Abstract:
A power supply system and a method for providing power supply to electrical equipment from conventional lighting circuits in buildings are disclosed. The invention is intended to provide power supply to electrical equipment, without the need of conventional alternating current (AC) power supply power socket outlets. Instead, it obtains electrical power from existing lighting points. An embodiment of the invention is disclosed for achieving this without disrupting normal operation of turning on and off existing lighting sources. The present invention consists a wall switch unit and a lighting source control unit. The wall switch unit control s the level or waveforms of AC voltage supply to the lighting source control unit while the lighting source control unit detects the AC voltage level or waveforms for switching on or off a lighting source. Additionally, regardless of whether the lighting source is switched on or off, an uninterrupted power supply is derived from the lighting source control unit with this power supply being usable for electrically powering external electrical equipment connected thereto.

Description:
FIELD OF INVENTION 
       [0001]    The present invention generally relates to power supplies for electrical equipment. Specifically, the present invention relates to a power supply system for providing additional, uninterrupted power supply to electrical equipment from conventional lighting circuits in buildings. 
       BACKGROUND 
       [0002]    During installation of electrical wiring in a building, mains supply power socket outlets are typically positioned at locations where power requirement is anticipated. After the laying of the building&#39;s electrical wiring or construction is completed, it is generally difficult, inconvenient and costly to provide additional mains supply power socket outlets at alternative or additional locations within the building as the building&#39;s completed electrical wiring is embedded in conduits or within the walls of the building. 
         [0003]    With current advancements in technology, more electrical equipment and sensors are being produced for various applications in homes or buildings including security, communication, monitoring and remote controlling. As the electrical equipment and sensors require an electrical power supply for operation, installation of these electrical equipment and sensors in homes or buildings with completed electrical wiring requires the addition of new electrical wiring to the homes or buildings which poses great difficulty, inconvenience and cost to owners of the homes or buildings. In some applications such as installation of a security system, there may be numerous security equipment and sensors positionally scattered throughout the entire home or building that require power supply. The electrical wiring installation for these security equipment and sensors is not only costly but time consuming as well. 
         [0004]    Existing methods for installing additional electrical equipment in the homes or buildings include provision of electrical power supply to the additional electrical equipment by creating new electrical wiring from a position of the additional electrical equipment to a typical wall socket, which is cumbersome. 
         [0005]    From the foregoing problems, it is apparent that there is a need for a quick, convenient and less costly way to install additional electrical equipment and sensors in existing homes or buildings with existing electrical wiring without adding to or altering the existing electrical wiring or disrupting the normal use of lighting. 
       SUMMARY 
       [0006]    In accordance with a first aspect of the invention, there is disclosed a system for providing power supply to electrical equipments from conventional lighting circuits in buildings, the system comprising a detector, a converter and a power switching device. The detector is for receiving alternating current (AC) power supply having at least one property being detectable by the detector. The detector is for providing one of a plurality of control signals corresponding with the at least one property detectable by the detector. The converter is for converting the AC power supply into direct current (DC) power supply while the power switching device is for receiving the one of a plurality of control signals from the detector. The one of a plurality of control signals is for one of enabling and disabling switching of the power switching device for one of enabling and disabling flow of the AC power supply to an AC output. 
