Back to results
US 9,313,847 B2Granted
LED light source
AssigneeKoninklijke Philips N.V.
InventorsHaimin Tao, Martinus Petrus Creusen, Ralph Kurt
Life of this patent
Estimating the term…
Abstract
LED light source comprising a string of LED loads (LED1-LED4) supplied by a rectified mains voltage. The number of LED loads carrying current is increased as the momentary amplitude of the rectified mains voltage increases, and is decreased as the momentary amplitude of the rectified mains voltage decreases. The order in which the LED loads start carrying a current and the order in which the LED loads stop carrying a current is reversed for each half period of the mains.
Claims9
A LED light source comprising
- a first input terminal and a second input terminal for connection to a supply voltage source supplying a low-frequency AC supply voltage with a frequency f,
- a rectifier coupled to the input terminals for rectifying the low-frequency AC supply voltage,
- a series arrangement comprising N LED loads, wherein N is an integer greater than or equal to 2, a first and a second end of said series arrangement being coupled to a first output terminal and a second output terminal of the rectifier, respectively,
- control means for, subsequently, in a first operating state during half a period of the low frequency AC voltage, making the LED loads carry current, one after another in a first order and in dependence on the momentary amplitude of the low-frequency AC supply voltage when the amplitude increases, and for subsequently making the LED loads stop carrying current, one after another and in a second order, that is reversed with respect to the first order and in dependence on the momentary amplitude of the low-frequency AC supply voltage when the amplitude decreases, and for, subsequently, in a second operating state during half a period of the low frequency AC voltage, making the LED loads carry current, one after another and in the second order and in dependence on the momentary amplitude of the low frequency AC supply voltage when the amplitude increases, and for subsequently making the LED loads stop carrying current, one after another in the first order, and in dependence on the momentary amplitude of the low-frequency AC supply voltage when the amplitude decreases, and wherein the control means is further equipped with circuitry for changing the operating state at every zero crossing of the low-frequency AC supply voltage.
1 more element
A LED light source comprising
- a first input terminal and a second input terminal for connection to a supply voltage source supplying a low-frequency AC supply voltage with a frequency f,
- a rectifier coupled to the input terminals for rectifying the low-frequency AC supply voltage,
- a series arrangement comprising N LED loads, wherein N is an integer greater than or equal to 2, a first and a second end of said series arrangement being coupled to a first output terminal and a second output terminal of the rectifier respectively,
- control means for, subsequently, making the N LED loads carry current during each half period of the low-frequency AC supply voltage, one after another in a first order, when the amplitude of the low-frequency AC supply voltage increases, and for subsequently making the N LED loads stop carrying current one after another in a second order that is reversed with respect to the first order, when the amplitude of the low-frequency AC supply voltage decreases, wherein in each of N subsequent half periods of the low-frequency AC supply voltage, the nth LED load that is made to conduct current differs from the nth LED load that is made to conduct current in every other half period of the N subsequent half periods for each value of n, wherein n is an integer and 1≦n≦N, wherein n is an integer≦0.5N.
1 more element
A method of supplying power to a LED light source equipped with a series arrangement of N LED loads, comprising the steps of
- providing a low-frequency AC supply voltage with a frequency f,
- rectifying the low-frequency AC supply voltage,
- supplying the rectified AC supply voltage to the series arrangement comprising N LED loads, wherein N is an integer greater than or equal to 2, and
- subsequently, in a first operating state during half a period of the low frequency AC supply voltage,
- making the LED loads carry a current, one after another, starting with a first LED load that is closest to a first end of the series arrangement, in dependence on the momentary amplitude of the low-frequency AC supply voltage, when the amplitude increases, and
- subsequently, making the LED loads stop carrying current, one after another, starting with the Nth LED load, in dependence on the momentary amplitude of the low-frequency AC supply voltage, when the amplitude decreases, and
- subsequently, in a second operating state during half a period of the low frequency AC supply voltage,
- making the LED loads carry current, one after another, starting with the Nth LED in dependence on the momentary amplitude of the low-frequency AC supply voltage, when the amplitude increases, and
- subsequently, making the LED loads stop carrying current, one after another, starting with the first LED load, in dependence on the momentary amplitude of the low-frequency AC supply voltage, when the amplitude decreases, and
- changing the operating state at every zero crossing of the low-frequency AC supply voltage.
7 more elements
Dependencies are inferred from the claim text.