WO2015141909A1 - Led driving integrated circuit and driving method thereof - Google Patents

Abstract

An LED driving integrated circuit according to an embodiment of the present invention comprises: an LED array comprising a first to an nth (where n is an integer that is greater than or equal to 2) group of LEDs connected in series; a control unit having a plurality of driving switches connected to the LED array and a driving switch controller for selectively opening and closing the plurality of driving switches; an LED current controlling circuit for controlling the current for each LED group; and a flicker controlling circuit for removing flicker generated due to connection to a dimmer.

Description

LED driving integrated circuit and driving method thereof

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to lighting drive circuits and methods, and more particularly to an LED drive integrated circuit for driving LED lighting, and a driving method thereof.

Recently, as one of the energy saving methods, an efficient LED type light source is introduced instead of an existing inefficient light source.

In the method of driving LED lighting, AC-DC conversion type driving method which largely converts AC power to DC power and then uses LED power to drive LED and AC power to AC without converting AC power to DC power There is an AC direct drive method that directly drives the LEDs as a power source.

In addition, in conventional incandescent lighting, a dimmer (eg, a device for adjusting brightness using a rotary switch) is used to adjust the brightness of an incandescent lamp. However, even if the incandescent lamp is replaced with an LED bulb, the dimmer tends not to be replaced. If you connect an LED bulb to an existing dimmer and adjust the brightness (brightness) of the dimmer, the flicker may be visible to the naked eye.

There are two main causes of flicker. First, the current flowing through the LED bulb is smaller than the latching or holding current required by the dimmer. In this case, the output of the dimmer is turned on and off, causing a misfire that causes repeated flicker of the LED bulb.

Second, flicker may occur even if the current flowing through the LED bulb is greater than the latching current or the holding current. A large difference between the dimmer output waveform coming from the AC power in both directions and the negative dimmer output waveform from the AC power will cause flicker in the LED bulb.

To connect an LED bulb to an existing dimmer, you need to eliminate the visible flicker.

The technical problem to be achieved by the present invention is to provide an AC direct type LED driving circuit that does not generate visual flicker when the LED bulb is connected to the dimmer.

An LED driving circuit according to an embodiment of the present invention includes an LED array including first to nth (n is an integer of 2 or more) LED groups connected in series, a plurality of driving switches connected to the LED array and the driving switches. A control unit including a drive switch controller for selectively opening and closing, an LED current control circuit for adjusting a current flowing through the first to nth LED groups, and a duty average voltage of a rectified voltage of a dimming alternating current (AC) voltage ( and a flicker switching circuit for selectively turning on or off each of the first to nth LED groups by comparing a duty average voltage and a flicker reference voltage.

In example embodiments, the flicker switching circuit may include a duty average detection circuit configured to generate the duty average voltage based on the rectified voltage of the dimming AC voltage, and a plurality of flickers to selectively turn on or off each of the first to nth LED groups. And a flicker switch controller controlling the plurality of flicker switches based on the flicker reference voltage and the duty average voltage corresponding to each of the switches and the first to nth LED groups.

According to an embodiment, the duty average detection circuit may generate a duty detector for generating a duty detection signal by comparing the rectified voltage of the dimming AC voltage with a duty reference voltage and generating the duty average voltage corresponding to an average level of the duty detection signal. An average voltage generator.

According to an embodiment, the flicker switch controller is based on a flicker reference voltage generator that generates the flicker reference voltage corresponding to each of the first to nth LED groups, and a flicker comparison result of comparing the flicker reference voltage and the duty average voltage. And a flicker comparator to control the plurality of flicker switches.

In some embodiments, the electronic device may further include an AC selection circuit configured to sense the voltage across the first LED group to adjust the flicker reference voltage.

In some embodiments, the driving switch controller further includes a circuit for linearly adjusting current and brightness of the LED group corresponding to the driving switch controller based on the duty average voltage and the flicker comparison result.

In some embodiments, the flicker comparator has hysteresis characteristics.

In some embodiments, the flicker reference voltage increases sequentially as the n-th LED group corresponds to the n-th LED group.

In some embodiments, a drain of each of the plurality of flicker switches is connected to a source of each of the plurality of driving switches corresponding to each of the plurality of flicker switches.

In some embodiments, a source of each of the plurality of flicker switches is connected to a drain of each of the plurality of driving switches corresponding to each of the plurality of flicker switches.

In some embodiments, a drain of each of the plurality of flicker switches is connected to a gate of each of the plurality of driving switches corresponding to each of the plurality of flicker switches.

According to an embodiment, each of the plurality of flicker switches and each of the plurality of driving switches is implemented as a single switch, and the flicker control circuit calculates the flicker comparison result and the output of the driving switch controller to operate the one switch. It further includes a calculation circuit for controlling.

An LED driving circuit according to an embodiment of the present invention includes an LED array including first to nth (n is an integer of 2 or more) LED groups connected in series, a plurality of driving switches connected to the LED array and the driving switches. A control unit including a drive switch controller for selectively opening and closing, an LED current control circuit for regulating a current flowing through the first to nth LED groups, and a constant level according to a rectified voltage of a dimming alternating current (AC) voltage And a bleeder circuit for generating a bleeder current.

According to an embodiment, the bleeder circuit is a short pulse bleeder circuit, and a short pulse generator for detecting a rising edge of the rectified voltage of the dimming alternating voltage to generate a short pulse signal having a predetermined interval and the short pulse generator And a short pulse switch to generate the bleeder current according to the short pulse signal.

According to an embodiment, the bleeder circuit is an active bleeder circuit, and the duty average detection circuit generates a duty average voltage based on the rectified voltage of the dimming AC voltage, and compares the duty average voltage with a bleeder reference voltage. A duty comparator for generating a result and an active switch for generating the bleeder current according to the duty comparison result.

An LED driving circuit according to an embodiment of the present invention includes an LED array including first to nth (n is an integer of 2 or more) LED groups connected in series, a plurality of driving switches connected to the LED array and the driving switches. A control unit including a drive switch controller for selectively opening and closing, an LED current control circuit for adjusting a current flowing through the first to nth LED groups, and a duty average voltage of a rectified voltage of a dimming alternating current (AC) voltage ( a flicker switching circuit for comparing the duty average voltage and the flicker reference voltage to selectively turn on or off each of the first to nth LED groups; And a flicker controlling circuit including a bleeder circuit configured to detect a rectified voltage rising edge or a duty average voltage of the dimming alternating voltage to generate a bleeder current of a constant level.

According to the LED driving circuit to which the flicker switching circuit is applied according to an embodiment of the present invention, the flicker phenomenon can be selectively turned off to eliminate the flicker phenomenon.

According to the LED driving circuit to which the bleeder circuit according to the embodiment of the present invention is applied, the flicker phenomenon caused by the misfire of the dimmer can be removed by properly generating the bleeder current.

1 is a schematic block diagram of an LED driving circuit according to an embodiment of the present invention.

