Light source driving device

Abstract

The present invention discloses a light source driving device, which includes a first diode, a second diode and a driving chip. The first diode is coupled to a first dimming input terminal, and the second diode is coupled to a second dimming input terminal. The driving chip is coupled to the first diode, the second diode and the light source. The first diode and the second diode have the same specifications and are located in an isothermal environment. The first dimming input terminal and the second dimming input terminal receive a dimming voltage. The driving chip generates two equal fixed currents passing through the first diode and the second diode respectively, and generates a first driving voltage between the first diode and the driving chip with the dimming voltage, and generates a second driving voltage between the driving chip and the second diode. The driving chip restores the dimming voltage according to the first driving voltage and the second driving voltage and drives the light source.

Description

Technical Field

[0001] The present invention relates to a driving device, and in particular to a light source driving device. Background Art

[0002] LED lighting has three main advantages, namely energy saving, environmental protection and green lighting. Because LEDs have high luminous efficiency and low production costs, their application prospects and markets are very broad, making LEDs one of the new generation of light sources that replace traditional light sources in the world today.

[0003] In order to prevent the high voltage from being mistakenly connected to the dimming port of the current LED driver, or to prevent the whole LED driver from being paralyzed due to the damage of one device when the dimming ports of multiple LED drivers are connected in parallel, a diode 10 is connected to the positive input end of the dimming port. Figure 1 As shown. Although this measure is simple and low-cost, it will bring two problems. Due to the voltage drop of diode 10, the actual voltage between the positive and negative input terminals of the dimming port is different from the dimming voltage actually received by the LED driver. The conversion chips in the LED drivers currently on the market cannot automatically eliminate the impact of the voltage drop on diode 10. Some manufacturers do not consider the voltage drop of diode 10 at all, while other manufacturers fixedly subtract 0.5 volts without considering the voltage drop difference on different types of diodes 10. In addition, since the diode is a nonlinear element. When the temperature changes, the voltage drop on the diode also changes, such as Figure 2 As shown in FIG. 1 , the change is in a nonlinear form, which causes the dimming voltage level between the positive and negative input terminals of the dimming port to deviate more seriously than the brightness level output by the light-emitting diode driver. Figure 2 In the graph, four different data correspond to four different forward bias voltages from top to bottom, which are 100, 10, 1 and 0.1 mA respectively.

[0004] Therefore, the present invention is aimed at the above-mentioned problems and proposes a light source driving device to solve the problems arising from the prior art. Summary of the invention

[0005] The object of the present invention is to provide a light source driving device, which can truly restore the actual dimming voltage at different temperatures without changing the manufacturing cost, improve the detection accuracy of the dimming voltage, and improve the negative impact caused by the diode connected in series at the dimming input end.

[0006] To achieve the above-mentioned purpose, the present invention provides a light source driving device, which is coupled to a light source. The light source driving device includes a first diode, a first driving chip, a second diode and a second driving chip. The cathode of the first diode is coupled to the first dimming input terminal, and the first driving chip is coupled to the anode of the first diode and the second dimming input terminal. The first dimming input terminal and the second dimming input terminal are used to receive a dimming voltage. The first driving chip is used to generate a first fixed current passing through the first diode, and the first fixed current and the dimming voltage are used to generate a first driving voltage at a first node between the first diode and the first driving chip. The cathode of the second diode is coupled to the ground terminal, and the anode of the second diode is coupled to a fixed current source. The fixed current source is used to generate a second fixed current passing through the second diode, and the second fixed current is equal to the first fixed current. The first diode and the second diode have the same specifications and are located in an isothermal environment. The second fixed current generates a second driving voltage at a second node between the fixed current source and the second diode. The second driving chip is coupled to the light source, the first node and the second node. The second driving chip is used to receive the first driving voltage and the second driving voltage, and drive the light source accordingly.

[0007] In an embodiment of the present invention, the light source driving device further includes a first filtering circuit coupled between the first node and the second driving chip, and the second driving chip is used to receive the first driving voltage through the first filtering circuit.

[0008] In an embodiment of the present invention, the light source driving device further includes a second filtering circuit coupled between the second node and the second driving chip, and the second driving chip is used to receive the second driving voltage through the second filtering circuit.

[0009] In one embodiment of the present invention, the first diode and the second diode are located on the same printed circuit board.

