TEA19162T All information provided in this document is subject to legal disclaimers. © NXP Semiconductors N.V. 2016. All rights reserved.
Product data sheet Rev. 1 — 10 March 2016 6 of 30
NXP Semiconductors
TEA19162T
PFC controller
The exact start-up sequence of the PFC depends on the availability of start-up conditions
(brownin level, V
start(SUPIC)
of the PFC, and I
en(PFC)
).
Before t1, the SUPIC voltage is below the UVP level of the PFC and LLC. When the LLC
reaches a minimum supply voltage level (t1), the LLC pulls down the SNSBOOST pin to
disable the PFC.
At t2, the SUPIC voltage reaches the start level of the PFC converter. However, as the
LLC pulls low the SNSBOOST to below the PFC short protection level, the PFC is still off.
When the mains voltage exceeds the brownin level, the PFC resets its latched protection
by pulling V
SNSBOOST
to the V
pu(rst)SNSBOOST
level (t3). However, the LLC returns it to the
protection mode. When at t4 the SUPIC voltage reaches the start level of the LLC, the
SNSBOOST is released. The SNSBOOST voltage increases because of the resistive
divider which is connected to the PFC bus voltage. To ensure that this voltage is
representative of the V
boost
voltage before the system actually starts to switch, an
additional delay (t
d(start)
; 3.62 ms) is active before the PFC starts switching (t5).
Another important condition for the PFC start is a precharge of the compensation circuitry
connected to the PFCCOMP pin. This condition is met when the current out of the
PFCCOMP pin < |I
en(PFCCOMP)
|.
When at t6 the SNSBOOST voltage reaches the start level of the LLC (V
start(SNSBOOST)
),
the LLC converter starts to switch.
Fig 4. Start-up of the PFC and LLC
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