Two-wire dimmer switch for low-power loads
First Claim
1. A load control device for controlling the amount of power delivered from an AC power source to an electrical load to a desired amount of power, the load control device comprising:
- a bidirectional semiconductor switch adapted to be coupled in series electrical connection between the AC power source and the electrical load for conducting a load current from the AC power source to the electrical load, the bidirectional semiconductor switch having a control input for rendering the bidirectional semiconductor switch conductive and non-conductive; and
a control circuit receiving a signal representative of a voltage developed across the bidirectional semiconductor switch, the control circuit operable to determine a half-cycle start time near the beginning of a half-cycle of the AC power source in response to the signal representative of the voltage developed across the bidirectional semiconductor switch;
wherein the control circuit;
conducts a control current through the load so as to generate a gate drive signal that is operatively coupled to the control input of the bidirectional semiconductor switch;
drives the gate drive signal to a first magnitude to render the bidirectional semiconductor switch conductive after a first variable amount of time has elapsed since the half-cycle start time;
maintains the gate drive signal at the first magnitude after the bidirectional semiconductor switch is rendered conductive, such that the bidirectional semiconductor switch remains conductive independent of the magnitude of the load current conducted through the bidirectional semiconductor switch;
drives the gate drive signal to a second magnitude to render the bidirectional semiconductor switch non-conductive after a second fixed amount of time has elapsed since the half-cycle start time;
controls the second fixed amount of time to be approximately equal during each half-cycle of the AC power source;
varies the first variable amount of time in response to the desired amount of power to be delivered to the load to thus control the amount of power delivered to the load to the desired amount.
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Accused Products
Abstract
A two-wire load control device (such as, a dimmer switch) is operable to control the amount of power delivered from an AC power source to an electrical load (such as, a high-efficiency lighting load) and has substantially no minimum load requirement. The dimmer switch includes a bidirectional semiconductor switch, which is operable to be rendered conductive each half-cycle and to remain conductive independent of the magnitude of a load current conducted through semiconductor switch. The dimmer switch comprises a control circuit that conducts a control current through the load in order to generate a gate drive signal for rendering the bidirectional semiconductor switch conductive and non-conductive each half-cycle. The control circuit may provide a constant gate drive to the bidirectional semiconductor switch after the bidirectional semiconductor switch is rendered conductive each half-cycle. The bidirectional semiconductor switch may comprise, for example, a triac or two field-effect transistors coupled in anti-series connection.
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Citations
77 Claims
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1. A load control device for controlling the amount of power delivered from an AC power source to an electrical load to a desired amount of power, the load control device comprising:
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a bidirectional semiconductor switch adapted to be coupled in series electrical connection between the AC power source and the electrical load for conducting a load current from the AC power source to the electrical load, the bidirectional semiconductor switch having a control input for rendering the bidirectional semiconductor switch conductive and non-conductive; and a control circuit receiving a signal representative of a voltage developed across the bidirectional semiconductor switch, the control circuit operable to determine a half-cycle start time near the beginning of a half-cycle of the AC power source in response to the signal representative of the voltage developed across the bidirectional semiconductor switch; wherein the control circuit; conducts a control current through the load so as to generate a gate drive signal that is operatively coupled to the control input of the bidirectional semiconductor switch; drives the gate drive signal to a first magnitude to render the bidirectional semiconductor switch conductive after a first variable amount of time has elapsed since the half-cycle start time; maintains the gate drive signal at the first magnitude after the bidirectional semiconductor switch is rendered conductive, such that the bidirectional semiconductor switch remains conductive independent of the magnitude of the load current conducted through the bidirectional semiconductor switch; drives the gate drive signal to a second magnitude to render the bidirectional semiconductor switch non-conductive after a second fixed amount of time has elapsed since the half-cycle start time; controls the second fixed amount of time to be approximately equal during each half-cycle of the AC power source; varies the first variable amount of time in response to the desired amount of power to be delivered to the load to thus control the amount of power delivered to the load to the desired amount. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15)
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16. A load control device for controlling the amount of power delivered from an AC power source to an electrical load to a desired amount of power, the load control device comprising:
