ICE3BR2565JF Datasheet, PDF (14/36 Pages) Infineon Technologies AG – Off-Line SMPS Current Mode Controller with integrated 650V CoolMOS and Startup cell (frequency jitter Mode) in FullPak

3.6.1
Leading Edge Blanking
V_Sense
V_csth
t_LEB = 220ns
CoolSET^®-F3R
ICE3BR2565JF
Functional Description
For example, I_peak = 0.5A with R_Sense = 2. The current
sense threshold is set to a static voltage level V_csth=1V
without Propagation Delay Compensation. A current
ramp of dI/dt = 0.4A/µs, or dV_Sense/dt = 0.8V/µs, and a
propagation delay time of t_{Propagation Delay} =180ns leads
to an I_peak overshoot of 14.4%. With the propagation
delay compensation, the overshoot is only around 2%
(see Figure 20).
t
Figure 18 Leading Edge Blanking
Whenever the internal CoolMOS^® is switched on, a
leading edge spike is generated due to the primary-
side capacitances and reverse recovery time of the
secondary-side rectifier. This spike can cause the gate
drive to switch off unintentionally. In order to avoid a
premature termination of the switching pulse, this spike
is blanked out with a time constant of t_LEB = 220ns.
3.6.2 Propagation Delay Compensation
In case of overcurrent detection, there is always
propagation delay to switch off the internal CoolMOS^®.
An overshoot of the peak current I_peak is induced to the
delay, which depends on the ratio of dI/dt of the peak
current (see Figure 19).
I_Sense
I_peak2
I_peak1
I_{L im it}
Signal2
I _{O v e rs h o o t2}
Signal1
t_{Propagation Delay}
I _{O v e rs h o o t1}
V
1,3
1,25
1,2
1,15
1,1
1,05
1
0,95
0,9
0
with compensation
without compensation
0,2 0,4 0,6 0,8
1 1,2 1,4 1,6 1,8
dV_Sense
dt
2_V
µs
Figure 20 Overcurrent Shutdown
The Propagation Delay Compensation is realized by
means of a dynamic threshold voltage V_csth (see Figure
21). In case of a steeper slope the switch off of the
driver is earlier to compensate the delay.
V_{OSC max. Duty Cycle}
V_Sense
V_csth
off time
Propagation Delay t
t
Figure 19 Current Limiting
The overshoot of Signal2 is larger than of Signal1 due
to the steeper rising waveform. This change in the
slope is depending on the AC input voltage.
Propagation Delay Compensation is integrated to
reduce the overshoot due to dI/dt of the rising primary
current. Thus the propagation delay time between
exceeding the current sense threshold V_csth and the
switching off of the integrated CoolMOS^® is
compensated over temperature within a wide range.
Current Limiting is then very accurate.
Figure 21
Signal1
Signal2
t
Dynamic Voltage Threshold V_csth
3.7
Control Unit
The Control Unit contains the functions for Active Burst
Mode and Auto Restart Mode. The Active Burst Mode
and the Auto Restart Mode both have 20ms internal
Blanking Time. For the Auto Restart Mode, a further
extendable Blanking Time is achieved by adding
Version 2.0
14
11 Sep 2008