GB2336044A

GB2336044A - Electrical power management converter

Info

Publication number: GB2336044A
Application number: GB9906898A
Authority: GB
Inventors: Raymond Collins; Andrew Peter Daniel
Original assignee: Raytek Components Ltd
Current assignee: Raytek Components Ltd
Priority date: 1998-03-26
Filing date: 1999-03-26
Publication date: 1999-10-06
Anticipated expiration: 2019-03-26
Also published as: GB9906898D0; GB9806415D0; GB2336044B

Abstract

In an electrical power management converter 10 having a switch 16 controlled by a control circuit 18 for periodically actuating the switch 16, an energy storage means, in the form of a reactive arrangement 20 is provide between the switch 16 and a load 14 such that the reactive arrangement stores power while a supply is enabled and discharges power to the load 14 while the supply is disabled, thereby adding to the period during which power is supplied to the load. The power to the converter is managed under control of a comparator 26 which compares the voltages from loads 14a-14e with a reference such as the supply voltage Vs. The output from the comparator determines the frequency of a VCO 28 so as to provide pulses (34a-34e, Fig 3) via outputs 36a-36e of a demultiplexer 30 to switch transistors 16a-16e in sequence and supply the loads 14a-14e. The loads may be heaters, lighting, TV's and cookers for use in caravans, boats and mobile homes.

Description

1 Flectrical Power Management Apparatus 2336044 This invention relates to

electrical power management apparatus, particularly but not exclusively electrical power management apparatus for use with a non-mains electrical supply.

Conventionally, where the use of a mains AC electrical supply is not available a battery or a photovoltaic cell solar panel is used to provide a DC electrical supply. These supplies have limitations in their use due to the fixed amount of power which they can supply, and this restricts the electrical load which can be driven by the supply. For example, the increasing provision of electrical appliances, such as heaters, lighting, televisions, cookers, and microwave ovens, in caravans, boats and mobile homes, has led to the electrical power demand often being greater than the power available from the supply.

According to the present invention there is provided electrical power management apparatus for managing the electrical power provided from an electrical supply to an electrical load when the apparatus is in communication with the supply and the load, the apparatus comprising: a switch means; control means for periodically actuating the switch means to thereby periodically enable power to be supplied to the load; and energy storage means provided between, and in communication with, the switch means and the load, the energy storage means storing power while the supply is enabled and discharging power to the load while the supply is disabled, thereby adding to the period during which power is supplied to the load.

The energy storage means is preferably a reactive electrical component assembly.

Preferably the apparatus is able to supply a plurality of loads. The apparatus preferably enables a plurality of loads to be powered from a supply of a lower power capacity than the combined power rating of the loads.

2 The reactive electrical component assembly preferably fully discharges over a period which is greater than the period during which the supply is disabled, thus the reactive electrical component assembly does not fully discharge before the supply is re-enabled and power is therefore substantially continuously provided to the load.

The reactive electrical component assembly preferably includes one or more inductors, or may include one or more capacitors. Desirably, the assembly includes both an inductor and a capacitor, preferably arranged in a known LC circuit arrangement. The inductor and capacitor values are preferably suitable for producing a voltage and/or current decay curve, as the inductor and capacitor discharge, having a predetermined decay characteristic such that the inductor and capacitor do not fully discharge before the supply is re-enabled.

Alternatively, a resistor and a capacitor may be used in a known RC circuit, a resistor and an inductor may be used in a known RL circuit, or a resistor, an inductor and a capacitor may be used in a known RLC circuit.

The switch means preferably includes an electrical switch, and desirably includes a semiconductor transistor device. The transistor may be an npn transistor. Preferably a plurality of switches are provided. Preferably each switch is able to communicate with a respective load. The switches are desirably provided as an array of switches. The array preferably has one electrical input, for communication with the supply, and an electrical output from each switch, the input being routed to an output according to which switch is actuated. Desirably only one switch may be actuated at any given time, hence the input is routed to a single output.

