KR101459505B1 - Led lighting system - Google Patents

Abstract

Disclosed is s a light emitting diode illumination device. The light emitting diode illumination device includes: a power supply circuit providing an input voltage with a ripple; an LED array which forms channels including light-emitting diodes and emits light in response to the input voltage; a constant current control circuit providing a current path for the LED array; a current sensing resistor which provides a sensing voltage in response to the current flowing through the current path; and a voltage sensing circuit which provides comparison voltages in a number corresponding to the channels for the constant current control circuit and adjusts the level of the comparison voltages in response to the change in the sensing voltage.

Description

TECHNICAL FIELD [0001] The present invention relates to a light emitting diode (LED)

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a light emitting diode lighting apparatus, and more particularly, to a light emitting diode lighting apparatus that performs current regulation to control light emission.

Recently, a light emitting diode is used as a light source of a lighting device, and an illumination device using the light emitting diode as described above is called a light emitting diode lighting device.

Light emitting diodes have the advantage of being differentiated from other light sources in various factors such as energy consumption, lifetime and light quality. However, the light emitting diode is driven by a constant current, and the light emitting diode illumination device needs a further configuration of many circuits in order to overcome the constant current characteristics of the light emitting diode.

In order to solve this problem, a light emitting diode lighting device capable of using a commercial AC power source has been developed and a 'LED light emitting device' has been disclosed in Korean Patent Application No. 10-2011-0146391.

An object of the present invention is to provide a light emitting diode lighting device having a small number of parts and a simple structure.

Another object of the present invention is to control the light emission of a light emitting diode lighting device by performing current regulation using a sensing voltage following a change in input voltage having ripple.

The present invention also provides a method of driving a light emitting diode in which a sensing voltage corresponding to a change in input voltage having ripple is fed back to obtain a corresponding voltage for each channel of a series connected light emitting diode, As shown in FIG.

According to an aspect of the present invention, there is provided a light emitting diode lighting apparatus comprising: a power supply circuit for providing an input voltage having ripple; An LED array forming channels including a light emitting diode and emitting light corresponding to the input voltage; A constant current control circuit for providing a current path to said LED array; A current sensing resistor for providing a sensing voltage corresponding to the current on the current path; And a voltage sensing circuit for providing the constant current control circuit with a number of comparison voltages corresponding to the channels, wherein the comparison voltages are level-adjusted corresponding to a change in the sensing voltage, And the current path is provided to one of the channels according to a result of comparing the voltage with the comparison voltage corresponding to each channel.

Further, a light emitting diode illumination device of the present invention, which provides a current path for light emission of an LED array corresponding to an input voltage having ripple, comprises: a current sensing resistor for providing a sensing voltage corresponding to the current on the current path; A voltage sensing circuit providing a number of comparison voltages corresponding to the channels included in the LED array, the comparison voltages being adjusted in level corresponding to a change in the sensing voltage; And a constant current control circuit for providing the current path to any one of the channels based on a result of comparing the reference voltage with the comparison voltage corresponding to each channel.

According to the present invention, it is possible to realize a light emitting diode lighting device having a small number of parts and a simple structure.

According to the present invention, it is possible to control the light emission of the LED lighting device in response to a change in the input voltage having ripple. Particularly, the control for providing the current path for light emission has a fixed reference voltage and an input voltage And can be accurately controlled by using the sensing voltage following the change.

1 is a circuit diagram showing a preferred embodiment of a light-emitting diode lighting device of the present invention.
2 is a waveform diagram illustrating operational characteristics of the embodiment of FIG.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. It is to be understood that the terminology used herein is for the purpose of description and should not be interpreted as limiting the scope of the present invention.

The embodiments described in the present specification and the configurations shown in the drawings are preferred embodiments of the present invention and are not intended to represent all of the technical ideas of the present invention and thus various equivalents and modifications Can be.

The light emitting diode lighting apparatus of the present invention emits a light emitting diode (LED) array (20) using an AC power source. The light emission of the LED array 20 can be controlled in response to a change in the input voltage VIN converted from the AC voltage by the AC power source.

