Power conversion system and method thereof

A power conversion system, comprising:

• a first switch, which is coupled between a first terminal and an intermediate node;
• a second switch, which is coupled between a second terminal and the intermediate node;
• a switching power converter, which is coupled between the intermediate node and a system node;
• a battery switch, which is coupled between the system node and a battery;
• and
• a conversion control circuit, which is configured to operably control the first switch, the second switch, the battery switch and the switching power converter, so as to control power conversion among a first power at the first terminal, a second power at the second terminal, an intermediate power at the intermediate node, a system power at the system node and a battery power at the battery;
• wherein in an external power supply mode, the conversion control circuit is configured to operably control the first switch to be ON to conduct the first power to generate the intermediate power, and the conversion control circuit is configured to operably control the second switch to be ON to conduct the intermediate power to generate the second power for powering an external load, and the conversion control circuit is configured to operably control the switching power converter to convert the intermediate power to the system power for powering a system load;
• wherein in a battery power supply mode, the conversion control circuit is configured to operably control the battery switch to be ON to conduct the battery power to generate the system power, and the conversion control circuit is configured to operably control the switching power converter to convert the system power to the intermediate power, and the conversion control circuit is configured to operably control the second switch to be ON to conduct the intermediate power to generate the second power for powering the external load, wherein the intermediate power includes an intermediate voltage, wherein the intermediate voltage is regulated to an intermediate regulation level;
• wherein in the external power supply mode, when the intermediate voltage is reduced to a transient state threshold, the conversion control circuit is configured to operably control the switching power converter to enter the battery power supply mode, wherein the intermediate regulation level is close to a minimum voltage regulation level or the intermediate regulation level is not lower than the minimum voltage regulation level.