FIG. 2 is a timing diagram illustrating the rectified voltage of the dimming alternating current (AC) voltage shown in FIG. 1.

3 is a view briefly showing an embodiment of the LED driving circuit shown in FIG.

4 is a diagram illustrating the duty average detection circuit of FIG. 3.

FIG. 5 is a timing diagram for describing an operation of the duty average detection circuit shown in FIG. 4.

FIG. 6 is a diagram illustrating any one of the flicker switches shown in FIG. 3.

FIG. 7 is a diagram for describing an operating method of an embodiment of the LED driving circuit illustrated in FIG. 3.

FIG. 8 is a view schematically illustrating another embodiment of the LED driving circuit shown in FIG. 1.

FIG. 9 is a view schematically illustrating another embodiment of the LED driving circuit shown in FIG. 1.

FIG. 10 is a view schematically illustrating another embodiment of the LED driving circuit shown in FIG. 1.

FIG. 11 is a diagram illustrating a first driving and flicker controller shown in FIG. 10.

FIG. 12 is a view schematically illustrating another embodiment of the LED driving circuit shown in FIG. 1.

FIG. 13 is a view schematically illustrating another embodiment of the LED driving circuit shown in FIG. 1.

14 and 15 are diagrams for describing an operation of still other embodiments of the LED driving circuit shown in FIGS. 12 and 13.

16 to 28 are schematic views illustrating still other embodiments of the LED driving circuit illustrated in FIG. 1, respectively.

29 to 31 are diagrams illustrating embodiments of the AC selection circuit illustrated in FIG. 1.

32 is a view for explaining the operation of the drive switch controller according to a comparative example of the present invention.

33 is a view for explaining the operation of the drive switch controller according to an embodiment of the present invention.

An LED driving circuit according to an embodiment of the present invention includes an LED array including first to nth (n is an integer of 2 or more) LED groups connected in series, a plurality of driving switches connected to the LED array and the driving switches. A control unit including a drive switch controller for selectively opening and closing, an LED current control circuit for adjusting a current flowing through the first to nth LED groups, and a duty average voltage of a rectified voltage of a dimming alternating current (AC) voltage ( and a flicker switching circuit for selectively turning on or off each of the first to nth LED groups by comparing a duty average voltage and a flicker reference voltage.

In example embodiments, the flicker switching circuit may include a duty average detection circuit configured to generate the duty average voltage based on the rectified voltage of the dimming AC voltage, and a plurality of flickers to selectively turn on or off each of the first to nth LED groups. And a flicker switch controller controlling the plurality of flicker switches based on the flicker reference voltage and the duty average voltage corresponding to each of the switches and the first to nth LED groups.

According to an embodiment, the duty average detection circuit may generate a duty detector for generating a duty detection signal by comparing the rectified voltage of the dimming AC voltage with a duty reference voltage and generating the duty average voltage corresponding to an average level of the duty detection signal. An average voltage generator.

According to an embodiment, the flicker switch controller is based on a flicker reference voltage generator that generates the flicker reference voltage corresponding to each of the first to nth LED groups, and a flicker comparison result of comparing the flicker reference voltage and the duty average voltage. And a flicker comparator to control the plurality of flicker switches.

In some embodiments, the electronic device may further include an AC selection circuit configured to sense the voltage across the first LED group to adjust the flicker reference voltage.

In some embodiments, the driving switch controller further includes a circuit for linearly adjusting current and brightness of the LED group corresponding to the driving switch controller based on the duty average voltage and the flicker comparison result.

In some embodiments, the flicker comparator has hysteresis characteristics.

In some embodiments, the flicker reference voltage increases sequentially as the n-th LED group corresponds to the n-th LED group.

In some embodiments, a drain of each of the plurality of flicker switches is connected to a source of each of the plurality of driving switches corresponding to each of the plurality of flicker switches.

In some embodiments, a source of each of the plurality of flicker switches is connected to a drain of each of the plurality of driving switches corresponding to each of the plurality of flicker switches.

In some embodiments, a drain of each of the plurality of flicker switches is connected to a gate of each of the plurality of driving switches corresponding to each of the plurality of flicker switches.

According to an embodiment, each of the plurality of flicker switches and each of the plurality of driving switches is implemented as a single switch, and the flicker control circuit calculates the flicker comparison result and the output of the driving switch controller to operate the one switch. It further includes a calculation circuit for controlling.

Specific structural to functional descriptions of the embodiments according to the inventive concept disclosed herein are merely illustrated for the purpose of describing the embodiments according to the inventive concept. It may be embodied in various forms and should not be construed as limited to the embodiments set forth herein.

Embodiments according to the inventive concept may be variously modified and have various forms, so specific embodiments are illustrated in the drawings and described in detail herein. However, this is not intended to limit the embodiments in accordance with the concept of the present invention to a particular disclosed form, it should be understood to include all changes, equivalents, and substitutes included in the spirit and scope of the present invention.

Terms such as first and / or second may be used to describe various components, but the components should not be limited by the terms. The terms are used only for the purpose of distinguishing one component from another, for example, without departing from the scope of rights in accordance with the inventive concept, and the first component may be called a second component and similarly The second component may also be referred to as the first component.

When a component is referred to as being "connected" or "connected" to another component, it may be directly connected to or connected to that other component, but it may be understood that other components may be present in between. Should be. On the other hand, when a component is said to be "directly connected" or "directly connected" to another component, it should be understood that there is no other component in between. Other expressions describing the relationship between components, such as "between" and "immediately between," or "neighboring to," and "directly neighboring to" should be interpreted as well.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. As used herein, the terms "comprise" or "having" are intended to indicate that there is a feature, number, step, action, component, part, or combination thereof that is described, and that one or more other features or numbers are present. It should be understood that it does not exclude in advance the possibility of the presence or addition of steps, actions, components, parts or combinations thereof.

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

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

1 is a schematic block diagram of an LED driving circuit according to an embodiment of the present invention. FIG. 2 is a timing diagram illustrating the rectified voltage of the dimming alternating current (AC) voltage shown in FIG. 1.

1 and 2, the LED drive system 10 includes an AC power source 11, a dimmer 12, a rectification circuit 13, and an LED drive circuit 20. can do.

The AC power source 11 may supply an AC voltage Vac to the dimmer 12, and the AC voltage Vac may be a commercial AC voltage (eg, 110V, 220V, etc.), but is not limited thereto.

The dimmer 12 is an example of a brightness controller, and receives an alternating voltage Vac to cut a predetermined section from the waveform of the alternating voltage Vac and passes the remaining section to pass the dimming alternating voltage Vdac. You can adjust the brightness by creating According to an embodiment, the dimmer 12 may be implemented as a leading edge dimmer capable of cutting a predetermined section from the time when the waveform of the AC voltage Vac starts, or the dimmer 12 may be an AC voltage. It may be implemented as a trailing edge dimmer capable of cutting a predetermined period before the end of the waveform of (Vac).