Referring to FIG. 1, an embodiment of the present invention includes a rectifier circuit 10, an LED array 20, a constant current control circuit 30, a voltage sensing circuit 40, and a current sensing resistor Rs.

The rectifying circuit 10 includes an AC power supply Vs for supplying an AC voltage and a rectifier for providing an input voltage VIN rectified by the AC voltage.

Here, the AC power supply Vs may be a commercial AC power supply. Also, the AC power supply Vs may be the output voltage of the AC to AC converter. The rectifying part includes diodes D1 to D4 and performs full-wave rectification of an AC voltage having a sinusoidal waveform by bridge coupling of the diodes D1 to D4.

The voltage obtained by full-wave rectification of the AC voltage in the rectifying circuit 10 may be provided as the input voltage VIN of the LED array 20 and the input voltage VIN has ripple rising and falling in half a cycle of the AC voltage . In the embodiment of the present invention, the level change of the input voltage VIN means a change of the ripple.

The LED array 20 includes four light emitting diodes (LED1 to LED4) connected in series. Although the embodiment of the present invention has been described with respect to four light emitting diodes (LED1 to LED4) as one light emitting diode for the sake of simplicity, the present invention is not limited thereto and may be applied to two or more light emitting diodes connected in series, . ≪ / RTI > The number of light emitting diodes included in the LED array 20 is not limited to four, and may be reduced or increased according to the intention of the manufacturer. That is, the LED array 20 forms the channels including the light emitting diodes, and each channel corresponds to the light emitting diodes (LED1, LED2 to LED4) of FIG.

When the input voltage VIN rises, the LED array 20 emits light first from the side to which the input voltage VIN is applied, and sequentially emits light sequentially from the side to which the input voltage VIN is applied And the number of light emitting diodes that emit light increases. In contrast, when the input voltage VIN falls, the LED array 20 sequentially extinguishes the light emitting diodes in the reverse order of the above-described light emission, and the number of light emitting diodes that emit light decreases. At this time, the constant current control circuit 30 may provide a current path for light emission to one of the output terminals of the light emitting diodes LED1 to LED4.

A current path must be provided for light emission of the LED array 30 and a current path for light emission of the LED array 20 may be provided by the constant current control circuit 30. [ That is, the constant current control circuit 30 has a function of controlling the light emission of the LED array 20 and selectively providing a current path corresponding to the change of the input voltage VIN.

The constant current control circuit 30 includes four driving circuits 31 to 34 and the driving circuits 31 to 34 are configured to correspond one-to-one to the output terminals of the light emitting diodes LED1 to LED4. That is, the driving circuit 31 forms a current path between the output terminal of the light emitting diode LED1 and the current sensing resistor Re, and the driving circuit 32 generates a current path between the output terminal of the light emitting diode LED2 and the current sensing resistor Re And the drive circuit 33 forms a current path between the output terminal of the light emitting diode LED3 and the current sensing resistor Re and the drive circuit 34 forms a current path between the output terminal of the light emitting diode LED4 and the current sensing resistor Re, RTI ID = 0.0 > Re. ≪ / RTI >

Each of the driving circuits 31 to 34 includes operational amplifiers 36a to 36d and driving elements 38a to 38d.

Here, the positive terminal (+) of the operational amplifiers 36a to 36d is provided with the reference voltage VREF, and the reference voltage VREF may have a fixed level. The reference voltage VREF may be provided in an internal voltage generating circuit (not shown) or provided externally.

A comparison voltage may be provided to the negative terminal (-) of the operational amplifiers 36a to 36d. The comparison voltage may be provided to have different levels for the driving circuits 31 to 34. [ The comparison voltages provided to the operational amplifiers 36a to 36d of the driving circuits 31 to 34 may be defined as V1, V2, V3, and Ve, respectively, and may have different levels. Illustratively, the comparison voltage V1 provided to the operational amplifiers 36a to 36d of the driving circuit 31 has the highest level, and the comparison voltage V2, the comparison voltage V3, and the comparison voltage Ve As shown in FIG.

