Power integrations InnoSwitch3 Installation and operating instructions

Application Note AN-72
InnoSwitch3 Family
www.power.com October 2018
Design Guide
Introduction
InnoSwitch™3 devices combine a high-voltage power MOSFET switch,
with both primary-side and secondary-side controllers, an innovative
high-speed magneto-coupling communications technology and a
synchronous rectication driver into one isolated, safety-rated device.
The incorporation of Fluxlink™, which transmits information safely and
reliably across the isolation barrier, eliminates the need for an
optocoupler - used in the feedback loop of conventional power
conversion circuits. This reduces component count and eliminates the
lifetime and reliability limitations inherent in opto-feedback devices.
The InnoSwitch3 integrated circuits feature a variable frequency,
variable peak-current control scheme which together with quasi-
resonant switching and synchronous rectication ensure very high
conversion efciency across the load range. The family can be used to
create power supplies up to 65 W output, including CV/CC chargers
that easily meet average-power-supply-efciency requirements and
offers very low no load input power and outstanding standby
performance. Power Integrations’ EcoSmart™ technology used in
InnoSwitch3 ICs enables designs that consume as little as 15 mW of
no-load power and makes the family ideal for applications that must
meet energy efciency standards such as the United States
Department of Energy DoE 6, California Energy Commission (CEC) and
European Code of Conduct.
The primary-side yback controller in InnoSwitch3 can seamlessly
transition between DCM, QR and CCM switching. The primary
controller consists of start-up circuitry, a frequency jitter oscillator, a
receiver circuit that is magnetically coupled to the secondary side, a
current limit controller, audible noise reduction engine, overvoltage
detection circuitry, lossless input line sensing circuit, over-temperature
protection and a 650 V or 725 V power MOSFET.
The InnoSwitch3 secondary controller consists of a transmitter circuit
that is magnetically coupled to the primary-side, a constant voltage
(CV) and constant current (CC) control circuit, synchronous-rectier-
MOSFET driver, QR mode circuit, and a host of integrated protection
features including output overvoltage, overload, power limit, and
hysteretic thermal overload protection.
At start-up the primary controller is limited to a maximum switching
frequency of 25 kHz and 70% of the maximum programmed current
limit. An auto-restart function limits power dissipation in the switching
MOSFET, transformer, and output SR MOFET during overload,
short-circuit or open-loop fault conditions.

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Figure 1. Typical Adapter Power Supply Schematic using InnoSwitch3 with Line Undervoltage Lockout, Line Overvoltage Shutdown, Constant Output Current Limit
and Quasi-Resonant Synchronous MOSFET Rectier and Integrated Output Overvoltage Protection.
Basic Circuit Conguration
The circuit in Figure 1 shows the basic conguration of a yback
power supply designed using InnoSwitch3. Different output power
levels may require different values for some circuit components, but
the general circuit conguration remains similar. Advanced features
such as line overvoltage and undervoltage protection, primary or
secondary sensed output overvoltage protection and constant current
limit programming are implemented using very few passive components.
Scope
This application note is intended for engineers designing an isolated
AC-DC yback power supply or charger using the InnoSwitch3 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, this application note refers directly
to the PIXls designer spreadsheet that is part of the PI Expert™
design software suite available online (https://piexpertonline.power.
com/site/login). The basic conguration used in InnoSwitch3 yback
power supplies is shown in Figure 1, which also serves as the
reference circuit for component identication used in the description
throughout this application note.
In addition to this application note, there is the InnoSwitch3 reference
design kit (RDK) containing an engineering prototype board as well
as device samples that provides an example of a working power
supply. Further details on downloading PI Expert, obtaining an RDK
and updates to this document can be found at www.power.com.
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 for a rst prototype.
For this approach, only the information described below needs to be
entered into the PIXls spreadsheet, other parameters will be
automatically selected based on a typical design. References to
spreadsheet line numbers are provided in square brackets [line
reference].
