KR20130103263A - Dimmable led lighting device - Google Patents

Abstract

PURPOSE: A dimmable LED device is provided to turn on all LED blocks by attenuating the current quality of a current limit device with a measured phase quantity even though a dimming operation is performed over 50%. CONSTITUTION: A rectifying circuit converts an AC voltage into a DC voltage by rectifying the AC voltage. An LED block is composed of one or more LEDs. A switch block is composed of switches which bypass a current which flows in each LED block. A current limit device limits the current which is supplied to the LED block. A controller controls the switch block and the current limit device. The controller controls the current quantity of the current limit device with a measured phase quantity.

Description

Dimmable LED Lighting Device

The present invention relates to a lighting device using an LED (light emitting diode),

More particularly, the present invention relates to an LED lighting device capable of dimming.

Light-emitting diodes (LEDs) are all-optical semiconductor devices that emit light when current flows. They are widely used in display backlights, and the development of technology has made them more efficient than conventional incandescent and fluorescent lamps. I'm going.

Among the methods of driving the LED, a number of methods for driving the LED lamps with AC voltage (hereinafter, "LED direct current driving method") are introduced, including the inventors' patent No. 10-1110380.

Hereinafter, a problem of dimming according to the related art will be described with reference to FIGS. 1 to 3.

Conventional Technology Example 1

The conventional LED lighting apparatus according to FIG. 1 includes an AC power supply 910 for supplying an AC voltage, a rectifier circuit 940 for converting an AC voltage supplied from the AC power supply 910 into a DC rectified voltage Vrect, Composed of a first light emitting block 871, a second light emitting block 872, a third light emitting block 873 and a fourth light emitting block 874 driven by a rectified voltage Vrect, which is an output of the rectifier circuit 940. do.

In addition, the conventional LED lighting device is a parallel switch block (first switch (SW1), second switch (SW2), the first switch to adjust the number of light-emitting blocks by changing the current path in accordance with the instantaneous voltage of the AC power source) Third switch SW3 and fourth switch SW4] and a controller 942.

 In addition, the conventional LED lighting apparatus, the first current source (I1), the second current source (I2) which is a current source (or "current limiting device") for limiting the current flowing through the first to fourth light emitting blocks. ), A third current source I3 and a fourth current source I4.

Representative examples of the configuration may include Patent No. 10-0942234 and Patent No. 10-0997050, and the method of operation thereof is described in detail in the above patents, and thus will be omitted for convenience of description.

In the conventional circuit of FIG. 1, the controller 942 controls the parallel switch block such that only one switch of the first switch SW1 to the fourth switch SW4 is turned on and the other is always shut off.

When the first switch SW1 is turned on so that the first light emitting block is turned on, the power supply current is limited by the current limiting device I1 to be 5 mA. In addition, when the second switch SW1 is turned on so that the first light emitting block 871 and the second light emitting block 872 are turned on, the power supply current is limited by the current limiting device I2 to be (10 mA). In the same manner, when the third switch SW3 is turned on, the first light emitting blocks 871 to 373 turn on and the power supply current becomes (15 mA). When the switch SW4 is turned on, the first to fourth light emitting blocks 871 to 874 are turned on, and the power supply current is 20 mA. If this is shown for one period of the rectified voltage, it becomes the current waveform 710 of FIG. That is, a stepped wave-type power current appears.

Figure 3 shows the circuit of the inventor's patent 10-1110380.

The main item related to the present invention is that the controller 942 is in phase with the AC voltage 910 and the shape of the sinusoidal control signal Csin controls the current source CS so that the power supply current waveform 710 of FIG. 2. It appears in sinusoidal form as At this time, the operation principle of the controller 942 to control the switch (S11) to the switch (S14) is described in detail in the Patent No. 10-1110380, and will be omitted for convenience of description.

Hereinafter, a problem of the conventional LED lighting apparatus will be described with reference to FIGS. 4 to 7.

In FIG. 4, the voltage waveform 310 illustrates an AC power supply voltage in which a part of an AC voltage phase is cut by using an AC power supply phase control device (eg, triac).

When the phase of the AC voltage is removed between 0 degrees and 90 degrees, a power supply current appears as shown in the stepped wave waveform 311 or the sinusoidal wave waveform 311A of FIG. At this time, all of the light emitting blocks are turned on at least once in each rectifying cycle.