[0010] In an embodiment of the present invention, the fixed current source includes a fixed voltage source and a resistor. The resistor is coupled between the fixed voltage source and the second node. The fixed voltage source is used to generate a second fixed current passing through the resistor.

[0011] In one embodiment of the present invention, the light source is a light emitting diode.

[0012] In one embodiment of the present invention, a light source driving device is also provided, which is coupled to a light source, and the light source driving device includes a first diode, a second diode and a driving chip. The cathode of the first diode is coupled to the first dimming input terminal, and the cathode of the second diode is coupled to the second dimming input terminal. The first diode and the second diode have the same specifications and are located in an isothermal environment. The first dimming input terminal and the second dimming input terminal are used to receive a dimming voltage. The driving chip is coupled to the anodes of the first diode and the second diode and the light source. The driving chip is used to generate a first fixed current and a second fixed current passing through the first diode and the second diode respectively, and the second fixed current is equal to the first fixed current. The driving chip is used to generate a first driving voltage at a first node between the first diode and the driving chip using the first fixed current and the dimming voltage, and the second fixed current generates a second driving voltage at a second node between the driving chip and the second diode. The driving chip is used to receive the first driving voltage and the second driving voltage, and drive the light source accordingly.

[0013] In an embodiment of the present invention, the light source driving device further includes a filter circuit coupled between the first node and the driving chip, and the driving chip is used to receive the first driving voltage through the filter circuit.

[0014] In one embodiment of the present invention, the first diode and the second diode are located on the same printed circuit board.

[0015] In one embodiment of the present invention, the light source is a light emitting diode.

[0016] Based on the above, the light source driving device places a diode and a diode connected to the dimming input end in an isothermal environment, and designs the first diode and the second diode to have the same specifications. Under the premise that the same current passes through the first diode and the second diode, the forward bias of the second diode is obtained. In this way, the actual dimming voltage can be truly restored at different temperatures without changing the production cost, thereby improving the detection accuracy of the dimming voltage and improving the negative impact caused by the diode in series with the dimming input end. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 FIG. 1 is a schematic diagram of a light emitting diode driver according to the prior art.

[0018] Figure 2 FIG. 4 is a graph showing the junction temperature and forward bias voltage of a light emitting diode in the prior art.

[0019] Figure 3 FIG. 1 is a schematic diagram of a first embodiment of a light source driving device of the present invention.

[0020] Figure 4 FIG. 4 is a schematic diagram of a second embodiment of a light source driving device of the present invention.

[0021] Figure 5 FIG. 4 is a schematic diagram of a light source driving device according to a third embodiment of the present invention.

[0022] Explanation of the reference numerals: 10-diode; 2-light source driving device; 20-first diode; 21-first driving chip; 22-second diode; 23-second driving chip; 24-fixed current source; 240-resistor; 25-first dimming input terminal; 26-second dimming input terminal; 27-first filter circuit; 28-second filter circuit; 3-light source; 4-light source driving device; 40-first diode; 41-second diode; 42-driving chip; 43-first dimming input terminal; 44-second dimming input terminal; 45-filter circuit; 5-light source; N1-first node; N2-second node; VD-dimming voltage; I1-first fixed current; I2-second fixed current; V1-first driving voltage; V2-second driving voltage; VCC, VDD-fixed voltage sources. DETAILED DESCRIPTION

[0023] The embodiments of the present invention will be further explained below in conjunction with the accompanying drawings. As much as possible, the same reference numerals represent the same or similar components in the drawings and the specification. In the drawings, the shapes and thicknesses may be exaggerated for simplicity and convenience. It is understood that the components not specifically shown in the drawings or described in the specification are in the form known to those skilled in the art. Those skilled in the art may make various changes and modifications based on the contents of the present invention.

[0024] When an element is referred to as being "on...", it can generally refer to the element being directly on other elements, or there being other elements between the two. Conversely, when an element is referred to as being "directly on" another element, there cannot be other elements between the two. As used herein, the term "and / or" includes any combination of one or more of the listed associated items.

[0025] The description of "one embodiment" or "an embodiment" in the following text refers to a specific element, structure or feature associated with at least one embodiment. Therefore, multiple descriptions of "one embodiment" or "an embodiment" appearing in multiple places in the following text do not refer to the same embodiment. Furthermore, specific components, structures and features in one or more embodiments may be combined in an appropriate manner.

