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[SOLVED] Do The Input And Output Capacitors Effect Efficiency In Switching Regulators

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Zak28

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Would increasing the input and output capacitances were the load is~2mA @ 25v and input is ~8v prolong the battery life?

For this switcher View attachment MT3608.pdf
 

Hi,

Theoretically yes, but it's only marginal. I don't think it's worth it.
I expect far less than 1% prolong time.

Klaus
 
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    Zak28

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Hi,

Theoretically yes, but it's only marginal. I don't think it's worth it.
I expect far less than 1% prolong time.

Klaus

Is this largely due impart MLCCs being leaky?
 

Hi,

I expect the ESR loss is higher than the leakage loss.
But I did not calculate it ...

Btw: without knowing voltage and current waveforms and exact part names calculation is impossible anyway.

Klaus
 
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    Zak28

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Hi,

I expect the ESR loss is higher than the leakage loss.
But I did not calculate it ...

Btw: without knowing voltage and current waveforms and exact part names calculation is impossible anyway.

Klaus

Wouldn't the ideal method to reduce ESR be to break up the recommended 22uF from switcher datasheet - into 3x 10uF capacitors thereby reducing ESR?
 

Input filter capacitor ESR is a big deal in low voltage
POL buck converters. The capacitor sees current
equal to IOUT - charging during output switch "off"
interval and discharging during "on" interval. So every
electron you throw to the output gets dragged across
the input filter cap ESR, twice. IIN of the DC-DC power
stage is a square wave current, and in-the-moment
on high fSW converters, little of it comes from the
power source, most of it from the close-in decoupling.
The less input voltage ripple you see, the more true
this is.

Output filter only sees the output inductor ripple current
so its ESR matters a lot less to efficiency. ESR and ESL
are however both key to minimize load-step deflection
in the interval between application of the new load, and
the control loop coming around.

At 2mA however I'd bet it's all about switching losses
and not so much either filter.
 
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    Zak28

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