         [0007]    In accordance with a second aspect of the invention, there is disclosed a power supply method for providing power supply to electrical equipments from conventional lighting circuits in buildings, the power supply method comprising the step of receiving alternating current (AC) power supply by a detector whereby the AC power supply has at least one property detectable by the detector. This is followed by correlating the at least one property to one of a plurality of control signals by the detector. The next step is for providing direct current (DC) power supply whereby the DC power supply is converted from the AC power supply by a converter. This is followed by reception of the one of a plurality of control signals by a power switching device whereby the one of a plurality of control signals is for one of enabling and disabling switching of the power switching device for one of enabling and disabling flow of the AC power supply to an AC output. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]    Embodiments of the invention are described hereinafter with reference to the following drawings, in which: 
           [0009]      FIG. 1  shows a schematic of a conventional lighting circuit; 
           [0010]      FIG. 2  shows a functional circuit diagram of a power supply system according to a first embodiment of the invention when integrated into the conventional lighting circuit of  FIG. 1 ; 
           [0011]      FIG. 3  shows a functional circuit diagram of the power supply system of  FIG. 2  according to a second embodiment of the invention; 
           [0012]      FIG. 4  shows a diagram of an AC line voltage waveform with a first interrupted voltage waveform to initiate an ON state of the circuit in  FIG. 3 ; 
           [0013]      FIG. 5  shows a diagram of an AC line voltage waveform with a second interrupted voltage waveform to initiate an OFF state of the circuit in  FIG. 3 ; 
           [0014]      FIG. 6  shows a diagram of two AC line voltage waveforms with a third interrupted voltage waveform and a fourth interrupted voltage waveform to initiate the ON state and the OFF state, respectively, of the circuit in  FIG. 3 ; 
           [0015]      FIG. 7  shows a functional circuit diagram of the power supply system of  FIG. 2  according to a third embodiment of the invention; and 
           [0016]      FIG. 8  shows a diagram of a phase-chopped AC line voltage waveform to initiate an OFF state of the circuit in  FIG. 7 . 
       
    
    
     DETAILED DESCRIPTION 
       [0017]    A system and a method for providing additional, uninterrupted power supply to electrical equipment from conventional lighting circuits in buildings are described hereinafter for addressing the foregoing problems. 
         [0018]    In the detailed description provided hereinafter and in the several figures of the drawings, like elements are assigned with like reference numerals, analogous but changed elements are assigned like reference numerals accompanied by the letter “A”, and different elements are assigned different reference numerals. Reference is also made to two electrical states, an ON state and an OFF state. The ON state refers to the electrical state where a lighting source in a lighting circuit is being turned on while the OFF state refers to the electrical state where the lighting source is being turned off. 
         [0019]    A power supply system  200  according to a first embodiment of the invention for providing power supply to electrical equipment from conventional lighting circuits in buildings is described with reference to  FIG. 1  and  FIG. 2 .  FIG. 1  shows a schematic of a conventional lighting circuit  100  typically found in homes and buildings while  FIG. 2  shows a functional circuit diagram of the power supply system  200 .  FIG. 2  further shows the power supply system  200  integrated into the conventional lighting circuit of  FIG. 1 . 
         [0020]    The power supply system  200  as shown in  FIG. 2  comprises a wall switch unit  210  and a lighting source control unit  216 . The wall switch unit  210  functions as a controller, having a supply switch  212  and a capacitor  214  where the capacitor  214  is connected in parallel with the supply switch  212 . The lighting source control unit  216  comprises an AC-DC converter  218 , a voltage level detector  220 , a relay  222  and a transistor  224  that collectively function as a power switching device, and a minimum-load resistor  226 . The AC-DC converter  218  is coupled to the voltage level detector  220 , the relay  222  and the minimum-load resistor  226  while the collector of the transistor  224  is coupled to the relay  222  and the base of the transistor  224  is coupled to the voltage level detector  220 . The minimum-load resistor  226  can alternatively be connected across a supply path  228  and the mains supply Neutral wire instead of being coupled to the AC-DC converter  218 . Additionally, each of the AC-DC converter  218 , the voltage level detector  220 , the transistor  224  and the minimum-load resistor  226  is connected to a common ground or reference voltage. The wall switch unit  210  is connected to the lighting source control unit  216  via the supply path  228 . 
