A digital controller comprising: a sampling component configured to sample an output signal from a system and an input signal from the system at a first sampling rate, said first sampling rate being at least equal to a predetermined operating rate; an input parameter obtaining component configured to receive the output signal and the input signal sampled at the first sampling rate and to obtain values for a plurality of input parameters, said values for said plurality of input parameters being sampled at said first sampling rate; a decimator component configured to receive said values for said plurality of input parameters sampled at the first sampling rate and to provide subsampled values for said plurality of input parameters, said subsampled values being sampled at a second sampling rate that is slower than said first sampling rate; an adaptive plant estimator component configured to receive said subsampled values of said plurality of input parameters and to obtain a model of the system based on said subsampled values; said model reflecting variations in the system; a compensator design component configured to receive the model of the system and to provide compensator parameters based on said model; wherein said compensator parameters reflect changes in the system; values of said compensator parameters being sampled at the second sampling rate; and a feedback compensator configured to receive said values of said compensator parameters and to adjust said input signal to said system based on said compensator parameters; and further comprising: a load current estimating component configured to receive the output signal sampled at the first sampling rate and state estimation data from said adaptive plant estimator component and to provide estimated load current data at the first sampling rate; and another decimator component configured to receive the estimated load current data at the first sampling rate and to provide the estimated load current data at a predetermined operating rate of the system to said feedback compensator; wherein the load current estimating component comprises a state estimator comprising: a disturbance estimating component configured to provide an estimated disturbance from a difference between a sensed output and an estimated output; and a power supply model component configured to receive the estimated disturbance as an input; wherein said power supply model component also receives as input a duty cycle multiplied by a predetermined gain; wherein said estimated disturbance is an estimated load current; wherein said disturbance estimating component comprises a proportional integral component; and wherein said power supply model provides an estimated state and said estimated output; wherein said difference between said sensed output and said estimated output is obtained from an oversampling modulator; said difference being an oversampled difference; said oversampled difference being provided to said disturbance estimating component; an output of said disturbance estimating component being an oversampled estimated disturbance; and the state estimator comprises: a low pass filter for receiving said oversampled estimated disturbance and for providing said estimated disturbance. a sampling component configured to sample an output signal from a system and an input signal from the system at a first sampling rate, said first sampling rate being at least equal to a predetermined operating rate; an input parameter obtaining component configured to receive the output signal and the input signal sampled at the first sampling rate and to obtain values for a plurality of input parameters, said values for said plurality of input parameters being sampled at said first sampling rate; a decimator component configured to receive said values for said plurality of input parameters sampled at the first sampling rate and to provide subsampled values for said plurality of input parameters, said subsampled values being sampled at a second sampling rate that is slower than said first sampling rate; an adaptive plant estimator component configured to receive said subsampled values of said plurality of input parameters and to obtain a model of the system based on said subsampled values; said model reflecting variations in the system; a compensator design component configured to receive the model of the system and to provide compensator parameters based on said model; wherein said compensator parameters reflect changes in the system; values of said compensator parameters being sampled at the second sampling rate; and a disturbance estimating component configured to provide an estimated disturbance from a difference between a sensed output and an estimated output; and a power supply model component configured to receive the estimated disturbance as an input; wherein said power supply model component also receives as input a duty cycle multiplied by a predetermined gain; wherein said estimated disturbance is an estimated load current; wherein said disturbance estimating component comprises a proportional integral component; and wherein said power supply model provides an estimated state and said estimated output; wherein said difference between said sensed output and said estimated output is obtained from an oversampling modulator; said difference being an oversampled difference; said oversampled difference being provided to said disturbance estimating component; an output of said disturbance estimating component being an oversampled estimated disturbance; and