CN101120618A

CN101120618A - A power supply

Info

Publication number: CN101120618A
Application number: CNA2006800039255A
Authority: CN
Inventors: T·史密斯; P·马尔斯
Original assignee: Cap XX Ltd
Current assignee: Cap XX Ltd
Priority date: 2005-02-02
Filing date: 2006-02-02
Publication date: 2008-02-06

Abstract

A power supply (1) for powering a load, the load being in the form of a flash driver circuit (4) for a digital camera (not shown). The power supply includes a supercapacitive device, in the form of a supercapacitor (8), for powering circuit (4). A regulator unit, in the form of an inductive regulator (10), charges supercapacitor (8).

Description

Power supply

Technical Field

The present application relates to a power supply, in particular for powering at least one load.

The invention has been developed primarily for use in portable electronic devices such as cellular telephones having an on-board digital camera with a flash light and will be described hereinafter with reference to this application. It will be appreciated that the invention is not limited to this particular field of application but is also applicable to other portable electronic devices such as PDAs, laptops, digital cameras, MP3 players, etc. or to other computing devices having multiple loads with corresponding peak power requirements at one or more nominal voltages, whether or not the devices are portable. The invention is also suitable for high-power devices such as hybrid electric vehicles and electric vehicles.

Background

Portable electronic devices contain an onboard power source for powering the electronic circuitry contained within the device. Typically, the power source is a secondary battery or a plurality of such batteries. The design of these portable devices is often particularly sensitive to the size of the device, the effective operating time required between having to recharge the battery, the functionality that can be provided, and the cost of the components required to construct the device. Typically, the trend is small size, longer run time, increased functionality, reduced cost. It will be appreciated that these trends are in opposition to each other. For example, one option for achieving longer run times is to include larger capacity batteries, which generally increase the size and cost of the device in order to provide a given function.

As technology is increasingly being converged upon in portable devices-that is, additional functions are being incorporated in a given device, along with the hardware and circuitry required to provide those functions-there is a need for higher battery load currents, particularly for higher battery peak load currents. This typically occurs because the battery must simultaneously supply current to the discrete circuits that provide the respective functions. In an effort to resolve such contradictions, an incomplete solution has been found that involves only allowing mutually exclusive use of different functions. Nevertheless, the peak load current is often still too high, and the running time of the device is still greatly affected by the standby current drawn by the circuits not currently in use. This is particularly problematic for devices that provide cellular telephones.

Previous efforts to reduce peak battery current have included placing an ultracapacitor in parallel with the battery, or employing some current limiting circuit between the battery and the ultracapacitor to limit inrush current to the discharged ultracapacitor. In this case, the super capacitor is on the input to the LED flash driver, especially if one of the loads being powered is a high current LED flash. This results in LED flash drivers that must support very high currents and make implementations impractical in small portable applications such as cellular phones.

Any discussion of the prior art throughout the specification should in no way be considered as an admission that such prior art is widely known or forms part of common general knowledge in the field.

Disclosure of Invention

It is an object of the present invention to overcome or ameliorate at least one of the disadvantages of the prior art, or to provide a useful alternative.

The term "supercapacitive device" as used in this specification is intended to include energy storage devices commonly referred to as "supercapacitors". Supercapacitive devices store charge in an electric field and typically have a high capacitance and a high power density. It will be understood that "supercapacitor" is also denoted by the terms "super capacitor", "electric double layer capacitor", "electrochemical capacitor", etc., among others, all of which are included in the term "supercapacitive device" as used in this specification. One subset of supercapacitive devices are so-called "hybrid devices" which contain supercapacitive elements in combination with fuel cell elements or battery elements. For example, hybrid supercapacitors/batteries typically comprise a package that includes components for storing energy in one or more electric fields and in one or more electrochemical cells. In some cases, a supercapacitive device includes multiple supercapacitive cells connected in series or in parallel or in a combination of series and parallel. Indeed, for purposes of this specification, a supercapacitive device is intended to include any reasonable combination of supercapacitors and other components that produce a net supercapacitive effect. Such "multi-cell" supercapacitive devices often contain other elements for balancing the voltages obtained across the respective cells. These other elements include active and/or passive electronic components.

According to a first aspect of the present invention, there is provided a power supply for supplying power to at least one load, the power supply comprising:

a super-capacitive device for powering the at least one load; and

a regulator unit for charging the super-capacitive device.

Preferably, the regulator unit limits the charging current of the supercapacitor to a first predetermined value. It is further preferred that the predetermined value is less than about 2 amps. More preferably, the predetermined value is less than about 1 amp. Even more preferably, the predetermined value is less than about 100mA. However, in other embodiments, the predetermined value is a value other than about 2 amps.

Preferably, the power supply unit limits the current of the battery to a second predetermined value. More preferably, the predetermined value is less than about 2 amps. However, in other embodiments, the predetermined value is a value other than about 2 amps.

Preferably, the regulator unit comprises a voltage regulator. More preferably, the voltage regulator is a voltage booster. However, in other embodiments, the voltage regulator is a buck regulator, such as a linear regulator or a buck (buck) regulator.

Preferably, the power supply includes an input for selectively connecting the regulator to the power source. It is also preferred that the input isolates the regulator from the power source when the super-capacitive device is powering the or each load. In certain embodiments, the supercapacitive device is connected in parallel with at least one load. It is also preferred that the regulator draws a charging current for the super-capacitive device from the power source limited to a predetermined value when the super-capacitive device powers the or each load. In certain embodiments, the supercapacitive device is connected in parallel with at least one load. More preferably, in these embodiments, the regulator is in series with the power source and together they are in parallel with the supercapacitive device. However, in an alternative embodiment, the super-capacitive device is in series with the power source. That is, in these alternative embodiments, the series combination of the super-capacitive device and the power source together are connected in parallel with the load. In yet another embodiment, the supercapacitive devices are selectively connected in parallel and in series with the power source.

In a preferred embodiment, the power supply draws a supply current from the power source, and the at least one load comprises two pulsating (pulsed) loads drawing respective load currents from the power supply, wherein the power supply suppresses the supply current to less than a predetermined threshold. Typically, the super-capacitive device enables the power supply to meet a pulsating load while the supply current remains less than the predetermined threshold.

More preferably, at least one of the load currents is controlled so as to suppress the power supply current to be less than a predetermined threshold value. However, in some embodiments, the super-capacitive device provides all or most of the load current and enables load currents well above a predetermined maximum current that can be supplied by the power source. In a preferred form, in the presence of more than one pulsating load, one of the loads has a high priority and the remaining loads have a low priority, wherein, to suppress the supply current, the regulator unit preferably controls the load current for loads having a lower priority. In other embodiments, the load current is controlled. In a further embodiment, the priority of the load varies over time or follows a configuration made by the user. It is also preferred that one of the loads is a cellular telephone transmitter circuit and the other of the loads is a flash lamp circuit. More preferably, the cellular telephone circuit has a high priority and the flash circuit has a low priority. Although both loads can operate simultaneously-although the loads will only mutually exclusively draw respective load currents-the supply current is suppressed by ensuring that the load current to the flash lamp circuit is controlled, or alternatively the load current to the flash lamp circuit is supplied by a super-capacitive device and the distribution of the supply current to the flash lamp circuit is controlled. The control of the load current to the flash circuit is responsive to the load current drawn by the cellular telephone circuit. That is, the load current to the flash circuit is reduced to substantially zero when the load current is drawn by the cellular telephone circuit. That is, the supply current is always kept below the predetermined threshold, and the low priority load current is reduced for situations where a high priority load requests a load current that may result in exceeding the threshold simultaneously with a low priority load. In some embodiments, the low priority load current is reduced to a fraction of the current provided in the absence of the high priority load current, while in other embodiments, the low priority load current is reduced to substantially zero. In other embodiments, the high priority loads may be powered directly from the power source, while the low priority loads are powered by the power source.

Preferably, the power supply comprises a regulator for powering at least one other load.

According to a second aspect of the present invention, there is provided a power supply comprising:

a regulator unit for powering a first load; and

a super-capacitive device, chargeable by the regulator unit, for powering the second load.

Preferably, charging the super-capacitive device and powering the second load are mutually exclusive. More preferably, the power supply is included in a cellular telephone that includes a communication module and a flash drive circuit that define the first and second loads, respectively.

Preferably, the power supply comprises an input for connection to a power source. In certain embodiments, the supercapacitive device is connected in parallel with at least one load. More preferably, in these embodiments, the regulator is in series with the power source and together they are in parallel with the supercapacitive device. However, in an alternative embodiment, the supercapacitive device is in series with the power source. That is, in an alternative embodiment, the series combination of the super-stage capacitive device and the power source together are in parallel with the load. In yet another embodiment, the super-capacitive devices are selectively connected in parallel and in series with the power source.

In some embodiments, the first and second loads are powered mutually exclusively. In other embodiments, the first and second loads are powered simultaneously. Preferably, the second load is a pulsating load.

Preferably, the power supply is selectively operable in a plurality of modes including:

a first mode in which the regulator unit supplies power to a first load;

a second mode in which the regulator unit charges the supercapacitive device; and

a third mode in which the supercapacitive device is discharged to power the second load.

Preferably, the super-capacitive device is isolated from the power source in the first mode. It is further preferred that the regulator unit does not supply a charging current to the supercapacitor in the third mode. It is further preferred that the first load is powered in the second and third modes. As such, the regulator unit ensures that the current drawn from the power source and supplied to the supercapacitive device in the second mode or the current drawn from the power source and supplied to the second load in the third mode is limited so that the power source can adequately power the first load. In some embodiments, the first load is isolated from the power source in the second and third modes.

Preferably, the regulator unit limits the charging current of the supercapacitor to a predetermined value. It is further preferred that the predetermined value is less than about 2 amps. More preferably, the predetermined value is less than about 1 amp. Even more preferably, the predetermined value is less than about 100mA.

In certain embodiments, the regulator unit is a voltage regulator. Preferably, the voltage regulator boosts a voltage supplied from the power source.

In certain embodiments, the regulator unit includes a voltage regulator and a bypass circuit. Preferably, the bypass circuit and the voltage regulator are used mutually exclusively. More preferably, the bypass circuit is used in the first mode and the voltage regulator is used in the second mode. It will be appreciated that the regulator unit may be isolated from the power source in the third mode, or the regulator unit may still supply a limited charging current to the super-capacitive device in the third mode.

According to a third aspect of the present invention, there is provided a power supply for supplying power to a plurality of loads, the power supply comprising:

an input for connection to a power source;

a first output for connection to a first load;

a second output for connection to a second load;

a super-capacitive device connected to at least one of the outputs for powering a respective load; and

a regulator unit connected to the input for charging the supercapacitive device.

Preferably, the first output limits the second output.

In some embodiments, the supercapacitive device is connected in parallel with the second load. More preferably, in these embodiments, the regulator is in series with the power source and together they are in parallel with the supercapacitive device. However, in an alternative embodiment, the supercapacitive device is in series with the input. That is, in these alternative embodiments, the series combination of the super-capacitive device and the power source together are connected in parallel with the load. In still further embodiments, the supercapacitive devices are selectively connected in parallel and in series with the power source.

Preferably, the regulator unit is selectively operable in a plurality of modes including:

a charging mode in which the regulator unit charges the supercapacitive device; and

a discharge mode in which the supercapacitive device is discharged to power the second load.

Preferably, the regulator cell is isolated from the supercapacitive device in the discharge mode.

In some embodiments, the first and second loads are mutually exclusively powered. In other embodiments, the first and second loads are powered simultaneously.

According to a fourth aspect of the present invention, there is provided a power supply for a plurality of loads drawing respective load currents, the power supply comprising:

an input for connection to a power source, the power source providing a predetermined maximum source current at a source voltage belonging to a predetermined range;

an output for selectively connecting to a load and providing an output voltage;

a super-capacitive device in parallel with the output; and

a control circuit arranged between the input and the output for controlling the output voltage such that the load current is provided while keeping the source current less than a predetermined value.

Preferably, at least one of the loads is a pulsating load. In other embodiments, one or more of the loads are pulsed loads that are switched between a standby mode and an operable mode in which the load current is relatively low and relatively high, respectively. More preferably, the ripple load has a duty cycle of less than about 50%. Even more preferably, for any given time interval, only one of the load currents is at or near its peak value, while the current drawn by any other load is at or near its inactive current level. That is, during any given load cycle, the average power drawn by all loads is less than the predetermined maximum source current multiplied by the source voltage.

More preferably, the supercapacitive device contributes to at least one of the load currents. In some embodiments, the supercapacitive device contributes to all load currents. In embodiments where at least one load is a pulsating load, the supercapacitive device preferably has sufficient capacity to supply full load current for one pulsating load cycle while receiving current from the source up to its predetermined value and maintaining sufficient voltage for the load to operate. It will be appreciated that in some embodiments, only one load current has a non-zero value for a given time interval. In this case, the capacity of the supercapacitive device only needs one cycle that is sufficient to supply the load that requires the most energy in the cycle.

