KR101520605B1 - Pulse driving apparatus and method of LED using AC power - Google Patents

Abstract

The present invention relates to an apparatus and a method for driving a pulse of a light emitting diode using an AC power source, and a pulse driving method of the present invention sets a minimum driving voltage and a maximum driving voltage according to the number of a plurality of light emitting diodes , Monitors the waveform of the input AC voltage and compares it with the minimum drive voltage and the maximum drive voltage and then turns on the LED array when the input AC voltage is between the minimum drive voltage and the maximum drive voltage, Off of the plurality of light emitting diodes connected in series, thereby discontinuously driving the plurality of light emitting diodes connected in series only in a specific voltage section, thereby improving the heat loss and the heat generation due to the continuous driving

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pulse driving apparatus and method for driving a light emitting diode

The present invention relates to a driving method of a light emitting diode (LED), and more particularly to a driving method of a light emitting diode (LED), in which a light emitting diode turns on only when a waveform of an input AC voltage using an AC power source is within a specific range, And more particularly, to a pulse driving apparatus and method for driving a light emitting diode.

Conventional lighting devices use incandescent lamps or fluorescent lamps and have a problem of a large power consumption and a short duration. In place of such conventional lighting devices, lighting devices using LEDs (Light Emitting Diodes) have been developed.

LED is a semiconductor device that emits light by flowing current to a compound such as an LED. A LED that emits white light following an LED that emits yellow light, green light, blue light, or red light has been developed. Accordingly, It is expected to be commercialized. An illumination device using an LED has a relatively long lifetime, a high response speed, and low heat generation.

Switch-Mode Power Supply (SMPS), a common power supply used in lighting equipment using LEDs, converts commercial AC power into rectified and smoothed DC voltage and converts it into a high frequency AC voltage using a switching device To the secondary side through a transformer, and then rectified and smoothed to obtain a desired DC voltage. At this time, the output voltage is determined according to the number of serially connected LEDs used as a load, and the output current is determined according to the number of parallel connection.

Such a SMPS has a disadvantage that circuit configuration is complicated because it involves a switching noise problem (EMI) generated in the process of converting to an AC voltage of a high frequency and requires power conversion at various stages during operation. In addition, due to the transformer using an iron core, it has a large volume to the rated value, a problem of lifetime due to an aluminum electrolytic capacitor used for smoothing the output stage, and the limit of the number of series connected LEDs due to the output voltage limitation. These problems have several limitations in applying LEDs to lighting devices.

According to an aspect of the present invention, there is provided a method of driving an LED, including turning on an LED at a predetermined interval according to an input AC voltage waveform of an AC power source, turning off an LED at a remaining interval, and to provide a pulse driving apparatus and method of a light emitting diode using an AC power source capable of driving a pulse.

According to an aspect of the present invention, there is provided an LED driving apparatus including a plurality of light emitting diodes (LEDs) including a plurality of light emitting diodes connected in series, the method comprising: monitoring an AC voltage input from an AC power source, A comparator for comparing a predetermined minimum driving voltage and a predetermined maximum driving voltage, and an LED array including a plurality of light emitting diodes connected in series when the AC voltage is located between the minimum driving voltage and the maximum driving voltage, And turning off the LED array when the AC voltage is less than the minimum driving voltage or exceeds the maximum driving voltage.

The minimum driving voltage is set to be larger than the sum of the operating voltages of the plurality of light emitting diodes included in the LED array and set to be smaller than the maximum driving voltage in the pulse driving apparatus of the light emitting diode using the AC power source of the present invention .

In the pulse driving apparatus for a light emitting diode using an AC power source according to the present invention, when the sum of the operating voltages of the LEDs included in the LED array is equal to or less than a predetermined value, And the drive unit turns on the LED array when the AC voltage is equal to or less than the maximum drive voltage.

In the pulse driving apparatus for a light emitting diode using an AC power source according to the present invention, the maximum driving voltage is a duty ratio that is a ratio of a time when the LED array is turned on as compared with one period of the AC voltage And is set to maintain a constant value.

In the pulse driving apparatus for a light emitting diode using an AC power source according to the present invention, the maximum driving voltage is set such that the duty ratio is a value between 9% and 11%.

