KR20150076831A - Apparatus for driving light emitting diode - Google Patents

Abstract

The present invention relates to an apparatus for driving a light emitting diode (LED), and especially, to an apparatus for driving a LED, which can prevent overcurrent from flowing into a LED. The apparatus for driving a LED according to the present invention comprises: a light emitting unit which comprises a plurality of LEDs which are classified into one or more groups, wherein switch devices are connected in parallel to the groups; a power unit which rectifies AC power to supply rectified output current to the light emitting unit; a driving unit which receives a driving signal and accordingly operates the switch devices to drive the light emitting unit; and a current overflow protection unit which is connected between the driving unit and the power unit to use the driving signal and accordingly prevents overcurrent from flowing into the light emitting unit.

Description

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

The present invention relates to a light emitting diode driving apparatus, and more particularly, to a light emitting diode driving apparatus capable of preventing an overcurrent from flowing to a light emitting diode.

Recently, light emitting diodes (LEDs) having advantages such as efficiency, color diversity, and design autonomy have been attracting attention as a light source of illumination .

Such an LED is a semiconductor device that emits light when a voltage is applied in a forward direction, has a long lifetime, low power consumption, and has electrical, optical, and physical characteristics suitable for mass production.

In order to use such LED as a light source of illumination, a driving system capable of driving with a commercial AC power source is required.

A single color LED can be used to drive an LED used in a lighting device, but an LED that emits light of a different color to the LED can be driven together to improve the light quality or to add an additional function that changes the color of the light .

In order to drive the LEDs emitting different colors, the LEDs can be divided into groups and driven, and a PWM (Pulse Width Modulation) driving method can be used.

SUMMARY OF THE INVENTION An object of the present invention is to provide a light emitting diode driving apparatus capable of reducing the number of control signals when a plurality of light emitting diodes are driven and preventing an overcurrent from being applied to the light emitting diodes.

According to an aspect of the present invention, there is provided a light emitting device comprising: a light emitting unit including a plurality of light emitting diodes divided into at least one group, the group including switch elements connected in parallel; A power supply unit for rectifying AC power and supplying a current output to the light emitting unit; A driving unit that receives the driving signal and operates the switching device to drive the light emitting unit; And an overcurrent prevention unit connected between the driving signal and the power supply unit to prevent an overcurrent from flowing to the light emitting unit using the driving signal.

Here, the overcurrent prevention unit may cut off the output of the power supply unit when the driving unit turns off the driving of the light emitting unit.

Here, the overcurrent prevention unit may cut off the output of the power supply unit when the driving of the light emitting diode of the light emitting unit is all turned off.

Here, the overcurrent prevention unit may cut off the output of the power supply unit when all the switch elements are turned on in the driving unit.

Here, the overcurrent control unit may include: a reverse current prevention diode connected to the driving signal for driving each group of the light emitting units; And a voltage distributor connected between the backflow prevention diode and the power supply unit.

At this time, the voltage divider may convert the voltage of the driving signal into a voltage capable of turning on / off the operation of the power source unit.

The voltage divider may include a first resistor and a second resistor connected in series to each other and connected to the power supply.

Here, the driving signal of the light emitting unit may be an inverted PWM signal.

The present invention has the following effects.

As the number of input signals to be communicated wirelessly increases because of the wireless communication technology can be applied to the illumination, the increase of the cost of other parts and the complication of the control signal may occur due to the channel increase. However, There is no need for signal level.

That is, the overcurrent prevention unit of the present invention can operate using an external driving signal for operation of the light emitting unit. Therefore, it is not necessary to use a separate signal level to prevent overcurrent.

Therefore, it is possible to reduce the number of communication channels in the illumination system, and to prevent the occurrence of an overcurrent of the circuit itself.

1 is a circuit diagram showing an example of a light-emitting diode driving apparatus.
2 is a schematic diagram showing an example of PWM driving the light emitting diode.
3 is a diagram showing a signal indicating a driving current waveform of the LED driving apparatus.

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

While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings and will herein be described in detail. Rather, the intention is not to limit the invention to the particular forms disclosed, but rather, the invention includes all modifications, equivalents and substitutions that are consistent with the spirit of the invention as defined by the claims.

It will be appreciated that when an element such as a layer, region or substrate is referred to as being present on another element "on," it may be directly on the other element or there may be an intermediate element in between .

Although the terms first, second, etc. may be used to describe various elements, components, regions, layers and / or regions, such elements, components, regions, layers and / And should not be limited by these terms.

1 is a circuit diagram showing an example of a light-emitting diode driving apparatus.

As shown in FIG. 1, the light emitting diode driving apparatus includes a light emitting portion 10 including a plurality of light emitting diodes divided into at least one group.

Fig. 1 shows a light emitting portion 10 composed of three groups (LED1, LED2, LED3). These three groups (LED1, LED2, LED3) may include light emitting diodes (LEDs) emitting light of different colors.

For example, LED1 may be an LED that emits red light, LED2 may be an LED that emits green light, and LED3 may be an LED that emits blue light.

