L6563 - L6563A
Application information
An important advantage of this technique is that the overvoltage level can be set
independently of the regulated output voltage: the latter depends on the ratio of R1 to R2,
the former on the individual value of R1. Another advantage is the precision: the tolerance of
the detection current is 15%, which means 15% tolerance on the ∆VO. Since it is usually
much smaller than Vo, the tolerance on the absolute value will be proportionally reduced.
Example: VO = 400V, ∆VO = 40V.
Then: R1 = 40V/20µA = 2MΩ ; R2 = 2.5·2MΩ·/(400-2.5) = 12.58kΩ.
The tolerance on the OVP level due to the L6563/A will be 40·0.15 = 6 V, that is ± 1.36%.
When either OVP is activated the quiescent consumption is reduced to minimize the
discharge of the Vcc capacitor.
Figure 33. Output voltage setting, OVP and FFP functions: internal block diagram
Vout
{R3a
R3
R3b
{R1a
R1
R1b
R4
0.26V
+
FAULT (not latched)
PFC_OK 7
INV 1
-
+
9.5V
-
2.5V
9.5V
ITBO
+
E/A
-
-
+
TBO
FUNCTION
FAULT (latched)
2.25V
20 µA
Frequency
Compensation
R2
2
COMP
Static OVP
Dynamic OVP
L6563
L6563A
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