One cycle P1 of the AC voltage Vac is shown in FIG. 2, and only one cycle P1 will be described below for convenience of description. The AC voltage Vac may represent a sinusoidal waveform having a positive peak voltage Vp and a negative peak voltage (-Vp). It is assumed that the positive peak voltage Vp and the negative peak voltage (-Vp) are the same.

Assuming that the dimmer 12 is implemented as a leading edge dimmer, a predetermined section may be cut at the time when each of the positive direction and the negative direction of the AC voltage Vac starts. However, although the actual dimmer 12 has a degree of difference, each predetermined section for cutting the waveform in the positive direction and the negative direction may be different from each other. In addition, the peak voltage Vp1 in the positive direction and the peak voltage (-Vp2) in the negative direction of the dimming AC voltage Vdac passing through the dimmer 12 may be different from each other.

The rectifier circuit 13 may generate a rectified voltage Vrac of the dimming AC voltage Vdac by full-wave rectifying the dimming AC voltage Vdac. For example, the rectifier circuit 13 may be implemented as a bridge diode. As shown in FIG. 2, the rectified voltage Vrac of the dimming AC voltage is represented by full-wave rectification of the dimming AC voltage Vdac. Accordingly, the peak voltage Vp1 and the negative voltage according to the AC voltage Vac in the positive direction are negative. The peak voltage Vp2 according to the AC voltage Vac in the direction becomes different from each other.

The LED driving circuit 20 directly receives the rectified voltage (Vrac) of the dimming AC voltage without converting the AC direct type LED driving circuit, that is, AC power into DC power and then into AC power having a specific frequency and amplitude. It is a circuit that operates.

The LED driving circuit 20 includes an LED array 30, a driving switch unit 40, a driving switch controller unit 50, an AC selection circuit 70, LED current control circuit 80, and flicker controlling circuit 100.

The LED array 30 may include first to n th (n is an integer of 2 or more) LED groups (eg, 30-1 to 30-n of FIG. 3) connected in series. Each LED group 30-1 to 30-n may include at least one LED and may include a plurality of LEDs. In the case of including a plurality of LEDs, the plurality of LEDs in one LED group may be connected in series, parallel, or a mixture of series and parallel. Each LED group 30-1 to 30-n may emit light sequentially according to the waveform of the rectified voltage Vrac of the dimming AC voltage and / or the control of the driving switch controller unit 50.

The drive switch unit 40 may be directly or indirectly on the cathode side of each of the first to nth LED groups 30-1 to 30-n (eg, further including a flicker switch between them as shown in FIG. 8). A plurality of driving switches (eg, DS1 to DSn of FIG. 3) may be included. The plurality of driving switches DS1 to DSn turn on or off each of the first to nth LED groups 30-1 to 30-n under the control of the driving switch controller unit 50. You can.

The driving switch controller unit 50 may include a plurality of driving switch controllers (eg, 50-1 to 50-n in FIG. 3) capable of controlling each of the plurality of driving switches DS1 to DSn.

The AC selection circuit 70 may determine whether the LED driving circuit 20 is for 120V or 220V by sensing a voltage at both ends of the first LED group (30-1 of FIG. 3). The AC selection circuit 70 controls the flicker reference voltage generator (122-i in FIG. 6) of the flicker control circuit 100 in accordance with the determination result, so as to correspond to the flicker reference voltage corresponding to the corresponding application (for 120V or 220V). 6 can be controlled to output Vf-i).

The LED current control circuit 80 may perform constant current control on the driving current flowing through each of the first to nth LED groups 30-1 to 30-n of the LED array 30.

The flicker control circuit 100 is implemented with a flicker switching cirtcuit (e.g., 100-1) or a bleeder circuit (e.g., 100-5 or 100-6), and a combination thereof. Based on the rectified voltage Vrac of the voltage, the flicker phenomenon that may occur when the LED array 30 emits light may be eliminated.

The flicker phenomenon occurs in two cases. First, the peak voltage Vp1 according to the AC voltage Vac in the positive direction and the peak voltage Vp2 according to the AC voltage Vac in the negative direction have a large difference from the rectified voltage Vrac of the dimming AC voltage. When generated, the generated flicker can be removed by the flicker switching circuit. Second, when the current flowing through the LED group is lower than the latching current or the holding current required by the dimmer, a misfire occurs in the dimmer and the output voltage of the dimmer decreases. Flicker occurs at. Flicker caused by the dimmer misfire can be removed using short pulse bleeder circuits or active bleeder circuits.

3 is a view briefly showing an embodiment of the LED driving circuit 20 shown in FIG. 4 is a diagram illustrating the duty average detection circuit 110 shown in FIG. 3. FIG. 5 is a timing diagram for describing an operation of the duty average detection circuit 110 shown in FIG. 4. FIG. 6 is a diagram illustrating any one of the flicker controllers 120-1 through 120-n shown in FIG. 3. FIG. 7 is a view for explaining a method of operating an embodiment of the LED driving circuit 20 shown in FIG.

1 to 7, one embodiment 20-1 of the LED driving circuit 20 includes first to n-th LED groups 30-1 to 30-n and a plurality of driving switches DS1. DSn), a plurality of driving switch controllers 50-1 to 50-n, an AC selection circuit 70, an LED current control circuit 80, and a flicker control circuit 100-1. The flicker control circuit 100-1 is implemented as a flicker switching circuit for removing flicker caused by the difference between Vp1 and Vp2 of the dimming rectified voltage Vrac, and then 100-1, which is an embodiment of the flicker control circuit, is a flicker switching circuit ( 100-1). In addition, the embodiments of the flicker control circuit 100-2 to 100-4 are also defined as the flicker switching circuits 100-2 to 100-4. 12 and 13, which are embodiments of the flicker control circuits illustrated in FIGS. 12 and 13, respectively, are implemented as a bleeder circuit for preventing a dimmer misfire, and then 100-5 and 100 which are embodiments of the flicker control circuit. -6 is defined as a short pulse bleeder circuit (100-5) and an active bleeder circuit (100-6), respectively. 16 to 28 to 100 to 19 are implemented by a combination of at least two or more of the flicker switching circuit, the short pulse bleeder circuit, and the active bleeder circuit.

Each of the first to nth LED groups 30-1 to 30-n, the plurality of driving switches DS1 to DSn, and the plurality of driving switch controllers 50-1 to 50-n, respectively, are illustrated in FIG. 1. It may correspond to the LED array 30, the drive switch unit 40, and the drive switch controller unit 50. The plurality of driving switches DS1 to DSn and the plurality of driving switch controllers 50-1 to 50-n may refer to a control unit that controls a general operation of the LED array 30. The AC selection circuit 70 may generate an AC selection signal ACS by sensing a voltage across the first LED group 30-1. The AC selection signal ACS may be supplied to the flicker switching circuit 100-1. The detailed operation and configuration of the AC selection circuit 70 will be described later with reference to FIGS. 29 to 31.

