Why the efficiency of Boost converter is low at light load

mpig09

Hi all:

I study a boost converter datasheet, and I found the efficiency is low (< 70%)
when the output current is small (10mA). But the chip is feature is low quiescent current,
so it is let me confused.


Could anyone help me?


Thanks.


mpig

mercybucher

1. how to defined the quiescent current? Is there any switching? or just the IDLE cycle?
2. the efficiency is mainly depending on the conduction loss and the switching loss. quiescent current typically has tiny contribution.
3. could you do a farther research, does the chip enter PSM/PFM when the loading is 10mA?
does the chip using sync control?

mpig09

Hi mercybucher:

1. how to defined the quiescent current? Is there any switching? or just the IDLE cycle?
==>quiescent current Definition : No load and No switch.

2. the efficiency is mainly depending on the conduction loss and the switching loss. quiescent  
   current typically has tiny contribution.

3. could you do a farther research, does the chip enter PSM/PFM when the loading is 10mA?
   does the chip using sync control?
==>the chip using sync control and it uses fixed-frequency PWM mode, so I think the chip is
      still in PWM mode when loading is 10mA.

Thanks.
mpig