how to design a boost converter by using LT1172

Discussion in 'The Projects Forum' started by xw0927, Dec 19, 2010.

  1. xw0927

    Thread Starter Member

    Dec 19, 2010
    hello all, I have a project to deal with the boost converter.
    I want to try to use the LT1172, however, I don't know how does this IC works. Could anyone help here??? I meant, I don't know how to put the parameter of those components like resistor, capacitor and inductor...

    My aim is from 12V to 45V... Tq, input source is Battery
  2. Wendy


    Mar 24, 2008
    This is the 3rd post on the subject you have done. One is enough. These are the rules here, please stop creating new threads on the subject. I have flagged the ones on this forum, a moderator will likely remove them very soon when they get on the site.

    Welcome to AAC, I hope you like it here. There are several forms of etiquette with forums such as these. Spamming is one, double (or more) posting is another, and hijacking someone elses thread is yet another.

    A thread started by you belongs to you. Someone else is not allowed to take it over with their questions, it is meant for your questions only.

    We are all volunteers, and this isn't a chat room. If you're query is not answered right away wait a bit, and repost in your thread, but don't start a new one.
  3. xw0927

    Thread Starter Member

    Dec 19, 2010
    Opss, so sorry about it. But, these 2 posts are different, ain't ?
    Although both are same related to boost converter, another is regarding the problem with inductor.
    I thought they are different, that's why i posted another new1 here...
  4. #12


    Nov 30, 2010
    Read this.
  5. SgtWookie


    Jul 17, 2007
    I haven't seen the other threads.

    What will the battery voltage range be? If a 12v lead-acid battery, that would be 14.5v (charging) down to 11.4v (100% discharged).

    What kind of output current do you need? Do you want the output to be isolated from the input?

    I used an LT1171 which has the same basic specs, only 2.5A out rather than 1.25A output current.

    Take a look at the schematic at the bottom of the 1st page of the datasheet; it's a boost converter using the LT1170. With 12v in, the LT1170 boost circuit will be limited to ~50W output, according to the graph on the right. An LT1172 would be limited to 1/4 that, which would be around 12.5W; so with 45v out, you'd get a max of 12.5w/45v =~ 277mA out.

    The regulator tries to maintain a constant 1.24v on the FB (feedback) input by switching the Vsw output.

    In the boost configuration, the output cannot go lower than (Input_voltage - Vf_of_D1.)