A bridgeless constant current power factor correction circuit, comprising: an input capacitor configured to receive an input current from a constant current source and produce an input voltage; a first switching device coupled to the input capacitor and the current source, wherein the first switching device is configured to be operable during a first half cycle of the input current and shorted during a second half cycle of the input current, and wherein when operable, the first switching device switches between an ON state and an OFF state; a second switching device coupled to the input capacitor and the current source, wherein the second switching device is configured to be operable during the second half cycle of the input current and shorted during the first half cycle of the input current, and wherein when operable, the second switching device switches between the ON state and the OFF state; a controller coupled to the first switching device and the second switching device, wherein the controller is configured to provide a pulse width modulation signal to the first switching device and the second switching device to control the first switching device and the second switching device, wherein the controller is configured to switch the first or second switching device (210a;210b) between the ON state and the OFF state, depending on which half cycle the input current is in, wherein when one of the first or second switching devices (210a; 210b) is in the OFF state, the input capacitor charges and the input voltage rises, and when one of the first or second switching devices (210a; 210b) is in the ON state, the input capacitor drains and the input voltage drops; and a DC output bus configured to be providing an output voltage, wherein the controller comprises a feedback controller that is configured to compare the output voltage and a reference voltage and that is configured to generate a feedback controller output that increases when the output voltage is below the reference voltage and that decreases when the output voltage is above the reference voltage, wherein the controller is configured to generate the PWM signal at least based on the feedback controller output, wherein the output voltage is a conditioned form of the input voltage, wherein the input voltage is in phase with the input current. an input capacitor configured to receive an input current from a constant current source and produce an input voltage; a first switching device coupled to the input capacitor and the current source, wherein the first switching device is configured to be operable during a first half cycle of the input current and shorted during a second half cycle of the input current, and wherein when operable, the first switching device switches between an ON state and an OFF state; a second switching device coupled to the input capacitor and the current source, wherein the second switching device is configured to be operable during the second half cycle of the input current and shorted during the first half cycle of the input current, and wherein when operable, the second switching device switches between the ON state and the OFF state; a controller coupled to the first switching device and the second switching device, wherein the controller is configured to provide a pulse width modulation signal to the first switching device and the second switching device to control the first switching device and the second switching device, wherein the controller is configured to switch the first or second switching device (210a;210b) between the ON state and the OFF state, depending on which half cycle the input current is in, wherein when one of the first or second switching devices (210a; 210b) is in the OFF state, the input capacitor charges and the input voltage rises, and when one of the first or second switching devices (210a; 210b) is in the ON state, the input capacitor drains and the input voltage drops; and a DC output bus configured to be providing an output voltage, wherein the controller comprises a feedback controller that is configured to compare the output voltage and a reference voltage and that is configured to generate a feedback controller output that increases when the output voltage is below the reference voltage and that decreases when the output voltage is above the reference voltage, wherein the controller is configured to generate the PWM signal at least based on the feedback controller output, wherein the output voltage is a conditioned form of the input voltage, wherein the input voltage is in phase with the input current.