Design Options

Use the Design Options form to view or change power supply specifications. The following options are available:

• Topology -  The Flyback topology is supported. This value cannot be changed.

• Optimization Type - If the device family allows you to choose an optimization type, click the calculator icon to select between cost or efficiency optimization.

• Family -  Changing the family option is not available for a created design. You need to create a new design if you want to select another family.

• Package -  You can change this option for a created design.

• Breakdown Voltage - Device drain to source breakdown voltage.

• Frequency - Depending on the device family you can choose the switching frequency value from the list.

• Current Limit -  For the TinySwitch device family, click the calculator icon to choose between Increased, Standard and Reduced in the drop down menu. Choose Increased for the device to deliver the most power, Reduced for reduced conduction losses in the switch, and Standard for a compromise between the reduced and increased current limit modes.

• M-pin function - This parameter is available for P/G packages of TopSwitch-HX and TopSwitch-GX families where M-pin exists. Select ILIM/PLIM Only or UV/OV Only to turn on current limiting and overvoltage programming.

• Feedback – When creating a new design, PI Expert selects a feedback type based on the specified PI Expert product family. For the devices with optional bias winding, you can turn the bias winding on by selecting the Use Bias check box. For the devices with required bias winding, the Use Bias check box is grayed out. Using a bias winding when it is optional typically reduces the amount of no-load power the design will consume.

• Feedback – PI Expert selects a feedback type based on the specified PI product family. Some feedback types require a bias winding.

Feedback Type

You can select the feedback type in the Feedback Type list. Use the Feedback Components form to view and edit the feedback components. The number of available feedback schemes depends on the PI Device family used. The most common feedback types are Secondary Zener or Secondary TL431. For low cost designs there is also Primary Resistor or Primary Zener feedback. If either Primary Resistor or Primary Zener is selected as the feedback type, the Feedback Components form is unavailable for the design.

Bias Winding feedback is only available for the LinkSwitch-XT product family. Bias winding feedback is very inexpensive and simple with regulation of about +/-10%. You cannot modify any bias parameters when Bias Winding feedback type is selected. See the Feedback Components form for more information.

Note: When the Feedback Type is either a secondary Zener or a TL431, PI Expert chooses an Ultra Fast diode as the diode type for the bias diode.

For LinkSwitch-CV family feedback type is set to Feedback Winding and using bias is optional. See Wizard - Design Options for more information.

Indirect CC  feedback consists of using the bias winding voltage to extract information about the output. Any variations of the output are sensed by the bias winding and the controller will make the necessary corrections based on this measurement.

Direct Secondary feedback can only be used in non-isolated designs, and basically it consists of converting the output current into a voltage by means of a sense resistor. The signal may or may not be filtered by a low pass filter, and is then connected to the feedback pin.

For InnoSwitch3 family feedback type is set to Secondary Divider.

The Fedback Type options available for InnoSwitch3-CP are summarized in the table below. To note is the fact that InnoSwitch3-Pro does not need an external feedback network as it is included in the secondary controller circuitry.

Bias Winding Requirements by Product

A bias winding is optional for some PI devices:

For the devices with optional bias winding, you can turn the bias winding on by selecting the Use Bias check box. For the devices with required bias winding, the Use Bias check box is grayed out. Using a bias winding when it is optional typically reduces the amount of no-load power the design will consume.