LED LIGHTING WITH INCANDESCENT LAMP COLOR TEMPERATURE BEHAVIOR

• US 20120134148A1
• Filed: 03/11/2010
• Published: 05/31/2012
• Est. Priority Date: 03/12/2009
• Status: Active Grant

• Current Assignee: Signify Holding B.V. (Signify N.V.)
• Original Assignee: Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Inventors: Ter Weeme, Berend Jan Willem, Jans, William Peter Mechtildis Marie, Van Dijk, Erik Martinus Hubertus Petrus, Julicher, Paul Johannes Marie, Hontele, Bertrand Johan Edward, Zijlman, Theo Gerrit, Akdag, Gazi
• Granted Patent: US 8,587,205 B2
• Time in Patent Office: Days
• US Class Current: 362/231
• CPC Class Codes: H05B 45/18 using temperature feedback
• CPC Class Codes: H05B 45/20 Controlling the colour of the light
• CPC Class Codes: H05B 45/3577 Emulating the dimming characteristics, brightness or colour temperature of incandescent lamps
• CPC Class Codes: H05B 45/375 using buck topology

Abstract

In a lighting device, sets of LEDs are employed using the natural characteristics of the LEDs to resemble incandescent lamp behavior when dimmed, thereby obviating the need for sophisticated controls. A first set of at least one LED produces light with a first color temperature, and a second set of at least one LED produces light with a second color temperature. The first set and the second set are connected in series, or the first set and the second set are connected in parallel, possibly with a resistive element in series with the first or the second set. The first set and the second set differ in temperature behavior, or have different dynamic electrical resistance. The light device produces light with a color point parallel and close to a blackbody curve.

Claims

1. Lighting device (100), comprising:

an LED driver (101) capable of generating dimmed LED current;

a two-terminal LED module (110;

300;

400;

500;

600), having two input terminals (111, 112) for receiving an input current (Iin) from the LED driver (101) and comprising;

a first LED group (113) comprising at least one first type LED for producing light having a first color temperature;

a second LED group (114) comprising at least one second type LED for producing light having a second color temperature different from the first color temperature;

wherein the module is capable of supplying LED currents to the LED groups, these LED currents being derived from the input current (Iin);

wherein the LED module produces a light output having at least a light output contributions from the first LED group (113) and from the second LED group (114);

and wherein the module is designed to vary the individual LED currents in the individual LED groups in dependency of the average magnitude of the received input current (Iin), such that the color point of the light output of the module varies as a function of the input current magnitude.

2. Lighting device according to claim 1, wherein the LED module is designed to vary the individual LED currents in the individual LED groups such that the color point of the light output of the module on dimming follows a black body curve.

3. Lighting device according to claim 1, wherein the LED module is designed to vary the individual LED currents in the individual LED groups such that the color behavior of the light output of the module on dimming resembles the color behavior of an incandescent lamp.

4. Lighting device according to claim 1, wherein the lighting device is configured to produce light with a color temperature CT at an average current of x %, CT(x %), supplied to the terminals following the relationship:

CT(x%)=CT(100%)*(x/100) 1/9.5

5. Lighting device according to claim 1, wherein the first group of LEDs has a varying first luminous flux output as a function of junction temperature of the first type LED, and the second group of LEDs has a varying second luminous flux output as a function of junction temperature of the second type LED, and wherein, at varying junction temperatures, the ratio of the first luminous flux output to the second luminous flux output varies;

and wherein preferably the first color temperature is lower than the second color temperature, while, at decreasing junction temperatures, the ratio of the first luminous flux output to the second luminous flux output increases, and vice versa.

6. Lighting device according to claim 1, wherein a gradient of the first luminous flux output as a function of junction temperature of the first type LED differs from a gradient of the second luminous flux output as a function of junction temperature of the second type LED;

and wherein preferably the first color temperature is lower than the second color temperature, while the absolute value of the gradient of the first luminous flux output as a function of temperature of the first type LED is higher than the gradient of the second luminous flux output as a function of temperature of the second type LED.

