US 2011/0031888 A1 · METHODS AND APPARATUS FOR CONTROLLING RESPECTIVE LOAD CURRENTS OF MULTIPLE SERIES-CONNECTED LOADS

Abstract

A lighting apparatus (100) includes one or more first LEDs (202) for generating a first spectrum of radiation (503), and one or more second LEDs (204) for generating a second different spectrum radiation (505). The first and second LEDs are electrically connected in series between a first node (516A) and a second node (516B), between which a series current (550) flows with the application of an operating voltage (516) across the nodes. A controllable current path (518) is connected in parallel with one or both of the first and second LEDs so as to at least partially divert the series current, such that a first current (552) through the first LED(s) and a second current (554) through the second LED(s) are different. Such current diversion techniques may be employed to compensate for shifts in color or color temperature of generated light during thermal transients, due to different temperature-dependent current-to-flux relationships for different types of LEDs.

Claims18

Dependent claims

A lighting apparatus, comprising:

at least one first LED for generating first radiation having a first spectrum;
at least one second LED for generating second radiation having a second spectrum different from the first spectrum, wherein:
the at least one first LED and the at least one second LED are electrically connected in series between a first node and a second node;
and
a series current flows between the first node and the second node when an operating voltage is applied across the first node and the second node;
and
a switching power supply for providing power factor correction and the operating voltage, the switching power supply controlling at least one controllable current path connected in parallel with one of the at least one first LED and the at least one second LED so as to at least partially divert the series current around the one of the at least one first LED and the at least one second LED, such that a first current through the at least one first LED and a second current through the at least one second LED are different.

4 more elements

A method for controlling a color temperature of white light generated by an LED-based lighting apparatus during a thermal transient, the LED-based lighting apparatus comprising at least one first LED for generating first radiation having a first spectrum and at least one second LED for generating second radiation having a second spectrum different from the first spectrum, wherein the white light results from a mixture of the first radiation and the second radiation, and wherein the at least one first LED and the at least one second LED are electrically connected in series between a first node and a second node and a series current flows between the first node and the second node when an operating voltage is applied across the first node and the second node, the method comprising:

A) generating a temperature signal representing a temperature proximate to the at least one first LED and the at least one second LED;
and
B) controlling, based on the temperature signal, at least one controllable current path connected in parallel with one of the at least one first LED and the at least one second LED so as to at least partially divert the series current around the one of the at least one first LED and the at least one second LED, such that a first current through the at least one first LED and a second current through the at least one second LED are different.

An apparatus for controlling a color temperature of white light generated by an LED-based light source during a thermal transient, the LED-based light source mounted to a thermally conductive substrate, the thermally conductive substrate having a recess (457) formed therein proximate to the LED-based light source, the apparatus comprising:

a printed circuit board (175) having a tab for insertion into the recess formed in the thermally conductive substrate;
a temperature sensor disposed on the tab of the printed circuit board, such that when the printed circuit board is inserted into the recess formed in the thermally conductive substrate, the temperature sensor is essentially embedded in the thermally conductive substrate proximate to the LED-based light source;
and
a plurality of components disposed on the printed circuit board and constituting a switching power supply for providing power factor correction and an operating voltage for the LED-based light source, the switching power supply comprising at least one integrated circuit (IC) controller.

1 more element

Dependencies are inferred from the claim text.

Methods and apparatus for controlling respective load currents of multiple series-connected loads

Life of this patent

Methods and apparatus for controlling respective load currents of multiple series-connected loads

Life of this patent

Abstract

Claims18