A High Efficiency, 20 W Continuous - 80 W Peak, Universal Input Power Supply - Power integrations TOPSwitch-HX Series Manual

A High Efficiency, 20 W continuous – 80 W Peak, Universal
Input Power Supply
The circuit shown in Figure 43 takes advantage of several of
TOPSwitch-HX features to reduce system cost and power
supply size and to improve power supply efficiency while
delivering significant peak power for a short duration. This
design delivers continuous 20 W and peak 80 W at 32 V from
an 90 VAC to 264 VAC input. A nominal efficiency of 82% at full
load is achieved using TOP258MN. The M-package part has an
optimized current limit to enable design of power supplies
capable of delivering high power for a short duration.
Resistor R12 sets the current limit of the part. Resistors R11
and R14 provide line feed forward information that reduces the
current limit with increasing DC bus voltage, thereby maintaining
a constant overload power level with increasing line voltage.
Resistors R1 and R2 implement the line undervoltage and
overvoltage function and also provide feed forward compensation
for reducing line frequency ripple at the output. The overvoltage
feature inhibits TOPSwitch-HX switching during a line surge
extending the high voltage withstand to 700 V without device
damage.
The snubber circuit comprising of VR7, R17, R25, C5 and D2
limits the maximum drain voltage and dissipates energy stored in
the leakage inductance of transformer T1. This clamp configuration
maximizes energy efficiency by preventing C5 from discharging
below the value of VR7 during the lower frequency operating
modes of TOPSwitch-HX. Resistor R25 damps high frequency
ringing for reduced EMI.
A combined output overvoltage and over power protection
circuit is provided via the latching shutdown feature of
D8 D9
1N4007
1N4007
o
t
D11 D10 RT1
1N4007 1N4007
10 Ω
L1
5.3 mH
D13
1N4007
R23 R24
1 MΩ 1 MΩ
R3
2 MΩ
C1
F1
220 nF
3.15 A
275 VAC
R4
2 MΩ
90 - 264
VAC
C30
100 nF
400 V
68
Figure 43. 20 W Continuous, 80 W Peak, Universal Input Power Supply using TOP258MN.
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VR7
BZY97C150
C3
150 V
120 µF
400 V
R11
R1
R17
3.6 MΩ
2 MΩ
1 kΩ
0.5 W
R2 R14
2 MΩ
3.6 MΩ
D
R21
CONTROL
1 MΩ
0.125 W
S
R15
1 kΩ
TOPSwitch-HX
R12
Q1
U4
7.5 kΩ
2N3904
TOP258MN
1%
Q2
Q3
2N3904
2N3904
R26
R18
kΩ
39 kΩ
TOPSwitch-HX and R20, C9, R22 and VR5. Should the bias
winding output voltage across C13 rise due to output overload
or an open loop fault (opto coupler failure), then VR5 conducts
triggering the latching shutdown. To prevent false triggering
due to short duration overload, a delay is provided by R20, R22
and C9.
To reset the supply following a latching shutdown, the V pin
must fall below the reset threshold. To prevent the long reset
delay associated with the input capacitor discharging, a fast AC
reset circuit is used. The AC input is rectified and filtered by
D13 and C30. While the AC supply is present, Q3 is on and Q1
is off, allowing normal device operation. However when AC is
removed, Q1 pulls down the V pin and resets the latch. The supply
will then return to normal operation when AC is again applied.
Transistor Q2 provides an additional lower UV threshold to the
level programmed via R1, R2 and the V pin. At low input AC
voltage, Q2 turns off, allowing the X pin to float and thereby
disabling switching.
A simple feedback circuit automatically regulates the output
voltage. Zener VR3 sets the output voltage together with the
voltage drop across series resistor R8, which sets the DC gain
of the circuit. Resistors R10 and C28 provide a phase boost to
improve loop bandwidth.
Diodes D6 and D7 are low-loss Schottky rectifiers, and
capacitor C20 is the output filter capacitor. Inductor L3 is a
common mode choke to limit radiated EMI when long output
cables are used and the output return is connected to safety
earth ground. Example applications where this occurs include
PC peripherals, such as inkjet printers.
C8
1 nF
250 VAC 0.5 W
1 10
2
9
R25
100 Ω
5
C13
3
10 µF
NC
50 V
C5
4
10 nF
1 kV
D5
T1
LL4148
EF25
D2
FR107
VR5
C9
1N5250B
R22
1 µF
20 V
V
2 MΩ 100 V
C
X
R6
C6 6.8 Ω
100 nF
50 V
C7
47 µF
16 V
TOP252-262
R19 C26
68 Ω 100 pF
1 kV
C20 C31
330 µF 22 µF
L2
50 V
50 V
3.3 µH
D6-D7
STPS3150
C10
1 nF
250 VAC
R10
56 Ω
R8
1.5 kΩ
C28
330 nF
50 V
VR3
1N5255B
28 V
U2A
PC817D
R20
130 kΩ
R9
2 kΩ
PI-4833-092007
32 V
625 mA, 2.5 A
L3
PK
RTN
47 µH
C29
220 nF
50 V
23
Rev. J 08/16