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ADP1046A 100Watt
Evaluation board
DIGITAL FILTER SETTINGS AND TRANSIENT ANALYSIS
The digital filter can be changed using the software by manipulating the position of the poles and zeros (red and green circles
in the figures below) in the Laplace domain. The ADP1046A allows three different sets of compensation to be programmed,
one at light load, one at heavy load, and one for soft-start.
A type 3 compensation is implemented in the ADP1046A. The first pole (to eliminate steady state error) is indirectly accessed
through the placement of the first zero. The second pole can be freely placed (ideally at the ESR zero), but the third pole (high
frequency gain) is fixed at half the switching frequency. There is an additional constraint in moving the poles and zeros and it is
that the software allows the poles and zeros to be moved only in a manner that keeps the slopes between them equal to be
±20dB/dec.
WARNING:
While varying the compensation parameters is possible while the part is running, the wrong combination
of parameters can cause the system to become unstable.
The following figures are provided to demonstrate the performance of the PSU as well as the ease with which the GUI can be
used to change the dynamic response of the system.
A.
Closed Loop System: Figure 41 and Figure 42 show the bode plot of the system.
The validity of this plot depends highly on the proper characterization of the output inductor and capacitor and their
respective parasitic components namely the DC resistance and ESR. The GUI displays the closed loop crossover
frequency, phase margin as well as individual gain and phase plots for the LC filter, digital filter and the closed loop
scenarios.
Rev. 1.3 | Page 27 of 55
PRD1386
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