| Enabling circuit for avoiding negative voltage transients -> Monitor Keywords |
|
|
  Enabling circuit for avoiding negative voltage transientsThe Patent Description & Claims data below is from USPTO Patent Application 20070030714. Brief Patent Description - Full Patent Description - Patent Application Claims
CROSS REFERENCE TO RELATED APPLICATIONS [0001] This application is a continuation of prior application Ser. No. 11/142,505 filed Jun. 1, 2005, now U.S. Pat. No. 7,112,943, which itself is a continuation of prior application Ser. No. 10/738,058 filed Dec. 17, 2003, now U.S. Pat. No. 6,906,497, which itself is a continuation of prior application Ser. No. 10/176,141, filed Jun. 20, 2002, now U.S. Pat. No. 6,756,769, the teachings of which are incorporated herein by reference. FIELD OF THE INVENTION [0002] This invention relates to an enabling circuit for avoiding negative voltage transients from an associated regulating circuit, and more particularly to such an enabling circuit for enabling a synchronous rectifier converter to switch from a first state to second state if the charge on an energy storage element of the synchronous rectifier converter is less than a reference charge. BACKGROUND OF THE INVENTION [0003] A variety of circuits have energy storage element such as capacitors, inductors, and transformers that transfer energy from an input to an output of such circuits. If such energy storage elements are not properly discharged in some instances, unwanted power disturbances, e.g., negative voltage transients, may occur in the output signal causing damage to nearby sensitive components. [0004] For instance, such a regulating circuit may be a DC-DC converter. DC-DC converters generally accept a DC input at one voltage level and convert it to a DC output at a higher or lower voltage level. Such DC-DC converters may be used in a wide variety of electronic devices in conjunction with a variety of systems. One such system may be used to provide a battery charging function for portable electronic devices such as laptop computers, cell phones, pagers, personal digital assistants, and the like. [0005] One type of DC-DC converter is a synchronous rectifier converter (SRC). An SRC does not use any Schottky diodes, but rather uses transistors referred to as "synchronous rectifiers." Such transistors may be a variety of transistors such as MOS or MOSFET transistors. An SRC may also have a variety of internal components that typically include an energy storage element, e.g., a capacitor, inductor, or transformer, with one or more transistors controlled by various control techniques, e.g., pulse width modulation where the switch frequency is constant and the duty cycle varies with the load. [0006] When an SRC is used in conjunction with a battery power management system, the SRC may accept an input voltage from a number of different power sources and convert it to an appropriate output voltage to, among other things, provide an appropriate charging current to an associated rechargeable battery. In such a battery power management system, there is typically an associated controller used to control the battery charging process. Such controller may be an integrated circuit (IC) having a plurality of input terminals or pins, some of which are connected to the output of the SRC. For instance, two such terminals may be coupled to either side of a sense resistor. The sense resistor may be in series with the output of the SRC such that it provides a signal representative of the charging current provided at the output of the SRC. [0007] If a soft start occurs when the energy storage element, e.g., a capacitor, of the SRC is charged at a significant value, e.g., over several volts, negative voltage transients may appear on either terminal of the sense resistor potentially causing catastrophic failure of the associated controller IC. Accordingly, there is a need for an enabling circuit and method that overcomes the above deficiencies in the prior art and is capable of avoiding negative voltage transients from an associated regulating circuit by enabling the regulating circuit only when the charge on the energy storage element is below a reference charge. BRIEF SUMMARY OF THE INVENTION [0008] According to one aspect of the invention, there is provided an enabling circuit for enabling a DC-DC converter having a capacitor coupled to an output terminal of the DC-DC converter to be controlled by a control signal. The enabling circuit may include a comparison circuit configured to compare a feedback signal representative of a charge on the capacitor with a signal representative of a reference charge and to provide an output to in response to the comparison to enable the DC-DC converter to be controlled by the control signal if the charge on the capacitor is less than the reference charge. The enabling circuit may also include a discharge path configured to discharge the charge on the capacitor if the charge is greater than the reference charge. [0009] According to another aspect of the invention, there is provided a system. The system may include a DC-DC converter configured to accept an input power level from a power source and provide a regulated output power level to a load. The DC-DC converter may have a capacitor coupled to an output terminal of the DC-DC converter. The system may further include an enabling circuit for enabling the DC-DC converter to be