[0026] The present invention is particularly described by the following examples, which are only used for illustration, because for those skilled in the art, various changes and modifications can be made without departing from the spirit and scope of the present disclosure, so the protection scope of the present disclosure shall be determined by the claims. Throughout the specification and claims, unless the content clearly specifies, the meaning of "a" and "the" includes such a description including "one or at least one" of the elements or components. In addition, as used in the present invention, unless it is obvious from the specific context that the plurality is excluded, the singular article also includes the description of plural elements or components. Moreover, when applied in this description and all claims, unless the content clearly specifies, the meaning of "in which" may include "in which" and "on it". The terms used in the specification and claims, unless otherwise specified, generally have the ordinary meaning of each term used in this field, in the content disclosed herein and in the specific content. Certain terms used to describe the present invention will be discussed below or elsewhere in this specification to provide practitioners with additional guidance in describing the present invention. The use of examples anywhere throughout the specification, including examples of any term discussed herein, is for illustrative purposes only and certainly does not limit the scope and meaning of the present invention or any exemplified term. Likewise, the present invention is not limited to the various embodiments set forth in this specification.

[0027] It is understood that the terms "comprising", "including", "having", "containing", "involving", etc. used herein are open-ended, that is, they mean including but not limited to. In addition, any embodiment or claim of the present invention is not required to achieve all the objects, advantages or features disclosed in the present invention. In addition, the abstract part and the title are only used to assist in searching patent documents and are not used to limit the scope of the present invention.

[0028] Unless otherwise specified, some conditional sentences or words, such as "can", "could", "might", or "may", are generally intended to express that the embodiment of the case has, but can also be interpreted as features, elements, or steps that may not be required. In other embodiments, these features, elements, or steps may not be required.

[0029] The following describes a light source driving device, which places a diode and a diode connected to a dimming input terminal in an isothermal environment, and designs the first diode and the second diode to have the same specifications. Under the premise that the same current passes through the first diode and the second diode, the forward bias of the second diode is obtained. In this way, the actual dimming voltage can be truly restored at different temperatures without changing the manufacturing cost, improving the detection accuracy of the dimming voltage, and improving the negative effects of connecting a diode in series at the dimming input terminal.

[0030] Figure 3 FIG. 1 is a schematic diagram of a first embodiment of a light source driving device of the present invention. Figure 3 , the first embodiment of the light source driving device 2 is introduced below. The light source driving device 2 is coupled to a light source 3. The light source 3 is a light emitting diode as an example, but the present invention is not limited to this. The light source driving device 2 includes a first diode 20, a first driver chip 21, a second diode 22, a second driver chip 23, a fixed current source 24, a first dimming input terminal 25 and a second dimming input terminal 26. The cathode of the first diode 20 is coupled to the first dimming input terminal 25, and the first driver chip 21 is coupled to the fixed voltage source VCC, the anode of the first diode 20 and the second dimming input terminal 25. The cathode of the second diode 22 is coupled to the ground, and the anode of the second diode 22 is coupled to the fixed current source 24. The second driver chip 23 is coupled to the fixed voltage source VDD, the light source 3, a first node N1 between the first diode 20 and the first driver chip 21, and a second node N2 between the fixed current source 24 and the second diode 22. The first diode 20 and the second diode 22 have the same specifications, such as the same size and semiconductor carrier doping concentration, and the first diode 20 and the second diode 22 are located in an isothermal environment. For example, the first diode 20 and the second diode 22 can be located on the same printed circuit board, and the distance between each other is less than 5 cm. In this way, when the temperature changes, the voltage drop across the first diode 20 and the second diode 22 also changes in the same way. In other words, no matter how the temperature changes, the temperature received by the first diode 20 and the second diode 22 is the same. If the current passing through the first diode 20 and the second diode 22 is designed to be the same, this means that the forward bias voltage of the first diode 20 and the second diode 22 is also the same.

