Switching mode charger with pass through mode

A circuit, comprising:

• a first transistor having a drain terminal coupled to a first node, a source terminal coupled to a second node, and a gate terminal, the first node is adapted to be coupled to a voltage supply operable to supply a bus voltage;
• a second transistor having a source terminal coupled to a third node, a drain terminal coupled to a fourth node, and a gate terminal, the fourth node is adapted to be coupled to a load;
• a third transistor having a drain terminal coupled to the second node, a source terminal coupled to a ground node, and a gate terminal;
• and
• a fourth transistor having a drain terminal coupled to the third node, a source terminal coupled to the ground node, and a gate terminal;
• a fifth transistor having a drain terminal coupled to the fourth node, a source terminal coupled to a sixth node, and a gate terminal, the sixth node is adapted to be coupled to a battery, and
• a controller coupled to the gate terminal of the first transistor, the second transistor, the third transistor, the fourth transistor and the fifth transistor, wherein the controller is configured to:
• turn on the first and second transistors while turning off the third, fourth and fifth transistors during first operational circumstances;
• and
• control the first, second, third, fourth and fifth transistors to operate as components of a buck-boost power converter under second operational circumstances to generate a system voltage present at the fourth node based on the bus voltage, the system voltage having a different value as a result of power switching of the first transistor or the second transistor than a value of the bus voltage.