| Abstract |
After a short introduction to the digital control of boost power factor correction converters, the principle
of operation of the alternating-edge-sampling algorithm is reviewed. The main features of this sampling
algorithm are: switching noise immunity, straightforwardness, the need for only few extra processor
cycles and accurate measurement of the averaged input current. However, to accomplish this last feature
the timing of the sampling instants has to be tuned manually. Moreover, the “ideal” timing instants may
slowly vary because of temperature effects and during the life-time of the converter. To annihilate these
effects and to avoid manual tuning, the alternating-edge-sampling algorithm is extended with an autotuning
feature for the timing of the sampling instants. The distortion caused by the sampling algorithm
due to an inaccurate timing of the sampling instants is quantified to obtain an estimate for the timing error.
This timing error is continuously monitored and intermittently used to adjust the timing of the sampling
instants. As a result, the proposed sampling algorithm provides accurate measurements of the averaged
inductor current without manual tuning, over a wide temperature range and during the operating life-time
of the converter. Experimental verification using a digitally controlled boost converter demonstrates the
feasibility of the proposed sampling algorithm and demonstrates that a small input current distortion can
be achieved. |
