KR20160130009A - Drive circuit structure for different type LED - Google Patents

Abstract

The present invention relates to a circuit structure for driving heterologous LEDs, and more particularly, to a circuit structure for driving the heterologous LEDs, which are capable of improving both efficiency and power factor thereof. The circuit structure for driving the heterologous LEDs includes a string including at least two LED devices of which the kinds are different from each other and driven by a driving current at a driving voltage in the first voltage range; and a current control unit for allowing an LED device selected from the LED devices of the string to be driven by an auxiliary driving current at a driving voltage in the second voltage range.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001]

The present invention relates to a circuit structure for driving different kinds of LEDs, and more particularly, to a circuit structure for driving different types of LEDs capable of improving both efficiency and power factor.

An LED device is a diode having a PN junction structure fabricated using a semiconductor manufacturing process. The LED device emits extra energy into light when the electron and the hole are combined in the PN junction. The wavelength of the light output from the LED element varies depending on the kind of the material constituting the LED element and the impurity added in the manufacturing process.

The LED device is smaller than the conventional light source, has a long life, is efficient, and has a high-speed response characteristic. The LED device has been recently used as a backlight source of a flat panel display device having a liquid crystal display device due to the above-mentioned advantages.

A flat panel display device using an LED element as a backlight source has advantages in terms of color reproducibility and life span as compared with the case of using a previous fluorescent lamp as a backlight source.

In recent years, LED devices have been used in lighting devices by taking advantage of the advantages of high brightness, low power consumption and long lifetime of LED devices. One LED device may be used to make an LED lighting device, or a plurality of LED devices may be connected in series or in parallel to form an LED lighting device.

If one or a relatively small number of LED elements are used to constitute the lighting device, the power factor characteristic representing the ratio of the effective power to the apparent power is improved in the AC circuit, but the efficiency characteristic is deteriorated.

On the other hand, if lighting is configured using a string in which a relatively large number of LED elements are connected in series, the power factor characteristic becomes relatively poor and the efficiency characteristic becomes better.

KR 10-2011-0023551 A KR 10-2011-0090201 A KR 10-2012-0018460 A KR 10-1175934 B1

SUMMARY OF THE INVENTION It is an object of the present invention to provide a circuit structure for driving different types of LEDs capable of improving both efficiency and power factor.

According to an aspect of the present invention, there is provided a circuit structure for driving a heterogeneous LED comprising at least two or more different types of LED elements, wherein the LED element is driven by a main driving current in a first voltage interval of the driving voltage A string; And a current controller for driving the LED element selected from the LED elements of the string to be driven by the auxiliary driving current in a second voltage interval of the driving voltage.

And a main current limiting element for limiting an amount of a main driving current of the string.

And the amount of the auxiliary driving current is smaller than the amount of the main driving current.

And a bridge circuit unit for rectifying the input AC voltage and providing the rectified AC voltage as the driving voltage.

Wherein the current controller includes: a first switch unit for allowing the auxiliary driving current to flow to the selected LED element at a first voltage level that is a one-side limit value of the second voltage section; And a second switch unit for controlling the first switch unit to allow the auxiliary drive current to flow at a second voltage level that is the other end of the second voltage interval.

Wherein the current control unit further comprises an auxiliary current limiting element connected to the selected LED element for causing the auxiliary driving current to flow from the selected LED element to the first switch unit, A first voltage distributor for distributing the reference voltage; And a first transistor for turning on the auxiliary driving current in accordance with a voltage level of the reference node and flowing the auxiliary driving current from the auxiliary current limiting element to a ground voltage supply terminal, 2 voltage divider; And a second transistor for selectively connecting the reference node and the ground voltage supply terminal in response to a voltage distributed by the second voltage distributor.

Wherein the current control unit includes a plurality of unit current controllers for receiving the driving voltages and causing corresponding LED elements among the LED elements of the string to be driven by respective predetermined auxiliary driving currents, Wherein each of the plurality of current control units has a different amount of current and each of the plurality of current control units has a different amount of current, And the LED element connected to the first LED element is connected to the last LED element connected to the first LED element.