The switches are preferably actuable by the control means according to a predetermined pattern, and are desirably actuable in serial rotation. The period during which a switch is actuated, and the frequency at which the switch is actuated and deactuated, are preferably variable. The switch actuation frequency is desirably controlled by the control means. Preferably the switch 3 actuation frequency is dependent upon the variation in the power level supplied to a load. The switch actuation frequency is desirably dependent upon the variation in the voltage supplied to the respective load. The actuation frequency preferably varies in response to a change in the load voltage such that the load voltage tends towards a predetermined threshold value.

The switch actuation frequency is preferably set by the control means comparing the load voltage with a reference voltage. The reference voltage is desirably the supply voltage, or may be a fraction of the supply voltage.

The control means preferably comprises a comparator means for comparing the load voltage with the supply voltage. The comparator means desirably produces an output voltage which is dependent upon the difference between the load voltage and the supply voltage. The control means preferably further comprises an electrical signal generator in communication with the comparator means output. The electrical signal generator is desirably a voltage controlled oscillator device, the frequency of the voltage controlled oscillator output signal being dependent upon its input voltage, namely the comparator output voltage. The electrical signal generator may alternatively or additionally comprise a voltage to frequency converter.

The control means preferably further comprises a demultiplexing means in communication with the voltage controlled oscillator output for dividing the oscillator output signal into a plurality of lower frequency signals. The frequency of the voltage controlled oscillator output signal is preferably divided by the number of switches in the switch means. The number of lower frequency signals is desirably equal to the number of switches. Each lower frequency signal is desirably spaced in time with respect to each other such signal. Each output signal from the demultiple) means is preferably connected to one switch. When the switch is a transistor, most preferably to the base of the transistor. The time delays applied to the lower frequency signals are preferably suitable to ensure that only one transistor is actuated at any one time. The transistors are desirably actuated sequentially.

4 A specific embodiment of the invention will now be described by way of example only, with reference to the accompanying drawings, in which:

Figure 1 is a schematic representation of an electrical power management apparatus, in communication with a supply and a load, according to the present invention; Figure 2 is a diagrammatic representation of the electrical circuit of the apparatus of Figure 1 in communication with five loads; and Figure 3 is a diagrammatic representation of an output signal from a voltage controlled oscillator used in the apparatus of Figure 1 and of the output signals from a demultiplexer used in the apparatus of Figure 1.

Referring to the drawings there is provided electrical power management apparatus 10, shown in communication with an electrical supply 12 and an electrical load 14. The apparatus 10 comprises a switch means 16 in communication with a control means 18 for periodically actuating the switch means 16 to thereby periodically enable power to be supplied to the load 14..An energy storage means, in the form of a reactive arrangement 20 is provided between, and in electrical communication with, the switch means 16 and the load 14. The reactive arrangement 20 stores power while the supply is enabled and discharges power to the load 14 while the supply is disabled, thereby adding to the period during which power is supplied to the load 14.

Referring to figure 2, the supply 12 is in electrical communication with the switch means 16 which, in this example, comprises an array of five npn semiconductor transistors 16a-16e. The supply 12 is connected to the collector of each transistor 16a-16e. The emitter of each transistor 16a16e is in electrical communication with a reactive arrangement 20, which in this example comprises a series inductor 22a-22e and a parallel capacitor 24a-24e arranged in a known LC circuit 20a-20e. Five loads 14a14e are connected to the common terminal of their respective LC circuits 20a-20e.

The control means 18 comprises a comparator 26 in electrical communication with an electrical signal generator in the form of a voltage controlled oscillator NCO) 28. The WO 28 is in electrical con-ununication with a demultiplexing means 30. The output from the comparator 26 forms the input to the VCO 28, and the output from the WO 28 forms the input to the demultiplexer 30.

