TPS55340-Q1: Circuit design to operate high voltage with light load current

Part Number: TPS55340-Q1

Dear experts,

I wanna design Boost circuit to operate Piezo speaker (that has light load)

The input voltage range is from 5V(specific backup battery) to 16V(vihicle battery),

and output voltage should be set to 28V at 20mA(load current of piezo speaker and driver).

The problem is, when I simulate using by WEBENCH, the inductance value is vety huge (above 100uH~1mH).

Should this big inductor be applied for this circuit? Can I use smaller one? (about 10~47uH)

What problems can be caused by using smaller inductors (about 10 to 47 uH)?

for reference, switching clock will be set under 1.2MHz since we are not using external cynchronous clock.

Thank you.

  • Hi Seungan,

    I believe webench is selecting the inductor with a fixed current ripple ratio (e.g. 40%). As you have a very low current, this will result in huge inductance.

    You can use a much smaller inductance. The converter may operate in DCM.

    You need to take a look at the inductor loss, efficiency and the output ripple. If they are still good, you can use a smaller inductor.

    Best Regards,


  • Thank you for your reply!!