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a bidirectional semiconductor switch adapted to be coupled in series electrical connection between the AC power source and the electrical load for conducting a load current from the AC power source to the electrical load, the bidirectional semiconductor switch having a control input for rendering the bidirectional semiconductor switch conductive and non-conductive; and a control circuit operable to conduct a control current through the load in order to render the bidirectional semiconductor switch conductive and non-conductive each half-cycle of the AC power source, the control circuit including a timing circuit for generating a timing signal that increases in magnitude with respect to time, the timing circuit starting to generate the timing signal at a start time shortly after a zero-crossing of the AC power source, the control circuit also including a drive circuit for receiving the timing signal and rendering the bidirectional semiconductor switch conductive each half-cycle in response to the magnitude of the timing signal, so as to control the amount of power delivered to the electrical load to the desired amount; wherein the timing circuit is operable to continue generating the timing signal after the bidirectional semiconductor switch is rendered conductive each half-cycle, such that the drive circuit continues to render the bidirectional semiconductor switch conductive and the bidirectional semiconductor switch remains conductive independent of the magnitude of the load current conducted through the bidirectional semiconductor switch. - View Dependent Claims (17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31)
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32. A load control device for controlling the amount of power delivered from an AC power source to an electrical load to a desired amount of power, the load control device comprising:
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a bidirectional semiconductor switch adapted to be coupled in series electrical connection between the AC power source and the electrical load for conducting a load current from the AC power source to the electrical load, the bidirectional semiconductor switch having a control input for rendering the bidirectional semiconductor switch conductive and non-conductive; and a timing circuit operable to conduct a timing current through the load so as to generate a timing signal, the timing circuit operable to begin generating the timing signal at a start time shortly after a zero-crossing of the AC power source, the timing signal increasing in magnitude with respect to time at a constant rate; and a drive circuit for receiving the timing signal and rendering the bidirectional semiconductor switch conductive when the magnitude of the timing signal exceeds a variable threshold representative of the desired amount of power to be delivered to the load; wherein the timing circuit is operable to continue generating the timing signal after the bidirectional semiconductor switch is rendered conductive each half-cycle, such that the drive circuit continues to render the bidirectional semiconductor switch conductive and the bidirectional semiconductor switch remains conductive independent of the magnitude of the load current conducted through the bidirectional semiconductor switch, the timing circuit operable to stop generating the timing signal after a fixed amount of time has elapsed since the start time in order to render the bidirectional semiconductor switch non-conductive. - View Dependent Claims (33, 34, 35, 36, 37, 38)
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39. A control circuit for a two-wire load control device for controlling the amount of power delivered from an AC power source to an electrical load, the load control device having a bidirectional semiconductor switch adapted to be coupled in series electrical connection between the AC power source and the electrical load and having a control input for rendering the bidirectional semiconductor switch conductive and non-conductive, the control circuit comprising:
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a timing circuit for generating a timing signal that increases in magnitude with respect to time, the timing circuit starting to generate the timing signal at a start time shortly after a zero-crossing of the AC power source, the timing circuit ceasing to generate the timing signal after a fixed amount of time has elapsed since the start time; and a drive circuit for receiving the timing signal and generating a gate drive signal that is operatively coupled to the control input of the bidirectional semiconductor switch, the drive circuit driving the gate drive signal to a first magnitude to render the bidirectional semiconductor switch conductive when the magnitude of the timing signal exceeds a trigger threshold, the drive circuit maintaining the gate drive signal at the first magnitude after the bidirectional semiconductor switch is rendered conductive, the drive circuit driving the gate drive signal to a second magnitude to render the bidirectional semiconductor switch non-conductive when the timing circuit ceases generating the timing signal, such that the gate drive signal is controlled to the first magnitude for a conduction time; wherein the control circuit conducts a control current through the load to enable the timing circuit to generate the timing signal and the drive circuit to generate the gate drive signal, and the conduction time of the gate drive signal has a length that is not dependent upon the length of the fixed amount of time that the timing circuit generates the timing signal. - View Dependent Claims (40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54)
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55. A timing circuit for generating a timing signal in a load control device to determine for controlling the amount of power delivered from an AC power source to an electrical load, the timing signal used to determine when a bidirectional semiconductor switch of the load control device is rendered conductive and non-conductive, the timing circuit comprising:
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a constant ramp circuit for generating the timing signal, such that the timing signal increases in magnitude with respect to time at a constant rate; a reset circuit coupled to the timing signal for starting to generate the timing signal at a start time shortly after a zero-crossing of the AC power source; and a one-shot circuit coupled to the timing signal for ceasing to generate the timing signal prior to the end of the present half-cycle after a fixed amount of time has elapsed since the start time; wherein a dead time exists between the time when the one-shot circuit ceases to generate the timing signal during the present half-cycle and the time when the reset circuit starts to generate the timing signal at the start time during the next, subsequent half-cycle. - View Dependent Claims (56, 57, 58, 59, 60)
