The following information provides helpful tips on the installation and use of the PI Expert Power Supply Design Software.

1. General Setup
2. Installation
3. Frequently Asked Questions for PI Expert 6.5 Users
4. Power Supply Design
5. Optimization

• What's new in the PI Expert Suite v.6.6?
  
  
  • Added support for TinySwitch-PK through PI Expert to faciliate automated designs.
  • Added support for TOPSwitch-HX through PI XLs application
  • Added support for TinySwitch-PK and TOPSwitch-HX in PI Transformer Designer
  • Added Japanese language support

• What is contained on the PI Expert Suite v.6.6 CD-ROM?

The PI Expert Suite contains complete installation for PI Expert, PI Xls, PI Viewer and PI Transformer Designer applications. In addition to the PI Expert Suite software (available through web download), the CD-ROM also contains up-to-date Power Integrations product and design collateral.

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• How do I upgrade previous versions to PI Expert v.6.6?

The installation program will detect previous versions of PI Expert and ask you if you want to delete the previous version. You must select "YES" to uninstall all previous PI Expert versions to install PI Expert v.6.6.

• How do I get upgrades to PI Expert v.6.6 after I install it on my computer?

Make sure you are connected to the internet . Please use the auto update feature which can be found under Help - Check Latest Updates in the PI Expert, PI Xls, and PI Transformer Designer menus.

• I am having trouble properly installing PI Expert on my system. What should I do?

Verify that your system meets the minimum requirements: Windows 98/ME or NT/2000/XP, Pentium-II, 450 MHz processor, 60 MB free space, 128 MB system memory is required. 256 MB system memory is recommended.

You may need administrator privileges to install on your system. Please contact your system administrator for more details.

• The new version doesn’t have support for old products. What should I do?

 PI Expert supports devices recommended for new designs.  PI Expert designs created using legacy products can be viewed using the included PI Viewer application.  For PI Xls designs or for additional guidance please contact technical support at PIExpert@powerint.com

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• What is PI Transformer Designer?

PI Transformer Designer helps you to generate detailed transformers for your PI Expert and PI Xls designs. It works as an add-on application to PI Expert v.6.6 and PI Xls v.6.6 and processes data from pre-existing PI Expert and PI Xls design files.

To use PI Transformer Designer you need to first create a design either in PI Expert or PI Xls. Save and close this design and then reopen the same design from PI Transformer Designer. The software will automatically generate a complete transformer design based on the inputs from either PI Expert or PI Xls programs. The user then can either accept this transformer design or change the design to suit his needs.

PI Transformer Designer provides options to select shield windings for better EMI performance.

• What is new in PI Transformer Designer v.6.6?

In v.6.6, support for TinySwitch-PK and TOPSwitch-HX has been added.

• What is PI Viewer?

This application allows you to conveniently view *.UDS, *.UDX or *.UDF design files created with current and previous versions of  PI Expert. *UDX, *.UDF files are not compatible with PI Expert version v.6.6.

The PI Viewer allows the user to print or export design files into HTML format

• What is PI Xls?

PI Xls was included to assist engineers already familiar with Power Integrations earlier excel transformer design spreadsheets.  This tool provides early support for new products and topologies in a familiar spreadsheet format.

• Is the design file format different in PI Expert v.6.6?

No, PI Expert v.6.6 has the same file format as version 6.5. PI Expert v.6.6 uses the *.UDS file format. The *UDX and *.UDF formats were used with previous versions, prior to 5.0 and 6.1, and must be converted to work with PI Expert v.6.6. This conversion may slightly modify the original *.UDX, *.UDF file results. The PI Viewer is available to review the original content of *.UDX, *.UDF files.

• Can I open the *.UDX, *.UDF design files created using previous versions of PI Expert v.6.6?

The user has two choices when opening an old (*.UDX, *.UDF) design file:

• Review the file in read-only format with the PI Viewer. PI Viewer is also available within the PI Expert Tools menu.
• Open the file and select the "Yes" option at the startup prompt to automatically convert to PI Expert v.6.6 *.UDS format. This file is no longer read-only and may be modified and re-saved. This conversion may modify the original *.UDX, *.UDF file contents.

See "Opening a *.UDX, *.UDF file" for more information.

• I changed the Preferences settings (Main Menu Tools option), but my active design has not changed. What have I done wrong?

The Preferences setting changes you have made will only take effect on your New designs and does not affect your active design. To alter the active design, you can select the Optimizations Parameters or access the "Advanced" tabs within the PI Component and Transformer Selection forms.

