SolvabilityGraphs. To simplify the design problems, graphical solutions have been developed that, if passed, assure there is no stability problem or performance degradation. If failed, there may or may not be a problem and the more complex analytical expressions must be solved to determine stability and performance. The graphical solutions are dependent on the control mode of the converter.
Criteria. For duty-ratio-programmed control (voltage-mode control) converters, the graphical solution is called the Middlebrook criteria and is simple to construct. For current-programmed converters (current-mode control) one more criteria associated with the controller feedback loops must be added to ensure stability. Basic Papers. The basic design papers for input filter interaction with switching-mode power supplies are Middlebrook's paper for duty-ratio (voltage) programmed converters and the Jang and Erickson modification for current-programmed converters, which contains the information for both voltage-programmed and current-programmed converters on the same graphs. A useful paper on the methods of damping input filters is the Phelps and Tate paper. Shunt-Damped. One method of damping a single section LC filter is to place a dc-blocked damping resistor across the input-filter output capacitor. The analysis for this simple circuit is surprisingly complex and if this popular damping method is used, the Middlebrook paper, which also reviews his earlier work, is highly recommended. Timeline. The timeline of key papers can be used to locate other papers for this design problem. Do not use this information for design without independent verification of the information. Editor: Jerrold Foutz |
