Current-programmed Converters Research Articles

A unified model for current-programmed converters

A unified model is established for a current-programmed power converter, which is both a modification and an extension of familiar models. Inclusion of the sampling effect allows the presence of an additional pole /spl omega//sub p/ in the current-loop gain to be derived. The resulting final double-slope asymptote is fixed in position, and the crossover frequency cannot exceed half the switching frequency. A stability parameter, Q/sub s/, determines the additional pole and describes the degree of peaking in the closed-loop transfer function. Experimental verification employs an analog signal injection technique. >

Physical origins of input filter oscillations in current programmed converters

Addition of an input filter to a current-programmed converter can cause the controller to oscillate. Two instability mechanisms can typically occur: (1) the current programmed controller effective current feedback loop may become unstable, or (2) the controller effective input voltage feedforward loop, which becomes a positive feedback loop when an input filter is added, may oscillate. Three design criteria for preventing oscillations are derived and interpreted. When all three criteria are well satisfied, then the output voltage regulation loop gain is unchanged. Hence, input filters of current programmed converters can be designed in essentially the same manner as for duty-ratio programmed converters. Results are summarized in tabular form for the basic buck, boost, and buck-boost converters. Experimental measurements for a buck converter with different input filters support the theoretical predictions.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Input filter design criteria for current-programmed regulators

The design of input filters for switched-mode regulators is discussed, and it is shown that the filter's effect on the power system depends on the control method used in the regulator's DC-DC converter. Design inequalities are reviewed for duty-ratio programmed converters, and specific expressions are presented for current-programmed converters. Examples of application to practical regulator circuits are given where current-programmed criteria, computer-driven measurement tools, and numerical evaluations of analytic expressions are used to design input filters.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>