A method of dynamically controlling minimum duty cycle, comprising: turning off a high-side switch and turning on a low-side switch during a charging period for allowing a direct-current, DC, voltage to charge a capacitor coupled between a direct-current, DC, voltage (V DC) and an output end (N OUT); turning on the high-side switch and turning off the low-side switch during a discharging period subsequent to the charging period for allowing energy stored in the capacitor to charge parasite capacitance (C PH) between a control end of the high-side switch and a second end of the high-side switch, thereby keeping the high-side switch turned on and allowing a bus voltage (V BUS) to be transmitted to the output end (N OUT) for driving a motor; and adjusting a first turn-on time of the high-side switch during the discharging period according to a status of the output end (N OUT); wherein the high-side switch includes a first end coupled to the bus voltage (VBUS) and a second end coupled to the output end (NOUT); wherein the low-side switch includes a first end coupled to the output end (NOUT) and a second end coupled to a ground voltage; characterized by limiting a second turn-on time of the low-side switch during the charging period according to a dynamically controlled minimum duty cycle curve, wherein: a value of the dynamically controlled minimum duty cycle curve is not larger than a maximum value when a rotational speed of the motor is not larger than a first rotational speed; wherein the value of the dynamically controlled minimum duty cycle curve is equal to the maximum value when the rotational speed of the motor is equal to the first rotational speed; and wherein the value of the dynamically controlled minimum duty cycle curve is not larger than the maximum value when the rotational speed of the motor is greater than the first rotational speed. turning off a high-side switch and turning on a low-side switch during a charging period for allowing a direct-current, DC, voltage to charge a capacitor coupled between a direct-current, DC, voltage (V DC) and an output end (N OUT); turning on the high-side switch and turning off the low-side switch during a discharging period subsequent to the charging period for allowing energy stored in the capacitor to charge parasite capacitance (C PH) between a control end of the high-side switch and a second end of the high-side switch, thereby keeping the high-side switch turned on and allowing a bus voltage (V BUS) to be transmitted to the output end (N OUT) for driving a motor; and adjusting a first turn-on time of the high-side switch during the discharging period according to a status of the output end (N OUT); wherein the high-side switch includes a first end coupled to the bus voltage (VBUS) and a second end coupled to the output end (NOUT); wherein the low-side switch includes a first end coupled to the output end (NOUT) and a second end coupled to a ground voltage; characterized by limiting a second turn-on time of the low-side switch during the charging period according to a dynamically controlled minimum duty cycle curve, wherein: a value of the dynamically controlled minimum duty cycle curve is not larger than a maximum value when a rotational speed of the motor is not larger than a first rotational speed; wherein the value of the dynamically controlled minimum duty cycle curve is equal to the maximum value when the rotational speed of the motor is equal to the first rotational speed; and wherein the value of the dynamically controlled minimum duty cycle curve is not larger than the maximum value when the rotational speed of the motor is greater than the first rotational speed. a value of the dynamically controlled minimum duty cycle curve is not larger than a maximum value when a rotational speed of the motor is not larger than a first rotational speed; wherein the value of the dynamically controlled minimum duty cycle curve is equal to the maximum value when the rotational speed of the motor is equal to the first rotational speed; and wherein the value of the dynamically controlled minimum duty cycle curve is not larger than the maximum value when the rotational speed of the motor is greater than the first rotational speed.