ICE2AS01_06 Datasheet, PDF (12/24 Pages) Infineon Technologies AG – Off-Line SMPS Current Mode Controller

ICE2AS01/S01G
ICE2BS01/S01G
Functional Description
transistors as well as to protect them against
undesirable gate overvoltages.
PWM-Latch
1
VCC
Z1
Gate
failure modes are latched by an Error-Latch. Additional
thermal shutdown is latched by the Error-Latch. In case
of those failure modes the Error-Latch is set after a
blanking time of 5µs and the external Power Switch is
shut down. That blanking prevents the Error-Latch from
distortions caused by spikes during operation mode.
3.8.1
Overload & Open loop with normal
load
Overload & Open loop/normal load
5µs Blanking
FB
4.8V
Failure
Detection
Figure 17 Gate Driver
t
SoftS
At voltages below the undervoltage lockout threshold
5.3V
V_VCCoff the gate drive is active low.
Soft-Start Phase
The driver-stage is optimized to minimize EMI and to
provide high circuit efficiency. This is done by reducing
the switch on slope when reaching the external Power
Switch threshold. This is achieved by a slope control of
the rising edge at the driver’s output (see Figure 18).
Driver
T_Burst1
t
T_Restart
V_Gate ca. t = 130ns
C_Load = 1nF
t
VCC
5V
13.5V
8.5V
t
Figure 18 Gate Rising Slope
t
Thus the leading switch on spike is minimized. When
the external Power Switch is switched off, the falling
shape of the driver is slowed down when reaching 2V
to prevent an overshoot below ground. Furthermore the
driver circuit is designed to eliminate cross conduction
of the output stage.
Figure 19 Auto Restart Mode
Figure 19 shows the Auto Restart Mode in case of
overload or open loop with normal load. The detection
of open loop or overload is provided by the Comparator
C3, C4 and the AND-gate G2 (see Figure20).
3.8
Protection Unit (Auto Restart Mode)
An overload, open loop and overvoltage detection is
integrated within the Protection Unit. These three
Datasheet
12
Preliminary Data
30 Jun 2006