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Isolated DC DC Converter

user4696155
Prodigy 35 points
Other Parts Discussed in Thread: UCC28911, UCC28910, UCC28704, UCC28740

I have 3 considerations about my design.

Vin = 60 - 90 V

CC and CV or only CC output

Isolated Voutput

Is there any dc dc converter which has these features ?

  • 0
    TI__Genius 9130 points
    Can you provide a few more details about your requirements & spec?

    - Vout?
    - Load current & power?

    Thanks,
    Bernard
  • 0 in reply to Bernard Keogh
    Prodigy 35 points

    I am striving on Battery Management System at discharge situation. I need a balacing circuit that charge the battery. For that reason, 

    the balancing circuit must have float charging. In a short, the circuit have constant current and constant voltage feature.

    Constant current: 2.7 A

    Constant Voltage: 4.2 V (boundry voltage of lithuim ion battery. If ıt is not 4.2, battery overcharges and damages.)

    Load: Lithuim ion battery (light load, ESR = 133 mOhm for we use battery)

    Power: Pout = 14 W (about), higher power better

    Other requirements:

    Vinmin = 60 V

    Vinmax = 90 V

    Converter Type: Isolated

    I am studying on UCC28911 and UCC28910. Do they satisfy our requirements ?

    Also, is there  a diffirent alternative ?

  • 0 in reply to user4696155
    TI__Genius 9130 points
    For low input voltage 60-90 V, the UCC28910/1 would not be suitable - they are not guaranteed to start below 100 V, and the internal FET Rdson would be too high - they are intended for offline AC-DC applications.

    However, you could consider the UCC28704 device and use it with an external FET. This device is intended for CV/CC operation. However, since it is PSR (primary-side regulation), it does not use opto feedback, and instead uses the aux bias winding for feedback. As a result, the CV and CC accuracy for output voltage and current regulation may not be good enough for your application - to be conservative, the CV/CC regulation accuracy could be up to +/-5%.

    You could also consider the UCC28740. This is a similar device, but it allows opto feeback to be used to get better CV regulation accuracy. This device also supports CC mode output current limiting, with the same +/-5% accuracy.

    The UCC28740 includes a HV startup pin, which is again intended for >100 V applications. In your case, you could leave the HV pin open, and instead use a startup resistor from the DC input voltage rail to the VDD pin.

    TI also offers a large selection of battery management IC's, which could be deployed on the isolated secondary side to manage the battery charging. The main power supply could then just be a generic Flyback to generate an isolated 5-V rail to feed the battery charger IC.

    I hope this information is helpful to you.

    Thanks,
    Bernard
  • 0 in reply to Bernard Keogh
    Prodigy 35 points

    Thanks for reply and advices,

    I saw this table in your site (Link: http://www.ti.com/product/UCC28911?keyMatch=ucc28911&tisearch=Search-EN-Everything), 

    and then I decided to make our project with UCC28911. After that, ı ordered even last day.

    Can you give an advise for Li - ion battery charger and  constant voltage flyback converter ? 

    For flyback requirements;

    Vinmax = 90 V

    Vinmin = 60 V

    Iomax = 5 A

    Vout = 24 V

    For battery charger requirements;

    Vin = 24 V

    Iout = 1.5 A

    Li - ion

    Thanks for everything