LED lighting device with chopper circuit and dimming control method
First Claim
1. An LED lighting device comprising:
- a DC power source having positive and negative output terminals;
a switching element coupled across the output terminals of the DC power source;
an inductor coupled on a first end to the switching element and effective to receive and store energy when the switching element is turned on;
a lighting device output connector coupled to a second end of the inductor and effective to receive a semiconductor light emitting element;
a regeneration diode coupled to the node between the inductor and the switching element and effective to discharge energy stored in the inductor to the output connector when the switching element is turned off;
a current sensor effective to detect current flowing to the switching element; and
a control circuit effective in a normal operation toreceive the detected current value from the current sensor;
compare the detected current value to a predetermined value;
decrease a gate drive signal to turn off the switching element when the detected current value reaches the predetermined value; and
increase a gate drive signal to turn on the switching element when energy discharge of the inductor is completed;
the control circuit further effective in a dimming operation toreceive a dimming control signal, andintermittently disable the normal operation in accordance with the dimming control signal.
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Accused Products
Abstract
A lighting device is provided for lighting control of an LED module based on an externally provided dimming control signal. A chopper circuit includes a switch coupled across a DC input and an inductor which receives and stores energy when the switch is turned on, and discharges energy to the LED module when the switch is turned off. A control circuit determines a current value to the switch, and compares the current value to a predetermined value. During normal operation, the switch is turned off when the detected current value reaches the predetermined value and turned back on when inductor discharge has completed. During a dimming operation, the normal operation is intermittently disabled in accordance with the dimming control signal. The dimming control signal may be a low-frequency PWM signal, with the lighting output being dimmed as a result of a duty ratio of the PWM signal.
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Citations
20 Claims
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1. An LED lighting device comprising:
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a DC power source having positive and negative output terminals; a switching element coupled across the output terminals of the DC power source; an inductor coupled on a first end to the switching element and effective to receive and store energy when the switching element is turned on; a lighting device output connector coupled to a second end of the inductor and effective to receive a semiconductor light emitting element; a regeneration diode coupled to the node between the inductor and the switching element and effective to discharge energy stored in the inductor to the output connector when the switching element is turned off; a current sensor effective to detect current flowing to the switching element; and a control circuit effective in a normal operation to receive the detected current value from the current sensor; compare the detected current value to a predetermined value; decrease a gate drive signal to turn off the switching element when the detected current value reaches the predetermined value; and increase a gate drive signal to turn on the switching element when energy discharge of the inductor is completed; the control circuit further effective in a dimming operation to receive a dimming control signal, and intermittently disable the normal operation in accordance with the dimming control signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. An LED lighting device for a video camera having a shutter speed, the lighting device comprising:
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a DC power source having positive and negative output terminals; a switching element coupled across the output terminals of the DC power source; an inductor coupled on a first end to the switching element and effective to receive and store energy when the switching element is turned on; a lighting device output connector coupled to a second end of the inductor and effective to receive a semiconductor light emitting element; a regeneration diode coupled to the node between the inductor and the switching element and effective to discharge energy stored in the inductor to the output connector when the switching element is turned off; a current sensor effective to detect current flowing to the switching element; and a control circuit effective in a normal operation to receive the detected current value from the current sensor; compare the detected current value to a predetermined value; decrease a gate drive signal to turn off the switching element when the detected current value reaches the predetermined value; and increase a gate drive signal to turn on the switching element when energy discharge of the inductor is completed; the control circuit further effective in a dimming operation to receive a PWM dimming control signal having a frequency set to an integral multiple of an inverse of shutter speed of the video camera, and intermittently disable the normal operation in accordance with the dimming control signal. - View Dependent Claims (10, 11, 12, 13, 14, 15, 16)
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17. A method of controlling lighting output for a lighting device mounted on a video camera, the method comprising:
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identifying a shutter speed associated with the video camera; providing the lighting device with a chopper circuit further comprising a switching element and an inductance element, the chopper circuit effective to convert an input DC signal into an output signal for powering a semiconductor light emitting element; detecting a current value to the switching element; comparing the detected current value to a predetermined value; decreasing a gate drive signal to turn off the switching element when the detected current value reaches the predetermined value; increasing a gate drive signal to turn on the switching element when energy discharge of the inductor is completed, the steps of decreasing and increasing the gate drive signal defining a normal operation for the lighting device; providing a PWM dimming control signal having a frequency set to an integral multiple of an inverse of shutter speed of the video camera; and intermittently interrupting operation of the switching element in accordance with the PWM dimming control signal, the interrupting step defining a dimming operation for the lighting device. - View Dependent Claims (18, 19, 20)
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Specification