CN101742786A - light emitting device - Google Patents

Abstract

A light-emitting device includes a power supply circuit, a light-emitting circuit and a detection control circuit. The power supply circuit outputs a current. The light-emitting circuit is electrically connected to the power supply circuit and has a plurality of light-emitting units connected in series. Each light-emitting unit has a light-emitting element and a switch element electrically connected to each other. The detection control circuit detects the power, voltage, current, or switch state of the light-emitting circuit and stops supplying current to the light-emitting circuit.

Description

light emitting device

technical field

The invention relates to a light emitting device.

Background technique

In a liquid crystal display device (LCD apparatus), a cold cathode fluorescent lamp is generally used as a light emitting unit of a backlight module. However, because CCFLs are not as good as light-emitting diodes (LEDs) in terms of color performance, there are currently industry players using light-emitting diodes as light-emitting devices under the premise that the technology of light-emitting diodes is gradually maturing.

Referring to FIG. 1 , a conventional light emitting device 1 has a power supply circuit 11 and a plurality of LEDs 12 , which provide power to each LED 12 through the power supply circuit 11 to make each LED 12 emit light.

However, in the prior art, no other detection circuits are used to detect the states of the light emitting diodes 12 . Therefore, when any LED 12 is damaged to form an open circuit O, there is no other control circuit to shut down the power supply circuit 11 to stop supplying power to the damaged LED 12 . In addition, if the light emitting diode 12 has reached the maximum brightness, the power supply circuit 11 cannot adjust the power supply to the light emitting diode 12 correspondingly, and these situations will cause loss and waste of electric energy.

Therefore, how to more effectively control the power supply of the light emitting device and reduce the loss and waste of electric energy is one of the current important issues.

Contents of the invention

In view of the above problems, the object of the present invention is to provide a light emitting device capable of more effectively controlling the power supply of the light emitting circuit to reduce power consumption and waste.

To achieve the above purpose, a lighting device according to the present invention includes a power supply circuit, a lighting circuit and a detection control circuit. The power supply circuit outputs a current. The light emitting circuit is electrically connected to the power supply circuit, and has a plurality of light emitting units connected in series. Each light emitting unit has a light emitting element and a switching element electrically connected to each other. The detection control circuit detects the power, or voltage, or current, or switch state of the lighting circuit, and stops supplying current to the lighting circuit.

As mentioned above, the light emitting device according to the present invention first detects the power, voltage, current, or switch state of the light emitting circuit through the detection control circuit, and then stops supplying current to the light emitting circuit. Therefore, the light emitting device of the present invention can control the supply of current of the light emitting circuit correspondingly according to the state of the light emitting circuit, thereby reducing unnecessary power loss and waste.

Description of drawings

FIG. 1 is a schematic diagram of a known light-emitting device;

FIG. 2 is a schematic diagram of a light-emitting device of the present invention; and

3 and 4 are schematic diagrams of different variations of the light emitting device of the present invention.

Description of component symbols:

1, 2, 2a, 2b: light emitting device

11.3: Power supply circuit

12: LED

4: Lighting circuit

41: Lighting unit

411: Light emitting element

412: switching element

5, 5a, 5b: detection control circuit

51: Brightness control unit

511: Comparing components

512: Charge storage element

513: sensing element

52: Detection unit

53: Power control unit

6: Bypass switch circuit

F: Feedback signal

I: Current

O: open circuit

Detailed ways

A light emitting device according to the present invention will be described below with reference to related drawings, wherein the same elements are denoted by the same symbols.

Please refer to FIG. 2 , the light emitting device 2 of the present invention includes a power supply circuit 3 , a light emitting circuit 4 and a detection control circuit 5 .

The power supply circuit 3 outputs a current I, and the current I can be direct current (DC) or alternating current (AC). The light emitting circuit 4 is electrically connected to the power supply circuit 3 and has a plurality of light emitting units 41 connected in series. Each light emitting unit 41 has a light emitting element 411 and a switching element 412 electrically connected to each other. Wherein, in this embodiment, the light emitting unit 41 has a plurality of light emitting elements 411 and the switching element 412 is connected in parallel with these light emitting elements 411 as an example for illustration, but it is not limiting.

The light emitting element 411 can be, for example, a light emitting diode or a CCFL. In this embodiment, the light emitting element 411 is illustrated by taking a light emitting diode as an example, but it is not limiting. The switching element 412 is, for example, a bipolar transistor (BJT) or a metal-oxide-semiconductor field effect transistor (MOSFET). In this embodiment, the switching element 412 is described as a MOSFET.