         [0021]    The wall switch unit  210  electrically interfaces mains supply Live wire  230  (hereinafter known as live wire  230 ) functioning as a power source and the supply path  228 . The live wire  230  provides alternating current (AC) power supply along the supply path  228  from which the voltage level detector  220  and the AC-DC converter  218  receive the AC power supply. The AC power supply has a property such as a voltage level. Examples of the voltage level include peak-to-peak voltage level and root-mean-square voltage level. The supply switch  212  is operable for enabling and disabling provision of the AC power supply from the live wire  230  along the supply path  228  via the supply switch  212 , when the supply switch  212  is in a closed state and an open state, respectively. The supply switch  212  can be a mechanical or an electronic device. The capacitor  214  is preferably of at least 330 nF and is for providing the AC power supply at reduced AC voltage level from the live wire  230  along the supply path  228  when the supply switch  212  is in the opened state. 
         [0022]    In the lighting source control unit  216  of the power supply system  200 , the AC-DC converter  218  converts the AC power supply that is received from the supply path  228  into direct current (DC) power supply. The AC-DC converter  218  provides the voltage level detector  220 , the minimum-load resistor  226  and the relay  222  with the DC power supply. The voltage level detector  220  detects the voltage level of the AC power supply and provides a control signal that corresponds with the voltage level. The power switching device receives the control signal provided by the voltage level detector  220  and can either enable or disable the flow of the AC power supply to an AC output, such as a lighting source  232 , depending on the control signal received. 
         [0023]    To initiate the ON state, the supply switch  212  is in the closed state and full AC power supply voltage level is supplied from the live wire  230  to the supply path  228  via the supply switch  212 . The voltage level detector  220  detects from the AC power supply a full voltage level and provides a first control signal that corresponds with the full voltage level. The transistor  224  energises the relay  222  by enabling the flow of the DC power supply from the AC-DC converter  218  through the relay  222  when the transistor  224  receives the first control signal provided by the voltage level detector  220 . The relay  222  then enables flow of the AC power supply to the lighting source  232  when the relay  222  is energised. The lighting source  232  is subsequently turned on by the AC power supply received from the supply path  228  via the relay  222 . 
         [0024]    To initiate the OFF state, the supply switch  212  is in the opened state and the reduced AC power supply voltage level is provided by the live wire  230  to the supply path  228  via the capacitor  214 . The voltage level detector  220  detects from the AC power supply a reduced voltage level and provides a second control signal that corresponds with the reduced voltage level. The transistor  224  receives the second control signal provided by the voltage level detector  220  and disables the flow of the DC power supply from the AC-DC converter  218  to the relay  222 . This de-energises the relay  222 , which in turn disables the flow of the AC power supply to the lighting source  232  and the lighting source  232  is then turned off. Additionally, when in the OFF state, the lighting source  232  is isolated from a node  234  as the relay  222  is de-energised and this prevents voltage at the node  234  from being pulled down by the lighting source  232 . 
         [0025]    A DC output  236  is coupled to the AC-DC converter  218  for receiving the DC power supply from the AC-DC converter  218  and is also connected to the common ground or reference voltage. The AC-DC converter  218  operates with the full AC power supply voltage level in the ON state and the reduced AC power supply voltage level in the OFF state to provide uninterrupted, continuous DC power supply to the DC output  236  during both the ON and OFF states. A first auxiliary device such as electrical equipment or a sensor can then be connected to the DC output  236  for drawing the uninterrupted, continuous DC power supply therefrom without being affected by the operation of turning on or off the lighting source  232 . 
         [0026]    Considerations must be taken to ensure proper functioning of the power supply system  200  of  FIG. 2 . The considerations include insufficient loading on the supply path  228  in the OFF state. When this happens, voltage level at the node  234  may rise to a high level such that it is difficult for the voltage level detector  220  to distinguish the OFF state from the ON state. The minimum-load resistor  226  prevents the above-mentioned situation from taking place as the minimum-load resistor  226  reduces the voltage level at the node  234 . As a result, the voltage level detector  220  receives a low voltage level and is able to distinguish the OFF state from the ON state. Another consideration includes a situation where there is exceeding DC loading. In this situation, the AC-DC converter  218  draws more AC power supply from the supply path  228  and there is an exceedingly large voltage drop across the capacitor  214 . A maximum loading condition is reached when the voltage level at the node  234  drops to a limit lower than that of the working voltage of the AC-DC converter  218 . The AC-DC converter  218  is preferably compatible for use in a 240V AC power supply system and capable of operating at a minimum level of 100V, and can provide 100-200 mA at a 12V DC output with the capacitor  214  preferably of at least 330 nF. This provides sufficient power for powering most small devices and sensors. 
