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UCC28951-Q1: EV charger station Design

Part Number: UCC28951-Q1
Other Parts Discussed in Thread: UCC28070, PMP8606, UCC28950

Hi,

I am also designing a Battery charger, for that i need to desig a PSFB using UCC28951-Q1. I just  want to ask is PSFB Using UCC28951-Q1 can give the CV/CI profile for battery charging.If the answer is yes. Then can you please suggest how should be the Control loop designed in reference to the Battery SOC.

Thank you.

  • Hi Digvijaysing,

    Thanks for your interest in UCC28951-Q1. Yes, you can implement a CV/CC charging profile. This is typically implemented as two feedback loops on the secondary. One controls the max output voltage, the other controls the max output current. This presentation provides a high level overview of battery charging:. . Page 5 shows the feedback structure necessary for CV/CC charging.

    Best Regards,

    Ben Lough

  • Hi Benjamin,

    Thanks for your reply on my query. i have refereed the document which you have send. But in that it is mentioned that the system goes in CV/CC Mode automatically, where as in my case i have to operate the system in CC/CV mode based on my commands to the system. i.e the system should operate in CV mode when i want to make it operate in CV mode and it should operate in CC mode when i want  to operate it in CC mode.So can you please suggest me how can i achieve that  using the same IC UCC28951-Q1.

    THANK YOU!!

    Best regards,

    Digvijaysing

  • Hi Digvijaysing,

    You would use the same structure but make the reference in the current control loop programmable through a MCU. You can set the reference appropriately to regulate the current across the sense resistor when you want CC mode. You can make the reference larger in order for the CV loop to take over when you want CV mode.

    Best Regards,

    Ben Lough

  • Hi Benjamin,

    Thanks for the reply on my query related to operating PSFB using UCC280951 in CC/CV mode..But again one query i have , is that as per the document you shared before, it is said that the lower error value at the output of both the error amplifier wins and then that signal is given to EA+ pin.Now who ever wins in both the case the signal given to the EA+ is in voltage form , so how it is going to generate the Constant voltage or Constant current profile at the output. Is there any logic in the internal circuit of the IC , that if the voltage at EA+ pin is in particular range then it will operate in CV mode and beyond or below that range the IC will generate the CI output.

    Thank you

  • Digvijaysing,

    The feedback circuit is what generates the CCCV charging profile. There is no logic inside the IC itself to generate a CCCV profile. When the battery charge is low, it will accept a large amount of current. The CC loop will regulate the maximum output of the converter to get CC mode. As the battery continues to be charged, the battery voltage will rise. Once the battery voltage reaches the max charging voltage (as set by the CV loop), the converter will regulate to the max charging voltage and the charging current will begin to decrease.

    Best Regards,
    Ben Lough
  • Dear Benjamin,

    Thanks for your reply.

    Do we have to connect Rsum to Ground when to operate in CC mode, and when to operate in CV Mode do we have to connect Rsum to Vref. 

    Just want to know does PCM and VCM mode play any role during CC/CV Mode.

  • Hi Digvijaysing,

    Please note that the control method of the converter (voltage mode control vs current mode control) refers to the control method. It is not the same as operating in constant current mode or constant voltage mode. Please note this distinction in nomenclature.

    You do not want to switch control method of the converter mid operation. You will likely want to use peak current mode control for an OBC application. Refer to slide 11 of this presentation:training.ti.com/.../how_to_design_multi-kw_converters_for_electric_vehicles_part_7_-_a_high_power_on_board_charger_design.pdf.

    Best Regards,
    Ben Lough
  • Hi Benjamin,

    Thanks for your replies on all my queries.Ill get back to you again if i  have any doubt.thank you once again.

  • Hi Benjamin,

    Can you suggest the idol test procedure to follow for the testing of PFC followed by PSFB Ckt using UCC28070 & UCC28951-Q1.

    your suggestion will be highly appreciated.

    Thank you. 