[0031] The operation process of the first embodiment of the light source driving device 2 is introduced below. The first dimming input terminal 25 and the second dimming input terminal 26 receive a dimming voltage VD, and the first driving chip 21 generates a first fixed current I1 through the first diode 20, and uses the first fixed current I1 and the dimming voltage VD to generate a first driving voltage V1 at a first node N1 between the first diode 20 and the first driving chip 21. The fixed current source 24 generates a second fixed current I2 through the second diode 22, and the second fixed current I2 is designed to be equal to the first fixed current I1, so that the forward bias voltages of the first diode 20 and the second diode 22 are the same. The second fixed current I2 generates a second driving voltage V2 at a second node N2 between the fixed current source 24 and the second diode 22. The second driving chip 23 receives the first driving voltage V1 and the second driving voltage V2, and drives the light source 3 accordingly. Because the first driving voltage V1 is equal to the forward bias voltage of the first diode 20 plus the dimming voltage VD, and the forward bias voltages of the first diode 20 and the second diode 22 are the same, the second driving chip 23 can truly restore the dimming voltage VD at any temperature by subtracting the second driving voltage V2 from the first driving voltage V1 without changing the manufacturing cost, thereby improving the detection accuracy of the dimming voltage VD and improving the negative impact of the diode connected in series to the dimming input terminal.

[0032] In order to improve the accuracy of the first driving voltage V1 and the second driving voltage V2, in some embodiments of the present invention, the light source driving device 2 may further include a first filtering circuit 27 and a second filtering circuit 28. The first filtering circuit 27 is coupled between the first node N1 and the second driving chip 23, and the second driving chip 23 receives the first driving voltage V1 through the first filtering circuit 27. The second filtering circuit 28 is coupled between the second node N2 and the second driving chip 23, and the second driving chip 23 receives the second driving voltage V2 through the second filtering circuit 28. In addition, in a specific implementation circuit, the fixed current source 24 may include a fixed voltage source VDD and a resistor 240. The resistor 240 is coupled between the fixed voltage source VDD and the second node N2, and the fixed voltage source VDD generates a second fixed current I2 passing through the resistor 240.

[0033] Figure 4 is a schematic diagram of a second embodiment of the light source driving device of the present invention. Figure 4, the second embodiment of the light source driving device 4 is introduced below. The light source driving device 4 is coupled to a light source 5, and the light source 5 is a light emitting diode as an example, but the present invention is not limited to this. The light source driving device 4 includes a first diode 40, a second diode 41, a driving chip 42, a first dimming input terminal 43 and a second dimming input terminal 44, wherein the second dimming input terminal 44 is coupled to the ground terminal. The cathode of the first diode 40 is coupled to the first dimming input terminal 43, and the cathode of the second diode 41 is coupled to the second dimming input terminal 44. The first diode 40 and the second diode 41 have the same specifications, such as having the same size and semiconductor carrier doping concentration, and the first diode 40 and the second diode 41 are located in an isothermal environment. For example, the first diode 40 and the second diode 41 can be located on the same printed circuit board, and the distance between each other is less than 5 cm. In this way, when the temperature changes, the voltage drop on the first diode 40 and the second diode 41 also changes in the same way. That is to say, no matter how the temperature changes, the temperature received by the first diode 40 and the second diode 41 is the same. If the current passing through the first diode 40 and the second diode 41 is designed to be the same, it means that the forward bias voltage of the first diode 40 and the second diode 41 is also the same. The driver chip 42 is coupled to the anodes of the first diode 40 and the second diode 41 and the light source 5.

[0034] The operation process of the second embodiment of the light source driving device 4 is introduced below. The first dimming input terminal 43 and the second dimming input terminal 44 receive a dimming voltage VD, and the driving chip 42 generates a first fixed current I1 and a second fixed current I2 passing through the first diode 40 and the second diode 41 respectively, and the second fixed current I2 is designed to be equal to the first fixed current I1, so that the forward bias voltages of the first diode 40 and the second diode 41 are the same. The driving chip 42 uses the first fixed current I1 and the dimming voltage VD to generate a first driving voltage V1 at a first node N1 between the first diode 40 and the driving chip 42, and the second fixed current I2 generates a second driving voltage V2 at a second node N2 between the driving chip 42 and the second diode 41. The driving chip 42 receives the first driving voltage V1 and the second driving voltage V2, and drives the light source 5 accordingly. Because the first driving voltage V1 is equal to the forward bias voltage of the first diode 40 plus the dimming voltage VD, and the forward bias voltages of the first diode 40 and the second diode 41 are the same, the driving chip 42 can truly restore the dimming voltage VD at any temperature by subtracting the second driving voltage V2 from the first driving voltage V1 without changing the manufacturing cost, thereby improving the detection accuracy of the dimming voltage VD and improving the negative impact of connecting a diode in series at the dimming input end.

