Abstract: The invention discloses a power supply with a frequency conversion function. The power supply is connected with a motherboard. The power supply includes a pulse width modulation (PWM) controller, a direct current-direct current (DC-DC) converter, and a switch resistor modulation circuit. The PWM controller generates a PWM signal. The DC-DC converter is connected with the PWM controller and the motherboard, and it generates a plurality of voltages to the motherboard after it receives the PWM signal. The switch resistor modulation circuit provides a first resistance value and a second resistance value switched to correspondingly generate a first switching frequency or a second switching frequency. The second resistance value is larger than the first resistance value. The second switching frequency is smaller than the first switching frequency.