Referring to the operation of a conventional AC direct type LED bulb that does not include the flicker switching circuit 100-1, the first to nth LED groups 30-1 that receive the rectified voltage Vrac of the dimming AC voltage. ˜30-n may sequentially emit light according to the waveform of the rectified voltage Vrac of the dimming AC voltage (Vrac in FIG. 7A) and the control of the plurality of driving switch controllers 50-1 to 50-n. can do. That is, the stepped waveform of the LED current I _LED means that the driving switches DS1 to DSn connected to the first to nth LED groups 30-1 to 30-n are sequentially turned on or off. For convenience of description, it is assumed herein that the plurality of driving switch controllers 50-1 to 50-n control the plurality of driving switches DS1 to DSn to be always in an on state. That is, when each of the plurality of driving switches DS1 to DSn is implemented as an NMOS transistor, it is assumed that an output of each of the plurality of driving switch controllers 50-1 to 50-n is at a high level.

Therefore, assuming that n is 4, the LED current I _LED according to the rectified voltage Vrac by the alternating voltage Vac in the positive direction of FIG. 7A is the fourth LED group, the third LED group. , The second LED group and the switches connected to the first LED group are turned on to flow. At this time, the LED current (I _LED ) according to the rectified voltage (Vrac) by the alternating voltage (Vac) in the negative direction of Figure 7 (a) is connected to the third LED group, the second LED group, the first LED group Indicates that the switch is turned on and flowing. In a period P1, the fourth LED group is turned on when the first peak voltage of AC power Vrac is Vp1, and the fourth LED group is off when the second peak voltage of AC power Vrac is Vp2. State is maintained. If the fourth group of LEDs is turned on and off for one period, the flicker phenomenon can be visually observed.

The flicker switching circuit 100-1 is a first embodiment of the flicker control circuit 100 shown in FIG. 1 based on a duty average voltage DD of the rectified voltage Vrac of the dimming AC voltage. Each of the to nth LED groups 30-1 to 30-n may be selectively turned on or off.

The flicker switching circuit 100-1 includes a duty average detection circuit 110, a plurality of flicker switches FS1 to FSn, and a plurality of flicker switch controllers 120-. 1 to 120-n).

The duty average detection circuit 110 may generate the duty average voltage Va_D based on the rectified voltage Vrac of the dimming AC voltage. The duty average detection circuit 110 includes a duty detector 112 and an average voltage generator 114 that generates a duty average voltage Va_D corresponding to an average level of the duty detection signal DD. can do.

The duty detector 112 may generate the duty detection signal DD by comparing the rectified voltage Vrac of the dimming AC voltage with the duty reference voltage Vref. In FIG. 5, when the rectified voltage Vrac of the dimming AC voltage is higher than the duty reference voltage Vref, the duty detection signal DD has a high level, and the rectified voltage Vrac of the dimming AC voltage is the duty reference. If the voltage Vref is lower than the duty detection signal DD has a low level.

The average voltage generator 114 may generate a duty average voltage Va_D corresponding to an average level of the duty detection signal DD. That is, the average voltage generator 114 may calculate the average level for a predetermined time, and generate the duty average voltage Va_D based on the calculation result.

If the constant time is assumed to be one period, the duty average voltage Va_D is calculated in the first period, and the calculated duty average voltage Va_D in the first period is the LED array 30 in the second period. However, the duty average voltage Va_D is almost constant in successive cycles assuming that the AC power supply Vac is stable, and an error that may occur somewhat may be described in the flicker comparator 124-i to be described later. It can be compensated by hysteresis characteristics. In addition, the period in which the duty average voltage Va_D is calculated may be determined in consideration of noise that may be generated in the AC power source Vac.

A drain of each of the plurality of flicker switches FS1 ˜FSn may be connected to a source of each of the plurality of driving switches DS1 ˜DSn corresponding to each of the plurality of flicker switches FS1 ˜FSn.

The plurality of flicker switch controllers 120-1 to 120-n correspond to each of the plurality of flicker switches FS1 to FSn, and the plurality of flicker switch controllers 120-1 to 120-n as shown in FIG. 6. Any one of 120) may include a flicker reference voltage (122-i), and a flicker comparator (124-i).

The flicker reference voltage generator 122-i may generate the flicker reference voltage Vf-i corresponding to each of the first to nth LED groups 30-1 to 30-n. The flicker reference voltage Vf-i is a reference voltage at which the flicker phenomenon disappears for each of the first to nth LED groups 30-1 to 30-n and may be an experimentally predetermined voltage. That is, when the duty average voltage Va_D-i is higher than the flicker reference voltage Vf-i, there is no flicker in the corresponding LED group, and the duty average voltage Va_D-i is lower than the flicker reference voltage Vf-i. When the flicker occurs on the LED group.

The flicker reference voltage generator 122-i may receive the AC selection signal ACS from the AC selection circuit 70 and generate the flicker reference voltage Vf-i according to the AC selection signal ACS. In other words, a higher level flicker reference voltage Vf-i is generated than when the AC select signal ACS is at high level (for 220V) or when the AC select signal ACS is at low level (for 120V). Can be. Accordingly, an appropriate level of flicker reference voltage Vf-i may be generated when the LED driving circuit 20-1 is for 120V and for 220V, respectively.

The flicker reference voltage Vf-i may increase sequentially as the n-th LED group 30-n corresponds to the n-th LED group 30-1. That is, as i increases, the flicker reference voltage Vf-i increases. However, the scope of the present invention is not limited thereto, and the flicker reference voltage Vf-i may be arbitrarily determined in consideration of characteristics of each LED group.

The flicker comparator 124-i may control a corresponding flicker switch FSi based on a flicker comparison result of comparing the flicker reference voltage Vf-i and the duty average voltage Va_D-i. For example, assuming that each of the plurality of flicker switches FS1 to FSn is implemented with an NMOS transistor, the flicker comparator 124-i may have a duty average voltage Va_D-i higher than the flicker reference voltage Vf-i. The high level may be output, and the low level may be output when the duty average voltage Va_D-i is lower than the flicker reference voltage Vf-i. In addition, the flicker switch controller 120-i is a drive average controller Va-D-i corresponding to each of the drive switch controllers 50-i, and the flicker reference voltage Vf-i and the duty average voltage Va_D-i. ) Can be used to provide flicker comparison results. An operation related to this will be described later with reference to FIGS. 32 and 33.

Here, it is assumed that n is 4 and the flicker reference voltages Vf corresponding to the first LED group 30-1 to the fourth LED group 30-4 are 0.5V, 1V, 1.5V, and 2V, respectively. If the duty average voltage Va_D is 3V, the flicker switches FS1 to FS4 are all turned on so that the first LED group 30-1 to the fourth LED group 30-4 may operate normally. If the duty average voltage Va_D is 0.3V, the flicker switches FS1 to FS4 are all turned off, and thus all of the first LED group 30-1 to the fourth LED group 30-4 may be turned off. If the duty average voltage Va_D is 1.7V, only FS4 of the flicker switches FS1 to FS4 may be turned off, such that the fourth LED group 30-4 may be turned off.