When the AC voltage is removed by 90 degrees, the power supply current appears as in the stepped wave waveform 312 or the sinusoidal wave waveform 312A of FIG. 6. At this time, all of the light emitting blocks are turned on at least once in each rectifying cycle.

However, when the amount of the phase of the AC voltage between 90 degrees and 180 degrees is removed, a power supply current appears as shown in the step wave waveform 313 or the sine wave waveform 313A of FIG. At this time, a light emitting block that is not turned on even once in each rectifying cycle is generated. That is, if dimming is performed by more than 50% in the LED lighting apparatus made in the related art, there is a problem in that the brightness deviation occurs in the LED lighting apparatus due to the light emitting block which does not light in the rectified voltage 1 cycle. (50% dimming here means that the brightness of the LED luminaire is 1/2)

Patent No. 10-1110380 Patent No. 10-0942234 Patent number 10-0971757 Patent No. 10-0997050 Patent No. 10-0979432

SUMMARY OF THE INVENTION The present invention has been made to solve the conventional problems, and in a dimming method in which a part of an AC power phase is removed using an AC power phase control element, even if dimming is performed at least 50%, one cycle of rectified voltage is achieved. All light emitting blocks are turned on within one cycle to provide an LED lighting device having a smaller brightness deviation than the prior art.

To this end, the dimmable LED lighting device according to the present invention, the rectifier circuit for rectifying the AC voltage to convert the rectified voltage of direct current; An LED light emitting block composed of one or more LEDs; A load (n ≧ 1 natural number) in which the LED light emitting blocks are connected in series n; A switch block comprising a switch for bypassing current flowing through each light emitting block of the load; A current limiting device for limiting a current supplied to the LED light emitting block; And a controller for controlling the switch block and the current limiting device.

The controller may further include a function of measuring a phase Delta removed when an AC voltage is partially cut and supplied by a phase controller; (Delta Phase) to adjust the amount of current in the current limiting device; Even if the dimming is 50% or more, all LED light-emitting blocks are turned on in each rectifying cycle.

In addition, the dimmable LED lighting device according to the present invention, the controller controls the current limiting device with a sinusoidal signal in phase with the AC voltage phase;

In addition, the dimmable LED lighting device according to the present invention, the controller controls the current limiting device in the form of a staircase wave;

In addition, the dimmable LED lighting apparatus according to the present invention adds Pulse Width Modulation (PWM) control to the current waveform before dimming so that the waveform formed by the average current values of one cycle of PWM becomes a dimming current waveform. Dimmable LED lighting device further comprising a PWM control function;

The conventional dimmable LED lighting device is a dimming method in which a part of an AC power phase is cut by using an AC power phase control element. Although there is a light emitting block that does not light up in the LED lighting device, the brightness deviation occurred, but the dimmable lighting device according to the present invention is all light emitting blocks are turned on is provided with an LED lighting device having a smaller brightness deviation than the prior art It works.

1 is a circuit diagram of a conventional LED lighting device.
2 is a power supply current waveform of the LED lighting apparatus according to the prior art.
3 is a view showing another conventional LED lighting device.
4 is a power supply current waveform when dimming is used as a phase removing method.
5 is an example of a power supply current waveform when dimming is performed with a phase removal amount of 0 degrees to 90 degrees.
6 is a power supply current waveform when dimming is performed with a phase removal amount of 90 degrees.
7 is an example of the power supply current waveform when dimming is performed with a phase removal amount of 90 degrees to 80 degrees.
8 is a dimmable LED lighting device circuit according to the present invention.
9 is a power supply current waveform when dimming acceleration coefficient = 1.
FIG. 10 shows the relationship between the phase removal amount and the dimming amount when the dimming acceleration coefficient = 1;
10 is a power supply current waveform when dimming acceleration coefficient = 3.
11 shows the relationship between the amount of phase removal and the amount of dimming when dimming acceleration coefficient = 3;

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In this case, it should be noted that like elements are denoted by like reference numerals as much as possible.