[0035] To improve the accuracy of the first driving voltage V1 , in some embodiments of the present invention, the light source driving device 4 may further include a filter circuit 45 coupled between the first node N1 and the driving chip 42 . The driving chip 42 receives the first driving voltage V1 through the filter circuit 45 .

[0036] Figure 5 Schematic diagram of the third embodiment of the light source driving device of the present invention. The difference between the third embodiment and the second embodiment is that the filter circuit 45 of the third embodiment is integrated into the driver chip 42 and coupled to the first node N1 to reduce circuit complexity. The driver chip 42 uses the filter circuit 45 to receive the first driving voltage V1.

[0037] According to the above embodiment, the light source driving device sets the second diode and the first diode connected to the dimming input terminal in an isothermal environment, and designs the first diode and the second diode to have the same specifications. Under the premise that the same current passes through the first diode and the second diode, the forward bias of the second diode is obtained. In this way, the actual dimming voltage can be truly restored at different temperatures without changing the manufacturing cost, thereby improving the detection accuracy of the dimming voltage and improving the negative effects caused by the diode connected in series to the dimming input terminal.

[0038] The above description is only a preferred embodiment of the present invention and is not intended to limit the scope of the present invention. Therefore, all equivalent changes and modifications made according to the shape, structure, characteristics and spirit described in the claims of the present invention should be included in the protection scope of the present invention.

Claims

1. A light source driving device, coupled to a light source, characterized in that: The light source driving device comprises: a first diode, a cathode of which is coupled to the first dimming input terminal; a first driver chip coupled to the anode of the first diode and a second dimming input terminal, wherein the first dimming input terminal and the second dimming input terminal are used to receive a dimming voltage, the first driver chip is used to generate a first fixed current passing through the first diode, and utilize the first fixed current and the dimming voltage to generate a first driving voltage at a first node between the first diode and the first driver chip; a second diode, having a cathode coupled to the ground and an anode coupled to a fixed current source, wherein the fixed current source is used to generate a second fixed current passing through the second diode, the second fixed current being equal to the first fixed current, the first diode and the second diode having the same specifications and being located in an isothermal environment, and the second fixed current generating a second driving voltage at a second node between the fixed current source and the second diode; and A second driving chip is coupled to the light source, the first node, and the second node, wherein the second driving chip is used to receive the first driving voltage and the second driving voltage and drive the light source accordingly.

2. The light source driving device according to claim 1, characterized in that: The device further includes a first filtering circuit coupled between the first node and the second driving chip, and the second driving chip is used for receiving the first driving voltage through the first filtering circuit.

3. The light source driving device according to claim 2, characterized in that: The device further includes a second filtering circuit coupled between the second node and the second driving chip, and the second driving chip is used for receiving the second driving voltage through the second filtering circuit.

4. The light source driving device according to claim 1, characterized in that: The first diode and the second diode are located on a same printed circuit board.

5. The light source driving device according to claim 1, characterized in that: The fixed current source comprises: a fixed voltage source; and A resistor is coupled between the fixed voltage source and the second node, wherein the fixed voltage source is used to generate the second fixed current passing through the resistor.

6. The light source driving device according to claim 1, characterized in that: The light source is a light emitting diode.

7. A light source driving device, coupled to a light source, characterized in that: The light source driving device comprises: a first diode, a cathode of which is coupled to the first dimming input terminal; a second diode, whose cathode is coupled to the second dimming input terminal, wherein the first diode and the second diode have the same specifications and are located in an isothermal environment, and the first dimming input terminal and the second dimming input terminal are used to receive a dimming voltage; and A driver chip is coupled to the anodes of the first diode and the second diode and the light source, wherein the driver chip is used to generate a first fixed current and a second fixed current passing through the first diode and the second diode respectively, the second fixed current is equal to the first fixed current, the driver chip is used to use the first fixed current and the dimming voltage to generate a first driving voltage at a first node between the first diode and the driver chip, the second fixed current generates a second driving voltage at a second node between the driver chip and the second diode, and the driver chip is used to receive the first driving voltage and the second driving voltage and drive the light source accordingly.

8. The light source driving device according to claim 7, characterized in that: The device further comprises a filter circuit coupled between the first node and the driving chip, and the driving chip is used for receiving the first driving voltage through the filter circuit.

9. The light source driving device according to claim 7, characterized in that: The first diode and the second diode are located on a same printed circuit board.

10. The light source driving device according to claim 7, characterized in that: The light source is a light emitting diode.

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