• How do I save my custom power supply input specifications and custom transformer settings?

Use the "Save Custom Settings" option in the Active Design menu to save your custom power supply input specifications and custom transformer settings.

• Where can I specify custom transformers?

In PI Expert v.6.6 Component database library has been added for transformer core (and capacitors and diodes). Users can enter any number of custom cores in this component library for the software to use. This library can be accessed under the Tools menu, by clicking the Custom Library tab. Users can share individual libraries or all libraries by using the import or export buttons provided.

• What is the difference between setting up the Preferences and saving the Custom settings?

Saving Preferences works only on your new designs and does not affect active designs. When initiating a new design the Saved Custom settings will be automatically entered into all applicable forms.

• I have a question that is not answered here. How do I contact PI Expert technical support?

For more information on using PI Expert v.6.6 please visit our web site at: www.powerint.com/designsoftware.htm or send us an e-mail, piexpert@powerint.com, describing the problem (if possible, please attach your design *.UDF, *.UDX or *.UDS design file).

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• Does PI Expert support all Power Integrations device families?

The following device families are supported by PI Expert v.6.6:

• DPA-Switch (DPA423-426 for DC-DC applications in Forward topology from 0 W to 100 W)
• LinkSwitch-XT (LNK362-364 for AC-DC applications from 0 W to 9 W)
• TinySwitch-II (TNY263-268 for AC-DC applications from 0 W to 23 W)
• TinySwitch-III (TNY274-280 for AC-DC applications from 0 W to 36 W)
• PeakSwitch (PKS603-606 for AC-DC applications from 0 W to 117 W)
• TOPSwitch-GX (TOP242-250 for AC-DC applications in Flyback topology from 0 W to 250 W)
• TinySwitch-PK (TNY375-380 for AC-DC applications from 0 W to 45 W)
• TOPSwitch-HX (TOP254-258 for AC-DC applications from 0 W to 150 W)
  

Please see the 'Introduction' page within the PI Expert Help utilities for access to the 'Power Integrations' Product Selector Guide'. This will help you choose the right device family for your particular application. In addition the PI Xls utility also supports the following devices families and topologies:

• DPA-Switch Flyback
• DPA-Switch Forward
• LinkSwitch Flyback
• LinkSwitch (LNK52X) Flyback
• LinkSwitch-HF
• LinkSwitch-LP
• LinkSwitch-TN Buck
• LinkSwitch-TN Buck-Boost
• LinkSwitch-XT
• PeakSwitch Flyback
• TinySwitch-II Flyback
• TinySwitch-III Flyback
• TOPSwitch-GX Flyback
• TinySwitch-PK Flyback
• TOPSwitch-HX Flyback

Can I change the parameters from PI Transformer Designer?

Yes. The user can change almost all the parameters on the results form either through PI Transformer Designer or through the parent file (PI Expert or PI Xls). For example parameters like number of turns, margin and core can only be changed through the parent design file (PI Expert or PI Xls) Other parameters like winding materials, wire gauges, foil thickness etc can be changed directly in PI Transformer Designer.

Winding instructions cannot be directly altered but the information regarding materials used, wire gauge information start and termination pins can all be altered through the proper forms. For example if the primary winding start and termination pins need to be changed then they can be updated on the primary winding form. These changes will be accurately reflected in the winding instructions.

• Why does PI Transformer Designer use multiple parallel wires in transformer constructions?

PI Transformer Designer uses multifilar windings. This means that rather than use one thick wire it uses two or three (or more) parallel stands of thinner wire. This minimizes skin effect losses, fills the bobbin width, lowers leakage inductance, and thus provides a more optimized design.

• In PI Transformer Designer, what is “maximum terminations per pin”?

PI Transformer Designer uses multifilar windings. This means that rather than use one thick wire it uses two or three (or more) parallel stands of thinner wire. As more and more parallel wires are used, it becomes difficult to terminate all these wires onto a single pin especially if the wires are thick and the pin is thin as is the case with small bobbins. In this case it is better to split the wires and between 2 or 3 different pins for the terminations. The “maximum terminations per pin” specifies how many wires can be terminated onto a single pin and the default is set to 4 wires per pin. For thinner wires this number may be as high as 6 and for thicker wires this number may be as low as 2.

• The terminology used within PI Expert is unfamiliar to me. Where are the definitions for these terms?

There is a Help button located on the toolbar and pop-up window within PI Expert or you can press F1 function key at any time. Selecting the Help button will launch the Help Utilities consistent with that form or window. You will find answers to common questions, terminology and guidelines to software usage within the individual Help sections.