It is further preferred that at least one load is connected to the output by a switch which travels between open and closed configurations for isolating and connecting the load from and to the output respectively. That is, when the switch is in the open configuration and the load is isolated from the output, wherein the load is not enabled, the load current of the load will be zero. Conversely, when the switch is in a closed configuration and the corresponding load is connected to the output, wherein the load is enabled, the load current of the load is not zero. In a preferred embodiment, the switch is responsive to the control circuit to travel between open and closed configurations. This allows the voltage presented to the load to be varied. If the voltage required to drive one load is too high for any other load, the latter is switched off in order to reduce the risk of damage to them. The switch is preferably a transistor, more preferably an FET.

In some embodiments, the supercapacitive device is always electrically connected to the output. However, in other embodiments, the supercapacitive device is selectively electrically disconnected from the output. More preferably, the supercapacitive device is selectively electrically disconnected from the output in response to the sum of the load currents being below a predetermined threshold for a predetermined period of time. This saves the supercapacitor leakage current and any supercapacitor balancing circuit current used in conjunction with a multi-cell supercapacitor drawing energy from the power source. Accordingly, for an electronic device having a power source including a secondary battery, the operating time of the device is increased.

Preferably, the load comprises respective operating voltages, and at least one of these operating voltages is different from all other operating voltages. That is, the load is at the operating voltage V ₁ ，V ₂ ，......V _N Draw down the corresponding load current I ₁ ，I ₂ ，......I _N Wherein N is not less than 2 and V ₁ ≠V ₂ ，......，V ₁ ≠V _N . More preferably, the control circuit is coupled to the outputThe voltage is controlled to selectively provide V on the output ₁ ，V ₂ ，......V _N 。

In a preferred mode, V ₁ ，V ₂ ，......V _N Is greater than the predetermined source voltage. More preferably, the control circuit comprises a regulator operable to selectively maintain the output voltage at V ₁ ， V ₂ ，......V _N Is greater than the at least one of the source voltage or about V ₁ ，V ₂ ，......V _N Greater than the at least one of the source voltages. Even more preferably, if the source voltage is greater than V ₁ ， V ₂ ，......V _N A selected one of which selectively bypasses and deactivates the regulator with the switch. In a preferred embodiment, the switch is a FET, while in other embodiments, alternative transistors are used. In some embodiments, the regulator is a boost circuit, while in other embodiments, the regulator is a buck-boost circuit. If a buck-boost circuit is used, a switch is not required to bypass the regulator if the source voltage is greater than the desired load voltage. This eliminates the switch and its associated control logic.

In a preferred embodiment, the predetermined source voltage varies with time. More preferably, the power source is an AC adapter, battery or battery pack for the portable electronic device and the load is the corresponding circuitry of the portable electronic device. It will be appreciated that the voltage supplied from the battery or battery pack varies considerably over time due to the discharge characteristics of the battery, the internal resistance of the battery, and any associated electronic protection circuitry used in the battery pack. The voltage provided by the AC adapter will also be different from the voltage provided by the battery or battery pack.

In other embodiments, the power source is a fuel cell or other portable energy storage device. In a further embodiment, the power source is a mains (mains) power source. More preferably, the power source is an adjustable power source.

According to a fifth embodiment of the present inventionFor drawing a corresponding load current I ₁ ， I ₂ ，......I _N Wherein N ≧ 2, the power supply includes:

an input for connection to a power source at a predetermined maximum source current I _S Supplying a source voltage V falling within a predetermined range _S ；

An output for selectively connecting to one or more loads for providing a predetermined load voltage V ₁ ，V ₂ ，......V _N Lower supply of load current I ₁ ，I ₂ ，......I _N Wherein V is ₁ ≠V ₂ ，......，V ₁ ≠V _N ；

A super-capacitive device in parallel with the output; and

a control circuit arranged between the input and the output for converting V ₁ ，V ₂ ，......V _N Is selectively applied to the output.

Preferably, V ₁ ，V ₂ ，......V _N One or more than one of V _S . More preferably, the load is selectively connected to the output as long as the load receives the voltage on the output. Accordingly, in some embodiments, loads are all mutually exclusively connected to the output, while in other embodiments more than one load is connected to the output at the same time.

According to a sixth aspect of the present invention, there is provided a power supply comprising:

an input for connection to a power source, the power source providing a source voltage within a predetermined range at a source current;

an output for connection to a load, the load drawing having a peak value (I) _LP ) Pulsed load current (I) _L1 )；

A control circuit arranged between the input and the output for supplying the output with a signal having a predetermined peak value (I) _OP ) Output current (I) of _O ) Wherein, in the step (A),I _OP ＜I _LP (ii) a And

a super-capacitive device connected in parallel with the output for providing a signal satisfying I _LP (I _OP +I _C ) Of (a) is measured _C )。

Typically, from I _LP ＝(I _OP +I _C ) To obtain I _OP ＜I _LP And I is _OP < predetermined maximum value. In some cases, during pulsed load discharge, I _OP ＝0。

Preferably, the output selectively draws a pulsating load current (I) _L2 ) Is connected to the other load and the supercapacitive device provides the condition of (I) _LP +I _L2 )≤(I _OP +I _C ) Capacitive current (I) of _C )。

According to a seventh aspect of the present invention, there is provided a power supply comprising:

an input for connection to a power source providing a source voltage belonging to a predetermined range;

an output for providing an output voltage and for connection to a load that draws a load current at the output voltage;

a super-capacitive device connected in parallel with the output; and

a control circuit arranged between the input and the output for travelling between first and second states in which the output voltage is substantially equal to the source voltage and a regulated form of the source voltage, respectively.

Preferably, in the first state, the source voltage is applied substantially directly to the output. More preferably, the control circuit comprises a switch between the input and the output which is closed and opened during the first state and the second state, respectively. In a preferred embodiment, the switch is a FET, while in other embodiments, an alternative switch is used.

It is further preferred that the control circuit includes a regulator which is selectively operable to maintain the output voltage at a predetermined value. More preferably, operation of the regulator is selected to occur simultaneously with the second state. In some embodiments, the output voltage is greater than the source voltage when the control circuit is in the second state. That is, the regulator is a boost converter. In other embodiments, the output voltage is lower or higher than the source voltage. That is, the regulator is a buck-boost regulator. In further embodiments, the output voltage is less than the source voltage and the regulator is a linear voltage regulator. In embodiments where the regulator is a buck-boost regulator, the regulator automatically handles the transition from the first to the second state. The regulator remains enabled and no bypass switch is required. This saves the bypass switch and associated control logic, albeit at the expense of a small efficiency penalty of having to use the buck-boost regulator during the first state.

According to an eighth aspect of the present invention, there is provided a power supply comprising:

a super-capacitive device that travels between first and second states in which the device is connected in parallel with an output and not connected in parallel with the output; and

a control circuit, disposed between the input and the output, for generating an output voltage in response to the source voltage, the circuit also causing the supercapacitive device to travel between the first state and the second state.

Preferably, the control circuit is responsive to one or more of the output voltage and the source voltage in order to cause the supercapacitive device to travel from one state to another. More preferably, the control circuit is responsive to both the source voltage and the output voltage for causing the supercapacitive device to travel from one state to the other. In other embodiments, the control circuit is responsive to the load current for causing the supercapacitive device to travel from one state to another.

According to a ninth aspect of the present invention, there is provided a power supply comprising:

an input for connection to a power source, the power source providing a source voltage that falls within a predetermined range;

an output for providing an output voltage selected from a voltage range including a source voltage, the output being connected to one or more loads;

a super-capacitive device connected in parallel with the output; and

a control circuit arranged between the input and the output and responsive to the source voltage for generating the output voltage and limiting the output current to a predetermined maximum value.

Preferably, the control circuit limits the output current to a predetermined maximum value even when the output voltage is less than the source voltage. More preferably, the control circuit includes: a regulator in the form of a boost converter having an inductor; a FET or other transistor in series with the boost converter; a diode in series with the transistor. This prevents high currents from flowing to the supercapacitive device until the output voltage is sufficiently high. That is, forward current conduction from the source to the supercapacitor via the inductor and diode of the boost converter cannot occur. This prevents excessive inrush currents when charging the supercapacitor and keeps the source current below a predetermined maximum.

According to a tenth aspect of the present invention, there is provided a method of powering a load from a power source, the method comprising the steps of:

electrically connecting a supercapacitor with a regulator unit between a power source and a load;

charging the super capacitor with a regulator unit; and

the super capacitor is discharged to power the load.

Preferably, the regulator unit comprises a voltage regulator. More preferably, the voltage regulator is a voltage booster. In some embodiments, the regulator unit is isolated from the power source when the super-capacitive device powers the or each load.

In certain embodiments, the supercapacitive device is connected in parallel with at least one load. More preferably, in these embodiments, the regulator is in series with the power source and together they are in parallel with the supercapacitive device. However, in an alternative embodiment, the super-capacitive device is in series with the power source. That is, in an alternative embodiment, the series combination of the super-capacitive device and the power source together are connected in parallel with the load. In yet a further embodiment, the super-capacitive device is selectively connected in parallel and in series with the power source.

According to an eleventh aspect of the present invention, there is provided a method for powering a first load and a second load, the method comprising:

powering a first load with a regulator unit; and

the second load is powered with a super-capacitive device that can be charged by the regulator unit.

According to a twelfth aspect of the present invention, there is provided a method for supplying power to a plurality of loads, the method comprising:

connecting the input to a power source;

connecting the first output to a first load;

connecting the second output to a second load;

connecting a super-capacitive device to at least one of the outputs to power a respective load; and

a regulator unit is connected to the input for charging the supercapacitive device.

According to a thirteenth aspect of the present invention, there is provided a method for powering a plurality of loads drawing respective load currents, the method comprising:

connecting the input to a power source that provides a predetermined maximum source current at a source voltage that falls within a predetermined range;

selectively connecting the output to a load and providing an output voltage;

providing a super-capacitive device in parallel with the output; and

a control circuit is provided between the input and the output to control the output voltage such that the load current is supplied while the source current is maintained to be less than a predetermined value.

According to a fourteenth aspect of the present invention, there is provided a method for drawing a corresponding load current I ₁ ，I ₂ ，......I _N The method for supplying power to a plurality of loads, wherein N is more than or equal to 2, the method comprises the following steps:

connecting the input to a power source having a predetermined maximum value I _S Under a source current of a source voltage V belonging to a predetermined range _S ；

Selectively connecting the output to one or more loads for application at respective predetermined load voltages V ₁ ，V ₂ ，......V _N Lower supply of a load current I ₁ ，I ₂ ，......I _N Wherein, V ₁ ≠V ₂ ，......， V ₁ ≠V _N ；

Providing a super-capacitive device in parallel with the output; and

a control circuit arranged between the input and the output for selectively switching V ₁ ，V ₂ ，......V _N To the output.

According to a fifteenth aspect of the present invention, there is provided a power supply method including:

connecting the input to a power source that provides a source voltage within a predetermined range at a source current;

the output and the suction have peak values (I) _LP ) Pulsed load current (I) _L1 ) The load of the power supply is connected;

between the input and the output a control circuit is arranged for supplying an output current (I) to the output _O ) The current having a predetermined peak value (I) _OP ) Wherein, I _OP ＜I _LP (ii) a And

providing a super-capacitive device in parallel with the output for providing the condition I _LP ≤(I _OP +I _C ) Capacitive current (I) of _C )。

According to a sixteenth aspect of the present invention, there is provided a power supply method including:

connecting the input to a power source, the power source providing a source voltage that falls within a predetermined range;

providing an output voltage on an output connected to a load that draws a load current at the output voltage;

connecting a super-capacitive device connected in parallel with the output; and

a control circuit is arranged between the input and the output to travel between first and second states in which the output voltage is substantially equal to the source voltage and is a regulated version of the source voltage, respectively.

According to a seventeenth aspect of the present invention, there is provided a power feeding method including:

connecting the input to a power source, the power source providing a predetermined source voltage;

causing the super-capacitive device to travel between a first state and a second state in which the device is connected in parallel with the output and not connected in parallel with the output; and

a control circuit is arranged between the input and the output for generating an output voltage in response to the source voltage, the circuit also causing the supercapacitive device to travel between the first state and the second state.

According to an eighteenth aspect of the present invention, there is provided a power supply method including:

providing an output voltage at an output, the voltage selected from a range of voltages including a source voltage, the output connected to one or more loads;

connecting a super-capacitive device in parallel with the output; and

a control circuit is arranged between the input and the output for generating an output voltage and limiting the output current to a predetermined maximum value in response to the source voltage.

According to a nineteenth aspect of the present invention, there is provided a power supply for a cellular telephone, the telephone having a first load and an LED flashlight, the power supply comprising:

an input for connection to a power source;

a first output for connection to a first load;

a second output for connection to an LED flash;

a super capacitive device connected to the second output for powering the LED flash; and

In certain embodiments, the regulator is in series with the power source and together they are in parallel with the supercapacitive device. In other embodiments, the super-capacitive device is in series with the input such that the super-capacitive device is in parallel with the LED flash along with the power source.

Preferably, the power supply is operable in a plurality of modes including:

a charging mode for charging the super-capacitive device; and

a discharge for discharging the super-capacitive device to power the LED flash.

