STMicroelectronics Double output SMPS for power line application using ALTAIR04-900 primary controller EVLALTAIR900-M1 EVLALTAIR900-M1 Data Sheet
Product codes
EVLALTAIR900-M1
ALTAIR04-900
Application information
Doc ID 18211 Rev 2
19/29
diagrams of
along with the others previously described, is noise-free since the
peak current is low
Figure 17.
Load-dependent operating modes: timing diagrams
5.8
Soft-start and starter block
The soft start feature is automatically implemented by the constant current block, as the
primary peak current is limited from the voltage on the C
primary peak current is limited from the voltage on the C
REF
capacitor.
During start-up, as the output voltage is zero, the IC starts in CC mode with no high peak
current operations. In this way the voltage on the output capacitor increases slowly and the
soft-start feature
current operations. In this way the voltage on the output capacitor increases slowly and the
soft-start feature
is ensured.
Actually the CREF value is not important to define the soft-start time, as its duration
depends on others circuit parameters, like transformer ratio, sense resistor, output
capacitors and load. The user can define the best appropriate value by experiments.
depends on others circuit parameters, like transformer ratio, sense resistor, output
capacitors and load. The user can define the best appropriate value by experiments.
COMP
I
DS
65 mV
hyster.
hyster.
Normal-mode
Burst-mode
Normal-mode
T
STA R T
T
S TA RT
T
S TA R T
T
ST AR T
V
COMPL