lnk623 Power Integrations, Inc., lnk623 Datasheet - Page 4

• Manufacturer Part Number: lnk623
• Description: Energy-efficient, Off-line Switcher With Accurate Primary-side Constant-voltage Cv Control
• Manufacturer: Power Integrations, Inc.

Rev. C 12/08
Applications Example
Figure 4.
Circuit Description
This circuit is confi gured as a three output, primary-side
regulated fl yback power supply utilizing the LNK626PG. It can
deliver 7 W continuously and 10 W peak (thermally limited) from
an universal input voltage range (85 – 265 VAC). Effi ciency is
>67% at 115 VAC/230 VAC and no-load input power is
<140 mW at 230 VAC.
Input Filter
AC input power is rectifi ed by diodes D1 through D4. The
rectifi ed DC is fi ltered by the bulk storage capacitors C1 and
C2. Inductor L1, L2, C1 and C2 form a pi (π) fi lter, which
attenuates conducted differential-mode EMI noise. This
confi guration along with Power Integrations transformer
E-shield
EN55022 class B with good margin without requiring a
Y capacitor. Fuse F1 provides protection against catastrophic
failure. Negative temperature coeffi cient thermistor RT1 limits
the inrush current when AC is fi rst applied to below the
maximum rating of diodes D1 through D4. Metal oxide varistor
RV1 clamps the AC input during differential line transients,
protecting the input components and maintaining the peak
drain voltage of U1 below its 700 V BV
surge levels at or below 2 kV this component may be omitted.
LNK626 Primary
The LNK626PG device (U1) incorporates the power switching
device, oscillator, CV control engine, startup, and protection
85 - 265
VAC
4
L
N
™
10
3.15 A
RT1
7 W (10 W peak) Multiple Output Flyback Converter for DVD Applications with Primary Sensed Feedback.
technology allow this design to meet EMI standard
F1
LNK623-626
1N4007
FR106
275 V
RV1
D1
D3
FR106
1N4007
D2
D4
3.5 × 7.6 mm
Ferrite Bead
22 F
400 V
680 uH
C1
L1
L2
DSS
rating. For differential
22 F
400 V
1N5272B
C2
VR1
5.1 k
1/8 W
R1
LinkSwitch-CV
390
1N4007
R2
LNK626PG
50 V
1 F
D5
C4
U1
820 pF
1 kV
C3
6.2 k
R4
functions. The integrated 700 V MOSFET provides a large drain
voltage margin in universal input AC applications, increasing
reliability and also reducing the output diode voltage stress by
allowing a greater transformer turns ratio. The device can be
completely self-powered from the BYPASS pin and decoupling
capacitor C4. In this design a bias circuit (D6, C6 and R4) was
added to reduce no load input power below 140 mW.
The rectifi ed and fi ltered input voltage is applied to one side of
the primary winding of T1. The other side of the transformer’s
primary winding is driven by the integrated MOSFET in U1. The
leakage inductance drain voltage spike is limited by the clamp
circuit D5, R1, R2, C3 and VR1. The zener bleed clamp
arrangement was selected for lowest no-load input power but in
applications where higher no-load input power is acceptable
VR1 may be omitted and the value of R1 increased to form a
standard RCD clamp.
Output Rectifi cation
The secondaries of the transformer are rectifi ed by D7, D8 and
D9. A Schottky barrier type was used for the main 5 V output
for higher effi ciency. The +12 V and -22 V outputs use an
ultrafast rectifi er diode. The main output is post fi ltered by L3
and C10 to remove switching frequency ripple. Resistors R7,
R8 and R9 provide a preload to maintain the output voltages
within their respective limits when unloaded. To reduce high
frequency ringing and associated radiated EMI an RC snubber
formed by R10 and C13 was added across D7.
1
3
47 k
1/8 W
680 pF
EEL19
R5
50 V
C5
T1
8,9,10
11
12
6
7
5
4
2
4.02 k
D7 SB540
1%
R6
1N4148
D6
47
R10
UF4003
UF4003
D8
6.34 k
D9
10 F
50 V
1%
R3
C6
270 pF
C13
PI-5205-102208
1000 F
47 F
25 V
C9
10 V
C8
47 F
50 V
C11
10 H
470 F
L3
10 V
C10
39 k
1/8 W
R9
www.powerint.com
24 k
1/8 W
R8
510
1/8 W
-22 V, 15 mA
R7
12 V, 0.1 A
5 V, 1.7 A
RTN