Patent Application
20050073866
This invention relates to boost converters, power supply apparatuses, electrical energy boost methods and electrical energy supply methods.
The sophistication and uses of electrical devices have increased dramatically in recent years. Consumer items having electrical components are ubiquitous in communications, computing, entertainment, etc. The size of mobile telephones, notebook computers, music players, and other devices has continued to decrease while the capabilities and quality of the devices continues to increase as modern electronic components used in such devices are developed and improved upon.
Numerous people rely upon or have grown accustomed to usage of electrical consumer devices for business, education, or for other needs. Electronic consumer devices are increasingly portable to accommodate these needs during travels from home or the workplace. The sophistication and capabilities of power supplies for such devices have also improved to meet the requirements of the electronic consumer devices. For example, cost, size, and capacity are some product characteristics which have been improved for the portable power supplies for electronic applications.
There is a desire to enhance these and other design parameters of power supplies, including portable power supplies, to accommodate increasing power requirements of modern electronic consumer devices. Some power supplies utilize boost circuitry to increase the voltage of electrical energy stored using batteries of the power supplies. Some boost circuits are largely inefficient, perhaps providing losses of 40% or more during boost operations. At least some aspects of the disclosure provide improved methods and apparatus for supplying electrical energy.
Preferred embodiments of the invention are described below with reference to the following accompanying drawings.
This disclosure of the invention is submitted in furtherance of the constitutional purposes of the U.S. Patent Laws “to promote the progress of science and useful arts” (Article 1, Section 8).
According to one embodiment, a boost converter comprises an input configured to receive direct current electrical energy at a first voltage, an output configured to output direct current electrical energy at a second voltage higher than the first voltage, a plurality of switching devices coupled in series intermediate a positive terminal of the output and a ground, wherein one of the switching devices comprises a high side switching device coupled with the positive terminal and the other of the switching devices comprises a low side switching device coupled with the ground, drive circuitry configured to output a common control signal to control switching of the plurality of switching devices, a capacitor configured to capacitively couple the common control signal from the drive circuitry to the high side switching device, and wherein the control signal is configured to control the switching of the switching devices to boost the voltage of the received electrical energy of the first voltage to the second voltage.
According to another embodiment, a power supply apparatus comprises a first coupling configured to couple with a supply and to receive electrical energy from the supply to charge electrochemical storage circuitry, a second coupling configured to couple with a load, a boost converter comprising a plurality of switching devices controlled by a common control signal to implement regulation of direct current electrical energy of a first voltage from the electrochemical storage circuitry to a second voltage greater than the first voltage, and wherein the second coupling is configured to provide the direct current electrical energy of the second voltage to the load.
According to yet another embodiment, a power supply apparatus comprises electrochemical storage means for providing direct current electrical energy at a first voltage, first interface means for coupling with a supply and for receiving electrical energy from the supply for use in charging the electrochemical storage means, boost converter means for regulating the direct current electrical energy from the electrochemical storage circuitry to a second voltage greater than the first voltage, wherein the boost converter comprises synchronous field effect transistor means for increasing the voltage of the direct current electrical energy from the first voltage to the second voltage, and second interface means for coupling with a load and for providing the direct current electrical energy of the second voltage to a load.
According to an additional embodiment, an electrical energy boost method comprises providing direct current electrical energy at a first voltage, first conducting the electrical energy of the first voltage using an inductor, second conducting a first portion of the first conducted electrical energy using a first switching device, third conducting a second portion of the first conducted electrical energy using a second switching device, and wherein only one of the second conducting and the third conducting substantially occurs at a given moment in time to boost the voltage of the direct current electrical energy to a second voltage greater than the first voltage.
According to still another embodiment, an electrical energy supply method comprises storing direct current electrical energy using an electrochemical storage device, providing the stored electrical energy at a first voltage, inductively coupling the provided electrical energy to a plurality of switching devices, controlling the switching devices to operate according to a break-before-make mode of operation to increase a voltage of the provided direct current electrical energy to a second voltage greater than the first voltage, and using an output, outputting the direct current electrical energy at the second voltage to a load.