In the pulse driving apparatus for an LED using an AC power source, the LED array may include LED groups each including a plurality of LEDs connected in series, and the comparator may be connected to a specific one of the LED groups The comparison operation is performed according to the minimum driving voltage or the maximum driving voltage set differently from each other corresponding to each of the LED groups when the number of the LEDs included in the LED group is different from the number of the LEDs included in the other LED group .

The pulse driving apparatus for an LED using an AC power source according to the present invention may further include an LDO (Low Drop Out) regulator connected to the AC power source, wherein the comparator or the driver receives an internal bias voltage from the LDO regulator, Is supplied.

In the pulse driving apparatus for a light emitting diode using an AC power source according to the present invention, the driver uses a driving current having a relatively higher value than the driving current in the case of continuously driving the LED when the input AC voltage is higher than a specific voltage, And turns on the LED array when the AC voltage is between the minimum driving voltage and the maximum driving voltage.

According to an aspect of the present invention, there is provided a method of driving a light emitting diode using an AC power source, the method including driving a plurality of light emitting diodes included in an LED array, A comparison step of monitoring the waveform of the AC voltage input from the AC power source and comparing the AC voltage with the minimum driving voltage and the maximum driving voltage, Turning on the LED array if it is located between the minimum drive voltage and the maximum drive voltage and turning off the LED array when the alternating voltage is below the minimum drive voltage or exceeds the maximum drive voltage And a control unit.

According to the pulse driving apparatus and method for driving a light emitting diode using an AC power source according to the present invention, when driving a plurality of LEDs connected in series by using an AC power source, the AC power source is not driven continuously in a section where the waveform of the AC voltage is higher than the rated driving voltage It is possible to improve the heat loss and the heat generation problem due to continuous driving by pulse-discontinuously driving only in a specific voltage section.

In the pulse driving section, a relatively high driving current is supplied to the light emitting diode and turned on as compared with the conventional continuous driving method, so that it is possible to control to emit light of relatively high illuminance during pulse driving, The heat generation can be solved by cooling in a turn-off interval relatively longer than the pulse drive period.

In addition, a power supply such as a SMPS (Switch-Mode Power Supply) is not required, which can improve problems such as switching noise, circuit complexity, volume increase, cost increase, and a capacitor for output stage smoothing, And an internal bias voltage for the operation of the pulse driving device itself or the comparator or the driver can be provided using an LDO (Low Drop Out) regulator connected to the AC power source.

1 is a block diagram showing a configuration of a pulse driving apparatus according to an embodiment of the present invention.
2 is a diagram for explaining a driving period of a pulse driving apparatus according to an embodiment of the present invention.
3 is a schematic diagram of a circuit of a pulse driving apparatus according to an embodiment of the present invention.
4 is a schematic diagram of a circuit of a pulse driving apparatus according to another embodiment of the present invention.
5 is a flowchart illustrating a pulse driving method according to an embodiment of the present invention.

In the following description, only parts necessary for understanding the embodiments of the present invention will be described, and the description of other parts will be omitted so as not to obscure the gist of the present invention.

The terms and words used in the present specification and claims should not be construed as limited to ordinary or dictionary meanings and the inventor is not limited to the meaning of the terms in order to describe his invention in the best way. It should be interpreted as meaning and concept consistent with the technical idea of the present invention. Therefore, the embodiments described in the present specification and the configurations shown in the drawings are merely preferred embodiments of the present invention, and are not intended to represent all of the technical ideas of the present invention, so that various equivalents And variations are possible.

The present invention relates to a technique of pulse-driving a light emitting diode in a specific section in accordance with an input AC voltage waveform of an AC power source. Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 is a block diagram showing a configuration of a pulse driving apparatus 100 according to an embodiment of the present invention.

1, the pulse driving apparatus 100 drives the LED array 3 by using an input AC voltage rectified by the rectifier 2 supplied from the AC power supply 1, and a comparator 10 and a driver (20).

