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UC1825 for synchronous buck converter

gG
Intellectual 915 points
Other Parts Discussed in Thread: UC1825, TPS50601-SP, TL594, UC1843, UC2950, UC1707-SP

Hi all,

Can i use UC1825 PWM controller IC for synchronous rectifier buck converter?

Can i drive its error amplifier output externally to achieve CC mode compensation to CV mode compensation networks?

Best regards.

  • 0
    Intellectual 915 points
    Hi all,
    Can anyone help me with this.
    Thanks
    Best regards,
  • 0
    TI__Expert 7445 points
    gG,

    1. Is your application for space, thus you need Radiation hard devices?
    2. what is your input / voltage and output current for the synchronous buck application. Note there is TPS50601-SP synchronous buck that is space qualified that you may consider for your application.
    3. What is your target efficiency for synchronous buck?
    4. For UC1825 yes you can configure the part to operate in CC and CV mode that would be typical for battery charger application.
    5. Is your application for battery charger?
    6. Configure the internal E/A as unity gain configuration.
    7. you can use an external E/A dual package and configure one for constant current operation, with its compensation and 2nd E/A for constant voltage operation with its compensation. Diode Or the two E/A and feed it into the NI pin of UC1825.
    8. See datasheet of TL594 for reference where the two E/A are internal to the device.
  • 0 in reply to Ramesh Khanna
    Intellectual 915 points

    Dear Ramesh,

    1.Yes and we need rad-hard ICs.

    2. 100V input, 50-85V output, at CC mod 5A output current. By adding additional componenets to drive mosfets , we may use TPS50601-SP.

    3. For above specifications, target efficiency is %93.

    4.Can i use UC1825 for synchronous buck converter application?

    5.Yes, so we need CC to CV mod transitions at control loop

    6. How can i do that? By connecting inverting and non-inverting pins to ground and drive its output from external compensations signals suitable?

    7. At this mode,will i connect internal reference to inverting pin? Therefore, there will be no need to drive internal error amplifier from external E/A. Am I right?

    8.Yes, but it is not satisfactory to be able configure external E/A voltage and current compensation loops. There is no space qualified PWM IC that has two error amplifiers in it at TI products- am I right?

    Looking forward to see your response.

    You can get contact with me by e-mail.

  • 0 in reply to gG
    TI__Expert 7445 points
    gG,

    1. TPS50601-SP is only rated for Vin = 6.3V and not for high voltage.
    2. Short answer for (4) Can I use UC1825 for synchronous buck converter application ?
    Is yes. however it will require discrete drivers with proper delay to ensure that you do not get into shoot thru issues.
    3. It will require that you take the two output pulses and couple then thru pulse x-fmr and then full wave rectify them to drive the high side MOSFET.
    4. Take the two output pulses and add then and invert then to drive the bottom mosfet.
    5. you can also use UC1843 with discrete drivers to make synchronous buck thing that you have to be concerned about would be to ensure that there is adequate delay added to prevent shoot-thru.
    6. Looking thru the TI portfolio check out UC2950 and UC1707-SP that is bipolar based drivers.
    what is your email? or you can email me at
    r-khanna@ti.com