The comparator 26 output voltage (Vc) is determined by comparing the voltage (VL) at one or more loads 14a-14e with a reference voltage, such as the supply voltage (V,) or a fraction of the supply voltage. The voltage of the VCO 28 input determines the frequency of the WO output signal 32. The WO output signal 32 comprises a pulse train, as shown for example in Figure 3. The comparator output VC forms the input to the VCO 28 and hence controls the frequency of the VCO output signal 32. In this example, the frequency of the pulse train is proportional to the input voltage VC In this example, the demultiplexer 30 comprises a one-to-five switch which selectively connects the demultiplexer 30 input to one of five output lines 36a-36e. The input is connected to each output 36a-36e in serial rotation. The switch moves from one output 36a-36e to the next output following receipt of a VCO output signal 32 pulse. The demultiplexer 30 thereby divides the VCO output pulse train 32 frequency by the number of transistors 16a-16e, in this case five, to provide five lower frequency pulse trains, each having a frequency of one-fifth of the VCO output 32 frequency. The five demultiplexed -signals 34a-34e are thus delayed with respect to one another, such that only one signal is high at any one time, thereby providing five time separated control signals 34a34e, one for each output line 36a-36e. Figure 3 shows an example output signal 32 from the VCO 28 and the corresponding five control signals 34a34e from the demultiplexer 30.

Each of the five outputs 34a-34e from the demultiplexer are in electrical communication, via the output lines 36a-36e, with the base of a respective one of the transistors 16a-16e. Each control signal 34a-34e therefore controls the actuation of the respective transistor 16a-16e. When the control signal 34a-34e is high, i.e. when a pulse is present, the selected transistor 16a-16e becomes 6 conducting, thereby enabling current to flow through that transistor 16a- 16e. Power is thus provided to a load 14a-14e when the corresponding control signal 34a-34e is high.

As can be seen from figure 3, the control signals 34a-34e become high one after the other in a serial rotation, namely 34a, 34b, 34c, 34d, 34e etc. The corresponding transistors 16a-16e are therefore actuated in a serial rotation, namely 16a, 16b, 16c, 16d, 16e etc, and the power supply to the respective loads 14a-14e is thus enabled in a serial rotation.

When VL is equal to a preset threshold voltage, in this example 11.35V, there will be a predetermined voltage difference between VL and the reference voltage i.e. the supply voltage VS VC will thus have a predetermined value, hence the frequency of the VCO 28 output pulse train 32 will also have a predetermined value and the transistors 16a-16e will be actuated in serial rotation at a predetermined rate. When the apparatus 10 is switched on, the VCO output pulse train 32 frequency adopts the said predetermined value. Hence when the apparatus 10 is initiated it operates at its predetermined optimum values.

Should the transistor actuation rate fall below the desired rate, the transistors 16a-16e will be deactuated, i.e. off, for a longer period of time than desired. The LC circuit will therefore discharge further than desired and the power supply level to the loads 14a-14e will fall below the optimum level. The value of V. will therefore fall and hence the difference between VL and the reference voltage will change. The change in this voltage difference will result in the value of VC changing, in this case increasing, and hence the frequency of the VCO 28 output signal 32 will also increase. The transistor actuation rate will therefore rise towards the predetermined desired rate and the transistors will thus be off for a shorter period. As a result, a given LC circuit will discharge less during deactuation of the respective transistor 16a-16e and the power level supplied to the corresponding load 14a-14e will therefore rise towards the predetermined threshold value. Hence, the apparatus 10 will 7 return to its optimum settings.

Similarly, if the transistor actuation rate rises above the predetermined level, the LC circuit will not discharge far enough and VL will be higher than the optimum value. The control means 18 will therefore act to reduce the transistor actuation rate, and hence V,, back towards the predetermined optimum value.

The comparator 26, WO 28 and demultiplexer 30 therefore form a feedback circuit which acts to maintain the transistor actuation rate and V. at their predetermined optimum levels.

The apparatus 10 may be used to power a plurality of, in this case five, loads 14a-14e from a supply 12 which has a lower power capacity than the combined power rating of the loads 14a-14e, due to the cyclical provision of power supply to the loads 14a-14e. During actuation of a selected transistor 16a-16e power from the supply 12 is provided to the corresponding load 14a14e. During deactivation of a selected transistor 16a-16e, the corresponding LC circuit 20a-20e discharges power to the respective load 14a-14e, thereby extending the time period during which power is supplied to the load 14a-14e. Therefore each load 14a-14e is provided with power during each actuation of the corresponding transistor 16a-16e and is provided with a generally lower, decaying power supply from the respective LC circuit 20a-20e while the transistor 16a-16e is off.

