Application Note AN-47
TOPSwitch-JX Family
Design Guide
Introduction
The TOPSwitch™-JX is a highly integrated monolithic off-line
switcher IC designed for off-line power supplies. TOPSwitch-JX
integrated circuits enable design of power supplies up to 244 W,
while providing high efficiency under all load conditions.
TOPSwitch-JX also provides very good performance at low load
and during standby (no-load) operation. The TOPSwitch-JX
family allows the designer to easily meet efficiency requirements
for the latest energy-efficiency standards. Innovative and
proprietary features enable design of compact and cost effective
switching power supplies while reducing overall design cycle time
and system cost. The TOPSwitch-JX family also enables the
design of power supplies with robust functionality and provides
enhanced safety features such as output overvoltage protection,
overload power limiting and hysteretic thermal protection.
Each member of the family has a high-voltage power MOSFET
and its controller combined monolithically. Internal start-up bias
current is drawn from a high-voltage current source connected to
the DRAIN pin, eliminating the need for external start-up circuitry.
The internal oscillator is frequency modulated (jitter) to reduce
EMI. In addition, the ICs have integrated functions that provide
system-level protection. The auto-restart function limits power
dissipation in the MOSFET, the transformer and the output diode
during overload, output short-circuit or open-loop conditions.
The auto-recovering hysteretic thermal shutdown function also
disables MOSFET switching if the junction temperature exceeds
safe limits. A programmable undervoltage/overvoltage (UV/OV)
AC
IN
detection feature allows glitch free start-up and shutdown of the
power supply during line sag or line surge conditions. Power
Integrations’ EcoSmart® technology enables supplies designed
around the TOPSwitch-JX family to consume less than 100 mW
at no-load and maintain constant efficiency over the full line and
load range. TOPSwitch-JX family of solutions easily meets energy
efficiency standards such as European Code of Conduct, EC
EuP and ENERGY STAR.
Basic Circuit Configuration
The discussion of application-specific requirements, such as
constant current, constant power outputs, etc., are beyond the
scope of this design guide. However, such requirements may be
satisfied by adding additional circuitry to the basic converter
descriptions shown here. For more information on additional
circuit capabilities, design examples and other information visit the
Power Integrations web site or contact your PI sales
representative.
Scope
This application note is intended for engineers designing an
isolated AC-DC flyback power supply using the TOPSwitch-JX
family of devices. It provides guidelines to enable an engineer
to quickly select key components and also complete a suitable
transformer design. To help simplify the task, the application
note refers directly to the PI Xls design spreadsheet that is part of
the PI Expert® design software suite available at no charge from
+
DC
OUT
-
RLS
ROVP VROVP
D
V
CONTROL
TOPSwitch-JX
S
C
X
F
RIL
PI-5840-021110
Figure 1. Typical TOPSwitch-JX Flyback Power Supply With Primary Sensed Output Overvoltage Protection, Line Undervoltage Lockout, Line Overvoltage Shutdown
and Programmable Current Limit.
www.power.com
December 2017
Application Note
AN-47
www.power.com. The basic configuration used in TOPSwitch-JX
flyback power supplies is shown in Figure 1, which also serves
as the reference circuit for component identifications used in
descriptions throughout this application note.
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In addition to this application note, the reader may also find the
TOPSwitch-JX Reference Design Kits (RDKs) useful. Each
contains a fully functional engineering prototype board,
engineering report and device samples. Further details on
downloading PI Expert, and obtaining an RDK and updates to
this document can be found at www.power.com.
•
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Quick Start
Readers familiar with power supply design and Power Integrations
design software may elect to skip the step-by-step design
approach described later, and can use the following information
to quickly design the transformer and select the components
necessary for a first prototype. For this approach, only the
information described below needs to be entered into the PI Xls
spreadsheet, other parameters will be automatically selected
based on typical design requirements. References to
spreadsheet cell locations are provided in square brackets [cell
reference].
