TOP232G-TL Ver la hoja de datos (PDF) - Power Integrations, Inc
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TOP232G-TL Datasheet PDF : 36 Pages
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TOP232-234
35 W Multiple Output Power Supply
Figure 25 shows a five output, 35 W, secondary regulated
power supply utilizing a TOP233 for multiple output applications
such as set-top box, VCR, DVD, etc. The circuit shown is
designed for a 230 VAC input but can be used over the universal
range at a derated output power of 25 W. Alternatively, a
doubler input stage can be used at 100 or 115 VAC for the full
power rating of 35 W. TOPSwitch-FX provides several
advantages in the above mentioned applications.
A single line sense resistor R1 (2 MΩ) implements an under-
voltage detect (at 100 V), over-voltage shutdown (at 450 V) and
line feed forward with DCMAX reduction features. Under-
voltage detect ensures that the outputs are glitch free on power
down. The over-voltage shutdown turns off the TOPSwitch-FX
MOSFET above 450 V on the DC input rail, eliminating
reflected voltage and leakage inductance spikes, and hence,
extending the surge withstand to the 700 VDC rating of the
MOSFET. This feature prevents field failures in countries
where prolonged line voltage surges are common.
This design also takes advantage of soft-start and higher operating
frequency to reduce transformer size. A snubber circuit (R4,
C4) is used to slowdown dv/dt of the switching waveform
minimizing radiated video noise that could interfere with TV
reception. The half frequency option of the TOPSwitch-FX can
be used by connecting the FREQUENCY pin to the CONTROL
pin instead of the SOURCE pin in video noise sensitive
applications to allow for heavier snubbing without significant
impact on efficiency.
This design achieves ±5% load regulation on 3.3 V and 5 V
outputs using dual sensed optocoupler feedback through resistors
R9, R10 and R11. Other output voltages are set by the transformer
turns ratio. Output voltage on the low power -5 V output is shunt
regulated by resistor R12 and Zener diode VR2. Dummy load
resistor R13 is required to maintain regulation of the 30 V
output under light load conditions. Compensation of the TL431
(U3) is achieved with resistor R8 and capacitor C7. Primary
side compensation and auto-restart frequency are determined
by resistor R5 and capacitor C5. Second stage LC post-filtering
is used on the 3.3 V, 5 V and 18 V high power outputs (L2, L3,
L4 and C13, C15, C17) for low ripple. Full load operating
efficiency exceeds 75% across the AC input range. Primary
clamp components VR1 and D1 limit peak drain voltage to a
safe value.
The frequency jittering in TOPSwitch-FX helps reduce EMI,
maintaining emissions below CISPR 22 (FCC B) levels through
proper choice of Y1 capacitor (CY1) and input filtering elements
(CX1, L1). To minimize coupling of common mode transients
to the TOP233, Y1 capacitor is tied to the positive input DC rail.
Lightning strike immunity to 3 kV is attained with the addition
of a 275 V MOV (RV1).
BR1
400 V
L1
20 mH
CX1
0.1 µF
250 VAC
F1
3.15 A
J1
L
RV1
275 V
N
D8
MUR120
C10
100 µF
50 V
L2
3.3 µH
C11
1 µF
50 V
CY1
2.2 nF
D9
UF5402
C12
220 µF
25 V
L3
3.3 µH
C13
100 µF
25 V
VR1
P6KE200
D1
UF4007
C1
33 µF
400 V
C4
47 pF
R4
D
2 kΩ
TOP233Y
U1 S
R1
2 MΩ
1/2 W
T1
M TOPSwitch-FX
CONTROL
C
R5
F
6.8 Ω
C5
47 µF
D10
MBR1045
C14
1000 µF
25 V
D11
BYW29-
100
C16
1000 µF
25 V
C18
D12 330 µF
1N5819 10 V
R12
5Ω
L4
3.3 µH
C17
100 µF
10 V
C15
100 µF
10 V
VR2
1N5231
C19
100 µF
10 V
D2
1N4148
C6
100 nF
R6
51 Ω
U2
LTV817
R7
510 Ω
R10
15.0 kΩ
R9
9.53 kΩ
R8 C7
10 Ω 0.1 µF
C8
22 µF
U3
TL431CLP
R11
10.0 kΩ
Figure 25. 35 W Set-Top Box Power Supply.
30 V
@ 100 mA
18 V
@ 550 mA
R13
24 kΩ
5V
@ 2.5 A
3.3 V
@3A
RTN
-5 V
@ 100 mA
PI-2536-040401
15 B
7/01
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