controlled by a control signal. The enabling circuit may include a comparison circuit configured to compare a feedback signal representative of a charge on the capacitor with a signal representative of a reference charge and to provide an output to in response to the comparison to enable the DC-DC converter to be controlled by the control signal if the charge on the capacitor is less than the reference charge. The enabling circuit may also include a discharge path configured to discharge the charge on the capacitor if the charge is greater than the reference charge. [0010] According to yet another aspect of the invention there is provided a method. The method may include monitoring a charge on a capacitor of a DC-DC converter coupled to an output terminal of said DC-DC converter; preventing the DC-DC converter from being controlled by a control signal if the charge is greater than the reference charge; and enabling the DC-DC converter to be controlled by the control signal if the charge is less than the reference charge. BRIEF DESCRIPTION OF THE DRAWINGS [0011] For a better understanding of the present invention, together with other objects, features and advantages, reference should be made to the following detailed description which should be read in conjunction with the following figures wherein like numerals represent like parts: [0012] FIG. 1 is a block diagram of a system including an enabling circuit consistent with the present invention for enabling an associated regulating circuit to switch from a first state to a second state; [0013] FIG. 2 is a block diagram of an exemplary enabling circuit consistent with the invention for enabling an associated synchronous rectifier converter to switch from one state to another state; [0014] FIG. 2A is a circuit diagram illustrating an exemplary embodiment of the enabling circuit of FIG. 2; and [0015] FIG. 3 is a block diagram of a battery management system utilizing the enabling circuit of FIG. 2. DETAILED DESCRIPTION [0016] Turning to FIG. 1, an exemplary system 100 including an enabling circuit 104 and an associated regulating circuit 102 is illustrated. The regulating circuit 102 may be any variety of circuits, e.g., a synchronous rectifier converter, containing an energy storage element 106, e.g., a capacitor. In general, the enabling circuit 104 monitors the charge on the energy storage element 106 and enables the regulating circuit 102 to switch from a first state to a second state when the charge on the energy storage element is below a reference charge. The first state may be any variety of states such as a power off state, and the second state may also be any variety of states such as an operating state where the regulating circuit 102 is controlled by a particular control technique. The reference charge should be chosen based on the particular system and sensitivity of associated components. In one embodiment, the reference charge may be 3.0 volts. [0017] The enabling circuit 104 has one input terminal 107 configured to accept a signal, Vdsch, representative of an acceptable reference charge level for the energy storage element 106. The enabling circuit 104 may have another input terminal 109 configured to accept a logic control signal chginh. Such logic control signal, chginh, has a predetermined state, e.g., low state, when at least one non energy storage element condition related to operation of the regulating circuit 102 is satisfied. Such a condition or conditions may be any variety of other conditions known to those skilled in the art unrelated to the charge on the energy storage element 106. For instance, one condition may be the proper coupling of an input power source at a proper power level to the input of the regulating circuit 102. [0018] The enabling circuit 104 accepts a feedback signal from the regulating circuit 102 along path 119. Such feedback signal is representative of the charge on the energy storage element 106. The enabling circuit compares the charge on energy storage element 106 with a reference charge and may output an enabling signal if the charge level is less than the reference charge level. The enabling circuit 104 may also include various discharging means as further described in reference to FIG. 2 in order to discharge the energy storage element 106 below the reference charge level should the charge be greater than the reference charge level. Continue reading... Full patent description for Enabling circuit for avoiding negative voltage transients Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Enabling circuit for avoiding negative voltage transients 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. Each week you receive an email with patent applications related to your keywords. Start now! - Receive info on patent apps like Enabling circuit for avoiding negative voltage transients or other areas of interest. ### Previous Patent Application: Circuits and techniques for capacitor charging circuits Next Patent Application: Multiple output power supply that configures itself to multiple loads Industry Class: Electric power conversion systems ### FreshPatents.com Support Thank you for viewing the Enabling circuit for avoiding negative voltage transients patent info. IP-related news and info Results in 0.14468 seconds Other interesting Feshpatents.com categories: Accenture , Agouron Pharmaceuticals , Amgen , AT&T , Bausch & Lomb , Callaway Golf |
||
