A power supply device includes a power circuit, feedback circuit, compensation circuit, and PWM controller. The power circuit generates an output voltage based on a PWM signal. The feedback circuit outputs a feedback voltage. The compensation circuit compares a reference voltage with the feedback voltage and outputs a compensation signal based on a comparison result. The PWM controller adjusts the duty ratio of the PWM signal based on the compensation signal. The compensation circuit includes a comparator to compare the feedback voltage with the reference voltage, a first voltage adjuster to adjust a voltage level of a compensation voltage based on the comparison result, and a compensator output the compensation signal based on the voltage level of the compensation voltage. The compensation signal has a width in a high section that varies. The booster boosts the response speed of the compensator in a predetermined section based on a control signal.