AU1109601A - Power saving control circuit for supplying power to a load - Google Patents

Description

AUSTRALIA

Patents Act 1990 COMPLETE SPECIFICATION STANDARD PATENT Applicant(s): POWER SAVE ELECTRONICS PTY LTD COLLINS MELLODY A.C.N. 092 051 137 Invention Title: POWER SAVING CONTROL CIRCUIT FOR SUPPLYING POWER TO A LOAD The following statement is a full description of this invention, including the best method of performing it known to me/us: 2 POWER SAVING CONTROL CIRCUIT FOR SUPPLYING POWER TO A LOAD This invention relates to a power saving control circuit for supplying power to a load and relates particularly but not exclusively to a power saving control circuit for supplying power to lighting circuits in order to reduce power and energy demands.

Hitherto, the power being supplied to a load, such as lighting circuits, can be controlled by dimmer devices which normally use phase switching to achieve a reduction in the load voltage. Such dimmers generate electrical and RF noise which has its attendant regulatory compliance cost problems.

Other energy saving devices exist which involve voltage reduction. These include: 1. Electronic ballasts, which are fitted to individual light fittings for fluorescent and gas discharge lighting.

2. Switchable ballast inductors, designed for individual light fittings.

3. Multiple transformer devices for switchboard installation. These suffer from cost and efficiency 30 shortcomings.

4. Single transformer devices using mechanical or solid state switching to select a suitable transformer output voltage. These have switch reliability and cost problems, and switching times are critical. Light flicker can also be a problem.

83 8 POWERScopete-ntb. doc 8/01/01 3 The present invention attempts to overcome one or more deficiencies of the prior art.

Therefore according to the present invention there is provided: a power saving control circuit for supplying power to a load, said circuit having a input with an active and a neutral for connection with a power supply, and an outlet with an active and a neutral for connection with said load, said neutral of the input and said neutral of the output being electrically common, a voltage divider circuit with a voltage output connection, said voltage divider circuit connected to the active of the outlet for providing output to the load at a voltage lower than the voltage of the power supply at the input, said voltage divider circuit being connectable across the input active and neutral, :there being a first switch means connected in parallel across the active of the outlet, and that part of the voltage divider circuit connected to the active of the input, there being a second switch means connected in series between the neutral and that part of the voltage divider circuit to be connected to neutral, said first switch means being set to the normally closed condition when the load is OFF, said second switch means being set to the normally open condition when the load is OFF, said first switch means thereby permitting full supply voltage from said input to be supplied to said load H:\8uzanneg\Keep\peci\P40838pwFsAvcoplete-ntb.doc 8/01/01 4 when said load is ON, control circuit means connected with said first switch means and said second switch means and responsive when the load is being ON to switch said first switch means to the open condition and the second switch means to the closed condition, so that said load will initially receive the full power supply voltage from said input, and then said voltage lower than the voltage of the power supply at the input via said voltage divider circuit.

Most preferably said voltage divider circuit is an auto transformer with a tap of the auto transformer used for supplying voltage to the outlet active.

Most preferably said control circuit means is responsive to changes in current supplied to the load.

Most preferably the control circuit means is 20 responsive to voltage supplied to the load Most preferably the control circuit means is responsive to voltage across said second switch means.

ooo o 25 Most preferably said control circuit means is a microprocessor control circuit means.

Most preferably during supply of power to said load, said microprocessor control circuit means will operate to return 30 said first switch means to the normally closed condition in the event of the load current exceeding a threshold, thereby permitting full power supply voltage to be supplied from said input to said load output.

Most preferably said control circuit means is responsive to a voltage change across said load below a threshold to switch said first switch means to the normally H:\8uzanneg\Keep\Speci\P40838POYWFRSAVcomplete-ntb.doc 8/01/01 5 closed thereby permitting full power supply voltage to be supplied from said input to said output.

Most preferably said control circuit means effects switching of said first switch means to the open condition and the second switch means to the closed condition when the load reaches a stable operating condition following said load being initially ON.

Preferably the stable operating condition is signalled to said control circuit means by elapse of time following said load being initially ON.

Most preferably, the first switch means is switched OFF before said second switched means is switched

ON.

Most preferably a check is made by said control circuit means between switching OFF of said first switch means and switching ON of said second switch means to determine that said load is stable and only switching said second switching means to the ON condition if said load is stable.

25 In order that the invention can be more clearly ascertained an example of a preferred embodiment will now be described with reference to the accompanying drawings wherein: 30 Figure 1 is a block schematic circuit diagram of .a preferred power saving control circuit for supplying power to lighting fittings.

