? I have used non linear secondary output transformer and editted the total number of windings to suit the requirement. Please let me know what are the changes I will have to make in this circuit to get the desired ouput.  
  3. I have attached my TINA file, WEb bench power supply pdf. 8081.WBDesign40.pdfLM5021.TSC

  • 0
    TI__Expert 7080 points

    Hi Ashiokraj,

    1. if you look at the block diagram of LM5021 , You will find that there is a internal 36V clamp Zener on VIN pin . most of the voltage drop will on external resistors which connected to VIN pin even the Bulk voltage is up to 240Vac_rms.

    2.3. I have reviewed the schematic you provided . here are some recommendations for your reference:

      1). The maximum allowed voltage for TL431 KA is 37V , the output voltage in your application is 24V , so Rreg/Creg/Dreg can be removed .

      2). Parallel a 1k resistor on opto-coupler diode , so the minimum required Ika by TL431 can be flow in this path.

      3). Ccomp2 =4.7nF will lead to a long delay for FB loop , could you please remove it or change to 100-200pF ?

    After implement above changes , if you still can't get a desired output , I think it has nothing with the schematic , but the setting of TINA or others . you have to check it by yourself .

    Thanks.

  • 0 in reply to Jaden Ning
    Prodigy 210 points

    Can you tell me what are the settings I will have to change in TINA? 

  • 0 in reply to Ashokraj Pilli
    TI__Expert 7080 points

    Hi Ashiokraj,

    Sorry , I am not familiar with TINA , could you please ask the question in another post without part number LM5021 but TINA.

    I believe some other engineer whom in charge of TINA will help you.

    Thanks.