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UCC24630: Can ucc24630 be used with UC3843 in fly-back?

Part Number: UCC24630
Other Parts Discussed in Thread: UC3843, , UCC24636

I am working with a power supply which input is 28V and output is +5V and -5V . Each channel of the output is 12A. I am planing to use the fly-back with two output windings. The question is :

(1) Is it suitable to use flyback topology ?

(2) the output current is  a little bit ,can you suggest some solutions? The SR or others? 

(3) The flyback is designed in CCM mode,as the UC3843 is easy to get in our company , can I use it with UCC24630? and which type mosfet should be selected?

  • Hi, 

    thanks for asking. My opinions are as below.

    1) Yes, it is okay to use flyback topology.

    2) SR would be a good solution since output current is high.

    3) UCC24630 is a SR controller based on voltage-balance approach. It is okay to be used in CCM operation. Also, UCC24630’s VDD(on) is 4V around. It is also meet your output spec if you would like to supply VDD from output voltage directly. However, please note the DRV voltage of UCC24630 follows VDD if VDD is lower than VPMOS (10V). Thus, you need choose logic level MOS or a MOS which define RDS at Vgs <5V. Besides, a smaller Qrr of MOS is also preferred since the flyback may operate is deep CCM.

    Just remind you may pay some attention to deal with thermal issue of transformer because the power rating is 120W, and current of primary and secondary side are high. 



  • Thanks for your reply. I have further some questions.

    1)  UCC24630 can be replaced by UCC24636?

    2) Does UCC24630 has some special demand for the primary flyback control. 

  • Hi Zixuan:

    Please check the reply as below. 

    1)  UCC24636 is only for DCM and transition mode operation. It does not support CCM. Also, it only support max frequency is 130kHz. UCC24630 supports 200kHz. Hence, if you are going to design a CCM flyback or switching frequency is higher than 130kHz.  UCC24636 is NOT able to replace UCC24630.

    2) UCC24630 uses voltage-balance control and it control the dead time based on previous cycle. Thus, please make sure the switching frequency is fixed when the converter works in CCM.