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Enter AC input voltage range VACMIN, VACMAX and minimum line
frequency fL [B3, B4, B5]
Enter nominal output voltage VO [B6]
For designs with a peak load condition, enter average output
power, else enter continuous (average) output power [B7]
For designs with a peak load current, enter peak load current
else leave blank [B8]
Enter efficiency estimate [B11]
0.8 for universal input voltage (85-265 VAC) or single
100/115 VAC (85-132 VAC) and 0.85 for a single 230 VAC
(185-265 VAC) design. Adjust the number accordingly
based on measurement at peak load and VACMIN.
Enter loss allocation factor Z [B12]
• 0.5 for typical application (adjust the number accordingly
after first prototype-board evaluation)
Enter input capacitance (CIN) [B15]
• 2~3 µF/W for universal (85-265 VAC) or single (100/115 VAC)
• Use 1 µF/W single 230 VAC for single (185-265 VAC)
Select the TOPSwitch-JX part from the drop down list or enter
directly [B19]
• Select the device in the table below according to output
power and line input voltage
• Enter operating frequency – [B24]
• “H” for 66 kHz operation
• “F” for 132 kHz operation
Enter core type (if desired) from drop down menu [B54]
• A suggested core size will be selected automatically if
none is entered
If any warnings are generated, make changes to the design by
following instructions in spreadsheet column F
Build transformer
Select key components
See Steps 7 through 12.
Build prototype and iterate design as necessary, replacing
estimates in the spreadsheets with measured values as
appropriate (e.g. efficiency, VMIN).
Power Integrations offers a transformer prototyping service
and links to other vendors: for details see www.power.com/
componentsuppliers.htm
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Output Power Table
Product5
PCB Copper Area1
230 VAC ±15%4
85-265 VAC
Open
Open
2
Adapter
Adapter2
Frame3
Frame3
Product5
Metal Heat Sink1
230 VAC ±15% 4
85-265 VAC
Open
Open
2
Adapter
Adapter2
Frame3
Frame3
TOP264VG
21 W
34 W
12 W
22.5 W
TOP264EG/VG
30 W
62 W
20 W
43 W
TOP265VG
22.5 W
36 W
15 W
25 W
TOP265EG/VG
40 W
81 W
26 W
57 W
TOP266VG
24 W
39 W
17 W
28.5 W
TOP266EG/VG
60 W
119 W
40 W
86 W
TOP267VG
27.5 W
44 W
19 W
32 W
TOP267EG/VG
85 W
137 W
55 W
103 W
TOP268VG
30 W
48 W
21.5 W
36 W
TOP268EG/VG
105 W
148 W
70 W
112 W
TOP269VG
32 W
51 W
22.5 W
37.5 W
TOP269EG/VG
128 W
162 W
80 W
120 W
TOP270VG
34 W
55 W
24.5 W
41 W
TOP270EG/VG
147 W
190 W
93 W
140 W
TOP271VG
36 W
59 W
26 W
43 W
TOP271EG/VG
177 W
244 W
118 W
177 W
Table 1. Output Power Table.
Notes:
1. See Key Application Considerations in device data sheet section for more details.
2. Maximum continuous power in a typical non-ventilated enclosed adapter measured at +50 °C ambient temperature.
3. Maximum continuous power in an open frame design at +50 °C ambient temperature.
4. 230 VAC or 110/115 VAC with doubler.
5. Packages: E: eSIP-7C, V: eDIP-12. See Part Ordering Information in device data sheet.
2
Rev. B 12/17
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AN-47
Application Note
Step-by-Step Transformer Design
Procedure Introduction
Power (W)
As average power increases, based on the measured transformer and device temperature, it may be necessary to select a
larger transformer to allow increased copper area for the
windings and/or to increase the amount of device heat sinking.
The power table (Table 1) provides guidance for peak and
continuous (average) power levels obtainable in both sealed
adapter and open frame applications. For the V package without
an external heat sink, the power values for adapter and open
frame are thermally limited. The peak values represent the
electrically limited output power, assuming operation at current
limit (ILIM(MIN)). For the E package, the adapter power values are
also thermally limited, however, the open frame values are
electrically limited and therefore also represent the peak output
power. As the continuous power values are thermally limited,
they indicate the upper limit of continuous power for worst case
conditions but may vary depending on the specific application.