That is, the flicker switching circuit 100-1 may select an LED group having a high probability of occurrence of flicker among the first LED groups 30-1 to 30th n based on the duty average voltage Va_D. By turning it off, the flicker phenomenon which arises by repeating ON / OFF can be prevented.

Flicker comparator 124-i may have hysteresis characteristics. When the flicker comparator 124-i outputs a high level according to this hysteresis characteristic, the duty average voltage Va_D-i for outputting the low level and the flicker comparator 124-i output a low level. The duty average voltage Va_D-i for outputting the high level may be different (eg, the latter duty average voltage may be higher).

This prevents the output of the flicker comparator 124-i from being unstable due to noise that may be included in the flicker reference voltage Vf-i or the duty average voltage Va_D-i, thereby causing the flicker phenomenon to be worse in the corresponding LED group. To do this. In addition, as described above, noise generated by the difference between the calculation time point and the application time point in the duty average detection circuit 110 may also be compensated by the hysteresis characteristics of the flicker comparator 124-i.

As described above, in the absence of the flicker switching circuit 100-1, the fourth LED group may be turned on when the first peak voltage is Vp1, but the fourth LED group may be turned on when the second peak voltage is Vp2. This off state is maintained and flicker occurs.

In FIG. 7B, the LED current I _LED when the flicker switching circuit 100-1 is present is shown, and the flicker reference in which the duty average voltage Va_D corresponds to the third LED group 30-3 is shown. The case of having a value between the voltage Vf and the flicker reference voltage Vf corresponding to the fourth LED group 30-4 is shown. That is, since the flicker phenomenon occurs in the fourth LED group 30-4, the flicker switching circuit 100-1 selectively turns off the flicker switch FS4 corresponding to the fourth LED group 30-4 to flicker. The phenomenon can be prevented.

Therefore, according to the LED driving circuit 20 according to the embodiment of the present invention, the flicker phenomenon can be selectively turned off to reduce the flicker phenomenon.

FIG. 8 is a diagram schematically showing another embodiment of the LED driving circuit 20 shown in FIG. 1. FIG. 9 is a view schematically showing another embodiment of the LED driving circuit 20 shown in FIG. 1. FIG. 10 is a view schematically illustrating another embodiment of the LED driving circuit 20 shown in FIG. 1. FIG. 11 is a diagram illustrating the first driving and flicker controller 60-1 shown in FIG. 10.

1 to 11, another embodiment 20-2 of the LED drive circuit 20 shown in FIG. 8 is one embodiment 20-1 of the LED drive circuit 20 shown in FIG. 3. Unlike the position of each of the plurality of flicker switches FS1 to FSn, the positions of the plurality of flicker switches FS1 to FSn are opposite to the positions of the plurality of drive switches DS1 to DSn respectively. That is, a source of each of the plurality of flicker switches FS1 to FSn may be connected to a drain of each of the plurality of driving switches DS1 to DSn corresponding to each of the plurality of flicker switches FS1 to FSn. The other embodiment 20-2 of the LED driving circuit 20 is different from the operation of the embodiment 20-1 of the LED driving circuit 20 except that only the positions of the plurality of flicker switches FS1 to FSn are changed. Substantially the same.

In another embodiment 20-3 of the LED driving circuit 20 shown in FIG. 9, the drain of each of the plurality of flicker switches FS1 to FSn corresponds to each of the plurality of flicker switches FS1 to FSn. It may be connected to the gate of each of the plurality of driving switches DS1 to DSn. Each of the plurality of flicker switch controllers 120-1 to 120-n included in the flicker control circuit 100-3 has a duty average voltage Va_D lower than the flicker reference voltage Vf corresponding to each LED group. A control signal for turning on each flicker switch FS1 to FSn may be generated.

 When the plurality of flicker switches FS1 to FSn and the plurality of driving switches DS1 to DSn are implemented as NMOS transistors, one embodiment 20-1 of the LED driving circuit 20 shown in FIG. Each of the plurality of flicker switch controllers 120-1 through 120-n may further include an inverter (not shown) in the flicker switch controller 120-i illustrated in FIG. 6 to perform substantially the same operation. .

In another embodiment 20-2 of the LED driving circuit 20 shown in FIG. 10, each of the plurality of flicker switches FS1 to FSn and each of the plurality of driving switches DS1 to DSn are driven one by one. A plurality of drive and flicker switch controllers 60-1 implemented with the flicker switches DFS1 to DFSn, and which control the operation of each of the plurality of drive and flicker switches DFS1 to DFSn. ˜60-n).

Each of the plurality of drive and flicker switch controllers 60-1 to 60-n can have substantially the same configuration and operation, and a first drive and flicker switch controller 60-1 is shown in FIG. 11. The first drive and flicker switch controller 60-1 may include a first drive switch controller 50-1, a first flicker switch controller 120-1, and a first drive switch controller 50-1 and a first flicker. The switch controller 120-1 may further include an operation circuit 62-1 that calculates an output of each of the switch controllers 120-1 to control the first driving and flicker switches DFS1. Hereinafter, an example in which the calculation circuit 62-1 is implemented with an AND gate is described.

Referring to the operation of the first driving and flicker switch controller 60-1, the outputs of the first driving switch controller 50-1 and the first flicker switch controller 120-1 are ANDed so that the first driving and flicker switches are operated. Since the DFS1 is controlled, the actual operation is the same as that of the first drive switch controller 50-1 and the first flicker switch controller 120-1 shown in FIG. 3. However, in FIG. 3, two switches are required for each LED group, whereas in FIG. 10, the same operation is performed using only one switch, which may be advantageous in terms of integration. Depending on the circuit configuration of the drive and flicker switch controllers 60-1 to 60-n, the arithmetic circuit 62-1 may be configured to have the same effect even if it is not an AND gate.

12 is a view schematically showing another embodiment of the LED driving circuit 20 shown in FIG. FIG. 13 is a view schematically showing another embodiment of the LED driving circuit 20 shown in FIG. 1. 14 and 15 are diagrams for describing an operation of still other embodiments of the LED driving circuit 20 shown in FIGS. 12 and 13.

1, 2, and 12 to 15, the flicker control circuits 100-5 and 100-6 shown in FIGS. 12 and 13 are implemented as a bleeder circuit as described above. . The bleeder circuits 100-5 and 100-6 detect a rising edge and a duty average value of the rectified voltage Vrac of the dimming AC voltage to generate a bleeder current. The bleeder circuits 100-5 and 100-6 must flow the bleeder current above the latching current or the holding current required by the dimmer 12.

