PMP4435: Bias winding for Primary and secondary supplies

Johny, hello and thank you for your interest in Texas Instruments. For future inquiries and perhaps faster responses, let me suggest that when sending in multiple questions, send secondary questions by simply hitting "reply" to the original E2E message thread. This will ensure that when the thread gets assigned (in this case to Ryan Manack who has already answered one of the questions) will get immediate notification of the next question...……….instead of being sent back to the E2E queue for moderation and assignment again. Just providing what I hope is a helpful hint. Good news is Ryan has all your questions and you should be getting a response here soon within the next 24 hours.

Best Regards
J. Fullilove
Reference Design Operations

Hi Nesh,
In my suggestion is "not suitable". Because we need the initial start up bias voltage to wake the controller up. If the controller not going to normal operation mode. It don't have a bias voltage. It is logical sequence for the start up. So we do need a additional controller for start up bias voltage first, then, wake up the UCD3138, then, start the main power.
Regards,
Richard

Hi Richard,

Suppose for the initial start up we can keep a LDO, for (LM5113TME) Primary Gate Driver and UCD3138 which is on the primary side, then once the converter reaches normal operation the bias winding of the planar transformer can supply for the UCD3138 , and similarly another winding for secondary bias to provide supply for secondary side gate drivers. This way can we reduce additional circuit components of LM34927.

By adding this additional bias winding in the main planar transformer is better option or more complicated compared to use of additional components like LM34927.

Regards,
Nesh

Hi Nesh,
Sure you can done it if the controller in primary side and pre-bias from LDO. But I think it is more complicated if adding this additional bias winding in the main planar transformer than using LM34927. Because of the disadvantage from primary side control to secondary side(In additional the LDO loss when switching is off too).
If you put the UCD3138 to primary side, it need a additional OPAmp/TL431/Optocoupler... to get remote sense output voltage(RS+, RS1). Problem is, seems don't have a suitable voltage sensing method in digital controller if you want to isolated between controller side and target regulate output side. Especially if need to have voltage accuracy and transient respond.
I think peripherals should be more and complex.
Regards,
Richard