PI-8465-041818
Secondary
Control IC
L
VOUT
RTN
RT
FR
C1C2
RLS1
RSN CSN
RS
RFB(UPPER)
CFB
RPH
CPH
CBPS
CSR RSR COUT
RFB(LOWER)
DSN
DBIAS
RBP
RLS2
RFWD
RIS
CBPP
CBIAS
N
SR FET
Primary FET
and Controller
D V
S IS
VOUT
BPS FB
GND
SR
BPP
FWD
InnoSwitch3
tO
LF
FB
BRD
CY

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Table 1. Output Power Tables of InnoSwitch3-CE and EP.
• Enter AC input voltage range and line frequency, VAC_MIN [B3],
VAC_MAX [B4], LINEFREQ [B6]
• Enter input capacitance, CAP_INPUT [B7]
• 3 µF / W for universal (85-265 VAC) or single (100/115 VAC) line.
A more aggressive value of 2 µF / W can be used for many
charger designs that do not need to meet hold up time require-
ment
• Use 1 µF/W for 230 VAC or for single (185-265 VAC) line. If this
cell is left blank then the capacitance value for a VMIN of 70 V
(universal input) or 150 V (single 230 VAC) is calculated. Often
this will lead to an optimal input lter capacitance value
• Enter nominal output voltage, VOUT [B8]
• Enter desired cable drop compensation, PERCENT_CDC [B9]
• “0%” for no cable compensation
• “1% - 6%” for featured H-code trim
• Enter continuous output current, IOUT [B10]
• Enter efciency estimate, EFFICIENCY [B12]
• 0.83 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 after measuring the
efciency of the rst prototype-board at max load and VACMIN
• Select power supply enclosure, ENCLOSURE [B14]
• Select current limit mode, ILIMIT_MODE [B19]
• Two current limit congurations are available, STANDARD or
INCREASED
• Select InnoSwitch3 from drop-down list or enter directly [B20]
• Select the device from Table 1 according to output power, input
voltage and application
• InnoSwitch3-CE for CV/CC yback application
• InnoSwitch3-EP for CV/CC yback application with 725 V
MOSFET
• Enter desired maximum switching frequency at full load, FSWITCH-
ING_MAX [B34]
• Enter desired reected output voltage, VOR [B35]
• Enter core type (if desired), CORE [B63] from drop down menu
• Suggested core size will be selected automatically if none is
entered [B63]
• For custom core, enter CORE CODE [B64], and core parameters
from [B65] to [B72]
• Enter secondary number of turns [B88]
If any warnings are generated, make changes to the design by
following instructions in spreadsheet column D.
• Build transformer as suggested in “Transformer Construction” tab
• Select key components
• Build prototype and iterate design as necessary, entering measured
values into spreadsheet where estimates were used (e.g. efciency,
VMIN). Note that the initial efciency estimate is very conservative.
Output Power Table
Product3
230 VAC ± 15% 85-265 VAC
Peak or
Open Frame1,2
Peak or
Open Frame1,2
INN3672C 12 W 10 W
INN3673C 15 W 12 W
INN3674C 25 W 20 W
INN3675C 30 W 25 W
INN3676C 40 W 36 W
INN3677C 45 W 40 W
Notes:
1. Minimum continuous power in a typical non-ventilated enclosed typical size
adapter measured at 40 °C ambient. Max output power is dependent on the
design. With condition that package temperature must be < 125 °C.
2. Minimum peak power capability.
3. Package: InSOP-24D.
Output Power Table
Product3
230 VAC ± 15% 85-265 VAC
Adapter1Open
Frame2Adapter1Open Frame2
INN3162C 10 W 12 W 10 W 10 W
INN3163C 12 W 15 W 12 W 12 W
INN3164C 20 W 25 W 15 W 20 W
INN3165C 25 W 30 W 22 W 25 W
INN3166C 35 W 40 W 27 W 36 W
INN3167C 45 W 50 W 40 W 45 W
INN3168C 55 W 65 W 50 W 55 W
Notes:
1. Minimum continuous power in a typical non-ventilated enclosed typical size
adapter measured at 40 °C ambient. Max output power is dependent on the
design. With condition that package temperature must be < 125 °C.
