BRIEF DESCRIPTION OF THE DRAWINGS
For the purpose of illustrating the invention, there is shown in the drawings a form, which is presently preferred, it being understood, however, that the invention is not limited to the precise arrangements and instrumentalities shown. The features and advantages of the present invention will become apparent from the following description of the invention that refers to the accompanying drawings, in which:
FIG. 1A shows a prior art three-way switch system, which includes two three-way switches;
FIG. 1B shows an example of a prior art three-way dimmer switch system including one prior art three-way dimmer switch and one three-way switch;
FIG. 1C shows a prior art four-way switching system;
FIG. 1D shows a prior art extended four-way switching system;
FIG. 2 is a simplified block diagram of a typical prior art multiple location lighting control system;
FIG. 3 shows the prior art user interface of the dimmer switch of the multiple location lighting control system of FIG. 2;
FIG. 4A shows a prior art three-way system having a smart three-way dimmer;
FIG. 4B shows another prior art three-way system having a smart three-way dimmer;
FIG. 5 is a simplified block diagram of a three-way dimming system including two smart three-way dimmers according to the present invention;
FIG. 6 is a simplified schematic diagram of a zero-crossing detector of the dimmers of FIG. 5;
FIG. 7 is a flowchart of a zero-crossing procedure, which is executed by controllers of the dimmers of FIG. 5;
FIG. 8 is a flowchart of the intensity level procedure, which is executed by the controllers of the dimmers of FIG. 5;
FIG. 9 is a flowchart of a triac firing procedure, which is executed by the controllers of the dimmers of FIG. 5;
FIG. 10 is a flowchart of an input monitor procedure, which is executed by the controllers of the dimmers of FIG. 5;
FIG. 11 is a simplified block diagram of a multiple location dimming system having four smart dimmers, each having four load terminals;
FIG. 12 is a simplified block diagram of a multiple location dimming system having four smart dimmers, each having two load terminals;
FIG. 13 is a simplified block diagram of a three-way dimming system including two smart three-way dimmers according to another embodiment of the present invention;
FIG. 14 is a simplified schematic diagram of a current sense circuit of the smart three-way dimmers of FIG. 13; and
FIG. 15 is a simplified block diagram of a multiple location dimming system having three smart dimmers, each having four load terminals and two current sense circuits.
DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION
The foregoing summary, as well as the following detailed description of the preferred embodiments, is better understood when read in conjunction with the appended drawings. For the purposes of illustrating the invention, there is shown in the drawings an embodiment that is presently preferred, in which like numerals represent similar parts throughout the several views of the drawings, it being understood, however, that the invention is not limited to the specific methods and instrumentalities disclosed.
FIG. 5 is a simplified block diagram of a three-way dimming system 500 including two smart three-way dimmers 502A, 502B according to the present invention. The dimmers 502A, 502B are connected in series between an AC voltage source 506 and a lighting load 508. Note that the dimmers 502A, 502B are identical in structure, such that either of the dimmers 502A, 502B could be coupled on the line-side or the load-side of the three-way system 500. The dimmers 502A, 502B include hot terminals H1, H2 that are coupled to the AC voltage source 506 and the lighting load 508, respectively. A switched hot terminal SH1 of the first dimmer 502A is coupled to a dimmed hot terminal DH2 of the second dimmer 502B. Similarly, a switched hot terminal SH2 of the second dimmer 502B is coupled to a dimmed hot terminal DH1 of the first dimmer 502A. The terminals H1, H2, SH1, SH2, DH1, DH2 of the dimmers 502A, 502B may be screw terminals, insulated wires or “flying leads”, stab-in terminals, or other suitable means of connecting the dimmer to the AC voltage source 506 and the lighting load 508.