For further details on general power supply terminology we recommend that the user read the applicable Application Notes for the selected devices. (See Help for details).

• What is the basis for the algorithms used within PI Expert?

For details of the calculations, see the applicable design methodology documents. The PI Expert algorithms are consistent with these references. Also see the Help system for detail on 'TinySwitch-II Design Calculations'.

• How can I specify a design with a negative DC output?

PI Expert allows one negative output when the total number of output is 2 or more (the negative output cannot be the main output). To work around a design where a single negative output is required simply enter the negative DC output as a positive value. Make sure you remember which output is negative when you determine the transformer pin-out and resulting PCB layout.

• What determines Transformer maximum power capability (PMAX)?

Transformer power capability is determined using the Area-Cross-Product method (Ae x Aw). Efficiency, device switching frequency and transformer margin are factored into this calculation.

• My preferred Transformer does not appear on your list. How can I add it?

In PI Expert v.6.6 Component database library has been added for transformer core (and capacitors and diodes). Users can enter any number of custom cores in this component library for the software to use. This library can be accessed under the the Tools menu, by clicking the Custom Library tab.

• I am using non-margin transformer but, due to bobbin spacing, I still require a margin to meet Safety requirements. How can I accomplish this?

By default, non-margin transformers (triple insulated) assume no margin (M=0 mm). To override this setting, simply enter the required margin on the Advanced Transformer Selection form. This change will affect all displayed transformers.

• In PI Transformer Designer what is “Margin on Left” and “Margin on right”?

PI Transformer Designer provides more flexibility in specifying the margin on which side of the bobbin (left and right side for horizontal bobbin and top and bottom side for vertical bobbin). This is particularly useful in specifying non-symmetrical margins.

The ‘margin on left’ and ‘margin on right’ should add up to two times the margin specified in PI Expert and PI Xls, which assume symmetrical margins. Thus is margin M is specified as 3 mm in PI Expert then the total margin (margin on left plus margin on right) should equal to 6 mm. The distribution of margin can be in any proportion so long as the total margin equals 6 mm.

• I noticed some inconsistencies with the gapped core effective inductance calculation (ALG). Is this a bug?

PI Expert uses non-integer primary turns within the ALG calculation. In most cases, since primary turns are large, the resulting error is minimal. Please make the necessary changes to the ALG value when communicating with your magnetic vendor.

• What is the basis for the default efficiency estimates?

Default efficiency is based on the efficiency curves presented in AN-21 (TOPSwitch-II), AN-26 (TOPSwitch-FX) and AN-29 (TOPSwitch-GX). TinySwitch-II efficiency is estimated and based on the evaluation of actual power supplies.

These curves estimate power supply efficiency given AC input range and output voltage. For output voltage between 5 V and 12 V, efficiency is estimated using linear interpolation. PI Expert estimates efficiency deviation for outputs outside the 5 V to 12 V range.

• Can PI Expert help me with package choice and thermal evaluation?

PI Expert can be used in conjunction with AN-21, AN-26 and AN-29 to gain insight into package dissipation. In general, Y-packages with suitable heatsinking should be considered when device dissipation exceeds approximately 1.5 W (open frame) or 1 W (adapter/enclosure); assuming a 50 °C ambient temperature.

Thermal design can be further hindered by extreme operating temperatures, poor layout, high altitude, inefficient transformer design and/or airflow limitations. When used near maximum current capability, Power Integrations recommends a maximum operating junction (die) temperature of 110 °C for all TOPSwitch, TinySwitch, LinkSwitch and PeakSwitch products.

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• Optimization is not solving with the input Capacitor, TOPSwitch/TinySwitch-II and/or Transformer that I wish to use. How can I work around this problem?

If the output power is beyond the capability of the device in question, the Optimization tool will choose the device combination which best suits your requirements. This choice is dependent on Optimization Parameters section within the Active Design on the main menu. If Optimization chooses a device, which is smaller than the preferred device, the user may force the preferred component choice(s). Simply enable the "Optimization Manual Start Point" option. Reopen Current Design and within the appropriate form, select the preferred PI Deviceand/or Transformer. When Optimize is selected, PI Expert will consider the chosen devices before proceeding to the next component on the respective list(s).

If rated greater than or equal to the power required, the Custom Transformer selection may be considered during the Optimization process.

Transformer power ratings are derived using the area-cross-product method (Ae x Aw). Power supply efficiency and switching frequency are factored into this calculation.

