A design criteria for the current gain in current-programmed regulators

The design of the inner loop for current-programmed regulators is discussed in this paper. The effect that current gain has on the quality factor Q of the LC filter is shown. A methodology is derived to reduce this value that, in most cases, can be very high. A high quality factor can produce drastic changes with undesirable effects on regulator stability. A low quality factor will produce two real poles with a consequent reduction in the current response. After the proper selection of the current gain is done, the design procedure for the proportional integral controller of the outer loop can be continued. The design-oriented analysis is applicable to the three basic switch-mode pulsewidth modulation converters, i.e. buck, boost and buck-boost. At the end, the procedure is applied to a 280 W boost regulator that shows the simplicity of this approach