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  Controller for dc to dc converterUSPTO Application #: 20060284608Title: Controller for dc to dc converter Abstract: A method includes starting a time count of a time interval at a start of a state change of a switch of a DC to DC converter; monitoring if the switch is in a skip mode; and disabling the skip mode in response to an expiration of the time interval so that the switch changes states at a frequency rate greater than an audible frequency for humans. (end of abstract)
Agent: Grossman, Tucker, Perreault & Pfleger, PLLC - Manchester, NH, US Inventors: Laszlo Lipcsei, Serban-Mihai Popescu USPTO Applicaton #: 20060284608 - Class: 323284000 (USPTO) The Patent Description & Claims data below is from USPTO Patent Application 20060284608. Brief Patent Description - Full Patent Description - Patent Application Claims
CROSS REFERENCE TO RELATED APPLICATIONS [0001] This application is a continuation of U.S. Nonprovisional application Ser. No. 11/037,598 filed on Jan. 18, 2005, now U.S. Pat. No. 7,098,624, the teachings of which are incorporated herein by reference, which itself is a continuation application of U.S. Nonprovisional application Ser. No. 10/668,459 filed on Sep. 23, 2003, now U.S. Pat. No. 6,844,710, the teachings of which are incorporated herein by reference, which itself is a continuation-in-part application of U.S. Nonprovisional application Ser. No. 10/389,037 filed on Mar. 14, 2003, now U.S. Pat. No. 6,965,221, the teachings of which are also incorporated herein by reference, all of which claim the benefit of the filing date of U.S. Provisional Application Ser. No. 60/425,553, filed Nov. 12, 2002, the teachings of which are also incorporated herein by reference. FIELD OF THE INVENTION [0002] The present invention relates to controllers for DC to DC converters and in particular to controllers for controlling inductor current levels without directly measuring such current levels. BACKGROUND OF THE INVENTION [0003] DC to DC converters are used to convert an input DC voltage to an output DC voltage. Such converters may step down (buck) or step up (boost) the input DC voltage. One type of buck converter is a synchronous buck converter. This converter typically has a controller, driver, a pair of switches, and an LC filter coupled to the pair of switches. The controller provides a control signal to the driver which then drives the pair of switches, e.g., a high side switch and a low side switch. The driver alternately turns each switch ON and OFF thereby controlling inductor current and the output voltage of the DC to DC converter. Such controllers typically utilize a pulse width modulated signal to control the state of the high and low side switches. [0004] In general, if the PWM signal is high, the high side switch is ON and the low side switch if OFF. This state of switches will be referred to herein as a "switch ON" state. In this state, the inductor is coupled to the input voltage source. In a buck converter, the input voltage is necessarily greater than the output voltage so there is a net positive voltage across the inductor in this switch ON state. Accordingly, the inductor current begins to ramp up. If the PWM signal is low, the high side switch is OFF and the low side switch is ON. This state of switches will be referred to as a "switch OFF" state. In a buck converter, there is a net negative voltage across the inductor in this state. Accordingly, the inductor current begins to ramp down during this low side switch OFF state. Hence, the pulse width of the PWM signal determines the time on for the switch ON state and the time off for the switch OFF state. Such pulse width may be adjusted by directly monitoring the inductor current level via a sense resistor or by comparing the output voltage with a reference voltage level. [0005] Accordingly, there is a need in the art for a controller for a DC to DC converter that provides a PWM signal during a first time interval based on an input voltage to the DC to DC converter less a signal representative of the output voltage. BRIEF DESCRIPTION OF THE DRAWINGS [0006] Advantages of the present invention will be apparent from the following detailed description of exemplary embodiments thereof, which description should be considered in conjunction with the accompanying drawings, in which: [0007] FIG. 1A is a block diagram of a DC to DC converter including a controller consistent with the present invention; [0008] FIG. 1B is an exemplary table illustrating switch states for the pair of switches of FIG. 1A based on the input PWM signal and low side enable signal; [0009] FIG. 2A is a block diagram of one embodiment of a controller for use with the DC to DC converter of FIG. 1; [0010] FIG. 2B is a plot illustrating the changes in charge level on the energy storage element of the controller of FIG. 2A compared to the associated changes in inductor current levels over similar time intervals; [0011] FIG. 3 is a block diagram of another embodiment of a controller for use with the DC to DC converter of FIG. 1; [0012] FIG. 4 is a more detailed block diagram of an exemplary delay circuit of FIG. 3; [0013] FIG. 5 is a block diagram of another embodiment of a controller for use with the DC to DC converter of FIG. 1; [0014] FIG. 6 is a block diagram of an exemplary dual phase controller; [0015] FIG. 7 is a circuit diagram of an input voltage sensing circuit using the LX pin of the controller; [0016] FIG. 8 is a block diagram of another embodiment of a controller consistent with the invention having an internal timer for controlling a minimum switching frequency; [0017] FIG. 9 is a block diagram of a DC to DC converter having a timer external the controller for controlling a minimum switching frequency; and [0018] FIG. 10 is a timing diagram for the embodiments of FIGS. 9 and 10. DETAILED DESCRIPTION [0019] FIG. 1A illustrates an exemplary DC to DC converter 100 including a controller 102 consistent with the present invention. The controller 102 consistent with the invention may be utilized with a variety of DC to DC converters. The illustrated DC to DC converter 100 is a synchronous buck converter generally including the controller 102, a driver circuit 104, a pair of switches 106 including a high side switch Q1 and a low side switch Q2, and a low pass filter 108. The low pass filter includes an inductor L and a capacitor C. Continue reading... Full patent description for Controller for dc to dc converter Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Controller for dc to dc converter patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. 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