In certain embodiments, the charge and discharge modes operate simultaneously. In other embodiments, the charge and discharge modes are selectively operated mutually exclusively. Preferably, the first load is powered regardless of whether the power supply is in a charging or discharging mode.

Preferably, the regulator unit limits the charging current to less than a predetermined value for the supercapacitor. More preferably, the predetermined value is about 2 amps. Even more preferably, the predetermined value is about 1 amp.

Preferably, the power supply limits the current drawn from the power source to a predetermined value. Preferably, the predetermined value is about 2 amps. More preferably, the predetermined value is about 1 amp.

In some embodiments, the first output limits the second output. In a further embodiment, the first output selectively limits the second output.

In certain embodiments, the first load is a communication module. In some embodiments, the first load is a power amplifier.

According to a twentieth aspect of the present invention, there is provided a power supply for an LED flash, the power supply comprising:

an input for connection to a power source;

an output for connection to an LED flash;

a super capacitive device connected to the output for powering the LED flash; and

According to a further aspect of the invention, a method is provided for drawing a corresponding load current I ₁ ， I ₂ ，......，I _N Wherein N ≧ 2, the power supply includes:

an input for connection to a supply voltage providing a minimum source voltage V _S The power source of (1);

an output for selectively connecting to one or more loads for providing a predetermined load voltage V ₁ ，V ₂ ，......，V _N Lower supply of a load current I ₁ ，I ₂ ，......，I _N Wherein V is ₁ ≠V ₂ ，......，V ₁ ≠V _N ；

A super-capacitive device connected in parallel with the output; and

a control circuit arranged between the input and the output for selectively switching V ₁ ，V ₂ ，......， V _N To the output.

Preferably, V ₁ ，V ₂ ，......，V _N One or more than one of V _S 。

Drawings

Preferred embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

FIG. 1 is a schematic diagram of a power supply according to an embodiment of the invention;

FIG. 2 is a schematic diagram of a power supply according to another embodiment of the present invention;

FIG. 3 is a schematic diagram of a power supply according to an embodiment of the invention;

FIG. 4 is a schematic diagram of a power supply according to another embodiment of the present invention;

FIG. 5 is a schematic diagram of a variable resistance voltage divider used to provide a reference voltage to the boost controller of the circuit in FIG. 5;

table 1 shows the logic used by the control block to operate the circuit of FIG. 2;

FIG. 6 is a schematic diagram of an alternative embodiment of the present invention incorporating a buck-boost regulator;

FIG. 7 illustrates a hardware implementation for limiting inrush current to a supercapacitor used in an embodiment of the present invention;

FIG. 8 shows experimental waveforms of ultracapacitor voltage and battery current when the ultracapacitor of FIG. 4 is charged while preventing inrush current;

FIG. 9 illustrates an alternative hardware implementation to that of FIG. 7;

FIG. 10 shows experimental waveforms for the circuit of FIG. 79;

FIG. 11 is a schematic diagram similar to that of FIG. 3 of an alternate embodiment of the present invention;

FIG. 12 is a schematic diagram of a power supply according to another embodiment of the present invention;

FIG. 13 is a schematic diagram of a power supply according to another embodiment of the present invention;

FIG. 14 is a schematic diagram of a power supply according to another embodiment of the present invention;

FIG. 15 is a schematic diagram of a power supply according to another embodiment of the present invention;

FIG. 16 is a schematic diagram of a power supply according to another embodiment of the present invention;

FIG. 17 is a schematic diagram of a power supply according to another embodiment of the present invention;

FIG. 18 is a schematic diagram of a prior art power supply;

FIG. 19 is a schematic diagram of a power supply according to another embodiment of the present invention;

fig. 20 is a schematic diagram of a power supply according to another embodiment of the present invention.

Detailed Description

Referring to fig. 1 and 2,

respective power supplies

1 and 20 are provided, each for powering a load in the form of a flash drive circuit 4 for a digital camera (not shown). Each power supply comprises a super-capacitive device in the form of a super-capacitor 8 for powering the circuit 4. A regulator unit in the form of an induction regulator 10 charges the supercapacitor 8.

Each power supply comprises an input 5, the input 5 being for connection to a power source in the form of a lithium ion battery 6. In other embodiments, alternative power sources are used, including but not limited to alternative battery types.

In the embodiment of fig. 1, the regulator 10 is in series with the battery 6 and together they are in parallel with the supercapacitor 8, whereas in the embodiment of fig. 2, the supercapacitor 8 is in series with the battery 6.

The regulator unit limits the charging current of the supercapacitor to a predetermined value. In the embodiment of fig. 2, the predetermined value is about 0.5 amps, while in the embodiment of fig. 1 it is about 0.1 amps. In other embodiments alternative predetermined values are used.

In the illustrated embodiment, the regulator 10 is a voltage regulator, in particular a voltage boost regulator. In some embodiments, a buck or buck-boost regulator is used. In other embodiments, the regulator unit takes the form of a charge pump (charge pump).

In some embodiments, an optional control block 9 is used to manage functional, logical, and/or selective aspects throughout the circuit. In some embodiments, control block 9 is defined by a processor external to the power supply. In other embodiments, the

power supply

1 or 20 is designed for inherent self-management.

In the embodiment of fig. 1, the

switches

11 and 13 travel between open and closed states in order to manage the charging/discharging of the supercapacitor 8 and the powering of the circuit 4. It will be appreciated that when switch 11 is open and switch 13 is closed, circuit 4 is isolated from battery 6 and regulator 10 charges supercapacitor 8. When the switch 11 is closed, the supercapacitor 8 is discharged to power the circuit 4. In certain embodiments, the switch 13 is opened to isolate the supercapacitor 8 from the battery 6 to reduce current leakage. However, it will be appreciated that in many embodiments, the switch 13 is replaced with a short circuit (short circuit).

In fig. 1 and many of the other figures of the present specification, selective connections are represented by switches. It should be appreciated, however, that in some embodiments, alternative mechanisms are used for selectively powering the load. For example, in certain embodiments, loads are selectively enabled or disabled as opposed to being physically connected or disconnected. It will be appreciated that this provides the same functionality-although the load is always physically electrically connected, it is only selectively powered. Other mechanisms include the use of switches including one or more FETs, transistors, etc., or the enabling/disabling of the regulator 10. For the present disclosure, switches are used to schematically represent any one or more of these or other suitable mechanisms for enabling selective connectivity in view of convenient visual representations.

In the embodiment of fig. 2, the three

switches

15, 16, 17 are selectively routed between their respective open and closed states in order to manage the function of the power supply 20. In some embodiments, not all of these switches are used. In other embodiments, more switches are used.

The

switches

15, 16, 17 allow the power supply to selectively operate in a charging mode, in which the regulator unit charges the supercapacitor 8, and a discharging mode, in which the supercapacitor 8 is discharged to supply the load 4. In the charging mode, the switches 15 and 16 are in the closed state, and the switch 17 is in the open state. When it is desired to power the circuit 4, the switch 17 travels to a closed state, allowing the discharge of the supercapacitor 8 in order to power the circuit 4. In the present embodiment, in the discharge mode, the regulator 10 is isolated from the supercapacitor 8, and as such, the switch 15 travels to an open state each time the switch 17 travels to a closed state. In certain embodiments, when switch 17 is advanced to a closed state, switch 15 remains in a closed state. It will be appreciated that in such an embodiment, the regulator 10 provides some load current while the supercapacitor 8 is discharging. This allows the use of smaller supercapacitors, but there is a trade-off by increased pressure on the battery 6-or current drawn therefrom.

The embodiments of fig. 1 and 2 show two main options for implementing embodiments of the invention:

■ A supercapacitor 8 is placed in parallel with the circuit 4.

■ A supercapacitor 8 is placed in parallel with the circuit 4 and in series with the battery 6.

Each of these options has corresponding unique advantages. Throughout the description, the advantages of each of these main alternatives are referred to by way of introduction of further embodiments.

Fig. 17 shows a schematic diagram of a power supply 120 suitable for use with both of the above options. Fig. 17 is arranged in a similar manner to fig. 2, but the switch 17 is now travelling between three states and incorporates a further switch 121. Those skilled in the art will appreciate that the arrangement of the power supply 120 allows for the proper configuration of the polarity of the supercapacitor 8 in the series and parallel options mentioned above.

Referring to fig. 3, an alternative embodiment of the power supply 1 is provided which also uses the option of a regulator 10 in series with the battery 6 and together with them in parallel with the supercapacitor 8. In this embodiment, the power supply 1 is for a cellular telephone 2 having a plurality of internal electrically pulsating loads in the form of a radio transmitter 3 for the telephone, a flash drive circuit 4 for a digital camera (not shown) integrated with the telephone, which draw respective load currents. The power supply 1 comprises an input 5 for connection to the power supply of the telephone 2 in the form of a detachable and rechargeable multi-cell lithium-ion battery pack 6. In this embodiment, the battery pack 6 supplies a predetermined maximum source current at a source voltage belonging to a predetermined range. The output 7 is selectively connected to the emitter 3 and the drive circuit 4 and provides an output voltage. A supercapacitive device, which takes the form of a 500mF supercapacitor 8, is connected in parallel with the output 7. In other cases, super-capacitive devices with other values are used. A control circuit, in the form of a control block 9 and a regulator 10, is arranged between the input 5 and the output 7 for controlling the output voltage such that the load current is provided while keeping the source current smaller than a predetermined value.

The connection of each load to the output 7 is selected so that the load can be selectively powered. In the embodiment of fig. 3, the emitter 3 and the drive circuit 4 are selectively connected to the output 7 by respective state switches 11 and 12, which are controlled by the block 9 to travel between open and closed states. In this embodiment, the control block 9 is part of the microcontroller firmware contained in the phone 2 and ensures that loads are mutually exclusively connected to the output 7. That is, when one of the emitter 3 and the drive circuit 4 is connected to the output 7, the other is not connected. This occurs:

■ In order to limit the peak current that must be supplied to the total load and therefore that must be delivered by the battery 6.

■ Since the regulator 10 provides one of a plurality of voltages on the output at any given time.

In this embodiment, regulator 10 provides 3.6 volts or 5.5 volts on the output when transmitter 3 and circuit 4 are connected, respectively. It would also be detrimental, if not destructive, for the emitter 3 to be exposed to 5.5 volts, as such, in the event that the voltage on the output rises to a higher voltage, it is isolated from the output 7 by the switch 11 being caused to travel to an open state.

In practice, it is not disadvantageous that the user cannot use both functions simultaneously. It is also useful to note that the circuit 4 needs to be higher than 5 volts only when high brightness light is required for flash photography. If low brightness light is sufficient, the circuit 4 draws a lower current at a lower voltage. For example, in "flash mode", the circuit 4 typically draws about 200mA at 3.6 volts. In this mode, the circuit 4 can be used in combination with the emitter 3, provided that the total average current drawn is less than a predetermined maximum current.

It will be appreciated that in other embodiments additional loads are selectively connected to the output either simultaneously or mutually exclusively with the transmitter 3 and the circuit 4.

The supercapacitor 8 is selectively connected to the output 7 by a state switch 13. The switch is operated by a control block 9, primarily to isolate the supercapacitor 8 from the output 7 when the current demanded by the load is low. This contributes to an increase in the operating life of the battery pack 6, as the duration between recharges is increased. This is due to the reduced consumption due to the reduced need to supply the pack with leakage current of the supercapacitor 8.

If the current demanded by the load does not remain low for a sufficiently long period of time, the switch 13 is omitted and the supercapacitor always remains connected in parallel with the load. Alternatively, if the supercapacitor supported load is not regularly used and is often left idle for a long period of time, the arrangement in fig. 11 is used. In particular, the switch 13 is positioned to simultaneously disconnect the supercapacitor 8, the transmitter 3 and the circuit 4 from the regulator 10. It will be appreciated that in fig. 11, features corresponding to those of fig. 3 are indicated by corresponding reference numerals.

It will be appreciated that for cellular telephones and other portable digital devices, the one or more loads are pulsed loads that switch between a standby mode and an operable mode with relatively low and relatively high load currents, respectively. For example, the transmitter 3 contains such a load as it travels between a transmission mode in which the power consumption is relatively high and a standby mode in which the power consumption is relatively low. Further, the ripple load represented by transmitter 3, which is a GPRS Class 12 transmitter, has a duty cycle of about 50%. Another special load, the driver circuit 4, discussed in this embodiment has a duty cycle ratio of about 2 to 10% (typically about 4-5%) when in use. Those skilled in the art will appreciate that in other embodiments, the alternative loads have different busy to idle ratios.

The power supply of fig. 3 allows the battery pack 6 and regulator 10 to be designed for relatively low peak currents. This is because:

■ The load typically has a relatively low busy-to-idle ratio.

■ The operation of the

switches

11 and 12 by the control block 9 allows: for any given time interval, at least one load current is zero or near zero.

■ The operation of the switch 13 by the control block 9 allows: for any given time interval, the loss of the battery pack in supplying leakage current to the supercapacitor is minimized.

■ The super capacitor contributes to the load current when one of the transmitter 3 and the circuit 4 draws a corresponding load current from the output 7 and the super capacitor 8 is connected to the output. Therefore, there is a reduction in the peak load current required from the output of the control circuit. In particular, there is a reduction in the peak current required from the regulator 10, and a reduction in the peak current required from the battery pack 6.

