MC33063A: Low conversion efficiency

Timsen

Other Parts Discussed in Thread: MC33063A

art Number: MC33063A

Dear all：

I'm using MC33063A with input of 10~35V and output of 5V.In the actual test, when the input VIN=24V and the load is 5V/300mA, the input current is 110mA. The conversion efficiency is 5*0.3/(24*0.11)=56.8%

But the data sheet says conversion efficiency is 83.7. Why is the result of my test 56.8%? Any Suggestions?Here is my schematic

7447452221.pdf

over 6 years ago

0 Jasper Li over 6 years ago

TI__Mastermind 46905 points

Hi Timsen,

what is the part number of the inductor? make sure the inductor doesn't saturate.

the layout is bad. please following this application note to modify the layout http://www.ti.com/lit/an/slyt614/slyt614.pdf

0 Timsen over 6 years ago in reply to Jasper Li

Expert 1660 points

Dear Jasper:

thanks for your reply! Please see the attachment below for the inductance parameters.

the layout is bad?Can you tell me more about it?My PCB layout is defined according to the data sheet!Would your link reference be better?

1323.7447452221.pdf

0 Jasper Li over 6 years ago in reply to Timsen

TI__Mastermind 46905 points

Hi Timsen,

as suggest in the datasheet, the input capacitor loop and output loop between the components and IC should be as small as possible.

however, the your layout, the GND node between the input/output capacitor and the IC GND is very long.

also please make sure the D4 and D5 doesn't impact the efficiency measurement.

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MC33063A: Low conversion efficiency