The flicker control circuit 100-5 in FIG. 12 is a short pulse bleeder circuit 100-5, a short pulse generator 130, and a short pulse switch M1. ) May be included.

The short pulse generator 130 may detect an edge of the rectified voltage Vrac of the dimming AC voltage to generate a short pulse signal SP having a predetermined interval. The short pulse signal SP may have an interval of any high level shorter than a half period of the rectified voltage Vrac of the dimming AC voltage from the time when the edge of the rectified voltage Vrac of the dimming AC voltage is detected. The high level may be a level at which the short pulse switch M1 may be turned on.

The short pulse switch M1 may generate a first current I1, that is, a bleeder current according to the short pulse signal. The first current I1 may satisfy the latching current or the holding current required by the dimmer 12, and prevent the misfire in which the output of the dimmer 12 is turned on and off, thereby preventing flicker. Can be removed

The short pulse generator 130 detects only an edge regardless of the level of the rectified voltage Vrac of the dimming AC voltage and controls the short pulse switch M1 to supply a constant current, so the level of the rectified voltage Vrac of the dimming AC voltage is controlled. It may be advantageous in terms of power consumption than when a current proportional to.

The flicker control circuit 100-6 of FIG. 13 is an active bleeder circuit 100-6 as a duty average detection circuit 110, a duty comparator 140, and an active switch. M2).

The duty average detection circuit 110 may generate the duty average voltage Va_D based on the rectified voltage Vrac of the dimming AC voltage, and the configuration and function are the same as the duty average detection circuit 110 shown in FIG. 4. .

The duty comparator 140 may generate a duty comparison result comparing the duty average voltage Va_D and the bleeder reference voltage Vref_b. For example, when the active switch M2 is implemented as an NMOS transistor, a high level duty comparison result is obtained when the duty average voltage Va_D is lower than the bleeder reference voltage Vref_b, and the duty average voltage Va_D is a bleeder reference voltage. When higher than (Vref_b) it can generate a low level duty comparison result. The high level may be a level at which the active switch M2 may be turned on. That is, the bleeder reference voltage Vref_b is a voltage that is a reference for generating a misfire in the dimmer 12 and may be an experimentally predetermined voltage.

The active switch M2 generates the second current I2, that is, the bleeder current, according to the duty comparison result. That is, the active bleeder circuit 100-6 may generate the second current I2 only at a predetermined duty or less by comparing the duty average voltage Va_D and the bleeder reference voltage Vref_b. Since the role of the second current I2 is substantially the same as that of the first current I2, a detailed description thereof will be omitted.

14 and 15 illustrate the first current I1 and the second current when the duty average voltage Va_D obtained from the rectified voltage Vrac of the dimming AC voltage is lower than and higher than the bleeder reference voltage Vref_b, respectively. I2) is shown, respectively. The first current I1 is a current flowing by the short pulse bleeder circuit 100-5 and the second current I 2 is a current flowing by the active bleeder circuit 100-6.

14 illustrates a bleeder current flowing when the duty average voltage Va_D is lower than the bleeder reference voltage Vref_b. The short pulse bleeder circuit 100 for each rising edge of the rectified voltage Vrac of the dimming AC voltage is shown in FIG. -5) operates so that a first level I1 of a certain level flows for a predetermined period. The first current I1 may flow in the form of a square wave or triangle wave. In addition, since the duty average voltage Va_D is lower than the bleeder reference voltage Vref_b, the duty comparator 140 generates a high level duty comparison result to dimming AC voltage from the rising edge of the rectified voltage Vrac of the dimming AC voltage. The active switch M2 is turned on and the second current I2 flows until one cycle P1 of the rectified voltage Vrac is ended. However, when the rectified voltage Vrac of the dimming AC voltage becomes 0 V in the active switch M2, the second current I2 does not flow because there is no voltage difference between the drain and the source. Accordingly, the first current I1 and the second current I2 are generated to prevent the misfire of the dimmer 12 and thus eliminate flicker.

Next, FIG. 15 illustrates the bleeder current waveform when the average voltage Va_D is higher than the bleeder reference voltage Vref_b. In the case of the short pulse bleeder circuit 100-5, as shown in FIG. 14, the first current I1 having a predetermined level is generated in the form of a square wave or a triangular wave for a predetermined period for each rising edge of the rectified voltage Vrac of the dimming AC voltage. can do. In the case of the active bleeder circuit 100-6, since the duty average voltage Va_D is higher than the bleeder reference voltage Vref_b, the duty comparator 140 generates a low level duty comparison result to determine the rectified voltage of the dimming AC voltage. The active switch M2 is turned off from the rising edge of Vrac until the end of one period P1 of the rectified voltage Vrac of the dimming AC voltage. That is, when the duty average voltage Va_D is higher than the bleeder reference voltage Vref_b, no misfire is generated in the dimmer 12, so that the second current I2 is not generated, thereby reducing unnecessary power consumption.

According to the LED driving circuit 20 according to the embodiment of the present invention, the flicker phenomenon can be removed by properly generating a bleeder current to prevent the misfire of the dimmer 12.

16 to 28 briefly illustrate still other embodiments of the LED driving circuit 20 shown in FIG. 1, respectively.

1 to 28, the flicker control circuits 100-7 to 100-10 shown in FIGS. 16 to 19 respectively illustrate the flicker switching circuits 100-100 shown in FIGS. 3 and 8 to 10, respectively. 1 to 100-4) and the short pulse bleeder circuit 100-5 shown in FIG. 12.

The flicker control circuits 100-11 to 100-14 shown in FIGS. 20 to 23 are shown in FIG. 3 and the flicker switching circuits 100-1 to 100-4 shown in FIGS. 8 to 10, respectively. This is the case using the active bleeder circuit 100-6 shown in FIG. However, the flicker control circuits 100-11 to 100-14 may include only one duty average detection circuit 110, respectively. For example, in the flicker control circuit 100-11, one duty average detection circuit 110 may supply the duty average voltage Va_D to the active comparator 140 and the flicker switch controllers 120-1 to 120-n. .

The flicker control circuits 100-15 to 100-18 shown in FIGS. 23 to 27 are shown in FIG. 3 and the flicker switching circuits 100-1 to 100-4 shown in FIGS. 8 to 10, respectively. Both the short pulse bleeder circuit 100-5 and the active bleeder circuit 100-6 shown in FIG. 13 may be provided.

The flicker control circuit 100-19 shown in FIG. 28 may further include the active bleeder circuit 100-6 shown in FIG. 13 in addition to the short pulse bleeder circuit 100-5 shown in FIG. have.

29 to 31 illustrate exemplary embodiments of the AC selection circuit illustrated in FIG. 1.

1, 3, and 29 to 31, the AC selection circuit 70-1 shown in FIG. 29 is connected to both ends of the first LED group 30-1, and the first to fourth portions. The resistors R1 to R4, the first and second diodes D1 and D2, and the comparator 72 may be included. Resistance values of each of the first to fourth resistors R1 to R4 may be the same, and each of the first and second diodes D1 and D2 may have the same voltage as one series of the first LED group 30-1. Can cause a drop.