The super capacitor 8 has sufficient capacitance to supply the total load current for one period of the pulsating load while receiving the maximum allowable current from the regulator 10. This allows the regulator 10 to be designed to supply a peak current that is closer to the average current required by the transmitter when in the relatively high power mode, since the transmitter 3 and circuit 4 are not connected simultaneously with the output 7. In embodiments like this, only one load current will have a non-zero value for a given time interval. In this case, the capacity of the supercapacitor needs only to be sufficient for one cycle to supply the load that requires the most energy in such a cycle. However, in some embodiments, more than one load is connected to the output at the same time, as such, the battery pack 6 and regulator 10 must be configured to provide the desired peak current inherent in such a combination of loads. In this case the current supplied by the battery 6 and the regulator 10 will be the average current in one cycle of the combined load, while the supercapacitor 8 will supply the combined load with the difference between the current supplied by the battery 6 and the regulator 10 and the peak current required by the load combination.

The

switches

11, 12, 13 are responsive to the control block 9 for travelling between open and closed configurations. Preferably, the switches are respective transistors, more preferably respective FETs.

The control block 9 is responsive to a number of variables for determining the state of the

switches

11, 12, 13. For example, in this embodiment, the control block 9 is responsive to a load current below a predetermined threshold for determining whether to connect the supercapacitor 8 to the output. However, in other embodiments, the supercapacitive device is selectively electrically disconnected from the output power when the load current is below the threshold for a predetermined period of time. In other embodiments, the super-capacitive device is selectively disconnected from the output when the load current is below a threshold and the output voltage is less than the source voltage. In other embodiments, the control block 9 sets the state of the

switches

11, 12, 13 depending on the function that the user has selected, for example taking a picture with a camera phone.

Some key principles of the above-described embodiments can be expressed as follows.

First, the load comprises respective operating voltages, at least one of which is different from all other operating voltages. In particular, the load is at an operating voltage V ₁ ，V ₂ ，......，V _N Draw down a corresponding load current I ₁ ，I ₂ ，......，I _N Wherein N is not less than 2 and V ₁ ≠V ₂ ，......， V ₁ ≠V _N . The control circuit controls the output voltage to selectively provide V on the output ₁ ，V ₂ ，......， V _N . Specifically, control block 9 controls regulator 10 and switches 11, 12, 13 to selectively provide V at the output ₁ ，V ₂ ，......，V _N 。

It will be appreciated that the different load voltages provided at the output are provided as such while a super capacitor is typically held in parallel with the output.

Second, V ₁ ，V ₂ ，......，V _N Is greater than a predetermined source voltage. That is, the control circuit includes circuitry adapted to selectively maintain the output voltage at or about V ₁ ，V ₂ ，......， V _N Of the at least one regulator 10 that is greater than the source voltage provided by the battery pack 6. In other embodiments, the regulator is selectively deactivated to enable the voltage provided by the battery pack 6 to be applied directly across the load. This provides increased efficiency for situations where such a connection is allowed, as no regulator is required.

In some embodiments of the present invention, the regulator 10 is a boost circuit that provides an output voltage greater than the voltage provided by the battery pack 6. In other embodiments, the regulator 10 is a buck-boost circuit that provides an output voltage that is greater than, less than, or about equal to the voltage provided by the battery pack 6.

The voltage and current supplied by the battery pack 6 vary with time. For example, due to the discharge characteristics of the cells in the battery pack, the internal resistance of the cells, and any associated electronic protection circuitry used in the battery pack. In any case, the battery pack will be used up and the phone 2 will not be able to operate. However, due to the much smaller spread in the peak currents drawn by the different loads powered by the battery 6-because of the use of the super-capacitor 8 in parallel with the load, more operating time can be obtained from the battery than would otherwise be the case.

In other embodiments, the power source is a fuel cell or other portable energy storage device. In a further embodiment, the power source is a mains power source. More preferably, the power source is a controllable power source. In all cases, the use of a supercapacitor 8, or other supercapacitive device, in parallel with the load has the effect of:

■ Reducing the peak current experienced by the power source for a given pulsating load.

■ Reducing peak current dispersion experienced by the power source due to different loads.

As will be appreciated by those skilled in the art, large capacitances provide current and power averaging effects. It is important that the main capacitance in the power supply of fig. 3, which is the capacitance provided by the supercapacitor 8, is arranged not only downstream of the battery pack, but also downstream of the regulator. Accordingly, the obtained averaging effect relates to the current that needs to be delivered by the battery 6 to the input 5 and the current that needs to be delivered by the regulator 10 to the output 7. This makes it possible to either one or a combination of the following:

■ The reduction in size of the battery pack and regulator, and therefore the phone 2.

■ The same function is provided with the battery 2, but with a longer period of time between recharges.

■ Additional functionality is provided in the phone 2.

The value of the capacitance provided by the supercapacitor 8 is an order of magnitude greater than or higher than that provided by a conventional capacitor, which occupies a corresponding volume in a cellular telephone or other appliance.

The inventors have realized that applying a large capacitance to the load side of the regulator as was done in the previous embodiment is counter-intuitive, let alone effected with a super-capacitive device. The reason is that such low impedance devices on the load side of the regulator will generate inrush currents that will overload the regulator and/or the battery. However, the inventors have also realised that with minimal hardware complexity beyond the required regulators and switches 11, 12, 13, such currents can be prevented while also obtaining considerable additional effects. These effects will be further described with reference to the following examples of the present invention.

Referring to fig. 4, there is schematically shown a circuit 21 which is part of a battery-powered cellular telephone with an integrated digital camera (referred to as a "camera phone"). It will be apparent to those skilled in the art that the same principles can be applied to a PDA having cellular phone and camera functions.

The function of the circuit 21 is to provide peak power to the LED, which in this embodiment is used as a camera flash, or GPRS communication module. In other embodiments, the communication module operates in accordance with one or more of the GSM or CDMA standards. Returning to the present embodiment, the circuit 21 is applicable to, for example, the following communication modules:

■Siemens MC45。

■Wavecomm Q2400。

in a further embodiment, the circuit 21 is configured as an RF power amplifier for GSM, GPRS, CDMA communication, for example for:

■Mororola MRFIC0970。

■Mororola MRFIC1870。

■Hitachi PF08122B。

the battery and regulator, which takes the form of "boost control," cannot provide the peak power required to operate both the communication module and the LEDs at the same time. For convenience, V ⁺ Representing power input to the different circuit blocks in figure 4. It will be appreciated, however, that these inputs to the different circuit blocks are not equal in all cases. Specifically, certain circuit blocks-those with low peak currents-cause V ⁺ Continuously connected directly to the positive terminal of the battery, that is, the input to the regulator. However, other circuit blocks, e.g. communication modules, V ⁺ Is selectively connected to the output of the regulator. This voltage, i.e. the voltage across the two-cell supercapacitor SCAP, is called V _SCAP 。

Camera phones, PDAs and similar portable electronic devices have microcontrollers that implement most of their functions. In such an embodiment, the control block 22 is implemented as part of the microcontroller firmware. However, in embodiments where the microcontroller has fewer than two A/D inputs and insufficient digital I/O, this functionality may be implemented as a combination of microcontroller firmware and hardware for the external interface. In a further embodiment, this functionality is provided by implementation in hardware, in addition to any microcontroller.

The key features of circuit 21 are described below. These characteristics should be read in the context of the information in table 1.

Circuit 21 contains a voltage regulator in the form of a boost converter based on a standard chip called boost control 23. The boost converter sets the voltage to a voltage required to drive one of the following at any time:

■ LEDD2, when FlASH function is required (indicated in table 1 as V in FlASH mode _FLASH ) (ii) a Or

■ A communication module 24, when communication is required (represented in Table 1 as V in COMMS mode _COMMS )。

In certain embodiments, LED D2 is defined by a plurality of LEDs connected in parallel. In a further embodiment, the LED D2 is defined by a plurality of LEDs in series, however, it will be appreciated that this would require a multi-cell super-capacitive device.

The voltage generated by the boost converter is marked V in fig. 4 _BOOST This voltage, minus any voltage drop across FET Q3, will be applied to any load. It will be appreciated that for the load of interest, LED D2 and the communication module 24, the value of the required load voltage, V respectively _FLASH And V _COMMS Is different. In this embodiment, V _FLASH And V _COMMS Are about 5.5 volts and 3.6 volts, respectively. In other embodiments, an additional load is included that requires V _BOOST Is selectively set at a value different from V _FLASH And V _COMMS The voltage of (c).

The boost controller will V depending on the load present _BOOST Is selected as V _FLASH Or V _COMMS . The value of which is determined by setting the reference voltage input V of the step-up converter _REF Is controlled. Although in this embodiment the voltage is controlled directly from control block 22, in other embodiments alternative arrangements are used. An alternative is to connect the relevant input to the voltage reference provided by the resistor divider and use a FET to switch another resistor into or out of the circuit as required. An example of which is schematically shown in fig. 5. It will be appreciated that other arrangements are possible, including the use of D/a converters or other components.

The boost converter in fig. 4 has fet q2, which is external to boost control 23 and is included in conjunction with diode D1 for the switch. It will be appreciated by those skilled in the art that switching to produce a greater than V for inductor L1 occurs in conjunction with other components _batt V of _BOOST The value of (c). Other alternatives for the combination of fet q2 and diode D1 include:

■ The synchronous boost converter of D1 is replaced with PFET.

■ A boost converter IC including similar components inside the IC.

Other combinations will be apparent to the skilled reader with the benefit of the teachings herein.

If the battery voltage V _batt Less than V for a given load _BOOST Control block 22 will enable the boost converter by holding pin EN of boost control 23 high. At the same time, control block 22 drives the gate of fet q1 high, causing fet q1 to be turned off. On the contrary, if the battery voltage V _batt Greater than or equal to the desired V _BOOST Then the boost converter is disabled and Q1 is turned on.

This combination of events improves the efficiency of the circuit 21 when the battery is in a high state of charge, but also allows the circuit 21 to continue to operate when the battery is in a low state of charge. In addition, this will contribute to an enhanced ability to draw more energy from the battery, as the use of a super capacitor on the regulator load side reduces the peak current load on the battery. In particular, V is due to the internal resistance of the battery _batt Peak value of (1)The drop is reduced.

In some embodiments, circuit 21 and associated cellular telephone may be operated up to V _batt About 1.5 volts. In the case of a lithium ion battery, to prevent damage to the battery, it is not discharged to such a level. However, it will typically be discharged to about 3 volts, at which point little energy is left in the battery. It also has the benefit of: allowing the battery 21 to be powered by an alternative battery, such as two AA batteries in series or three AA batteries in series. This functionality allows phone users to seek a cost-effective short-term power supply in the event that the normal battery is discharged and cannot be recharged before the desired use. This has particular advantages in emergency situations.

Battery packs for portable electronic devices typically include one or more rechargeable batteries and protection circuitry for reducing the risk of damaging the batteries during charging, recharging and use. Protection circuit pair voltage V _batt In response to a drop to a "stop voltage" that prevents any further discharge of the battery. This is important for some batteries because discharging to too low a level increases the risk of damage to the battery. However, for primary batteries (primarybatteries), the circuit 21 will operate until the battery voltage is below the minimum input voltage for the boost converter, typically about 1.5 volts.

The circuit 21 comprises one super-capacitive device in the form of a two-cell super-capacitor SCAP. Such a supercapacitor is manufactured by CAP-XX and is referred to as GS206. It will be appreciated that in other embodiments, alternative supercapacitors are used.

The super capacitor SCAP supplies pulsating current to the LED D2 when a flash is required, or to the communication module 24 when communication is required.

The supercapacitor SCAP is charged through the boost control 23 and the fet q3. This combination allows the current supplied by the regulator to be controlled and therefore limited when the supercapacitor is usedAny inrush current to the SCAP when it is in a low charge state. It will be appreciated that the current limiting function in boost control 22 is only when the regulator output voltage is higher than the input voltage to the regulator (V) _batt ) Operating when the voltage drop across diode D1 is subtracted. Since the voltage drop across diode D1 is typically about 0.5 volts, the regulator is only effective at limiting current at this time:

V _BOOST ＞V _batt -0.5 volt

Until this condition is met, diode D1 conducts and current flows through inductor L1 and diode D1 to the load.

If the supercapacitor SCAP needs to be charged, control block 23 turns FETQ3 off until V _BOOST ＞V _batt Then, fet q3 is turned on. Once in this state, the supercapacitor SCAP is gradually charged to V _BOOST The level of (c).

An alternative to fet q3 and associated control logic is to use a PNP transistor as shown in fig. 9. For ease of reference, the PNP transistor is referred to as transistor Q3. Such a transistor will not conduct until V _BOOST About ratio V _batt 0.7 volts, at which point there is sufficient base-emitter voltage to turn on transistor Q3. Fig. 10 shows the charging current and the supercapacitor voltage for this embodiment with the boost current limit set to about 600 mA.

