KR20140107837A - Led lighting system and control circuit thereof - Google Patents

Abstract

In the present invention, disclosed are an LED lamp device and a control circuit thereof. The LED lamp device includes a power supply unit which supplies a rectified voltage by converting utility power, a light source in which a plurality of LED channels are serially arranged to successively emit light according to the rectified voltage, and a current control circuit which includes a plurality of switching circuits which provide current paths for the LED channels, and controls the emission of the light source by switching the current path.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a light emitting diode (LED)

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a light emitting diode lighting apparatus, and more particularly, to a light emitting diode lighting apparatus and its control circuit which emit light in an alternating direct manner.

In order to save energy, development of lighting technology using light emitting diode (LED) as a light source is continuously being carried out.

In particular, high brightness light emitting diodes have the advantage of differentiating them from other light sources in various factors such as energy consumption, lifetime and light quality.

However, an illumination device using a light emitting diode as a light source has a problem in that a lot of additional circuit is required due to characteristics of a light emitting diode driven by an electric current.

An example developed to solve the above problem is an AC direct type illumination device.

The AC direct light emitting diode lighting device drives a light emitting diode by generating a rectified voltage from a commercial AC power source. Since a rectified voltage is directly used as an input voltage without using an inductor and a capacitor, a characteristic of a good power factor have.

An example of the above-described direct current type light emitting diode device is disclosed in Korean Patent Registration No. 10-1128680.

A general AC direct-type light-emitting diode lighting device has a configuration for emitting or extinguishing light-emitting diode channels in order to realize a dimming function. The dimming function is generally implemented by including a comparator for determining the level of the rectified voltage and performing on-off.

An AC direct-lighting LED lighting apparatus uses a rectified voltage obtained by rectifying a commercial power source having an AC voltage.

The commercial power source includes characteristics on the transmission system or noise components due to various environments.

The noise component may affect the operation of the comparator formed inside the light emitting diode lighting device, and as a result, acts as a factor to destabilize the dimming function of the light emitting diode lighting device.

The comparator is mounted as a component for driving the light-emitting diode channel. Therefore, when the input voltage, which is compared with the reference voltage in the comparator, reaches a level at which the light emitting diode channel is turned on and off in a state of being unstable by the noise component, the output signal of the comparator becomes unstable due to the noise component of the rectified voltage. By the output signal of the unstable comparator, the light emitting diode channel repeats the light emission and the extinction, thereby performing a flickering malfunction.

As described above, in the conventional LED lighting apparatus of the direct current type having the dimming function, when the input voltage of the comparator reaches a specific phase angle near the switching voltage due to the noise component on the rectified voltage, a blinking phenomenon occurs .

It is an object of the present invention to provide a light emitting diode lighting device capable of eliminating a flickering phenomenon occurring at the time when a light emitting state of an LED channel is switched by a noise component on a rectified voltage in an AC direct light emitting diode lighting device having a dimming function, And a control circuit.

According to an aspect of the present invention, there is provided a light emitting diode (LED) lighting apparatus comprising: a power supply unit for providing a rectified voltage obtained by converting a commercial power supply; A light source in which a plurality of light emitting diode channels sequentially emit light in accordance with the rectified voltage; And a plurality of switching circuits for providing a current path to the light emitting diode channels, wherein each of the switching circuits includes a rising reference voltage corresponding to the rise of the rectified voltage and a falling reference voltage corresponding to the falling of the rectified voltage And a current control circuit for controlling the light emission of the light source by switching the current path according to a comparison result between the sensing voltage formed by the current flowing in the current path and the rising or falling reference voltage, do.

The control circuit of the light emitting diode lighting device for controlling the light source in which a plurality of light emitting diode channels are arranged in series according to application of the rectified voltage according to the present invention includes a plurality of light emitting diodes Wherein each of the switching circuits provides a rising reference voltage corresponding to the rise of the rectified voltage and a falling reference voltage corresponding to the falling of the rectified voltage and a sensing voltage generated by the current flowing through the current path, And the current path is switched according to the comparison result of the rising or falling reference voltage to control the light emission of the light source.

Accordingly, the switching for controlling the light emission of the light emitting diode channels can be stably realized, thereby eliminating the unstable flickering of the light emitting diode channel due to the noise component on the rectified voltage, It is possible to receive a voltage (commercial power) or to perform a dimming function with an external dimmer stably.

