ICE2QR4765_12 Datasheet, PDF (11/22 Pages) Infineon Technologies AG – Off-Line SMPS Quasi-Resonant PWM Controller with integrated 650V Startup Cell/Depletion CoolMOS In DIP-8

CoolSET^® - Q1
ICE2QR4765
Functional Description
immediately after leaving Active Burst Mode. This is
helpful to decrease the output voltage undershoot.
V_FB
V_FBLB
V_FBBOn
V_FBBOff
Entering
Active Burst
Mode
Leaving
Active Burst
Mode
V_FBEB
Blanking Window (t_BEB)
t
V_CS
1.0V
V_CSB
Current limit level
during Active Burst
Mode
V_VCC
t
V_VCCoff
V_O
t
Max. Ripple < 1%
IC is reset and the main power switch is then kept off.
After the VCC voltage falls below the threshold V_VCCoff,
the startup cell is activated. The VCC capacitor is then
charged up. Once the voltage exceeds the threshold
V_VCCon, the IC begins to operate with a new soft-start.
In case of open control loop or output over load, the
feedback voltage will be pulled up . After a blanking
time of 24ms, the IC enters auto-restart mode. The
blanking time here enables the converter to provide a
high power in case the increase in V_FB is due to a
sudden load increase. During off-time of the power
switch, the voltage at the zero-crossing pin is
monitored for output over-voltage detection. If the
voltage is higher than the preset threshold v_ZCOVP, the
IC is latched off after the preset blanking time.
If the junction temperature of IC exceeds 140 °C, the IC
enter into autorestart mode.
If the voltage at the current sensing pin is higher than
the preset threshold v_CSSW during on-time of the power
switch, the IC is latched off. This is short-winding
protection.
During latch-off protection mode, when the VCC
voltage drops to 10.5V,the startup cell is activated and
the VCC voltage is charged to 18V then the startup cell
is shut down again and repeats the previous procedure.
There is also an maximum on time limitation inside
ICE2QR4765. Once the gate voltage is high longer
than t_OnMAx, it is turned off immediately.
t
Figure 8 Signals in Active Burst Mode
3.6
Protection Functions
The IC provides full protection functions. The following
table summarizes these protection functions.
Table 2 Protection features
VCC Overvoltage
VCC Undervoltage
Overload/Open Loop
Over temperature
Output Overvoltage
Short Winding
Auto Restart Mode
Auto Restart Mode
Auto Restart Mode
Auto Restart Mode
Latched Off Mode
Latched Off Mode
During operation, the VCC voltage is continuously
monitored. In case of an under- or an over-voltage, the
Version 2.3
11
November 14, 2012