If the FLASH mode requires V _BOOST A value greater than the maximum voltage allowable on the power input of the communication module 24, fet q4 is included to isolate the module 24 when the circuit 21 is in FLASH mode.

If the FLASH mode requires V _BOOST The value may shorten the operational life of the supercapacitor SCAP, then V when FLASH mode is not required _BOOST Is lowered. For example, in this embodiment, the control block 22 contains a timeout (timeout) period. If the camera phone remains in FLASH mode for a timeout period since the last user activity occurred, the unit reverts to non-FLASH mode and V _BOOST Is loweredDown to the level required for COMMS mode. In this embodiment, the timeout period is one minute, while in other embodiments, the timeout period is different. Typically, the timeout period is in the range of about 30 seconds to about five minutes. User activities mentioned aboveActions include activities such as focusing on the camera, taking a picture, selecting a camera mode, etc.

In the embodiment shown in FIG. 4, FETQ5 and resistor R3 are included to quickly bring the ultracapacitor from V _FLASH Discharge to V _COMMS . In other embodiments, fet q5 and resistor R3 are omitted and the supercapacitor is discharged through diode D2, fet q6 and resistor R4.

In another embodiment, the forward voltage required to drive the led d2 is low enough that V _FLASH Less than the maximum operating voltage of the communication module 24. Thus, the circuit 21 contains the following simplifications:

■V _BOOST is fixed at a value because V _BOOST ＝V _FLASH ＝V _COMMS . This allows the voltage reference to the boost converter (or buck-boost converter in other embodiments) to be fixed. That is, there is no longer a select reference voltage for control block 22 to guarantee V _BOOST Matching the demand of the load that is currently drawing current from the boost control 23.

■ Conditions 7 to 12 in table 1 are no longer required.

■ FETQ4 is no longer needed because V + of the communication module 24 can be directly connected to V _SCAP 。

■ FETQ5 and its associated control logic are no longer needed to slave supercapacitor SCAP from V _FLASH Discharge to V _COMMS . Accordingly, resistor R3 and associated control logic in control block 22 may be omitted in addition to FETQ 5.

If the maximum operating voltage of the control block 22, other circuits 27 used in the camera phone, and the LED current control 28 are all less than V _FLASH The corresponding power supply pins are, in some embodiments, directly connectedTo V _BOOST Instead of V _batt In order to provide a better adjustable power source. In addition, this alternative allows the circuit 21 to operate even when the battery is in a very low state of charge, since the boost converter can operate to convert V _BOOST Maintained above V _batt The level of (c). Any further circuitry within the camera phone can also draw power from the output side of the boost controller rather than directly from the battery. These other circuits include, for example, other voltage regulators, DC-DC converters, or other power supplies.

As mentioned above, the supercapacitor SCAP is a multi-cell supercapacitor, wherein two cells are connected in series. Each cell has a nominal operating voltage of about 2.5 volts. This voltage can be exceeded without permanent damage to the supercapacitor, but operation at higher voltages for extended periods of time can reduce the useful life of the supercapacitor. The supercapacitor eventually breaks down once a sufficiently large voltage is applied.

The supercapacitor SCAP draws leakage current when held at voltage. In addition, in order to obtain voltage balance between cells in the supercapacitor, a balancing circuit 31 is used. The purpose of circuit 31 is to prevent any one cell from over-voltage and damaging the super-capacitor. This embodiment comprises one of the simplest forms of a balancing circuit comprising two series-connected equivalent resistors R1 and R2 in parallel with the cells of the supercapacitor SCAP. The resistors R1 and R2 are referred to as balance resistors.

The balancing circuit 31 also draws current. The combination of the leakage current of the supercapacitor SCAP and the current drawn by the circuit 31 is an unwanted discharge on the battery when the camera phone is switched off or in standby mode. One option is for control block 22 to turn off boost control 23 and fet q3 at these low load current demands. When the control block 22 detects that the camera phone is likely to transmit-for example, when the user starts to enter a phone number to be dialed-the supercapacitor SCAP is gradually charged to the required voltage through the fet q3. Performing gradual charging to control the superThe capacitor surges current. In this embodiment, the control block 22 and other circuitry 27 of the camera phone are directly from V _batt Is powered and is therefore enabled independently of the state of charge of the supercapacitor SCAP.

In other embodiments, as mentioned above, control block 22, other circuitry 27, and LED current control 28 are driven from V _BOOST Is powered. In these embodiments, a reduction in the loss of leakage current from the balancing resistor and the supercapacitor is achieved by enabling boost control 23 and turning fet q3 off during periods of low load current demand.

Alternatively, if the communication module 28 is periodically required to transmit, the FET Q3 is turned on. This occurs in response to polling, for example, from the network. In this case, the battery or other power source must tolerate the energy loss of the balancing circuit shown in fig. 4. An improvement to this is the use of very low current active (active) balancing circuits. Typically, the current of the low current active circuit, including the supercapacitor leakage current, will be less than about 5 μ A.

In other embodiments, the FET Q3 is placed as shown in FIG. 12. Which disconnects the super-capacitor and associated balancing circuitry from the output of the boost control 23 while allowing the communication module 24 to be powered and able to respond to polling from the network. The response to the polling is typically only one GPRS time slot (which is 577 μ s), which in some embodiments is supported by a smaller capacitance than that provided by the supercapacitor SCAP.

Table 1 provides the logic used in circuit 21. To assist the reader, the following comments are provided:

V _batt is a battery voltage that may be greater than or less than a nominal or desired load voltage of the communication module 24V _COMMS 。

Suppose that the communication module 24 is directly driven from V _batt Run at the maximum possible value of V _batt ＞V _COMMS At the same time, the communication module is directly powered by the battery and the super capacitor SCAP. Also hasThat is, fet Q1, Q3, and Q4 are on, and the boost control 23 is deactivated.

The buck-boost regulator topology shown in fig. 6 is used in some embodiments in place of the boost-only regulator topology of fig. 4. This eliminates the need for the bypass FET Q1 and associated logic. Additionally, this eliminates the need for FET Q3 and associated logic if there is current sensing in the inductor path. However, in some embodiments it is desirable to disconnect the supercapacitor from the output of the buck-boost regulator (as described above), and as such, FET Q3 is retained.

The minimum voltage to which the super-capacitor needs to be charged in order to supply the pulsating power to the LED D2 is greater than the minimum voltage to which the battery will be discharged while still keeping the circuit fully operational. Therefore, regulators in the form of boost converters or buck-boost converters are used.

V for control of FETQ3 when using a boost converter _batt And V _BOOST The embodiment of the comparison between preferably includes compensation for hysteresis effects.

DV is the tolerance (tolerance) for the target voltage that the supercapacitor must be charged to before the relevant FET is turned on. One label is used for all cases, namely "DV", but it will be understood that in different cases DV will have the same or different value for each listed condition.

To control the peak current, the inrush current must be controlled when charging the discharged supercapacitor. Certain methods for doing so are disclosed in PCT/AU02/01762, the subject matter of which is incorporated herein by cross-reference. Typical implementations of the current limiting function in a boost converter or regulator do not limit the ultracapacitor inrush current until the boost voltage provided by the regulator is greater than the input voltage to the regulator. This is because the useful current sensing function is often implemented on the ground pin of FET Q2. As shown in fig. 4, the ground pin is the source of FET Q2.

When the output voltage of the regulator is less than the regulator input voltage minus the diode drop across diode D1:

■ The FET D2 will be turned off.

■ There is no effective current sensing.

■ Current will flow through L1 and D1.

Embodiments of the present invention are configured to ensure that inrush currents are prevented or at least controlled. The two solutions contained in this description are provided in fig. 4 and 6, respectively. Turning first to FIG. 4, circuit 21 includes FETQ3 and the input voltage (V) _batt ) And the output voltage (V) _BOOST ) A comparator with hysteresis for making the comparison. It will be appreciated that although the input voltage in this embodiment is provided by a secondary battery, in other embodiments it is provided by a different voltage source, not necessarily a battery.

The hysteresis value is set at twice VD1, where VD1 is the voltage drop across D1 when D1 begins to conduct. As determined from fig. 4, the diode D1 is a schottky diode and has a typical voltage drop VD1 of about 500 mV. In other embodiments, alternative diodes and hysteresis values are used.

When V is _BOOST ＞(V _batt + VD 1), fet q3 is turned on. This discharges the capacitor C2 into the super capacitor SCAP. When V is _BOOST ＜(V _batt -VD 1), fet q3 is turned off. This allows the boost control 23 to charge the capacitor C2 again. It also prevents excessive surge currents, since the diode D1 will only be at V _BOOST ＜(V _batt -VD 1) is started. This cycle continues until the charge on the supercapacitor SCAP causes V _batt And V _BOOST The voltage difference between them is small enough to prevent surge currents.

Fig. 7 shows one possible hardware implementation of the inrush current limiting function used in an embodiment of the present invention. FIG. 8 is a SPICE simulation of ultracapacitor voltage and battery current as the ultracapacitor is charged. In other embodiments, the hysteresis value is set to be less than VD1, and as a result, it takes longer to charge the ultracapacitor.

In other embodiments, the comparison function is implemented using an A/D converter and a microcontroller. The microcontroller implements the following algorithm:

■ When V is _BOOST ＞(V _batt + VD 1), FETQ3 is turned on.

■ When V is _BOOST ＞(V _batt -VD 1), FETQ3 is turned off.

In certain embodiments, the A/D converter and the ability to switch more than one input channel to A/D are already available in the microcontroller. In these embodiments, the complete functionality is thus implemented in firmware. In an alternative embodiment where only one input channel is available to the microcontroller A/D, two FETs or analog switches, V, external to the microcontroller are used _batt And V _BOOST Is switched to the input channel.Another alternative is to use an a/D converter external to the microcontroller. The microcontroller will optionally convert V _batt Or V _BOOST Switch to the input of the a/D and read the result. The gate of fet q3 is then controlled according to the above algorithm.

The advantage of using FET Q3 to limit current is:

■ For the hardware implementation of inrush current control: v _BOOST Can be set to be (V) _batt Half the hysteresis voltage used by the + comparator) is as low.

■ For the firmware implementation of inrush current control: hysteresis energy at V _BOOST ＞V _batt By turning on FETQ3 and at V _BOOST ＜(V _batt VH) is simply biased by turning off fet q3, where VH is set to keep the current flowing from the battery below a maximum limit. It has been found that VD1 is a good choice for VH because it allows V _BOOST Is set at V _batt 。

■ Since FET Q3 is either off or on, it is never in its linear region except at the instant of switching, there is little power loss in FET Q3. This allows FET Q3 to be a small device.

A second solution to limit or prevent inrush current to a supercapacitor is shown in fig. 9. In this particular embodiment, circuit 41 includes transistor Q3, which is a BJT having the model designation ZXT13P12DE 6. In other embodiments, different transistors are used. Transistor Q3 is selected as:

■ Managing the power dissipation that the supercapacitor SCAP will be subjected to when it is charged.

■ Has a low saturation voltage which in turn reduces power dissipation.

In circuit 41, voltage feedback input (V) to boost control 23 _FB ) Is connected to the supercapacitor voltage (V) _SCAP ). When the boost control 23 is enabled, the capacitor C2 is charged. However, at the feedback input is connected to V _SCAP In the case of (2), V _FB Kept at 0V (assuming the supercapacitor is fully discharged). When the voltage (V) across the capacitor C2 _BOOST ) Greater than V _batt And the base-emitter turn-on voltage of transistor Q3, the transistor turns on to allow partial charging of the supercapacitor. During charging, the normal function of the boost control 23 to limit current operates. Resistor R5 is selected to allow transistor Q3 to reach saturation without excessive current through resistor R5. Typical values for resistor R5 are in the range of about 27 ohms to 100 ohms.

One of the main advantages of circuit 41 is that it does not require special logic control. It is important, however, that the circuit is best suited for these applications: wherein, at all times, V _BOOST Greater than (V) _batt +V _BE ) Wherein V is _BE Is the turn-on voltage of transistor Q3. Typically, V _BE About 0.6 volts. If V _BOOST ＞(V _batt +0.6 volts), another schottky diode similar to D1 is placed between the collector of transistor Q3 and the supercapacitor to prevent current flow through the base of transistor Q3 and the supercapacitorThe current of the p-n junction formed by the collector is advantageous.

Fig. 10 shows an experimental waveform of circuit 41 when the charged supercapacitor is a CAP-XXGW201 supercapacitor. The characteristics of the super capacitor are as follows: a capacitance of 300 mF; ESR of 80 mOhms. The super capacitor is arranged at the output side of the regulator and has a voltage of 3V _batt And a 500mA battery current limited battery charged to 3.8 volts.

Some of the above embodiments use a current limiting function in combination with hysteresis for the comparison function used to control FETQ3. Suitably employing this combination, the minimum battery voltage and V for powering the communication module 24 directly from the battery is applied _BOOST Given certain considerations.

