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UCC28950: UCC28950

A.S.Bhushan
Expert 1060 points
Part Number: UCC28950
Other Parts Discussed in Thread: PMP8740

Hi,

I have taken reference design from infineon for 54V, 35A DC-DC converter. (ref:   EVAL_2KW_ZVS_FB_CFD2.)

In this design they are using UCC28950, (PSFB)

Problem :

Our aim is to design a 48V battery charger for input range of 250V DC to 400VDC. We modified transformer, in order to get, 54V, 35A output for this range.

Output is coming for resistive loads.

For resistive loads as per given below 

Vin DC

Vout

Iout

Remarks

270

54.05

24A

When I increase the load more than 24A, output is decreasing gradually

280

54.05

27A

When I increase the load more than 27A, output is decreasing gradually

290

54.05

32.5A

When I increase the load more than 30.5A, output is decreasing gradually

300

54.05

35A

 

310

54.05

35A

 

320

54.05

35A

 

330

54.05

35A

 

350

54.05

35A

 

360

54.05

35A

 

370

54.05

35A

 

 

Same circuit for battery connection, as per given below 

Vin DC

Vout

Iout

Remarks

270

54.05

24A

Battery is charging with 24A only

280

54.05

27A

Battery is charging with 27A only

290

54.05

32.5A

Battery is charging with 30.5A only.

300

54.05

35A

Output is fluctuating from 0A to 35A (ON/OFF)

310

54.05

35A

320

54.05

35A

330

54.05

35A

350

54.05

35A

360

54.05

35A

370

54.05

35A

 

Please help me to solve this issue.

I need to charge the battery with constant 35A, from 270VDC to 400VDC.

  • 0
    TI__Mastermind 25570 points

    Hello Bhushan

    The Infineon design looks good but it is for a general purpose PSU rather than a battery charger. The main difference is that the Infineon design uses the input current rather than the output current and the result is that you get a constant input current limit but the output current limit will be a function of the input voltage (Vpri*Ipri  = Vout*Iout)

    What you need to do is to add a second error amplifier. The first error amplifier controls the output voltage whenever the output current is less than the desired max rate charging current. The second error amplifier controls the output current at the max charging current whenever the output voltage is below the maximum battery voltage. 

    The PMP8740 reference design is a good example of how this can be done - the details are at - https://www.ti.com/tool/PMP8740

    but the basic idea is described in the document at.

    /cfs-file/__key/communityserver-discussions-components-files/196/5751.CI_5F00_CV.docx

    Please feel free to ask any questions.

    Regards

    Colin