boost-buck regulator

Discussion in 'General Electronics Chat' started by Steyn01, Jul 25, 2010.

  1. Steyn01

    Thread Starter New Member

    Jul 25, 2010
    1
    0
    I need to build a regulator which will give a constant output of 12volt DC at 4amps. The input of this regulator vary between 10 and 14 volt. Do anyone know of an boost-buck IC that is capable? Any advise is welcome.
     
  2. timrobbins

    Active Member

    Aug 29, 2009
    318
    16
    Are you planning on a simple buck-boost circuit config? Have you settled on whether you want to operate in DCM or CCM? What manufacturers have you checked out, and do you want to stick with a common IC (eg. in leaded DIP) or are you going smt?

    CIao, Tim
     
  3. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    Linear Technology's LT1268/LT1268B can handle up to 7.5A.

    Attached is a simulation of an LT1268B used in a flyback configuration, input at 10v, output 12v, 4A. Efficiency isn't great when input is 10v, but improves when the input voltage is higher. There is nearly 9W power dissipation in the switching regulator itself; you would need a large/efficient heat sink.

    You would have to custom wind a toroidal transformer.

    L3/C4 are an optional output filter. Without those components, you will have approximately 300mV p-p ripple @ 150kHz; the filter reduces it to 8mV p-p.

    If you didn't mind the output polarity being opposite, you could use a buck-boost-inverting configuration. See the LT1170 datasheet for the configuration, available on Linear Technology's site.

    The simulation was created using Linear Technology's LTSpice, freeware available from Linear Technology. Google is your friend.
     
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