         [0027]      FIG. 3  shows a functional circuit diagram of a power supply system  300  according to a second embodiment of the invention. The power supply system  300  comprises the wall switch unit  210  functioning as the controller, which consists of an electronic switch  310  instead of the supply switch  212  and the capacitor  214  as in  FIG. 2 . The electronic switch  310  preferably comprises an electronic circuitry having a power triac, a bridge circuit and a voltage limiting circuit, and a receiver (not shown). Suitable electronic circuitries are known in the art and exemplified in U.S. Pat. No. 6,281,604 B1 which is hereby incorporated by reference. The electronic switch  310  interrupts the voltage waveform of the AC power supply that the electronic switch  310  receives from the live wire  230  by phase chopping the voltage of the AC power supply in a specific pattern. The electronic circuitry determines the specific pattern of the interrupted voltage waveform of the AC power supply along the supply path  228  and the receiver receives signals such as infrared (IR) signals or radio frequency (RF) signals for controlling the wall switch unit  210 . The electronic switch  310  continuously provides the AC power supply from the live wire  230  along the supply path  228 . 
         [0028]    The lighting source control unit  216  of the power supply system  300  of  FIG. 3  comprises the AC-DC converter  218 , the relay  222  and the transistor  224  that collectively function as the power switching device, and an AC line interruption detector  220 A instead of the voltage level detector  220  as in  FIG. 2 . Further, the lighting source control unit  216  of the power supply system  300  does not comprise of the minimum-load resistor  226  as in  FIG. 2 . Additionally, each of the AC-DC converter  218 , the AC line interruption detector  220 A and the transistor  224  is connected to the common ground or reference voltage. The AC-DC converter  218  is coupled to the AC line interruption detector  220 A and the relay  222  while the collector of the transistor  224  is coupled to the relay  222  and the base of the transistor  224  is coupled to the AC line interruption detector  220 A. Similar to the circuit in  FIG. 2 , the wall switch unit  210  is connected to the lighting source control unit  216  via the supply path  228 . The AC-DC converter  218  provides the DC power supply to the AC line interruption detector  220 A. The AC line interruption detector  220 A detects the AC power supply having the interrupted voltage waveform and provides a control signal that corresponds with the interrupted voltage waveform of the AC power supply. 
         [0029]    To initiate the ON state, the electronic switch  310  provides a first interrupted voltage waveform, such as the AC line voltage waveform  400  in which two consecutive upper half cycles are phase chopped, as shown in  FIG. 4 . When the AC line interruption detector  220 A detects the first interrupted voltage waveform, the AC line interruption detector  220 A provides a first control signal that corresponds with the first interrupted voltage waveform. The transistor  224  receives the first control signal provided by the AC line interruption detector  220 A and enables the flow of the DC power supply from the AC-DC converter  218  through the relay  222 . This energises the relay  222  which enables the flow of the AC power supply to the lighting source  232 . The lighting source  232  is then turned on by the AC power supply provided by the supply path  228  via the relay  222 . 
         [0030]    To initiate the OFF state, the electronic switch  310  provides a second interrupted voltage waveform, such as the AC line voltage waveform  500  in which two alternate upper half cycles are phase chopped, as shown in  FIG. 5 . The AC line interruption detector  220 A, upon detecting the second interrupted voltage waveform, provides a second control signal that corresponds with the second interrupted voltage waveform. 
         [0031]    The transistor  224  receives the second control signal provided by the AC line interruption detector  220 A and disables the flow of the DC power supply from the AC-DC converter  218  through the relay  222 . This de-energises the relay  222  which disables the flow of the AC power supply to the lighting source  232 , hence, turning the lighting source  232  off. 
