L6560 查看數據表（PDF） - STMicroelectronics
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L6560 Datasheet PDF : 11 Pages
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L6560 - L6560A
ELECTRICAL CHARACTERISTICS (continued)
ZERO CURRENT DETECTOR
Symbol
VZCD
VZCD
VZCD
Pin
Parameter
Test Condition
5 Input Threshold Voltage Rising
Edge
Hysteresis
5 Clamp Voltage
IZCD = 3mA
5 Clamp Voltage
IZCD = –3mA
OUTPUT SECTION
Min. Typ. Max. Unit
1.8
2.3
V
0.3 0.5 0.7
V
5
5.7 6.4
V
0.4 0.7
1
V
Symbol Pin
Parameter
VGD
7 Dropout Voltage
tr
7 Output Voltage Rise Time
tf
7 Output Voltage Fall Time
Test Condition
IGDsource = 200mA
IGDsource = 20mA
IGDsink = 200mA
IGDsink = 20mA
CL = 1nF
CL = 1nF
Min. Typ. Max. Unit
1.2
2
V
0.7
1
V
1.5
V
0.3
V
50 120 ns
40 100 ns
OUTPUT OVERVOLTAGE SECTION
Symbol Pin
Parameter
IOVP
2 OVP Triggering Current
RESTART TIMER
Test Condition
Min. Typ. Max. Unit
36
40
44
µA
Symbol
tSTART
Pin
Parameter
Start Timer
Test Condition
Min. Typ. Max. Unit
45 60
µs
OVER VOLTAGE PROTECTION OVP
The output voltage is expected to be kept by the
operation of the PFC circuits close to its reference
value that is set by the ratio of the two external re-
sistors R1 and R2 (see fig. 2), taking into consid-
eration that the non inverting input of the error
amplifier is biased inside the L6560 at 2.5V.
In steady state conditions, the current through R1
and R2 is:
ISC
=
∆Voutsc −
R1
2.5
or
ISC =
2.5
R2
and, if the external compensation network is
made only with a capacitor C, the current through
C is equal zero.
When the output voltage increases abruptly the
current through R1 becomes:
IR1
=
Vout − 2.5
R1
IR1
=
Voutsc
+
∆VOUT
R1
−
2.5
=
Isc
+
∆I.
Since the current through R2 doesn’t change, the
∆I current must flow through the capacitor C and
enter in the error amplifier.
This current is mirrored inside the L6560, and
compared with a precise internal reference of
40µA. Whenever such 40µA limit is exceed, the
OVP protection is triggered (Dynamic OVP), and
the external power transistor is switched off, until
the overvoltage situation disappears. However if
the overvoltage persists, before that the transient
condition of dynamic circuit exhausts, an internal
comparator (Static OVP) latches the OVP condi-
tion keeping the external power switch turned off
(see fig. 1).
The OVP value is threfore set by the equation
OVP = ∆Vout = R1 ⋅ 40µA.
Typical values for R1, R2 and C are reported in
the application circuit. The overvoltage can be set
independently from the average output voltage.
The precision in setting the overvoltage threshold
is 7% of the overvoltage value (for instance ∆V =
60V ± 4.2V).
4/11
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