In particular, in the case of control of the output voltage for varying the illuminance using the dimmer, the output voltage may be located at the switching boundary voltage between the light-emitting diode channels. In this case, the switching state between the light-emitting diode channels can be alternated according to the level of the unstable voltage of the rectified voltage. At this time, an unstable flickering may occur, and flickering can be eliminated by the present invention.

1 is a circuit diagram showing a preferred embodiment of a light emitting diode lighting device according to the present invention.
2 is a circuit diagram of a comparison circuit for explaining hysteresis characteristics;
Fig. 3 is a waveform diagram for explaining the operation characteristics of the comparison circuit of Fig. 2 due to the hysteresis characteristic in a state where the rectified voltage is raised. Fig.
Fig. 4 is a waveform diagram for explaining the operation characteristics of the comparison circuit of Fig. 2 due to the hysteresis characteristic in a state where the rectified voltage is lowered. Fig.
5 is a waveform diagram for explaining the operation of the embodiment of FIG.
6 is a circuit diagram showing another embodiment according to the present invention.
7 is a circuit diagram showing still another embodiment according to the present invention.
8 is a waveform diagram illustrating a state in which an embodiment according to the present invention is applied to control of an output voltage for varying illuminance using a dimmer.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. It is to be understood that the terminology used herein is for the purpose of description and should not be interpreted as limiting the scope of the present invention.

The embodiments described in the present specification and the configurations shown in the drawings are preferred embodiments of the present invention and are not intended to represent all of the technical ideas of the present invention and thus various equivalents and modifications Can be.

An embodiment of a light emitting diode illumination device according to the present invention is implemented in an AC direct method and is disclosed to implement control by applying a change in sensing current according to a rectified voltage to a rising or falling reference voltage corresponding to a change in rectified voltage. That is, according to the embodiment of the present invention, the reference voltage is changed by the hysteresis characteristic, that is, the hysteresis voltage (referred to as 'hysteresis voltage' for ease of explanation in the description of the embodiment of the present invention) The light emission of the light emitting diode channels is controlled. Accordingly, the plurality of LED channels connected in series can be controlled in the light emitting state without being affected by the noise component and without flickering.

Referring to FIG. 1, an embodiment according to the present invention includes three light emitting diode channels (LED1 to LED3), and includes a power source, a light source 12, and a current control circuit 14.

The power supply unit includes a rectifying circuit 10 that rectifies the AC power and outputs it as a rectified voltage and rectifies the AC power supply VAC having the AC voltage and the AC power VAC to output the rectified voltage. Here, the AC power source (VAC) may be a commercial power source.

The rectifying circuit 10 outputs a rectified voltage so as to have a full-wave rectified waveform of an alternating-current voltage having a sinusoidal waveform of the alternating-current power supply VAC. Therefore, the rectified voltage has a ripple component in which the voltage level rises and falls by a half cycle of the commercial AC voltage.

The light source 12 includes three light emitting diode channels LED1, LED2, and LED3 connected in series, and each of the three light emitting diode channels LED1, LED2, and LED3 includes one or more series-connected light emitting diodes . The number of light-emitting diode channels included in the light source may be varied according to the intention of the manufacturer.

Each of the light emitting diode channels LED1, LED2, and LED3 emits light in a state in which a rectified voltage is applied and in a state in which a current path is formed by the current control circuit 14.

In the embodiment according to the present invention, the initial state of each of the switching circuits 30_1, 30_2, and 30_2 included in the current control circuit 14 described later and selectively providing a current path is maintained in a turned-on state.

When the rectified voltage increases, the number of channels sequentially emitting light increases from the side where the rectified voltage is applied to the three light-emitting diode channels (LED1, LED2, LED3). When the rectified voltage falls, The number of channels that sequentially emit light gradually decreases toward the side to which the rectified voltage is applied starting from the farther from the applied side.

The current control circuit 14 forms and maintains a current path by a hysteresis characteristic at a position corresponding to the current rectified voltage state among the three light emitting diode channels LED1, LED2, and LED3 so that the above-described light emission can be performed.

The current control circuit 14 includes three switching circuits 30_1, 30_2 and 30_3 which have a hysteresis characteristic and provide a current path to the light-emitting diode channels LED1, LED2 and LED3, and the current control circuit 14 Each of the switching circuits 30_1, 30_2, and 30_3 has a reference voltage for switching the current path.

