Flux walking in voltage mode half-bridge?

[grizedale]

Hi,

Page 4-7 of the following warns of flux-walking in half-bridge smps......

https://www.ti.com/lit/ml/slup126/slup126.pdf

Is this flux-walking stopped by adding a series capacitor in series with the primary winding?

the article states that if peak-current-mode control is used, then flux-walking is stopped by using a balancing winding and two diodes...........but am i right ion saying that when in voltage mode, adding such a balancing winding will just result in wild oscillation of the primary current waveform?

 

[technoqwerty123]

Hello,

Hi,
Is this flux-walking stopped by adding a series capacitor in series with the primary winding?

Yes this is true. The current direction alternates in the primary winding in the case of the half bridge allowing us to use the blocking cap technique to avoid flux walking.

I will think about the second question and let you know. However at first instance I believe that voltage mode control does not need to use this mid point voltage balancing scheme as the runaway mechanism is absent which unfortunately is the case as regards to current mode control.

Regards