SSL8516T All information provided in this document is subject to legal disclaimers. © NXP Semiconductors N.V. 2014. All rights reserved.
Product data sheet Rev. 1 — 5 May 2014 27 of 33
NXP Semiconductors
SSL8516T
Greenchip PFC and flyback controller
11. Application information
An LED driver with the SSL8516T consists of a PFC circuit and a flyback converter (see
Figure 16
).
Capacitor C
VCC
buffers the IC supply voltage. The IC supply is charged from the high
voltage rectified mains during start-up and the auxiliary winding of the flyback converter
during operation. Sense resistors R
SENSE1
and R
SENSE2
convert the current through the
MOSFETs S1 and S2 into a voltage on the PFCSENSE and FBSENSE pins. The R
SENSE1
and R
SENSE2
values define the maximum primary peak current in MOSFETs S1 and S2.
In the example, the LATCH pin is connected to a Negative Temperature Coefficient (NTC)
resistor. The protection is activated when the resistance drops below the value as
calculated in Equation 8
:
(8)
Capacitor C
TIMEOUT
is connected to the FBCTRL pin. R
LOOP
ensures that the time-out
capacitor does not interfere with the flyback regulation control loop.
R
S1
and R
S2
prevent that the soft-start capacitors C
SS1
and C
SS2
are charged during
normal operation due to negative voltage spikes across the sense resistors.
Resistor R
AUX1
protects the IC from damage during lightning events.
R
S3
and R
COMP
can be used to lower the PFC on/off power level. The minimum and
maximum peak current ratio increase. So, the PFC switch-on and switch-off power level
decreases.
R
DRV1
and R
DRV2
prevent that the internal MOSET drivers are damaged due to, for
example, power MOSFET avalanche.
Depending on the drain voltage maximum rating of MOSFET S2, the HV pin of the IC can
either be connected to the center tap of the flyback transformer or to the drain of MOSFET
S2.
V
prot LATCH
I
OLATCH
-------------------------------
16.2 k=
