- #1
victorb
- 12
- 0
Hello, I'm a newbie for this forum, and I don't have much practical experience on SMPS too. I found this forum when I'm searching for my solution from internet.
My Circuit:
I'm using a simple buck converter:
Vin: 24V
Vout:3.3V
Iout: 1.5A (dynamic load)
The loading is running in PWM control, that means sometime it will draw around 1.5A and sometime it will draw around 0.05A, the PWM's frequency is about 250Hz.
The converter is fine when I'm running it at fully ON (100% duty-cycle) and fully OFF (0% duty-cycle).
But when I'm running it from 30% to 90% (duty-cycle), I can hear some audible noise (humming) clearly from the circuit.
As I didn't hear the noise at fully OFF mode, so I think DCM is not the reason.
I tried to remove the buck converter's inductor, and plug in a 3.3V at the converter output directly, then the noise disappeared, so I think the noise is from the converter circuit.
I tried to replace the inductor with another brand and bigger size (higher current rating) inductor, the noise seems reduced slightly (the original inductor's current rating is about double of the converter's output current already), and both of them are shielded inductor with EPOXY potted already, so more EPOXY may not be helped.
Anyone can share some experience knowledge with me on how to solve this issue?
And any reply will be appreciated
My Circuit:
I'm using a simple buck converter:
Vin: 24V
Vout:3.3V
Iout: 1.5A (dynamic load)
The loading is running in PWM control, that means sometime it will draw around 1.5A and sometime it will draw around 0.05A, the PWM's frequency is about 250Hz.
The converter is fine when I'm running it at fully ON (100% duty-cycle) and fully OFF (0% duty-cycle).
But when I'm running it from 30% to 90% (duty-cycle), I can hear some audible noise (humming) clearly from the circuit.
As I didn't hear the noise at fully OFF mode, so I think DCM is not the reason.
I tried to remove the buck converter's inductor, and plug in a 3.3V at the converter output directly, then the noise disappeared, so I think the noise is from the converter circuit.
I tried to replace the inductor with another brand and bigger size (higher current rating) inductor, the noise seems reduced slightly (the original inductor's current rating is about double of the converter's output current already), and both of them are shielded inductor with EPOXY potted already, so more EPOXY may not be helped.
Anyone can share some experience knowledge with me on how to solve this issue?
And any reply will be appreciated
Last edited: