KR20110023870A - Lighting system - Google Patents

Abstract

PURPOSE: A light emitting system is provided to supply a uniform current and a uniform voltage to a light emitting diode through a voltage regulator and a constant current unit, thereby making a light emitting diode stably emit light without a brightness change. CONSTITUTION: A power supply unit(PW) provides an AC voltage. A rectifying unit(100) generates an output voltage by rectifying the AC voltage. A voltage regulator(200) converts the output voltage into an operation voltage with a uniform voltage value. A constant current unit(300) generates a light emitting current with a uniform current value by the operation voltage. A light emitting diode(400) generates light by receiving the light emitting current from the constant current unit.

Description

Lighting system {LIGHTING SYSTEM}

The present invention relates to a light emitting system, and more particularly to a light emitting system having a light emitting diode for generating light.

Light emitting diodes (LEDs) are light emitting devices capable of generating high luminance light at low power, and have recently been widely used as light sources of light emitting devices. The light emitting diode generally generates light only when a direct current voltage is applied in the forward direction. Therefore, when the external power source is an AC power source providing an AC voltage, it is necessary to change the AC voltage to a DC voltage that can be used in the light emitting diode. That is, to drive the light emitting diode, there is a need for an AC-DC converter capable of converting AC into direct current and outputting the same.

The AC-DC converter has an advantage of supplying a stable DC voltage and DC current to the light emitting diode, but the lifetime reliability (typically 10,000-15,000 hr) of components such as a capacitor used in the AC-DC converter is emitted. The problem of not following the diode's lifetime reliability (about 30,000 hr or more) can occur. In addition, the AC-DC converter has not only a considerable volume but also a high price, which can be a big obstacle in applying the LED to a real product.

Accordingly, the present invention is to solve such a conventional problem, the problem to be solved by the present invention is to provide a light emitting system that can emit a light emitting diode by generating a stable power at low cost.

The light emitting system according to the exemplary embodiment of the present invention includes a power supply unit, a rectifying unit, a constant voltage unit, a constant current unit, and a light emitting device unit.

The power supply unit provides an AC voltage. The rectifier receives the AC voltage from the power supply, rectifies the AC voltage to generate an output voltage. The constant voltage unit receives the output voltage from the rectifier and changes the output voltage to a driving voltage having a constant voltage value. The constant current unit receives the driving voltage from the constant voltage unit, and generates a light emitting current having a constant current value by the driving voltage. The light emitting device unit includes at least one light emitting diode to generate light by receiving the light emitting current from the constant current unit.

The constant voltage unit may include a transistor, a bias resistor electrically connected between the collector terminal and the base terminal of the transistor, and a zener diode electrically connected to the base terminal of the transistor. In this case, the cathode terminal of the zener diode is electrically connected to the base terminal of the transistor, and the output voltage is applied between the collector terminal of the transistor and the anode terminal of the zener diode. In addition, the driving voltage is formed between the emitter terminal of the transistor and the anode terminal of the zener diode by the output voltage.

One end of the constant current unit may be electrically connected to an emitter terminal of the transistor, and the other end of the constant current unit may be electrically connected to an anode terminal of the light emitting device unit, and a cathode terminal of the light emitting device unit may be connected to an anode terminal of the zener diode. Can be electrically connected.

The constant current unit may include a constant current device capable of generating the light emitting current having a constant current value if the driving voltage applied from the constant voltage unit has a voltage value within a reference range. In this case, the constant current device may be a junction field effect transistor, the collector terminal of the junction field transistor is electrically connected to the emitter terminal of the transistor, the emitter terminal of the junction field transistor Is electrically connected to the base terminal of the junction field transistor.

The transistor may be any one of a bipolar junction transistor and a metal oxide semiconductor field effect transistor (MOSFET). The rectifying unit may include a bridge circuit.

A light emitting system according to another embodiment of the present invention includes a light emitting device unit having at least one light emitting diode for generating light, a power supply unit for providing an AC voltage, and receiving the AC voltage from the power supply unit to rectify the AC voltage. And a rectifier for generating an output voltage, and a constant voltage part configured to receive the output voltage from the rectifier, change the output voltage to a drive voltage having a constant voltage value, and provide the drive voltage to the light emitting device. The constant voltage unit includes a transistor, a bias resistor electrically connected between a collector terminal and a base terminal of the transistor, and a zener diode electrically connected to the base terminal of the transistor. In this case, a cathode terminal of the zener diode is electrically connected to the base terminal of the transistor, and the output voltage is applied between the collector terminal of the transistor and the anode terminal of the zener diode, and the driving voltage Is formed between the emitter terminal of the transistor and the anode terminal of the zener diode by the output voltage, and is provided to the light emitting element portion.

The light emitting system may further include a constant current unit configured to receive the driving voltage from the constant voltage unit, generate a light emitting current having a constant current value by the drive voltage, and provide light to the light emitting element unit to generate light. have.

According to the light emitting system of the present invention, by providing a constant current and voltage to the light emitting diode through the constant voltage unit and the constant current unit having a relatively low cost and high reliability, the light emitting diode can emit light stably without changing the brightness.

1 is a block diagram showing a light emitting system according to a first embodiment of the present invention.
FIG. 2 is a circuit diagram illustrating the light emitting system of FIG. 1 in detail.
3 is a waveform diagram illustrating an AC voltage and an output voltage of FIG. 2.
4 is a waveform diagram illustrating an output voltage and a driving voltage of FIG. 2.
FIG. 5 is a graph for describing voltage and current characteristics of the constant current device of FIG. 2.
6 is a waveform diagram illustrating a light emitting current output from the constant current device of FIG. 2.
7 is a circuit diagram for describing in detail the light emitting system according to the second embodiment of the present invention.
FIG. 8 is a waveform diagram illustrating the AC voltage and the secondary AC voltage of FIG. 7.
FIG. 9 is a waveform diagram illustrating the secondary AC voltage and the pulse current voltage of FIG. 7.
FIG. 10 is a waveform diagram illustrating the pulse voltage and the output voltage of FIG. 7.
FIG. 11 is a waveform diagram illustrating an output voltage and a driving voltage of FIG. 7.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the drawings.

As the inventive concept allows for various changes and numerous embodiments, particular embodiments will be illustrated in the drawings and described in detail in the text. However, this is not intended to limit the present invention to the specific disclosed form, it should be understood to include all modifications, equivalents, and substitutes included in the spirit and scope of the present invention.

Like reference numerals are used for like elements in describing each drawing. In the accompanying drawings, the dimensions of the structures are shown in an enlarged scale than actual for clarity of the invention.

The terms first, second, etc. may be used to describe various components, but the components should not be limited by the terms. The terms are used only for the purpose of distinguishing one component from another. For example, without departing from the scope of the present invention, the first component may be referred to as the second component, and similarly, the second component may also be referred to as the first component. Singular expressions include plural expressions unless the context clearly indicates otherwise.

In this application, the terms "comprise" or "have" are intended to indicate that there is a feature, number, step, action, component, part, or combination thereof described on the specification, and one or more other features. It is to be understood that the present invention does not exclude the possibility of the presence or the addition of numbers, steps, operations, components, parts, or combinations thereof.

Also, unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art. Terms such as those defined in the commonly used dictionaries should be construed as having meanings consistent with the meanings in the context of the related art and shall not be construed in ideal or excessively formal meanings unless expressly defined in this application. Do not.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

<Example 1 of the light emitting system>

FIG. 1 is a block diagram illustrating a light emitting system according to a first embodiment of the present invention, and FIG. 2 is a circuit diagram for explaining the light emitting system of FIG. 1 in detail.

1 and 2, the light emitting system according to the present exemplary embodiment includes a power supply unit PW, a rectifying unit 100, a constant voltage unit 200, a constant current unit 300, and a light emitting device unit 400.

The power supply unit PW provides an AC voltage V1. For example, the AC voltage V1 may be an AC voltage of 60Hz 220V or an AC voltage of 60Hz 120V. The rectifier 100 receives the AC voltage V1 from the power supply PW, rectifies the AC voltage V1 to generate an output voltage V2. That is, the rectifier 100 includes a rectifier circuit 110 that can change the AC voltage V1 to the output voltage V2.

3 is a waveform diagram illustrating an AC voltage and an output voltage of FIG. 2.

2 and 3, the rectifier circuit 110 may invert the negative voltage of the AC voltage V1 applied from the power supply unit PW to a positive voltage. For example, the rectifier circuit 110 is preferably a bridge circuit composed of four rectifier diodes.

4 is a waveform diagram illustrating an output voltage and a driving voltage of FIG. 2.

2 and 4, the constant voltage unit 200 receives the output voltage V2 from the rectifier 100 and changes the output voltage V2 into a driving voltage V3 having a constant voltage value. Let's do it. For example, the constant voltage unit 200 may form the driving voltage V3 by clipping a portion of the output voltage V2 that vibrates in the form of a wave.

The constant voltage unit 200 may include, for example, a transistor BT, a bias resistor RS, and a zener diode DZ. The bias resistor RS is electrically connected between a collector terminal and a base terminal of the transistor BT. The cathode terminal of the zener diode DZ is electrically connected to the base terminal of the transistor BT. In the present embodiment, the transistor BT is preferably a bipolar transistor as shown in FIG. 2, but may alternatively be a metal oxide semiconductor field effect transistor (MOSFET). In addition, the transistor BT is preferably an NPN type transistor as shown in FIG. 2, but may also be a PNP type transistor.

First and second output terminals of the rectifier circuit 110 are electrically connected to the collector terminal of the transistor BT and the anode terminal of the zener diode DZ, respectively, and thus the output voltage V2. Is applied between the collector terminal of the transistor BT and the anode terminal of the zener diode DZ. In this case, the driving voltage V3 may be formed between the emitter terminal of the transistor BT and the anode terminal of the zener diode DZ by the output voltage V2.

Specifically, the process of forming the driving voltage V3 will be described briefly. First, when the rectified output current Iin by the output voltage V2 is applied to the constant voltage unit 200, the rectified output current Iin is applied to the collector terminal of the transistor BT. And an bias current IS flowing through the IC and the bias resistor RS. The bias current IS is divided into a base current IB applied to the base terminal of the transistor BT and a zener current IZ flowing through the zener diode DZ. In addition, the emitter current IE output from the emitter terminal of the transistor BT is formed by the sum of the collector current IC and the base current IB. In this case, the collector current IC is a current that is amplified proportionally by the base current IB, and is similar to the emitter current IE because the base current IB has a relatively small magnitude.

The zener current IZ is a current flowing in the reverse direction of the zener diode DZ after overcoming the breakdown voltage of the zener diode DZ. At this time, the zener voltage (VZ) formed at both ends of the zener diode (DZ) does not have a voltage value greater than the breakdown voltage of the zener diode (DZ) due to the characteristics of the zener diode (DZ), the zener current (IZ) Regardless of the magnitude, the breakdown voltage of the zener diode DZ is almost maintained. On the other hand, since the PN junction diode is formed between the base terminal and the emitter terminal of the transistor BT, a voltage drop of about 0.7 V is applied by the base-emitter voltage VBE. Therefore, the driving voltage V3 formed between the emitter terminal of the transistor BT and the anode terminal of the zener diode DZ is equal to the base-emitter voltage as shown in FIG. 4 in the zener voltage VZ. It will have a value less than or equal to the size of VBE).

FIG. 5 is a graph illustrating voltage and current characteristics of the constant current device of FIG. 2, and FIG. 6 is a waveform diagram illustrating a light emitting current output from the constant current device of FIG. 2.

2, 5, and 6, the constant current unit 300 receives the driving voltage V3 from the constant voltage unit 200, and emits light having a constant current value by the driving voltage V3. Generate (ID). Thereafter, the light emitting device unit 400 receives the light emitting current ID from the constant current unit 300 to generate light. Here, the light emitting device unit 400 may include a plurality of light emitting diodes connected in series, in parallel or in parallel.

Specifically, one end of the constant current unit 300 is electrically connected to the emitter terminal of the transistor BT, and the other end of the constant current unit 300 is electrically connected to the anode terminal of the light emitting device unit 400. The cathode terminal of the light emitting device unit 400 may be electrically connected to the anode terminal of the zener diode DZ.

The constant current unit 300 may generate a constant current device JT capable of generating the light emitting current ID having a constant current value when the driving voltage V3 applied from the constant voltage unit 200 changes within a reference range. It may include. In this case, the constant current device is preferably a junction field effect transistor (junction field effect transistor), as shown in Figure 2, the collector terminal of the junction field transistor is electrically connected to the emitter terminal of the transistor (BT), The emitter terminal of the junction field transistor is electrically connected to the base terminal of the junction field transistor.

The driving voltage V3 output from the constant voltage unit 200 is applied between the collector terminal of the junction type transistor and the cathode terminal of the light emitting device unit 400. In this case, the driving voltage V3 is distributed and applied to the junction field transistor and the light emitting device unit 400, respectively. That is, the driving voltage V3 is equal to the sum of the transistor operating voltages formed at both ends of the constant current device JT and the light emission voltages formed at both ends of the light emitting device unit 400.

On the other hand, the voltage-current characteristics of the junction type transistor may be divided into three regions, an ohmic region, a saturation region, and a breakdown region. The ohmic region refers to a region in which a current flowing through the junction type transistor (hereinafter referred to as a transistor through current) increases when the transistor operating voltage increases, and the saturation region refers to a transistor through current even though the transistor operating voltage increases. Is a region in which is no longer increased and remains substantially constant as the saturation current IA, and the breakdown region is a region in which the transistor operating current increases excessively and the transistor passing current rapidly increases again. Here, the junction type transistor has the characteristic of the ohmic region until the first operating voltage VA1, and has the characteristic of the saturation region between the first operating voltage VA1 and the second operating voltage VA2. After the second operating voltage VA2, the breakdown region has a characteristic. That is, when the transistor operating voltage is formed between the first operating voltage VA1 and the second operating voltage VA2, the junction field transistor has the transistor passing current substantially constant as the saturation current IA. Has a constant current characteristic that is maintained.

The light emitting voltage may be changed according to the number of light emitting diodes in the light emitting device unit 400. For example, when a voltage drop of about 0.7V occurs in one light emitting diode, when the number of the light emitting diodes is connected in series, the light emitting voltage may be about 14V. In addition, the light emitting voltage may be changed according to heat generated from the light emitting diode. For example, when the temperature is increased in the light emitting diode, the voltage drop value generated in the single light emitting diode is reduced, and as a result, the light emitting voltage may be reduced.

As described above, when the light emission voltage fluctuates for various reasons including the above case, since the sum of the light emission voltage and the transistor operating voltage is constant as the driving voltage V3, the transistor operation voltage is It changes in the direction opposite to the fluctuation direction of the light emission voltage. However, as long as the transistor operating voltage only varies within the first operating voltage VA1 and the second operating voltage VA2, the light emitting current ID applied to the light emitting element unit 400, that is, The transistor pass current may be maintained at the saturation current IA. Here, the light emission current ID is the same current as the emitter current IE output from the emitter terminal of the transistor BJ.

In addition, even if the driving voltage V3 itself changes or a ripple occurs due to a problem in the power supply unit PW, a problem in the rectifying unit 100, or a problem in the constant voltage unit 200. As long as a transistor operating voltage is formed between the first operating voltage VA1 and the second operating voltage VA2, the light emitting current ID applied to the light emitting device unit 400 is the saturation current IA. Can be kept constant.

<Example 2 of the light emitting system>

7 is a circuit diagram illustrating a light emitting system according to a second exemplary embodiment of the present invention in detail. FIG. 8 is a waveform diagram illustrating an AC voltage and a secondary AC voltage of FIG. 7, and FIG. 9 is a secondary AC of FIG. 7. FIG. 10 is a waveform diagram illustrating the voltage and the pulse voltage, and FIG. 10 is a waveform diagram illustrating the pulse voltage and the output voltage of FIG. 7, and FIG. 11 is a waveform diagram illustrating the output voltage and the driving voltage of FIG.

Since the light emitting system according to the present exemplary embodiment is substantially the same as the light emitting system of the first embodiment described with reference to FIGS. 1 to 6 except for the rectifying unit 100, a detailed description of other components except for the rectifying unit 100 is described. Will be omitted.

Referring to FIG. 7, the rectifying unit 100 receives the AC voltage V1 from the power supply unit PW, and rectifies the AC voltage V1 to generate an output voltage V2. The rectifier 100 may include a transformer 120, a rectifier circuit 110, and a smoothing circuit 130.

7 and 8, the transformer 120 receives the AC voltage V1 from the power supply unit PW, and transforms the AC voltage V1 to generate a secondary AC voltage V4. The secondary AC voltage V4 may be formed by dropping from the AC voltage V1 and have an appropriate size to drive the light emitting diode of the light emitting device unit 400.

7 and 9, the rectifier circuit 110 receives the secondary AC voltage V4 from the transformer 120 and rectifies the secondary AC voltage V4 to generate a pulse voltage V5. Let's do it. The pulsating voltage V5 is a voltage formed by inverting the negative voltage of the secondary AC voltage V4 into the positive voltage, and both have only the positive voltage. For example, the rectifier circuit 110 is preferably a bridge circuit composed of four rectifier diodes.

7 and 10, the smoothing circuit 130 receives the pulse current voltage V5 from the rectifier circuit 110 and reduces the pulse flow rate, that is, the magnitude of vibration of the pulse voltage V5. The output voltage V2 is generated. For example, the smoothing circuit 130 may reduce the pulse rate of the pulse voltage V5 by charging the electric charge applied from the rectifier circuit 110 to maintain the peak voltage of the pulse voltage V5. It may include a rectifying capacitor.

7 and 11, the constant voltage unit 200 receives the output voltage V2 from the smoothing circuit 130 and converts the output voltage V2 into a driving voltage V3 having a constant voltage value. Change it. For example, the constant voltage unit 200 may form the driving voltage V3 by clipping a portion of the output voltage V2 that vibrates in the form of a wave. At this time, since the output voltage (V2) is a voltage from which the pulse flow is removed, the driving voltage (V3) may have a voltage value that is kept constant, unlike FIG. It may have a current value that is kept constant.

According to the light emitting system of the present invention, a constant current and voltage are supplied to the light emitting diodes by using a relatively low cost, high reliability, and simple constant voltage part and constant current part, without using expensive and bulky components as in the conventional AC-DC converter. By providing the light emitting diodes, the light emitting diodes can be stably emitted without changing the brightness.

In the detailed description of the present invention described above with reference to the preferred embodiments of the present invention, those skilled in the art or those skilled in the art having ordinary skill in the art will be described in the claims to be described later It will be understood that various modifications and variations can be made in the present invention without departing from the scope of the present invention.

PW: power supply section 100: rectification section
110: rectifier circuit 120: transformer
130: smoothing circuit 200: constant voltage portion
BT: Transistor RS: Bias Resistor
DZ: Zener Diode 300: Constant Current Section
JT: constant current device 400: light emitting diode
V1: AC voltage V2: Output voltage
V3: drive voltage V4: secondary AC voltage
V5: Pulse voltage VZ: Zener voltage
VBE: Base-Emitter Voltage Iin: Rectified Output Current
IC: collector current IE: emitter current
IB: Base Current IS: Bias Current
IZ: Zener Current ID: Luminous Current

Claims (10)

A power supply unit providing an AC voltage;
A rectifying unit receiving the AC voltage from the power supply unit, rectifying the AC voltage to generate an output voltage;
A constant voltage unit receiving the output voltage from the rectifier and changing the output voltage to a driving voltage having a constant voltage value;
A constant current unit configured to receive the driving voltage from the constant voltage unit and generate a light emitting current having a constant current value by the drive voltage; And
And a light emitting device unit including at least one light emitting diode to generate light by receiving the light emitting current from the constant current unit. The method of claim 1, wherein the constant voltage unit
A transistor, a bias resistor electrically connected between a collector terminal and a base terminal of the transistor, and a zener diode electrically connected to the base terminal of the transistor,
The cathode terminal of the zener diode is electrically connected to the base terminal of the transistor, the output voltage is applied between the collector terminal of the transistor and the anode terminal of the zener diode,
And the driving voltage is formed between the emitter terminal of the transistor and the anode terminal of the zener diode by the output voltage. The method of claim 2, wherein the one end of the constant current portion is electrically connected to the emitter terminal of the transistor,
The other end of the constant current portion is electrically connected to the anode terminal of the light emitting element portion,
And a cathode terminal of the light emitting element portion is electrically connected to an anode terminal of the zener diode. The method of claim 3, wherein the constant current unit
And a constant current element capable of generating the light emitting current having a constant current value if the driving voltage applied from the constant voltage portion has a voltage value within a reference range. The method of claim 4, wherein the constant current device is a junction field effect transistor,
The collector terminal of the junction field transistor is electrically connected to the emitter terminal of the transistor, and the emitter terminal of the junction field transistor is electrically connected to the base terminal of the junction field transistor. . The method of claim 2, wherein the transistor
A light emitting system, characterized in that one of a bipolar transistor (transistor) and a metal oxide semiconductor field-effect transistor (MOSFET). The light emitting system of claim 1, wherein the rectifier comprises a bridge circuit. A light emitting system comprising a light emitting element portion having at least one light emitting diode for generating light, the light emitting system comprising:
A power supply unit providing an AC voltage;
A rectifying unit receiving the AC voltage from the power supply unit, rectifying the AC voltage to generate an output voltage; And
A constant voltage unit configured to receive the output voltage from the rectifying unit, change the output voltage to a driving voltage having a constant voltage value, and provide the driving voltage to the light emitting device unit for driving;
The constant voltage unit includes a transistor, a bias resistor electrically connected between a collector terminal and a base terminal of the transistor, and a zener diode electrically connected to the base terminal of the transistor. The method of claim 8, wherein the cathode terminal of the zener diode is electrically connected to the base terminal of the transistor, and the output voltage is applied between the collector terminal of the transistor and the anode terminal of the zener diode. ,
And the driving voltage is formed between the emitter terminal of the transistor and the anode terminal of the zener diode by the output voltage, and is provided to the light emitting element unit. 10. The device of claim 8, further comprising a constant current unit configured to receive the driving voltage from the constant voltage unit, generate a light emitting current having a constant current value by the drive voltage, and provide light to the light emitting element unit to generate light. Light emitting system characterized in that.

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