Modification of switch activation order in a power supply

#This application is related to U.S. patent application Ser. No. 11/969,655 entitled “POWER SUPPLY AND CONTROLLER CIRCUITS,”, filed on the same day as the present application, the entire teachings of which are incorporated herein by this reference.

#This application is related to U.S. patent application Ser. No. 11/969,659 entitled “POWER SUPPLY AND CONTROLLER CIRCUITS,”, filed on the same day as the present application, the entire teachings of which are incorporated herein by this reference.

#This application is related to U.S. patent application entitled “Method and Apparatus for Equalizing Phase Currents in Multiphase Switching Power Converters”, which has been assigned U.S. patent application Ser. No. 11/897,290, and was filed on Aug. 30, 2007, the entire teachings of which are incorporated herein by this reference.

#The foregoing and other objects, features, and advantages of the invention will be apparent from the following more particular description of preferred embodiments herein, as illustrated in the accompanying drawings in which like reference characters refer to the same parts throughout the different views. The drawings are not necessarily to scale, with emphasis instead being placed upon illustrating the embodiments, principles and concepts.

#FIG. 1 is a schematic diagram of a prior art single phase synchronous buck converter;

#FIG. 2 is a plot of estimated output capacitance versus load current for the invention compared with prior art VRMs;

#Digital control has many advantages over analog control in a power converter. One of the most important advantages relates to the flexibility of digital control. Various control schemes that may be difficult to implement in analog control become feasible when digital control is applied. However, no previous digital controllers for VRMs provide satisfactory solutions for transient load conditions, particularly the transients expected to be presented by future microprocessors.

#A digital controller as described herein provides a novel solution to the control of a VRM during transients, by employing voltage sensing of the VRM output voltage. By sensing minute changes in the output voltage, and relating the output voltage to the corresponding required output current (e.g., predicting the output current from the sensed output voltage), a digital controller as described herein may respond quickly to sudden demands for current that would otherwise result in a substantial drop in output voltage, compromising performance of the load. As exemplified by the embodiments described herein, the digital controller of the invention has been optimized to work in conjunction with either a dynamic conversion circuit and a power converter, such as a buck converter, or with only a power converter, as use of the digital controller to enhance performance of any power converter may be accomplished with only minor modifications to the embodiments described herein.

#By implementing the digital controller and the control method of the invention, increasing the switching frequency of the DC-DC converter is unnecessary, because an increased switching frequency does not further improve the dynamic response of the converter. The switching frequency may be kept below 500 kHz to achieve a higher efficiency and at the same time maintain a very fast dynamic response with greatly reduced output capacitance. The greatly reduced output capacitance enables the use of ceramic capacitors, which are smaller in size and have a much smaller equivalent series resistance (ESR). Consequently, a VRM according to the invention will require less space on a PCB and cost will be reduced. Further, the digital implementation offers great flexibility, including external programming, such that no analog components need to be substituted under different conditions. Factors such as tolerance, temperature, and aging of components have no effect on components such as the compensator due to the digital implementation.