The driving elements 38a to 38d may be NPN or NMOS transistors. The driving elements 38a to 38d may be configured such that the output of the operational amplifiers 36a to 36d is applied to the gate and the drain and the source respectively provide the current path between the output terminal of the light emitting diode and the current sensing resistor Re. More specifically, the output terminal of the light emitting diode may be connected to the drain of the driving elements 38a to 38d, and the current sensing resistor Re may be connected to the source.

In the above configuration, the current sensing resistor Re may be configured such that one ends thereof are commonly connected to the sources of the driving circuits 31 to 34, and the other ends thereof are grounded.

The voltage sensing circuit 40 is configured to provide the comparison voltages V1, V2, V3, and Ve to the negative terminals of the operational amplifiers 36a to 36d of the driving circuits 31 to 34, respectively. Here, the comparison voltage Ve may be configured to share a voltage formed in the current sensing resistor Re.

The voltage sensing circuit 40 includes a transistor Q1 to Q3, an operational amplifier 42 and resistors R1 to R3 and a current mirror circuit using a current sensing resistor (V1 to V3, Ve) having a level corresponding to the sensing voltage of the reference voltage (Vref, Re). Here, the transistors Q1 to Q3 may be composed of a bipolar transistor or a MOS transistor. Q1 and Q2 may be PNP or PMOS transistors, and Q3 may be NPN or NMOS transistors.

The configuration of the voltage sensing circuit 40 will be described in detail.

The transistor Q1, the transistor Q3 and the resistor Rr are connected in series between the terminal to which the operating voltage VDD is applied and the ground. The output terminal of the operational amplifier 42 is connected to the gate of the transistor Q3 and the negative terminal thereof is connected to the node between the source and the resistor Rr and the positive terminal of the operational amplifier 42 is connected to the current sensing resistor Re Respectively. That is, the positive terminal (+) of the operational amplifier 42 is configured to receive the sensing voltage of the current sensing resistor Re. The embodiment of the present invention is configured such that the sensing voltage of the current sensing resistor Re is applied to the comparison voltage Ve provided to the negative terminal (-) of the operational amplifier 34 of the driving circuit 34. [

On the other hand, the transistors Q1 and Q2 are configured such that gates are coupled to each other, and the operating voltage VDD is commonly applied to the drains. The transistor Q1 is configured such that the gate is connected in common to the source. The resistor R3 connected in series is connected between the current sensing resistor Re and the positive terminal of the operational amplifier 42. The resistor R3 is connected in series to the source of the transistor Q2, Lt; / RTI >

In the above configuration, the comparison voltage V1 is provided at the node between the transistor R2 and the resistor R1, the comparison voltage V2 is provided at the node between the resistor R1 and the resistor R2, ) And the resistor R3 is provided with the comparison voltage V3.

The operational amplifier 42, the transistor Q3 and the resistor Rr function as a sensing circuit for sensing the sensing voltage of the current sensing resistor Re to control the amount of current, R2 and R3 function as a voltage dividing circuit for outputting comparison voltages and transistors Q1 and Q2 are connected to a current mirror circuit for providing a current corresponding to the amount of current of the sensing circuit to the resistors R1, Lt; / RTI >

The operation of the embodiment of the present invention configured as described above will be described.

The voltage for causing the light emitting diodes LED1 to LED4 to emit light may be defined as a light emitting voltage. More specifically, a voltage required for light emission of the light emitting diode LED1 is a light emitting voltage of the light emitting diode LED1, a voltage required for light emission of the light emitting diodes LED1 to LED2 is a light emitting voltage of the light emitting diode LED2, A voltage required for light emission of the light emitting diodes LED1 to LED3 is a light emitting voltage of the light emitting diode LED3 and a voltage necessary for light emission of the light emitting diodes LED1 to LED4 is defined as a light emitting voltage of the light emitting diode LED4.

Fig. 2 is a waveform diagram illustrating a case of driving four light emitting diodes (LED1 to LED4), and is for explaining the correlation between the input voltage and the currents I1 to I4 on the current path.

First, the rectifying circuit 10 provides the input voltage VIN so as to have a waveform that full-wave rectifies the AC voltage as shown in FIG. That is, the input voltage VIN is repeatedly raised and lowered in half a cycle of the alternating-current voltage of the alternating-current power supply Vs.

Then, the drive circuits 31 to 34 maintain the turn-on in the initial state. That is, the initial state means that the light emitting diodes LED1 to LED4 are not lighted. In the initial state, the sensing voltage formed in the current sensing resistance Re is low and the levels of the comparison voltages V1 to V3, Ve provided to the drive circuits 31 to 34 are also low. That is, since the comparison voltages V1 to V3 and Ve at a level lower than the reference voltage VREF are applied to the negative terminals (-) of the operational amplifiers 36a to 36d, the operational amplifiers 36a to 36d are turned on And the driving elements 38a to 38d maintain the turned-on state corresponding thereto.

When the sensing voltage formed in the current sensing resistor Re in the voltage sensing circuit 40 rises, the output of the operational amplifier 42 rises and the amount of current flowing through the transistor Q3 correspondingly increases.

The transistors Q1 and Q2 act as a current mirror circuit. Therefore, the amount of current flowing through the transistor Q1 and the transistor Q2 is proportional to the channel ratio. That is, when the amount of current of the transistor Q1 increases, the amount of current of the transistor Q2 also increases.

Therefore, if the sensing voltage increases and the amount of current of the transistor Q3 increases, the amount of current of the transistor Q1 increases, and as a result, the amount of current of the transistor Q2 increases. The increase in the amount of current of the transistor Q2 raises the comparison voltages V1 to V3, Ve of the respective nodes formed at both ends of the resistors R1 to R33.

That is, when the sensing voltage of the current sensing resistor Re rises, the voltage sensing circuit 40 provides the comparison voltages V1 to V3 and Ve of the increased level, and the sensing voltage of the current sensing resistor Re falls The lower voltage sensing circuit 40 provides the lowered comparison voltages V1 to V3, Ve.

The driving circuits 31 to 34 provide a current path between the light emitting diode and the current sensing resistor Re only when the comparison voltage applied to the driver circuit 31 to 34 is equal to or lower than the reference voltage VREF. That is, the drive circuits 31 to 34 cut off the current path between the light emitting diode and the current sensing resistor Re when the comparison voltage applied to the driver circuit 31 to 34 exceeds the reference voltage VREF.

When the input voltage VIN rises gradually in the initial state and reaches the light emitting voltage of the light emitting diode LED1, the light emitting diode LED1 emits light, and the current path for light emission is formed by the drive circuit 31 at this time. Then, the current I1 flows to the current sensing resistor Re via the drive circuit 31 providing the current path.

The current path by the driving circuit 31 is maintained until the input voltage VIN rises to the light emitting voltage of the light emitting diode LED2.

Then, when the input voltage VIN reaches the light emitting voltage of the light emitting diode LED2, the light emitting diodes LED1 and LED2 emit light, and a current path for light emission is formed by the drive circuit 32 at this time. Then, the current I2 flows to the current sensing resistor Re via the drive circuit 32 which provides the current path.

Then, the current amount of the current sensing resistance Re changes as shown in FIG. 2, and the sensing voltage of the current sensing resistance Re rises accordingly. As a result, the comparison voltages V1 to V3, Ve rise. The rising width of the comparison voltages V1 to V3, Ve may correspond to the change in the amount of current shown in Fig. The comparison voltage V1 is higher than the reference voltage VREF by the current I2 and the comparison voltage V2 rises to the same level as the reference voltage VREF and the remaining comparison voltages V3 and Ve are And is raised to have a level lower than the reference voltage VREF.

Therefore, in the driving circuit 31, the output of the operational amplifier 36a is lowered and the driving element 38a is turned off. As a result, the current path by the driving circuit 31 is cut off, and the current path for the light emission of the LED array 20 is formed by the driving circuit 32. [

The current path by the driving circuit 32 is maintained until the input voltage VIN rises to the light emitting voltage of the light emitting diode LED3.

Then, when the input voltage VIN reaches the light emission voltage of the light emitting diode LED3, the light emitting diodes LED1, LED2, and LED3 emit light, and the current path for light emission is formed by the drive circuit 33 . Then, the current I3 flows to the current sensing resistor Re via the drive circuit 33 providing the current path.

Then, the current amount of the current sensing resistance Re changes as shown in FIG. 2, and the sensing voltage of the current sensing resistance Re rises accordingly. As a result, the comparison voltages V1 to V3, Ve rise. The increase width of the comparison voltages V1 to V3 and Ve may correspond to the change in the amount of current in Fig. 2 and the comparison voltages V1 and V2 become higher than the reference voltage VREF by the current I3, V3 rise to be the same level as the reference voltage VREF and the remaining comparison voltage Ve rises to be lower than the reference voltage VREF.

Therefore, in the driving circuit 32, the output of the operational amplifier 36b is lowered and the driving element 38b is turned off. As a result, the current path by the drive circuit 32 is cut off, and the current path for the light emission of the LED array 20 is formed by the drive circuit 33. [

The current path by the driving circuit 33 is maintained until the input voltage VIN rises to the light emitting voltage of the light emitting diode LED4.

Then, when the input voltage VIN reaches the light emitting voltage of the light emitting diode LED4, the light emitting diodes LED1, LED2, LED3, and LED4 emit light, . Then, the current I4 flows to the current sensing resistor Re via the drive circuit 34 providing the current path.

Then, the current amount of the current sensing resistance Re changes as shown in FIG. 2, and the sensing voltage of the current sensing resistance Re rises accordingly. As a result, the comparison voltages V1 to V3, Ve rise. At this time, the rising width of the comparison voltages V1 to V3 and Ve may correspond to the variation of the current amount of FIG. 2, and the comparison voltages V1, V2 and V3 are higher than the reference voltage VREF by the current I4, The comparison voltage Ve rises to the same level as the reference voltage VREF.

Therefore, in the driving circuit 33, the output of the operational amplifier 36c is lowered and the driving element 38c is turned off. As a result, the current path by the drive circuit 33 is cut off, and the current path for the light emission of the LED array 20 is formed by the drive circuit 34. [

After all of the light emitting diodes LED1 to LED4 are lit, the input voltage VIN rises to the highest level and then begins to fall.

When the input voltage VIN falls below the light emitting voltage of the light emitting diodes LED1 to LED4, the light emitting diode LED4 is extinguished. The sensing voltage of the current sensing resistor Re falls corresponding to the lowering of the input voltage VIN and as a result the comparison voltages V1 to V3 and Ve become the current I3 by the drive circuit 33 Lt; RTI ID = 0.0 > a < / RTI > current path. That is, the current path for the light emission of the LED array 20 is formed by the drive circuit 33.

The LEDs LED3, LED2 and LED1 are sequentially extinguished when the input voltage VIN gradually falls to fall below the light emitting voltage of the light emitting diodes LED1 to LED3, LED1 to LED2, and LED1. The sensing voltage of the current sensing resistor Re falls corresponding to the lowering of the input voltage VIN and as a result the comparison voltages V1 to V3 and Ve are generated by the driving circuits 33, To a level that forms a current path for currents I3, I2, I1. That is, the current path for the light emission of the LED array 20 is shifted in the reverse order corresponding to the light emission.

When the input voltage VIN falls to a level of the initial state, all of the light emitting diodes LED1 to LED4 are extinguished, and the driving circuits 31 to 34 wait for the current path formation to turn on.

The embodiment of the present invention constructed and operated as described above can provide a current path corresponding to the rise and fall of the input voltage VIN using one current sensing resistor. Therefore, the light emitting diode illumination device can be realized with a small number of parts and a simple structure.

In addition, the embodiment of the present invention can control the light emission of the light emitting diode lighting device in response to the change of the input voltage having ripple. In particular, the control for providing the current path for light emission uses a fixed level reference voltage The effect can be accurately controlled.

In addition, the embodiment of the present invention can provide an improved power factor by applying a comparison voltage that follows an input voltage without using an inductor or a capacitor element, and an effect that a current path for light emission can be provided by current regulation of a driving circuit .

10: rectifier circuit 20: LED array
30: constant current control circuit 31, 32, 33, 34: drive circuit
36a to 36d, 42: operational amplifiers 38a to 38d:
40: Voltage sensing circuit

Claims (12)

A power supply circuit for providing an input voltage having ripple;
An LED array forming channels including a light emitting diode and emitting light corresponding to the input voltage;
A constant current control circuit for providing a current path to said LED array;
A current sensing resistor for providing a sensing voltage corresponding to the current on the current path; And
And a voltage sensing circuit that provides the constant current control circuit with a number of comparison voltages corresponding to the channels, and the comparison voltages are level-adjusted corresponding to the change in the sensing voltage,
Wherein the constant current control circuit provides the current path to any one of the channels according to a comparison result between a reference voltage provided to have the same level for each channel and a comparison voltage provided to have a different level for each channel Wherein the light emitting diode illuminating device is a light emitting diode. 2. The constant current control circuit according to claim 1,
And a driving circuit for comparing the reference voltage and the comparison voltage, the level of which is adjusted in correspondence with the variation of the sensing voltage, to form the current path, wherein the driving circuits comprise a light emitting diode . The driving circuit according to claim 2,
An operational amplifier for comparing the reference voltage and the comparison voltage whose level is adjusted corresponding to a change of the sensing voltage; And
And a driving element for forming the current path by a signal output from the operational amplifier. The method of claim 3,
Wherein the reference voltage of the driving circuit has a fixed level. The voltage sensing circuit according to claim 1,
A sensing circuit for sensing the sensing voltage and controlling an amount of current;
A voltage dividing circuit for outputting the comparison voltages; And
And a current mirror circuit for providing a current corresponding to an amount of current of the sensing circuit to the voltage divider circuit,
Wherein the comparison voltages are adjusted in response to a change in the sensing voltage. 6. The method of claim 5,
Wherein the voltage divider circuit includes a plurality of resistors connected in series to the current sensing resistor and outputs the comparison voltages at the nodes formed between the current sensing resistor and the plurality of resistors. 1. A light emitting diode lighting apparatus for providing a current path for light emission of an LED array corresponding to an input voltage having ripple,
A current sensing resistor for providing a sensing voltage corresponding to the current on the current path;
A voltage sensing circuit providing a number of comparison voltages corresponding to the channels included in the LED array, the comparison voltages being adjusted in level corresponding to a change in the sensing voltage; And
A constant current control circuit for providing the current path to any one of the channels according to a comparison result between a reference voltage provided to have the same level for each channel and a comparison voltage provided to have a different level for each channel, And a light emitting diode (LED) 8. The constant current control circuit according to claim 7,
And a driving circuit for comparing the reference voltage and the comparison voltage, the level of which is adjusted in correspondence with the variation of the sensing voltage, to form the current path, wherein the driving circuits comprise a light emitting diode . 9. The driving circuit according to claim 8,
An operational amplifier for comparing the reference voltage and the comparison voltage whose level is adjusted corresponding to a change of the sensing voltage; And
And a driving element for forming the current path by a signal output from the operational amplifier. 10. The method of claim 9,
Wherein the reference voltage of the driving circuit has a fixed level. 8. The voltage sensing circuit of claim 7,
A sensing circuit for sensing the sensing voltage and controlling an amount of current;
A voltage dividing circuit for outputting the comparison voltages; And
And a current mirror circuit for providing a current corresponding to an amount of current of the sensing circuit to the voltage divider circuit,
Wherein the comparison voltages are adjusted in response to a change in the sensing voltage. 12. The method of claim 11,
Wherein the voltage divider circuit includes a plurality of resistors connected in series to the current sensing resistor and outputs the comparison voltages at the nodes formed between the current sensing resistor and the plurality of resistors.

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