Take the case where FET Q3 is controlled by the following logic:

■ When V is _BOOST ＞V _batt +V _H When FETQ3 is turned on

■ When V is _BOOST ＜V _batt -V _L Turn off FETQ3

Wherein, V _H And V _L High hysteresis voltage and low hysteresis voltage, respectively. If VCOMMS is the output voltage from boost control 23 when communication module 24 is powered by boost control 23 rather than directly from the battery, boost control 23 and fet q1 are preferably controlled by the following logic:

■ When V is _batt ＞V _COMMS -V _L At this time, boost control 23 is disabled and FETQ1 is turned on

■ When V is _batt ＜V _COMMS -V _L When the boost control 23 is enabled and Q1 is turned off

To achieve this, the conditions in control block 22 are changed accordingly.

Table 1: function of control block 22

Status of state ID	Mode(s) for	V _SCAP	Vbatt and V _BOOST	Vbatt and on-demand Boosted voltage	Boost EN	Is a V _BOOST = is provided with Arranged V _REF	Q1	Q3	Q4	Q5	Movement of
Status of state ID	Mode(s) for	V _SCAP	Vbatt and V _BOOST	Vbatt and on-demand Boosted voltage	Boost EN	Is a V _BOOST = is provided with Arranged V _REF	Q1	Q3	Q4	Q5	Movement of	1	To SCAP Charging method and apparatus COMMS	＜V _batt -ΔV	V _BOOST ＜V _batt	V _batt ＞V _COMMS	ON	V _FLASH	OFF	OFF	OFF	OFF	If the cell is COMMS mode and V _batt ＞V _COMMS Need to make To temporarily change the boost voltage to V _FLASH So as to ensure the pressure-boosting effect, so that the current limiting becomes operative.
2	To SCAP Charging method and apparatus COMMS	＜V _batt -ΔV	V _BOOST ＞V _batt	V _batt ＞V _COMMS	ON	V _FLASH	OFF	ON	OFF	OFF	When V is _BOOST ＞V _batt In time, the current limit can be operated and can be turned on Q3 is turned on so as toAnd charging the super capacitor.	1	To SCAP Charging method and apparatus COMMS	＜V _batt -ΔV	V _BOOST ＜V _batt	V _batt ＞V _COMMS	ON	V _FLASH	OFF	OFF	OFF	OFF
2	To SCAP Charging method and apparatus COMMS	＜V _batt -ΔV	V _BOOST ＞V _batt	V _batt ＞V _COMMS	ON	V _FLASH	OFF	ON	OFF	OFF		3	COMMS	＝V _batt ±ΔV	X	V _batt ＞V _COMMS	OFF	V _FLASH	ON	ON	ON	OFF	V _SCAP Belonging to V for supplying power to COMMS module _batt Is allowed to Within the error range, so that the current can be in the condition of no excessive surge current Connecting the battery to the super capacitor and activating to And supplying power to the COMMS. The communication is ready.
4	To SCAP Charging method and apparatus COMMS	＜V _COMMS -ΔV	V _BOOST ＜V _batt	V _batt ＜V _COMMS	ON	V _COMMS	OFF	OFF	OFF	OFF	If the cell is COMMS mode and V _batt ＜V _COMMS But do not When the super capacitor is discharged, the Q1 and the Q3 are switched off Set under the condition of V _BOOST ＝V _COMMS To prevent the battery from going to super The capacitor discharges.	3	COMMS	＝V _batt ±ΔV	X	V _batt ＞V _COMMS	OFF	V _FLASH	ON	ON	ON	OFF
4	To SCAP Charging method and apparatus COMMS	＜V _COMMS -ΔV	V _BOOST ＜V _batt	V _batt ＜V _COMMS	ON	V _COMMS	OFF	OFF	OFF	OFF		5	To SCAP Charging of electricity COMMS	＜V _COMMS -ΔV	V _BOOST ＞V _batt	V _batt ＜V _COMMS	ON	V _COMMS	OFF	ON	OFF	OFF	When V is _BOOST ＞V _batt In time, the current limit can work and can be opened Q3 to charge the supercapacitor.
6	COMMS	＜V _COMMS ±ΔV	V _BOOST ＞V _batt	V _batt ＜V _COMMS	ON	V _COMMS	OFF	ON	ON	OFF	V _SCAP Belong to V _COMMS Within the tolerance range of (A) and is therefore now Power to COMMS module may be enabled and ready to turn on The letter is sent.	5	To SCAP Charging of electricity COMMS	＜V _COMMS -ΔV	V _BOOST ＞V _batt	V _batt ＜V _COMMS	ON	V _COMMS	OFF	ON	OFF	OFF

State model ID	V _SCAP	Vbatt and V _BOOST	Vbatt and on-demand Boosted voltage	Boost EN	Is a V _BOOST = is provided with Arranged V _REF	Q1	Q3	Q4	Q5	Movement of
State model ID	V _SCAP	Vbatt and V _BOOST	Vbatt and on-demand Boosted voltage	Boost EN	Is a V _BOOST = is provided with Arranged V _REF	Q1	Q3	Q4	Q5	Movement of	7-way SCAP Charging of electricity FLASH	＜V _FLASH -ΔV	V _BOOST ＜V _batt	V _batt ＜V _FLASH	ON	V _FLASH	OFF	OFF	OFF	OFF	Charging the boost voltage so that V _BOOST ＞V _batt So that the current is limited The manufacturing becomes operational.
8-way SCAP Charging of electricity FLASH	＜V _FLASH -ΔV	V _BOOST ＞V _batt	V _batt ＜V _FLASH	ON	V _FLASH	OFF	ON	OFF	OFF	When V is _BOOST ＞V _batt In time, the current limit can be operated and can be opened Q3 is turned on to charge the supercapacitor.	7-way SCAP Charging of electricity FLASH	＜V _FLASH -ΔV	V _BOOST ＜V _batt	V _batt ＜V _FLASH	ON	V _FLASH	OFF	OFF	OFF	OFF
8-way SCAP Charging of electricity FLASH	＜V _FLASH -ΔV	V _BOOST ＞V _batt	V _batt ＜V _FLASH	ON	V _FLASH	OFF	ON	OFF	OFF		9FLASH	＞V _FLASH -ΔV	V _BOOST ＞V _batt	V _batt ＜V _FLASH	ON	V _FLASH	OFF	ON	OFF	OFF	The super capacitor is charged toV _FLASH Within a tolerance range of And (4) the following steps. It is now well established to use flashlights.
10 will SCAP Is discharged to COMMS	＞V _batt +ΔV	X	V _batt ＞V _COMMS	OFF	X	OFF	OFF	OFF	ON	Using boost current limiting, the ultracapacitor has been charged large At V _batt Value of (a), however, V _batt Is used for COMMS mode A sufficient voltage of formula (la). Now turn off boost and go through R3 pair The stage capacitor is discharged until the supercapacitor voltage is close enough to Battery voltage, can connect the battery to the super under condition 11 And a capacitor.	9FLASH	＞V _FLASH -ΔV	V _BOOST ＞V _batt	V _batt ＜V _FLASH	ON	V _FLASH	OFF	ON	OFF	OFF
10 will SCAP Is discharged to COMMS	＞V _batt +ΔV	X	V _batt ＞V _COMMS	OFF	X	OFF	OFF	OFF	ON		11COMMS	＝V _batt ±ΔV	X	V _batt ＞V _COMMS	OFF	X	ON	ON	ON	OFF	The super capacitor is discharged to about the same value as the battery, can Connecting a battery to a battery without too high an inrush current A super capacitor and enables power to the COMMS module. Ready for communication.
12 will SCAP Is discharged to COMMS	＞V _COMMS +ΔV	X	V _batt ＜V _COMMS	OFF	X	OFF	OFF	OFF	ON	The super capacitor is charged to be greater than V _COMMS The value of (a), however, V _COMMS is a sufficient voltage for the COMMS mode. Now that After the boosting is turned off and the super capacitor is discharged through R3 To the super capacitor voltage is sufficientClose to V _COMMS Can lift The voltage is connected to the supercapacitor under condition 13.	11COMMS	＝V _batt ±ΔV	X	V _batt ＞V _COMMS	OFF	X	ON	ON	ON	OFF

As an alternative to the boost control plus bypass FET Q1 configuration provided by fig. 4, a regulator in the form of a buck-boost controller is used. An embodiment of the present invention including regulation provided by a buck-boost controller is shown in fig. 6, where corresponding features are labeled with corresponding reference numerals. Fig. 6 provides a circuit 51 with the following main advantages:

■ With respect to the circuit of fig. 4, FET Q1 and its associated control logic are eliminated.

■ If the buck-boost converter senses current flowing in inductor L1, FET Q3 is no longer needed for current control because it can be controlled by the converter itself. In the illustrated embodiment, the converter used is LTC3441, which can be configured to sense the current in the inductor.

If the buck-boost converter senses current flowing into inductor L1, FET Q3 may still be included if it is desired to disconnect the supercapacitor from the power source, which in this embodiment is a battery, to eliminate supercapacitor leakage current and balance circuit current when:

■ The communication module 24 is in standby mode; and

■ When the camera phone does not have to be ready to transmit or take a flash photo; and

■ The buck-boost converter is still enabled.

Alternatively, if the buck-boost converter does not need to be enabled in standby mode, the buck-boost converter can be disabled in standby mode in order to eliminate the ultracapacitor leakage current. In this case, FETQ3 is omitted, and V _SCAP Is directly connected to V _BOOST . That is to say that， V _SCAP ＝V _BOOST 。

The circuit 51 is most advantageous in applications where the overall efficiency of the power supply is not critical, because when V is _batt ＞V _BOOST At a slight cost of efficiency. The circuit 51 is therefore also suitable for V _batt ≤ V _BOOST The electronic device of (1).

The buck-boost regulator shown in fig. 6 has an internal FET for switching. However, in other embodiments, other buck-boost regulators are utilized, including those with external FETs and/or diodes.

Similar to circuit 21, circuit 51 can be simplified if the forward voltage required to drive led d2 is low enough that V is _FLASH Less than the maximum operating voltage of the communication module 24. If this condition is satisfied, the following simplification is made for the power structure of fig. 6:

■V _BOOST fixation, V _BOOST ＝V _FLASH ＝V _COMMS . In this case, the voltage reference to the buck-boost converter is fixed, rather than controlled by control block 22.

■ Conditions 7 to 12 in table 1 are no longer required.

■ The fet q4 is no longer required. Referring to fig. 10, V of the communication module 24 ⁺ Is directly connected to V _SCAP 。

Briefly, some of the main advantages of embodiments of the present invention are:

■ A super-capacitive device is used at the output side of the regulator to supply a plurality of different voltages supplied by the regulator.

■ The peak current demand on the power source and regulator is reduced for a given load.

Accordingly, the actual area of the circuit board required by these components for a given load can be reduced.

The source circuit is controlled at any time, not only when the output voltage of the regulator is greater than the input voltage to the regulator.

Fig. 13 to 16 show embodiments of the invention in which a supercapacitor is connected in series with a battery.

Fig. 13 shows an embodiment of the invention in the form of a power supply 60, i.e. an alternative power supply for the cellular phone 2. In fig. 13, corresponding reference signs are used to denote corresponding features of fig. 3. In this embodiment, the supercapacitor 8 is connected in series with the battery pack 6. This embodiment is described with reference to a particular configuration in which the physical size of the power supply is minimized. In some embodiments, similar measures to minimize size are not taken along the same lines as power supply 60. That is, the general design option of positioning the supercapacitor 8 in series with the battery pack 6 is employed, but with alternate details.

The basic premise for the power supply 60 is that the battery pack 6 is always present and has a continuous power rating. As such, a load in need, such as circuit 4, should use this nominal battery power, and the super capacitive device should make up for the difference between it and the power needed by the load. In an effort to substantially achieve this, the supercapacitor 8 is connected in series between the battery pack 6 and the circuit 8. This method reduces the risk of stress on the battery 6 when compared to the known prior art and correspondingly reduces the risk of shortening the life time and the running time of the battery. In addition, voltage drops affecting the circuit are substantially avoided as a whole. In embodiments where the battery pack 6 includes overcurrent protection, the chance of tripping the built-in protection mechanism is also mitigated.

For the present exemplary embodiment, it is assumed that the effect of the supercapacitor 8 is not required for proper operation of the transmitter 3. That is, the battery pack 6 is relatively capable of powering the transmitter 3 and is typically only subjected to pressure in relation to the power supply circuit 4. It will be appreciated that this is one possible scenario: led flashes will be incorporated into already existing phone designs. Under such a concept, the supercapacitor 8 is used only in conjunction with the circuit 4-that is, the supercapacitor 8 need not be added to the emitter 3. The rationale is that in this particular example the emitter 3 is not sufficiently demanding to make the cooperation of the supercapacitor urgent. In embodiments other than this, the supercapacitor 8 or additional one or more supercapacitors are used to assist in providing the required voltage, current and/or power to the transmitter 3. It will be appreciated that this increases the physical size of the power supply.

The connection of each load to output 7 is selectable-transmitter 3 and circuit 4 are selectively connected to output 7 mutually exclusively through respective status switches 61 and 62 which travel between open and closed states. That is, when one of the emitter 3 and the drive circuit 4 is connected to the output 7, the other is not. The supercapacitor 8 is located between the switch 63 and the switch 61. When the circuit 4 is connected to the output 7, a further switch 63, which is activated to operate in synchronism with the switch 61, connects the supercapacitor 8 in series to the battery pack 6. As such, when the circuit 4 is energized, the supercapacitor 8 is connected in series with the battery pack 6, in series with the drive circuit 4, and in parallel with the output 7. As with other examples in this disclosure, certain switches are optionally not used in certain embodiments. One such example is to replace switch 62 with a short circuit.

