AC-powered, microprocessor-based, dimming LED power supply
First Claim
1. A pulse width modulation-based dimming circuit for adjusting DC constant current from a phase-controlled, AC power source to at least one light source, the circuit comprising:
- a phase-angle detection circuit that senses input voltage from the AC power source and provides a DC pulse signal when the sensed input voltage exceeds a predetermined threshold voltage;
a power stage that is electrically coupled to the at least one light source and that is adapted to control delivery of power to the at least one light source;
a dv/dt filter that is electrically coupled to the AC power source and to the power stage and that is adapted to filter out voltage transients and to prevent reverse current ring back;
a controller power supply that provides power to the power stage; and
a controller that is adapted to establish a first pulse width modulation (PWM) switching frequency;
to adjust a duty cycle of a second PWM signal; and
to adjust a peak level of the current during the duty cycle, based on the DC pulse signals from the phase-angle detection circuit and on sensed current levels from the at least one light source.
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Accused Products
Abstract
A dimmable, light-emitting diode (LED) power supply adapted to provide a direct current (DC), constant current (“constant current source”) from a conventional, phase-controlled 120 VAC, 60 Hz power source is disclosed. The constant current source of the present invention utilizes two processes to control dimming. In a first process, the phase angle of the input voltage is used to control the duty cycle of a line frequency pulse width modulation (PWM). In a second process, a proportional-current limit adjustment is used to control the average current to the LED during the ON time of the line frequency by PWM. As a result, at relatively low phase angles, peak currents can be lowered, reducing flicker and improving the audible noise levels generated by the circuit.
117 Citations
23 Claims
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1. A pulse width modulation-based dimming circuit for adjusting DC constant current from a phase-controlled, AC power source to at least one light source, the circuit comprising:
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a phase-angle detection circuit that senses input voltage from the AC power source and provides a DC pulse signal when the sensed input voltage exceeds a predetermined threshold voltage; a power stage that is electrically coupled to the at least one light source and that is adapted to control delivery of power to the at least one light source; a dv/dt filter that is electrically coupled to the AC power source and to the power stage and that is adapted to filter out voltage transients and to prevent reverse current ring back; a controller power supply that provides power to the power stage; and a controller that is adapted to establish a first pulse width modulation (PWM) switching frequency;
to adjust a duty cycle of a second PWM signal; and
to adjust a peak level of the current during the duty cycle, based on the DC pulse signals from the phase-angle detection circuit and on sensed current levels from the at least one light source. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
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15. A constant current source to control dimming of at least one light source, the source comprising:
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means for sensing an input voltage from a phase-controlled, AC power source; means for pulse width modulation-based dimming, which means is adapted to provide power (current) to the at least one light source whenever the sensed input voltage exceeds a predetermined voltage threshold; and means for proportional-current dimming that is adapted to modify power to the at least one light source when a current sensed at said at least one light source is greater than or equal to a limiting, peak current. - View Dependent Claims (16, 17, 18)
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19. A proportional-current light-dimming device for controlling current to at least one light source at low and relatively-low phase angles of an input voltage, the device comprising:
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current sensing means for sensing a current flowing through the at least one light source; a processing unit that is adapted to calculate a limiting, peak current based on the input voltage; a main switch driving circuit that is adapted to compare a signal associated with the sensed current with the limiting, peak current; and a main switch that is adapted to increase current to the at least one light source when the signal associated with the sensed current is less than the limiting, peak current and to decrease current to said at least one light source when said signal associated with said sensed current is greater than or equal to said limiting, peak current.
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20. A method of controlling current to at least one light source to control light-dimming using a dimming device, the method comprising:
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sensing an input voltage from a phase-controlled AC source; sensing a current flowing through the at least one light source; calculating a limiting, peak current using the input voltage; providing pulse width modulation-dimming signals to the at least one light source whenever the sensed current is less than the limiting, peak current; providing proportional-current dimming signals to the at least one light source whenever the limiting, peak current is less than or equal to the sensed current. - View Dependent Claims (21, 22, 23)
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Specification