The detection control circuit 5 detects the power, or voltage, or current, or switch state of the light emitting circuit 4 . Wherein, the power is, for example, the electric power or luminous power of the light emitting circuit 4 , the voltage or current is the terminal voltage or current of the light emitting circuit 4 , and the switching state is the switching state of the switching elements 412 .

Therefore, when the detection control circuit 5 detects that the power, voltage, or current of the lighting circuit 4 is less than or equal to a threshold, the detection control circuit 5 can make the power supply circuit 3 stop supplying the current I to the lighting circuit 4 .

In addition, if the detection control circuit 5 detects the switch state of the light-emitting circuit 4, when at least one switch element 412 is in a turn off state, it means that at least one light-emitting element 411 is in a turn-on state, and the light-emitting circuit 4 is turned on. state, at this time, the detection control circuit 5 will make the power supply circuit 3 continue to supply the current I to the light emitting circuit 4 . However, when all the switching elements 412 are turned on, which means that all the light emitting elements 411 are turned off, the light emitting circuit 4 is turned off, and the detection control circuit 5 will turn off the power supply circuit 3 to stop supplying the current I to the light emitting circuit 4.

Therefore, the light emitting device 2 of this embodiment can control the current input of the light emitting circuit 4 correspondingly according to the state of the light emitting circuit 4 , thereby reducing unnecessary power loss and waste.

In addition, please refer to FIG. 3 , which is a schematic diagram of another variation of the light emitting device 2a of this embodiment. The detection control circuit 5 a of the light emitting device 2 a may further include a brightness control unit 51 electrically connected to at least one of the light emitting units 41 .

The brightness control unit 51 may have a comparison element 511 , a charge storage element 512 and a sensing element 513 , and the three are electrically connected. The comparison element 511 can be, for example, a voltage comparator or a current comparator, the charge storage element 512 can be, for example, a capacitor, and the sensing element 513 can be, for example, a photodiode or a photoresistor. Here, the comparing element 511 is illustrated as a voltage comparator, and the sensing element 513 is illustrated as a photodiode. It should be noted that the design method of the brightness control unit 51 is not restrictive, and there may be different design methods according to different requirements.

Therefore, the brightness control unit 51 consumes or adjusts the amount of charge stored in the charge storage element 512 by utilizing the characteristic that the sensing element 513 will generate a leakage current after receiving the light from the light-emitting element 411 that is turned on, and After the charge is consumed, the switch element 412 of the light emitting unit 41 is turned on, so that the light emitting element 411 is turned off. Thus, the brightness control unit 51 can control the switch element 412 according to the brightness of the light-emitting element 411 of the light-emitting unit 41, and determine the light-emitting time of the light-emitting unit 41 according to the amount of charge stored in the charge storage element 512, so as to control the brightness of the light-emitting unit 41 .

Please refer to FIG. 4 , which is a schematic diagram of another variation of the light emitting device 2 b of this embodiment. The lighting device 2 b may further include a bypass switch circuit 6 .

The bypass switch circuit 6 may include, for example, a BJT or a MOSFET, and in this embodiment, a MOSFET is used for illustration. The bypass switch circuit 6 is electrically connected to the light emitting circuit 4 and connected in parallel with at least one of the light emitting units 41 . In this embodiment, the bypass switch circuit 6 is connected in parallel with a plurality of light emitting units 41 for illustration, but this is not limiting.

Therefore, when the detection control circuit 5b detects that the power, voltage, or current of the light emitting circuit 4 is less than or equal to a threshold, the detection control circuit 5b can control the bypass switch circuit 6 to bypass the conduction current I or turn off the power supply circuit 3, To stop supplying the current I to the lighting circuit 4 . In addition, if the detection control circuit 5b detects the switching state of the light emitting circuit 4, similarly, when the light emitting elements 411 of the light emitting circuit 4 are in the off state, the detection control circuit 5b can control the bypass switch circuit 6 to bypass the conduction current I Or turn off the power supply circuit 3 to stop supplying the current I to the lighting circuit 4 .

It is worth mentioning that, regardless of whether the bypass switch circuit 6 includes a three-terminal switch element or a four-terminal switch element, the terminal voltage across the light-emitting circuit 4 when it is turned on is smaller than the terminal voltage when the light-emitting circuit 4 is turned on.

In addition, the detection control circuit 5 b may further include a detection unit 52 and a power control unit 53 .

The detecting unit 52 may include logic gates, or comparators, or resistors, or capacitors, or light sensors, for example, which detect the power, voltage, current, or switch state of the lighting circuit 4 to generate at least one feedback signal F. Wherein, the power is, for example, the electric power or luminous power of the light emitting circuit 4 , the voltage or current is the terminal voltage or current of the light emitting circuit 4 , and the switching state is the switching state of the switching elements 412 . The feedback signal F can be, for example, a digital signal or an analog signal.