2. Minimum peak power capability.
3. Package: InSOP-24D.

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Step-by-Step Design Procedure
This design procedure uses the PI Expert design software (available
from Power Integrations), which automatically performs the key
calculations required for an InnoSwitch3 yback power supply design.
PI Expert allows designers to avoid the typical highly iterative design
process. Look-up tables and empirical design guidelines are provided
in this procedure where appropriate to simplify the design task.
Iterate the design to eliminate warnings. Any parameters outside the
recommended range of values can be corrected by following the
guidance given in the right hand column. Once all warnings have
been cleared, the output transformer design parameters can be used
to create a prototype transformer.
Step 1 ‒ Application Variables
Enter: VIN_MIN, VIN_MAX, LINEFREQ, CAP_INPUT, VOUT,
PERCENT_CDC, IOUT, EFFICIENCY, FACTOR_Z, and
ENCLOSURE
Minimum and Maximum Input Voltage, V_MIN, V_MAX (VAC)
Determine the input voltage range from Table 2 for a particular
regional requirement.
Line Frequency, LINEFREQ (Hz)
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 minimum. For most applications this gives
adequate overall design margin. For absolute worst-case or based on
the product specication reduce these numbers by 6% (47 Hz or 56 Hz).
Total Input Capacitance, CAP_INPUT (µF)
Enter total input capacitance using Table 3 for guidance.
Region Nominal Input
Voltage (VAC)
Minimum Input
Voltage (VAC)
Maximum Input
Voltage (VAC)
Nominal Line
Frequency (Hz)
Japan 100 85 132 50 / 60
United States, Canada 120 90 132 60
Australia, China, European Union Countries,
India, Korea, Malaysia, Russia 230 185 265 50
Indonesia, Thailand, Vietnam 220 185 265 50
Rest of Europe, Asia, Africa, Americas
and rest of the world
115, 120, 127 90 155 50 / 60
220, 230 185 265 50 / 60
240 185 265 50
Visit: https://en.wikipedia.org/wiki/Mains_electricity_by_country
Table 2. Standard Worldwide Input Line Voltage Ranges and Line Frequencies.
2
APPLICATION VARIABLES
Design Title
3 VIN_MIN 85 85 V Minimum AC input voltage
4 VIN_MAX
265
265 V Maximum AC input voltage
5 VIN_RANGE UNIVERSAL Range of AC input voltage
6 LINEFREQ 60 Hz AC Input voltage frequency
7 CAP_INPUT 40.0 uF Input capacitor
8 VOUT
5.00
5.00 V Output voltage at the board
9 PERCENT_CDC
0%
0%
Percentage (of output voltage) cable drop
compensation desired at full load
10 IOUT 4.00 4.00 A Output current
11 POUT 20.00 W Output power
12 EFFICIENCY 0.89 0.89
AC-DC efficiency estimate at full load given that
the converter is switching at the valley of the
rectified minimum input AC voltage
13 FACTOR_Z 0.50 Z-factor estimate
14 ENCLOSURE ADAPTER ADAPTER Power supply enclosure
Figure 2. Application Variable Section of InnoSwitch3-CE Design Spreadsheet with Gray Override Cells.

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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.
Nominal Output Voltage, VOUT (V)
Enter the nominal output voltage of the main output at full load.
Usually the main output is the output from which feedback is derived.
Cable Compensation, PERCENT_CDC (%)
Select the appropriate cable compensation depending on the choice
of cable for the design. If this power supply is not supplied with a
cable, use the default 0%. (For InnoSwitch3-EP, this feature is not
available)
Power Supply Output Current, IOUT (A)
This is the maximum continuous load current of the power supply.
Output Power, POUT (W)
This is a calculated value and will be automatically adjusted based on
cable compensation selected.
Power Supply Efciency, EFFICIENCY (η)
Enter the estimated efciency of the complete power supply
measured from the input and output terminals under peak load
conditions and worst-case line (generally lowest input voltage). The
table below can be used as a reference. Once a prototype has been
constructed then the measured efciency should be entered and
further transformer iteration(s) can be performed if required.
