ICE3RBR0665JZ Datasheet, PDF (14/31 Pages) Infineon Technologies AG – Off-Line SMPS Current Mode Controller with integrated 650V

ICE3RBR0665JZ
Functional Description
3.6.1
Leading Edge Blanking
V_Sense
V_csth
t_LEB = 220ns
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 integrated 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 over-current detection, there is always
propagation delay to switch off the integrated
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).
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.
I_Sense
I_peak2
I_peak1
I_Limit
Signal2
I_Overshoot2
Signal1
t_{Propagation Delay}
I_Overshoot1
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 depends 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
Version 2.0
14
7 Jun 2013