The circuit structure for driving different kinds of LEDs according to the present invention has an advantage of improving both the power factor and the efficiency characteristic.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a circuit diagram showing a circuit structure for driving a different type of LED for explaining the present invention; Fig.
Fig. 2 is a waveform diagram showing an operation of a circuit structure for driving different kinds of LEDs shown in Fig. 1; Fig.
FIG. 3 is a diagram showing the characteristics of a circuit structure for driving a heterogeneous LED shown in FIG. 1; FIG.
4 is a circuit diagram showing a circuit structure for driving a heterogeneous LED according to the present invention;
Fig. 5 is a waveform diagram showing the operation of a circuit structure for driving different kinds of LEDs shown in Fig. 4; Fig.
Fig. 6 is a waveform diagram showing operational characteristics of a circuit structure for driving different types of LEDs shown in Fig. 4; Fig.
FIG. 7 is a block diagram showing an embodiment of the unit current controller shown in FIG. 4. FIG.
8 is a waveform diagram for explaining the operation of the unit current control unit shown in Fig.
FIG. 9 is a circuit diagram according to an embodiment of the unit current controller shown in FIG. 4. FIG.

Hereinafter, a circuit structure for driving different types of LEDs according to a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings.

1 to 9 show a circuit structure for driving different kinds of LEDs according to the present invention.

Fig. 1 is a circuit diagram showing a circuit structure for driving different types of LEDs for explaining the present invention.

Referring to FIG. 1, the circuit structure for driving different types of LEDs includes a bridge circuit unit 20, a current limiting device 30, and a string 40 in which a plurality of LED devices are connected in series.

The bridge circuit unit 20 includes four diodes D1 to D4 for receiving an AC voltage from the power supply unit 10 and providing a rectified voltage to the string 40. [

The current limiting element 30 may be implemented as a resistor, a capacitor, a bipolar transistor, or a MOS transistor so that a constant amount of current is supplied to the string 40.

The string 40 includes a plurality of LED elements connected in series, and the circuit structure for driving the different types of LEDs may be configured such that the number and type of LED elements provided in the string 40 are determined according to the amount or color of light to be output All.

2 is a waveform diagram showing the operation of the circuit structure for driving the different types of LEDs shown in FIG. In particular, the AC voltage provided from the power supply unit 10 shows a positive value.

FIG. 3 is a diagram showing characteristics of a circuit structure for driving the different types of LEDs shown in FIG. 1; FIG.

The driving current flowing in the string 40 may be the first case C1 and the second case C2 when the input voltage VIN output by the bridge circuit unit 20 changes.

The first case C1 has a relatively large number of LED elements included in the string 40 and the second case C2 has a relatively small number of LED elements included in the string 40. [ In the case of the first case C1, since the number of LED elements included in the string 40 is large, a driving current flows in the string 40 in the first section X having a relatively large voltage Vb or more, In the first section X, light is emitted from the string 40.

In the case of the second case C2, since the number of LED elements included in the string 40 is small, a driving current flows in the string 40 in the second section Y having a relatively small voltage Va or more, In the second section Y, light is emitted from the string 40.

Power factor and efficiency are factors used to judge the performance of the lighting device. The power factor refers to the effective power against the supplied apparent power, and the efficiency represents how much light can be output to the supplied electric energy.

When the number of LED elements included in the string is large, that is, in the first case, the power factor is bad and the efficiency is good.

3, when a large number of LED elements are used in the string 40 as in the first case C1, the current limiting element 30 takes a relatively small voltage as compared with the string 40, So that the efficiency characteristics are good. However, when there are many LED elements in the string 40, there is a large phase difference between the input voltage VIN and the driving current flowing in the string 40, so that the power factor characteristic deteriorates.

As shown in FIG. 3, when the LED element is used in a small amount in the string 40 as in the second case, the voltage is relatively large in the current limiting element 30 as compared with the string 40, The power characteristic is good because the phase difference is relatively small between the input voltage VIN and the driving current flowing in the string 40. [

As described above, if the LED driving device is designed as shown in FIG. 1, if the efficiency characteristic is increased, the power factor characteristic deteriorates, and if the power factor characteristic is increased, the efficiency characteristic becomes worse. In order to solve this problem, the present invention proposes a circuit structure for driving different kinds of LEDs capable of simultaneously improving power factor and efficiency characteristics.

4 is a circuit diagram showing a circuit structure for driving different types of LEDs according to a preferred embodiment of the present invention. Referring to FIG. 4, the circuit structure for driving different types of LEDs according to the present embodiment includes a bridge circuit unit 200, a current control unit 300, a string 400, and a main current limiting device 500.