In addition, the terms or words used in the specification and claims described below should not be construed as being limited to the conventional or dictionary meanings, but should be construed as meanings and concepts corresponding to the technical spirit of the present invention. And the detailed description of known structures and functions that are determined to unnecessarily obscure the subject matter of the present invention will be omitted.

In the conventional LED lighting apparatus that removes the power supply voltage phase, the current flowing through the LED is kept the same, and only the removed power supply voltage phase is dimmed. However, in the present invention, the concept of "dimming acceleration coefficient" is introduced to more actively dimming. That is, the amount of phase removed is measured, and the amount of current flowing through the LED lighting apparatus is attenuated in proportion to the amount of phase removed, thereby dimming more aggressively.

<Preferred Circuit Example to the Present Invention>

Hereinafter, an example of a circuit preferable for the present invention will be described with reference to FIG. 8.

First, the circuit configuration of FIG. 8 will be described. An AC power source 1, a rectifying circuit 2 for rectifying the AC input voltage and converting it into a DC rectified voltage, a first LED light emitting block 11 including a plurality of LEDs, The second LED light emitting block 12, the third light emitting block 13 and the fourth light emitting block (14).

It also includes a current source (or " current limiting device ") CS2 for limiting the current supplied to the LED light emitting block. In this case, the power supply current waveform by the current limiting device is preferably a step wave. And it is more preferable that the power supply current waveform is a sine wave.

And, it may include one or more switch blocks that can adjust the number of lighting blocks by changing the flow of current flowing through the sub light emitting block. It is of course preferable to include a controller 4 for controlling the switch.

The forward lighting switch block SA, which lights up sequentially from the front to the back, may include a first forward switch SA_1, a second forward switch SA_2, and a third forward switch SA_3. In addition, the reverse-lighting switch block SB, which is sequentially turned on from the back, may be configured of the first reverse switch SB_1, the second reverse switch SB_2, and the third reverse switch SB_3.

If only one switch block of either the forward lit switch block SA or the reverse lit switch block SB is provided, and the lights are turned on, each switch operates on the same principle as the prior art shown in FIG. do.

 Both switch blocks are provided, and in the case of lighting, the inside of each switch block operates on the same principle as the prior art. At this time, it is preferable that the controller 4 activates the forward-lighting switch block SA and the reverse-lighting switch block SB alternately.

That is, the first example of the switch block activation is a case in which the switch block SA operates between 0 degrees and 180 degrees of the input voltage phase, and the switch block SB operates between 180 degrees and 360 degrees of the input voltage phase.

A second example of switch block activation is to perform switch block SA and switch block SB activation at predetermined intervals shorter than the rectification cycle.

Since the lighting method using two switch blocks is a form of a specific embodiment of the present inventors patent No. 10-1110380, description of the operation method is omitted for convenience of description.

In addition, the method of constructing the LED light emitting block and the method of configuring the switch block are also well-known technologies described in detail in the above Patent Nos. 10-1110380 and the prior art documents, and thus are omitted for convenience of description.

Referring to the eight circuits from the viewpoint of the present invention, 1) it is preferable that the controller measures whether there is a phase cut in the AC input voltage, and if so, the amount of the removed phase. That is, when the phase of the AC voltage is partially removed by using an AC phase control element such as TRIAC, the removal amount is measured. And 2) the controller calculates the current regulation control amount of the current limiting device CS2 based on the measured Delta phase, and controls the current source CS2 by the calculated current regulation control amount.

Example 1 Dimming Acceleration Factor = 1.0

Hereinafter, a preferred example of the present invention will be described with reference to FIGS. 9 to 10.

First, a method for calculating the control amount of the current limiting device CS2 based on the removal phase amount measured by the controller 4 will be described.

First, the necessary terms are defined as follows.

1) Im: Instantaneous maximum current source (CS2) current when not dimming.

2) Idim: Instantaneous maximum current source (CS2) current in dimming.

3) alpha: dimming acceleration coefficient (real).

4) dPhase: Delta phase of AC input voltage.

The control input signal Csin of the current limiting device CS2 is calculated as shown in Equation (1).

Csin = Idim x sin (Power Voltage Phase) --- (Equation 1)

The instantaneous maximum current Idim at dimming is calculated by Equation 2.

Idim = [(90-dPhase x alpha) / 90] x Im --- (Equation 2)

In the first embodiment of the present invention, the dimming acceleration coefficient is 1.0.