The LED array 3 includes a plurality of light emitting diodes (LEDs) connected in series. At this time, the LED array 3 may include light emitting diodes of various colors such as red, yellow, green, blue, and white. In addition, the LED array 3 may have a configuration in which LED groups each including a plurality of LEDs connected in series are connected in parallel to each other.

An AC power supply (1) supplies an AC voltage for driving the LED array (3).

The rectifier 2 supplies a rectified input voltage to an AC input voltage supplied to the AC power supply 1 to the pulse driving apparatus 100. The rectifier 2 is connected to a full wave rectifier full-wave rectifier.

The pulse drive device 100 turns on and pulse-drives the LED array 3 when the input AC voltage rectified in the rectifier 2 is located between the minimum drive voltage and the maximum drive voltage of the LED array 3 .

At this time, the comparator 10 included in the pulse driving apparatus 100 monitors the waveform of the input AC voltage supplied from the AC power supply 1 through the rectifier 2, and outputs a predetermined minimum driving voltage and a predetermined maximum driving voltage Compare with voltage. At this time, the comparator 10 may have a comparison unit for comparing the input AC voltage with the minimum drive voltage, and a comparison unit for comparing the input AC voltage with the maximum drive voltage.

The driver 20 included in the pulse driving apparatus 100 turns on the LED array 3 when the input AC voltage as a result of the comparison of the comparator 10 is located between the minimum driving voltage and the maximum driving voltage, The LED array 3 is turned off when the input AC voltage is below the minimum drive voltage or exceeds the maximum drive voltage. The minimum drive voltage and the maximum drive voltage of the LED array 3 can be set according to the number of series connection of the light emitting diodes included in the LED array 3. [

That is, the minimum driving voltage for driving the LED array 3 is set to be larger than the sum of the operating voltages of the plurality of light emitting diodes included in the LED array and smaller than the maximum driving voltage. For example, the minimum driving voltage (? V _F ) is obtained by multiplying the sum (V _sum ) of the operating voltages of a plurality of LEDs connected in series by the product of the driving current (I) of the plurality of light emitting diodes and the internal resistance value Value (? _VF = V _sum + I * R).

The maximum driving voltage for driving the LED array 3 is set so that the duty ratio, which is the ratio of the time when the LED array 3 is turned on compared with one period of the AC voltage, do. For example, the maximum driving voltage may be set so that the duty ratio is between 9% and 11%, and in particular, the duty ratio may be set to 10%.

If the sum of the operating voltages of the light emitting diodes included in the LED array 3 according to the embodiment is less than or equal to a predetermined value, the comparator 10 skips the operation of comparing the input AC voltage with the minimum driving voltage, To the maximum driving voltage. That is, if the number of LEDs included in the LED array 3 is not small, the minimum driving voltage is relatively small, and as a result, the period in which the input AC voltage becomes less than the minimum driving voltage becomes relatively short, 10) compares the input AC voltage with only the maximum drive voltage while omitting comparison with the minimum drive voltage. In this case, the driver 20 turns on the LED array 3 when the input AC voltage is equal to or less than the maximum drive voltage according to the comparison result of the comparator 10, The voltage is automatically turned off in a period shorter than the voltage, and is automatically turned on at the time when the input AC voltage exceeds the minimum driving voltage.

In one embodiment of the present invention, the LED arrays 3 each include a plurality of LEDs connected in series and are connected in parallel to each other to be connected in a multi-channel form. In this case, if the number of light emitting diodes included in each LED group is equal to each other, the minimum drive voltage and the maximum drive voltage corresponding to each LED group can be set to be the same. On the other hand, if the number of light emitting diodes included in the specific LED group among the LED groups included in the LED array 3 is different from the number of the LEDs included in the other LED group, The driving voltage can be set differently. In this case, the comparator 10 may have a comparison unit for comparing the input AC voltage with the minimum driving voltage or the maximum driving voltage for each LED group.

A section in which the pulse driving apparatus 100 drives the LED array 3 among the input AC voltages will be described in detail with reference to FIG.

2 is a diagram for explaining a driving period of a pulse driving apparatus according to an embodiment of the present invention.

