Jeff Falin
Texas Instruments

A mathematical model is always helpful in determining the optimal compensation components for a particular design. However, compensating the loop of a WLED current regulating boost converter is a bit different than compensating the same converter configured to regulate voltage. Measuring the control loop with traditional methods is cumbersome because of low impedance at the feedback (FB) pin and the lack of a top-side FB resistor. In Reference 1, Ray Ridley has presented a simplified, small-signal control-loop model for a boost converter with current-mode control. The following explains how to modify Ridley's model so that it fits a WLED current-regulating boost converter; it also explains how to measure the boost converter's control loop.