Depending upon the nature of the loads 14a-14e, the power dissipation characteristics of the loads 14a-14e may assist in maintaining power output from the loads 14a-14e. For example, if the loads 14a-14e comprise a heater 14a, two lamps 14b, 14c, an oven 14d and a kettle 14e, the thermal characteristics of the devices will result in the heater 14a, oven 14d and kettle 14e elements radiating heat and the lamp 14d, 14c filaments emitting light even when the power supplied to them is much lower than their power rating, or no power is supplied at all. The loads 14a-14e will therefore appear to be working 8 continuously even though their power supply is not at a constant level.

There is thus provided electrical power management apparatus for managing the electrical power provided from a supply to a load. As will be appreciated, the apparatus enables a plurality of loads to be powered by a supply which has a lower power capacity than the combined power rating of the loads. The apparatus may be of particular use in a caravan, boat, mobile home or the like where only a low power supply, such as a battery or photovoltaic cell solar panel, is available. The apparatus may also be used with a rectified AC electrical supply.

It will be appreciated that the apparatus of the present invention may reduce the amount of power required to operate an appliance, such as any of the above. In the case of a battery supply, this will lead to a longer battery life.

Various modifications may be made without departing from the scope of the invention. For example, the control means may be of a different construction to that described and may be any device which is suitable for altering the switch actuation frequency in response to a change in the load voltage. The switch means maybe a different type of electrical switch, such as a pnp transistor or another semiconductor switch device. A greater or smaller number of switches and/or loads may be provided. A load may be connected to more than one switch in order to increase the time period during which power is supplied to the load. The reactive components may be provided in a different known circuit arrangement, such as an RI-C circuit including a resistor. An RC circuit or an RL circuit may be used in place of any LC circuit.

Whilst endeavouring in the foregoing specification to draw attention to those features of the invention believed to be of particular importance it should be understood that the Applicant claims protection in respect of any patentable feature or combination of features hereinbefore referred to and/or shown in the drawings whether or not particular emphasis has been placed thereon.

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Claims

1. Electrical power management apparatus for managing the electrical power provided from an electrical supply to an electrical load when the apparatus is in communication with the supply and the load, the apparatus comprising: a switch means; control means for periodically actuating the switch means to thereby periodically enable power to be supplied to the load; and energy storage means provided between, and in communication with, the switch means and the load, the energy storage means storing power while the supply is enabled and discharging power to the load while the supply is disabled, thereby adding to the period during which power is supplied to the load.

2. Apparatus according to claim 1 in which the energy storage means is a reactive electrical component assembly.

3. Apparatus according to claims 1 or 2 in which the apparatus is able to supply a plurality of loads.

4. Apparatus according to claim 3 in which the apparatus enables a plurality of loads to be powered from a supply of a lower power capacity than the combined power rating of the loads.

5. Apparatus according to any of claims 2 to 4 in which the reactive electrical component assembly fully discharges over a period which is greater than the period during which the supply is disabled, thus the reactive electrical component assembly does not ftWy discharge before the supply is re-enabled and power is therefore substantially continuously provided to the load.

6. Apparatus according to any of claims 2 to 5 in which the reactive electrical component assembly includes one or more inductors.

7. Apparatus according to any of daims 2 to 5 in which the reactive electrical component assembly includes one or more capacitors.

8. Apparatus according to any of claims 2 to 7 in which the assembly includes both an inductor and a capacitor.

9. Apparatus according to claim 8 in which the inductor and capacitor are arranged in a known LC circuit arrangement.

10. Apparatus according to claims 8 or 9 in which the inductor and capacitor values are suitable for producing a voltage and/or current decay curve, as the inductor and capacitor discharge, having a predetermined decay characteristic such that the inductor and capacitor do not fully discharge before the supply is re-enabled.

