Source: http://www.google.com/patents/US7391188?ie=ISO-8859-1&dq=7222078
Timestamp: 2014-08-31 07:41:13
Document Index: 88070341

Matched Legal Cases: ['application No. 60', 'application No. 60', 'application No. 60', 'application No. 60', 'application No. 60', 'application No. 60']

Patent US7391188 - Current prediction in a switching power supply - Google PatentsSearch Images Maps Play YouTube News Gmail Drive More »Sign in<nobr>Advanced Patent Search</nobr>PatentsA high efficiency switching power supply including an analog front end, a battery control circuitry portion, a display and equalization circuitry portion, field effect transistor (FET) drivers, an isolated power supply transformer circuitry (and three associated sets of tap circuitry), microcontroller...http://www.google.com/patents/US7391188?utm_source=gb-gplus-sharePatent US7391188 - Current prediction in a switching power supplyAdvanced Patent SearchPublication numberUS7391188 B2Publication typeGrantApplication numberUS 11/193,635Publication dateJun 24, 2008Filing dateAug 1, 2005Priority dateAug 2, 2004Fee statusPaidAlso published asUS20060119331Publication number11193635, 193635, US 7391188 B2, US 7391188B2, US-B2-7391188, US7391188 B2, US7391188B2InventorsJames K. Jacobs, Sankar Dasgupta, David VandermeerOriginal AssigneeJacobs James K, Sankar Dasgupta, David VandermeerExport CitationBiBTeX, EndNote, RefManPatent Citations (19), Referenced by (1), Classifications (18), Legal Events (2) External Links: USPTO, USPTO Assignment, EspacenetCurrent prediction in a switching power supplyUS 7391188 B2Abstract A high efficiency switching power supply including an analog front end, a battery control circuitry portion, a display and equalization circuitry portion, field effect transistor (FET) drivers, an isolated power supply transformer circuitry (and three associated sets of tap circuitry), microcontroller circuitry, oscillator circuitry, overcharge protection circuitry, programmable logic circuitry portion, and a zero current predictor. Overbiasing of the FET power supply switches, and/or other various circuitry features disclosed herein, helps achieve electrical power efficiencies of preferably greater than 95%, even more preferably greater than 98% and even more preferably greater than 99%. Preferably, the switching power supply has one or more of the following: (1) high electrical power efficiency (>95%. >98%, >99%); (2) overbiasing of a gate of a power supply switch; (3) a power supply switch with a low gate capacitance ratio; (4) multiple modes of operation; and (5) current prediction wherein an inductor voltage is used to control a constant current capacitor whose voltage indicates the level of current in the inductor.
RELATED APPLICATION DATA This application claims any and all applicable benefits based on the following provisional patent application(s): (1) U.S. patent application No. 60/592,386 filed on 2 Aug. 2004; (1) U.S. patent application No. 60/656,911 filed on 1 Mar. 2005; (2) U.S. patent application No. 60/656,889 filed on 1 Mar. 2005; (3) U.S. patent application No. 60/656,913 filed on 1 Mar. 2005; (4) U.S. patent application No. 60/657,417 filed on 2 Mar. 2005; and (5) U.S. patent application No. 60/656,914 filed on 1 Mar. 2005. All of the foregoing patent-related documents are herein incorporated by reference.
FIELD OF THE INVENTION The present invention relates to power supplies and more particularly to high efficiency dc-dc converter switching power supplies.
DESCRIPTION OF THE RELATED ART Power supplies and switching power supplies are well known and conventional. A switching power supply generally includes: (1) an input power signal (see DEFINITIONS section for definition of �power signal�); (2) a power supply switch set; (3) a passive component set; (4) a controller; and (5) an output power signal.
U.S. published patent application publication number 2002/0017897 (�Wilcox�) discloses a switching voltage regulator which is alleged to exhibit high efficiency over broad current ranges, including low output currents. Wilcox further states that its disclosed control circuit can facilitate over 90% efficiency in a 5-volt synchronous switching regulator for an input voltage of approximately 10 volts. Wilcox further states that efficiencies of over 95% can be maintained. The Wilcox switching regulator generates a control signal to turn switching resistors off when voltage at the output can be effectively maintained at the regulated voltage by the charge on an output capacitor.
U.S. Pat. No. 4,495,554 (�Simi�) discloses a switching power supply wherein the input elements, including the controller, are fully isolated by a transformer. Simi explains the way in which its switching power supply uses, the technique of overbiasing: �Thus, during each period in which controller 51 gates FET 9 on, transistor 19 is driven on. Transistor 19 is overbiased and can conduct any amount of current which might be provided by line 33. During the other periods, transistor 19 is positively driven off. Diode 20 is then forward biased and provides a shunt to ground which protects transistor 19. As transistor 19 is turned on, current flows through the primary of transformer 35, bypassing diode 37 and resistor 39 since transistor 19 constitutes a direct path to the ground reference potential.�
U.S. Pat. No. 6,348,784 (�Gofman�) discloses a switching power supply including a series regulator circuit. The regulator circuit includes a MOSFET that operates with voltage biasing circuitry. The voltage biasing circuitry offsets a voltage level between the gate and drain terminals to reduce the difference in voltage between the drain and the source terminals associated with the gate-to-source threshold voltage. This biasing thereby reduces the power dissipated within the series regulator element.
