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Overcurrent Protection
PCL
+
V
PCL
1.08V
ISENSE
Soft Over Current (SOC)
R
SENSE
R
ISENSE
+–
C
ISENSE
(Optional)
LINE
INPUT
V
OUT
V
SOC
0.73V
Peak Current Limit (PCL)
SOC
+
-1x
300ns
Leading Edge
Blanking
+
Soft Over-Current (SOC)
Peak Current Limit (PCL)
UCC28019
SLUS755B – APRIL 2007 – REVISED DECEMBER 2007
Inductor current is sensed by R
SENSE
, a low value resistor in the return path of input rectifier. The other side of
the resistor is tied to the system ground. The voltage is sensed on the rectifier side of the sense resistor and is
always negative. There are two over-current protection features; Peak Current Limit (PCL) protects against
inductor saturation and Soft Over Current (SOC) protects against an overload on the output.
Figure 25. Soft Over Current (SOC) / Peak Current Limit (PCL)
SOC limits the input current. SOC is activated when the current sense voltage on ISENSE reaches -0.73 V,
affecting the internal VCOMP level, and the control loop is adjusted to reduce the PWM duty cycle.
Peak current limit operates on a cycle-by-cycle basis. When the current sense voltage on ISENSE reaches -1.08
V, PCL is activated terminating the active switch cycle. The voltage at ISENSE is amplified by a fixed gain of -1.0
and then leading-edge blanked to improve noise immunity against false triggering.
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Product Folder Link(s): UCC28019