The power control unit 53 may have a logic gate or a comparator, for example, where the logic gate is, for example, an OR (OR) gate or an AND (AND) gate.

Therefore, when the feedback signal F is an analog signal, the power control unit 53 may have a logic gate, and the power control unit 53 will compare the feedback signal F with a threshold. When the feedback signal F is less than or equal to the threshold, the power control unit 53 can control the bypass switch circuit 6 to bypass the conduction current I, or turn off the power supply circuit 3 to stop supplying the current I to the light emitting circuit 4 .

In addition, when the detection unit 52 is to output a plurality of digital feedback signals F (for example, the detection unit 52 is to detect the switching state of the switch element 412 ), the power control unit 53 may have logic gates. The power control unit 53 can perform an OR (OR) operation or an AND (AND) operation on these feedback signals F. According to the calculation result, if the light-emitting elements 411 of the light-emitting circuit 4 are in the off state, the power control unit 53 can control the bypass switch circuit 6 to bypass the conduction current I, or turn off the power supply circuit 3 to stop supplying the current I to emit light. Circuit 4.

To sum up, the light emitting device according to the present invention first detects the power, voltage, current, or switch state of the light emitting circuit through the detection control circuit, and then stops supplying current to the light emitting circuit. Therefore, the light emitting device of the present invention can control the power supply of the light emitting circuit correspondingly according to the state of the light emitting circuit, thereby reducing unnecessary power loss and waste. In addition, the lighting device can also include a bypass switch circuit, so that the detection control circuit can not only turn off the power supply circuit, but also control the bypass switch circuit to bypass the conduction current, so as to stop supplying current to the lighting circuit.

In addition, the detection control circuit may further include a detection unit and a power control unit. The detection unit can generate a digital or analog feedback signal, and the power control unit can stop the power supply circuit from supplying current to the light emitting circuit according to the feedback signal.

The above description is for illustration only, not for limitation. Any equivalent modifications or changes made without departing from the spirit and scope of the present invention shall be included in the scope of the appended claims.

Claims (13)

1. A lighting device, comprising: a power supply circuit, which outputs a current; A light emitting circuit, which is electrically connected to the power supply circuit, and has a plurality of light emitting units connected in series, and each light emitting unit has a light emitting element and a switching element electrically connected to each other; and A detection control circuit, which detects the power, or voltage, or current, or switch state of the lighting circuit, and stops supplying the current to the lighting circuit. 2. The light emitting device according to claim 1, wherein the light emitting element is connected in parallel with the switching element. 3. The lighting device according to claim 1, wherein the detection control circuit comprises: A brightness control unit is electrically connected to at least one of the light emitting units, and the brightness control unit controls the switch element according to the light emitting brightness of the light emitting element of the light emitting unit. 4. The light emitting device as claimed in claim 3, wherein the brightness control unit has a comparison element, a charge storage element and a sensing element, and the three are electrically connected. 5. The light emitting device as claimed in claim 1, wherein when the light emitting elements are all off, the detection control circuit turns off the power supply circuit. 6. The light emitting device of claim 1, further comprising: A bypass switch circuit is electrically connected with the lighting circuit. 7. The light emitting device according to claim 6, wherein the terminal voltage when the bypass switch circuit is turned on is smaller than the terminal voltage when the light emitting circuit is turned on. 8. The light emitting device as claimed in claim 6, wherein when the light emitting elements are all off, the detection control circuit bypasses the bypass switch circuit. 9. The lighting device as claimed in claim 6, wherein the detection control circuit detects the power, voltage, current, or switch state of the lighting circuit to control the bypass switch circuit or shut down the power supply circuit. 10. The lighting device according to claim 1, wherein the detection control circuit comprises: A detection unit, which detects the power, or voltage, or current, or switch state of the lighting circuit to generate at least one feedback signal; and A power control unit receives the feedback signal and stops supplying the current to the lighting circuit. 11. The light-emitting device according to claim 10, wherein the detection unit outputs a plurality of feedback signals, and the power control unit has a logic gate, which performs calculation on these feedback signals, and the power control unit stops according to the calculation result. The current is supplied to the lighting circuit. 12. The lighting device as claimed in claim 10, wherein the power control unit has a comparator for comparing the feedback signal with a threshold. 13. The lighting device according to claim 12, wherein when the feedback signal is less than or equal to the threshold, the power control unit stops supplying the current to the lighting circuit.

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