For example, if the peak power condition has a very low duty
cycle, such as the 1-second peak required to close the drawer in
a DVD player, then the thermal rise of the device (and transformer)
is only a function of the continuous average power. However, if
the peak power is repetitive with a significant duty cycle, then it
would need to be considered as a limiting factor in the design.
Figure 2 shows how to calculate the average power requirements
for a design with two different peak load conditions.
PAVE = P1 + ]P3 - P1 g # d1 + ]P2 - P1 g # d2
Dt
Dt
d1 = T 1 , d2 = T 2
P2
P1
∆t1
∆t2
Time (t)
T
Figure 2. Continuous (average) Output Power Calculation Example.
The peak power is used to select the TOPSwitch-JX device and
design the transformer for power delivery at minimum input line
voltage while continuous (or average power if the peak load is
periodic) is used for thermal design and may affect the size of
the transformer and the heat sink.
Step 1 – Enter Application Variables VACMIN, VACMAX, fL ,
VO, PO(AVE), PO(PEAK), h, Z, VB, tC, CIN
Determine the input voltage range from Table 2.
Nominal Input Voltage (VAC)
VACMIN
VACMAX
100/115
85
132
230
195
265
Universal
85
265
Table 2. Standard Worldwide Input Line Voltage Ranges.
Line Frequency, fL
50 Hz for universal or single 100 VAC, 60 Hz for single 115 VAC
input. 50 Hz for single 230 VAC input. These values represent
typical line frequencies rather than minimums. For most
applications this gives adequate overall design margin. For
absolute worst case or based on the product specification,
reduce these numbers by 6% (47 Hz or 56 Hz). For half-wave
rectification, use fL /2. For DC input, enter the voltage directly
into Cells B67 and B68.
Where PX are the different output power conditions, Dt X are the
durations of each peak power condition and T is the period of
one cycle of the pulsed load condition.
The design procedure requires both peak and continuous
(average) powers to be specified. If there is no peak power
requirement for the design, the same value should be used for
both continuous and peak power.
Design title
ENTER APPLICATION VARIABLES
VACMIN
VACMAX
fL
VO
PO_AVG
PO_PEAK
Heatsink Type
Enclosure
n
Z
VB
tC
CIN
P3
PI-4329-030906
The design flow allows for design of power supplies both with or
without a peak output power requirement. For peak power
requirements the device current limit is programmed to enable
the delivery of peak power for a short duration limited only by
thermal characteristics of the TOPSwitch-JX package and
ratings of other components in the circuit.
85
265
50
5.00
35.00
External
Adapter
Volts
Volts
Hertz
Volts
Watts
35.00 Watts
External
0.80
0.50
12
3.00
68.0
%/100
Volts
ms
68 uFarads
Minimum AC Input Voltage
Maximum AC Input Voltage
AC Mains Frequency
Output Voltage (main)
Average Output Power
Peak Output Power
Heatsink Type
Open Frame enclosure assume sufficienct airflow while adapter means a sealed enclosure.
Efficiency Estimate
Loss Allocation Factor
Bias Voltage - Verify that VB is > 8 V at no load and VMAX
Bridge Rectifier Conduction Time Estimate
Input Filter Capacitor
Figure 3. Application Variable Section of TOPSwitch-JX Design Spreadsheet.
3
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Rev. B 12/17
Application Note
AN-47
DC INPUT VOLTAGE PARAMETERS
VMIN
VMAX
Minimum DC Input Voltage
Maximum DC Input Voltage
74 Volts
375 Volts
Figure 4. DC Input Voltage Parameters Showing Grey Override Cells for DC Input Designs.
Nominal Output Voltage, VO (V)
Enter the nominal output voltage of the main output during the
continuous load condition. Generally the main output is the
output from which feedback is derived.
Continuous / Average Output Power PO(AVE) (W)
Enter the average output power of the power supply. If the
power supply is a multiple output power supply, enter the sum
total power of all the outputs.
Peak Output Power PO(PEAK) (W)
Enter the peak output power under peak load conditions. If the
design does not have a peak load condition, then leave this
entry blank and a value equal to PO(AVE) is assumed. PO(PEAK) is
used to calculate the primary inductance value.