Figure 2 is a functionality flow diagram of the steps involved in the microprocessor control circuit means shown in Figure 1.

H:\suzanneg\Keep\Speci\P40838POWERSAVcomplete-ntb.doc 8/01/01 6 Referring now to the drawings there is disclosed a power saving control circuit particularly used for installation at a switch board and used to control a particular lighting circuit which includes many individual lighting fittings of the fluorescent lamp type.

It should be understood that the invention is not limited to a control circuit for installation at a switchboard for controlling a circuit such as a circuit containing many different lighting fittings. It should also be understood that the invention is not limited for use with lighting fittings. Individual control circuits could be supplied for only one load or the loads.

Similarly, the power saving control circuit may be utilised for any other electrical device or devices.

In the case of fluorescent lamp operation it is known that once the lamp has been ignited and is operating under stable conditions, the supply voltage can be reduced marginally with almost no perceptible visual change in light output. In the preferred example, the voltage is reduced by about 15%. If the load voltage is reduced by about 15% this translates to about a 30% savings in power.

Different lamp types require different reduced voltages and 25 in the case of a typical mercury vapour lamp it requires about 220 volts to provide a maximum of 16% light reduction. Thus, when utilising the invention, account *must be taken of the reduced voltage to be supplied and the system designed accordingly.

Referring to Figure 1 it can be seen that there is an input 1 to the power saving control circuit where mains input power can be supplied. The power saving control circuit has an outlet 3 to which a load can be connected. The load is typically a circuit containing many different individual light fittings which can each be individually switchable ON and OFF. Other loads are H:\suzanneg\Keep\speci\P4O838OeIsRAvconpete-ntb.doc 8/01/01 7 possible. The input 1 has an active connection 5 and a neutral connection 7. The outlet 3 has an active 9 and a neutral 11. The neutral 7 and the neutral 11 are electrically common.

The power saving control circuit also includes a voltage divider circuit 13. The voltage divider circuit 13 is typically an autotransformer, but maybe some other voltage dividing mechanism. The voltage divider circuit 13 has a voltage output connection 15 which connects to the active 9 of the outlet 3 and will be used for supplying output voltage at the outlet 3 which is lower than the voltage of the full power supply voltage from the input 1.

The voltage divider circuit 13 is connected with the active 5 by connection 17. The voltage divider circuit 13 is also connectable with the neutral 7/11 by connection 19.

A first switch means 21 of the normally closed type is connected in parallel across the active 9 of the outlet 3 and that part of the voltage divider circuit 13 that is connected to the active 5 of the input 1. In other words, the first switch means 21 connects across that part of the voltage divider circuit 13 that is connected to the active 5 and the voltage output connection A second switch means 23 of the normally open type is connected in series between the neutral 7/11 and that part of the voltage divider circuit 13 which is to be connected to the neutral 7/11 via connection 19.

Under no load conditions, the first switch means 21 is normally closed when the load is OFF. The second switch means 23 is normally open when the load is OFF.

Under the circumstances, when the load is connected to the outlet 3 and switched ON, full mains supply voltage will be supplied via the input 1 to the outlet 3. In other words, input 1 active 5 will connect through the first switch H:\suzanneg\Keep\Speci\P40838POWERSAVcomplete-ntb.doc 8/01/01 8 means 21 directly to the active 9 of the outlet 3. The neutral 7 of the input 1 is electrically connected with the neutral 11 of the outlet 3. Thus, when the load is initially electrically connected at the outlet 3 full input supply voltage will be supplied to the load.

A control circuit means 25 is connected with the first switch means 21 and the second switch means 23 and is responsive when the load is ON to switch the first switch means 21 to the open condition and the second switch means 23 to the closed condition, so that the load connected to the outlet 3 will initially receive full power supply voltage from the input i, and then because of the switching of the first and second switch means receive a voltage lower than the voltage of the power supply at the input 1 via the voltage divider circuit 13. In other words, the voltage divider circuit 13 will then be in circuit and supplying a reduced voltage to the outlet 3. In the initial condition, the voltage divider circuit 13 is not 20 connected electrically in circuit with the outlet 3.

ooooo Thus, when power is first applied, the power saving control circuit is in a D-activated mode and the first switch means 21 is in its default ON state, and full 25 supply voltage is applied to the load. After sufficient time has passed for normal load starting, and measured load power conditions show that the load is stable, a power saving mode can be entered where the control circuit means operates the first switch means 21 and the second switch means 23 to apply a reduced voltage to the outlet 3. With fluorescent lamps, the outlet voltage 23 can be lowered to 204 volts with about a 30% reduction in both power consumption and a 15% reduction in light output level. The reduction in light output level is barely perceptible by an observer. For fluorescent lamps a suitable time to be passed for normal load and stable operation conditions to be reached is in the order of approximately 10 seconds.

