Hr1000a light load

DC-DC Power Converters
1

I am designing a power supply with input 180-260vac (no PFC). Po= 180w, 36V. using HR1000A. When under light load 0-300mA, it makes a sound. I measured it and it goes into burst mode. So how can that sound disappear. Rfmax = 1k8, Rfmin = 13K, Css = 2.2uF, CT = 470pF, Rss = 3k3. Fr ~ 90kHz. Cr = 56nF, Lr = 50uH.

Thank you.

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2

Hello,

In general, there are two ways that you could reduce the audible noise from a resonant half-bridge like the one you are using:

  1. If you are able to adjust the input voltage of the system to optimize the output voltage if you have this kind of flexibility, this could reduce the audible noise.
  2. Designing and choosing capacitor with an appropriate Q factor (somewhere between 0.34 and 0.5) can prevent inrush currents during start up and prevent voltage stress that can cause audible noise.