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