Since the dimmers 502A, 502B are identical in structure, only dimmer 502A will be described in greater detail below. The components of dimmer 502B have similar functions and similar reference numbers to the corresponding components of dimmer 502A. The dimmer 502A comprises a bidirectional semiconductor switch 510A, which is coupled between the switched hot terminal SH1 and the dimmed hot terminal DH1. As shown in FIG. 5, the dimmer 502A implements the semiconductor switch as a triac. However, other semiconductor switching circuits may be used, such as, for example, two FETs in anti-series connection, a FET in a bridge, or one or more insulated-gate bipolar junction transistors (IGBTs). The triac 510A has a gate (or control input) that is coupled to a gate drive circuit 512A. The dimmer 502A further includes a controller 514A that is coupled to the gate drive circuit 512A to control an on-time tON of the triac 510A, i.e., the period of time that the triac 510A conducts the load current, each half-cycle. The controller 514A is preferably implemented as a microcontroller, but may be any suitable processing device, such as a programmable logic device (PLD), a microprocessor, or an application specific integrated circuit (ASIC).
A power supply 516A generates a DC voltage, VCC, to power the controller 514A. The power supply 516A is coupled across the triac 510A, i.e., from the switched hot terminal SH1 to the dimmed hot terminal DH1. The power supply 516A is able to charge by drawing a charging current through the lighting load 508 when the triac 510A is not conducting and there is a voltage potential developed across the dimmer 502A.
The dimmer 502A further includes a sensing circuit for sensing an electrical characteristic of the dimmer. The electrical characteristic may be a voltage developed across the dimmer 502A or a load current conducted through the dimmer. Specifically, the dimmer 502A comprises a zero-crossing detector 518A, i.e., a voltage monitoring circuit, which is coupled across the triac 510A. The zero-crossing detector 518A monitors the voltage across a “dimmer voltage” across the controllably conductive device 510A to determine the zero-crossings of the input AC waveform from the AC power supply 206. A zero-crossing is defined as the time at which the AC supply voltage transitions from positive to negative polarity, or from negative to positive polarity, at the beginning of each half-cycle. The zero-crossing information is provided as an input to controller 514A. The controller 514A provides the gate control signals to operate the semiconductor switch 510A to provide voltage from the AC power supply 506 to the lighting load 508 at predetermined times relative to the zero-crossing points of the AC waveform.
The controller 514A uses forward phase control dimming (or leading edge control dimming) to control the on-time tON of the triac 510A and thus the intensity of the lighting load 508. With forward phase control dimming, the triac 510A is rendered conductive, i.e., turned on or “fired”, at some time, i.e., a phase angle, within each AC line voltage half-cycle. The triac 510A remains on until the next line voltage zero-crossing at which time the triac is rendered non-conductive. Forward phase control dimming is often used to control energy to a resistive or inductive load, which may include, for example, a magnetic low-voltage transformer or an incandescent lamp.
FIG. 6 is a simplified schematic diagram of the zero-crossing detector 518A. The AC terminals of a full wave rectifier bridge 630 are coupled between the hot terminal Hi and the dimmer hot terminal DH1, i.e., across the triac 510A. The rectifier bridge 630 comprises four diodes 632, 634, 636, 638. The DC terminals of the rectifier bridge 630 are coupled across a photodiode 642 of an optocoupler 640 and a resistor 650. A phototransistor 644 of the optocoupler 640 is responsive to the photodiode 642. The control signal of the zero-crossing detector 518A, i.e., the output to the controller 514A, is provided at the junction of a resistor 652 and the phototransistor 644. The output of the controller 514A is coupled to the DC voltage VCC of the power supply 516A through the resistor 652. When there is substantially no voltage developed across the triac 510A, i.e., when the photodiode 642 is not forward biased, the output to the controller 514A is pulled up to a logic high level. When a voltage is developed across the triac 510A, an input current will flow through the photodiode 642 and the resistor 650. Accordingly, the phototransistor 644 will pull the output down to a circuit common 654, i.e., a logic low level. Thus, the control signal is the logic low level for most of the half-cycle and the logic high level at the zero-crossing. The resistor 650 preferably has a substantially large resistance, e.g., 56 kΩ, such that the magnitude of the input current through the photodiode 642 is small.
