8         Loop Analysis

8.1            What is Loop analysis?

Loop analysis is a tool to let user arbitrary draw a transfer function by vary the coefficient or component from the feedback block. On the other way, curve fitting can be done by entering points of expected gain or expected phase, by pressing “Automatic Compensation” button, the coefficient of the transfer function or components will be changed to fit those points.

 

8.2            Loop Analysis with power supply initialized - Generic transfer function analyzer

The Loop Analysis provides the interface to customize the transfer function and shows the gain and phase of the transfer function G(s)

 

 

8.2.1                  Change transfer function coefficients (a_i and b_i)

Input a_i and b_i with using this interface. You can set the number of parameters by setting n., where n is the order of the transfer function.

 

8.2.2                  Define the range of each coefficient for Automatic Compensation

The range of a_i and b_i should be specified for curve fitting purpose. For coefficient which user may not want to be changed by our non-linear regression curve fitting engine, user simply unchecks the check box as shown above.

 

8.2.3                  Draw any transfer function

Click on "Compensation Setting". You can set the expected Gain and Phase at different frequencies. Then, close this window and click on "Automatic Compensation"

 

8.2.4                  Change after Automatic Compensation

After Automatic Compensation, a non-linear regression curve fitting will change a_i and b_i value so as to fit the expected gain and expect phase as close as possible. The adjusted a_i and b_i are shown at the parameter setting interface.

 

8.2.5                  Tips on Automatic Compensation

How well the transfer function fit all those points depends on the number of a_i and b_i allowed to change and the range of a_i or b_i

 

8.2.6                  Non-linear Load Transient Analysis

Non-linear load transient analysis can be done by pressing “Transient Analysis.” The voltage waveform will be displayed according to the loading current shape and output impedance defined by user.

 

8.2.7                  How to set the Step loading in Transient Analyzer?

 In Transient Analysis

1. Click the step loading current with this interface, enter the turning point of the loading current I_i against t_i .
2. Press on “Apply" to make it effective.
3. The arbitrary current loading current will be repeated at a rate defined by “Frequency” at the upper right corner.

 

8.2.8                  How to set the Sine loading in Transient Analyzer?

 

1. Check the “sine loading” selection and set the upper and lower limit of sine loading.
2. Press on “Apply" to make it effective.
3. “Maximum” means the peak current of the sine wave loading
4. “Minimum” means the lowest current of the sine wave loading.

 

8.2.9                  What does the curve tell?

Once apply is clicked. AC voltage change and the response also can be seen on the setting at "Advance User Setting"

 

8.2.10              Advance User Setting in Transient Analyzer

After Click on "Advance User Setting" at Loading Setting, You can set the output impedance of a generic power supply by setting “Output Capacitor”, “Output Inductor”, “Loading Capacitor”, “Max. positive supply current” and “Min. negative supply current” to customize the generic power supply characteristic.

 

 

8.3            Loop Analysis with power supply initialized

 

After initializing a power supply design, the loop analyzer will take the open loop transfer function of the power supply user chosen.  Current injection method is employed for small signal analysis, all the detail parasitic element, e.g. ESR, ESL, ESR vs Temp. and high frequency effect, are already considered. User no longer needs to do the tedious analysis.

 

8.3.1                  Automatic Compensation - optimizing gain and phase margin 

User can set the Expected Gain Margin, Expected Phase Margin and Expected Cut-off Frequency of the power supply and press “Automatic Compensation” for the machine to find proper component to fit those points.

Or user can go into the “Compensation Setting,” click the check box “Use Advanced Setting” and enter point by point of the expected gain and expected phase. Go back and click on the "Automatic Compensation" our machine will try to provide the corresponding feedback component which will best fit user defined points.

 

8.3.2                  How can feedback components be changed?

For example, if you choose the Generic Feedback circuit, the parts in the circuit are modeled as values such as capacitance or resistance. You can change particular values from the generic component page.

Click on the component button and then you can see the following page. Uncheck the checkbox if you don’t want the component used for automatic compensation.

 

Not every component are allowed for automatic compensation, only the component with a check box “Enable for Automatic Loop Compensation” at the upper right corner of component selection user interface.

8.3.3                  Define the range of each component for Automatic Compensation

 

The range of the component used for automatic loop compensation is all component listed in the searched components box which is defined by the searching criteria.

 

8.3.4                  What bases do the transient analysis work?

The transient analysis is based on the small signal close loop transfer function to derive equivalent output impedance. Non-linear effect caused by the limitation of sink and source current have also considered.

 

8.3.5                  Corresponding transient response

You can select the output that you would like to monitor the transient response.

 

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