In this embodiment, when the status switch 62 is closed, the supercapacitor 8 is isolated from the output 7. Thus, there is a reduced need for the battery pack 6 to supply leakage current of the supercapacitor 8 when the transmitter 3 is in use. This will increase the operating time of the battery pack.

As a further advantage of this embodiment, there is a relatively low voltage stress on the supercapacitor 8, since the required load voltage is compensated by the battery as well as the supercapacitor. In addition, the battery provides power, which allows the use of supercapacitors having a smaller capacitance than in certain other embodiments. It will be appreciated that certain of the above embodiments using a supercapacitor in parallel with the battery provide even further reduced pressure on the battery. In addition to this, the pressure on the battery in this embodiment is sufficient for modern acceptability concepts, especially in portable consumer electronics devices such as the phone 2.

In the above embodiments, the power supply may be selectively operated in a plurality of modes including:

■ A first mode in which the regulator 10 powers the transmitter 3.

■ A second mode, in which the regulator 10 charges the supercapacitor 8; and

■ A third mode, in which the supercapacitor 8 is discharged in order to power the circuit 4.

It will be appreciated that in this embodiment the supercapacitor 8 is isolated from the battery 6 in the first mode. In addition, the regulator 10 is isolated from the circuit 4 in the third mode. In addition, the transmitter 3 is isolated from the battery 6 in the second mode and the third mode. In some embodiments, the transmitter 3 is powered in the second and third modes, and there is a selection to interrupt the second and third modes during transmission by the transmitter 3.

Fig. 14 shows an alternative embodiment similar to the embodiment of fig. 13, which takes the form of a power supply 100. Similar to the circuit 60, the power supply 110 includes an input 5 for connection to a battery 6 and a super capacitor 8 in series with the battery 6. In addition, the power supply 110 includes two outputs, which are:

■ A first output 111 for connection to the transmitter 3.

■ A second output 7 for connection to the circuit 4.

While the regulator 10 charges the supercapacitor 8, another component in the form of a bypass circuit 112 is combined with the regulator 10 to define a regulator cell. The regulator unit is operable in a plurality of modes including:

■ A first mode in which the battery 6 powers the transmitter 3 through the bypass circuit. In this mode, the switch 115 is closed. It will be appreciated that the disconnect switch 115 isolates the transmitter 3.

■ A second mode in which the regulator 10 powers the transmitter 3. In this mode, switches 113 and 114 are closed and switch 116 is open to isolate circuit 4 from supercapacitor 8.

■ A third mode, in which the supercapacitor 8 is discharged, in order to power the circuit 4.

In this embodiment, the regulator unit is always used in the first mode. That is, the battery 6 continuously powers the transmitter 3. The second or third modes are mutually exclusive-such that charging and discharging are mutually exclusive events-but are used simultaneously with the first mode.

The power supply 110 generally has the same advantages as the power supply 60, however, the controller 9 is not required, resulting in additional cost and size advantages. The reason is that the regulator 10 does not need to provide a variety of different voltages and merely boosts the voltage provided by the battery 6 to a voltage that is capable of efficiently charging the supercapacitor 8 in line with the duty cycle of the circuit 4. It will be appreciated that the power supply 110 provides a relatively small and efficient solution to operating the circuitry 4 in conjunction with the transmitter 3 without imposing the problematic current requirements on the battery 6.

Fig. 15 and 16 show exemplary circuits 80 and 100 in which an ultracapacitor is connected in series with a battery. Circuits 80 and 100 are alternative circuits included in cellular telephones.

The circuit 80 includes two loads-an LED flash 81 and a communication module 82. The circuit 80 is powered by a lithium ion battery 83, but in other embodiments an alternative power source is used. The voltage booster 84 operates in conjunction with an inductor 85, a diode 86, a transistor 87, and resistors 88, 89, and 90 to provide the current necessary to generate the flash. The super capacitor 91 is connected in series with the battery 83. In this embodiment a single cell capacitor is used, however, in other embodiments alternative supercapacitive devices are used, such as multiple supercapacitors in series and/or parallel. The circuit 80 also includes a current control module 92 for the flash lamp 81, which operates in conjunction with a resistor 93 and a transistor 94.

In this particular example, the flash 81 draws about 2 amps at about 5.5V (including the voltage drop across the regulator unit — the actual voltage drop across the LED is close to 5 volts) to give a flash that is bright enough for the intended camera application. The regulating resistor 88 allows a low charging current to be selected, which is substantially below 2 amps. Reducing the charging current allows for a reduction in circuit size, provided that inductor 85, diode 86, transistor 87 can be physically small and have a low current rating.

Another advantage of a low charging current is that the chance of a significant drop in the battery voltage is reduced. This drop often creates problems for other parts of the circuit and is therefore beneficial to avoid.

The selection of the super capacitor 91 and power electronics and charging current is made according to the desired duty cycle of the flash lamp 81.

The location of the supercapacitor 91 eliminates the inrush current problem and, therefore, no additional current limiting circuitry is required as in the case of a typical boost circuit. It will be appreciated that there is room for savings in efficiency and the associated manufacturing costs should be reduced.

In this embodiment, the peak battery current is substantially equal to the load current of the flash lamp, i.e. 2 amps. In a typical boost design, the battery current should be greater than the load current according to the following equation:

where η is efficiency. In this example, V is expected _out = 5.5V _in =3.3 volts, η =0.85, I _out =2 amps, note that battery 83 is a lithium ion battery. Thus, the formula yields I _in Will be 3.92 anper. Those skilled in the art will appreciate that such an amount of battery current is generally unacceptable. In the use of alkaline batteries, which can be attributed to lower V _in The situation is even worse in the case of (a) - (b). Assume in this example that the peak battery current is acceptableThe example of this embodiment is more satisfactory at 2 amps.

It will be appreciated that the embodiment of fig. 14 provides a relatively small circuit that can be used to drive an LED flashlight in a mobile phone without substantial detrimental effect on the battery.

Circuit 100 differs from circuit 80 in that block 82 is used in conjunction with voltage booster 84. Specifically, the booster 84 is used in conjunction with an inductor 85, a diode 86, a transistor 87, and resistors 88, 89, and 90 to provide the current and voltage necessary for the respective loads. These loads include a flash 81 and a module 82, respectively. It will be appreciated that in the present embodiment, the booster 84 comprises a controller such that a plurality of different voltages are provided in response to one or more loads being energized.

Referring now to fig. 18, there is shown a camera cellular telephone 151 incorporating a prior art power supply in the form of a voltage regulator 152 having an input 153 and an output 154. A power source in the form of a lithium ion battery 155 provides a battery voltage to input 153 in the range of from about 4.2 volts (when fully charged) to about 3.3V (just before actually fully discharged). Regulator 152 provides a regulated voltage of approximately 3.8 volts to output 154. Regulator 152 operates in linear mode and boost mode when the battery voltage on input 153 is greater than or less than the regulated voltage, respectively. In other embodiments, regulator 152 is a buck regulator rather than a linear regulator, and as such, regulator 152 operates in a buck mode when the battery voltage on input 153 is greater than the regulated voltage.

Camera phone 151 includes, among other circuits, a GPRS power amplifier 156 that draws a peak current of 1 amp from output 154 when driving an associated antenna 157. The camera phone also includes an LED flash circuit 158 having a current controller 159 and an LED 160 between the output 154 and the controller 159. The controller includes an ENABLE input 161 that forward biases the LED 160 when held in a high state to allow a flash to be generated from the LED. In this embodiment, the controller 160 allows up to 350mA to flow through the LED 160 during flash generation. Accordingly, the regulator 152 provides a peak current of 1.35 amps, which translates to a battery current of 2 amps peak when the efficiency of the regulator is taken into account.

The skilled reader will appreciate that camera phone 151 contains another circuit than that shown in fig. 18. Such further circuitry is omitted in order to clearly focus on the two loads that have the most significant impact on peak battery current, namely amplifier 156 and circuitry 158.

Reference is now made to fig. 19, in which corresponding features are denoted by corresponding reference numerals. In particular, camera phone 151 does not contain a prior art power supply as provided in FIG. 18, but rather contains a power supply 165. Specifically, power supply 165 includes an input 166 connected to battery 155 to draw a load current. Peak battery current is limited to 2 amps or less for battery life and increased run time. The power supply 165 includes a first output 167 for connection to a first load in the form of an LED flash circuit 168, and a second output 169 for connection to a second load in the form of an amplifier 156.

The regulator 152 continues to operate in either the linear mode or the boost mode as in the prior art arrangement of fig. 18. Note, however, that the regulator only provides power and current to the amplifier 156. The voltage on output 169 is regulated at 3.8 volts and the peak current available to be drawn is 1.35 amps. Importantly, this peak current is greater than the peak current available to the amplifier 156 in the embodiment of fig. 18. Accordingly, the power supply 165 is able to provide more power to the amplifier 156 than in this example of the prior art, with the result of less call signal loss, better distance from the base station with which communication is being established, and better transmission in low signal areas such as elevators, trains, tunnels.

In embodiments where the battery current is suppressed below the above-described threshold of the 2 amp limit, the amplifier 156 may be allowed to draw more than 1.35 amps. For example, some GPRS amplifiers may require up to 2 amps, depending on their efficiency.

The power supply 165 comprises a regulator cell (in the form of a low current charge pump 170) in parallel with a super-capacitive device (in the form of a single cell super-capacitor 171). A super capacitor is connected in series between input 166 and output 167 and is selectively charged by pump 170 to power circuit 168 at a maximum voltage of 6.5 volts. (that is, the sum of the maximum battery voltage of 4.2 volts and the maximum supercapacitor voltage of 2.3 volts).

In this embodiment, pump 170 operates to fully charge supercapacitor 171, regardless of the state of charge of battery 155. That is, the supercapacitor is charged until the voltage difference between its electrodes is 2.3V. This has the advantage of simplicity, but will result in higher losses in the supercapacitor and may result in limiting the lifetime of the supercapacitor. In other embodiments, the supercapacitor 171 is charged such that the high voltage electrode is at a specified voltage. As the battery discharges, the voltage it provides changes, and therefore the voltage across the supercapacitor applied by the pump 170 will increase as the battery 155 discharges. In either case, the voltage across the supercapacitor is controlled to ensure that it remains within specification, otherwise the condition will be short lived.

The pump 170 includes an ENABLE input 172 that drives the pump 170 to charge the supercapacitor 171 when an appropriate voltage signal is applied.

The combination of the pump 170 and the supercapacitor 171 is capable of supplying the circuit 168 with a load current that peaks at about 2 amps and averages about 1.5 amps over a GPRS pulse period. In addition, this is done while simultaneously:

■ The battery current is suppressed to less than about 2 amps.

■ Amplifier 156 is operated to transmit the GPRS signal and draw a load current that peaks at about 1.35 amps and averages about 340mA over a GPRS pulse period.

It will be appreciated from the above description that amplifier 156 is operating for Class 10 transmission. That is, there is a 25% duty cycle on the peak current. In other embodiments, the other levels of emission are accommodated peaks (accommoded peaks).

Due to the increased available current capacity, the circuit 168 comprises two

LEDs

173 and 174 arranged in parallel with each other and in series with the current controller 159. The controller 159 is adapted to allow a current of a maximum predetermined maximum value to flow, thereby allowing a flash of light to be produced by the

LEDs

173 and 174.

The configuration of power supply 165 allows for the generation of a substantial flash of light without excessive use of battery 155, regardless of whether the cellular telephone functionality of camera phone 151 is being used. That is, the user of camera phone 151 does not need to stop talking to operate the flash function.

During normal operation of the cellular telephone function, regulator 152 provides amplifier 156 with the ability to draw up to 1.35 amps of peak current, which is sufficient to allow the desired communication signals to be transmitted, received and processed. In other embodiments, more than 1.35 amps are drawn by the amplifier 156 due to the efficiency of the amplifier.

Pump 170 charges supercapacitor 171, if needed, when a telephone call is not in progress, or if a call is in progress only when the amplifier is not drawing a peak current pulse. The latter case is described in detail below, and specifically, upon startup of camera phone 151, pump 170 begins to charge supercapacitor 171, thus maintaining the supercapacitor in a fully charged state. It is apparent that the supercapacitor 171 is at least partially discharged after the flash is provided.

In other embodiments, pump 170 begins charging supercapacitor 171 only when the user indicates that a flash from circuitry 168 will be needed or is likely to be needed, for example, when a camera function is selected from a menu on the camera phone visual display.

It will be noted from fig. 19 that line 172 is held low, that is, pump 170 is deactivated, while GPRS pulses are being generated by amplifier 156. However, for the remainder of the GPRS signal period, which in this embodiment is equal to 75% of the period, line 172 is held high and pump 170 is enabled and can charge supercapacitor 171.