Referring to
In exemplary applications, power supply apparatus 10 is arranged as a portable device configured to provide portable electrical energy to portable loads or devices. Exemplary high-power loads include notebook computers and exemplary low-power loads include personal digital assistants (PDAs), mobile telephones, etc. Power supply apparatus 10 may be utilized to provide electrical power to other devices or may be configured in other arrangements to power devices of other wattage ratings. The particular arrangement of power supply apparatus 10 may be modified and tailored to accommodate the energy requirements of the utilized load(s). Power supply apparatus 10 may be utilized to provide electrical energy to one load (e.g., one high-power load or low-power load) at a given moment in time, or simultaneously provide electrical energy to one or more high-power load or one or more low-power load. Other arrangements besides portable energy applications including permanent arrangements or semi-permanent arrangements for providing electrical energy may also be implemented.
The illustrated exemplary power supply apparatus 10 includes a housing 12 configured to house electrical energy storage circuitry (exemplary storage circuitry is shown in
The depicted power supply apparatus 10 further includes a first connector 16 and a second connector 18. First connector 16 and second connector 18 are configured to couple with external devices or loads and to supply electrical energy to loads coupled therewith and\or receive electrical energy from a supply coupled therewith. Connectors 16, 18 have appropriate receptacle(s) to accommodate cables or other couplings utilized for coupling with the respective individual loads and\or supply. In the depicted exemplary arrangement, first connector 16 includes a receptacle 20 configured to receive a cable or other connection to couple with an external supply (not shown) and a second receptacle 22 configured to receive a cable or other connection for coupling with a load. Connector 18 includes a receptacle 24 which is configured to couple with a load in the illustrated configuration.
An appropriate supply (shown in
As mentioned previously, power supply apparatus 10 is arranged to supply electrical power to loads of different configurations and having different energy ratings or requirements for proper operation. For example, a first load may require or utilize electrical energy of a first voltage while another appropriate load may utilize electrical energy of a second voltage. In the described exemplary configuration, first connector 16 is a high-power connection and second connector 18 is a low-power connection.
A plurality of possible connectors 16, 18 are available to provide appropriate connection of power supply apparatus 10 with respective loads. Once a load is identified, the appropriate connector corresponding thereto is selected by the user and utilized to couple apparatus 10 with the load and\or supply. Connectors 16, 18 are configured to provide appropriate electrical energy to corresponding load devices and also configure power supply apparatus 10 as described further below.
Referring to
Storage circuitry 30 includes one or more electrochemical device 32 in exemplary embodiments. In the illustrated arrangement of
A particular configuration of power supply apparatus 10 may be dictated by an application in which it will be used to supply electrical energy. Electrochemical devices 32 implemented as lithium cells individually having a lithium-mixed metal electrode are individually configured in at least one arrangement to provide a voltage of approximately 3.7 Volts in a substantially charged state or condition. In the depicted exemplary arrangement, four electrochemical devices 32 are coupled in series to provide electrical energy to an appropriate load. In such a configuration, electrical energy is provided at a variable voltage range of 8 to 14.8 Volts from storage circuitry 30 with a nominal voltage of 10-13.2 Volts during typical operations.
In another possible embodiment, two banks of devices 32 are coupled in parallel to provide the electrical energy. Individual banks may include four such electrochemical devices 32 arranged in series. In an exemplary configuration comprising four series arranged electrochemical devices 32, power supply apparatus 10 may be utilized in 60 watt applications. In the configuration including eight electrochemical devices 32, power supply apparatus 10 may be utilized to provide electrical energy in 130 watt applications. Other configurations of power supply apparatus 10 including more or less cells arranged in series and\or parallel are contemplated and may be utilized in other energy applications having other energy current, voltage or wattage specifications.
Power supply apparatus 10 additionally includes circuitry 34 configured to control and monitor operations of apparatus 10. For example, circuitry 34 controls and implements charging, maintenance, and discharging of electrochemical devices 32 as well as conditioning of electrical energy extracted from electrochemical devices 32.
