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LM2623 Efficiency at 10, 12, & 14V DC

R11
Expert 1485 points
Other Parts Discussed in Thread: LM2623, TPS61093, PMP

For the LM2623 - DC/DC Boost Converter,  I am doing some battery life calculations and would like to know the efficiency of this convertor with a load of 5 mA at the output voltages of 10, 12 and 14 VDC. 

Because this will be a battery operated device the Vin will vary from around 3.2 volts down to 1.8 volts. (Input source = 2AA batteries in series)

I was only able to find one graph for efficiency on the LM2623 data sheet.  That was “Efficiency vs. Vin at Vout = 5 volts”.

  • 0 in reply to Jeffery Pfarr
    Prodigy 5 points

    At this low power level, with 5mA of current, and very low input voltage 2xAlkalines, circuit parasitics play a large role in determining efficiency.
    These parasitics wouldn't be modeled very well in most simulators.
    Parasitics are worse in an inductor based switcher, much less in a charge pump.
    The Alkaline battery also has a very high ESR which lowers overall efficiency.

    Another way to look at it, 5mA at 10V is only 50mW, so at 50% efficiency it takes 100mW to make 50mW.
    So look at the power loss that can be afforded in the system.

    Low current auxiliary voltages are better suited to be derived from other switchers in a system.
    Coupled inductor bucks, charge pumps off bucks, are some examples.

    PMP5587 is a 5V input to 14Vout at 100mA using TPS61093..
    http://www.ti.com/tool/pmp5587 
    TPS61093 runs down to 1.6V, so this PMP could be tweaked for lower input and various Vout's.
    The efficiency curves stop a 40mA but you can see the efficiency is dropping fast at low Iout.