PFS757HG POWERINT [Power Integrations, Inc.], PFS757HG Datasheet - Page 10

• Manufacturer Part Number: PFS757HG
• Description: Combined Two-Switch Forward and Flyback Power Supply Controllers with Integrated High Voltage MOSFETs
• Manufacturer: POWERINT [Power Integrations, Inc.]

A resistor R
FEEDBACK pin. This resistor feeds current into the FEEDBACK
pin (who’s voltage is clamped to approximately 1 V during this
detection period). The current into the FEEDBACK pin is
determined by the value of the resistor, and thus the input
current (and indirectly the resistor value), select an internal
current limit according to the following table.
Rev. C 02/11
Figure 8.
Figure 9.
Table 3.
11.9-23.8 mA
(Threshold)
5.1-11.9 mA
10
0.0-5.1 mA
I
FB
V
T
device start-up and before power supply switching
V
V
Current Limit Selection.
Duty Cycle Limit vs. Ratio of R Pin Current Over L Pin Current.
TFS757-764HG
FEEDBACK Pin Main Current Limit Selection.
SELECT
(EN)
(BP)
(FB)
I
(L)
FB
is connected from the BYPASS pin to the
- current limit selection occurs here during
UV(ON)
L1
L2
L3
4.7 V
1 V
STANDBY
100%
60%
80%
I
LIMIT
0.7
0.6
0.5
0.4
, I
(L)
0.5
= 25 µA
5.7 V
mA
mA
mA
PI-5975-102610
6.0 V after
regulation
2.7 V
2.2 V
acheives
standby
1.0
511.0
232.0
Open
R
EN(SELECT)
(1%)
kW
kW
kW
1.5
I
Main Line Undervoltage Detection (UV)
The LINE-SENSE pin resistor is connected to V
a current signal proportional to V
is held by the device at 2.35 V. The LINE-SENSE pin current
signal is used to trigger under/overvoltage thresholds for both the
standby and main converters. Assuming a LINE-SENSE pin
resistor of 4 MW, the standby will begin operating when the
LINE-SENSE pin current exceeds the (I
nominally approximately 100 V. However the main is still held in
the off-state, until the LINE-SENSE pin current exceeds the
(I
hysteresis for both main and standby undervoltage-off
thresholds, to allow sufficient margin to avoid accidental
triggering, and to provide sufficient margin to meet hold-up time
requirements. Bear in mind that the main converter may start to
loose regulation before it finally shuts down. This is because
the dynamic duty cycle limit may clamp the duty cycle below
that required for regulation at lower input voltages. Once the
input voltage falls below the 215 V (I
main will shutdown but standby will continue to operate. The
standby will turn off when the input voltage drops below
approximately 40 V (I
R
L(MA-UVON)
/I
L
2.0
I
) threshold, nominally 315 V for 4 MW. There is
L
I
I
I
L
L
L
= 100 µA
= 60 µA
= 90 µA
= 115 µA
2.5
L(SB-UVON)
).
IN
3.0
. The LINE-SENSE pin voltage
L(MA_UVOFF)
L(SB-UVON)
) threshold, the
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) threshold,
IN
and generates