DRV8432: why DRV8432 efficiency is only about 80%, how to achieve the 97%

Robin,

First, you have to know what the factors are affect the efficiency? For hard switch switching converter, the switching frequency, FET Rds_on, FET turn-on&off time, dead time; gate drive voltage, input/output voltage and inductor and current path resistance could affect the efficiency number.
DRV8432 has integrated the switching FETs. So, you don't need worry about the FET Rds_on, turn-on and off time and dead time.

Please set a lower switching frequency and a lower input voltage to see any change for efficiency. Also, the datasheet figure 1,2,3 can give some ideas about efficiency number. You could use those test condition as reference to check your setup.

Hi wang,

Thanks for your response.

as the customer said, he provide both the 12V and 24V input voltage, but the efficiency is always around 80%.

also I have the their schematic from customer, I find their external component parameter is a little different with our datasheet application circuit. maybe this can help analysis.

Could you provide your email to me? so i can share the schematic to you.

Regards

Robin Liu

Robin,

What PWM frequency do they set? Does the output voltage or current keep same when they change the input from 12V to 24V?
After you have those info, you can put the cursor on my logo and send me an e2e private message to attach the schematic.

Hi Wang,

the PWM frequency is 60kHz.

Please refer to the test report from customer 

     Vin（V）         Iin（A)              Pi（w)          Vo（V）        Io（A)           Po（w)       efficiency 

      24.2                  8.2               198.44             20.1               7.8               156.78            79%

      24.25                5.7                138.23             16.5               6.5                107.25           77.6%

       24.28               3.4                82.55                12.6              5.0                63                76.3%

 Regards

Robin Liu

Hi Wang,

I send you the customer schematic, please help analysis. thanks

Robin,

Yes. The efficiency is low. I am checking the schematic in your private message. To understand the efficiency, please check the DC losses in the FET and inductors first. And then, measure the switching node waveform to check the dead time...

Hi Wang,

Thanks.

So could you help go more details to describe how to test the losses in the FET and inductors? by my understand, just test the voltage drop upon this device?

Regards

Robin Liu

Robin,

First calculate the DC loss, find Rds-on and DCR value. And then, use I^2 * R to calculate the DC loss.
And then, check the switching waveform to see if any abnormal condition, such as: turn-on time too slow or high side and low side FET shoot through...

Hi Wang,

it's OK. once the customer has some update. I'll send to you. Thanks.

Regards

Robin Liu