TOP242R POWERINT [Power Integrations, Inc.], TOP242R Datasheet - Page 22

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

A High Efficiency, Enclosed, 70 W, Universal Adapter Supply
The circuit shown in figure 42 takes advantage of several of the
TOPSwitch-GX features to reduce cost, power supply size and
increase efficiency. This design delivers 70 W at 19 V, from an
85 to 265 VAC input, at an ambient of 40 °C, in a small sealed
adapter case (4” x 2.15” x 1”). Full load efficiency is 85% at
85 VAC rising to 90% at 230 VAC input.
Due to the thermal environment of a sealed adapter a TOP249Y
is used to minimize device dissipation. Resistors R9 and R10
externally program the current limit level to just above the
operating peak DRAIN current at full load and low line. This
allows the use of a smaller transformer core size without
saturation during startup or output load transients. Resistors
R9 and R10 also reduce the current limit with increasing line
voltage, limiting the maximum overload power at high input
line voltage, removing the need for any protection circuitry on
the secondary. Resistor R11 implements an under voltage and
over voltage sense as well as providing line feed forward for
reduced output line frequency ripple. With resistor R11 set at
2 MΩ the power supply does not start operating until the DC
rail voltage reaches 100 VDC. On removal of the AC input the
UV sense prevents the output glitching as C1 discharges,
turning off the TOPSwitch-GX when the output regulation is
lost or when the input voltage falls to below 40 V, whichever
occurs first. This same value of R11 sets the OV threshold to
450 V. If exceeded, for example during a line surge,
TOPSwitch-GX stops switching for the duration of the surge
extending the high voltage withstand to 700 V without device
Figure 42. 70 W Power Supply using Current Limit Reduction with Line and Line Sensing for UV and OV.
22
TOP242-250
0.1 F
J1
L
N
C6
X2
820 H
G
1/02
2A
L2
F1
3.15 A
1.7 A
8A 600 V
10
RT1
RS805
BR1
t
0.33 F
400 V
C13
L3
75 H
2A
150 F
400 V
C1
0.022 F
400 V
C12
0.01 F
400 V
C11
13 M
20.5 k
R9
R10
D
S
1/2 W
VR1
P6KE-
200
D1
UF4006
2 M
CONTROL
R11
CONTROL
X
C7 2.2 nF
Y1 Safety
L
TOPSwitch-GX
T1
F
0.1 F
50 V
C8
C
TOP249Y
damage. Capacitor C11 has been added in parallel with VR1 to
reduce Zener clamp dissipation. With a switching frequency of
132 kHz a PQ26/20 core can be used to provide 70 W. To
maximize efficiency, by reducing winding losses, two output
windings are used each with their own dual 100 V Schottky
rectifier (D2 and D3). The frequency reduction feature of the
TOPSwitch-GX eliminates any dummy loading to maintain
regulation at no-load and reduces the no-load consumption of the
power supply to only 520 mW at 230 VAC input. Frequency
jittering provides conducted EMI meeting the CISPR 22
(FCC B) / EN55022B specification, using simple filter compo-
nents (C7, L2, L3 and C6) even with the output earth grounded.
To regulate the output an optocoupler (U2) is used with a
secondary reference sensing the output voltage via a resistor
divider (U3, R4, R5, R6). Diode D4 and C15 filter and smooth
the output of the bias winding. Capacitor C15 (1µF) prevents the
bias voltage from falling during zero to full load transients.
Resistor R8 provides filtering of leakage inductance spikes
keeping the bias voltage constant even at high output loads.
Resistor R7, C9 and C10 together with C5 and R3 provide loop
compensation.
Due to the large primary currents, all the small signal control
components are connected to a separate source node that is Kelvin
connected to the source pin of the TOPSwitch-GX. For improved
common mode surge immunity the bias winding common
returns directly to the DC bulk capacitor (C1).
U1
D4
1N4148
D3
MBR20100
D2
MBR20100
47 F
6.8
16 V
4.7
C5
R3
R8
1 F
50 V
C15
820 F
25 V
C2
PERFORMANCE SUMMARY
Output Power:
Regulation:
Efficiency:
Ripple:
No Load Consumption:
820 F
PC817A
25 V
TL431
All resistors 1/8 W 5% unless otherwise stated.
C3
U2
U3
270
R1
200 H
56 k
L1
R7
1 k
C9
4.7 nF 50 V
R2
820 F
25 V
C4
70 W
31.6 k
4.75 k
4%
84%
120 mV pk-pk
0.52 W @ 230 VAC
0.1 F
0.1 F
562
1%
R4
50 V
C10
50 V
1%
C14
R6
1%
R5
PI-2691-033001
19 V
@ 3.6 A
RTN