ICE3DS01L Datasheet, PDF (8/27 Pages) Infineon Technologies AG – Off-Line SMPS Current Mode Controller with integrated 500V Startup Cell

F3
ICE3DS01L/LG
Functional Description
3 Functional Description
All values which are used in the functional description
are typical values. For calculating the worst cases the
min/max values which can be found in section 4
Electrical Characteristics have to be considered.
SMPS. There is no need for an extra over sizing of the
SMPS, e.g. the transformer or PowerMOS.
3.2
Power Management
3.1
Introduction
The F3 is the further development of the F2 to meet the
requirements for the lowest Standby Power at
minimum load and no load conditions. A new fully
integrated Standby Power concept is implemented into
the IC in order to keep the application design easy.
Compared to F2 no further external parts are needed to
achieve the lowest Standby Power. An intelligent
Active Burst Mode is used for this Standby Mode. After
entering this mode there is still a full control of the
power conversion by the secondary side via the same
optocoupler that is used for the normal PWM control.
The response on load jumps is optimized. The voltage
ripple on V_out is minimized. V_out is further on well
controlled in this mode.
The usually external connected RC-filter in the
feedback line after the optocoupler is integrated in the
IC to reduce the external part count.
Furthermore a high voltage startup cell is integrated
into the IC which is switched off once the Undervoltage
Lockout on-threshold of 15V is exceeded. The external
startup resistor is no longer necessary. Power losses
are therefore reduced. This increases the efficiency
under light load conditions dramatically.
The Soft-Start capacitor is also used for providing an
adjustable blanking window for high load jumps. During
this time window the overload detection is disabled.
With this concept no further external components are
necessary to adjust the blanking window.
A new Latched Off Mode is implemented into the IC in
order to increase the robustness and safety of the
system. Latched Off Mode is only entered if very
dangerous conditions occur that damage the SMPS if
not switched off immediately. A restart of the system
can then only be done by disconnecting the AC line.
Auto Restart Mode reduces the average power
conversion to a minimum. In this mode malfunctions
are covered that could lead to a destruction of the
SMPS if no dramatically reduced power limitation is
provided over time. Once the malfunction is removed
normal operation is immediately started after the next
Start Up Phase.
The internal precise peak current limitation reduces the
costs for the transformer and the secondary diode. The
influence of the change in the input voltage on the
power limitation can be avoided together with the
integrated Propagation Delay Compensation.
Therefore the maximum power is nearly independent
on the input voltage that is required for wide range
HV
Startup Cell
VCC
Power Management
Internal Bias
Latched Off Mode
Reset
V_VCC < 6V
Power-Down Reset
Undervoltage Lockout
15V
8.5V
Voltage
6.5V
Reference
Auto Restart Mode
T1
Active Burst Mode
Latched Off Mode
SoftS
Figure 4 Power Management
The Undervoltage Lockout monitors the external
supply voltage V_VCC. When the SMPS is plugged to the
main line the internal Startup Cell is biased and starts
to charge the external capacitor C_VCC which is
connected to the VCC pin. The VCC charge current
that is provided by the Startup Cell from the HV pin is
1.05mA. When V_VCC exceeds the on-threshold
V_CCon=15V the internal voltage reference and bias
circuit are switched on. Then the Startup Cell is
switched off by the Undervoltage Lockout and therefore
also the power losses are switched off caused by the
Startup Cell which is connected to the bus voltage
(HV). To avoid uncontrolled ringing at switch-on a
hysteresis is implemented. The switch-off of the
Version 2.0
8
15 May 2003