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LM5036: Isolated 600W DC-DC Converter Controller Request

William Mcknight
Intellectual 380 points
Part Number: LM5036
Other Parts Discussed in Thread: UCC28251, UCC27712, UCC28C45

Hello,

I will prequalify this by saying I am fairly new to using high power-related IC's, so any and all advice (as well as white papers or articles) are appreciated.

I have converted my 2003 Mini Cooper S to Electric, and the vehicle runs great. I unfortunately though bought a DCDC converter that has too high of a low voltage cut out, so this presented an excellent opportunity to build one. The application is that this converter is taking over the functionality of what an alternator does in a standard vehicle, charges the 12V lead-acid battery while sharing the low voltage load.

I have been studying a two-switch forward topology, so if I can use that, then that would be preferable; otherwise, a half-bridge or full-bridge topology is where I would like to go next. I want to stay away from an LLC resonant topology as I believe it is a more complex topology to work with.

I was recommended the LM5036, but I would like to explore other topologies (as noted above), and if nothing else fits my requirements than an explanation as to how to use this with higher input voltage would be appreciated.

My specifications are:

Power: 600W

Full load efficiency: 90+%

Vin range: 122 - 94/93 (VDC)

Vout: 12V@50A to 13.7@0A

Wide Switch Frequency range that will include: 100kHz - 500kHz

Desired Control Method: Peak Current Mode Control

I would like light load efficiency increase features, and EMI reduction features ZVS/ZCS if possible.

The under-voltage-lockout must be programmable through hardware/software, as 90VDC needs to be an absolute minimum.

If more information is needed please let me know.

Thanks,

Will

  • 0
    TI__Genius 9790 points

    Hi, Will

    First of all, LM5036 support the application with Input voltage <100V.

    I recommend Half bridge with UCC28251 to support your request. You can find detail document of UCC28251 through below link.

    https://www.ti.com/product/UCC28251

    Regards,

    Yunsheng

  • 0 in reply to Yunsheng Qu
    Intellectual 380 points

    Hello Yunsheng,

    Thank you for the suggestion, I will have to look more into the IC to see if I have any questions on it. While I am comparing IC's, hopefully, you can clear my confusions up below.

    Within the LM5036 documentation, there is a subsection (8.2.2.4) that briefly talks about when Vin>100V. I would greatly appreciate you going over design considerations and potential idea's with respect to the comment, "100V-rated internal circuit blocks, including VCC start-up regulator, auxiliary supply and half-bridge gate drivers, need to be bypassed, or powered from a reduced voltage".

    Seeing the zener-transistor regulator is easy to understand, but what could be suggestions with respect to the auxiliary supply or half-bridge gate drivers?

    Regards,

    Will

  • 0 in reply to William Mcknight
    TI__Genius 9790 points

    Hi, Will

    Auxiliary supply is from auxiliary winding of transformer, you can refer to below diagram.

    Regarding to High voltage half bridge gate driver, UCC27712 is good choice.

    regards,

    Yunsheng

  • 0 in reply to Yunsheng Qu
    Intellectual 380 points

    Hello Yunsheng,

    I am having a hard time figuring out the auxiliary supply. VCC and SW_AUX are listed as an input, yet when you look at figure 33 SW_AUX to me looks like it is pwm driving the auxiliary supply transformer. If it isn't, can you please explain to me how this portion of the circuit works?

  • 0 in reply to William Mcknight
    Intellectual 380 points

    Also, the datasheet says around 800uA's gives 0% duty cycle, but I can't find a graph showing the comp current mapped to duty cycle. How do you design for this?

  • 0 in reply to William Mcknight
    TI__Genius 9790 points

    Hi, Will

    1. UCC28251 can support high to 400V input application.

    2. In LM5036, VCC/BST_AUX/SW_AUX/FB_AUX forms a Fly_Buck converter, are used to generate auxiliary voltage for other circuit in primary and secondary side if needed. HSG and LSG is the gate driver signal for Half bridge for main power output. 

    3. If you want to apply >100V with LM5036, the VCC and auxiliary voltage in primary and secondary side should be generated from another converter which can handle >100V, such Flyback with UCC28C45.

    4. If the current flow into COMP pin >800uA, ducy cycle is 0, if the current =0, duty cycle is maximum. so you just make sure the current flow into COMP pin less than 800uA,

    regards,

    Yunsheng

  • 0 in reply to Yunsheng Qu
    Intellectual 380 points

    Hello Yunsheng,

    I made another thread asking the same question so please ignore, I did not know if you were going to reply to this.

    1) Looking into the UCC28251, why can this particular converter be used up to 400VDC on the input, and not the LM5036 be used like this https://i.imgur.com/qYJkRoe.png? If the primary FET's are being driven by an isolated gate driver, why can't the input be 1000V? or 2000V? How should VDD be supplied for the UCC28251, through an auxiliary winding of the main transformer?

    3) With the UCC28C45 the VDD limit is 20V, how can this be used for >100V's?

    Regards,

    Will

  • 0 in reply to William Mcknight
    TI__Genius 9790 points

    hi, Will

    Since you made another thread, I close this thread. If you have further question , you can send to yunsheng-qu@ti.com 

    regards,

    Yunsheng