The bridge circuit unit 200 is provided with four diodes D5 to D8 for receiving the AC voltage supplied from the power supply unit 100 and providing the driving voltage VIN rectified to the string 400. [

The current controller 300 includes a plurality of unit current controllers 300_1 to 300_n.

In the string 400, a plurality of LED devices receiving a driving voltage VIN are connected in series.

The main current limiting element 500 is disposed between the string 400 and the ground voltage supply terminal VSS such that the string 400 is driven by the main current I2. The main current limiting element 500 allows a main driving current I2 having a predetermined amount to flow from the string 400 to the ground voltage supply terminal VSS. The main current limiting element 500 may be implemented by a resistor, a capacitor, a bipolar transistor, or a MOS transistor.

The plurality of unit current controllers 300_1 to 300_n are respectively connected to the LED elements included in the string 400. Each of the unit current controllers 300_1 to 300_n generates a predetermined driving current As shown in FIG. Here, the plurality of unit current controllers 300_1 to 300_n correspond to a plurality of LED devices provided in the string 400 in a one-to-one correspondence. However, in some cases, the plurality of LED devices provided in the string 400 may be grouped, and the unit current controllers 300_1 to 300_n may be configured to correspond to each group in a one-to-one correspondence.

5 is a waveform diagram showing the operation of the circuit structure for driving the different types of LEDs shown in FIG.

5, a plurality of auxiliary driving currents I_1 to I_n are generated by the unit current controllers 300_1 to 300_n when the driving voltage VIN changes, The main current limiting element 500 generates the main driving current I2. The main driving current I2 has a larger current amount than the auxiliary driving currents I_1 to I_n so that the efficiency is maintained and the power factor can be improved.

The string 400 is driven by the main driving current I2 in the first voltage interval T1 of the driving voltage VIN and the current control unit 300 is driven by the driving voltage I2 having the voltage level lower than the first voltage interval T1 And the corresponding LED element is driven by the auxiliary driving currents I_1 to I_n in the second voltage period T2 of the driving voltage VIN.

The plurality of unit current controllers 300_1 to 300_n may be configured such that a predetermined current (for example, I_1) in each of the sections a, b, and c having different voltage levels in the second voltage section T2 To the ground voltage supply terminal (VSS). In this case, the amount of current flowing in each of the periods a, b, and c has different values. In particular, the current flows from the first connected LED device to the last connected LED device by the corresponding unit current control unit The amount of current increases further.

It is preferable that the plurality of unit current controllers 300_1 to 300_n have a plurality of auxiliary driving currents I_1 to I_n within the range in which the driving voltage VIN varies. 5, when the driving voltage VIN changes in a semicircular shape, the values of the plurality of auxiliary driving currents I_1 to I_n gradually increase as the driving voltage VIN increases So that the shape of the maximum number of auxiliary driving currents I_1 to I_n and the main driving current I2 matches the shape of the driving voltage VIN. The form of the plurality of auxiliary driving currents I_1 to I_n and the main driving current I2 should be as close as possible to the driving voltage VIN to improve the power factor characteristics. However, the plurality of auxiliary driving currents I_1 to I_n may be configured such that the plurality of auxiliary driving currents I_1 to I_n have a constant value or decrease as the driving voltage VIN increases as needed.

FIG. 6 is a waveform diagram showing operational characteristics of the circuit structure for driving the different types of LEDs shown in FIG.

As shown in FIG. 6, in the circuit structure for driving different types of LEDs according to the present embodiment, in the process of changing the driving voltage VIN, a current generation pattern P1 ), And operates along the current generation pattern P2 whose power factor characteristics are improved. This is because the circuit structure for driving the different types of LEDs according to the present embodiment is different from the circuit structure in which all the LED elements of the string 400 operate (refer to T1 section in FIG. 5) within a section in which the driving voltage VIN varies (See the T2 section of FIG. 5) also include a plurality of current controllers 300_1-300_n for each LED element. For reference, the current generation pattern P3 represents a case where the power factor is 100%.

The circuit structure for driving different LEDs of the present invention can be configured such that the current control units 300_1 to 300_n are properly configured so that the power factor can be substantially 100%. In addition, the unit current controllers 300_1 to 300_n may be configured to satisfy the power factor required for a situation in which a circuit structure for driving different types of LEDs is applied.

