TEA1753T All information provided in this document is subject to legal disclaimers. © NXP B.V. 2012. All rights reserved.
Product data sheet Rev. 3. — 24 August 2012 26 of 32
NXP Semiconductors
TEA1753T
HV start-up flyback controller with integrated PFC controller
11. Application information
A power supply with the TEA1753T consists of a power factor correction circuit and a
flyback converter. See Figure 17
.
Capacitor C
VCC
buffers the IC supply voltage. The IC is powered 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 at the PFCSENSE and FBSENSE pins. The values of
R
SENSE1
and R
SENSE2
define the maximum primary peak current in MOSFETs S1 and S2.
In the example given, the LATCH pin is connected to a Negative Temperature Coefficient
(NTC) resistor. The protection is activated when the resistance drops below a value
calculated as follows:
(8)
A capacitor C
TIMEOUT
is connected to the FBCTRL pin. With a 120 nF capacitor, the
time-out protection is activated after 10 ms. R
LOOP
is added so that the time-out capacitor
does not interfere with the normal regulation loop.
R
S1
and R
S2
are added to prevent the soft-start capacitors from being charged during
normal operation due to negative voltage spikes across the sense resistors.
Resistor R
AUX1
is added to protect the IC from damage during lightning events.
RS3 and RCOMP are added to compensate for input voltage variations. The (stray)
capacitance on the drain node of MOSFET S3 affects the frequency reduction slope and
therefore the PFC switch-on and switch-off levels. Choosing the proper values for RS3
and RCOMP results in an input voltage independent PFC switch-on and switch-off power
level.
V
prot LATCH
I
OLATCH
-------------------------------
15.6 k=