The first resistor R1, the first diode D1, and the second resistor R2 are connected in series between the rectified voltage Vrac of the dimming AC voltage Vdac and the ground, and the cathode of the first LED group ( A third resistor R3, a second diode D2, and a fourth resistor R4 may be connected in series between the cathode voltage and the ground. The comparator 72-1 compares the cathode voltage of the first diode D1 with the anode voltage of the second diode D2 and compares the AC selection signal ACS as a result of the flicker switch controller 120-i. ) Can be sent.

When the LED drive circuit 20 is for 220V, the first group of LEDs may consist of three series of LEDs so that the cathode voltage of the first diode D1 is greater than the anode voltage of the second diode D2. Becomes high. Accordingly, the comparator 72-1 may output a high level AC comparison signal ACS.

When the LED drive circuit 20 is for 120V, the first group of LEDs may consist of one or two series LEDs so that the cathode voltage of the first diode D1 is the anode of the second diode D2. Will be lower than the voltage. Accordingly, the comparator 72-1 may output the low level AC comparison signal ACS.

The AC selection circuit 70-2 shown in FIG. 30 may include first and second NMOS transistors N1 and N2 instead of the first and second diodes D1 and D2 of the AC selection circuit 70-1. Can be.

The comparator 72-2 shown in FIG. 30 compares the source voltage of the first NMOS transistor N1 and the drain voltage of the second NMOS transistor N2 with each other to compare the AC selection signal ACS as a result of the flicker switch controller. May transmit to 120-i.

The AC selection circuit 70-2 has only been replaced with the first and second NMOS transistors N1 and N2 of the first and second diodes D1 and D2 of the AC selection circuit 70-1, respectively. It is the same as the AC selection circuit 70-1.

The AC selection circuit 70-3 shown in FIG. 31 may include first and second PMOS transistors P1 and P2 instead of the first and second diodes D1 and D2 of the AC selection circuit 70-1. Can be.

The comparator 72-3 shown in FIG. 31 compares the drain voltage of the first PMOS transistor P1 with the source voltage of the second PMOS transistor P2 and compares the AC selection signal ACS as a result of the flicker switch controller. May transmit to 120-i.

The AC selection circuit 70-3 has only been replaced with the first and second PMOS transistors P1 and P2 of the AC selection circuit 70-1 by the first and second diodes D1 and D2, respectively. It is the same as the AC selection circuit 70-1.

Each of the AC selection circuits 70-1 through 70-3 shown in FIGS. 29 to 31 is only an embodiment of the AC selection circuit 70, and the AC selection circuit 70 includes the first LED group 30-1. By sensing the voltage at both ends, the LED driving circuit 20 can be transformed into various circuits capable of determining whether the LED driving circuit 20 is for 120V or 220V.

32 is a view for explaining the operation of the drive switch controller according to a comparative example of the present invention. 33 is a view for explaining the operation of the drive switch controller according to an embodiment of the present invention.

3 to 6, 32, and 33, unlike the first to n th driving switch controllers 50-1 to 50-n illustrated in FIG. 3, the first to n th flicker switch controllers ( It is assumed that the first to nth drive switch controllers operate regardless of 120-1) (comparative example of the present invention).

In this case, the driving reference voltage Vref_d determines the current and luminance of each of the first to nth LED groups 30-1 to 30-n as a signal for controlling each of the first to nth driving switch controllers. As the driving reference voltage Vref_d increases, the current of each of the first to nth LED groups 30-1 to 30-n increases and the luminance increases.

If the driving reference voltage Vref_d remains constant regardless of the duty average voltage Va_D, the current and luminance of the LED groups 30-1 to 30-n are always maintained even if the duty average voltage Va_D is changed. Will remain constant.

At this time, when the duty average voltage Va_D is changed and the flicker switches FS1 to FSn are turned on and off as a reference, the dimmer is adjusted to turn off the flicker switches FS1 to FSn. In this case, since the corresponding LED group is turned off from the on state, the brightness of the LED bulb decreases drastically. On the contrary, when the flicker switches FS1 to FSn turn on from the off state, the luminance of the corresponding LED group increases rapidly. To improve the quality of LED bulbs, it is necessary to drive LEDs that linearly increase or decrease in brightness rather than abruptly increase or decrease in brightness.

However, each of the first to n-th drive switch controllers 50-1 to 50-n illustrated in FIG. 3 is the first to n-th flicker switch controller 120-1 to 120-n as shown in FIG. 6. ), The comparison result of the duty average voltage Va_D and the flicker comparator 124-i may be received. Each of the first to n-th driving switch controllers 50-1 may control the level of the driving reference voltage Vref_d from the comparison result of the duty average voltage Va_D and the flicker comparator 124-i.

That is, each of the first to nth driving switch controllers 50-1 to 50-n may recognize the point A from the comparison result of the flicker comparator 124-i and the duty average voltage Va_D is less than or equal to the A point. In this case, the driving reference voltage Vref_d may be maintained at 0V. In this case, when the duty average voltage Va_D exceeds the point A, the driving reference voltage Vref_d may be gradually increased at 0V with a constant slope. In addition, when the duty average voltage Va_D exceeds the A point and exceeds the B point, a constant driving reference voltage Vref_d may be maintained. Point B may be arbitrarily determined based on power consumption and the like.

Therefore, according to the first to n-th driving switch controllers 50-1 to 50-n illustrated in FIG. 3, the first to n-th LED groups corresponding to the flicker switches FS1 to FSn at the point A ( 30-1 ~ 30-n) The brightness of each LED will gradually increase the driving reference voltage (Vref_d) at 0V with a constant slope when the duty average voltage (Va_D) exceeds the point A, so even if the dimmer is increased or decreased, the LED bulb It is possible to eliminate the phenomenon that the brightness of the camera suddenly changes and the brightness increases or decreases smoothly.

Although the present invention has been described with reference to one embodiment shown in the drawings, this is merely exemplary, and those skilled in the art will understand that various modifications and equivalent other embodiments are possible therefrom. Therefore, the true technical protection scope of the present invention will be defined by the technical spirit of the appended claims.

The invention can be applied to an apparatus for controlling LED lighting.

