Method for power management and an electronic system using the same

An electronic system, comprising:

• a central processing unit, wherein the power state of the central processing unit includes a working state, a first low-power state and a second low-power state;
• a plurality of peripheral modules;
• an a power-management module, setting the central processing unit in a first low-power state when receiving a request requiring the central processing unit to enter the second low-power state,
• wherein the power-management module is configured to obtain first idle periods of the peripheral modules respectively, determine a second idle period according to the first idle periods of the peripheral modules, and determine whether the peripheral modules have not sent a data-access request during the second idle period;
• wherein when the peripheral modules have not sent the data-access request during the second idle period, the power-management module sets the central processing unit in the second low-power state;
• and
• wherein each first idle period is an interval period between two data transmissions of each peripheral module.