Exemplary circuitry 34 includes a first interface 36 and a second interface 38. First and second interfaces 36, 38 are individually configured to electrically couple with a respective one of first connector 16 and second connector 18. In the depicted exemplary embodiment, first and second interfaces 36, 38 comprise a plurality of electrical connection pins configured to mate with respective electrical connections such as receptacles (not shown) of connectors 16, 18. Connectors 16, 18 and interfaces 36, 38 are configured for removable electrical coupling enabling different configurations of first and second connectors 16, 18 to be utilized with the power supply apparatus 10 and corresponding to the loads and supplies to be coupled with apparatus 10. Further details regarding exemplary operations and one possible arrangement of circuitry 34 and apparatus 10 are discussed in a co-pending patent application having patent application Ser. No. 10/072,827, filed Feb. 8, 2002, entitled “Power Supply Apparatuses and Methods of Supplying Electrical Energy,” listing Lawrence Stone and John Cummings as inventors, the teachings of which are incorporated by reference herein.
Referring to
In accordance with one exemplary embodiment, circuitry 34 includes storage circuitry 30, first interface 36, second interface 38, a boost converter 40, charge circuitry 42, switch device circuitry 44, a capacity monitor 46, and a step-down converter 48. Components intermediate switch device circuitry 44 and first interface 36 may be referred to as high-power circuitry 50 and components intermediate switch device circuitry 44 and second interface 38 may be referred to as low-power circuitry 52.
As shown in
Interfaces 36, 38 are coupled with and provide electrical energy from storage circuitry 30 to respective loads 61, 65 using respective connectors 16, 18. In addition, first interface 36 is arranged in the exemplary embodiment to receive electrical energy from supply 60 coupled with connector 16. Further, interfaces 36, 38 may be arranged to receive control signals from connectors 16, 18 which control operations of circuitry 34 (e.g., voltage conversion operations).
Supply 60 and storage circuitry 30 provide electrical energy for usage within high-power load 61 and/or low-power load 65. Referring to operations of circuitry 50, one or both of supply 60 and high-power load 61 may be coupled with connector 16 at any given time.
Boost converter 40 is coupled intermediate storage circuitry 30 and first interface 36. Boost converter 40 is configured to receive direct current (DC) electrical energy from storage circuitry 30 and to provide direct current electrical energy having an increased voltage. According to an exemplary embodiment wherein storage circuitry 30 includes four series coupled lithium cell electrochemical devices 32, electrical energy having a nominal voltage of 10-13.2 Volts is provided and received by boost converter 40. Exemplary high-power loads (e.g., notebook computers) utilize electrical energy at a voltage of approximately 19.4 Volts. Boost converter 40 in one exemplary configuration increases the voltage of electrical energy received from storage circuitry 30 (e.g., 10 Volts) to electrical energy having an increased voltage (e.g., 19.4 Volts). In one configuration, boost converter 40 comprises synchronous circuitry. Additional details regarding an exemplary boost converter 40 are described below with respect to
Charge circuitry 42 is configured to control and implement charging and conditioning operations of storage circuitry 30. Charge circuitry 42 is coupled intermediate first interface 36 and storage circuitry 30 including one or more electrochemical device 32. In an exemplary configuration, charge circuitry 42 is implemented as a current sense circuit having product designation LT1621 available from Linear Technology Corporation and a battery charger having product designation LTC1735 available from Linear Technology Corporation.
Charge circuitry 42 is configured to monitor a quantity of electrical energy supplied from supply 60 to high-power load 61. Responsive to such monitoring, charge circuitry 42 controls a supply of electrical energy from supply 60 to storage circuitry 30 to charge one or more electrochemical device 32. Charge circuitry 42 is arranged in the described configuration to assure that load 61 receives adequate electrical energy for proper operation.
