Power management circuit and electronic device

A power source (100) includes a first power terminal (101) for outputting a first supply voltage. A power management circuit (200) includes a pulse width modulation unit (24) having an input power terminal (240), a first switch unit (22) capable of being turned on to establish an electrical connection between the first power terminal (101) and the input power terminal (240) or being turned off to cut off the electrical connection, and a storage unit (25). The input power terminal (240) receives the first supply voltage from the first power terminal (101) when the first switch unit (22) is turned on, the pulse width modulation unit (24) is powered by the first supply voltage to generate a pulse voltage at the output terminal (242). The storage unit (25) receives the first supply voltage to store energy when the pulse voltage is in a first level, and releases energy to generate an operating voltage for powering the load (300) when the pulse voltage is in a second level.