7 is a block diagram showing an embodiment of the unit current controller shown in FIG.

Referring to FIG. 7, the first unit current controller 300_1 includes an auxiliary current limiting element 310, a first switch 320, and a second switch 330.

The auxiliary current limiting element 310 is for causing the auxiliary driving current I_1 to flow. The first switch unit 320 causes the auxiliary driving current I-1 to flow from the corresponding LED element to the auxiliary current limiting element 310 at the first voltage level V1 of the driving voltage VIN.

The second switch unit 330 controls the first switch unit 310 so that the auxiliary driving current I_1 flows at the second voltage level V2 of the driving voltage VIN. 7, the unit current control unit includes the first switch unit 320, the second switch unit 330, and the auxiliary current limiter 310. However, when the unit current control unit includes the first switch unit 320, the second switch unit 330, The auxiliary current limiting element 310 may be omitted.

8 is a waveform diagram for explaining the operation of the current control unit shown in FIG.

8, the first switch unit 320 is activated at a first voltage level V1 within a section in which the drive voltage VIN is input and increased, and the auxiliary current limit element 310 The auxiliary driving current I-1 flows.

The second switch unit 330 causes the first switch unit 320 to be deactivated at the second voltage level V2 so that the auxiliary drive current I_1 no longer flows. The second switch unit 330 activates the first switch unit 320 to allow the auxiliary drive current I_1 to flow at a second voltage level V2 within a period in which the drive voltage VIN is input and decreased .

The first switch unit 320 is inactivated at the first voltage level V1 so that the auxiliary driving current I-1 no longer flows.

9 is a circuit diagram according to an embodiment of the unit current controller of FIG.

9, the first switch unit 320 includes a first voltage distributor 321 for distributing the driving voltage VIN on the basis of the reference node O, And a first transistor T1 for turning on the auxiliary current limiting element 310 to supply a current from the auxiliary current limiting element 310 to the ground voltage supply terminal VSS.

The first voltage divider 321 includes resistors R1 and R2. Although the first transistor T1 is a bipolar transistor, the first transistor T1 may be a MOS transistor. The first switch unit 320 includes a zener diode Z1 between the base end of the first transistor T1 and the ground voltage supply terminal VSS for stabilizing the voltage applied to the base end of the first transistor T1 do.

The second switch unit 330 includes a second voltage distributor 331 for distributing the drive voltage VIN and a second voltage distributor 331 for distributing the drive voltage VIN to the reference node O in response to the voltage distributed by the second voltage distributor 331. [ And a second transistor T2 for selectively connecting the ground voltage supply terminal VSS. Although the second transistor T2 is implemented as a bipolar transistor, the second transistor T2 may be a MOS transistor.

The second switch unit 330 includes a zener diode Z2 between the base of the second transistor T2 and the ground voltage supply terminal VSS for stabilizing the voltage applied to the base end of the second transistor T2 Respectively.

9, the unit current control unit includes the first switch unit 320, the second switch unit 330, and the auxiliary current limiting device 310. However, the unit current control unit may include the first switch unit 320, the second switch unit 330, The auxiliary current limiting element 310 may be omitted. In this case, the amount of current flowing through the transistor T1 provided in the first switch unit 320 can be appropriately controlled to allow a desired current to flow at a desired timing.

9, when the driving voltage VIN increases, the voltage is applied to the reference node O by the first voltage distributor 321 of the first switch unit 320, The first transistor T1 is turned on. When the first transistor T1 is turned on, the auxiliary driving current I-1 flows from the auxiliary current limiting element 130 to the ground voltage supply terminal VSS.

Due to this current, the LED element corresponding to the auxiliary current limiting element 130 operates. When the drive voltage VIN continues to increase, the second transistor T2 is turned on by the voltage divided by the second voltage distributor 331. [

When the second transistor T2 is turned on, the first transistor T1 is turned off. Therefore, the auxiliary driving current I-1 no longer flows. When the driving voltage VIN further increases in this state, all the LED elements provided in the string 400 are turned on, so that the main driving current I 2 flows through the string 400.

At this time, all the LED elements provided in the string 400 are operated. When the driving voltage VIN is lowered and the voltage distributed by the second voltage distributor 331 falls below a predetermined level, the second transistor T2 is turned off.