U.S. published patent application publication number 2004/0119448 (�Wiegand�) discloses a controller apparatus that varies the amplitude of an electrical power supply voltage. Wiegand states: �The controller apparatus . . . may be used to implement all otherwise conventional converter types, buck, boost, and inverting (and duals of these) version to obtain different regulating characteristics . . . �
U.S. published patent application publication number 2004/0100807 (�MacDonald�) discloses a dual input AC/DC power converter with dual programmable DC voltage outputs. The power converter includes an AC-to-DC converter, a DC-to-DC booster converter, and a DC-to-DC buck converter. The two programmable DC output voltages may be generated as a function of both AC and DC input voltages.
U.S. published patent application 2003/0214271 (�Bradley�) discloses a system for bi-directional power conversion in a portable device with a battery, particularly wireless communications devices. Bradley states: �The invention . . . us[es] a single inductor to perform both buck and boost power conversion operations . . . thereby reducing the number of components . . . �
U.S. Pat. No. 6,377,032 (�Andruzzi�) discloses an apparatus for virtual current sensing in a DC-DC switched mode power supply. A programmable current source charges a current sensing capacitor and the voltage across the capacitor simulates the rising slope of the voltage across a conventional current sensing resistor. A ramp capacitor is charged by a second programmable current source. The sum of the voltages across the capacitors is used to discharge the current sensing capacitor to simulate the falling slope of current across a conventional resistor.
U.S. Pat. 5,982,160 (�Walters�) discloses a DC-DC converter that provides sensing of the output current for regulation. The DC-DC converter includes a power switch, an output inductor connected across the power switch and a current sensor connected in parallel with the inductor. The current sensor includes a resistor and a capacitor, preferably with fast values.
SUMMARY OF THE INVENTION The present invention relates to switching power supplies and circuitry portions of switching power supplies. Preferably, the switching power supply has one or more of the following: (1) high electrical power efficiency (>95%. >98%, >99%); (2) overbiasing of a gate of a power supply switch; (3) a power supply switch with a low gate capacitance ratio; (4) multiple modes of operation; and (5) current prediction wherein an inductor voltage is used to control a constant current capacitor whose voltage indicates the level of current in the inductor.
BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 a is an analog front end first portion of a first embodiment of a switching power supply;
DETAILED DESCRIPTION OF SOME EMBODIMENTS The following exemplary embodiment(s) of a switching power supply will be given in the context of a switching power supply used in a battery device. More particularly, the battery device (not separately shown in the Figs.) includes the switching power supply and rechargeable electrochemical cells (preferably lithium ion or lithium polymer cells) in a housing. One or more jacks at an external surface of the housing allow external devices to be electrically connected and disconnected from the switching power supply. Because it is electrically interposed between the external device(s) and the electrochemical cells, the switching power supply here controls the charging and discharging of the electrochemical cells. Specifically, an external power source can be connected via a jack to recharge the electrochemical cells when they have been drained of charge. Alternatively (or additionally) an external load can be connected. This external load can then be powered by the electrochemical cells via the switching power supply. In some preferred embodiments of the present invention, only one jack is provided, and this jack is used both to charge and discharge the electrochemical cells.
Referring to FIG. 3 a, battery control first portion 225 includes input 249; outputs 233, 234, 236, 250; ground (digital or analog, as appropriate) 243; resistor 251; capacitor 231; DC jack terminals 227, 247; and input overvoltage protection circuit 229; and Metal Oxide Semiconductor Field Effect Transistor (�MOSFET�) 245. The circuit elements of the battery control first portion are electrically interconnected as shown in FIG. 3 a. Preferred electrical characteristics for some of the components of the first battery control portion are now set forth in parentheses after each element: input 249 (Overcharge); output 233 (Charge Supply); output 234 (input 244); output 236 (input 246); output 250 (Jack Sense); and resistor 251 (1M0).
MOSFETS 235, 269 are preferably constructed as Model Si4835DY from Vishay Siliconix. MOSFETS 239, 279 are preferably constructed as Model Si4886DY from Vishay Siliconix. Inductors 253, 255 are preferably each 3.2 microhenry inductors with a saturation current of at least 8.6 amperes (A) at 25 degrees Celsius (C). Of course, the combined inductance of these inductors connected in series is 6.4 microhenry. Alternatively, one larger inductor could be used here, but it is generally easier to obtain two small inductors rated at this high level of saturation current. Precision voltage dividers 259, 265 (or resistor networks) are preferably constructed as Model MPM2001/1002A from Vishay Thin Film of Shelton, Connecticut. In power supply 50, these MOSFETS 235, 239, 269, 279 are the power supply switches. In other power supply embodiments, other types of FETs, or other types of transistors, or even entirely different types of semiconductor devices, may be used for the power supply switches. Power supply switches are sometimes herein referred to as �power supply switch FETs.�
Preferred switching power supplies according to the present invention have electrical power efficiencies (e.g., at 25 watt, full power) of upwards of 95%, 98% or even 99%. Some of the features that result in the very high efficiencies of the present invention are related to the driving of the power supply switches, in this embodiment MOSFETs 235, 239, 269, 279. Some inefficiencies in switching power supplies include: (1) gate charge of MOSFETS (active component set, frequency sensitive); (2) resistance drain to source (�RDS�, active component set); (3) resistance loss of inductor (dc loss, frequency sensitive, less loss at high frequency); (4) capacitive losses (frequency sensitive, ESR: effective series resistance); (5) shunt loss (smaller shunt is preferred, not frequency sensitive); and (6) frequency inductance.