Power Supply Loss Allocation Factor, FACTOR_ Z
This factor describes the apportioning of losses between the primary
and the secondary of the power supply. Z factor is used together
with the efciency to determine the actual power that must be
delivered by the power stage. For example losses in the input stage
(EMI lter, rectication etc) are not processed by the power stage
(transferred through the transformer) and therefore although they
reduce efciency the transformer design is not effected.
TotalLosses
Secondary Losses
Z=
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. The higher number indicates larger secondary side
losses.
Enclosure
Power device selection will also be dependent on the application
environment. For an open frame application where the operating
ambient temperature is lower than in an enclosed adapter, the PIXls
will suggest a smaller device for the same output power.
Efciency is also a function of output power, low power designs are
most likely around 84% to 85% efcient, whereas with a synchronous
rectier (SR) the efciency would reach 90% typically.
Nominal Output
Voltage (VOUT) Typical Low-Line Range Typical Universal Range Typical High-Line Range
85 VAC - 132 VAC 85 VAC - 265 VAC 185 VAC - 265 VAC
Schottky Diode
Rectier
Synchronous
Rectier
Schottky Diode
Rectier
Synchronous
Rectier
Schottky Diode
Rectier
Synchronous
Rectier
50.84 0.87 0.84 0.88 0.87 0.89
12 0.86 0.90 0.86 0.90 0.88 0.90
Total Input Capacitance per Watt of
Output Power (µF/W)
Total Input Capacitance per Watt of
Output Power (µF/W)
AC Input Voltage (VAC) Full Wave Rectication
Adapter with hold-up time requirement Open Frame or Charger/Adapter without
hold-up time requirement
100 / 115 3 2
230 1 1
85-265 3 2
Table 4. Efciency Estimate Without Output Cable .
Table 3. Suggested Total Input Capacitance for Different Input Voltage Ranges.

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Step 2 – Primary Controller Selection
Enter: Device Current Limit mode, ILIMIT and Generic Device
Code, DEVICE_GENERIC
Generic Device Code, DEVICE_GENERIC
The default option is automatically selected based on input voltage
range, maximum output power and application (i.e. adapter or open
frame).
For manual selection of device size, refer to the InnoSwitch3 power
table in the data sheet and select a device based on the peak output
power. 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 larger device should
be selected. Similarly, if the continuous power is close to the
maximum adapter power given in the power table, it may be
necessary to switch to a larger device based on the measured
thermal performance of the prototype.
Device Current Limit Mode, ILIMIT_MODE
For designs where thermals are not as challenging (such as open
frame applications) and lowest cost is a critical requirement, ILIMIT
MODE allows the choice of an INCREASED current limit mode, this
Figure 3. Primary Controller Selection of InnoSwitch3-CE Design Spreadsheet with Current Limit Mode Selection.
18 PRIMARY CONTROLLER SELECTION
19 ILIMIT_MODE STANDARD STANDARD Device current limit mode
20 DEVICE_GENERIC
Auto
INN31X5 Generic device code
21 DEVICE_CODE INN3165C Actual device code
22 POUT_MAX 22 W
Power capability of the device based on thermal
performance
23 RDSON_100DEG 3.47 Ω
Primary MOSFET on time drain resistance at 100
degC
24 ILIMIT_MIN 0.88 A Minimum current limit of the primary MOSFET
25 ILIMIT_TYP 0.95 A Typical current limit of the primary MOSFET
26 ILIMIT_MAX 1.02 A Maximum current limit of the primary MOSFET
27 VDRAIN_BREAKDOWN 650 V Device breakdown voltage
28 VDRAIN_ON_MOSFET 0.87 V Primary MOSFET on time drain voltage
29 VDRAIN_OFF_MOSFET 508.4 V
Peak drain voltage on the primary MOSFET
during turn-off
will set the peak current of the device equivalent to the next bigger
device’s current limit and allow higher output power. By default,
ILIMIT is set to STANDARD.
