Power Conversion Device and Control Method Thereof

A power conversion device, comprising:

• an input terminal, configured to receive an input voltage;
• an output terminal, configured to provide an output voltage;
• a first, a second, a third, and a fourth switching elements, wherein the first switching element is connected between the input terminal and the second switching element, the second switching element is connected to the third switching element, the fourth switching element is connected between the third switching element and the output terminal, a connection between the first and second switching elements forms a first node, a connection between the third and fourth switching elements forms a second node, and a connection between the second and third switching elements forms a third node;
• an inductor, connected between the first node and the second node;
• a low-side current sensing module, disposed between the third node and a ground terminal, configured to sense a current between the third node and the ground terminal when the first to fourth switching elements operate in an input voltage grounding state and an output voltage grounding state, and to generate a sensing signal;
• and
• a control circuit, coupled to the low-side current sensing module, the output terminal, and the first to fourth switching elements, configured to dynamically switch the first to fourth switching elements to operate in a boost mode, a buck mode, and a buck-boost mode based on the sensing signal, a duty cycle of the input voltage grounding state, and a duty cycle of the output voltage grounding state, thereby controlling the first to fourth switching elements to convert the input voltage into the output voltage with a target voltage value;
• wherein, in the buck-boost mode, the control circuit controls the first to fourth switching elements to periodically operate in the input voltage grounding state, the output voltage grounding state, and an input voltage to output voltage state, and extends the duty cycle of the input voltage grounding state or the duty cycle of the output voltage grounding state.