Two-wire dimmer with power supply and load protection circuit in the event of switch failure
First Claim
1. A dimmer circuit for providing AC power from an AC voltage source to an inductive lighting load disposed in series with the dimmer circuit comprising:
- a bidirectional semiconductor switch having at least one control electrode provided with a control signal for controlling the amount of power provided to the load, the switch in normal operation being able to be controlled to block voltage in first and second opposite polarity half-cycles of the AC voltage source but in a failure mode being able to block the AC voltage source in only one half-cycle of the AC voltage source and not being able to block the AC voltage source in the second opposite polarity half-cycle;
a controller for the switch for determining if said failure mode of the switch occurs;
a power supply coupled across said dimmer circuit for supplying power to the controller;
the controller controlling the switch if such failure mode occurs so as to;
drive the switch into substantially full conduction during most of the half-cycle which the switch is able to control; and
drive the switch into non-conduction for a brief interval of time during that same half-cycle so as to prevent a DC voltage component supplied to the load from exceeding a predetermined level below which excessive transformer heating does not occur, thereby minimizing overheating of the inductive load and enabling the power supply for the controller to be provided with sufficient voltage from the AC voltage source to enable the controller to continue to operate.
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Accused Products
Abstract
A dimmer circuit for providing AC power from an AC voltage source to an inductive lighting load disposed in series with the dimmer circuit, comprising: a bidirectional semiconductor switch having at least one control electrode provided with a control signal for controlling the amount of power provided to the load, the switch in normal operation being able to be controlled to block voltage in first and second opposite polarity half-cycles of the AC voltage source but in a failure mode being able to block the AC voltage source in only one polarity half-cycle of the AC voltage source and not being able to block the AC voltage source in the second opposite polarity half-cycle; a controller for the switch for determining if said failure mode of the switch occurs which can cause an asymmetry between the half-cycles delivered to the load and thus a DC voltage component to be delivered to the load; a power supply for supplying power to the controller and provided with power across the dimmer circuit; the controller controlling the switch if such failure mode occurs so as to: drive the switch into substantially full conduction during most of the half-cycle which the switch is able to control; and drive the switch into non-conduction for a brief duration of time during that same half-cycle so as to prevent a DC voltage component supplied to the load from exceeding a predetermined level below which excessive transformer heating does not occur, thereby minimizing overheating of the inductive load and enabling the power supply for the controller to be provided with sufficient voltage from the AC voltage source to enable the controller to continue to operate.
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Citations
43 Claims
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1. A dimmer circuit for providing AC power from an AC voltage source to an inductive lighting load disposed in series with the dimmer circuit comprising:
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a bidirectional semiconductor switch having at least one control electrode provided with a control signal for controlling the amount of power provided to the load, the switch in normal operation being able to be controlled to block voltage in first and second opposite polarity half-cycles of the AC voltage source but in a failure mode being able to block the AC voltage source in only one half-cycle of the AC voltage source and not being able to block the AC voltage source in the second opposite polarity half-cycle;
a controller for the switch for determining if said failure mode of the switch occurs;
a power supply coupled across said dimmer circuit for supplying power to the controller;
the controller controlling the switch if such failure mode occurs so as to;
drive the switch into substantially full conduction during most of the half-cycle which the switch is able to control; and
drive the switch into non-conduction for a brief interval of time during that same half-cycle so as to prevent a DC voltage component supplied to the load from exceeding a predetermined level below which excessive transformer heating does not occur, thereby minimizing overheating of the inductive load and enabling the power supply for the controller to be provided with sufficient voltage from the AC voltage source to enable the controller to continue to operate. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27)
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28. A method for operating a dimmer circuit for providing AC power from an AC voltage source to an inductive lighting load disposed in series with the dimmer circuit, wherein the dimmer circuit comprises a bidirectional semiconductor switch having at least one control electrode provided with a control signal for controlling the amount of power provided to the load, the switch in normal operation being able to be controlled to block voltage in first and second opposite polarity half-cycles of the AC voltage source but in a failure mode being able to block the AC voltage source in only one half-cycle of the AC voltage source and not being able to block the AC voltage source in the second opposite polarity half-cycle;
- a power supply coupled across the dimmer circuit for supplying power to a control circuit for the dimmer circuit;
the method comprising;
determining if said failure mode of the switch occurs which can cause an asymmetry between the half-cycles delivered to the load and thus a DC voltage component to be delivered to the load;
driving the switch into substantially full conduction during most of the half-cycle which the switch is able to control; and
driving the switch into non-conduction for a brief interval of time during that same half-cycle so as to prevent a DC voltage component supplied to the load from exceeding a predetermined level below which excessive transformer heating does not occur, thereby minimizing overheating of the inductive load and enabling the power supply for the control circuit to be provided with sufficient voltage from the AC voltage source to enable the control circuit to continue to operate. - View Dependent Claims (29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43)
- a power supply coupled across the dimmer circuit for supplying power to a control circuit for the dimmer circuit;
Specification