UCC28600
www.ti.com
SLUS646J –NOVEMBER 2005–REVISED JULY 2011
DCM
SS Mode
QR Mode
(Valley Switching, VS)
Green Mode
FFM, (VS)
(maximum fs)
(Fixed f
)
SW
fsw
(VS)
f
=
MAX
Oscillator Frequency
(130 kHz)
This mode applies bursts of
40kHz soft−start pulses to the
power MOSFET gate. The
average fsw is shown in this
operating mode.
f
GRMODE_MX
(40 kHz)
f
SS
(40 kHz)
f
QR_MIN
Internally Limit-
ed to 40 kHz
t
t
V
FB
Hysteretic
Transition into
Green Mode
Burst Hysteresis
V
OUT
t
V
STATUS
Green Mode,
PFC bias OFF
t
t
Load shown is slightly
less than overcurrent
threshold
Regular Operation
IC Off
Fixed Frequency
Softstart
Green Mode
Frequency
Foldback
P
OUT
P
OUT, (max)
t
Figure 4. Operation Mode Switching Frequencies
Copyright © 2005–2011, Texas Instruments Incorporated
13
TI [ TEXAS INSTRUMENTS ]
