A power converter comprising: a buck converter portion comprises a first diode, a first inductor, and a capacitor, said buck converter portion being arranged such that a first terminal of the first inductor is connected to a cathode of the first diode at an input node, a second terminal of the first inductor is connected to a first terminal of the capacitor at an output node, and an anode of the first diode is connected to a second terminal of the capacitor at a first ground node, wherein the input node is connected to an input voltage via a first switch, and wherein the buck converter portion is arranged to supply an output voltage at the second terminal of the inductor; an energy storage portion comprising a second diode, an energy storage element, and a second inductor magnetically coupled to the first inductor, said energy storage portion being arranged such that a first terminal of the second inductor is connected to an anode of the second diode, a cathode of the second diode is connected to a first terminal of the energy storage element, and a second terminal of the energy storage element is connected to a second terminal of the second inductor, wherein the first terminal of the energy storage element is connected to the input node via a second switch; and a controller arranged such that: when the input voltage is not less than a threshold value, the controller operates the power converter in a first mode in which a first pulse width modulation signal is applied to the first switch and the second switch is opened; and characterised in that when the input voltage is less than the threshold value, the controller operates the power converter in a second mode in which the first switch is opened and a second pulse width modulation signal is applied to the second switch. a buck converter portion comprises a first diode, a first inductor, and a capacitor, said buck converter portion being arranged such that a first terminal of the first inductor is connected to a cathode of the first diode at an input node, a second terminal of the first inductor is connected to a first terminal of the capacitor at an output node, and an anode of the first diode is connected to a second terminal of the capacitor at a first ground node, wherein the input node is connected to an input voltage via a first switch, and wherein the buck converter portion is arranged to supply an output voltage at the second terminal of the inductor; an energy storage portion comprising a second diode, an energy storage element, and a second inductor magnetically coupled to the first inductor, said energy storage portion being arranged such that a first terminal of the second inductor is connected to an anode of the second diode, a cathode of the second diode is connected to a first terminal of the energy storage element, and a second terminal of the energy storage element is connected to a second terminal of the second inductor, wherein the first terminal of the energy storage element is connected to the input node via a second switch; and a controller arranged such that: when the input voltage is not less than a threshold value, the controller operates the power converter in a first mode in which a first pulse width modulation signal is applied to the first switch and the second switch is opened; and characterised in that when the input voltage is less than the threshold value, the controller operates the power converter in a second mode in which the first switch is opened and a second pulse width modulation signal is applied to the second switch. when the input voltage is not less than a threshold value, the controller operates the power converter in a first mode in which a first pulse width modulation signal is applied to the first switch and the second switch is opened; and characterised in that when the input voltage is less than the threshold value, the controller operates the power converter in a second mode in which the first switch is opened and a second pulse width modulation signal is applied to the second switch.