Referring to FIG. 4, display and equalization first portion 300 includes inputs 322, 324, 330; outputs 306, 308, 310, 312; terminals 320, 350; ground (preferably digital) 304; resistors 314, 316, 318, 326, 332, 336, 340, 344, 348, 352, 354, 356, 358; light emitting diodes (LEDs) 328, 334, 338, 342, 346; and sixteen port processing circuit 302. The circuit elements of the display and equalization first portion are electrically interconnected as shown in FIG. 4. Preferred electrical characteristics for some of the elements of the display and equalization first portion are now set forth in parentheses after each element: input 322 (Serial Data Port B); input 324 (Serial Clock Port B); input 330 (LED 1); output 306 (Equalization 4); output 308 (Equalization 3); output 310 (Equalization 2); output 312 (Equalization 1); terminal 320 (+5.4 V); terminal 350 (+5.4 V); resistor 314 (100K); resistor 316 (100K); resistor 318 (100K); resistor 326 (100K); resistor 332 (1K0); resistor 336 (1K0); resistor 340 (1K0); resistor 344 (1K0); resistor 348 (1K0); resistor 352 (100K); resistor 354 (100K); resistor 356 (100K); resistor 358 (100K); LED 328 (Red); LED 334 (Yellow); LED 338 (Green); LED 342 (Green); LED 346 (Green); port 1 of circuit (or �ckt�) 302 (A0); port 2 of ckt 302 (A1); port 3 of ckt 302 (A2); port 4 of ckt 302 (LED0); port 5 of ckt 302 (LED1); port 6 of ckt 302 (LED2); port 7 of ckt 302 (LED3); port 8 of ckt 302 (GND); port 9 of ckt 302 (LED4); port 10 of ckt 302 (LED5); port 11 of ckt 302 (LED6); port 12 of ckt 302 (LED7); port 13 of ckt 302 (RESET); port 14 of ckt 302 (SCL); port 15 of ckt 302 (SDA); and port 16 of ckt 302 (VDD).
The zero current predictor is utilized to prevent reverse current flow. The current predictor works by sensing the voltage across an inductor and/or the rate of change of voltage across an inductor. This zero current predictor is believed to be especially advantageous in synchronous switching power supplies. This zero current prediction is different than power supply control methods for measuring the current in the inductor for the express for purpose of limiting the current peaks to prevent inductor saturation and FET damage, and to provide current regulation without the use of a current shunt. This is done in various manners all with the intent of knowing what the current is at a specific point in time. The zero current prediction approach is quite different in that respect. The zero current prediction approach does not necessarily make any effort to realize the absolute value of current. Rather, the zero current prediction method predicts when the current might be zero, for the purpose of improving efficiency. This is different than conventional devices that make efforts to actually measure the current, for both peak current control and reverse current prevention (occurs after current reaches zero.) One of the basic problems with this approach is, of course, it is very difficult to measure very small currents. The present invention avoids that by not measuring actual current but by �predicting when it �might� be zero. The approach has resulted in some significant improvements in efficacy. This kind of zero current predictor can prevent inductor from getting down to zero current as synchronous FETs are switching on and off. The rate of change of current in an inductor can be mimicked by the rate of change of voltage in a capacitor, which is the preferred way of performing zero current prediction according to the present invention.
Power signal: any electrical power flow caused primarily for the purpose of transferring electrical power, regardless of whether the �signal� includes any informational component (generally it will not) and regardless of whether some or all of the power is not transferred (for example, in some embodiments, some of the power will be used to run the switching power supply and therefore there will be some power from the power signal that is not transferred in these embodiments, even though electrical power transfer is still the primary purpose of the power signal.
To the extent that a patentee may act as its own lexicographer under applicable law, it is hereby further directed that all words appearing in the claims section, except for the above-defined words, shall take on their ordinary, plain, and accustomed meanings (as generally shown by documents such as dictionaries and/or technical lexicons), and shall not be considered to be specially defined in this specification. Notwithstanding this limitation on the inference of �special definitions,� the specification may be used to evidence the appropriate ordinary, plain and accustomed meanings (as generally shown by dictionaries and/or technical lexicons), in the situation where a word or term used in the claims has more than one alternative ordinary, plain and accustomed meaning and the specification is actually helpful in choosing between the alternatives.
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