H:\suzanneg\Keep\Speci\P40838POWERSAvcomplete-ntb.doc 8/01/01 9 This figure is not critical and can be varied. The measured load power conditions are sensed by a current sensor 27 and a voltage sensor 29 which are connected in series with the outlet 3, and in parallel with the outlet 3 respectively. Each of the sensors 27/29 connect with a control circuit means 25. Thus, if the load is a lighting circuit containing many individual light fittings each independently switchable, and for example, the last and unlit light in the circuit is to be switched ON, the load voltage at that time may be too low for proper lamp starting. In that event, either the current sensor 27 or the voltage sensor 29 would sense a changed condition which is insufficient and would trip the first switch means 21 and the second switch means 23 so that full input supply voltage to the input 1 will be supplied to the outlet 3.

This, in turn, will then allow for proper starting of the last lamp in the circuit. After a set time and stable operating conditions, the power saving control circuit will then switch to effect the lower voltage supply at the outlet 3. In other words, if additional load is added, such that the load voltage is too low for proper lamp starting, full power operation is restored, and the start sequence repeated.

ooooi The charged condition sensed is that the voltage supplied to the output is too low for proper starting or that the current drawn from the output is too high.

Should there be failure of the switches 21/23 or 30 of the voltage divider circuit 13 or of the control circuit means 25, it will result in the power saving control circuit reverting to the initial condition where full input 1 voltage is supplied to the outlet 3.

A voltage sensor 31 is connected across the second switch means 23 to monitor voltage across the second switch means 23. This sensor 31 is connected with the H:\suzanneg\Keep\Speci\P4083 RSAVcomnpete-ntb.doc 8/01/01 10 control circuit means 25 with appropriate logic which determines if there is a voltage across the second switch means 23, then the second switch means 23 is open. This can signal a fault condition of the second switch means 23, or alternatively provide control instruction that the voltage divider circuit 13 is either fully in circuit or is out of circuit.

Fuses 33 and 35 are provided at various points in the power saving control circuit.

Typically the control circuit means 25 is an industrial quality microprocessor control circuit suitably programmed to perform the required functions.

Figure 2 shows the functionality in the process steps and will be self evident to a person skilled in the art with the necessary programming skills.

0* The control circuit means 25 may incorporate a :temperature detector device which may be used independently :or in conjunction with external temperature sensors using an analogue input sensing capability, to shut down the power saving control circuit to its initial default state 25 when excessive temperatures are reached. The voltage divider circuit 13 may also incorporate a thermal fuse for :added protection.

s If desired, options may be fitted to the power 30 saving control circuit for computation of load power and the energy saved. The load power and energy saved may then be displayed through a suitable display or reported remotely to some other location. Such may also be used with a remote control for use within building management systems and other remote devices. Figure 2 incorporates the functionality flow steps associated with these options and is self explanatory.

H:\suzanneg\Keep\speci\P4083gPOWERSAcomplete-ntb.doc 8/01/01 11 It should be understood that the switches shown may be mechanical or electronic or combined mechanical and electronic. Further, it should be appreciated that multiphase realisation could use a common microprocessor with separate voltage divider circuits for each phase.

Similarly, current and voltage sensing may be performed for each phase.

It should also be appreciated that with the circuit described above that if the supply voltage passes outside acceptable limits i.e. reduces due to "brown out", that this will be sensed by the voltage sensor 29 at the outlet 3 and full input supply voltage to the input 1 will then be provided by the circuit at the outlet 3 and applied to the load. This will permit the maximum possible supply voltage to be provided to the load under those circumstances.

20 Preferably, the power saving control circuit is located at a central switch board to control many lamps in a circuit and to avoid fitting at individual light fittings.

Known devices which reduce voltage, they are subject to introduction of flicker, and electrical noise, and are sensitivity to switching timings and reliability and have consequential dangerous and inconvenient failure modes. These have their attendant costs. In the power o. 30 saving control circuit of the preferred embodiment, the use of an auto transformer minimises these problems.

If desired, the first switch means 21 may be comprised of two different types of switches being electronic and also electromechanical which are connected in parallel so as to guarantee fail safe operation and zero power dissipation when in the closed condition.

