Low power and low EMI power stealing circuit for a control device
First Claim
1. A control device for controlling a supply of power from an AC power source to a load, the power source supplying a line voltage having a plurality of repeating cycles, the control device comprising:
- a first switch arranged in series electrical connection between the power source and the load, the first switch having a first state in which the first switch conducts electrical current and a second state in which the first switch is not conducting; and
a power stealing circuit arranged in parallel electrical connection to the first switch and comprising a charge storage, a second switch connected between a first terminal of the first switch and the charge storage device, and a semiconductor device, the power stealing circuit for;
detecting a zero crossing of the line voltage occurring at a beginning of each one of the plurality of cycles,at the zero crossing, directing through the second switch and towards the charge storage device an electrical current flowing through the load with the first switch in the second state,monitoring a voltage across terminals of the charge storage device and comparing the voltage across terminals of the charge storage device to a threshold value,if the voltage across terminals of the charge storage device reaches the threshold value, causing activation of the semiconductor device, the semiconductor device, when activated, bringing a voltage across terminals of the first switch towards zero volts with a predetermined rate, andbringing the first switch to the first state once the voltage across terminals of the first switch approaches zero volts.
1 Assignment
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Accused Products
Abstract
There is provided a device and a method for controlling a supply of power from an AC power source to a load. A switch is arranged in series electrical connection between the power source and the load, the switch having a first state in which the switch connects the load to the power source for supplying an electrical current from the power source to the load and a second state in which the switch disconnects the load from the power source. A power stealing circuit is arranged in parallel electrical connection to the switch and adapted to divert the electrical current away from the power source with the switch in the second state, the power stealing circuit comprising a linear semiconductor device adapted to control a rate of change of a first voltage across terminals of the switch upon the switch being brought to the first state.
52 Citations
23 Claims
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1. A control device for controlling a supply of power from an AC power source to a load, the power source supplying a line voltage having a plurality of repeating cycles, the control device comprising:
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a first switch arranged in series electrical connection between the power source and the load, the first switch having a first state in which the first switch conducts electrical current and a second state in which the first switch is not conducting; and a power stealing circuit arranged in parallel electrical connection to the first switch and comprising a charge storage, a second switch connected between a first terminal of the first switch and the charge storage device, and a semiconductor device, the power stealing circuit for; detecting a zero crossing of the line voltage occurring at a beginning of each one of the plurality of cycles, at the zero crossing, directing through the second switch and towards the charge storage device an electrical current flowing through the load with the first switch in the second state, monitoring a voltage across terminals of the charge storage device and comparing the voltage across terminals of the charge storage device to a threshold value, if the voltage across terminals of the charge storage device reaches the threshold value, causing activation of the semiconductor device, the semiconductor device, when activated, bringing a voltage across terminals of the first switch towards zero volts with a predetermined rate, and bringing the first switch to the first state once the voltage across terminals of the first switch approaches zero volts. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A power stealing circuit for a control device controlling a supply of power from an AC power source to a load, the power source supplying a line voltage having a plurality of repeating cycles, the control device comprising a first switch arranged in series electrical connection between the power source and the load and having a first state in which the first switch conducts electrical current and a second state in which the first switch is not conducting, the power stealing circuit comprising:
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a charge storage device arranged in parallel electrical connection with the first switch; a second switch connected between a first terminal of the first switch and the charge storage device, the second switch for, at a zero crossing of the line voltage occurring at a beginning of each one of the plurality of cycles, directing towards the charge storage device an electrical current flowing through the load with the first switch in the second state; and a semiconductor device arranged in parallel electrical connection with the first switch, the semiconductor device being activated when a voltage across terminals of the charge storage device reaches a threshold value, the semiconductor device, when activated, bringing a voltage across terminals of the first switch towards zero volts with a predetermined rate before the first switch is brought to the first state. - View Dependent Claims (11, 12, 13, 14, 15, 16, 17)
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18. A method for controlling a supply of power from an AC power source to a load having a first switch arranged in series electrical connection therebetween, the first switch having a first state in which the first switch conducts electrical current and a second state in which the first switch is not conducting, the method comprising:
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directing, through a second switch, an electrical current flowing through the load with the first switch in the second state towards a charge storage device arranged in parallel electrical connection with the first switch, the second switch connected between a first terminal of the first switch and the charge storage device; comparing a voltage across terminals of the charge storage device to a threshold value; when the voltage across terminals of the charge storage device reaches the threshold value, outputting a control signal for activating a semiconductor device arranged in parallel electrical connection to the first switch, the semiconductor device, when activated, controllably bringing towards zero volts a voltage across terminals of the first switch; and applying, when a line voltage supplied by the power source approaches zero volts, a first pulse on a gate terminal of the first switch to trigger the first switch, thereby bringing the first switch to the first state. - View Dependent Claims (19, 20, 21)
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22. A two-wire line voltage thermostat for controlling a supply of power from an AC power source to a load, the power source supplying a line voltage having a plurality of repeating cycles, the thermostat comprising:
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a first switch arranged in series electrical connection between the power source and the load, the first switch having a first state in which the first switch conducts electrical current and a second state in which the first switch is not conducting; a power stealing circuit arranged in parallel electrical connection to the first switch and comprising a charge storage device, a second switch connected between a first terminal of the first switch and the charge storage device, and a semiconductor device, the power stealing circuit for; at a zero crossing of the line voltage occurring at a beginning of each one of the plurality of cycles, directing through the second switch and towards the charge storage device an electrical current flowing through the load with the first switch in the second state, if a voltage across terminals of the charge storage device reaches a threshold value, causing activation of the semiconductor device, the semiconductor device, when activated, bringing a voltage across terminals of the first switch towards zero volts with a predetermined rate, and bringing the first switch to the first state once the voltage across terminals of the first switch approaches zero volts; and a communications module adapted to receive one or more input radio-frequency signals indicative of instructions to operate at least one of the load and the thermostat. - View Dependent Claims (23)
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Specification