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UCC28064A: Could UCC28064A work normally in DC input voltage.

Part Number: UCC28064A
Other Parts Discussed in Thread: UCC28064

Hi TI

Could UCC28064 work normally in DC INPUT?I have tested UCC28064A EVM-004 IN DC 200V input,but it works instability。Just like the picture as below,CH1 GDB;CH2 GDA;CH3 Vout。It seams restart  in startup。Why it happens.Thanks.

  • Page 14 of the datasheet, the block diagram shows VINAC detects peak to set up internal gain. If DC input, there will be no reset, a proper gain may not be set up. But if your DC input voltage is with narrow input voltage range, say 10%, it is ok to use. If > 10%, then the gain may not be set up correct, then not able to provide correct output, particularly full output power. 

    Based on your test waveform, it looks if you apply an external 13V bias to J1 on the EVM, the startup should work ok.

  • HI

    Could you please explain the peak VINAC voltage detect function in detail. What is"no reset"mean. If I want to use in DC input voltage , the DC input voltage should be 10% ripple?

    The test waveform is under 13V bias to J1,it seams abnormal. Tks.

  • VINAC reset by AC voltage zero crossing so to help adjust the device internal gain to make correct control. The DC input voltage does not have zero crossing so the device cannot adjust its internal gain which can result on incorrect control.

    In your case, you may test EVM with AC voltage to make sure the board still works ok. After confirmed, you can test with your DC input voltage. If the EVM cannot work on you DC input, then it cannot work. In nature, this device requires AC zero crossing to work properly.