A power supply for generating a supply voltage (Vsupply) between a positive voltage output terminal (VOUTP) and a negative voltage output terminal (VOUTN) comprising: a pulse width modulation, PWM, signal generator to generate at least one switching signal (SWH; SWL) according to a voltage error signal (VERROR); a power conversion circuit coupled to the positive voltage output terminal and the negative voltage output terminal and comprising an inductor, wherein the power conversion circuit is operable to generate a switching voltage to the inductor according to the at least one switching signal so as to generate the supply voltage between the positive voltage output terminal and the negative voltage output terminal, the positive voltage output terminal and negative voltage output terminal for connecting to a positive voltage input terminal (VINP) and negative voltage input terminal (VINN) of a load respectively; a first error amplifier having a positive input terminal operable to receive a reference voltage (VREF) and a negative input terminal operable to receive a first voltage signal (VFBP) and detect a difference between the first voltage signal and the reference voltage, wherein the first voltage signal is related to a voltage at the positive voltage input terminal (VINP), and an output terminal of the first error amplifier is coupled to a first node; and a second error amplifier having a positive input terminal operable to receive a second voltage signal (VFBN) and a negative input terminal operable to receive a ground voltage and detect a difference between the second voltage signal and the ground voltage, wherein the second voltage signal is related to a voltage at the negative voltage input terminal (VINN), and an output terminal of the second error amplifier is coupled to the first node; and wherein the voltage error signal is generated at the first node, and the PWM signal generator is operable to modulate a duty cycle of the at least one switching signal according to a variation of the voltage error signal, characterized in that the power supply further comprises a determination circuit operable to determine whether the load is a light-load according to a current flowing through the inductor; and wherein the determination circuit is configured to cause the second error amplifier to be disabled, such that it does not operate, when the determination circuit determines that the supply voltage is provided in the light-load condition. a pulse width modulation, PWM, signal generator to generate at least one switching signal (SWH; SWL) according to a voltage error signal (VERROR); a power conversion circuit coupled to the positive voltage output terminal and the negative voltage output terminal and comprising an inductor, wherein the power conversion circuit is operable to generate a switching voltage to the inductor according to the at least one switching signal so as to generate the supply voltage between the positive voltage output terminal and the negative voltage output terminal, the positive voltage output terminal and negative voltage output terminal for connecting to a positive voltage input terminal (VINP) and negative voltage input terminal (VINN) of a load respectively; a first error amplifier having a positive input terminal operable to receive a reference voltage (VREF) and a negative input terminal operable to receive a first voltage signal (VFBP) and detect a difference between the first voltage signal and the reference voltage, wherein the first voltage signal is related to a voltage at the positive voltage input terminal (VINP), and an output terminal of the first error amplifier is coupled to a first node; and a second error amplifier having a positive input terminal operable to receive a second voltage signal (VFBN) and a negative input terminal operable to receive a ground voltage and detect a difference between the second voltage signal and the ground voltage, wherein the second voltage signal is related to a voltage at the negative voltage input terminal (VINN), and an output terminal of the second error amplifier is coupled to the first node; and wherein the voltage error signal is generated at the first node, and the PWM signal generator is operable to modulate a duty cycle of the at least one switching signal according to a variation of the voltage error signal, characterized in that the power supply further comprises a determination circuit operable to determine whether the load is a light-load according to a current flowing through the inductor; and wherein the determination circuit is configured to cause the second error amplifier to be disabled, such that it does not operate, when the determination circuit determines that the supply voltage is provided in the light-load condition.