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61. A lighting control system adapted to be coupled to an AC power source, the lighting control system comprising:
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a high-efficiency lighting load including a high-efficiency light source and a load regulation device electrically coupled to the high-efficiency light source for controlling the amount of power delivered to the high-efficiency light source, the load regulation device characterized by a capacitive impedance; and a two-wire dimmer switch adapted to be coupled between the AC power source and the high-efficiency lighting load, the dimmer switch comprising a bidirectional semiconductor switch adapted to be coupled in series electrical connection between the AC power source and the high-efficiency lighting load for conducting a load current from the AC power source to the high-efficiency lighting load, the dimmer switch further comprising a control circuit operable to conduct a control current through the high-efficiency lighting load in order to render the bidirectional semiconductor switch conductive each half-cycle of the AC power source; wherein the bidirectional semiconductor switch remains conductive independent of the magnitude of the load current conducted through the bidirectional semiconductor switch, and is operable to conduct the load current to and from the high-efficiency lighting load during a single half-cycle of the AC power source. - View Dependent Claims (62, 63, 64, 65, 66, 67)
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68. A lighting control system adapted to be coupled to an AC power source, the lighting control system comprising:
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a high-efficiency lighting load including a high-efficiency light source and a load regulation device electrically coupled to the high-efficiency light source for controlling the amount of power delivered to the high-efficiency light source, the load regulation device characterized by a capacitive impedance; and a two-wire dimmer switch adapted to be coupled between the AC power source and the high-efficiency lighting load, the dimmer switch having electrical connections consisting of a hot terminal adapted to be coupled to the AC power source and a dimmed-hot terminal adapted to be coupled to the high-efficiency lighting load, the dimmer switch comprising a bidirectional semiconductor switch adapted to be coupled in series electrical connection between the AC power source and the high-efficiency lighting load for conducting a load current from the AC power source to the high-efficiency lighting load; wherein the bidirectional semiconductor switch is operable to be rendered conductive each half-cycle of the AC power source and to remain conductive independent of the magnitude of the load current conducted through the bidirectional semiconductor switch, the bidirectional semiconductor switch further operable to conduct the load current to and from the high-efficiency light source during a single half-cycle of the AC power source.
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69. A method for controlling the amount of power delivered from an AC power source to an electrical load to a desired amount of power, the method comprising:
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conducting a load current from the AC power source to the electrical load; controllably rendering a bidirectional semiconductor switch conductive and non-conductive so as control the load current and the amount of power delivered to the load; receiving a signal representative of a voltage developed across the bidirectional semiconductor switch; determining a half-cycle start time near the beginning of a half-cycle of the AC power source in response to the signal representative of the voltage developed across the bidirectional semiconductor switch; conducting a control current through the load so as to generate a gate drive signal that is operatively coupled to a control input of the bidirectional semiconductor switch; driving the gate drive signal to a first magnitude to render the bidirectional semiconductor switch conductive after a first variable amount of time has elapsed since the half-cycle start time; maintaining the gate drive signal at the first magnitude after the bidirectional semiconductor switch is rendered conductive, such that the bidirectional semiconductor switch remains conductive independent of the magnitude of the load current conducted through the bidirectional semiconductor switch; driving the gate drive signal to a second magnitude to render the bidirectional semiconductor switch non-conductive after a second fixed amount of time has elapsed since the half-cycle start time; controlling the second fixed amount of time to be approximately equal during each half-cycle of the AC power source; and varying the first variable amount of time in response to the desired amount of power to be delivered to the load to thus control the amount of power delivered to the load to the desired amount. - View Dependent Claims (70, 71, 72, 73, 74, 75, 76)
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77. A two-wire load control device for controlling the amount of power delivered from an AC power source to an electrical load to a desired amount of power, the load control device comprising:
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a bidirectional semiconductor switch adapted to be coupled in series electrical connection between the AC power source and the electrical load for conducting a load current from the AC power source to the electrical load, the bidirectional semiconductor switch operable to be rendered conductive and to remain conductive independent of the magnitude of the load current conducted through the semiconductor switch; an analog control circuit coupled so as to conduct a control current through the electrical load and to generate a timing voltage that increases in magnitude with respect to time; and a drive circuit for receiving the timing voltage and rendering the bidirectional semiconductor switch conductive and non-conductive each half-cycle of the AC power source, so as to control the amount of power delivered to the electrical load to the desired amount.
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Specification