Control Loop Components Chart

When the design is based on a PWM control device, like TOPSwitch-HX or the DPA-Switch product family, you can click the Chart button to display the estimated Bode plots for the design. The following plots are generated for both the gain (Magnitude) and the phase (Phase) of the design:  

• The power stage: the Power Switch, the transformer, the output diodes and the output capacitors.

• The control stage, which consists of the PI device controller, the TL-431 and its support components.

• The power and control stages together (the magnitude and phase responses of the entire supply).

Changing the values of the control loop components including the gain of the error amplifier and the optocoupler current transfer ratio (CTR) affects the Bode plots.

You may also plot the  control loop response over line voltage by moving the chart to show the Feedback Components dialog and then entering “Vin”. The bode plot will then be plotted based upon this input voltage. Be sure to unfreeze the Vin before you close the chart.

The Control Loop Components Chart dialog box has the following control buttons:

• - saves the chart as .bmp file.

• - prints the entire chart.

• - shows or hides the chart legend.

• - - opens the Graph Options dialog box. In the Series, Common and Colors tabs of the Graph Options dialog box you will find the parameters for customizing the chart. The Series tab allows you to hide/show graphs and specify their color and line style. The Common tab lets you to edit the value range for X and Y axes and the chart title. The Colors tab allows you to adjust the colors and styles for the chart components.

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