On-Time Drain Voltage, VDRAIN_ON_MOSFET (V)
This parameter is calculated based on RDSON_100DEG and primary
RMS current.
Drain Peak Voltage, VDRAIN_OFF_MOSFET (V)
This parameter is the assumed Drain voltage seen by the device
during off-time. The calculation assumes 10% minimum margin from
the breakdown voltage rating of the internal MOSFET and gives a
warning if this is exceeded.
VDRAIN < (VIN_MAX * 1.414) + VOR + VLKPRI – (BVDSS × 10%).
VLKPRI is the voltage induced by the leakage inductance of the
transformer when MOSFET turns off.
Other electrical parameters are displayed based from the data sheet,
RDSON_100DEG, ILIMIT_MIN, ILIMIT_TYP, ILIMIT_MAX,
VDRAIN_BREAKDOWN.

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Figure 4. Worst-Case Electrical Parameters Section of InnoSwitch3-CE Design Spreadsheet with Gray Override Cells.
Table 5. Suggested Maximum Switching Frequency.
33
WORST CASE ELECTRICAL
PARAMETERS
34 FSWITCHING_MAX 80000 80000 Hz
Maximum switching frequency at full load and
valley of the rectified minimum AC input voltage
35 VOR 65.0 V
Seconday voltage reflected to the primary when
the primary MOSFET turns off
36 VMIN 85.95 V
Valley of the rectified minimum AC input voltage
at full power
37 KP 0.66
Measure of continuous/discontinuous mode of
operation
38 MODE_OPERATION CCM Mode of operation
39 DUTYCYCLE 0.433 Primary MOSFET duty cycle
40 TIME_ON 7.46 us Primary MOSFET on-time
41 TIME_OFF 7.09 us Primary MOSFET off-time
42 LPRIMARY_MIN 805.6 uH Minimum primary inductance
43 LPRIMARY_TYP 830.5 uH Typical primary inductance
44 LPRIMARY_TOL
3.0
3.0 % Primary inductance tolerance
45 LPRIMARY_MAX 855.4 uH Maximum primary inductance
46
47 PRIMARY CURRENT
48 IPEAK_PRIMARY 0.95 A Primary MOSFET peak currrent
49 IPEDESTAL_PRIMARY 0.30 A Primary MOSFET current pedestal
50 IAVG_PRIMARY 0.25 A Primary MOSFET average current
51 IRIPPLE_PRIMARY 0.76 A Primary MOSFET ripple current
52 IRMS_PRIMARY 0.41 A Primary MOSFET RMS current
53
54 SECONDARY CURRENT
55 IPEAK_SECONDARY 12.24 A Secondary winding peak current
56 IPEDESTAL_SECONDARY 3.79 A Secondary winding current pedestal
57 IRMS_SECONDARY 6.44 A Secondary winding RMS current
Step 3 – Worst-Case Electrical Parameters
Enter: FSWITCHING_MAX, VOR and LPRIMARY_TOL, or VMIN
Switching Frequency, FSWITCHING_MAX (Hz)
This parameter is the switching frequency at full load at minimum
rectied AC input voltage. The maximum switching frequency of
InnoSwitch3 in normal operation is 100 kHz, and the typical overload
detection frequency of is 110 kHz. In normal operating condition, the
switching frequency at full load should not be close to the overload
detection frequency.
The programmable switching frequency range is 25 to 95 kHz, but it
should be continued that the average frequency accounting for
primary inductance and peak current tolerances does not result in
average frequency higher than 110 kHz as this will trigger auto-
restart due to overload. Pushing frequency higher to reduce
transformer size is advisable, but Table 5 provides the suggested
frequency based on the size of the internal high-voltage MOSFET, and
represents the best compromise to balance overall device losses (i.e.
conduction and switching losses).
