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UCD3138A: Flux balancing feature

Part Number: UCD3138A
Other Parts Discussed in Thread: UCD3138


Customer is comparing UCD3138A to XDPP1100 (link below) and has a question regarding flux balancing functionality.

1. Per my understanding, UCD3138A can achieve transformer flux balancing by setting EADC in peak current mode. Is it additionally achieved by PID filter? May I ask more detail on how to implement it? I thought the current mode control inherently was able to control the flux imbalance as the pulse is being terminated at the same peak current by adjusting the pulse width.

2. XDPP1100 supports flux balancing feature in voltage mode using PI filter. Please see in the application note below. I eventually wonder this feature can also be implemented using PID filters in UCD3138A.

Thank you for your kind help.

  • Hi, Ella,

    This is a good question. Peak current control can prevent flux from walking away and transformer saturation. At voltage mode control, when the flux is unbalanced, the transformer could be saturated after many cycles. But current mode can limit the cycle by limiting the peak current. Peak current consists of magnetizing current plus output inductor current. I think it can allow some degree of flux unbalance.

    UCD3138 also integrates flux unbalancing feature. It is can be configured from peripherals. See the feature: Flux and Phase Current Balancing for Nonpeak Current Mode Control Application. 

    Normally, for the full bridge, peak current mode is recommended and prevent flux unbalance.



  • Hi Sean,

    Thank you for additional description. May I ask which document are you referring to when you mentioned ; 

    See the feature: Flux and Phase Current Balancing for Nonpeak Current Mode Control Application. 

    I cannot find it in UCD3138A datasheet or

  • Ella,

    I sent you it to your email.