Claims (31)

In the AC direct type LED driving circuit, An LED array comprising first to nth (n is an integer greater than or equal to) LED groups connected in series; A control unit including a plurality of drive switches connected to the LED array and a drive switch controller for selectively opening and closing the drive switches; An LED current control circuit configured to adjust a current flowing in the first to nth LED groups; And The duty average voltage of the rectified voltage of the dimming alternating current (AC) voltage is compared with the flicker reference voltage to selectively turn on or off each of the first to nth LED groups. LED drive circuit including flicker switching circuit. The method of claim 1, The flicker switching circuit A duty average detection circuit configured to generate the duty average voltage based on the rectified voltage of the dimming alternating voltage; A plurality of flicker switches for selectively turning on or off each of the first to nth LED groups; And And a flicker switch controller configured to control the plurality of flicker switches based on the flicker reference voltage and the duty average voltage corresponding to each of the first to nth LED groups. The method of claim 2, The duty average detection circuit A duty detector configured to generate a duty detection signal by comparing the rectified voltage of the dimming AC voltage with a duty reference voltage; And And an average voltage generator for generating the duty average voltage corresponding to the average level of the duty detection signal. The method of claim 2, The flicker switch controller A flicker reference voltage generator for generating the flicker reference voltage corresponding to each of the first to nth LED groups; And And a flicker comparator configured to control the plurality of flicker switches based on a flicker comparison result of comparing the flicker reference voltage and the duty average voltage. The method of claim 1, And an AC selection circuit for sensing the voltage across the first LED group to adjust the flicker reference voltage. The method of claim 1, The drive switch controller further includes a circuit for linearly adjusting current and brightness of the LED group corresponding to the drive switch controller based on the duty average voltage and the flicker comparison result. The method of claim 4, wherein The flicker comparator has hysteresis characteristics. The method of claim 4, wherein The flicker reference voltage increases sequentially as the first LED group corresponds to the nth LED group. The method of claim 2, And a drain of each of the plurality of flicker switches is connected to a source of each of the plurality of drive switches corresponding to each of the plurality of flicker switches. The method of claim 2, And a source of each of the plurality of flicker switches is connected to a drain of each of the plurality of drive switches corresponding to each of the plurality of flicker switches. The method of claim 2, And a drain of each of the plurality of flicker switches is connected to a gate of each of the plurality of drive switches corresponding to each of the plurality of flicker switches. The method of claim 2, Each of the plurality of flicker switches and each of the plurality of driving switches is implemented as a single switch, The flicker control circuit further includes an arithmetic circuit for calculating the flicker comparison result and the output of the drive switch controller to control the one switch. In the AC direct type LED driving circuit, An LED array comprising first to nth (n is an integer greater than or equal to) LED groups connected in series; A control unit including a plurality of drive switches connected to the LED array and a drive switch controller for selectively opening and closing the drive switches; An LED current control circuit configured to adjust a current flowing in the first to nth LED groups; And An LED drive circuit comprising a bleeder circuit that generates a constant level of bleeder current in accordance with a rectified voltage of a dimming alternating current (AC) voltage. The method of claim 13, The bleeder circuit is a short pulse bleeder circuit, A short pulse generator configured to detect a rising edge of the rectified voltage of the dimming AC voltage and generate a short pulse signal having a predetermined interval; And And a short pulse switch configured to generate the bleeder current according to the short pulse signal. The method of claim 13, The bleeder circuit is an active bleeder circuit, A duty average detection circuit configured to generate a duty average voltage based on the rectified voltage of the dimming AC voltage; A duty comparator configured to generate a duty comparison result comparing the duty average voltage and a bleeder reference voltage; And And an active switch configured to generate the bleeder current according to the duty comparison result. The method of claim 15, The duty average detection circuit A duty detector configured to generate a duty detection signal by comparing the rectified voltage of the dimming AC voltage with a duty reference voltage; And And an average voltage generator for generating the duty average voltage corresponding to the average level of the duty detection signal. In the AC direct type LED driving circuit, An LED array comprising first to nth (n is an integer greater than or equal to) LED groups connected in series; A control unit including a plurality of drive switches connected to the LED array and a drive switch controller for selectively opening and closing the drive switches; And An LED current control circuit configured to adjust a current flowing in the first to nth LED groups; And The duty average voltage of the rectified voltage of the dimming alternating current (AC) voltage is compared with the flicker reference voltage to selectively turn on or off each of the first to nth LED groups. Flicker controlling circuit including a flicker switching circuit and a bleeder circuit that detects the rectified voltage rising edge or the duty average voltage of the dimming AC voltage to generate a constant level of bleeder current. LED drive circuit comprising a circuit). The method of claim 17, The bleeder circuit is a short pulse bleeder circuit, A short pulse generator configured to detect an edge of the rectified voltage of the dimming AC voltage and generate a short pulse signal having a predetermined interval; And And a short pulse switch configured to generate the bleeder current according to the short pulse signal. The method of claim 17, The bleeder circuit is an active bleeder circuit, A duty average detection circuit configured to generate a duty average voltage based on the rectified voltage of the dimming AC voltage; A duty comparator configured to generate a duty comparison result comparing the duty average voltage and a bleeder reference voltage; And And an active switch to generate the latching current or the holding current according to the duty comparison result. The method of claim 17, The flicker switching circuit A duty average detection circuit configured to generate the duty average voltage based on the rectified voltage of the dimming alternating voltage; A plurality of flicker switches for selectively turning on or off each of the first to nth LED groups; And And a flicker switch controller configured to control the plurality of flicker switches based on the flicker reference voltage and the duty average voltage corresponding to each of the first to nth LED groups. The method of claim 20, The duty average detection circuit A duty detector configured to generate a duty detection signal by comparing the rectified voltage of the dimming AC voltage with a duty reference voltage; And And an average voltage generator for generating the duty average voltage corresponding to the average level of the duty detection signal. The method of claim 20, The flicker switch controller A flicker reference voltage generator for generating the flicker reference voltage corresponding to each of the first to nth LED groups; And And a flicker comparator configured to control the plurality of flicker switches based on a flicker comparison result of comparing the flicker reference voltage and the duty average voltage. The method of claim 22, And an AC selection circuit for sensing the voltage across the first LED group to adjust the flicker reference voltage. The method of claim 22, The drive switch controller further includes a circuit for linearly adjusting the brightness of the LED group corresponding to the drive switch controller based on the duty average voltage and the flicker comparison result. The method of claim 22, The flicker comparator has hysteresis characteristics. The method of claim 22, The flicker reference voltage increases sequentially as the first LED group corresponds to the nth LED group. The method of claim 20, And a drain of each of the plurality of flicker switches is connected to a source of each of the plurality of drive switches corresponding to each of the plurality of flicker switches. The method of claim 20, And a source of each of the plurality of flicker switches is connected to a drain of each of the plurality of drive switches corresponding to each of the plurality of flicker switches. The method of claim 20, And a drain of each of the plurality of flicker switches is connected to a gate of each of the plurality of drive switches corresponding to each of the plurality of flicker switches. The method of claim 20, Each of the plurality of flicker switches and each of the plurality of driving switches is implemented as a single switch, The flicker switching circuit further includes an arithmetic circuit for controlling the one switch by calculating the flicker comparison result and the output of the driving switch controller. The method of claim 17, And the flicker control circuit includes only one duty average detection circuit that generates the duty average voltage based on the rectified voltage of the dimming alternating voltage.

Images