AU643504B2 - Electrical power control means - Google Patents

Description

643504 Form COMMONWEALTH OF AUSTRALIA PATENTS ACT 1952-62 COMPLETE SPECIFICATION

(ORIGINAL)

FOR OFFICE USE: Application Number: Lodged: Complete Specification Lodged: Accepted: Published: Priority: Related Art: Class Int. Class Name of Applicant: Adaress of Applicant: Actual Inventor: Address for Service: TO BE COMPLETED BY APPLICANT GERARD INDUSTRIES PTY LTD 12 Park Terrace, Bowden, South Australia, Australia PETER MICHAEL STOCK Care of R K MADDERN ASSOCIATES, 345 King William Street, Adelaide, South Australia, 5000 Complete Specification for the invention entitled: "ELECTRICAL POWER CONTROL MEANS" The following statement is a full description of this invention, including the best method of performing it known to me.us.

1- FIELD OF THE INVENTION This invention relates to the control of power delivered to selected electrical loads in an alternating current circuit where more than one load may be controlled over an existing switched active cable independently of other loads connected to the same cable.

BACKGROUND OF THE INVENTION New electrical loads are often difficult to add to existing buildings because of the problems associated with running new cables to the control switches for those new loads.

Many loads also require control of the power level delivered to the load, as for example when dimming an incandescent light or changing the speed of ceiling sweep fans. It is an object of this invention to address the problem of simultaneously switching loads and providing power control to selected loads.

BRIEF DESCRIPTION OF THE INVENTION In its broadest form the invention comprises an electrical power control signal circuit means in an alternating current circuit to indicate to a power control means the amount of power to be applied to an electrical load, said signal circuit means comprising, at least one variable passive circuit component which modifies a single polarity current signal, a detection means in series with said passive circuit component to detect the single polarity current and modification made thereto by the passive circuit component and provide an output signal indicative of the amount of power to be applied to said electrical load.

BRIEF DESCRIPTION OF THE DRAWINGS An embodiment of the invention is described hereunder and shown in'the following figures, such that: Fig 1 depicts a power control circuit means for two loads, Fig 2 depicts an averaging circuit embodiment of a power control circuit, Fig 3 depicts an application of the power control circuit means, 2 Fig 4 depicts a further embodiment of a power control circuit means incorporating a further embodiment of a signal detection means, Fig 5 depicts yet a further embodiment of a power control means, and Fig 6 depicts an embodiment of a solid state switch means suitable for the circuit of Fig. As shown in Fig 1 a first load power adjustment signalling device 10 for load 1 is connected in parallel with a second load power adjustment signalling device 11 for load 2 at the normal wall switch location. Devices 10 and 11 are located in series with two wires, the active 12 and a switched active 13 of a ceiling mounted load. These two wires are generally existing parts of a standard active and switched active electrical installation for one of a lighting or other alternating current driven load, and the two power adjustment devices 10 and 11 would simply replace an existing 1 single load control switch to provide power control for two separately controllable loads. As shown in Fig 1, the load power adjustment signalling devices (10 and 11) comprise a master switch S10, in series with a diode D10 and potentiometer RV10. This configuration of discrete electrical elements is simple to manufacture and occupies very little space so that it may be easily incorporated into existing switch mouldings and fittings since passive components do not require external power sources to operate and are generally compact or can be easily made so.

The main control unit, 14 may be mounted in an accessible ceiling space or other convenient access location preferably adjacent to the loads 1 and 2.

S As can be seen in Fig 1, sub-blocks 15 and 16 have identical circuit functional blocks. The only difference between the two is the orientation of the control diodes, 17 and 18. These diodes determine that sub-block 15 responds only to positive half wave rectified control signals (and thereby to load power adjustment signalling device 10 only), and sub-block 16 responds only to negative half wave rectified control signals (and thereby to load power adjustment signalling device 11 only).

3 The electronic circuitry within sub-blocks 15 and 16 may be designed to achieve the required function in a very wide variety of ways by those skilled in the art. The circuitry described and shown in Fig 2 is only one of those ways, and is described for exemplary purposes only.

The main control unit 14 in Fig. 1 comprises two subblocks, 15 and 16. Sub-block 15 comprises functional blocks which detect the power control signal and control the amount of power delivered to load 1 in direct relation to the position of the potentiometer component RV10 within the load power adjustment signalling device Likewise, sub-block 16 may comprise similar functional blocks to ultimately control the amount of power delivered to load 2 in direct relation to the position of the potentiometer component RV11 within the load control and power adjustment signalling device 11 which functions independently of sub-block A variety of circuit embodiments may be used to achieve these requirements.

