A High Efficiency, 65 W, Universal Input Power Supply - Power integrations TOPSwitch-HX Series Manual

TOP252-262

A High Efficiency, 65 W, Universal Input Power Supply

The circuit shown in Figure 44 delivers 65 W (19 V @ 3.42 A) at
88% efficiency using a TOP260EN operating over an input
voltage range of 90 VAC to 265 VAC.
Capacitors C1 and C6 and inductors L1 and L2 provide
common mode and differential mode EMI filtering. Capacitor C2
is the bulk filter capacitor that ensures low ripple DC input to the
flyback converter stage. Capacitor C4 provides decoupling for
switching currents reducing differential mode EMI.
In this example, the TOP260EN is used at reduced current limit
to improve efficiency.
Resistors R5, R6 and R7 provide power limiting, maintaining
relatively constant overload power with input voltage. Line
sensing is implemented by connecting a 4 MW impedance from
the V pin to the DC rail. Resistors R3 and R4 together form the
4 MW line sense resistor. If the DC input rail rises above
450 VDC, then TOPSwitch-HX will stop switching until the
voltage returns to normal, preventing device damage.
This circuit features a high efficiency clamp network consisting
of diode D1, zener VR1, capacitor C5 together with resistors R8
and R9. The snubber clamp is used to dissipate the energy of
the leakage reactance of the transformer. At light load levels,
very little power is dissipated by VR1 improving efficiency as
compared to a conventional RCD clamp network.
3KBP08M
BR1
L1
12 mH
C2
120 µF
R1 R2
400 V
2.2 MΩ 2.2 MΩ
C1
F1
330 nF
4 A
275 VAC
L
E
N
90 - 265
VAC
C3
470 pF
250 VAC
L2
Ferrite Bead
Figure 44. 65 W, 19 V Power Supply Using TOP260EN.
24
Rev. J 08/16
250 VAC
C5
VR1
2.2 nF
BZY97C180
1 kV
180 V
4
5
R8
R9
100 Ω
1 kΩ
6
R3 R5
2.0 MΩ 5.1 MΩ
D1
DL4937
R4 R6
2.0 MΩ 6.8 MΩ
D5
BAV19WS
C4
100 nF D3
BAV19WS
400 V
TOPSwitch-HX
U1
TOP260EN
D V
CONTROL
C
S
X F
C8
R7
100 nF
15 kΩ
50 V
1%
The secondary output from the transformer is rectified by diode
D2 and filtered by capacitors C13 and C14. Ferrite Bead L3 and
capacitors C15 form a second stage filter and effectively reduce
the switching noise to the output.
Output voltage is controlled using a LM431 reference IC.
Resistor R19 and R20 form a potential divider to sense the
output voltage. Resistor R16 limits the optocoupler LED current
and sets the overall control loop DC gain. Control loop
compensation is achieved using C18 and R21. The components
connected to the control pin on the primary side C8, C9 and
R15 set the low frequency pole and zero to further shape the
control loop response. Capacitor C17 provides a soft finish
during startup. Optocoupler U2 is used for isolation of the
feedback signal.
Diode D4 and capacitor C10 form the bias winding rectifier and
filter. Should the feedback loop break due to a defective
component, a rising bias winding voltage will cause the Zener
VR2 to break down and trigger the over voltage protection
which will inhibit switching.
An optional secondary side over voltage protection feature
which offers higher precision (as compared to sensing via the
bias winding) is implemented using VR3, R18 and U3. Excess
voltage at the output will cause current to flow through the
optocoupler U3 LED which in turn will inject current in the V-pin
through resistor R13, thereby triggering the over voltage
protection feature.
C6
C12
2.2 nF R16
1 nF
33 Ω
100 V
C13
470 µF 470 µF
T1
RM10 FL1 25 V
D2
MBR20100CT
FL2
C10 VR2
R10
22 µF
1N5248B
73.2 kΩ
50 V 18 V
3
C11
100 nF
50 V
2
R11
D4 BAV19WS
2 MΩ
680 Ω
R12
5.1 kΩ U3B
C7
PC357A
100 nF
25 V
U2A
LTY817C
U2B
R13
LTY817C
5.1 Ω
R14
D6
100 Ω
1N4148
R15
6.8 Ω
C16
1 µF
C9
50 V
47 µF
16 V C17
33 µF
35 V
L3
C14 C15
Ferrite
47 µF
19 V, 3.42 A
Bead
25 V 25 V
VR3
BZX79-C22
22 V
R16
R18
47 Ω
U3A
PC357A
R19
68.1 kΩ
C18
100 nF
R21
1 kΩ
U4
LM431
R20
2%
10 kΩ
PI-4998-021408
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