A voltage converter includes a voltage conversion circuit, a pulse width modulation (PWM) signal generating module, a feedback controlling module, and a subtractor. The voltage conversion circuit is configured to convert an input voltage to an output voltage according to a PWM signal. The PWM signal generating module is configured to generate the PWM signal according to a control signal. The feedback controlling module is configured to generate the control signal according to a feedback signal. The subtractor is configured to subtract a first reference voltage by the output voltage, to generate the feedback signal. The phase of an AC component of the first reference voltage is substantially opposite to the phase of the input voltage.