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MC33063A: 5V-400V Step up Converter

Purushottam Pawar
Prodigy 60 points
Part Number: MC33063A

Hi,

Greetings of the day!!!

We need 400V/10uA DC voltage in one of our application. I am trying to generate 5V to 400V DC voltage as per configuration in attached image. 

I have used approximately 3mH inductor and achieved voltage upto 270V. But problem is the voltage is gradually decreasing (Voltage drops down to 2V it puts continuous on) and the power Mosfet is heating too much.

As per datasheet Vout= 1.25(1+R2/R1), which indicates it is depending on resistor values. But during testing the output voltage is changing with change in Inductor value. With (10-100) uH inductors voltage is ~100V. When used (1-3) mH Inductors voltage rise to ~ 270V.

Please  suggest how should I achieve this much of stable voltage without heating the components.

Thanks 

Paddy 

  

  • 0
    TI__Guru* 78370 points
    You may consider to add a charge pump stage to your current circuit, to double the output voltage. You can refer to the schematic at the following link for how the charge pump stage is added to the boost circuit to produce higher voltage.

    www.ti.com/.../tidrom5.pdf
  • 0 in reply to Youhao Xi
    Prodigy 60 points

    Thanks for suggestions and sharing the circuit. I will check suggested schematic.

    I would like to know, what could be the reason for heating of Mosfet.  I have not connected the load to output voltage as well.

    Also I would like to know your comments on the schematic which I shared earlier. (Will it work as it is or needs any modifications)

    Thanks & Regards,

    Paddy

  • 0 in reply to Purushottam Pawar
    TI__Guru* 78370 points
    There are a few factors that can cause the MOSFET FET hot. The 1st is inadequate gate drive, and the FET is not fully turned on, and can still be in linear mode or close to that mode with high Rds(ON). This is usually related to low VCC voltage. Please double check that the VCC is well established. Another one is the switching losses, if the driver is strong enough, but the layout causes a gate ringing or Vds ringing. You can use a scope to measure the MOSFET Vds.