11. Apparatus according to any of claims 2 to 5 in which a resistor and a capacitor are used in a known RC circuit.

12. Apparatus according to any of claims 2 to 5 in which a resistor and an inductor are used in a known RL circuit.

13. Apparatus according to any of claims 2 to 10 in which a resistor, an inductor and a capacitor are used in a known RI-C circuit.

14. Apparatus according to any preceding claim in which the switch means includes an electrical switch.

15. Apparatus according to claim 14 in which the switch means includes a semiconductor transistor device.

16. Apparatus according to claim 15 in which the transistor is an npn transistor.

17. Apparatus according to any preceding claim in which a plurality of switches are provided.

18. Apparatus according to claim 17 in which each switch is able to communicate with a respective load.

19. Apparatus according to claims 17 or 18 in which the switches are provided as an array of switches.

20. Apparatus according to claim 19 in which the array has one electrical input, for communication with the supply, and an electrical output from each switch, the input being routed to an output according to which switch is actuated.

21. Apparatus according to claim 20 in which only one switch may be actuated at any given time, hence the input is routed to a single output.

22. Apparatus according to any of claims 1 71 to 21 in which the switches are actuable by the control means according to a predetermined pattern.

23. Apparatus according to claim 22 in which the switches are actuable in serial rotation.

24. Apparatus according to any of claims 14 to 23 in which the period during which a switch is actuated, and the frequency at which the switch is actuated and deactuated, are variable.

25. Apparatus according to claim 24 in which the switch actuation frequency is controlled by the control means.

26. Apparatus according to claims 24 or 25 in which the switch actuation frequency is dependent upon the variation in the power level supplied to a load.

27. Apparatus according to any of claims 24 to 26 in which the switch 12 actuation frequency is dependent upon the variation in the voltage supplied to the respective load.

28. Apparatus according to claim 27 in which the actuation frequency varies in response to a change in the load voltage such that the load voltage tends towards a predetermined threshold value.

29. Apparatus according to claims 27 or 28 in which the switch actuation frequency is set by the control means comparing the load voltage with a reference voltage.

30. Apparatus according to claim 29 in which the reference voltage is the supply voltage.

31. Apparatus according to claim 29 in which the reference voltage is a fraction of the supply voltage.

32. Apparatus according to claims 30 or 31 in which the control means comprises a comparator means for comparing the load voltage with the supply voltage.

33. Apparatus according to claim 32 in which the comparator means produces an output voltage which is dependent upon the difference between the load voltage and the supply voltage.

34. Apparatus according to claim 33 in which the control means further comprises an electrical signal generator in communication with the comparator means output.

35. Apparatus according to claim 34 in which the electrical signal generator is a voltage controlled oscillator device, the frequency of the voltage controlled oscillator output signal being dependent upon its input voltage, namely the comparator output voltage.

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36. Apparatus according to claims 34 or 35 in which the electrical signal generator comprises a voltage to frequency converter.

37. Apparatus according to claims 35 or 36 in which the control means further comprises a demultiplexing means in communication with the voltage controlled oscillator output for dividing the oscillator output signal into a plurality of lower frequency signals.

38. Apparatus according to claim 37 in which the frequency of the voltage controlled oscillator output signal is divided by the number of switches in the switch means.

39. Apparatus according to claims 37 or 38 in which the number of lower frequency signals is equal to the number of switches.

40. Apparatus according to any of claims 37 to 39 in which each lower frequency signal is spaced in time with respect to each other such signal.

41. Apparatus according to any of claims 37 to 40 in which each output signal from the demultiplexing means is connected to one switch.

42. Apparatus according to claim 41 in which when the switch is a transistor, to the base of the transistor.

43. Apparatus according to claim 42 in which the time delays applied to the lower frequency signals are suitable to ensure that only one transistor is actuated at any one time.

44. Apparatus according to claim 43 in which the transistors are actuated sequentially.

45. Electrical power management apparatus substantially as described above with reference to the accompanying drawings.

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46. Any novel subject matter or combination including novel subject matter disclosed herein, whether or not within the scope of or relating to the same invention as any of the preceding claims.