TOP242R POWERINT [Power Integrations, Inc.], TOP242R Datasheet - Page 24

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TOP242R

Manufacturer Part Number
TOP242R
Description
TOPSwitch -GX Family Extended Power, Design Flexible, EcoSmart, Integrated Off-line Switcher
Manufacturer
POWERINT [Power Integrations, Inc.]
Datasheet

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Multiple Output, 60 W, 185-265 VAC Input Power Supply
Figure 44 shows a multiple output supply typical for high end
set-top boxes or cable decoders containing high capacity hard
disks for recording. The supply delivers an output power of
45 W cont./60 W peak (thermally limited) from an input
voltage of 185 to 265 VAC. Efficiency at 45 W, 185 VAC is
≥ 75%.
The 3.3 V and 5 V outputs are regulated to ±5% without the
need for secondary linear regulators. DC stacking (the
secondary winding reference for the other output voltages is
connected to the cathode of D10 rather than the anode) is used
to minimize the voltage error for the higher voltage outputs.
Due to the high ambient operating temperature requirement
typical of a set-top box (60 °C) the TOP246Y is used to
reduce conduction losses and minimize heat sink size. Resis-
tor R2 sets the device current limit to 80% of typical to limit
overload power. The line sense resistor (R1) protects the
TOPSwitch-GX from line surges and transients by sensing when
the DC rail voltage rises to above 450 V. In this condition the
TOPSwitch-GX stops switching, extending the input voltage
withstand to 496 VAC which is ideal for countries with poor
power quality. A thermistor (RT1) is used to prevent
premature failure of the fuse by limiting the inrush current (due
Figure 44. 60 W Multiple Output Power Supply using TOP246.
24
TOP242-250
0.1 F
PERFORMANCE SUMMARY
Output Power:
Regulation:
3.3 V:
5 V:
12 V:
18 V:
30 V:
Efficiency:
No Load Consumption:
J1
C1
X1
L
N
20 mH
0.8A
G
1/02
L1
3.15 A
14 mm
275 V
RV1
1N4007 V
F1
D1-D4
1.7 A
10
RT1
TOP246Y
68 F
400 V
C2
P6KE170
U1
45 W Cont./60 W Peak
0.6 W
VR1
75%
5%
5%
7%
7%
8%
D
S
D6
1N4937
68 k
CONTROL
CONTROL
2 W
R5
X
L
2 M
1/2 W
TOPSwitch-GX
F
R1
2.2 nF
400 V
1 nF
C
C6
Y1
C5
9.08 k
0.1 F
50 V
C3
.R2
T1
47 F
6.8
10 V
R3
C5
1N4148
10
R6
D6
D10
BYV32-200
D8
UF5402
D9
UF5402
D11
MBR1045
D7
UF4003
47 F
50 V
C7
1 F
50 V
330 F
C3
to the relatively large size of C2). An optional MOV (RV1)
extends the differential surge protection to 6 kV from 4 kV.
Leakage inductance clamping is provided by VR1, R5 and C5,
keeping the DRAIN voltage below 700 V under all conditions.
Resistor R5 and capacitor C5 are selected such that VR1
dissipates very little power except during overload conditions.
The frequency jittering feature of TOPSwitch-GX allows the
circuit shown to meet CISPR22B with simple EMI filtering
(C1, L1 and C6) and the output grounded.
The secondaries are rectified and smoothed by D7 to D11, C7,
C9, C11, C13, C14, C16 and C17. Diode D11 for the 3.3 V
output is a Schottky diode to maximize efficiency. Diode D10
for the 5 V output is a PN type to center the 5 V output at 5 V.
The 3.3 V and 5 V output require two capacitors in parallel to
meet the ripple current requirement. Switching noise filtering
is provided by L2 to L5 and C8, C10, C12, C15 and C18.
Resistor R6 prevents peak charging of the lightly loaded 30 V
output. The outputs are regulated using a secondary reference
(U3). Both the 3.3 V and 5 V outputs are sensed via R11 and
R10. Resistor R8 provides bias for U3 and R7 sets the overall
DC gain. Resistor R9, C19, R3 and C4 provide loop compen-
sation. A soft-finish capacitor (C20) eliminates output
overshoot.
25 V
C9
390 F
35 V
C11
1000 F
C13
25 V
22 F
10 V
C20
1000 F
1000 F
C14
25 V
C17
25 V
1000 F
C16
25 V
LTV817
150
R7
U2
3.3 H
3.3 H
3.3 H
3.3 H
U3
TL431
L2
L3
L4
L5
3A
3A
5A
5A
3.3 k
220 F
1 k
R9
C18
16 V
R8
220 F
165 V
C15
0.1 F
C19
9.53
10 k
R11
R12
k
100 F
C12
25 V
15.0
100 F
R10
k
C10
25 V
10 F
50 V
C8
PI-2693-033001
30 V @
18 V @
12 V @
5 V @
3.3 V @
0.03 A
0.5 A
0.6 A
3.2 A
3 A
RTN

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