Circuit for operating light emitting diodes (leds)
AssigneeTridonicatco Schweiz AG
InventorsMichael Zimmermann, Eduardo Pereira
Life of this patent
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Abstract
The present invention relates to a circuit arrangement for supplying power to, and for controlling, light-emitting diodes for illuminating, and to a method therefor. The invention provides a driver circuit for providing an operating current for operating at least one light-emitting diode, wherein the operating current has different positive intensities.
Claims17
A driving circuit for provision of an operating current for at least one light emitting means, the driving circuit comprising:
- a switched converter having a switch controlled by a control circuitry,
- wherein a choke is charged when the control circuitry control the switch in its conducting state and the choke is de-charged when the control circuits controls the switch in its non-conducting state,
- wherein by supplying an external signal or an internal feedback signal to the control circuitry, the control circuitry is designed to adapt the clocking of the switch in order to adapt the operating mode of the switched converter.
A method for dimming at least one LED using a switched converter for supplying the at least one LED with electrical power, the switched converter comprising a switch for charging a choke when the switch is conducting and decharging the choke when the switch is non-conducting, which comprises performing the dimming selectively via at least two dimming modes, including:
- (1) a first dimming mode, in which the at least one LED is dimmed by controlling the switch such that the current through the choke has an essentially triangular shape, wherein the dimming is achieved by adjusting the time period for allowing the choke current to rise to a peak value by switching on a switch of the switched converter,
- wherein the fall of the choke current, caused by switching off the switch of the switched converter at the peak, is stopped by switching on the switch of the switched converter at the latest when the falling choke current reaches zero, and
- (2) a second dimming mode, in which, in addition or alternatively to the adjustment of the time period for allowing the current to rise to a peak value, wherein the dimming is achieved by adjusting the time period between the falling choke current reaching zero and the switching-on of the switch of the switched converter in order to cause the choke current to raise again.
A driving circuit for provision of an operating current for at least one LED, wherein a desired value for the operating current is specified and spread by a control unit temporally into at least two different operating current values of greater than zero, in such a way that the time-average value corresponds to the desired value.
A method for improving the color rendering index or for adjusting the color of a light emitting diode, which comprises providing operating current or current flowing through the light emitting diode with different positive intensities.
Dependencies are inferred from the claim text.