7. Lighting device according to claim 1, wherein a thermal resistance to ambient of the first group of LEDs differs from the thermal resistance to ambient of the second group of LEDs;

and wherein preferably the first color temperature is lower than the second color temperature, while the thermal resistance to ambient of the first group of LEDs is higher than the thermal resistance to ambient of the second group of LEDs.

8. Lighting device according to claim 1, wherein the first group of LEDs has a first dynamic electrical resistance, and the second group of LEDs has a second dynamic electrical resistance.

9. Lighting device according to claim 1, wherein one of the first group of LEDs and the second group of LEDs is connected in series with a resistor, and wherein this series arrangement is connected in parallel to the other one of the first group of LEDs and the second group of LEDs, and wherein this parallel arrangement is connected between the two input terminals (111, 112) of the LED module;

and wherein preferably the resistor is a negative temperature coefficient, NTC, type resistor.

10. Lighting device according to any of the preceding claims, wherein the first type LED is an AlInGaP type LED, and/or wherein the second type LED is an InGaN type LED.

11. Lighting device according to claim 1, wherein the LED module comprises an electronic division circuit (115) capable of controlling the LED currents (I1, I2) in said two groups (113, 114) of LEDs as a function of the input current level received at the input of the LED module.

12. Lighting device according to claim 11, wherein the electronic division circuit is capable of supplying the two groups of LEDs with constant current and of controlling the LED currents (I1, I2) such that the following formulas apply:

I1=p·

Iin and I2=q·

Iin, and p+q=1

with Iin denoting the input current magnitude,

I1 denoting the current magnitude in the first group of LEDs,

I2 denoting the current magnitude in the second group of LEDs;

wherein there is at least a range of input current magnitudes where dp/d(Iin) is always positive and dq/d(Iin) is always negative.

13. Lighting device according to claim 12, wherein the LED module comprises:

a current regulating element (320) arranged in series with one of said groups of LEDs, this series arrangement being coupled in parallel to another of said groups of LEDs;

a current sensing element (350) arranged for sensing the input current received at the input terminals of the LED module;

and a regulator driver (310) receiving a sense output signal from the sensing element and driving the current regulating element on the basis of this sense output signal.

14. Lighting device according to claim 11, wherein the electronic division circuit (515) comprises a controllable switch (501) for temporally dividing de received input current (Iin) between the two groups of LEDs;

a control device (520) for controlling the switch (501) at a switching period T such that the input current is passed on to the first group of LEDs for a first time duration t1 and the input current is passed on to the second group of LEDs for a second time duration t2, with t1+t2=T;

a current sensing element (116) arranged for sensing the input current received at the input terminals of the LED module;

the control device being coupled to receive a sense output signal from the sensing element and being designed to vary the ratio t1/t2 of the switching of the switch on the basis of said sense output signal, such that there is at least a range of input current magnitudes where dt1(Iin) is always positive and dt2(Iin) is always negative.

15. Lighting device according to claim 11, wherein the second group of LEDs (114) is supplied by a current converter (601) having its input terminals connected in parallel to the first group of LEDs (113);

wherein the current converter comprises a control circuit (620) receiving a sense output signal from a current sensing element (116) sensing the input current of the LED module;

and wherein this control circuit (620) is designed to control the current converter (601) on the basis of the sense output signal received from the current sensing element (116).

16. Lighting device according to claim 11, wherein the first group of LEDs (113) is supplied by a first current converter (730) and the second group of LEDs (114) is supplied by a second current converter (740), and wherein these two current converter have their input terminals connected in series;

wherein the LED module comprises a control circuit (720) receiving a sense output signal from a current sensing element (116) sensing the input current of the LED module;

and wherein this control circuit (720) is designed to control the current converters (730, 740) on the basis of the sense output signal received from the current sensing element (116).