Hi,
I use MP8017 to generate a 12V backup power supply(PSR mode), which works in conjunction with the main power supply (9V - 30V). MP8017 already has a diode at the output so I think I don’t need to add an extra diode to implement oring function.
According to the datasheet, the MP8017 will continue to operate even under light load. I used an ADI PD chip(similar PSR mode) before which require a Zener as minimum load to maintain output stable. I didn’t see MP8017 has such requirement.
Could you please tell me what will happen when MP8017 output current close to 0. For example, MP8017 output current is close to 0 when main power is 24V in my application.
Welcome to MPS forums. When operating at low-load, MP8017 keeps the frequency consistent and does not go inactive which can prevent audible noise issues from the transformer. How is the main power supply connected with to the MP8017? What is the input voltage used at MP8017?
Hi Saquib,
Thanks for your reply.
I plan to use TI ideal-ORing controller to select main power(9V - 30V) or POE 12V power. The typical POE input voltage is 48V from Ethernet port which compliant with 802.3af.
MP8017 will keep switching but FB pin won’t get feedback voltage from secondary side because output diode is not conducting even when LS-FET stay off if main power is much larger than 12V. No changing current means no changing magnetic field, and thus no induced voltage will be generated, right?
I don’t know if there will be a problem due to the energy has no where to go. Could you please help me to confirm?
I didn’t quite understand the configuration. Can you share schematic or rough block diagram on how are you planning to power MP8017. Is it either with main power(9-30 V) or 12 V power from POE?
Thank you for sharing the block diagram. It is evident when the LM5050 turns off, the MP8017 will be in no load condition. For PSR, it is necessary to watch out for voltage spike at the output and I confirmed with our internal team that a dummy load or Zener will be required. For energy saving, you can also disable MP8017 by pulling the DET pin low.
We also have a smart diode controller which has similar characteristics to LM5050-1. Please take a look at MPQ5850.