First, when the removal phase amount dPhase is 0 degrees, Equation 2 becomes Idim = Im. That is, in case of dimming 0%, instantaneous maximum current source current Idim is equal to instantaneous maximum current source current Im when not dimming.

When the removal phase amount dPhase is 89.9 degrees, Equation (2) is Idim = 0.1 / 90 x Im. When dimming, the instantaneous maximum all-current current Idim becomes 1/900 of the instantaneous maximum current Im when dimming. Assuming that the switch for determining the number of series of LED light-emitting blocks is changed at the same time (power supply voltage phase) as before dimming, and the brightness of the LED is proportional to the current, the brightness of the LED lighting device is proportional to the amount of power supply current. In other words, "one hundredth of the brightness before dimming is 100% dimming."

 In reality, if you want to 100% dimming, you can turn off the power switch, so from the point of view of a commercial product, the maximum dimming will be suitable between 80% and 95%.

If the removal phase amount dPhase is 45 degrees (for example, the AC phase control element removes 180 degrees from the voltage phase 135 degrees) (Equation 2), Idim = 1/2 x Im. When the instantaneous current value for the power supply voltage phase is shown for the voltage phase, it may be represented by the waveform 45A of FIG. 9. In other words, the current limiting device (CS2) is limited to the sinusoidal wave of Idim = 1/2 x Im from 0 to 135 degrees in voltage phase, and the waveform from which current is removed by the AC phase control element from 135 to 180 degrees ( 45A).

In FIG. 9, the dimming current waveform 15A is a case in which the input voltage is removed by a phase of 15 degrees, the dimming current waveform 75A is in a phase of 75 degrees, and the dimming current waveform 85A is in a case of removing a phase of 85 degrees, respectively. It is shown.

The current attenuation curve A1 of FIG. 10 is obtained by: 1) obtaining the total dimming power current amount of the cycle with the rectified voltage as described above, changing the removal phase amount from 0 degree to 85 degree in 5 degree steps; and 2) removing phase amount. This is obtained by dividing by the total current source current (a cycle of rectified voltage) in the case of 0 degrees and 3) multiplying by 90 to normalize (ie, normalizing to 90) (the horizontal axis is the removal phase amount and the vertical axis is the normalized current source current amount).

And the dimming amount DS1 of FIG. 10 is calculated | required by (3). (Horizontal axis is the removal phase, vertical axis is%).

Dimming amount = [(90- normalized current amount) / 90] x 100 --- (Equation 3)

Here, if the linear regression equation of the normalized current amount A1 is obtained and the correlation coefficient (R-squared value) is calculated, it is 0.995. That is, in practice, the removal phase amount and the dimming amount may be viewed as linearly proportional.

In conclusion, referring to FIG. 10 from the viewpoint of the present invention, in the dimming method in which a phase cut of a part of an AC power source is removed using an AC power phase control element, even if dimming is performed at least 50%, a cycle of rectified voltage 1 is achieved. All light emitting blocks are turned on within one cycle, and thus, an LED lighting device having a smaller brightness deviation than the prior art is disclosed.

In the present embodiment, the current flows in the dimming current waveform 45A where 50% of the dimming is performed in the vicinity of the voltage phase of 0 degrees. In an actual circuit, it is natural that no current flows below the threshold voltage of the first light emitting block (for example, the first light emitting block).

In the present embodiment, the phase removal is performed after the tailing is performed at 90 degrees, and the phase removal may be performed before the leading edge is removed by 90 degrees.

In the present embodiment, the case in which the current waveform before dimming is a sine wave is described as an example, but the concept of the present invention can be applied to the case of a staircase wave.

In addition, the dimming current waveforms 15A, 45A, 75A, 85A have been described as instantaneous currents implemented by the controller 4 controlling the current limiting device CS2. However, the current waveforms 15A to 85A may be viewed as average current waveforms by pulse width modulation (PWM). That is, PWM control is added to the current waveform before dimming so that the waveform formed by the average current values of the PWM one cycle becomes the dimming current waveform 15A to the dimming current waveform 85A.

At this time, the PWM duty may be calculated by Equation 4.