A user interface 520A is coupled to the controller 514A and to allow a user to determine a desired lighting level (or state) of the lighting load 508. The user interface 520A provides a plurality of actuators for receiving inputs from a user, e.g., including a toggle button and an intensity actuator. In response to an actuation of the toggle button, the controller 514A will toggle the state of the lighting load 508 (i.e., from on to off and vice versa) as will be described in greater detail below. Further, the controller 514A will adjust the intensity of the lighting load 508 in response to an actuation of the intensity actuator. The user interface 520A further provides a plurality of status indicators, e.g., LEDs, to provide feedback to a user of the dimmer 502A. The status indicators are preferably arranged to display an operating characteristic of the dimmer 502A or the lighting load 508. For example, the status indicators may be arranged in a linear array (as shown in FIG. 3) to display the intensity of the lighting load 508.
The dimmers 502A, 502B include airgap switches 522A, 522B coupled to the hot terminals H1, H2 (which are preferably coupled to the AC power source 406 and the lighting load 408, respectively). Accordingly, the airgap switches 522A, 522B are each coupled between the AC power source 406 and the lighting load 408 such that if either airgap switch 522A, 522B is opened, current is prevented from flowing through the lighting load 508. The dimmers 502A, 502B further comprise inductors 524A, 524B, i.e., chokes, for providing electromagnetic interference (EMI) filtering.
According to the present invention, the triacs 510A, 510B of the dimmers 502A, 502B are coupled in parallel electrical connection between the AC source 506 and the lighting load 508. Only one of the triacs 510A, 510B will conduct the load current from the AC source 506 to the lighting load 508 at any given time. The dimmer 502A, 502B having the conducting triac 510A, 510B is consider to be in an “active” mode. Accordingly, the dimmer 502A, 502B that has the triac 510A, 510B that is not conducting current to the lighting load 508 will be in a “passive” mode. When the dimmer 502A, 502B is in the active mode, the respective controller 514A, 514B is operable to control the on-time of the conducting triac 510A, 510B to control the intensity of the lighting load 508.
As used herein, when a first device and a second device are coupled in “parallel electrical connection”, a first path can be traced from the AC source 506 to the lighting load 508 through the first device, wherein the first path does not pass through the second device, and a second path can be traced from the AC source to the lighting load through the second device, wherein the second path does not pass through the first device. Accordingly, other electrical components may be coupled in series with the first and second devices such that the first and second devices are still fundamentally coupled in parallel. For example, the inductors 524A, 524B may be coupled in series with the triacs 510A, 510B, respectively, such that the series combinations of the inductors and the triacs are coupled in parallel. Further, as used herein, first dimmer and second dimmer that are coupled in “parallel electrical connection” are coupled such that their controllably conductive devices are coupled in parallel electrical connection.
When the first dimmer 502A is in the passive mode, the first controller 514A monitors the firing angle of the second triac 510B, i.e., the present intensity of the lighting load 508, by monitoring the output of the first zero-crossing detector 518A. Accordingly, the first controller 514A is operable to display the present lighting intensity of the lighting load 508 on the status indicators of the user interface 520A independent of whether the controller is presently controlling the lighting load.
According to the present invention, the dimmers 502A, 502B are operable to communicate with each other to “take control” of the lighting load 508. When the dimmer 502A, 502B is in the passive mode, the controller 502A, 502B is operable to change from the passive mode to the active mode to take control of the lighting load 508, for example, in response to an actuation of a button of the user interface 520A, 522B. To take control of the lighting load 508, the controller 502A, 502B of the dimmer 502A, 502B that is in the passive mode is operable to fire the respective triac 510A, 510B just before the triac of the dimmer that is in the active mode.
