Table of Contents
Advertisement
6.6
Protection Features
The IC provides several protection features which lead to the Auto Restart Protection Mode. The following
table shows the conditions of the system failure and the associate protection mode.
Protection function
Vcc Over-voltage
Over-temperature
(controller junction)
Over-load / Open loop
Vcc Under-voltage / short
Opto-coupler
Auto-restart enable
Table 1
Protection functions and failure conditions
The 25.5V OVP protection is inactivated during burst mode so that it can achieve lower standby power
performance.
6.6.1
Auto Restart Protection Mode
When the failure condition meets the auto restart protection mode, the IC will go into auto-restart. The
switching pulse will stop. Then the Vcc voltage will drop. When the Vcc voltage drops to 10.5V, the startup
cell will turn on again. The Vcc voltage is then charged up. When it hits 18V, the IC will turn on and the
startup cell will turn off. It would then start the startup phase with soft start. After the startup phase the failure
condition is checked to determine whether the fault persists. If the fault is removed, it will go to normal
operation. Otherwise, the IC will repeat the auto restart protection and the switching pulse stop again.
Figure 15 shows the switching waveform of the V
overloaded by shorting the outputs. The IC is turned on at V
IC is off again due to the presence of the fault. V
activated again to charge up capacitor at V
V
DS
Vcc
V
FB
V
BA
Application Note
Failure condition
1. Vcc > 25.5V or
2. Vcc > 20.5V & FB > 4.0V & during soft start period
T
> 130°C
J
V
> 4.0V and V
> 4.0V
FB
BA
(Blanking time counted from charging V
4.0V )
Vcc < 10.5V
V
< 0.33V
BA
CC
CC
that initiates another restart cycle.
CC
Figure 15
Auto Restart Mode
15
from 0.9V to
BA
and the feedback voltage V
= 18V. After going through the startup phase,
CC
is discharged until 10.5V. Then, the Startup Cell is
Channel 1; C1 : Drain-Source Voltage (V
Channel 2; C2 : Supply Voltage (V
Channel 3; C3 : Feedback Voltage ( V
Channel 4; C4 : BA voltage ( V
System enters auto restart mode when output
voltage short circuit @ Vin=85Vac
ICE3BRXX65J(Z)(G)
Protection Mode
Auto Restart
Auto Restart
Auto Restart
Auto Restart
Auto Restart
when the output is
FB
)
DS
)
CC
)
FB
)
BA
2010-06-20
Advertisement
Table of Contents