In multiple output designs, the output power of the main output
(typically the output from which feedback is taken) should be
increased such that the peak power (or maximum continuous
output power as applicable) matches the sum of the output
power from all the outputs in the design. The individual output
voltages and currents should then be entered at the bottom of
the spreadsheet (cells [B122 to B168]).
Select Heat sink Type and Enclosure
The enclosure determines the maximum power capability of the
TOPSwitch-JX device. If the power supply is going to be
housed in a sealed plastic case (much like an laptop power
supply) then select the adapter enclosure. If on the other hand
the power supply has better air flow, select the open frame
enclosure.
Depending on the package selected an appropriate heat sink
type can be selected. The E package always needs an external
heat sink but a V package may be used either with or without an
external heat sink. When used without a heat sink the copper
area on the PCB provides the only heat sinking. However due
to the increased thermal resistance of the PCB, as compared to
an external heat sink, the maximum power capability in this
configuration will be reduced.
Power Supply Efficiency, h
Enter the estimated efficiency of the complete power supply
measured at the output terminals under peak load conditions
and worst-case line (generally lowest input voltage). Start with a
value of 80% for VACMIN of 85 VAC and 85% for 195 VAC. These
are typical for a design where the majority of the output power is
drawn from an output voltage of 12 V and no output current
sensing is present on the secondary. For a 5 V output starting
values of 75% for VACMIN of 85 VAC and 80% for 195 VAC are
recommended. Once a prototype has been constructed, then
measured efficiency can be entered and a further transformer
iteration performed, as appropriate.
Power Supply Loss Allocation Factor, Z
This factor represents the proportion of losses between the
primary and the secondary of the power supply. Z factor is
used together with the efficiency number to determine the
actual power that must be delivered by the power stage. For
example, losses in the input stage (EMI filter, rectification, etc)
are not processed by the power stage (transferred through the
transformer) and therefore, although they reduce efficiency, the
transformer design is not affected by their effect on efficiency.
Z=
Secondary Side Losses
Total Losses
Examples of primary side losses are losses incurred in the input
rectifier and EMI filter, MOSFET conduction losses and primary
side winding losses. Examples of secondary side losses include
the losses in secondary diode, secondary windings and core
losses, losses associated with the primary side clamp circuit
and the bias winding. For designs that do not have a peak power
requirement, a value of 0.5 is recommended. For designs with
a peak power requirement, enter 0.65. This difference accounts
for increased input stage losses under peak power loading
Bias Winding Output Voltage (VB)
Enter the voltage at the output of the bias winding output. A
starting value of 15 V is recommended. The voltage may be set
to different values, for example, when the bias winding output is
also used as a primary side (non-isolated) auxiliary output. Higher
voltages increase no-load input power while values below 8 V
are not recommended as at light load there may be insufficient
voltage to correctly bias the optocoupler, causing loss of output
regulation. A 10 mF, 50 V electrolytic capacitor is the recommended
minimum value for the bias winding output filter.
Bridge Diode Conduction Time, tC (ms)
Enter a bridge diode conduction time of 3.00 ms if there is no
better data available.
Total Input Capacitance, CIN (mF)
Table 3 suggests suitable multiplication factors to be used for
calculating input capacitance for different AC input voltage ranges.
AC Input Voltage (VAC)
Total Input Capacitance per
Watt Output Power (mF/W)
Full Wave Rectification
100/115
2–3
230
1
85-265
2–3
Table 3. Suggested Total Input Capacitance for Different Input Voltage Ranges.
The capacitance is used to calculate the minimum and
maximum DC voltage across the bulk capacitor and should be
selected to keep the minimum DC input voltage, VMIN >70 V.
4
Rev. B 12/17
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AN-47
Application Note
Step 2 – Enter TOPSwitch-JX Variables:
Device, Current Limit, VOR, VDS, VD, Select the
Correct TOPSwitch-JX Device
First, refer to the TOPSwitch-JX power table and select a device
based on the peak output power design. Then compare the
continuous power to adapter column numbers in the power
table, if the power supply is of fully enclosed type, or compare to
the open-frame column if the power supply is an open-frame
design. If the continuous power exceeds the value given in the
power table (Table 1), then the next largest device should be
selected. Similarly, if the continuous power is close to the
adapter power levels given in the power table, then it may be
necessary to switch to a larger device based on the measured
thermal performance of the prototype.