2, is supplied from the AC power supply, and the waveform of the input alternating voltage (V _ac (t)) full-wave rectification by the rectifier shown, an input alternating voltage (V _ac (t)) is the minimum driving voltage (ΣV _F A period B where the input AC voltage V _ac (t) is between the minimum drive voltage V _F and the maximum drive voltage V _P , an input AC voltage V _ac (t) ) Is greater than the maximum driving voltage (V _P ).

The conventional LED driving apparatus continuously drives the LEDs to turn on in the section B and the section C of the waveform of the input AC voltage V _ac (t) shown in FIG. That is, the conventional LED driving device includes an input alternating voltage (V _ac (t)) is the minimum driving voltage (ΣV _F) or more turns on the LED in the section B-wave changes in one and the input alternating voltage (V _ac (t)) The input AC voltage V _ac (t) changes to the section A and the minimum driving voltage V (t) is changed to the minimum driving voltage V (t) after continuously driving so as to maintain the LED turned on during the corresponding period B, _F ), the LED is turned off. Similarly, even if the LED starts to turn on at a specific point in the period B or C, the input AC voltage V _ac (t) falls below the minimum driving voltage (? V _F ) And turns off at the change point of the A section. However, such a conventional LED driving apparatus has a problem that power is excessively supplied in a section C where the input AC voltage V _ac (t) is relatively higher than the rated driving voltage of the LED, and heat loss due to heat generation occurs.

On the other hand, the pulse driving apparatus of the present invention drives the LED to turn on only in the section B except the section C of the waveform of the input AC voltage V _ac (t) shown in FIG. In other words, the pulse driving apparatus of this embodiment is pulse-driven so that the LED array is turned on only in a period in which the input AC voltage is between the minimum drive voltage (? V _F ) and the maximum drive voltage (V _P ).

In this case, the maximum driving voltage may be set so that the duty ratio is, for example, between 9% and 11%, and in particular, the duty ratio may be set to 10%. At this time, the width of the turn-on pulse should be 10ms or less, and when the frequency of the AC power is 60Hz, one cycle of the full-wave rectified AC waveform is less than 10ms.

At this time, the pulse driving apparatus of the present invention allows the driving current to be supplied to the LED array relatively higher than the LED driving current of the conventional continuous driving method. For example, when a driving current of 100 mA is used in the conventional continuous driving method, the pulse driving apparatus of the present invention can use a driving current of 280 mA to 300 mA, And the overall luminance degradation due to the pulse driving can be improved.

The pulse drive also turns on the LED array using a relatively high rated current in a relatively short length of section B, and turns off and turns off the LED array in section A and section C of relatively long length, The heat generation problem due to the current can be solved.

The circuit configuration of the pulse driving apparatus according to the present invention will be described with reference to Figs. 3 and 4. Fig.

3 is a diagram schematically showing a circuit of the pulse driving device 200 according to an embodiment of the present invention.

Referring to FIG. 3, the pulse driving device 200 is implemented as an integrated circuit (IC).

In the present embodiment, the pulse driving apparatus 200 drives the LED array 3 using the input AC power rectified through the rectifier 2 of the bridge diode type.

At this time, the comparator 10 of the pulse driving device 200 monitors the waveform of the input AC voltage and compares it with a predetermined minimum driving voltage and a preset maximum driving voltage.

The constant current driver 20 of the pulse driving device 200 turns on the LED array 3 when the input AC voltage of the comparator 10 is between the minimum drive voltage and the maximum drive voltage, The LED array 3 is turned off when the AC voltage is below the minimum drive voltage or exceeds the maximum drive voltage. In this case, the switch 8 for the turn-on or turn-off control of the light emitting diodes included in the LED array is connected to the bias circuit of the constant current driver 20 to turn the constant current source on or off .

At this time, the drive current of the LED array 3 is _set using R _set (7), and is set so as not to exceed the pulse drive rated current of the light emitting diode. The internal bias voltage of the pulse driving apparatus 200 in the form of an integrated circuit can be supplied through an LDO (Low Drop Out) regulator 4 connected to an AC power source via the rectifier 2. [ In this case, the stabilization time of the LDO regulator 4 can be designed in consideration of the case where the input alternating-current voltage becomes lower than the output voltage of the LDO regulator 4 and becomes higher again.