If the switches S10 or S11 in either of the load power adjustment signalling devices is open, no power is supplied to the corresponding load. When a switch is closed, the power delivered to the corresponding load can be manually adjusted and set by the signal voltage provided by the corresponding potentiometer components RV10 or RV11.

Potentiometers commonly comprise an operator adjustable knob providing rotational adjustment of the impedance of the component. In this example, however, it will be understood by those skilled in the art that there exist a variety of X. circuit means and passive component elements which could be used to provide a signal carried by a single polarity current and which changes its characteristics. For example a capacitive element could be varied to vary the voltage and phase characteristics of the single polarity current and the resultant signal communicated via the cable 13 to its corresponding load control sub unit.

Therefore, as shown in Fig 2 an averaging circuit block 23 generates a DC voltage output, the value of which varies 4 with the position of potentiometer VR21 in the corresponding load power adjustment signalling device 21.

Sub-block 23 of Fig. 2 is but one embodiment of an averaging circuit. For clarity, the devices 21, 22 are shown at the left of the figure, while the averaging circuit for load 1 is shown enclosed by dashed line 23. The time constant provided by components, resistor R3 and Cl, a reactive element, is by choice long compared with the period of the mains supply cycle, while R2 is selected'to be much greater than R3. Therefore the voltage across C1 (V1; positive with respect to neutral) varies only slightly over complete mains cycles, but at the same time depends on the setting of VR21, the potentiometer in the load 1 load power adjustment signalling device 21.

As described above, the voltage across C2 (V2; negative with respect to neutral) depends on the setting of VR22, the potentiometer in the load 2 load power adjustment signalling device 22.

Orientation of the diodes in the manner shown ensures that the voltage V1 is completely independent of the operation o the switch and potentiometer within the load 2 load power adjustment signalling device 22, and that the voltage V2 is completely independent of the switch and potentiometer within the load 1 load power adjustment signalling device 21.

Referring back to Fig 1, in an embodiment the functional circuit blocks labelled "variable power load control" accepts as an input the voltage output from the corresponding averaging circuit and therewith controls the power delivered to the corresponding load in proportion to the level of the voltage output.

Such power control circuitry is well known in the art, and any of several well known methods for controlling the power delivered to a mains powered electrical load can be utilised. Common methods which can be expected to find, use in practical implementation of this device include: 1) Phase control, where each half cycle of the AC voltage waveform supplied to the load is chopped by an adjustable amount. This method of power control may be 5 used when the load is an incandescent globe to adjust the brightness of the globe for minimum component count and cost.

2) Variable voltage control, where the magnitude of the continuous voltage applied to the load is varied. This can be achieved by use of a transformer with adjustable taps, or by dropping some,part of the mains voltage across ballast resistors, inductors or capacitors connected in series with the load. This method of controlling the power in the load may well be utilised when the unit is designed to control the speed of ceiling sweep fans and is depicted in Fig 5 for exemplary purposes.

3) Switching of complete mains cycles to the load. The 5. power delivered to the load is varied by successively turning the load ON or OFF for integral numbers of complete mains cycles. Two thirds power, for example, would comprise a repeating pattern of two complete mains cycles with the load turned ON followed by one complete mains cycle with the load turned OFF.

4) Pulse width modulation. This method includes having the load rapidly turned ON and OFF many times during each half cycle. The power dissipated in the load is controlled by changing the ratio of the pulse ON time to the pulse OFF time.

S With reference again to Fig 1, a different method for controlling the load power could be used in each of the subblocks 15 and 16. For example, load 1 could be an incandescent globe, the brightness of which is controlled by a phase control type circuit in sub-block 15, while load 2 could be a ceiling sweep fan, the speed of which is controlled by a variable voltage control circuit in sub-block 16.

Fig 3 shows the manner in which one half of a novel switch means can be used in place of sub-block 15 of Fig 1.

This arrangement would be used where the power level in only one load, needs to be controlled, while the other load only needs be switched ON or OFF.

6- Sub-block 16 of Fig 3 performs the power control function of the invention independently of sub-block 15 under the control of a variable resistor set by the operator at 11.

Although the present invention can be generally used when adding any new electrical loads to an existing installation, or for reducing the amount of wiring in new installations, in the embodiment of Fig I, one of the loads may be a ceiling sweep fan motor, and the other load an incandescent globe which is fitted to the fan. In this way, the energisation of both loads and the speed of the fan and the brightness of the globe can be independently controlled.