Reected Output Voltage, VOR (V)
This parameter is the secondary winding voltage during the diode /
Synchronous Rectier MOSFET (SR FET) conduction-time reected
back to the primary through the turns ratio of the transformer. Table
6 provides suggested values of VOR. VOR can be adjusted to achieve
a design that does not violate design rules for the transformer and
InnoSwitch3 Family Maximum Switching Frequency
INN3xx2C and
INN3xx3C 85 - 90 kHz
INN3xx4C and
INN3xx5C 80 kHz
INN3xx6C 75 kHz
INN3xx7C 70 kHz
INN3xx8C 65 kHz
SR FET while simultaneously achieving sufciently low Drain-Source
voltage of the primary side MOSFET. VOR can be adjusted as
necessary to ensure that no warnings in the spreadsheet are
triggered. For design optimization purposes, the following factors
should be considered,
• Higher VOR allows increased power delivery at VMIN, which
minimizes the value of the input capacitor and maximizes power
delivery from a given.

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• Higher VOR reduces the voltage stress on the output diodes and SR
FETs, which in some cases may allow a lower voltage rating for
higher efciency.
• Higher VOR increases leakage inductance which reduces power
supply efciency.
• Higher VOR increases peak and RMS current on the secondary-side
which may increase secondary side copper, diode and SR FET losses
thereby reducing efciency.
It should be noted that there are exceptions to this guidance
especially for very high output currents where the VOR should be
reduced to obtain highest efciency. Higher output voltages
(above 15 V) should employ a higher VOR to maintain acceptable
peak inverse voltage (PIV) across the output SR FET.
Optimal selection of the VOR value depends on the specic
application and is based on a compromise between the factors
mentioned above.
Mode of Operation, KP
KP is a measure of how discontinuous or continuous the mode of
switching is. KP > 1 is said to be in discontinuous operation (DCM),
while KP < 1 denotes continuous operation (CCM).
Ripple to Peak Current Ratio, KP
Below 1 (indicating continuous conduction mode), KP is the ratio of
ripple to peak primary current (Figure 5).
Table 6. Suggested Values for VOR.
Figure 5. Continuous Mode Current Waveform, KP≤1.
Output
Voltage
Suggested VOR
Value
Suggested
Range
5 V 55 V 45 V - 60 V
9 V 85 V 80 V - 90 V
12 V - 20 V 110 V 100 V - 120 V
KP≡ KRP =
(a) Continuous, KP<1
(b) Borderline Continuous/Discontinuous, KP = 1
IR
IP
IPIR
IP
IR
PI-2587-103114
Primary
Primary
KP≡ KDP =
T = 1/fS
T = 1/fS
(1-D) ×T
(1-D) ×T = t
t
D ×T
D ×T
(b) Borderline Discontinuous/Continuous, KP = 1
(a) Discontinuous, KP > 1
Primary
Secondary
Primary
Secondary
PI-2578-103114
(1-D) ×T
t
Figure 6. Discontinuous Mode Current Waveform, KP≥1.

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KK
I
I
PRP
P
R
/=
Above a value of 1, indicating discontinuous conduction mode, KPis
the ratio of primary MOSFET off time to the secondary SR_FET
conduction time.
KK t
DT
VV D
VD
1
1
PDP
MIN DS MAX
OR MAX
#
#
#
/=-
-
-
=
^
^
^
h
h
h
The value of KP should be in the range of 0.5 < KP < 6. Guidance is
given in the comments cell if the value of KPis outside this range.
Experience has shown that a KPvalue between 0.8 and 1 will result in
higher efciency by ensuring DCM or critical mode operation (CRM)
which is desirable for most charger designs.
The spreadsheet will calculate the values of peak primary current,
primary RMS current, primary ripple current, primary average current,
and the maximum duty cycle for the design based on the selection of
the these parameters.
Typical Primary Inductance, LPRIMARY_TYP (µH)
This is the typical transformer primary inductance target.
Primary Inductance Tolerance, LPRIMARY_TOL (%)
This parameter is the assumed primary inductance tolerance. A value
of 7% is used by default, however if specic information is provided
from the transformer vendor, then this may be entered in the grey
override cell. A value of 7% helps to reduce unit-to-unit variation and
is easy to meet for most magnetics vendors. A value of 3% will help
improve production tolerance further but will be more challenging to
vendors.