H:\suzanneg\Keep\Speci\P4O838POWERSAcomplete-ntb.doc 8/01/01 12 The microprocessor forming a preferred implementation of the control circuit means 25 may be programmed to ensure sufficient voltage is maintained at the load at all times for acceptable light variation and proper lamp starting. The microprocessor may be interconnected with remote control systems and data delivery systems for providing either remote control of the power saving control circuit itself or to provide signals to other remote equipment.

It should be realised that with the power saving control circuit described, failure of the first switch means 21 or second switch means 23 or the control circuit means 25 cannot cause a hazard in those conditions or loss of power to the load as any failure in the devices will result in full input supply voltage being supplied to the outlet 3.

o 20 These and other modifications may be made without departing from the subject of the invention the nature of which is to be determined from the foregoing description.

00 H:\suzanneg\Keep\Specj\P4083 8 POWSAVcompete-ntb.doc 8/01/01

Claims (12)

1. A power saving control circuit for supplying power to a load, said circuit having a input with an active and a neutral for connection with a power supply, and an outlet with an active and a neutral for connection with said load, said neutral of the input and said neutral of the output being electrically common, a voltage divider circuit with a voltage output connection, connected to the active of the outlet for providing output to the load at a voltage lower than the voltage of the power supply at the input, said voltage divider circuit being connectable across the input active and neutral, there being a first switch means connected in parallel across the active of the outlet, and that part of the voltage divider circuit connected to the active of the input, there being a second switch means connected in series between the neutral and that part of the voltage divider circuit to be connected to neutral, said first switch means being set to the normally closed condition when the load is OFF, said second switch means being set to the normally open 30 condition when the load is OFF, 00 said first switch means thereby permitting full supply voltage from said input to be supplied to said load when said load is ON, control circuit means connected with said first switch means and said second switch means and responsive H:\suzanneg\Keep\Speci\P40838POWERSAVcomplete-ntb.doc 8/01/01 14 when the load is ON to switch said first switch means to the open condition and the second switch means to the closed condition, so that said load will initially receive the full power supply voltage from said input, and then said voltage lower than the voltage of the power supply at the input via said voltage divider circuit.

2. A circuit as claimed in claim 1 wherein said voltage divider circuit is an auto transformer with a tap of the auto transformer used for supplying voltage to the outlet active.

3. A circuit as claimed in claim 1 or claim 2 wherein said control circuit means is responsive to changes in current supplied to the load.

4. A circuit as claimed in any one of the preceding claims wherein the control circuit means is responsive to .voltage supplied to the load ooee

5. A circuit as claimed in any one of the preceding claims wherein the control circuit means is responsive to voltage across said second switch means. .Q•

6. A circuit as claimed in any one of the preceding claims wherein said control circuit means is a microprocessor control circuit means.

7. A circuit as claimed in any one of the preceding o 30 claims wherein during supply of power to said load, said *microprocessor control circuit means will operate to return said first switch means to the normally closed condition in the event of the load current exceeding a threshold, thereby permitting full power supply voltage to be supplied from said input to said load output.

8. A circuit as claimed in any one of the preceding H:\suzanneg\Keep\Speci\P40838POWE.RSAVcomplete-ntb.doc 8/01/01 15 claims wherein said control circuit means is responsive to a voltage change across said load below a threshold to switch said first switch means to the normally closed thereby permitting full power supply voltage to be supplied from said input to said output.

9. A circuit as claimed in any one of the preceding claims wherein said control circuit means effects switching of said first switch means to the open condition and the second switch means to the closed condition when the load reaches a stable operating condition following said load being initially ON. A circuit as claimed in claim 9 wherein the stable operating condition is signalled to said control circuit means by elapse of time following said load being initially ON. 9

11. A circuit as claimed in any one of the preceding D. 20 claims, the first switch means is switched OFF before said second switched means is switched ON.

12. A circuit as claimed in any one of the preceding claims wherein a check is made by said control circuit 25 means between switching OFF of said first switch means and switching ON of said second switch means to determine that said load is stable and only switching said second switching means to the ON condition if said load is stable. 9.9. H;\9uzanneg\Keep\Speci\P40838POWERSAvcomplete-ntb.doc 8/01/01 16

13. A Power Saving Control Circuit for Supplying power to a load substantially as herein described with reference to the accompanying drawings. Dated this 8th day of January 2001. POWER SAVE ELECTRONICS PTY LTD By their Patent Attorneys GRIFFITH HACK Fellows Institute of Patent and Trade Mark Attorneys of Australia 06 H:\suzanneg\Keep\speci\P40838POWF.sAvcomplete-ntb.doc 8/01/01