A system includes a constant input current filter configured to draw a constant input current from a power source and to generate a variable output current. The constant input current filter includes a capacitor, a boost converter, and a buck converter. The boost converter is configured to receive at least a portion of the input current and to charge the capacitor using at least the portion of the input current during first time periods associated with operation of a load. The buck converter is configured to discharge the capacitor and to provide an additional current as part of the output current during second time periods associated with operation of the load. The load could represent an electronic device having a time-varying output power characteristic, such as a wireless radio.