Triple PFC with triple HiperLCS2
Posted by: treez
on
Hi,
We wish to do a 100-265VAC input PSU with 52Vout and 420W.
We need it to be fanless. Enclosure is metal with vent holes.
We wish to have a BCM PFC chip into the HiperLCS-2...and have three of such (BCM PFC + HiperLCS2) in parallel...and have a load share circuit on the outputs so that all three HiperLCS2's share the current.
Do you think this is feasible?
Also, is the HiperLCS-2 going to mean there is a limit to the total amount of capacitance connected to the output?
Hi treez,
May I inquire what is the purpose of doing three parallel PFC+LCS stage since parallel PFC+LCS is not ideal for a 420W project only. While paralleling PFC is already proven with reports, we currently do not have any design report of paralleling the LCS.
BCM (CrM) is feasible and is still available for valley correction feature of the PFC which reduces the input current distortion.
The total amount of capacitance is primarily based in the start-up behavior, below is a summary for your reference.
The HiperLCS-2 begins primary switching at a frequency approximately 1.5x the maximum of the selected switching frequency range. The switching frequency is ramped down quickly to build current in the resonant tank. Once the resonant tank achieves target current (IHB(IOVL)), the frequency is then indirectly regulated to maintain tank current at this level. The result at the system output capacitor, is equivalent to a very high-power current source. This results in a monotonic rise at the voltage on the output capacitor. The positive slew rate of the output voltage-rise will be a function of resonant tank and output capacitor values.
From start of primary switching, secondary should send wake-up command within 32 ms and hand over should occur to secondary control within 64 ms. Also during start-up frequency confirmation received signal should be received. If any of these do not occur, then error will be activated. May indicate excessive COUT, excessive load, or insufficient power delivery.
Another thing to mentioned is that there is still minimum COUT value to satisfy burst condition.
Thank you and regards