For example, if the first dimmer 502A is in the active mode and the second dimmer 502B is in the passive mode, the first controller 514A is operable to control the intensity of the lighting load 508 by turning on the triac 510A at a time approximately 5 msec after a zero-crossing of the AC line voltage. Accordingly, the triac 510A will conduct the load current for a first on-time tON1 of approximately 3 msec each half-cycle. To take control of the lighting load, the second controller 514B is operable to turn on the second triac 510B at a time before the first controller 514A turns on the first triac 510A, for example, at a time approximately 4.9 msec after a zero-crossing of the AC line voltage (i.e., such that a second on-time tON2 of the second triac 510B is 3.1 msec). The first controller 514A then determines that the second controller 514B has fired the second triac 510B by monitoring the output of the first zero-crossing detector 518A. Specifically, the dimmer voltage across the first triac 510A will be substantially zero volts if the second controller 514B has fired the second triac 510B. If the first controller 514A determines that the second triac 510B has fired, the first controller does not fire the first triac 510A during the present half-cycle. Preferably, the second controller 514B of the second dimmer 502B continues to control the conduction time of the second triac 510B with the second on-time tON2 for a predetermined amount of time, i.e., a predetermined number of half-cycles, e.g., three (3) half-cycles. After the predetermined amount of time, the second controller 514B will control the second triac 510B to a desired intensity level as determined from the input provided by the second user interface 522B.
FIGS. 7-10 show flowcharts of the software of the controller 514A, 514B for operating the dimmers 502A, 502B in the three-way dimming system 500 according to the present invention. The flowcharts will be described with reference to the first controller 514A, even though the second controller 514B preferably executes exactly the same software.
FIG. 7 is a flowchart of a zero-crossing procedure 700, which is preferably executed every half-cycle beginning at a zero-crossing of AC voltage source 506 at step 710. If the dimmer 502A is in the active mode at step 712, a firing angle timer begins decreasing at step 714 with an initial value that corresponds to a desired intensity level. The desired intensity level is generated in response to a user input, for example, from the user interface 520A and is stored in a memory of the controller 514A. When the firing angle timer expires, a fire triac interrupt request (IRQ) occurs. A triac firing procedure 900 is executed in response to the fire triac IRQ and will be described in greater detail below, with reference to FIG. 9.
When the dimmer 502A is in the passive mode, the first controller 514A determines the firing angle of the second triac 510B of the second dimmer 502B (which is in the active mode). Specifically, if the dimmer 502A is not in the active mode, i.e., in the passive mode, at step 712, a determination is made as to whether the dimmer 502A is transitioning from the passive mode to the active mode at step 716. If not, an intensity level timer is started at step 718. The intensity level timer increases in value with time and is used by an intensity level procedure 800 to calculate the firing angle of the second triac 510B of the second dimmer 502B.
FIG. 8 is a flowchart of the intensity level procedure 800, which is executed every half-cycle when the controller 514A is in the passive mode in response to an intensity level IRQ. The intensity level IRQ occurs at step 810 when the controller 514A has been signaled by the zero-crossing detector 518A that the voltage across the first triac 501A has fallen to substantially zero volts. At step 812, the controller 514A saves the value of the intensity level timer in a memory of the controller. At step 814, the controller 514A uses the value of the intensity level timer, i.e., the firing angle of the second triac 510B, to determine the amount of power being delivered to the lighting load 508, i.e., the lighting intensity of the lighting load. The controller 514A then uses the determined lighting intensity of the lighting load 508 to illuminate one or more of the status indicators of the user interface 520A to provide the intensity of the lighting 508 as feedback to a user at step 816 and exits at step 818.
While the dimmer 502A is transitioning from the passive mode to the active mode, the controller 514A will fire the first triac 510A before the second triac 510B of the second dimmer 502B for a predetermined number of half-cycles. The controller 514A uses an advance counter to keep track of how many half-cycles the dimmer 502A has fired the first triac 510A before the second triac 510B. Referring back to FIG. 7, if the dimmer 502A is transitioning from the passive mode to the active mode at step 716 and if the advance counter is greater than zero at step 720, the controller 514A decrements the advance counter by one (1) at step 722. At step 724, the controller 514A subtracts an advance constant, e.g., 100 μsec, from the calculated intensity level of the lighting load 508 (as determined in the light level procedure 800 shown in FIG. 8) to produce an advanced firing time. Next, the controller 514A starts the firing angle timer at step 726 using the advanced firing time from step 724 and the procedure 700 exits at step 730. If the advance counter has decreased to zero at step 720, the controller 514A enters the active mode at step 728 and exits the zero-crossing procedure 700 at step 730.
