Техническая Спецификация для STMicroelectronics 19V - 90W Adapter with PFC for Laptop computers using the L6563H and L6699 EVL6699-90WADP EVL6699-90WADP
Модели
EVL6699-90WADP
Application information
L6699
20/38
Doc ID 022835 Rev 2
the operating frequency is essentially determined by the current sunk by the optocoupler's
phototransistor.
phototransistor.
During this frequency sweep phase the operating frequency decays following the
exponential charge of C
exponential charge of C
SS
: then, it initially changes relatively quickly but the rate of change
gets slower and slower. This counteracts the non-linear frequency dependence of the tank
circuit that makes the converter's input impedance change little as frequency is away from
resonance and change very quickly as frequency approaches resonance frequency (see
circuit that makes the converter's input impedance change little as frequency is away from
resonance and change very quickly as frequency approaches resonance frequency (see
As a result, the DC input current smoothly increases, without the peaking that occurs with
linear frequency sweep, and the output voltage reaches the regulated value with almost no
overshoot.
linear frequency sweep, and the output voltage reaches the regulated value with almost no
overshoot.
Typically, R
SS
and C
SS
is selected based on the following relationships:
Equation 5
where f
start
is recommended to not be over 300 kHz. Please refer to the timing diagram of
to see some significant signals during the soft-start phase.
Figure 12.
Soft-start circuit
Figure 13.
Input impedance vs.
frequency curve in an LLC
resonant half bridge
frequency curve in an LLC
resonant half bridge
!-V
,
#S S
2&M IN
233
#33
2&M IN
!-V
,/7% 2
&2%15%. #9
F
\
)NITIAL
FREQUENCY
3TEADY
STATE
FREQUENCY
500%2
&2%15%. #9
SS
3
SS
min
start
min
SS
R
10
·
3
=
C
;
1
f
f
RF
=
R
-
-