Switching charger, the control circuit and the control method thereof

A control circuit for a switching charger, wherein the switching charger has a high-side power switch, a low-side power switch and an inductor, the control circuit comprising:

• a feedback amplifier having a first input terminal configured to receive a feedback signal indicating the charging voltage, a second input terminal configured to receive a feedback reference signal, and an output terminal configured to generate an amplified feedback signal based on the feedback signal and the feedback reference signal;
• a select circuit having a first input terminal configured to receive a current reference signal, a second input terminal coupled to the feedback amplifier to receive the amplified feedback signal, and an output terminal configured to generate a current control signal based on the current reference signal and the amplified feedback signal, wherein the current control signal is either the current reference signal or the amplified feedback signal whichever has the lower value;
• a hysteretic control circuit having a first input terminal coupled to the output terminal of the select circuit to receive the current control signal, a second input terminal configured to receive the input voltage, a third input terminal configured to receive the charging voltage, a fourth input terminal coupled to the output terminal of the control circuit to receive the control signal, and a fifth input terminal configured to receive a frequency control signal having pulses at moment when the power stage is turned ON, wherein based on the current control signal, the input voltage, the charging voltage, the control signal and the frequency control signal, the hysteretic control circuit provides a lower limit signal via a first output terminal, and a higher limit signal via a second output terminal;
• a comparison circuit having a first input terminal coupled to the first output terminal of the hysteretic control circuit to receive the lower limit signal, a second input terminal coupled to the second output terminal of the hysteretic control circuit to receive the higher limit signal, a third input terminal configured to receive a current sense signal indicating a current flowing through the inductor, and based on the lower limit signal, the higher limit signal, and the current sense signal, the comparison circuit provides a set signal via a first output terminal, and a reset signal via a second output terminal;
• and
• a logic circuit having a set terminal coupled to the comparison circuit to receive the set signal, a reset terminal coupled to the comparison circuit to receive the reset signal, and an output terminal configured to generate the control signal based on the set signal and the reset signal.

A control method for a switching charger, wherein the switching charger has a high-side power switch, a low-side power switch and an inductor, the control method comprising:

• amplifying an error between a feedback signal indicating an output voltage of the switching charger and a feedback reference signal to generate an amplified feedback signal;
• selecting the smaller value of the amplified feedback signal and a current reference signal to be a current control signal;
• generating a hysteretic window signal;
• generating a higher limit signal and a lower limit signal based on the current control signal and the hysteretic window signal;
• turning OFF the high-side power switch when the a current sense signal indicating a current flowing through the inductor is higher than the higher limit signal, and turning ON the high-side power switch when the current sense signal is lower than the lower limit signal.