Iduty = [(90-dPhase x alpha) / 90] x 100 --- (Equation 4)

Here, Iduty is the duty of PWM control signal applied to one period of rectified voltage and unit is%. dPhase is the removal phase of AC input voltage and alpha is the dimming acceleration factor. At this time, it is obvious that the PWM frequency must be higher than the rectified frequency which is twice the power frequency.

As a specific PWM implementation method, a switch (not shown) connected in series with the current limiting device may be provided and implemented by applying a PWM control signal to the control terminal of the series switch. As another implementation method, the current limiting device CS2 may be provided with an output enable / disable terminal and a PWM control signal may be applied to the enable / disable terminal.

In the above, the embodiment for the case where the dimming acceleration coefficient is set to 1.0 has been described in detail.

Example 2: Dimming Acceleration Coefficient = 3.0

The second embodiment of the present invention uses the same formula as the first embodiment of the present invention and sets the dimming acceleration coefficient to 3.0.

Fig. 11 is a view corresponding to Fig. 9, which is the first embodiment (the horizontal axis is the removal phase amount and the vertical axis is the normalized amount of power current). The current waveform 0B is a case where the removal phase amount is 0, the current waveform 10B is a case where the removal phase amount is 10 degrees, and the current waveform 28B is a case where the removal phase amount is 28 degrees, respectively.

12 is a diagram corresponding to FIG. 10, which is the first embodiment. First, the current attenuation curve A3 shows that the maximum dimming is provided before the removal phase amount is 30 degrees (the horizontal axis is the removal phase amount and the vertical axis is the normalized power current amount). The dimming amount is represented by a curve DS3 (where the vertical axis is%).

When the linear regression equation of the normalized current amount A3 is obtained and the correlation coefficient (R-squared value) is calculated, it is 0.999. In other words, the removal phase amount and the dimming amount may be viewed as a linear relationship in practical use.

Referring to FIG. 12 from the viewpoint of the present invention, in the dimming method of removing a part of the AC power phase by using an AC power phase control element, even if dimming is performed at 50% or more, one cycle of rectified voltage (one cycle) All the light emitting blocks are turned on within the LED is disclosed an LED lighting device having a smaller brightness deviation than the prior art.

In the above, the case in which the current limiting device limits the current to the sine wave has been described.

While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. Therefore, the embodiments of the present invention disclosed in the specification and drawings are merely to illustrate the technical details of the present invention, and to present specific examples to aid the understanding of the present invention, and are not intended to limit the scope of the present invention.

1,910 AC power supply 2,940 rectifier circuit
I1, I2, I3, I4 Current Source CS2 Current Source
710 Stair Wave Power Current Waveform 710A Sine Wave Power Current Waveform
310 Power Supply Current Waveform by Phase Controlled Dimming
311,321,331 LED Light Block Current Waveform by Phase Control Dimming (Stair Wave)
311A, 321A, 331A LED Light Block Current Waveform by Phase Control Dimming (Sine Wave)
SA, SB Switch Block

Claims (4)

In an LED lighting device,
A rectifier circuit rectifying the AC voltage and converting the rectified voltage into a DC rectified voltage;
An LED light emitting block composed of one or more LEDs;
A load (n ≧ 1 natural number) in which the LED light emitting blocks are connected in series n;
A switch block comprising a switch for bypassing current flowing through each light emitting block of the load;
A current limiting device for limiting a current supplied to the LED light emitting block;
And a controller for controlling the switch block and the current limiting device.

The controller further has a function of measuring a phase of the removed Delta when the alternating voltage is supplied with a phase cut by the phase controller;
The controller adjusts the amount of current in the current limiting device using the measured Delta Phase;
Dimmable LED lighting device, characterized in that all LED light-emitting blocks turn on at each rectification cycle even if dimming is more than 50% The method of claim 1,
And the controller controls the current limiting device with a sinusoidal signal in phase with an alternating voltage phase. The method of claim 1,
And the controller controls the current limiting device in the form of a staircase wave. 4. The method according to any one of claims 2 to 3,
Adding a PWM (Pulse Width Modulation) control to the current waveform before dimming, further comprising a PWM control function so that the waveform formed by the average current values of one cycle of PWM becomes a dimming current waveform; LED lighting available.

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