As a result, the first transistor T1 is turned on and the auxiliary driving current I-1 flows again. When the driving voltage VIN further decreases, the level of the voltage distributed by the first voltage distributor 321 falls below a predetermined level and the first transistor T1 is turned off and the auxiliary driving current I- 1) does not flow anymore.

FIG. 9 shows one of the unit current controllers (for example, 300_1) shown in FIG. 4. The timing at which the plurality of unit current controllers in the current controller 300 operate is determined by the respective transistors (for example, T1 , T2) are turned on and off. Here, the turn-on and turn-off timings of the transistors T1 and T2 are determined by the resistance values of the resistors R1 to R4.

5, the resistance value of the resistors R1 to R4 included in the unit current control unit of the current control unit 300 is increased as the number of the nodes LED_1 to LED_n increases Can be used.

As described above, in the circuit structure for driving different types of LEDs according to the present embodiment, a relatively large number of LED elements are connected in series to the string 400, and the unit current controllers 300_1 to 300_n So that the auxiliary driving current can flow through the corresponding LED element.

All the LED elements provided in the string 400 are driven by the main driving current I2 flowing by the main current limiting element 500 and each LED element is driven by a corresponding unit current control part, And is driven by currents I_1 to I_n.

Since the auxiliary driving current is relatively smaller than the main driving current at this time, the efficiency characteristic is not substantially affected, and the auxiliary driving current flows in addition to the main driving current in the process of changing the driving voltage (VIN) The power factor characteristic of the circuit structure is improved.

In addition, since the circuit structure for driving different types of LEDs according to the present embodiment includes a relatively large number of LED elements in the string 400, the circuit structure for driving the different types of LEDs including the string 400 is good Efficiency characteristics can be expected.

As a result, the circuit structure for driving different types of LEDs according to the present embodiment can expect good efficiency characteristics and good power factor characteristics due to a relatively large number of LED elements and a unit current controller connected to each LED element.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. It will be appreciated that other equivalent embodiments are possible.

Therefore, the scope of the true technical protection of the present invention should be determined by the technical idea of the appended claims.

100: AC power supply
200: Bridge circuit part
300:
400: String
500: Main current limiting element

Claims (7)

A string driven by a main driving current in a first voltage interval of a driving voltage, the string including at least two or more different kinds of LED elements;
And a current controller for driving an LED element selected from the LED elements of the string to be driven by an auxiliary driving current in a second voltage interval of the driving voltage. The method according to claim 1,
Further comprising a main current limiting element for limiting a current amount of the main driving current of the string. The method according to claim 1,
And the amount of the auxiliary driving current is smaller than the amount of the main driving current. The method according to claim 1,
Further comprising a bridge circuit unit for rectifying an input AC voltage and providing the rectified AC voltage as the driving voltage. The method according to claim 1,
The current control unit
A first switch unit for allowing the auxiliary driving current to flow to the selected LED element at a first voltage level which is a one-side limit value of the second voltage section;
And a second switch unit for controlling the first switch unit to allow the auxiliary drive current to flow at a second voltage level that is a second threshold voltage of the second voltage section Circuit structure. 6. The method of claim 5,
The current control unit further comprises an auxiliary current limiting element connected to the selected LED element for causing the auxiliary driving current to flow from the selected LED element to the first switch unit,
Wherein the first switch unit includes: a first voltage distributor for distributing the drive voltage based on a reference node; And a first transistor for turning on the auxiliary driving current in accordance with a voltage level of the reference node and flowing the auxiliary driving current from the auxiliary current limiting element to a ground voltage supply terminal,
A second voltage distributor for distributing the driving voltage; And a second transistor for selectively connecting the reference node and a ground voltage supply terminal in response to a voltage distributed by the second voltage distributor. The method according to claim 1,
Wherein the current controller includes a plurality of unit current controllers for receiving the driving voltages and causing the corresponding LED elements of the strings to be driven by respective predetermined auxiliary driving currents,
Wherein the second voltage section has a different voltage range for each of the plurality of unit current controllers,
Each of the auxiliary driving currents controlled by the plurality of current control units has a different amount of current,
Wherein a current amount of each of the auxiliary driving currents controlled by the plurality of current control units is increased as the LED device connected to the string is connected to the last LED device connected to the string.

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