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Power Factor Preregulator

Other Parts Discussed in Thread: UCC28050, UCC28051, UCC38050

Hi All,

Need help with a suggestion for a power factor circuit or module that will work on input voltage of 120VAC +/- 20%,  47-65 Hz

Typical load : 20 to 100 Watt (150 Watt)

Cos ( Fi) >= 0.9

The current power supply with 45 Watt Load ( and internal 12VDC power supply) is giving Cos (Fi) about 0.5 , any suggestion for improvement?

Thanks, Dov Rossitzan  =516-487 5314 X 125 






  • Dov,

    Typically customers would consider the UCC28050 or UCC28051 for your power range. Take a look at the information on our web site and see if it is of interest.
  • Brain,
    Thanks for your feedback, have few questions:
    1-Need a circuit that can deliver 20 to 150 watt-Figure 19 of the data sheet is talking about 100 W only
    2-Need Bill of Material of ALL parts numbers of the components (at Figure 19 [ missing L1 diodes etc] or other circuit TBD) that can handle 20 to 150 Watt
    3-What is the minimum Power Factor that this circuit will " deliver "
    4-Where is the power supply of Vcc Figure 19 , is there is a circuit or an application that do no need additional Vcc supply ? (like in Figure 20 Rup, Rb etc)
    5-Figure 18 is talking about frequency of >>120 Hz our frequency is about 60 Hz will circuit of Fig 19 match to our need?
    6-CCM, DCM & CRM what are the changes needed in circuit / examples of schematic for each of this modes . any application notes?
    7-What about a design example or application note that will match our needs .

    Thanks-Dov Rossitzan , Email : 516-487 5314 x 125
  • Dov,

    Q1-Q3: There is no reference design for your specific application at 150 W. Figure 19 in the datasheet is actually a copy of the "UCC38050 Evaluation Module: 100-W Universal Line Input PFC Boost Converter" and the User Guide has the BOM. Figure 2 in the User Guide shows PF > 0.9 for different input Voltages and only down to 25 W load.

    Q4: VCC is sourced by the extra winding off the boost inductor L1. It is the circuit D6/C7/C6/R10/R6/R12

    Q5: Figure 18 is referencing the Operating frequency >> 120 Hz which is the switching frequency of the PFC boost stage. This circuit works with 60 Hz and 50 Hz AC voltage inputs.

    Q6: The controllers I recommended you to look at operate as Transition mode (also know as boundary-mode or critical conduction mode) only. It will not operate in DCM nor CCM modes and there are no application notes on these other operating modes specific to the controllers I recommended.

    Q7: There is no specific design example for your design requirement. A 350 W implementation is found in the PMP9531 reference design (not an EVM so cannot obtain the hardware) at but it is a 2 stage design so ignore the LLC isolated converter.
  • Brain,
    Thanks for the answers, have few more questions:
    1-Do we have any data about V out DC as a function of Vin AC ? at different loads ?
    2-We need that the output voltage will be less than 370 VDC ,
    What are the components at the UCC38050 circuit that have to be changed ?
    3-What are the components that have to be changed to have output power of 150 Watt?
    4-What will be if the output load will go down to zero will the circuit still supply Vout DC , with a less good power factor ? or what TBD?
    5-What are the physical dimensions of the module ?
    6-What is the efficiency of the circuit ? at a given load ?
    7-What is your direct phone number can we talk - if needed ?
    Thanks-Dov Rossitzan , Email : 516-487 5314 x 125
  • Dov,

    We do not have a design that I can share or use to address all of your questions. My best suggestion is to work through the application note titled "UCC38050 100W Critical Conduction (PFC) Reference Design (Rev. A)" at and complement your analysis with the datasheet.