The pulse drive device 200 also includes a control logic 5 and an overtemperature protection unit 6.

The functions and operations of the pulse driving apparatus 200 including the comparator 10 and the driver 20 are similar to those described with reference to FIG. 1 and FIG. 2, so a detailed description thereof will be omitted.

4 is a diagram schematically showing a circuit of a pulse driving apparatus 300 according to another embodiment of the present invention.

Referring to FIG. 4, the pulse driving device 300 is implemented using a discrete device.

In the present embodiment, the pulse driving apparatus 300 drives the LED array 3 using the input AC power rectified through the rectifier 2 of the bridge diode type.

At this time, the comparator 10 of the pulse driving device 300 monitors the waveform of the input AC voltage and compares it with a predetermined minimum driving voltage and a preset maximum driving voltage.

The constant current driver 20 of the pulse driving device 300 turns on the LED array 3 when the input AC voltage as a result of the comparison of the comparator 10 is located between the minimum drive voltage and the maximum drive voltage, The LED array 3 is turned off when the AC voltage is below the minimum drive voltage or exceeds the maximum drive voltage. In this case, the switch 9 for the turn-on or turn-off control of the light emitting diodes included in the LED array is directly connected to the alternating current source via the rectifier 2 to turn the input alternating voltage itself on or off Turn off.

At this time, the drive current of the LED array 3 is _set using R _set (7), and is set so as not to exceed the pulse drive rated current of the light emitting diode. The internal bias voltage of the integrated circuit can be supplied through an LDO (Low Drop Out) regulator 4 connected to the AC power source via the rectifier 2. [ In this case, the stabilization time of the LDO regulator 4 can be designed in consideration of the case where the input alternating-current voltage becomes lower than the output voltage of the LDO regulator 4 and becomes higher again.

The function and operation of the pulse driving device 300 including the comparator 10 and the driver 20 are similar to those described with reference to FIGS. 1 to 3, and thus a detailed description thereof will be omitted.

The process of pulse-driving the LED array according to one embodiment of the present invention will be described with reference to FIG.

5 is a flowchart illustrating a pulse driving method according to an embodiment of the present invention.

Referring to FIG. 5, a minimum driving voltage and a maximum driving voltage of the pulse driving device for driving the LED array are set according to the number of the LEDs included in the LED array in series (S1).

In step S1, the minimum driving voltage may be set to be larger than the sum of the operating voltages of the plurality of light emitting diodes included in the LED array and smaller than the maximum driving voltage, for example. If the sum of the operating voltages of the light emitting diodes included in the LED array is less than a predetermined value, the minimum driving voltage may not be separately set in step S1.

In step S1, the maximum driving voltage may be set such that, for example, the duty ratio, which is the ratio of the time during which the LED array is turned on, compared with one period of the input AC voltage, maintains a constant value. At this time, the maximum driving voltage may be set so that the duty ratio is between 9% and 11%, and in particular, may be set to be 10%.

If the LED array in step S1 is a parallel connection of LED groups including a plurality of LEDs connected in series, the corresponding minimum driving voltage or maximum driving voltage may be set differently for each LED group.

Subsequently, the pulse driving apparatus monitors the waveform of the input AC voltage inputted from the AC power source, and compares the AC voltage with the minimum driving voltage and the maximum driving voltage set in step S1 (S2).

If the number of LEDs included in the LED array is small and the minimum driving voltage is not separately set in step S1, the pulse driving device in step S2 compares only the monitored input AC voltage with the maximum driving voltage.

Alternatively, if the LED array of step S1 includes the LED groups including the LED groups connected in parallel to each other and the minimum driving voltage or the maximum driving voltage is separately set, the pulse driving apparatus of step S2 sets the input AC voltage to the minimum And the driving voltage and the maximum driving voltage, respectively.

When the input AC voltage is between the minimum drive voltage and the maximum drive voltage as a result of the comparison in step S2, the pulse drive device turns on the LED array, and the AC voltage is less than the minimum drive voltage or the maximum drive voltage If exceeded, the pulse drive device turns off the LED array (S3).