Capacity monitor 46 is configured to monitor a state of charge of electrochemical devices 32 of storage circuitry 30. Capacity monitor 46 is coupled with switch device circuitry 44 and is configured to control such switch device circuitry 44 responsive to the monitoring. In one embodiment, switch device circuitry 44 includes a charge field effect transistor (FET) and a discharge field effect transistor which are controlled to implement charging, discharging and maintenance operations. In one arrangement, capacity monitor 46 is implemented using product designation BQ2060, available from Texas Instruments Incorporated.
As illustrated in
Step-down converter 48 is arranged to receive electrical energy from electrochemical device 32, to decrease a voltage of the electrical energy received from electrochemical device 32, and to provide the electrical energy of the decreased voltage to second interface 38 for application to load 65 coupled therewith. Connector 18 controls the outputted voltage of converter 48 in the described embodiment.
In the described arrangement, circuitry 34 is arranged to apply electrical energy from supply 60 to storage circuitry 30 to charge and\or maintain electrochemical devices 32 and to apply electrical energy from storage circuitry 30 to first interface 36 and\or second interface 38 for application to respective present loads 61, 65. Converters 40, 48 are configured to receive electrical energy which may have a variable voltage from storage circuitry 30 and to provide regulated electrical energy of a substantial constant voltage for application to respective loads 61, 65.
Although converter 40 is configured as a boost converter and converter 48 is configured as a step-down converter in the described exemplary embodiment, the converters 40, 48 may be individually configured to implement other conditioning operations corresponding to the respective loads 61, 65. For example, converter 40 may be arranged to reduce the voltage of received electrical energy and converter 48 may be arranged to increase the voltage of received electrical energy in other exemplary embodiments.
Referring to
Vcharge may correspond to input direct current electrical energy from storage circuitry 30 and Vout corresponds to output direct current electrical energy applied to first interface 36. The voltage of the received electrical energy corresponds to the configuration and state of charge of storage circuitry 30 and may have a nominal voltage of 10-13.2 Volts while the output electrical energy is regulated to a constant output voltage of approximately 19.4 Volts in the exemplary arrangement. Other voltages may be used in other embodiments.
Blocking diode 56 may be utilized to accommodate different gate charges for the first and the second switching devices 58, 60 and the different rates of switching of devices 58, 60. In one embodiment, blocking diode 56 is implemented as a Schottky diode.
First switching device 58 may comprise a high side field effect transistor (FET) implemented as a P-Channel device. In the described embodiment, the first switching device 58 may comprise a synchronous device, such as a synchronous FET or synchronous rectifier. Second switching device 60 may comprise a low side field FET implemented as an N-Channel device in the exemplary embodiment. Switching devices 58, 60 are coupled in series intermediate a positive terminal of the output 53 and a ground as shown in
Drive circuitry 62 comprises a gate drive integrated circuit configured to control the operation of switching devices 58, 60 to implement boost operations in one implementation. In the illustrated embodiment, drive circuitry 62 outputs a common control signal comprising a square wave of 0-5 Volts at a frequency of 600 kHz which controls both of the switching devices 58, 60 (i.e., the gate drive of first switching device 58 is derived from the gate drive for the second switching device 60) to boost the voltage of the direct current electrical energy received via input 51.
In one embodiment, boost converter 40 is arranged such that only one of first switching device 58 having a negative threshold voltage and second switching device 60 having a positive threshold voltage are substantially enabled at a given time. This avoids simultaneous engagement of both switching devices 58, 60 which would short the output voltage and disable the ability of boost converter 40 to regulate the output voltage.
In the disclosed embodiment, voltage translation capacitor 63 operates to ensure only one of switching devices 58, 60 is substantially engaged at any given time. In the exemplary embodiment of
During a negative pulse from drive circuitry 62, switching device 58 is inherently OFF inasmuch as the voltage of the gate of switching device 58 is substantially pulled up to the voltage of the source (i.e., the output voltage). When a positive pulse is provided by drive circuitry 62, translation capacitor 63 causes the gate of switching device 58 to rise by an equal amount (e.g., 5 Volts). However, the actual voltage rise is limited by diode 56 and a capacitive divider 59 comprising capacitors 63, 66.
