Light emitting diode lamp

An LED lamp includes a first LED string and a second LED string connected in parallel to each other and a variable resistor connected in series with one of the first and second LED strings. The first LED string provides a first color temperature. The LED string provides a second color temperature difference from the first color temperature. The variable resistor includes a resistance track with resistance coils wound thereon and a slider moveable along the resistance track. When a position of the slider of the variable resistor is changed, an electric current flowing through the one of the first and second strings is changed accordingly to adjust the color temperature of the LED lamp.

BACKGROUND

1. Technical Field

The present disclosure relates to an illumination device, and particularly to a light emitting diode (LED) lamp providing an adjustable color temperature.

2. Description of Related Art

At present, light emitting diodes (LEDs) are widely used due to high brightness, wide color gamut and rapid response speed. With the rapid development of decorative illuminations for both commercial and residential, the demand for using LEDs in lamp for decorative illumination is ever increasing.

It is important for the decorative illumination to have a sufficient light energy in a correct color temperature since the color temperature affects the sensation of user's eyes. Thus, there is a need for a lamp which can emit light with an adjustable color temperature. However, the function of most conventional LED lamps for adjusting the color temperature is achieved by varying pulse width modulation (PWM) signals supplied thereto. Therefore, drive circuit for the LED lamps must include a PWM drive chip and many complicated peripheral circuits, which badly affects an illumination efficiency of the LED lamps and increases costs.

It is thus desirable to provide an LED lamp which can overcome the described limitations.

DETAILED DESCRIPTION

Reference will now be made to the drawing figures to describe the present LED lamp in detail.

Referring toFIG. 1, an LED lamp90according to an exemplary embodiment of the present disclosure is shown. The LED lamp90includes an LED light source10, an envelope20covering the LED light source10therein, a heat sink30thermally connected with the LED light source10, a connecting head40electrically connected with the LED light source10, and an adjustment button50.

The LED light source10includes a circular substrate11and a plurality of LEDs12mounted on the substrate11. Referring toFIG. 2, the LEDs12includes a plurality of first LEDs121connected in series with each other and providing a first color temperature and a plurality of second LEDs123connected in series with each other and providing a second color temperature different from the first color temperature. For providing a broad emission bandwidth, the first LEDs121emit cold color with the first color temperature of about 6500K, and the second LEDs123emit warm color with the second color temperature of about 2800K in this embodiment.

The envelope20is a hollow hemisphere shape, and defines an opening at a bottom side thereof. The envelope20connects a periphery edge of the substrate11to seal the opening, thereby defining a sealed receiving space therebetween for receiving the LED light source10therein.

The heat sink30is integrally made of a metal with good heat conductivity such as aluminum, copper or an alloy thereof. The heat sink30includes a circular top surface31, a circular bottom surface32less than the top surface31and a tapered side surface33interconnected between the top and bottom surfaces31,32. The LED light source10is mounted on the top surface31. A plurality of axially grooves35is defined in the side surface33of the heat sink30. The grooves35are equally spaced from each other along a circumference direction of the side surface33of the heat sink30. The grooves35can increase an outer surface area of the heat sink30, to thus promote a heat dissipation performance of the heat sink30. An elongated cutout36is defined at a bottom portion of the side surface33of the heat sink30.

The adjustment button50is received in the elongated cutout36. The adjustment button50is slidably along the elongated cutout36, to adjust a color temperature of the LED lamp90. Alternatively, the adjustment button50can be a rotatable button which is rotatablely around a central axis thereof, to adjust the color temperature of the LED lamp90.

The connecting head40is electrically connected with the LED light source10, and mounted on the bottom surface32of the heat sink30. When used, the connecting head40of the LED lamp90electrically connects a direct current (DC) power source60(FIGS. 2,3and4) or an alternating current (AC) power source70(FIGS. 5and6), such that the LED light source10can get an electrical power from the DC power source60or the AC power source70to emit light.

Referring back toFIG. 2, a circuit100is shown for illustrating the LED lamp90electrically connected to the DC power source60for working. The first LEDs121are connected in series to form a first LED string101. The second LEDs123are connected in series to form a second LED string102. The first LED string101and the second LED string102are connected in parallel. A variable resistor80is connected in series with the first LED string101. The variable resistors80includes a resistance track84with resistance coil wound around thereon, first and second connecting posts82,83at two opposite ends of the resistance track84, respectively, and a slider81moveable along the resistance track84to change a resistance between the slider81and a corresponding connecting post82,83.

In this circuit100, anodes of the first and second LED strings101,102connect a positive pole of the DC power source60. One of the first and second connecting posts82,83, i.e., the first connecting post82in this embodiment, of the variable resistor80connects a cathode of the first LED string101. The slider81of the variable resistor80connects a negative pole of the DC power source60. Cathode of the second LED string102connects the negative pole of the DC power source60directly. With this configuration, a portion of the resistance between the first connecting post82and the slider81of the variable resistor80is connected in series with the first LED string101. When the slider81of the variable resistor80is moved along the resistance track84towards the first connecting post82, the resistance between the first connecting post82and the slider81is reduced, and when the slider81of the variable resistor80is moved along the resistance track84towards the second connecting post83, the resistance between the first connecting post82and the slider81is increased.