FIG. 9 is a flowchart of a triac firing procedure 900, which the controller 514A preferably executes once every half-cycle in response to the fire triac interrupt request (IRQ) at step 910 when firing angle timer expires. The firing angle timer is started at steps 714 and 726 of FIG. 7. If the dimmer 502A is not transitioning to the active mode at step 912, the controller 514A monitors the output of the zero-crossing detector at step 914 to determine if the dimmer voltage across the first triac 510A is substantially zero volts, i.e., if the second triac 510B is conductive. If the second triac 510B is not conductive at step 916, the controller 514A simply fires the first triac 510A as normal at step 918 and then exits at step 924. If the second triac 510B is conductive at step 916, the controller 514A does not fire the triac 510A during the present half-cycle. The controller 514A changes to the passive mode at step 920 and exits at step 924. If the dimmer 502A is transitioning to the active mode at step 912, the controller 514A fires the triac 510A at the advanced time to take control of the lighting load 508 at step 922 and exits at step 924.
FIG. 10 is a flowchart of an input monitor procedure 1000, which is preferably executed once every half cycle and begins at step 1010. At step 1012, the controller 514A checks the inputs, for example, inputs provided from the user interface 520A. If no inputs are received at step 1014, the procedure 1000 simply exits at step 1022. Otherwise, if the dimmer 502A is in the passive mode at step 1015, the controller 514A begins to transition to the active mode at step 1016. At step 1018, the controller 514A initializes the advance counter to a maximum advance counter value, e.g., three, such that the controller fires the first triac 510A before the second triac 510B for three half-cycles while transitioning to the active mode. Next, the controller 514 processes the input accordingly at step 1020 and exits at step 1022.
While the present invention has been described with reference to the three-way dimming system 500 shown in FIG. 5, the present invention is not limited to including only two dimmers 502A, 502B. FIG. 11 is a simplified block diagram of a multiple location dimming system 1100 having four smart dimmers 1102A, 1102B, 1102C, 1102D according to the present invention. Each dimmer 1102A, 1102B, 1102C, 1102D has a controllably conductive device, e.g., a triac 1110A, 1110B, 1110C, 1110D. The triacs 1110A, 1110B, 1110C, 1110D are coupled in parallel electrical connection between an AC power source 1106 and a lighting load 1108, such that each triac is able to control the intensity of the lighting load. As shown in FIG. 11, each dimmer 1102A, 1102B, 1102C, 1102D has four terminals to allow for simple connection between the dimmers. Each of the dimmers 1102A, 1102B, 1102C, 1102D includes a power supply (not shown), which is operable to charge by drawing a charging current through the lighting load 1108. Preferably, the charging current of each power supply is substantially small, such that the sum of the charging currents of each of the power supplies is not large enough the illuminate the lighting load 1108.
Only one of the dimmers 1102A, 1102B, 1102C, 1102D may be in the active mode, i.e., controlling the lighting load 1108, at a given time, while the other three dimmers are in the passive mode. As with the system 500 shown in FIG. 5, one of the dimmers 1102A, 1102B, 1102C, 1102D in the passive mode may temporarily increase the firing angle provided to the lighting load 1108 to take control of the lighting load. The present invention is not limited to including only four dimmers as shown in FIG. 11. Since the triacs of the dimmers are provided in parallel electrical connection, more dimmers can be added to the system 1100.
FIG. 12 is a simplified block diagram of a multiple location dimming system 1200 having a plurality of smart dimmers 1202A, 1202B, 1202C, 1202D, each having only two terminals. Each dimmer 1202A, 1202B, 1202C, 1202D has a controllably conductive device, e.g., a triac 1210A, 1210B, 1210C, 1210D. The triacs 1210A, 1210B, 1210C, 1210D are coupled inparallel electrical connection between an AC power source 1206 and a lighting load 1208, such that each triac is able to control the intensity of the lighting load. The dimmers 1202A, 1202B, 1202C, 1202D operate in a similar fashion to the dimmers of the other systems 500, 1100 described.
