TOP266KG Power Integrations, TOP266KG Datasheet - Page 17

• Manufacturer Part Number: TOP266KG
• Description: IC OFFLINE SWITCHER 39W 58W
• Manufacturer: Power Integrations
• Series: TOPSwitch®-JXr

Specifications of TOP266KG

• Output Isolation: Isolated
• Frequency Range: 66 ~ 132kHz
• Voltage - Output: 725V
• Power (watts): 39W
• Operating Temperature: -40°C ~ 125°C
• Package / Case: 12-BSOP (0.350", 8.89mm Width) Exposed Pad
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: 596-1399

Very Low No-load, High Efficiency, 30 W, Universal Input,
Open Frame, Power Supply
The circuit shown in Figure 26 below shows an 85 VAC to
265 VAC input, 12 V, 2.5 A output power supply. The goals of
the design were highest full load efficiency, average efficiency
(average of 25%, 50%, 75% and 100% load points), very low no-
load consumption. Additional requirements included latching
output overvoltage shutdown and compliance to safety agency
limited power source (LPS) limits. Actual efficiency and no-load
performance is summarized in the table shown in the schematic
which easily exceed current energy efficiency requirements.
In order to meet these design goals the following key design
decisions were made.
PI part selection
•
The device selected for this design was based on the 85-265 VAC,
Open Frame, PCB heat sinking column of power table (Table 1).
One device size smaller was selected (TOP266V vs TOP267V)
due to the ambient specification of 40 °C (vs the 50°C assumed
in the power table) and the optimum PCB area and layout for
the device heat sink. The subsequent thermal and efficiency
data confirmed this choice. The maximum device temperature
was 107°C at full load, 40 °C, 85 VAC, 47 Hz (worst case
conditions) and average efficiency exceeded 83% ENERGY
STAR and EuP Tier 2 requirements.
Transformer Core Selection
•
Figure 26. Schematic of High Efficiency 12 V, 30 W, Universal Input Flyback Supply With Very Low No-load.
www.powerint.com
Ambient of 40 °C allowed one device size smaller than
indicated by the power table
132 kHz switching frequency allowed the selection of smaller
core for lower cost
L
N
85 - 264
3.15 A
VAC
F1
14 mH
L1
No-load Input Power (mW)
Full Load Efficiency (%)
Input Voltage (VAC)
Average Efficiency (%)
275 VAC
100 nF
C1
1N4007
1N4007
81.25
D1
D3
60.8
85
83.94
84.97
61.98 74.74
1N4007
1N4007
115
82 µF
400 V
D2
D4
C3
86.21
85.13
230
14.3 kΩ
5.1 MΩ
5.1 MΩ
R15
1%
R1
R2
TOPSwitch-JX
10 MΩ
10 MΩ
TOP266VG
R3
R4
U1
10 kΩ
1/2 W
R5
P6KE180A
VR1
D
S
FR107
CONTROL
D5
X
V
BAV19WS
4.7 nF
1 kV
191 kΩ
C4
F
R12
D6
1%
C
6
4
NC
The size of the magnetic core is a function of the switching
frequency. The choice of the higher switching frequency of
132 kHz allowed for the use of a smaller core size. The higher
switching frequency does not negatively impact the efficiency in
TOPSwitch-JX designs due its small drain to source capacitance
(C
Line Sense Resistor Values
•
Line sensing is provided by resistors R1 and R2 and sets the
line undervoltage and overvoltage thresholds. The combined
value of these resistors was increased from the standard 4 MW
to 10.2 MW. This reduces the current into the V pin, and
therefore contribution to no-load input power, from ~26 mW to ~
10 mW. To compensate the resultant change in the UV
threshold resistor R12 was added between the CONTROL and
VOLTAGE-MONITOR pins. This adds a DC current equal to ~16
mA into the V pin, requiring only 9 mA to be provided via R1 and
R2 to reach the V pin UV threshold current of 25 mA and setting
the UV threshold to approximately 95 VDC.
This technique does effectively disable the line OV feature as
the resultant OV threshold is raised from ~450 VDC to ~980 VDC.
However in this design there was no impact as the value of
input capacitance (C3) was sufficient to allow the design to
withstand differential line surges greater than 1 kV without the
peak drain voltage reaching the BV
Specific guidelines and detailed calculations for the value of R12
may be found in the TOPSwitch-JX Application Note.
100 nF
250 VAC
50 V
NC
C9
OSS
EF25
ZMM5245B-7
Increasing line sensing resistance from 4 MW to 10.2 MW to
reduce no-load input power dissipation by 16 mW
C11
1 nF
T1
VR3
) as compared to that of discrete MOSFETs.
11,12
1
2
7,8
BAV21WS-
7-F
D7
1/8 W
6.8 Ω
R16
47 µF
25 V
C10
10 Ω
200 V
R9
LTV817D
C12
1 nF
47 µF
U2B
25 V
C7
SB560
D8,9
22 Ω
R17
680 µF
25 V
C14
47 nF
110 Ω
50 V
C18
R18
680 µF
25 V
C15
TOP264-271
DSS
470 Ω
LMV431A
R19
LTV817D
LL4148
3.3 µH
1%
D10
U3
rating of U1.
U2A
L2
33 nF
50 V
C20
100 µF
25 V
C16
PI-5775-030810
10 kΩ
86.6 kΩ
R23
1%
R21
1%
12 V, 2.5 A
RTN
Rev. C 11/10
17