Once the super capacitor 170 is charged (which in some embodiments will be instantaneous), the user can initialize the camera to take images. There are two possible modes of operation of camera phone 151 that are cellular phone functions being used simultaneously and not. Looking first at the situation where the cellular telephone is not in use, this will result in the non- (GPRS) condition of

lines

161 and 172 being true. The other condition for these two lines is the logical opposite, and accordingly, pump 170 is not active when current is flowing through

LEIDs

173 and 174 and controller 159. In this mode, the peak and average current drawn by the circuit 168 will be about 2 amps. That is,

diodes

173 and 174 draw approximately 1 amp each. An example of such a diode is the diode manufactured by Lumileds and known as PWF1, which has a manufacturer's recommended maximum current of 1 amp. Such a diode, as used in the embodiment of fig. 19, provides a large flash of light that greatly exceeds the arrangement in the prior art shown in fig. 18. Specifically, the embodiment in fig. 19 includes two such LEDs, each capable of being driven by a peak current of 1 amp.

In another mode, camera phone 151 is used simultaneously to capture an image and drive amplifier 156. After the logical input of

lines

161, 172, the operation is similar to that in the mode described above. Importantly, however, both

lines

161 and 172 go low during the GPRS pulse, that is, 25% of the time that amplifier 156 draws 1.35 amps. That is, for the time that amplifier 156 requires peak current, both pump 170 and circuit 168 are disabled and will draw very little if not zero current. During the other 75% of the cycle, when amplifier 156 draws much less current, line 161 is high and a flash of light is produced by

LEDs

173 and 174. Thus, during the period of the GPRS signal, the flash will be pulsed.

For the above example, even though the cellular phone function is being used, the average current available to produce the flash is about 1.5 amps (averaged over the period of a GPRS pulse), which is much larger than what is provided in the known, prior art. Specifically, in this mode, the embodiment of FIG. 19 provides a current of 430% greater than the prior art of FIG. 18, while simultaneously providing a current of 35% greater to amplifier 156. However, if reference is made to other modes of operation, that is, where cellular telephone functions are not being used simultaneously, the increase in current to the circuit 168 is even greater.

The above improvement is achieved by the following means:

■ The extra energy required by

LEDs

173 and 174 is stored in supercapacitor 171.

■

LEDs

173 and 174 are driven only when there is no GPRS transmission.

It will be appreciated by the skilled reader that pulsing the current to the LED (that is, pulsing the light provided as a flash) is acceptable because the CMOS exposure time of a typical CCD is on the order of about 100 to 200ms, and the time for the current to be pulsed off is only on the order of 4.6 ms. As the skilled reader will appreciate, the integral of the light intensity falling on the CMOS sensor (total light) rather than the instantaneous peak is important.

It will be noted from the description of the embodiment of fig. 19 that the cellular telephone circuit in the form of the amplifier 156 has a high priority and the flash circuit 168 has a low priority. Although the two loads can operate simultaneously-although the loads only mutually exclusively draw respective load currents, the supply current (i.e., the current drawn from battery 155) is suppressed by ensuring that the load current to circuit 168 is controlled. That is, when the load current (in this case, the peak load current) is drawn by amplifier 156, the load current to circuit 168 is reduced to substantially zero. That is, at any time, the supply current is kept below a predetermined threshold. For the case where both the high priority load and the low priority load demand load currents that would cause the threshold to be exceeded, the low priority load current is reduced. In other embodiments, the low priority load current is reduced to a fraction of the current that would be provided in the absence of the high priority load current.

In some embodiments, the regulator 152 is omitted and the power input to the amplifier 156 is connected directly to the battery output 166. During GPRS transfer, the charging of the super-capacitor 8 and/or the Flash Enable is interrupted so they do not draw current from the battery.

In a low cost embodiment, one of the

LEDs

173 and 174 is omitted. Even in these embodiments, the current available to the amplifier 156 is increased to 1.35A, and the remaining LEDs can be driven as high as the LED manufacturer allows. For known LEDs suitable for this application, a typical maximum is 1 amp peak at 75% duty cycle, giving an average current of 750 mA. This represents a 214% improvement (350 mA-750 mA) over the best prior art known to the inventors.

In a broader sense, the solution provided by the embodiment of fig. 19 is to efficiently share the battery current to allow for the simultaneous efficient use of both functions, which would otherwise require too much battery current. The GPRS circuit containing the power amplifier requires only 2 amps for 25% of the time and the power supply 165 is configured to ensure that it receives priority during this time. However, the other 75% of the time, the LED circuit accepts 2 amps. Once a flash is provided (and a corresponding photograph is taken), "75% of the time" to drive the flash circuit can be used to recharge the super-capacitor. In this embodiment, the supercapacitor is charged by a pump 170 providing about 100mA of charging current. However, in other embodiments, different charging currents are used. For completeness it is mentioned that in the embodiment of figure 19, when both camera and cell phone functions are used, the LED is pulsed at a duty cycle of 75% and the average light output will be 75% of the peak light output.

In other embodiments, the power supply 165 includes an additional supercapacitive device in the form of a dual cell supercapacitor (not shown) connected in parallel with the output 138 of the regulator 152. This additional supercapacitor functions similarly to the supercapacitor 8 in fig. 1. That is, the two structures of the embodiments of the present invention discussed below can be used in combination.

In more complex and expensive devices that capture higher quality images, the image capture system used is synchronized with LED pulsing. That is, if the pixel is not being captured, no LED current is supplied. This minimizes the energy storage requirements on the supercapacitor, allowing the use of smaller, thinner supercapacitors.

Fig. 20 shows an embodiment along a similar line as fig. 19, which takes the form of a power supply 180. The main difference is that in the embodiment of fig. 20, the battery 155 is free to drive the amplifier 156 without being impeded by the operation of the LED flash 181. That is, the primary, telecommunication aspects of camera phone 151 are not affected by the secondary, photographic aspects, at least insofar as LED flashes are concerned.

The power supply 180 includes an input 166 connected to the battery 155 for drawing a load current. The first output 182 is connected to a first load in the form of an amplifier 156. The second output 183 is connected to a second load in the form of an LED flash 181. A super capacitor 184 is connected to output 183 to charge the LED flash 181. A regulator unit 185 is connected to the input 166 to charge the supercapacitor 184.

The regulator 185 draws only a low current from the battery 155. The current magnitude is typically determined to be sufficient to allow timely charging of the supercapacitor 184 while substantially not creating pressure on the battery 155 above a predetermined threshold level. This notes the above mentioned constraints, e.g. that the battery current is limited to a maximum of 2 amps.

The function of this power supply is affected by signal 186. This signal provides two modes:

■ A first mode, in which switch 187 is opened such that the LED flash 181 is isolated and the regulator 185 is enabled to charge the super capacitor 184.

■ A second mode in which the switch 187 is closed so that the LED flash 181 is enabled and the super capacitor 184 discharges to power the flash. In this mode, the regulator 185 is deactivated so that it does not draw current from the battery 155. Thus, the LED flash 181 is solely powered by the discharge of the supercapacitor 184.

It will be appreciated that this approach effectively isolates the regulator 185, the super capacitor 184, and the LED flash 181 from the rest of the circuitry in the phone 151 during use of the LED flash 181. That is, the rest of the phone is not affected by the power requirements associated with flash use.

In a similar embodiment, regulator 185 remains enabled in the second mode. That is, in the second mode, the super capacitor 184 discharges to power the LED flash 181, while the regulator 185 continues to draw a low current to charge the super capacitor 184. In one such case, signal 186 operates to only affect switch 187.

The above embodiments use one or a combination of two power supply configurations:

■ A super-capacitive device located on the load side of the voltage regulator.

■ A super-capacitive device in series with the battery.

These structures can be used independently or in combination within one power source. For example, in one embodiment of the present invention, the power supply includes two loads that are powered by the circuits of the first and second configurations, respectively. It will be appreciated by the skilled reader that in certain embodiments there is a need to time share the power supply to the load, as occurs in the embodiment of figure 19, to prevent overloading of the associated power source.

The second configuration is preferably applied to a device having a battery (or other power source) capable of supplying a load current to a given load. Having the super-capacitive device in series with the battery allows the physical size of the super-capacitive device to be relatively small because it will be exposed to less than the full load voltage. That is, the voltage across the supercapacitive device (which may be a supercapacitor bank) will be smaller, and therefore, fewer series-connected supercapacitive cells are required for the supercapacitive device. In addition, less capacitance is required from the super-capacitive device because the current it carries is limited to the magnitude of the load current.

The above two configurations are suitable for many applications, but are particularly suitable for applications where the limitations in existing power supplies are relatively significant. In particular, the above structure provides substantial benefits when combined with the following loads demanded from the associated power source:

■ An average power that does not exceed the average power capability of the power source.

■ A peak power greater than a peak power capacity of the power source.

When these two conditions exist, the preliminary investigation is the current capability of the power source. If it is greater than or equal to the peak current required by the load, the second of the above structures is applied. However, if the current capacity of the power source is less than the peak current demand of the load, the first of the above structures applies.

The first architecture allows the use of a lower power battery (or other power source) and a smaller capacity voltage regulator for a given ripple powered load, and relative to a power supply without a super capacitor. The second configuration allows a greater peak power to be provided to the load for a given battery.

The embodiment exemplifies the above structure as applied to a low power device. Another example of a low power device is a type of electronic device that is powered by a low voltage (i.e., one or more cells) alkaline battery. Including portable sound reproduction devices such as MP3 players, CD players, radios, etc. Other specific examples of low power devices include digital cameras, digital camcorders, cellular telephones, PDAs, pagers, laptop computers. The invention is equally applicable to non-portable devices having pulsating current loads with limited power supply. For example, the present invention is applicable to powering loads within a desktop computer. Although the primary power supply of the computer is connected to the mains power supply, -in this example, the mains power supply is the "power source" and the primary power supply is the "power supply" throughout this specification-there are many components in the computer having a secondary power supply which draws power separately from the primary power supply and is limited in the amount of power and/or current. That is, if the reference point is the secondary power source, the primary power source becomes the "power source" as used in this description. Examples of electronic devices that include a secondary power source include DVD players, pcmcia cards, hard drives, or any device that is powered through a USB port of a computer. The replacement of the secondary power source with the power source according to the invention allows better use of the average power available from the primary power source.

The two configurations mentioned above are also suitable for medium and high power devices. Examples of such applications include UPS and drive systems for hybrid electric and electric vehicles.

Although the invention has been described with reference to specific examples, it will be appreciated by those skilled in the art that it may be implemented in many other ways.

Claims

1. A power supply for a cellular telephone, the telephone having a first load and an LED flash, the power supply comprising:

an input for connection to a power source;

a first output for connection to the first load;

a second output for connection to the LED flash;

a super-capacitive device connected to the second output to power the LED flash; and

2. The power supply of claim 1, wherein said regulator is in series with said power source and together they are in parallel with said supercapacitive device.

3. The power supply of claim 1, wherein the super-capacitive device is in series with the input such that the super-capacitive device is in parallel with the LED flash together with the power source.

4. The power supply of claim 1 adapted for use in a plurality of modes including:

a charging mode for charging the super-capacitive device; and

discharging for discharging the super capacitor to power the LED flash.

5. The power supply of claim 4, wherein the charge and discharge modes operate simultaneously.

6. The power supply of claim 4, wherein said charge and discharge modes selectively operate mutually exclusively.

7. The power supply of claim 4, wherein the first load is powered regardless of whether the power supply is in the charging mode or the discharging mode.

8. The power supply of claim 1, wherein the regulator unit limits the charging current of the supercapacitor to less than a predetermined value.

9. The power supply of claim 8, wherein the predetermined value is about 2 amps.

10. The power supply of claim 8, wherein the predetermined value is about 1 amp.

11. The power supply of claim 1, limiting the current drawn from the power source to less than a predetermined value.

12. The power supply of claim 11, wherein the predetermined value is about 2 amps.

13. The power supply of claim 11, wherein the predetermined value is about 1 amp.

14. The power supply of claim 1, wherein the first output limits the second output.

15. The power supply of claim 1, wherein the first output selectively limits the second output.

16. The power supply of claim 1, wherein the first load is a communication module.

17. The power supply of claim 1, wherein the first load is a power amplifier.

18. A power supply for an LED flash, the power supply comprising:

an input for connection to a power source;

an output for connection to the LED flash;

a super capacitive device connected to an output for powering the LED flash; and

19. A power supply for a plurality of loads drawing respective load currents I ₁ ，I ₂ ，……，I _N Wherein N is more than or equal to 2, the power supply comprises:

an input for connection to a supply voltage V providing a minimum source voltage _S The power source of (1);

an output for selectively connecting to one or more of said loads for providing a corresponding predetermined load voltage V ₁ ，V ₂ ，……，V _N Supplying the load current I ₁ ，I ₂ ，……， I _N Wherein V is ₁ ≠V ₂ ，……，V ₁ ≠V _N ；

A super-capacitive device in parallel with the output; and

a control circuit arranged between the input and the output for selectively switching V ₁ ， V ₂ ，……，V _N Is provided to the output.

20. The power supply of claim 19, wherein V ₁ ，V ₂ ，……，V _N One or more than one of V is ≧ V _S 。