Battery charging circuit with improved system stability and control method thereof

A battery charging circuit, comprising:

• a switching circuit having at least one switch and an inductor coupled to the at least one switch;
• a first difference circuit configured to receive a charging current feedback signal and a charging current reference signal and to provide a first difference signal at an output terminal;
• a second difference circuit configured to receive a battery voltage feedback signal and a battery voltage reference signal and to provide a second difference signal at an output terminal;
• a selection circuit having a first input terminal configured to receive the first difference signal and a second input terminal configured to receive the second difference signal, wherein based on a battery voltage, the selection circuit selects one of the first difference signal, the second difference signal and a ground voltage as a third difference signal at an output terminal;
• a bias circuit coupled to the output terminal of the selection circuit to receive the third difference signal, the bias circuit proportionally integrates the third difference signal and provides a bias signal at an output terminal;
• a comparison circuit having a first input terminal, a second input terminal and an output terminal, wherein the first input terminal is configured to receive the sum of the bias signal and a system voltage reference signal, the second input terminal is configured to receive the sum of a system voltage feedback signal and a ramp signal, the comparison circuit provides a comparison signal at the output terminal, and wherein the sum of the bias signal and the system voltage reference signal is a bias reference signal;
• a constant time period control circuit configured to provide a constant time period control signal;
• and
• a logic circuit configured to receive the comparison signal and the constant time period control signal, wherein the logic circuit provides a control signal at an output terminal to control the at least one switch.

A control method for controlling a battery charging circuit having at least one switch and an inductor coupled to the at least one switch, the control method comprising:

• generating a first difference signal based on the difference between a charging current feedback signal and a charging current reference signal;
• generating a second difference signal based on the difference between a battery voltage feedback signal and a battery voltage reference signal;
• based on a battery voltage, selecting one of the first difference signal, the second difference signal and a ground voltage as a third difference signal;
• generating a bias signal by proportionally integrating the third difference signal;
• comparing the sum of a system voltage feedback signal and a ramp signal with the sum of the bias signal and a system voltage reference signal and generating a comparison signal;
• generating a constant time period control signal;
• and
• generating a control signal for controlling the at least one switch based on the comparison signal and the constant time period control signal.