L6564HTR STMicroelectronics, L6564HTR Datasheet - Page 18

• Manufacturer Part Number: L6564HTR
• Description: Power Factor Correction ICs High Volt Start Up 700V PFC 100uA 6mA
• Manufacturer: STMicroelectronics

Specifications of L6564HTR

• Product Category: Power Factor Correction ICs
• Rohs: yes
• Maximum Power Dissipation: 0.75 W
• Maximum Operating Temperature: + 125 C
• Mounting Style: SMD/SMT
• Package / Case: SO-14
• Minimum Operating Temperature: - 25 C

Application information
6
6.1
6.2
18/35
Application information
Overvoltage protection
Normally, the voltage control loop keeps the output voltage V
close to its nominal value, set by the ratio of the resistors R1 and R2 of the output divider. A
pin of the device (PFC_OK) has been dedicated to monitor the output voltage with a
separate resistor divider (R3 high, R4 low, see
the voltage at the pin reaches 2.5 V if the output voltage exceeds a preset value, usually
larger than the maximum V
Example 1: V
= 51 kΩ .
When this function is triggered, the gate drive activity is immediately stopped until the
voltage on the PFC_OK pin drops below 2.4 V. Note that R1, R2, R3 and R4 can be selected
without any constraints. The unique criterion is that both dividers must sink a current from
the output bus which needs to be significantly higher than the bias current of both INV and
PFC_OK pins.
Figure 31. Output voltage setting, OVP and FFP functions: internal block diagram
Feedback failure protection (FFP)
The OVP function described above handles “normal” overvoltage conditions, i.e. those
resulting from an abrupt load/line change or occurring at startup. If the overvoltage is
generated by a feedback disconnection, for instance when the upper resistor of the output
divider (R1) fails to open, the comparator detects the voltage at the INV pin. If the voltage is
lower than 1.66 V and the OVP is active, the FFP is triggered, the gate drive activity is
R3
R3
o
= 400 V, V
R3a
R3a
R3b
R3b
R4
R4
R1a
R1a
R1b
R1b
R2
R2
OX
o
that can be expected.
= 434 V. Select: R3 = 8.8 MΩ; then: R4 = 8.8 MΩ ·2.5/(434-2.5)
Doc ID 022960 Rev 2
Vout
Vout
compensation
compensation
Frequency
Frequency
R1
R1
PFC_OK
PFC_OK
COMP
COMP
INV
INV
Figure 31
6
1
6
1
2
2
1.66 V
0.23 V
0.23 V
0.27 V
0.27 V
1.66 V
2.5 V
2.5 V
2.4 V
2.4 V
2.5 V
2.5 V
). This divider is selected so that
+
+
+
+
+
+
-
-
-
-
-
-
+
+
+
-
-
-
o
Disable
Disable
OVP
OVP
Error Amplifier
Error Amplifier
of the PFC pre-regulator
L_OVP
L_OVP
AM11459v1
L6564H