If the pulse driving device of step S2 is only to perform the comparison operation between the input AC voltage and the maximum driving voltage by setting only the maximum driving voltage without the minimum driving voltage in step S1, Turns on the LED array in an interval in which the input AC voltage is equal to or less than the maximum driving voltage. In this case, the LED array is automatically turned off at an interval where the input AC voltage is below the minimum drive voltage, and is turned on as the input AC voltage reaches the minimum drive voltage.

The minimum driving voltage and the maximum driving voltage are separately set including the LED groups in which the LED arrays in step S1 are connected in parallel to each other, and the pulse driving apparatus in step S2 sets the input AC voltage to the minimum driving If the voltage or the maximum driving voltage is compared with each other, the pulse driving apparatus of step S3 separately performs the turn-on or turn-off control of the LED group according to the result of each comparison.

The pulse driving method according to the embodiment of the present invention may be implemented in a form of a program readable by various computer means and recorded in a computer-readable recording medium.

It should be noted that the embodiments 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. Furthermore, although specific terms are used in this specification and the drawings, they are used in a generic sense only to facilitate the description of the invention and to facilitate understanding of the invention, and are not intended to limit the scope of the invention.

1: AC power supply 2: Rectifier
3: LED array 10: comparator
20: driver 100, 200, 300: pulse driving device

Claims (9)

An LED array including a plurality of light emitting diodes connected in series;
A comparator for monitoring a waveform of an AC voltage input from an AC power source and comparing the AC voltage with a predetermined minimum driving voltage and a predetermined maximum driving voltage; And
Wherein the comparator turns on the LED array including a plurality of light emitting diodes connected in series when the alternating voltage is located between the minimum driving voltage and the maximum driving voltage, A driver for turning off the LED array when the maximum driving voltage is exceeded;
And a driving circuit for driving the pulse of the light emitting diode using the AC power. The method according to claim 1,
The minimum driving voltage may be,
And the driving voltage of the light emitting diode is set to be larger than the sum of the operating voltages of the plurality of light emitting diodes included in the LED array and smaller than the maximum driving voltage. 3. The method of claim 2,
The comparator comprising:
And comparing the maximum driving voltage with the AC voltage except for the minimum driving voltage when the sum of the operating voltages of the LEDs included in the LED array is equal to or less than a predetermined value,
The driver includes:
And the LED array is turned on when the AC voltage is equal to or less than the maximum driving voltage. The method according to claim 1,
The maximum driving voltage may be,
Wherein the duty ratio is a ratio of a time when the LED array is turned on as compared with one period of the AC voltage so that the duty ratio maintains a constant value. 5. The method of claim 4,
The maximum driving voltage may be,
Wherein the duty ratio is set to a value between 9% and 11%. The method according to claim 1,
The LED array includes:
LED groups including a plurality of LEDs connected in series are connected in parallel with each other,
The comparator comprising:
When the number of the LEDs included in the specific LED group among the LED groups is different from the number of the LEDs included in the other LED group, the minimum driving voltage or the maximum driving voltage And the comparison operation is performed according to the comparison result. The method according to claim 1,
Further comprising an LDO (Low Drop Out) regulator connected to the AC power source,
Wherein the comparator or the driver is supplied with an internal bias voltage from the LDO regulator. The method according to claim 1,
The driver includes:
When the AC voltage is located between the minimum drive voltage and the maximum drive voltage, using the drive current having a value relatively higher than the drive current when the LED is continuously driven when the input AC voltage is higher than the specific voltage, Wherein the pulse driving is performed by turning on the light emitting diode. A setting step of setting a minimum drive voltage and a maximum drive voltage of the LED array according to the number of serially connected plurality of light emitting diodes included in the LED array;
A comparison step of monitoring a waveform of an AC voltage input from an AC power source and comparing the AC voltage with the minimum drive voltage and the maximum drive voltage; And
Turning on the LED array when the alternating voltage is between the minimum driving voltage and the maximum driving voltage as a result of the comparison in the comparing step and the alternating voltage is less than the minimum driving voltage or exceeding the maximum driving voltage A driving step of turning off the LED array when the LED array is turned on;
Wherein the step of driving the light emitting diode comprises the steps of:

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