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WEBENCH® Tools/TPS55340: To use one step or two step boost from 3.3V input boost to 24V output

Jin Jiang
Intellectual 310 points
Part Number: TPS55340
Other Parts Discussed in Thread: TPS61500,

Tool/software: WEBENCH® Design Tools

Dear Sir/Madam,

I am driving a few strings of 8 LED and I need 24v output voltage. My input is Lithium ion battery and has a minimum voltage of 3.3V. My output current is 0.2 to 0.4A and I would like to have high efficiency for battery battery life. My question is should I use one step boost from 3.3V to 24V or should I use two step like 3.3V to 9V and 9V to 24V. The goal is to have better efficiency. Using webbench for tps55340. I got a design. But it seems to me it does not work at Vin of 3.3V to have a 24V output. As soon as the output require a current, even 100mA, the output voltage collapse to 10 to 14V.

Thanks.

Jin

  • 0
    TI__Mastermind 40080 points

    Hi Jin,

    Could you please share the sch with us? By the way, TPS55340 rarely used in the LED application, usually use TPS61500.

  • 0 in reply to Helen chen
    Intellectual 310 points

    Helen,

    Thank you for pointing me to another option TPS61500. I will look into the data sheet and prototype board.

    For the TPS55340, I am using TI prototype board TPS55340EVM-017. It is designed for 5V and up input voltage. Compared with the webbench generated schematic that I put Vin at 3.3V to 12V, the FB resistor are the same 187K and 10k for 24V output. The comp resistor/capacitor are different. I will change the comp and freq resistor to the webbench result.

    I still have the question here on for the 3.3V to 24V boost, when the output current is at 0.4 to 0.8A, how can I get a better efficiency? Whether to use one stage boost or two stage, 3.3V to say 8V first and then from 8V to 24. I am looking for a efficiency of 95%. Is this achievable?

    Thanks.

    Jin

  • 0 in reply to Jin Jiang
    TI__Mastermind 40080 points

    Hi Jin,

    95% efficiency can't be achievable with TPS55340. the efficiency will be around 85% since a rectifier diode will be used at the output side.