AN11486_15 Datasheet, PDF (43/53 Pages) NXP Semiconductors – GreenChip SSL8516T PFC and flyback controller

NXP Semiconductors
AN11486
GreenChip SSL8516T PFC and flyback controller

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Fig 28. Minimum frequency in QR mode
The equation for the primary flyback inductance is:
L_{pfb} =
-----------------------------------------------------------------------------------------------------¹-------------------------------------------------------------------------------------------------------



2_-----_---P_{----o----m----a--x------}_---f_{-f-s-b-w-----f--b----Q----R----m----i--n--}



----------¹-----------
V_{busmin}
+
-_N----_f-¹_b---_V----_o-_
+
f_{swfbQRmin}



2
C_{dfb}
(44)
Where:
• f_{sw(fb)QR(min)} minimum flyback switching frequency in QR mode
• _fb is the flyback controller efficiency, typically 0.95
• V_bus(min) is the expected minimum bus voltage
• N_fb is flyback turns ratio N_p(fb)/N_s(fb)
• V_o is the output voltage
• P_o(max) is the maximum output power
• C_d(fb) is the total capacitance on the drain of the flyback switch
To ensure that the PFC is on at P_o(PFC)swon, the L_p(fb) must not exceed the value L_p(fb)max
when the auto PFC on/off function is used (See Section 6.6).
L_{pfbmax} =
----------------------------------------------------------------------------------------------------------------¹-----------------------------------------------------------------------------------------------------------------



2_-----_---7_---3_-----k_---H_-----z_----_---fP_{-b---o----P---F---C-----s---w---o--n-}

 ----------------------¹-----------------------
v_{mainsrmsmin}  2
+
------¹--------
N_fbV_o
+
f_{swfbQRmin}



2₍₄₅₎
C_{dfb}
AN11486
Application note
All information provided in this document is subject to legal disclaimers.
Rev. 1 — 17 July 2014
© NXP Semiconductors N.V. 2014. All rights reserved.
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