  • Hi Digvijaysing,

    Take a look at this design review as a starting point for your test procedure for interleaved CCM PFC::www.ti.com/.../slua479b.pdf

    For phase shifted full bridge take a look at PMP8606 as a starting point:www.ti.com/.../tidu621.pdf

    Best Regards,
    Ben Lough
  • Hi Benjamin
    Are there any PFC & PSFB TINA Simulation Module using UCC28070 & UCC28950. If so can you please share the link of that simulation module .

    Thank you.
  • Digvijaysing,

    You could take the individual TINA models and combine them. You can find the models on these pages:
    www.ti.com/.../toolssoftware
    www.ti.com/.../toolssoftware

    Best Regards,
    Ben Lough
  • Hi Benjamin,

    As per your suggested links for simulation of UCC28070 & UCC28950. I just want to know what is the use of pin IRIPA, IRIPB & F_KHZ in UCC28070 Transient model, this pin are not available in actual IC UCC28070.Can you please tell me while simulating UCC28070 Trasient model what connections to be done across this pins.

    Thank you.

  • Digvijaysing,

    IRIPA and IRIPB represent the ripple current. F_KHZ represents the switching frequency. The model is set up as an average model. These parameters are needed because there is no switching behavior for an average model.Please refer to this other E2E post:

    Best Regards,

    Ben Lough

  • Hi Benjamin,
    I have started to Test the PFC Board . When i remove the CT which is in Between the Inductor and drain of Mosfet the circuit performance the boost operation as per the calculations and as per given duty cycle, but when i connect CT the circuit stop performing boost operation and i get the same output voltage as applied to the input . currently i have removed the UCC28070 IC from the board, And driving the Mosfet through the external Pulse. Currently i am testing the circuit with resistive load. I am testing the boost converter individually .

    My queries are as follows.

    1) should i get the output voltage same as that of input voltage or it should get boosted when i connect CT?

    2)How should the CT turns ratio should be selected?

    Thank you.

    With regards,
    Digvijaysing
  • Hi Digvijaysing,

    If your output voltage is the same as your input voltage, then you are likely not seeing any switching action. This is not normal behavior. Do you have a schematic of your design you can share?

    Generally, a Nct between 50 and 200 is reasonable.

    Best Regards,
    Ben Lough
  • Hi Ben,

    Thanks for your reply .Actully i am giving DC supply to my PFC Circuit after Bridge rectifier.I have checked the switching .It is getting proper pulse at the Gate of the mosfet .I have tried to change the Load ,Duty cycle, switching frequency then also i am facing the same problem.I am getting the output voltage same as the input voltage. After connecting the Ct in between the Inductor and Drain of the Mosfet i am facing this Problem.I haved he same schematic for PFC that is provided in the application note of UCC28070.

    Can you give me any suggestion what might be the problem .Currently  i am not testing the PFC on AC Supply i am just giving the DC Voltage as an input to the circuit in the range of 12V - 24V, Load i have given as 220Ohm resistive load.I have varied the switching frequency from 50Khz to 100Khz.

    Below i have attached the TI PFC Schematic that i have refered for my Circuit.

    Thank you.PFC Schematic.pdf

  • Digvijaysing,

    What is your input voltage range and your output voltage setting? 12V-24V sounds too low of an input voltage.

    Best Regards,
    Ben Lough
  • Hi Benjamin,

    My actual input voltage is same as that is given in Application note of UCC28070 i.e 85V-265V AC input and output voltage to get 400V DC , i have designed my system for 3.3KW .but currently i was just trying to check the system at low voltage and low power by giving low DC input voltage of about 12V-28V DC instead of AC after rectifier.

    Thank You.

  • Hi Digvijaysing,

    You are likely hitting the peak current limit. Testing with 24V input and output voltage set to 400V would require a very high duty cycle. It is likely you are reaching either the max duty cycle or the peak current limit.

    Best Regards,
    Ben Lough