The other important electrical parameters are automatically calculated
by the spreadsheet. These can used to appropriatley select the other
components in the circuit, such as input fuse (FR) and EMI lter (LF),
bridge rectiers (BRD), output rectiers (SRFET) and capacitors (COUT),
as described in Figure 1.
PRIMARY CURRENT
IPEAK_PRIMARY − Peak primary current
IPEDESTAL_PRIMARY − Primary MOSFET current pedestal in CCM mode
IAVG_PRIMARY − Primary MOSFET average current
IRIPPLE_PRIMARY − Primary MOSFET ripple current
IRMS_PRIMARY − Primary MOSFET RMS current
SECONDARY CURRENT
IPEAK_SECONDARY − Peak secondary current
IPEDESTAL_SECONDARY − Secondary winding current pedestal
IRMS_SECONDARY − Secondary winding RMS current
Minimum Rectied Input Voltage, VMIN
Valley of the rectied minimum AC input voltage at full power is
calculated based on input capacitance (CAP_INPUT).

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Step 4 – Transformer Construction Parameters
Enter: CORE, AE, LE, AL, VE, BOBBIN, AW, BW, MARGIN
Choose Core and Bobbin based on maximum output power.
Core Type, CORE
By default, if the core type cell is left empty, the spreadsheet will
select the smallest commonly available core suitable for the
continuous (average) output power specied. Different core types
61
TRANSFORMER CONSTRUCTION
PARAMETERS
62
CORE SELECTION
63 CORE RM6 Info RM6
The transformer windings may not fit: pick a
bigger core or bobbin and refer to the Transformer
Parameters tab for fit calculations
64 CORE CODE PC95RM06Z Core code
65 AE 37.00 mm^2 Core cross sectional area
66 LE 29.20 mm Core magnetic path length
67 AL 2150 nH/turns^2 Ungapped core effective inductance
68 VE 1090.0 mm^3 Core volume
69 BOBBIN B-RM06-V Bobbin
70 AW 15.52 mm^2 Window area of the bobbin
71 BW 6.20 mm Bobbin width
72 MARGIN 0.0 mm
Safety margin width (Half the primary to
secondary creepage distance)
73
74 PRIMARY WINDING
75 NPRIMARY 77 Primary turns
76 BPEAK 3125 Gauss Peak flux density
77 BMAX 2844 Gauss Maximum flux density
78 BAC 933 Gauss AC flux density
79 ALG 140 nH/turns^2 Typical gapped core effective inductance
80 LG 0.310 mm Core gap length
81 LAYERS_PRIMARY
4
4 Number of primary layers
82 AWG_PRIMARY 30 AWG Primary winding wire AWG
83 OD_PRIMARY_INSULATED 0.303 mm
Primary winding wire outer diameter with
insulation
84 OD_PRIMARY_BARE 0.255 mm
Primary winding wire outer diameter without
insulation
85 CMA_PRIMARY 248 Cmil/A Primary winding wire CMA
86
87
SECONDARY WINDING
88 NSECONDARY 66 Secondary turns
89 AWG_SECONDARY 19 AWG Secondary winding wire AWG
90 OD_SECONDARY_INSULATED 1.217 mm
Secondary winding wire outer diameter with
insulation
91 OD_SECONDARY_BARE 0.912 mm
Secondary winding wire outer diameter without
insulation
92 CMA_SECONDARY 216 Cmil/A Secondary winding wire CMA
93
94
BIAS WINDING
95 NBIAS 15 Bias turns
Figure 7. Transformer Core and Construction Variables Section of InnoSwitch3 PIXLs Spreadsheet.
and sizes from the drop-down list are available to choose from if a
user-preferred core is not available, the grey override cells (AE, LE,
AL, VE, AW & BW) can be used to enter the core and bobbin
parameters directly from the manufacturer’s data sheet.