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LM3478: 15V --> 350V : Boost OR Flyback Design?

Darren Kozey
Prodigy 10 points
Part Number: LM3478
Other Parts Discussed in Thread: LM5155, TPS40210, LM3481

Greetings,

I am needing to design a high voltage, low current compact supply. The specs are as follows:

1) Input voltage: 10V-17V

2) Output Voltage: 350VDC

3) Output Current (max): 10mA (nominal about 5mA)

I was wanting to use the LM3478 for its low cost, high voltage spec (500V), and small 8-pin package.

The questions are:

a) Is it possible?

b) What configuration is best; BOOST, FLYBACK, one or the other in combination with a voltage multiplier?

c) Is there some other controller that would be better?

Thanks.

PS. i have also been trying to simulate with the LM3478 pspice model using Orcad PSpice, but it does not want to play well (convergence problems, any tips?)

  • 0
    TI__Guru* 78370 points

    Hi Darren,

    Thank  you for reaching out and considering our products.  I would like to recommend the LM5155, our latest boost/flyback controller superior to the LM3478.

    Anyway, both LM5155 and the LM3478 can support your applications.  

    For such high step up ratio, I would like to recommend the flyback configuration, because the transformer turns ratio brings in a freedom in optimizing the duty cycle and better overall performance. 

    However, you can use Boost plus the charge pump stage, like in the following ref design.  The controller of these two ref designs use TPS40210 and LM3481, but the similar concept also apply to LM3478 and LM5155. 

    http://www.ti.com/tool/PMP20212?keyMatch=300V&tisearch=Search-EN-Everything

    www.ti.com/.../PMP8621

    Best regards,

    Youhao Xi, Applications Engineering