In such an example, the three colors may be mixed with one another and used as illumination to emit white light. However, the present invention is not limited thereto, and various groups and LEDs of various colors may be used. It is needless to say that a single color LED may be used.

The LEDs of these three groups (LED1, LED2, LED3) may each include a plurality of LEDs.

In addition, the switch elements Q1, Q2, and Q3 may be connected in parallel to the respective groups LED1, LED2, and LED3.

The light emitting unit 10 includes a power supply unit 20 that supplies a current for driving the light emitting unit 10.

The power supply unit 20 rectifies the AC power source 21 to output a rectified constant current and supplies the rectified current to the light emitting unit 10. That is, the input of the alternating current I1 may be outputted from the power supply unit 20 to the direct current I2.

The power supply unit 20 includes an AC-DC converter for converting the AC voltage into a constant voltage output using the input of the commercial AC power source 21 and a constant current output for driving the LED of the light emitting unit 10 May be configured as a DC-DC converter.

The switch elements Q1, Q2 and Q3 of the light emitting portion 10 receive drive signals from the outside and operate the switch elements Q1, Q2 and Q3 in accordance with the drive signals to drive the light emitting portion 10 The driving unit 30 is connected.

A driving signal for driving each group (LED1, LED2, LED3) of the light emitting portion 10 is transmitted to the driving portion 30. The driving signal may be a PWM driving signal.

For example, the PWM driving signal may include a first PWM signal PWM_LED1 for driving the LED 1, a second PWM signal PWM_LED2 for driving the LED 2, and a third PWM signal PWM_LED3 for driving the LED 3.

2, a signal for setting a period and a pulse width for driving the respective groups (LED1, LED2, and LED3) is input, and accordingly, the groups (LED1 , LED2, LED3) can be driven.

As described above, by driving LEDs of various colors, the light quality can be improved and the color of light can be changed.

In order to drive light of different colors, the LEDs forming the light emitting portion 10 can be driven for each group (channel) as described above.

To do this, the PWM (Pulse Width Modulation) method can be used in which the LED currents of different groups have different time durations.

In FIG. 2, as an example, PWM driving is performed by applying drive times of the red LED 1, the green LED 2, and the blue LED 3 differently.

Here, the PWM clock signal is a reference unit for determining the start and end of the current of each group. In the clock 1, LED1, LED2 and LED3 are all turned on at the same time.

In the case of the LED 3 emitting blue light, the LED 2 is turned off before the clock 2 is started, and the LED 2 is kept in the on state until the clock 5 is started.

In the case of red LED1, it is turned off before clock 8 starts. As described above, by setting the time differently for each group and driving the current, it is possible to realize light of a specific color according to the mixture of red, green, and blue light.

The driving unit 30 operates the switch circuits Q1, Q2 and Q3 connected to the respective groups LED1, LED2 and LED3.

In the example of the circuit of Fig. 1, when the corresponding switch circuit operates, the current supplied from the power supply unit 20 flows through the switch element without being supplied to the corresponding LED.

That is, the group in which the switch element is turned on can be set so as not to emit light. For example, when the first switch element Q1 is turned on (turned on) by the driver 30, the current flows through the first switch element Q1, so that the LED 1 does not emit light.

More specifically, when an on signal is applied to the gate terminals of the switching elements Q1, Q2 and Q3, the switching elements Q1, Q2 and Q3 are turned on to cut off the current flowing to the LEDs, (Q1, Q2, Q3) to turn off the LED.

When an off signal is applied to the gate terminals of the switching elements Q1, Q2 and Q3, no current flows through the switching elements Q1, Q2 and Q3, and current flows through the LEDs. on.

Since the off reference voltages of the gate signals applied to the respective switch elements Q1, Q2 and Q3 may be different from each other, signals can be applied to the switch elements Q1, Q2 and Q3 using the driving unit 30 , The driving unit 30 receives an external driving signal.

The overcurrent prevention unit 40 may be connected between the driving unit 30 and the power supply unit 20 to prevent the overcurrent from flowing to the light emitting unit 10.

The overcurrent prevention unit 40 is connected to an input terminal to which the drive signals PWM_LED1, PWM_LED2 and PWM_LED3 are inputted and controls the power supply unit 20 using the drive signals PWM_LED1, PWM_LED2 and PWM_LED3, It is possible to prevent an overcurrent from flowing.

The overcurrent prevention unit 40 may cut off the output of the power supply unit 20 when the driving unit 30 turns off the driving of the light emitting unit 10. [

As an example, the overcurrent prevention unit 40 can cut off the output of the power supply unit 20 when all the LEDs of the light emitting unit 10 are turned off.

That is, the overcurrent prevention unit 40 can cut off the output of the power supply unit 20 when all the switching elements Q1, Q2, and Q3 are turned on in the driving unit 30. [

Here, the overcurrent control unit 40 includes the backflow prevention diodes D1, D2, and D3 connected to the driving signals for driving the respective groups of the light emitting units 10 and the backflow prevention diodes D1, D2, and D3, And a voltage distributor 41 connected between the power supply unit 20.

