Load control device having a variable drive circuit
First Claim
1. A load control device, for controlling the amount of power delivered to an electrical load from a source of AC power, comprising:
- a controllably conductive device adapted to be coupled in series electrical connection between the source and the electrical load, the controllably conductive device having a control input to render the controllably conductive device conductive and non-conductive; and
a variable drive circuit coupled to the control input of the controllably conductive device to provide an impedance in series with the control input of the controllably conductive device;
wherein the variable drive circuit is operable to control the impedance in response to a temperature of the controllably conductive device.
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Accused Products
Abstract
A load control device for controlling the amount of power delivered to an electrical load from a source of AC power comprises a controllably conductive device and a variable gate drive circuit. The controllably conductive device is coupled in series electrical connection between the source and the electrical load to control the amount of power delivered to the load. The variable drive circuit is thermally coupled to the controllably conductive device and provides a continuously variable impedance in series with the control input of the controllably conductive device. The impedance of the variable drive circuit is operable to decrease as a temperature of the controllably conductive device increases and vice versa. Preferably, the variable drive circuit comprises an NTC thermistor. Accordingly, the switching times of the controllably conductive device, i.e., the times when the controllably conductive device is changing between the conductive and non-conductive states, remain constant, or alternatively decrease, as the temperature of the controllably conductive device increases.
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Citations
51 Claims
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1. A load control device, for controlling the amount of power delivered to an electrical load from a source of AC power, comprising:
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a controllably conductive device adapted to be coupled in series electrical connection between the source and the electrical load, the controllably conductive device having a control input to render the controllably conductive device conductive and non-conductive; and
a variable drive circuit coupled to the control input of the controllably conductive device to provide an impedance in series with the control input of the controllably conductive device;
wherein the variable drive circuit is operable to control the impedance in response to a temperature of the controllably conductive device. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20)
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21. A load control device, for controlling the amount of power delivered to an electrical load from a source of AC power, comprising:
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a controllably conductive device adapted to be coupled in series electrical connection between the source and the electrical load, the controllably conductive device having a control input for changing the controllably conductive device between a conductive state and a non-conductive state, the controllably conductive device characterized by a switching time when the controllably conductive device is changing between the conductive state and the non-conductive state; and
a drive circuit coupled to the control input of the controllably conductive device and operable to control the duration of the switching time is responsive to a temperature of the controllably conductive device. - View Dependent Claims (22, 23, 24, 25, 26)
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27. A drive circuit for a controllably conductive device in a load control device, the drive circuit comprising:
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a first resistor operable to be coupled in series electrical connection with a control input of the controllably conductive device; and
a thermally sensitive device coupled in parallel electrical connection with the first resistor and thermally coupled to the controllably conductive device, the thermally sensitive device operable to provide a variable impedance responsive to a temperature of the controllably conductive device. - View Dependent Claims (28, 29, 30, 31, 32, 33, 34, 35)
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36. A method for controlling a controllably conductive device in a load control device, the method comprising the steps of:
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providing a variable impedance in series electrical connection with a control input of the controllably conductive device; and
controlling the variable impedance in response to the temperature of the controllably conductive device. - View Dependent Claims (37, 38, 39, 40, 41, 42, 43)
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44. A method of controlling a controllably conductive device in a load control device, the method comprising the step of:
controlling the controllably conductive device between a conductive state and a non-conductive state for a switching time, the switching time responsive to a temperature of the controllably conductive device. - View Dependent Claims (45, 46, 47, 48, 49)
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50. A load control device, for controlling the amount of power delivered to an electrical load from a source of AC power, comprising:
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a controllably conductive device adapted to be coupled in series electrical connection between the source and the electrical load, the controllably conductive device having a control input for rendering the controllably conductive device conductive and non-conductive; and
a variable drive circuit coupled to the control input of the controllably conductive device for providing a continuously variable impedance in series with the control input of the controllably conductive device;
wherein the variable drive circuit is thermally coupled to the controllably conductive device such that the continuously variable impedance is operable to decrease as a temperature of the controllably conductive device increases and operable to increase as the temperature of the controllably conductive device decreases.
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51. A load control device, for controlling the amount of power delivered to an electrical load from an AC power source, comprising:
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a first controllably conductive device operable to conduct current from the source to the load during a positive half-cycle of the AC power source, the first controllably conductive device having a first control input to render the first controllably conductive device conductive and non-conductive;
a second controllably conductive device operable to conduct current from the source to the load during a negative half-cycle of the AC power source, the second controllably conductive device having a second control input to render the second controllably conductive device conductive and non-conductive;
a control circuit operable to independently render the first and second controllably conductive devices conductive and non-conductive;
a first variable drive circuit coupled in series electrical connection with the first control input of the first controllably conductive device to provide a first impedance in series with the first control input; and
a second variable drive circuit coupled in series electrical connection with the second control input of the second controllably conductive device to provide a second impedance in series with the second control input;
wherein the first impedance of the first variable drive circuit is operable to change substantially only in response to a first temperature of the first controllably conductive device and the second impedance of the second variable drive circuit is operable to change substantially only in response to a second temperature of the second controllably conductive device.
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Specification