External Current Limit Reduction Factor, KI
The factor KI sets the value of the current limit threshold. This
allows the current limit level to be adjusted slightly above the
minimum peak current (IP) required for power delivery. This
optimizes the transformer design by limiting the peak flux density
(BP) during overload and start-up.
For higher efficiency and improved thermal performance, KI also
allows the selection of a larger TOPSwitch-JX device to be used
than required for power delivery by reducing KI, such that the
current limit of the larger device is equal to the original smaller
part selected.
High Line Operating Mode
This parameter confirms the mode of operation of the
TOPSwitch-JX at high line. It is desirable to operate in fullfrequency mode at high line as the switching frequency jitter
feature will be enabled. (See TOPSwitch-JX data sheet for an
explanation of operating modes). This provides improved EMI
performance.
Reflected Output Voltage, VOR (V)
This parameter is the secondary winding voltage during diode
conduction, reflected back to the primary through the turns ratio
of the transformer. The default value is 135 V; however the
acceptable range for VOR is between 80 V and 135 V, provided
that no warnings in the spreadsheet are triggered. For design
optimization purposes, the following trade-offs should be
considered:
1. Higher VOR allows increased power delivery at VMIN, which
minimizes the input capacitance value and maximizes power
delivery from a given TOPSwitch-JX device.
2. Higher VOR reduces the voltage stress on the output diodes,
which in some cases may allow the use of a lower forward
drop Schottky diode for higher efficiency.
3. Higher VOR can increase leakage inductance and increase
clamp losses that reduces efficiency of the power supply and
degrade cross regulation in multiple output designs.
4. Higher VOR increases peak and RMS current on the secondary side, which may increase secondary side copper and
diode losses.
Optimal selection of the VOR value depends on the specific
application and is based on a compromise between the factors
mentioned above.
For lower voltage outputs (approximately 5 V or multiple output
designs) a lower VOR of approximately 100 V - 110 V is usually
better suited. For higher voltage outputs (12 V and above) a
higher VOR of approximately 120 and 135 V is better suited.
Values below 80 V are not usually recommended. Low VOR may
cause excessive triggering of the MOSFET self-protection feature
during start-up, especially in designs where all outputs are >5 V
(see Table 4 for a summary).
TOPSwitch-JX ON-State DRAIN to SOURCE Voltage, VDS (V)
This parameter is the average ON state voltage developed
across the DRAIN and SOURCE pins of TOPSwitch-JX. By
default, if the grey override cell is left empty, a value of 10 V is
assumed. Use the default value if no better data is available.
Output Diode Forward Voltage Drop, VD (V)
Enter the average forward voltage drop of the (main) output diode.
Use 0.5 V for a Schottky diode or 0.7 V for a PN diode if no
better data is available. By default, a value of 0.5 V is assumed.
Bias Winding Diode Forward Voltage Drop, VDB (V)
Enter the average forward voltage drop of the bias winding
output diode. Use 0.7 V for a PN diode.
Ripple to Peak Current Ratio, KP
Figure 6 shows KP < 1, indicating continuous conduction mode,
KP is the ratio of ripple to peak primary current.
ENTER TOPSWITCH-JX VARIABLES
TOPSwitch-JX
Chosen Device
KI
ILIMITMIN_EXT
ILIMITMAX_EXT
Frequency (F)=132kHz, (H)=66kHz
fS
fSmin
fSmax
High Line Operating Mode
VOR
VDS
VD
VDB
KP
TOP266E
TOP266E
Power Out
Universal / Peak
40 W / 86 W
0.53
1.257 Amps
1.446 Amps
F
F
132000 Hertz
119000 Hertz
145000 Hertz
FF
135.00
0.50
0.70
0.50
Volts
10 Volts
Volts
Volts
115 Doubled/230V
60W
External Ilimit reduction factor (KI=1.0 for default ILIMIT, KI