At this time, the voltage divider 41 can convert the voltages of the driving signals PWM_LED1, PWM_LED2, and PWM_LED3 to voltages capable of turning on / off the operation of the power source unit 20. [ In this example of the configuration, the drive signals PWM_LED1, PWM_LED2, and PWM_LED3 may be inverted PWM signals.

The voltage divider 41 may include a first resistor R1 and a second resistor R2 connected in series to each other at an intermediate stage connected to a terminal EN of the power supply unit 20. [ That is, between the first resistor R1 and the second resistor R2 and the EN terminal of the power supply unit 20 are connected to each other.

The drive signals PWM_LED1, PWM_LED2 and PWM_LED3 are connected in parallel to generate a signal for preventing overcurrent in the drive signals PWM_LED1, PWM_LED2 and PWM_LED3, D1, D2, and D3, respectively.

The cathodes of the diodes D1, D2, and D3 are connected in common to the voltage dividing unit 41. That is, the diode is connected to the first resistor R1 and the first resistor R1 is connected in series to the second resistor R2 and the ground. The role of the diodes D1, D2, and D3 may be to prevent backflow to prevent current flow from being turned off in the on signal of the input signal.

The voltage of the signal having the longest on time among the three driving signals PWM_LED1, PWM_LED2 and PWM_LED3 is generated at the potential between the first resistor R1 and the second resistor R2, The resistors R1 and R2 of the voltage distributor 41 are determined to be controllable at the EN (Enable) terminal of the power supply unit 20 through the distributor 41. [

The power source unit 20 is operated during the longest driving time among the LED1, LED2, and LED3, and the power source unit 20 is shut down when the LED is shortened, thereby preventing the overcurrent of the output current.

In this way, the overcurrent prevention unit 40 can operate using a signal for operating the light emitting unit 10. Therefore, no separate signal level is required for overcurrent prevention.

Recently, the number of input signals to be wirelessly communicated with the wireless communication technology is increased and the increase of the cost of other parts and the complication of the control signal may occur due to the channel increase.

However, if it is configured as described above, it is possible to reduce the number of communication channels and to prevent an overcurrent of the circuit itself.

3 shows a signal representing the driving current waveform.

3A shows the sum of the drive voltages of LED1, LED2 and LED3, FIG. 3B shows the output current (current 1) in the state where the overcurrent prevention unit 40 is not provided, Shows a state of an output current (current 2) in a state in which the overcurrent prevention unit 40 is provided.

Time t1 to t2 indicate when the initial LED is turned off, and both the output voltage and the output current are zero.

At time t2 to t3, only the LED 1 (for example, red LED) is turned on, and a constant current begins to flow at this time.

The time t3 to t4 show the voltage and current when the LED1 (red) and the LED2 (green) are turned on, and the waveforms when the LED1, LED2 and LED3 (blue) are turned on at the time t4 to t5.

When both of the LEDs 1, 2, and 3 are turned off, an instantaneous overcurrent flows to the LED due to an instantaneous short of the load end, as shown at t5 of (B) .

However, if the operation of the power supply unit 20 is stopped by the operation of the overcurrent prevention unit 40 as in (C), the overcurrent can be prevented from flowing to the LED.

It should be noted that the embodiments of the present invention disclosed in the present specification and drawings are only illustrative of specific examples for the purpose of understanding and are not intended to limit the scope of the present invention. It will be apparent to those skilled in the art that other modifications based on the technical idea of the present invention are possible in addition to the embodiments disclosed herein.

10: light emitting portion 20: power supply portion
30: Driving unit 40: Overcurrent prevention unit
41: Voltage distribution portion

Claims (8)

A light emitting unit including a plurality of light emitting diodes divided into at least one group, the group including switch elements connected in parallel;
A power supply unit for rectifying AC power and supplying a current output to the light emitting unit;
A driving unit that receives the driving signal and operates the switching device to drive the light emitting unit; And
And an overcurrent prevention unit connected between the driving signal and the power supply unit to prevent an overcurrent from flowing to the light emitting unit using the driving signal. 2. The light-emitting diode drive device according to claim 1, wherein the overcurrent prevention unit cuts off the output of the power supply unit when the driving unit turns off the driving of the light emitting unit. 2. The light emitting diode driving apparatus according to claim 1, wherein the overcurrent prevention unit cuts off the output of the power supply unit when the driving of the light emitting diode of the light emitting unit is all turned off. The light-emitting diode drive device according to claim 1, wherein the overcurrent prevention unit cuts off the output of the power supply unit when all the switch elements are turned on in the drive unit. 2. The overcurrent controller according to claim 1,
A backflow preventing diode connected to each driving signal for driving each group of the light emitting units; And
And a voltage divider connected between the backflow prevention diode and the power supply unit. 6. The light emitting diode driving apparatus according to claim 5, wherein the voltage divider divides the driving signal into a voltage capable of turning on / off the operation of the power source unit. 6. The LED drive device according to claim 5, wherein the voltage divider includes a first resistor and a second resistor connected in series to each other and having an intermediate terminal connected to the power supply. The light emitting diode driving apparatus according to claim 1, wherein the driving signal of the light emitting unit is an inverted PWM signal.

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