When the voltage on the gate of switching device 60 is driven to 0 Volts (i.e., the charge pulled off of the gate), the translation capacitor 63 causes the voltage at the gate of switching device 58 to fall. The resultant voltage at the gate of switching device 58 is a function of the capacitive divider 59.
In the disclosed embodiment, switching device 58 comprises a P-Channel FET configured to facilitate break-before-make operation with respect to switching device 60 wherein the P-Channel FET is easier to turn on and off compared with switching device 60. For example, in the depicted embodiment, device 58 uses less gate charge compared with device 60 and the current is flowing in the direction of the body diode providing zero-voltage switching of device 58. In the exemplary break-before-make configuration, switching device 58 is substantially OFF before switching device 60 is substantially ON. As the switching device 58 turns off, current is automatically shunted through the external blocking diode 56.
Referring to the operation of switching device 60, when device 60 is OFF there is a voltage Vds across the drain and source which is nominally the regulation voltage of the converter 40. When sufficient gate charge is applied to turn device 60 ON, the device begins to conduct and the voltage Vds falls. As the voltage Vds falls below Vgs, a parasitic Miller capacitor of second switching device 60 creates a brief delay in the turn on switching because the falling Vds pulls charge off of the gate via the Miller capacitor. This delay provides sufficient time for first switching device 58 to be completely OFF before engagement of switching device 60 providing break-before-make operation.
Further protection of simultaneous engagement of devices 58, 60 is provided by first switching device 58 having a lower gate charge than second switching device 60 and/or switching device 58 configured to implement zero voltage switching in one embodiment. Accordingly, switching speed of first switching device 58 is inherently faster than the switching speed of second switching device 60 in at least one embodiment.
In addition, capacitor 66 may be selected to have a sufficient capacitance to swamp out or over-ride switching effects of the parasitic Miller capacitor of first switching device 58 arranged as a FET in a zero-voltage switching arrangement in combination with diode 56. For example, capacitor 66 having capacitance 0.01 μF is sufficient in the embodiment of
Diode 68 is configured to ensure that the gate of first switching device 58 does not go to more than a diode drop higher than Vout. This allows for the gate of the first switching device 58 in the disclosed embodiment to fall as much as 2.5 Volts when the second switching device 60 is disabled and assuming capacitors 63, 66 are sufficiently matched and there was a 5 Volt gate drive removed from the second switching device 60.
Accordingly, the described exemplary configuration of the boost converter 40 provides break-before-make operations during first switching device 58 going from ON to OFF states and second switching device 60 going from OFF to ON states. In the described configuration, a self-protect operation is further provided wherein first switching device 58 is turned OFF if node 69 joining first and second switching devices 58, 60 falls below Vout. This self-protect operation results from the fact that pull-up current of the gate of first switching device 58 comes from the source of device 58. Further, break-before-make operations are implemented during device 60 turning OFF and device 58 turning ON. For example, device 60 becomes sufficiently resistive before a channel adequately forms within device 58 and current is initially momentarily directed through diode 56 providing the break-before-make operation.
The described exemplary boost converter 40 provides negligible switching losses inasmuch as the first switching device 58 comprising a synchronous FET is effectively a zero-voltage switched device and therefore not subject to the switching losses caused by the parasitic Miller capacitor of device 58 implemented as a FET in but one arrangement. The disclosed exemplary boost converter 40 has provided real world testing to deliver 90 W of power at more than 93% conversion efficiency. At more reasonable and typical loads of 45-60 W, the efficiency is in excess of 94%.
Exemplary circuit components of the boost circuitry 40 of
Referring to
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In compliance with the statute, the invention has been described in language more or less specific as to structural and methodical features. It is to be understood, however, that the invention is not limited to the specific features shown and described, since the means herein disclosed comprise preferred forms of putting the invention into effect. The invention is, therefore, claimed in any of its forms or modifications within the proper scope of the appended claims appropriately interpreted in accordance with the doctrine of equivalents.
