PMP22477: TPS23730_12Vout_51W_hardware design of Type1, Type2, Type3

Hi Ching-Fei,

The quad amplifier circuit regulates the maximum input power.  It can be useful when two converters are in parallel on two PoE ports and you want to get maximum power from each port.  When the converter with the higher output voltage reaches maximum input power, it will continue to provide the maximum input power allowed by the PoE standard from that port.  The parallel converter will continue to increase its power up to the maximum power allowed for the PoE port it is connected to.  If the load current is increased after both PoE ports reach maximum power, the output voltage will droop so that maximum input power is maintained on each port.

The input current through the primary sense resistor is filter back to its average value and a sample of the input voltage is also measured.  These two signals are added together and compared to a reference.  Once the reference is reached, the input power is regulated instead of the output voltage (the voltage loop and power loop are OR'd together).

The TPH and TPL signals are used to identify the maximum power from available from each PoE port to set the maximum input power regulation level.  This could also be done through software if a MCU is available.

Thanks, David

Hi David,

Thanks, the explanation is very completed.