Thus, the main control unit 14 could be built into ceiling sweep fans of the type having a light fitting mounted Sintegral and below them. Such a fan would then be very easily installed in a room which already has a standard light fitting in the ceiling. The electrical installer would simply remove the existing light and mount the fan/light combination with appropriate sub-blocks built in in its place. The existing wall switch would be removed and replaced with the load 1 and load 2 load power adjustment signalling devices (10 and 11 of Fig The fan speed and light brightness level can then be conveniently controlled from the position of the old light switch, and no additional cables have had to be run as is required at the present time 23 to achieve the same result.

S. If control over the brightness of the light is not required, the circuitry controlling the light could be replaced with one half of the novel switch means (as described previously) and the potentiometer bridged out of circuit or omitted from the corresponding load power adjustment signalling device (10 or 11 of Fig This would allow the light to be simply switched on or off.

A further embodiment of the power control means of the invention which addresses the need to control load power, but eliminates the need for a reactive element at the slave circuit end of the arrangement is shown in Figs 4, 5 and 6.

Fig 4 shows a yet further embodiment of an electrical power control signal circuit means. An optional sedond load control circuit may independently control a second load, load 7 2, and may be either another power control circuit or the novel switch means as previously described and shown in Fig.

3.

With reference to the load 1 control circuit the resistor divider network RI, R2, and the diode D1 located in the ceiling mounted portion of the device, and the load power adjustment signalling device at the master switch end of an electrical power control signal circuit means provide a half wave rectified voltage signa- (positive with respect to neutral) VI shown as an input to a multi-channel analog to digital converter circuit 43.

The resistor values of R! and R2 are chosen so that the peak value of the voltage VI varies from a minimum of approximately 1V to a maximum of approximately 5V, as the potentiometer VR42 in the load power adjustment signalling device 42 is manually turned through its full resistive range. V1 is provided to one input of.a multi-channel analogue to digital converter 43, which, under the control of a specifically programmed microprocessor 44, Ls able to convert a large number of readings of voltage VI into digital representations and allow the microprocessor to determine the peak value of VI for each relevant half cycle of the alternating current conducted via the signal cable 13. These preceding elements form one embodiment of a signal detection C2S* means.

The peak value of V1 determines a load voltage which should be applied across load 1 to achieve a power dissipation which corresponds to the particular setting of the load power adjustment signalling device variable element which in this embodiment is a variable resistor VR42. The value of VI may also be used to signal the ON function of a switch provided the signal value is above a predetermined minimum value.

A further circuit is used as a reference for the microprocessor which comprises diode D2 and resistors R3 and R4 which generate a second positive current half wave rectified voltage signal, the peak value of which is directly proportional to the actual voltage across load 1. The values of R3 and R4 are selected so that the peak value of the half 8 wave rectified voltage V2 is approximately 5V when the full mains voltage is applied to load 1.

Voltage V2 is fed to a second input of the multi-channel analogue to digital converter 43 and is sampled in the same manner as VI, hence the microprocessor 44 is able to determine the peak value of V2 which represents the actual voltage V across load 1.

The microprocessor continually compares the voltage which should be across the load (determined from the peak value of VI) with the voltage which is actually across the load (determined from the peak value of V2) and adjusts the load power control circuit to bring the two voltages as close together as possible. In this way, the power dissipated in load 1 can be more accurately controlled by the control and power adjustment signalling device 42.

The Load Power Control Circuit 45 depicted in Fig 4 could be any of the well known methods listed previously, provided an acceptably smooth and continuous voltage waveform is generated across the load. Power control methods such as phase control or switching of complete mains cycles to the load which do not always provide smooth and continuous voltage waveforms across the load may also be used, however, the circuits to generate V2, or the required sampling rate and algorithm to determine the power across load 1 from V2 would necessarily be more complex.

Fig 5 shows one implementation of a Load Power Control circuit which is particularly useful for controlling ceiling sweep fans as is also discussed more generally previously.

Capacitors Cl to C4 can be switched into the power circuit to a load an inductive load) by switches Sl to S4. Switch 0 S5 allows mains voltage to be connected directly to the load for maximum power dissipation. Sl to S5 are independently controlled by the microprocessor 44, so that any combination of open and closed switches can be selected which allows a range of different capacitance values to be placed in series with the load. As the value of capacitance in series with the load decreases, the voltage drop across the capacitor switch network increases and the voltage across the load 9 decreases thereby reducing the power dissipated at the load.