Each of the switching circuits 30_1, 30_2, and 30_3 applies a hysteresis voltage whose reference voltage is changed in accordance with the rising and falling of the rectified voltage to a sensing voltage formed by the current flowing through the current path, So as to control the light emission of the light source 12.

The current control circuit 14 composed of the embodiment according to the present invention can be configured to control the constant current, and the current path that makes up the current control circuit 14 can be formed of the constant current path.

More specifically, the current control circuit 14 includes a reference voltage generating circuit 20, a current sensing resistor Rs, and three switching circuits 30_1, 30_2, and 30_3.

Here, the reference voltage generating circuit 20 includes a plurality of resistors R1, R2, ..., R4 connected in series to which a constant voltage VR is applied.

The resistor R1 is connected to the ground, and the constant voltage VR is applied to the resistor R4. Among them, the resistor R4 acts as a load resistor for adjusting the output. The resistors R1, R2, and R3 are for outputting reference voltages VREF1, VREF2, and VREF3 at different levels. Among the reference voltages VREF1, VREF2 and VREF3, the reference voltage VREF1 has the lowest voltage level and the reference voltage VREF3 has the highest voltage level.

That is, each of the resistors R1, R2, and R3 corresponds to three reference voltages VREF1 having a higher level corresponding to the rise of the rectified voltage applied to the three light emitting diode channels LED1, LED2, and LED3, , VREF2, and VREF3.

More specifically, the reference voltage VREF1 has a level for turning off the switching circuit 30_1 at the time when the light emitting diode channel LED2 emits light, and corresponds to the sensing voltage by the light emitting voltage of the light emitting diode channel LED2 As shown in FIG. The reference voltage VREF2 has a level for turning off the switching circuit 30_2 at the time when the light emitting diode channel LED3 emits light and has a level corresponding to the sensing voltage by the light emitting voltage of the light emitting diode LED3 So that the light emitting diode can be set to maintain a constant current state higher than the channel LED1. It is preferable that the reference voltage VREF3 is set so as to maintain a higher constant current state than the channel LED2 in the light emitting diode since the light emission of the light emitting diode channel LED3 must be maintained at a voltage in a range including the highest point of the rectified voltage Do.

The light emitting voltage of the light emitting diode channel LED1 is a voltage required for the light emitting diode channel LED1 to emit light and may be defined as a level capable of emitting light emitting diodes included in the light emitting diode channel LED1. The light emitting voltage of the light emitting diode channel LED2 is a voltage necessary for light emission of the light emitting diode channels LED1 and LED2 and can be defined as a level capable of emitting light emitting diodes included in the light emitting diode channels LED1 and LED2. The light emitting voltage of the light emitting diode channel LED3 is a voltage required for light emission of the three light emitting diode channels LED1, LED2 and LED3, and the light emitting diodes included in the three light emitting diode channels LED1, LED2 and LED3 emit light Can be defined as a level that can be achieved.

The three switching circuits 30_1, 30_2 and 30_3 are connected in parallel to the output terminals CH1, CH2 and CH3 of the light emitting diode channels LED1, LED2 and LED3, and the switching circuits 30_1, 30_2 and 30_3, Are commonly connected between the grounds and connected in common to a current sensing resistor Rs that provides a sensing voltage.

The three switching circuits 30_1, 30_2, and 30_3 selectively (independently) provide one current path for turning on the light source 12.

The three switching circuits 30_1, 30_2, and 30_3 are turned on and off by applying a hysteresis voltage whose reference voltage is changed to a sensing voltage of the current sensing resistor Rs in synchronization with the rising and falling of the rectified voltage to provide a current path do.

The switching circuits 30_1, 30_2, and 30_3 are supplied with a higher level reference voltage as they are connected to the light emitting diode channels LED1, LED2, and LED3 far from the position where the rectified voltage is applied. In other words, when the number of light emitting diode channels included in the light source is three, for example, the reference value applied to the switching circuit corresponding to the third light emitting diode channel is lower than the level of the reference voltage applied to the switching circuit corresponding to the second light emitting diode channel The level of the voltage is high.