FIG. 13 is a simplified block diagram of a three-way dimming system 1300 according to another embodiment of the present invention. The system 1300 comprises two dimmers 1302A, 1302B coupled between an AC power source 1306 and a lighting load 1308 for individual control of the amount of power delivered to the lighting load. The dimmers 1302A, 1302B include current sense circuits 1326A, 1326B, which are coupled in series with the switched hot terminals SH1, SH2, respectively, and both provide a control signal to a controller 1314A. When the dimmers 1302A, 1302B are in the passive mode, the current sense circuit 1326A, 1326B provide control signals representative of the firing angle of the triac 510A, 510B in the other triac. For example, when first dimmer 1302A is in the passive mode, the first current sense circuit 1326A is operable to sense the rising edge of the load current through the switched hot terminal SI when the second triac 510B fires. Even though the flowcharts of the software executed by the controller 1314A are not shown in the present application, the controller logic for this embodiment is substantially similar to the flowcharts shown in FIGS. 7-10.
FIG. 14 is a simplified schematic diagram of the current sense circuit 1326A. The current sense circuit 1326A includes a current sense transformer 1430 that has a primary winding coupled in series between the switched hot terminal SH1 and the junction of the triac 510A and the inductor 524A. The current sense transformer 1430 only operates above a minimum operating frequency, such that current only flows in the secondary winding when the current waveform through the primary winding has a frequency above the minimum operating frequency. Preferably, the current sense transformer 1430 detects the rising edge of the load current through the second triac 510B of the second dimmer 502B. Since the load current will increase very quickly when the second triac 510B fires (i.e., the load current has a high-frequency component), a current will flow in the secondary winding of the current sense transformer when the second triac 510B fires.
The secondary winding of the current sense transformer 1430 is coupled across a resistor 1432. The resistor 1432 is further coupled between circuit common and the negative input of a comparator 1434. A reference voltage is produced by a voltage divider comprising two resistors 1436, 1438 and is provided to the positive input of the comparator 1434. The output of the comparator 1434 is tied to the DC voltage VCC of the power supply 516A through a resistor 1440 and is coupled to the controller 1314A. When current flows through the secondary winding of the current sense transformer 1430, a voltage is produced across the resistor 1432 that exceeds the reference voltage. The comparator 1434 then drives the output low, signaling to the controller 1314A that current has been sensed. Alternatively, the current detect circuit 1326A may be implemented using an operational amplifier or a discrete circuit comprising one or more transistors rather than the comparator 1434.
FIG. 15 is a simplified block diagram of another multiple location dimming system 1500. The system 1500 comprises a plurality of dimmers 1502A, 1502B, 1502C coupled between an AC source 1506 and a lighting load 1508. Each of the dimmers 1502A, 1502B, 1502C comprises a triac 1510A, 1510B, 1510C operable to control the amount of power delivered to the lighting load 1508. Since the dimmers 1502A, 1502B, 1502C each comprise four load terminals, each of the dimmers comprises a first current sense circuit 1526A, 1526B, 1526C and a second current sense circuit 1528A, 1528B, 1528C, respectively. Each of the first and second current sense circuits is responsive to the rising edge of the load current flowing through the respective current sense circuit. For example, the dimmer 1502B is operable to sense the firing angle of the load current through the triac 1510A through the second current sense circuit 1528B or the load current through the triac 1510C through the first current sense circuit 1526B.
Although the words “device” and “unit” have been used to describe the elements of the dimming systems of the present invention, it should be noted that each “device” and “unit” described herein need not be fully contained in a single enclosure or structure. For example, the dimmer 502A of FIG. 5 may comprise a plurality of buttons in a wall-mounted enclosure and a controller that is included in a separate location. Also, one “device” may be contained in another “device”. For example, the semiconductor switch (i.e., the controllably conductive device) is a part of the dimmer of the present invention.
Although the present invention has been described in relation to particular embodiments thereof, many other variations and modifications and other uses will become apparent to those skilled in the art. Therefore, the present invention should not be limited by the specific disclosure herein.
Patent Application
20070296347