Fig 5 depicts a circuit using four suitably chosen values for capacitors C1-C4, which provide in combination different power settings, not including zero power (when all switches are open) or maximum power (when switch S5 is closed). For example for C1 0.25uF, C2 0.5uF. C3 luF, C4 2uF, provides any capacitance from 0.25uF to 3.75uF in steps of 0.25uF which can then be inserted in series with the load, by opening and closing switches S1 to S4 in a binary sequence controlled by the microprocessor 44. Other values of capacitance could be used to match any particular load being controlled, or additional switches and capacitors could be added or removed to vary the possible range or increment of adjustment.

Resistors R1 to R4 are placed across each capacitor to allow the capacitors to discharge when the switches are opened. A small delay with all switches open when changing from one switch setting to another allows the capacitors to discharge and so avoid heavy discharge currents when switches are closed. This delay may be easily controlled by the microprocessor 44.

Fig 6 shows one possible implementation of the switches Sl to S6 in Fig. 5. In this embodiment the main triac, T1, is gated into couduction by an optically coupled trigger triac, T2. The light emitting diode inside the opticalll coupled triac is switched directly by data output lines from the microprocessor, thereby allowing individual control of each switch under programmed control.

3 There are significant cost advantages in using the invention in combination with a variety of power control techniques while preserving the concept of using existing wiring in a two wire AC circuit to a load remote from its controlling master switch/es. New wires or extra wires at initial installation are not required, while the components required to implement the invention are simple and reliable, thereby ensuring an economic solution to a commonly experienced problem of load switching combined with power control.

10

Claims (7)

1. 2. Electrical power control signal circuit means according to claim 1 wherein said signal circuit means further comprises a first diode located in series with said passive circuit component so arranged as to pass only a single polarity current and said detection means further comprising a second diode located in series with said passive circuit component so arranged as to pass the same single polarity current as said first diode. :e eoooo
2. 3. Electrical power control signal circuit means according to claim 1 wherein said power control means comprises analogue to digital conversion means to convert said i output signal into a digital representation of the value of the signal, microprocessor means to receive said digital representation and convert it into a power control signal, ~and a power control circuit to receive said power control signal and thereby control the application of and the amount of power applied to said electrical load from said TFW4 11 alternating current power source in proportion to the value of said output signal.
3. 4. Electrical power control signal circuit means according to ciaim 3 wherein said power control circuit comprises a plurality of parallel reactive elements consisting of a resistor and capacitor themselves in parallel, connected in series with said alternating current power source arranged to coDniuct a portion thereof, a plurality of power switching elements in series with each of said reactive elements and connected between said alternating current power source and said electrical load, a further power switch element connected directly between said alternating current power source and said electrical load, wherein, either said further power switch element by itself is controlled into a conducting state br said power control signal, or one or more of said plurality of power switch elements is controlled into a conducting state by said power control signal thereby supplying a portion of said alternating current power source to the said electrical load via respective one or more of said parallel reactive elements. :.i2 5. Electrical power control signal circuit means according to claim 4 wherein said power switch element comprises a triac device connected between said parallel reactive elements and said electrical load, and said power switch element further comprises an optically coupled tr-ac arranged to gate said triac device whereby said optically coupled triac is triggered by the application of said power control signal.
4. 6. Electrical power control signal circuit means according to claim 1 wherein said variable passive circuit component comprises a variable resistive element which modifies the magnitude of the single polarity current signal, and said detection means comprises a voltage averaging circuit means 12 7 C) having a voltage signal output indicative of the amount of power to be applied to a respective electrical load.
5. 7. Electrical power control signal circl;t means according to claim 1 wherein said variable passive ircuit component comprises a variable resistive element which modifies the magnitude of the single polarity current signal, and said detection means comprises a voltage divider circuit means having a voltage signal output indicative of the amount of power to be applied to a respective electrical load.
6. 8. Electrical power control signal circuit means substantially as hereinbefore described with reference to the accompanying Figs. 1 and 2.
7. 9. Electrical power control signal circuit means substantially as hereinbefore described with reference to the accompanying Figs. 3 and 4. Electrical power control signal circuit means substantially as hereinbefore described with reference to the accompanying Figs. 1, 3, 4, 5 and 6. Dated this 19th day of August 1993 GERARD INDUSTRIES PTY LTD By its Patent Attorneys, R K MADDERN ASSOCIATES *e *e 13