A system comprising: a load subsystem to draw output current; and an active-power filter to provide the output current to the load subsystem by regulating the output voltage for the load subsystem, wherein the active-power filter comprises: a control loop for regulating an output voltage; a control loop for regulating a DC input current using current-mode control; and control circuitry to implement the control loops by combining an output-voltage sense signal with an input-voltage sense signal to generate a control signal; and switching-signal generation circuitry to further implement the control loops by providing a switching signal based on the control signal and a current-sense signal, wherein the current-sense signal indicates the amount of current drawn through a switching element of a power converter, and the switching element is responsive to the switching signal, wherein the control circuitry includes an error amplifier and associated circuitry to integrate the output-voltage sense signal, and characterised in that the output current is drawn by the load subsystem with a current ripple having a nominal ripple frequency, and wherein the error amplifier and associated circuitry are selected to provide a control loop bandwidth in the range of 1/10th to 1/30th of the nominal ripple frequency. a load subsystem to draw output current; and an active-power filter to provide the output current to the load subsystem by regulating the output voltage for the load subsystem, wherein the active-power filter comprises: a control loop for regulating an output voltage; a control loop for regulating a DC input current using current-mode control; and control circuitry to implement the control loops by combining an output-voltage sense signal with an input-voltage sense signal to generate a control signal; and switching-signal generation circuitry to further implement the control loops by providing a switching signal based on the control signal and a current-sense signal, wherein the current-sense signal indicates the amount of current drawn through a switching element of a power converter, and the switching element is responsive to the switching signal, wherein the control circuitry includes an error amplifier and associated circuitry to integrate the output-voltage sense signal, and characterised in that the output current is drawn by the load subsystem with a current ripple having a nominal ripple frequency, and wherein the error amplifier and associated circuitry are selected to provide a control loop bandwidth in the range of 1/10th to 1/30th of the nominal ripple frequency. a control loop for regulating an output voltage; a control loop for regulating a DC input current using current-mode control; and control circuitry to implement the control loops by combining an output-voltage sense signal with an input-voltage sense signal to generate a control signal; and switching-signal generation circuitry to further implement the control loops by providing a switching signal based on the control signal and a current-sense signal, wherein the current-sense signal indicates the amount of current drawn through a switching element of a power converter, and the switching element is responsive to the switching signal, wherein the control circuitry includes an error amplifier and associated circuitry to integrate the output-voltage sense signal, and characterised in that the output current is drawn by the load subsystem with a current ripple having a nominal ripple frequency, and wherein the error amplifier and associated circuitry are selected to provide a control loop bandwidth in the range of 1/10th to 1/30th of the nominal ripple frequency.