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Dual output isolated DC-DC forward Converter cross regulation problem.

Atul Kumar20
Prodigy 100 points
Other Parts Discussed in Thread: PMP5123

Dear Sir,

Greeting for the day!!!

I am going to design the dual output DC-DC Forward converter as below mentioned spec.

Input : 18-36Vdc

Output: 15V/2A & -15V/2A

Switching Freq. : 250kHz ( Fixed)

All Regulations: < 50mV 

Effi>80%

I want to simulate to my design prior to fabricate the PCB and other relevant activity. Sir my design scheme is first converted input voltage 18-36Vdc into 8V at forward topology transformer secondary side due to control the duty cycle going to beyond 50% at 18V input, then 8V is boosted to 15V/2A by Switching boost regulator. I create the two secondary winding for dual outputs ,output-1 is control by the feedback close loop control by the duty cycle through opto coupler. output -2 is unregulated .sir in the balance load condition both output are ok but if my output-1 at no load and output-2 is full load condition the voltage drop at output-2, means cross regulation problem has been occured and pre loading is required to the output-1 for normal operation hence  effi. of converter decrease.

Sir i also seen the Synchronous switch post regulator (SSPR) to control the regulation of unregulated auxiliary output in multioutput power supply. how to use SSPR kindly send the application note ,

I am using non TI PWM controller and simulation software, Kindly suggest the relevant application note and schematic.

Many Many Thank You

Regards

Atul Mishra

DC-DC Forward Converter scheme.pdf

Isolated Forward topology.

  • 0
    TI__Expert 7395 points
    Atul,
    Thanks for your interest in TI. I've contacted the appropriate product group. You should see a reply soon.
    Regards,
    John
  • 0
    TI__Intellectual 2230 points
    Hi Atul,

    Thanks for the inquiry. And I really would like to recommand active clamp forward solution for your design. Forward converters with active-clamp reset offer multiple benefits to designers and are presently popular choice. Due to it can achieve zero voltage switching, lower switch voltage stress, reduced EMI (electro-magnetic interference) combined with significant efficiency improvements and extended duty cycle range.
    More information relative to the active clamp forward please go to below links:

    www.ti.com.cn/.../snva591.pdf
    www.ti.com.cn/.../getliterature.tsp

    And I think there is no need the boost converter with active clamp technique, you can using a turn ratio < 1 (eg. 3:4 ) to step-up the primary voltage to secondary, then the duty cycle will reduce to 62.5% when Vin = 18V, refer to the reference design PMP5123:

    www.ti.com.cn/.../PMP5123

    Thanks
    Oliver
  • 0 in reply to Oliver Pan91
    Prodigy 100 points

    Dear Mr. Olivar,

    Thanks for your reply.

    Sir, PMP5123 is a single output design, Kindly send me dual or multi output DC-DC Converter design scheme and relevant data with tight cross regulation and high efficiency for reference, outputs Cross regulation is my primary concern. The design would  be more helpful to me if which TI part's used in design have the Pspice model TI.com.

    Many many thank you.

    Warm Regards

    Atul Mishra