Predictive energy balance control for PDN applications

March 09, 2015 //By Steve Sandler
Predictive energy balance control for PDN applications
Steve Sandler of Picotest considers predictive energy balance control for PDN applications.

Power integrity (PI) and power distribution network (PDN) design are now central elements in the design of all high-speed, high-performance, and low-noise electronic circuits. 

The first rule in achieving optimum performance is to maintain the power distribution path impedance magnitude below some specific level, often referred to as the target impedance. 

The second rule is to keep the power distribution impedance as flat as possible over frequency.  Semiconductor companies are introducing new voltage regulator architectures incorporating non-linear controls, multiple loops, and hysteretic operation to achieve these goals.  One of the more interesting topologies is the patented predictive energy balance (PEB) controller, developed and owned by Cognipower.

What is PEB?
The PEB control algorithm controls the voltage converter performance from a supply vs. demand perspective.  As in most switching converters, energy is stored in an inductor and transferred to the output where the voltage is averaged in a capacitor.  The energy stored in the inductor is:

The PEB controller establishes the required supply based on the demand, setting these equations equal during each switching cycle.  The result is a “memory-less” control, with every cycle being a “clean slate” resulting in complete dynamic response recovery within a single switch cycle.  The output neither overshoots nor undershoots. The controller is inherently stable, since there are no compensating poles added in the control function.  The PEB control computational block diagram is shown in Figure 1.

Figure 1  Block diagram of the PEB computational control. Note that the voltage terms and the current terms are squared in order to provide energy comparisons rather than voltage or current comparisons.

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