BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic block diagram of a switching power supply with ripple suppression in accordance with a preferred embodiment of the present invention;
FIG. 2 shows a circuit diagram of a DC/DC converting circuit of the switching power supply of FIG. 1;
FIG. 3 shows an alternative circuit diagram of the DC/DC converting circuit; and
FIG. 4 is a schematic block diagram of a traditional switching power supply of the related art.
DETAILED DESCRIPTION OF THE EMBODIMENTS
Referring to FIG. 1, a schematic diagram of a switching power supply with ripple suppression is shown. As Compared with the traditional switching power supply shown in FIG. 4, the switching power supply 2 further includes a DC/DC (direct current-to-direct current) converting circuit 80. The DC/DC converting circuit 80 is connected in series with the voltage stabilization circuit 70 in the switching power supply 2 and executes a DC-to-DC power conversion before output DC power to the DC load. The DC/DC converting circuit 80 is provided with a feedback control function that is used for stabilizing an output voltage to the DC load according to feedback signals from the output voltage, thus reducing ripples that exist in the output voltage.
Referring to FIG. 2, an exemplary circuit diagram of the DC/DC converting circuit 80 is shown. The DC/DC converting circuit 80 of FIG. 1 embodied in FIG. 2 is a buck converting circuit 801 and includes a switching circuit S connected between the voltage stabilization circuit 70 and an output terminal 90 of the switching power supply 2. The output terminal 90 is used for connecting the switching power supply 2 with the DC load. As shown in FIG. 2, the switching circuit is presented using a MOS (Metal-Oxide-Semiconductor) transistor S that is controlled by a PWM (pulse width modulation) generator 810. The PWM generator 810 includes a driving signal output port DR and a feedback signal receiving port FB. The driving signal output port DR is connected with the MOS transistor S and the feedback signal receiving port FB is connected to a feedback circuit. The feedback circuit is actually a voltage dividing circuit as presented in FIG. 2. The voltage dividing circuit is made up with two resistors R1 and R2. The resistors R1 and R2 are serially connected between the output terminal 90 of the switching power supply 2 and ground. The feedback signal receiving port FB of the PWM generator 810 is connected between the resistors R1, R2 and receives feedback signals from the voltage dividing circuit. The feedback signals reflect the actual output voltage to the DC load. The PWM generator 810 generates PWM waves to control an on-off time ratio of the switching circuit S by comparing the feedback signals to a reference signal that reflects a desired output voltage.
Also referring to FIG. 2, an inductor L is connected between the switching circuit S and the output terminal 90 of the switching power supply 2. A diode D and a capacitor C are connected on opposite sides of the inductor L. Concretely, the diode D is inversely connected between the switching circuit S and ground, and the capacitor C is connected between the output terminal 90 of the switching power supply 2 and ground. The capacitor C filters the ripples in the output voltage.
Referring to FIG. 3, an alternative exemplary circuit diagram of the DC/DC converting circuit 80 is shown. The DC/DC converting circuit 80 in FIG. 3 is a boost converting circuit 802. The inductor L and the diode D are serially connected between the voltage stabilization circuit 70 and the output terminal 90 of the switching power supply 2. The inductor L is connected with an anode of the diode D. The switching circuit S and the capacitor C are connected on opposite sides of the diode D, concretely, the switching circuit S is connected between the anode of the diode D and the ground, and the capacitor C is connected between a cathode of the diode D and the ground.
It is believed that the present embodiments and their advantages will be understood from the foregoing description, and it will be apparent that various changes may be made thereto without departing from the spirit and scope of the invention or sacrificing all of its material advantages, the examples hereinbefore described merely being preferred or exemplary embodiments of the invention.