         [0032]    The AC line voltage waveforms  600  as shown in  FIG. 6  illustrate a third interrupted voltage waveform  610 , in which the rising half of an upper half cycle is phase chopped, and a fourth interrupted voltage waveform  612 , in which the rising half of two consecutive upper half cycles are chopped. The third interrupted voltage waveform  610  and the fourth interrupted voltage waveform  612  can also be used to initiate the ON state and the OFF state respectively. Besides the four interrupted voltage waveforms mentioned, the interrupted voltage waveforms can also take on other forms and can be arranged in a variety of sequence to initiate the ON state and the OFF state. The voltage of the AC power supply can also be interrupted by alternative techniques such as voltage clipping and voltage clamping. The AC line interruption detector  220 A can be of an appropriate design to detect the other forms of the interrupted voltage waveforms accordingly. 
         [0033]    An auxiliary output  312  is connected to the supply path  228  for receiving uninterrupted, continuous AC power supply provided by the supply path  228  in both the ON and OFF states. A second auxiliary device is connectible to the auxiliary output  312  and is able to receive the uninterrupted, continuous AC power supply provided by the auxiliary output  312  without being affected by the operation of turning on or off the lighting source  232 . The amount of power provided to the second auxiliary device  312  is limited by the wiring capacity in the power supply system  300  or that of the electronic switch  310 . The DC output  236  connected to the common ground or reference voltage as in  FIG. 2  can also be coupled to the AC-DC converter  218  for receiving the DC power supply from the AC-DC converter  218 . The first auxiliary device can then be connected to the DC output  236  for drawing the uninterrupted, continuous DC power supply therefrom without being affected by the operation of turning on or off the lighting source  232 . 
         [0034]    In order to ensure reliable functioning of the power supply system  300 , interrupted voltage waveform patterns used are preferably distinct from common interrupted voltage waveform patterns that commonly occur in any power supply system due to interference. The choice of chopped half cycles, such as the AC line voltage waveform  400 , the AC line voltage waveform  500  and the AC line voltage waveform  600  as shown in  FIG. 4 ,  FIG. 5  and  FIG. 6  respectively, offers a reliable performance against possible erratic operation arising from inherent spurious interrupted voltage waveform patterns in power supply systems. 
         [0035]    A power supply system  700  according to a third embodiment of the invention as shown in  FIG. 7  comprises the wall switch unit  210  and the lighting source control unit  216  as in the power supply system  200  of  FIG. 2  with the exception that the controller consists of the electronic switch  310  as in  FIG. 3  instead of the supply switch  212  and the capacitor  214 . Instead of initiating the OFF state using the reduced AC power supply voltage level to obtain the reduced voltage level as in the power supply system  200  of  FIG. 2 , the AC line voltage waveform  800  in which the beginning portion of each half cycle of the AC line voltage is phase chopped as shown in  FIG. 8  can also produce the reduced AC power supply voltage level needed to initiate the OFF state. 
         [0036]    Analogous to the power supply system  200  of  FIG. 2 , the DC output  236  is coupled to the AC-DC converter  218  for receiving the DC power supply from the AC-DC converter  218 . The AC-DC converter  218  provides the DC power supply to the DC output  236  during both the ON and OFF states and the first auxiliary device can then be connected to the DC output  236  for drawing the uninterrupted, continuous DC power supply therefrom without being affected by the operation of turning on or off the lighting source  232 . 
         [0037]    In the foregoing manner, a power supply system and a method for providing power supply to electrical equipment from conventional lighting circuits in buildings are described according to three specific embodiments of the invention for addressing the foregoing disadvantages of conventional methods. Although only three embodiments of the invention are disclosed, the invention is not to be limited to the specific forms or arrangements of parts so described and it will be apparent to one skilled in the art in view of this disclosure that numerous changes and/or modification can be made without departing from the scope and spirit of the invention.