In all cases, Optimization will choose the optimum input capacitor. The user cannot override this component choice. The user should pursue manual design if an alternate input capacitor is desired.

• Why do I get the same efficiency estimate for Cost and Efficiency Optimization?

PI Expert assumes a current waveform parameter consistent with AN-21, AN-26 and AN-29 (varies according to power requirements, AC line voltage and PI Deviceused). Therefore the efficiency estimate does not take account of the change of optimization goal. In practice a prototype using a transformer design optimized for efficiency should have a higher efficiency than that optimized for cost.

• Optimization is providing a result with an unusually large Zener clamp loss (PZ). Why?

The Zener Clamp loss is calculated assuming a leakage inductance (some percent of the primary inductance) and at the peak primary current. In low power applications, these two factors play a large part in determining the overall zener clamp loss. In reality, the clamp loss can be a little lower that what is calculated by the software.

It is recommended that the designer verify transformer and layout parasitic prior to finalizing his transformer design. This includes transformer leakage inductance (LL) and secondary trace inductance (LSEC). This may be especially true for multiple output power supplies, where the leakage is dependent on the characteristics of all outputs.

• How can I guarantee a Continuous / Discontinuous design using the Optimization engine(s)?

Optimization will choose the optimum operating point for the given requirements. In general, the user has no control over Continuous / Discontinuous operating modes.

The user may increase the chances of discontinuous operation by enabling "Optimization Manual Start Point" and over-sizing the initial PI Deviceselection.

• How does Optimization work?

Optimization generates multiple design solutions and compares to an expert design rules database, compiled by the Power Integrations engineering staff. The Optimization engine seeks the minimum design solution that meets, or exceeds, the limits specified in this database.

Power Integrations recommends that all design solutions be constructed and performance verified to your specific requirements. This includes independent verification of safety, thermal and system reliability.

• What is an Optimization Best-Fit solution and how can I use it?

Optimization Best-Fit solutions occur infrequently, but are provided when the Optimization engine has failed to pass all design checks. In this case, the user is provided the option to review the solution closest to the optimum design (based on a internal score).

Optimization failures can occur for a number of reasons, including: extremely high or low output voltages, low AC input voltage, initial PI Deviceand/or Transformer are too large (when using 'Optimization Manual Start Point'). In these cases, it is best to review the Best-Fit design for possible errors (too many L, CMA too low, BP above limits, etc.). It may be possible to further optimize the design manually.

• What control do I have over the Optimization results?

If you are seeking additional design solutions, it is recommended that the user consider all Optimization types (Cost, Efficiency). The TOPSwitch-FX/GX device families allow additional Optimization options (Efficiency with ILIM Reduction). By utilizing "Optimization Manual Start Point", the user can review solutions with oversized PI Device and/or Transformer combinations.

The control over optimization results for DPA-Switch is limited. You can change the DPA-Switch, the transformer or the output diode independently of the other.

• Cost Optimization provides a result, which generates the warning "Core size may be too small for this power level (Po)". Is this a serious problem?

This message may appear following successful Cost Optimization. Cost Optimization will consider transformers with power ratings (PMAX) within 90% of specified output power. This warning states that the design, running under continuous rated power, is a approaching the maximum capacity for that core/bobbin size. In these cases, further evaluation of power supply thermal performance is recommended.

The user may want to consider a solution with a larger core. To generate these results, you must enable Optimization Manual Start Point. Select a larger transformer and reselect Cost Optimization

• Why does optimization using Forward topology (DPA-Switch) take longer time than Flyback designs?

Optimization using the Forward topology often takes longer time than a Flyback design. This is because the optimization algorithm for DPA-Switch is far more complex. The algorithm steps through several possible solutions corresponding to different combinations DPA-Switch, transformer and output rectifier while iterating the transformer turns’ ratio. It then assigns scores for each solution based on efficiency of the design, cost and size of components. The design with the highest score representing the most optimum design is presented.

• Can I change the transformer in a DPA-Switch design?

Yes. You can change the DPA-Switch, the transformer or the output rectifier. To do this, click on the component you want to change and go to the appropriate form. In this case click on the transformer on the block schematic to go to transformer selection form. Then choose the transformer from the transformer list and click OK.  A message box will appear informing the user that this selection may change his previously obtained results. Click "OK" and the software will return an optimized design with user selection for transformer. Instead of the transformer, either the DPA-Switch or the forward diode can also be changed in a similar manner but may change the transformer selected previously.

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