Protection Functions - Denon DRA-F107 Service Manual

3.5

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
Output Overvoltage
Short Winding
During operation, the VCC voltage is continuously
monitored. In case of an under- or an over-voltage, the
IC is reset and the main power switch is then kept off.
After the VCC voltage falls below the threshold
V , the power cell is activated. The VCC capacitor
VCCUVP
is then charged up. Once the voltage exceeds the
threshold V , the IC begins to operate with a new
VCCon
soft-start.
In case of open control loop or output over load, the
regulation 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
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
IC is latched off after the preset blanking time.
If the voltage at the current sensing pin is higher than
the preset threshold v
csSW
switch, the IC is latched off. This is short-winding
protection.
During latch-off protection mode, the power cell is
activated and it keeps the VCC voltage at the level of
V
VCCBL.
Auto Restart Mode
Auto Restart Mode
Auto Restart Mode
Latched Off Mode
Latched Off Mode
is due to a
REG
, the
OPOVP
during on-time of the power
DRA-F107 / DRA-F107DAB
Functional Description
32