The slider81of the variable resistor80is connected with the adjustment button50. When the adjustment button50is moved upwardly along the elongated cutout36, the slider81of the variable resistor80follows the adjustment button50to move along the resistance track84towards the first connecting post82. Thus, the portion of the resistance connected in series with the first LED string101of the variable resistor80is reduced. Accordingly, a first electric current flowing through the first LED string101is increased, thereby increasing a light intensity of light emitted from the first LED string101, while a second electric current flowing through the second LED string102remains unchanged. Due to a light of the LED lamp90is a mixture of the light of the first LED string101and the light of the second LED string102, when the light intensity of the first LED string101is increased, the color temperature of the LED lamp90is more closer to the color temperature of the first LED string101, such that the color temperature of the LED lamp90is increased.

On the contrary, when the adjustment button50is moved downwardly along the elongated cutout36, the slider81of the variable resistor80follows the adjustment button50to move towards the second connecting post83. Thus, the portion of the resistance connected in series with the first LED string101of the variable resistor80is increased. Accordingly, the first electric current flowing through the first LED string101is decreased, thereby decreasing the light intensity of the first LED string101, while the second electric current flowing through the second LED string102remains unchanged. When the light intensity of the first LED string101is decreased, the color temperature of the LED lamp90is much closer to the second LED string102, such that the color temperature of the LED lamp90is decreased.

In the present disclosure, the LED lamp90includes the variable resistor80connected in series with the first LED string101, and the first and second LED strings101,102connected in parallel to each other, such that when the portion of the resistance which is connected in series with the first LED string101of the variable resistor80is increased (decreased), the first electric current flowing through the first LED string101is decreased (increased). Therefore, a percentage of light of the first LED string101and the second LED string102is changed, thereby changing the color temperature of the LED lamp90. The circuit100is simple and includes minimum of electronic components, which provides lower costs.

Referring toFIG. 3, a circuit200is shown for illustrating the LED lamp90electrically connected to the DC power source60for working, according to a second embodiment. The circuit200differs from the previous circuit100only in that the variable resistor80is connected in series with the second LED string102. More specifically, the first connecting post82of the variable resistor80connects the cathode of the second LED string102, and the slider81of the variable resistor80connects the negative pole of the DC power source60. Thus, when the position of the slider81of the variable resistor80along the resistance track84is changed, the second electric current flowing through the second LED string102is changed accordingly, thereby adjusting the color temperature of the LED lamp90.

Referring toFIG. 4, a circuit300is shown for illustrating the LED lamp90electrically connected to the DC60for working, according to a third embodiment. The circuit300differs from the previous circuit100only in that a switch85is interconnected between the variable resistor80and the LEDs12. One of the connecting posts82,83, i.e., the second connecting post83in this embodiment, of the variable resistor80connects the negative pole of the DC power source60. The slider81is electrically connected with the switch85. The switch85includes a first contact point86connected with the first LED string101and a second contact point88connected with the second LED string102. The switch80can be switched between a first state that the switch80electrically connects the first contact point86and a second state that the switch80electrically connects the second contact point88. Referring back toFIG. 1, the LED lamp90which adopts the circuit300further includes a selector button55connected with the switch85. The selector button55is circular shaped, and rotatablely around a central axis thereof, to control the switch80to work at the first state or the second state.

When the switch80works at the first state, the slider81of the variable resistor80electrically connects the first LED string101via the switch80to form a close circuit between the first LED string101and the DC power source60, while an open circuit is formed between the second LED string102and the DC power source60. At this state, the first LED string101emits light, but the second LED string102is non-luminous. Thus, the color temperature of the light of the LED lamp90is equal to that of the first LED string101. Then, the adjustment button50can be moved downwardly or upwardly along the elongated cutout36to change the position of the slider81of the variable resistor80. Thus, an electric current flowing through the first LED string101is changed accordingly, to adjust the color temperature of the first LED string101(accordingly, the LED lamp90) further. In the contrary, when the switch80works at the second state, the slider81of the variable resistor80electrically connects the second LED string102via the switch80to form a close circuit between the second LED string102and the DC power source60, while an open circuit is formed between the first LED string101and the DC power source60. At this state, the second LED string102emits light, but the first LED string101is non-luminous. Thus, the color temperature of the light of the LED lamp90is equal to that of the second LED string102. Then, the adjustment button50can be moved downwardly or upwardly to change the position of the slider81of the variable resistor80. Thus, an electric current flowing through the second LED string102is changed accordingly, to adjust the color temperature of the second LED string102(and accordingly the LED lamp90) further.

Referring toFIG. 5, a circuit400is shown for illustrating the LED lamp90electrically connected to the AC power source70for working, according to a fourth embodiment. The circuit400differs from the previous circuit100only in that the first and second LED strings101,102are connected in parallel by anti-polar. More specifically, the anode of the first LED string101and the cathode of the second LED string102both connect one pole of the AC power source70directly. The variable resistor80is interconnected between the cathode of the second LED string102and another pole of the AC power source70. The anode of the second LED string102connects the another pole of the AC power source70directly. In this embodiment, the color temperature of the LED lamp90can be changed by changing position of the slider81of the variable resistor80as the same way of the previous circuit100.

Referring toFIG. 6, another circuit500is shown for illustrating the LED lamp90electrically connected to the AC power source70for working, according to a fifth embodiment. The circuit500differs from the previous circuit400only in that the variable resistor80is connected in series with the second LED string102. That is, the variable resistor80is interconnected between the anode of the second LED string102and the another pole of the AC power source70.