Each of the switching circuits 30_1, 30_2, and 30_3 has a configuration including a comparison circuit and a switching element. The hysteresis voltage (rising reference voltage And generates a hysteresis voltage (falling reference voltage) having a level lower than the reference voltage in synchronization with the falling of the rectified voltage, and compares the hysteresis voltage (falling reference voltage) with the sensing voltage applied to the current sensing resistor Rs. The switching element has a configuration for switching the current path in accordance with the output of the comparison circuit. Here, it is preferable that the switching element is constituted by the NMOS transistor 52.

The comparison circuit of each of the switching circuits 30_1, 30_2 and 30_3 comprises a comparator 50 which compares the voltages of the positive input terminal (+) and the negative input terminal (-) and outputs an output corresponding to the comparison result, And a second resistor Rb connected between an output terminal of the comparator 50 and the positive input terminal (+), and a second resistor Rb connected between the output terminal of the comparator 50 and the positive input terminal (+ .

The sensing voltage of the current sensing resistor Rs is applied to the negative input terminal (-) of the comparator 50 and the negative terminal (-) of the comparator 50 of each of the switching circuits 30_1, 30_2 and 30_3 is connected to the current sensing resistor Rs.

When the level of the rectified voltage rises, the positive input terminal (+) of the comparator 50 is applied with the hysteresis voltage V + having the reference voltage raised by the current distribution by the first and second resistors Ra and Rb. When the level of the rectified voltage falls, the hysteresis voltage V + whose reference voltage has dropped due to the current distribution by the first and second resistors Ra and Rb is applied to the positive input terminal (+) of the comparator 50 do.

The hysteresis characteristic of the above-described comparison circuit will be described in more detail with reference to FIG. 2 to FIG.

2 (A) shows a general comparator circuit, and Fig. 2 (B) shows a comparison circuit according to the present invention. In order to understand the explanation, the reference voltage is represented by VREF, the input voltage corresponding to the sensing voltage of the current sensing resistance Rs is represented by VIN, the output voltage of the comparator is represented by VOUT, and the hysteresis voltage is represented by V + do. The hysteresis voltage corresponding to the rise of the rectified voltage is denoted by VH, and the hysteresis voltage corresponding to the falling of the rectified voltage is denoted by VL.

The general comparator of FIG. 2A outputs a high-level output voltage VOUT when the reference voltage VREF applied to the positive input terminal (+) is higher than the input voltage VIN applied to the negative input terminal (-), +) Is lower than the input voltage VIN applied to the negative input terminal (-), the low-level output voltage VOUT is output.

When the output voltage VOUT of the comparator shown in FIG. 2A is applied to the NMOS transistor 52, the NMOS transistor 52 is turned on when the high-level output voltage VOUT is applied and the low-level output voltage VOUT is applied Off.

As described above, the rectifying voltage rectified by the commercial power source is used for the LED lighting apparatus of the AC direct type, and the rectified voltage includes a large amount of noise components due to the commercial power source.

In the embodiment according to the present invention, the rectified voltage is applied to the current sensing resistor Rs through the current path through the turned-on NMOS transistor 52 of the switching circuits 30_1, 30_2, and 30_3. Therefore, the sensing voltage formed by the current sensing resistor Rs also follows the signal characteristic of the rectified voltage, resulting in a noise component as shown in Figs. 3 (A) and 4 (A).

Therefore, when the level of the input voltage VIN reaches the vicinity of the reference voltage VREF (SH1, SL1) in conjunction with the rise and fall of the rectified voltage, The output voltage VOUT is output in an unstable state in which the high and low states are repeated as shown in FIG.

When the output of the comparator in the unstable state as shown in FIGS. 3B and 4B is applied to the NMOS transistor 52 of FIG. 1, the NMOS transistor 52 is repeatedly turned on and off. The light emitting diode channels LED1, LED2, and LED3 connected to the switching circuits 30_1, 30_2, and 30_3 of FIG. 1 are flickered by the unstable switching operation of the NMOS transistor 52. FIG.

As described above, the embodiment of the present invention can employ the comparison circuit of FIG. 2 (B) in order to solve the unstable dimming operation with flickering due to the noise component in the LED lighting apparatus.

The comparison circuit of FIG. 2 (B) is characterized in that the output voltage VOUT connected to the rectified voltage by the current distribution of the first resistor Ra and the second resistor Rb is higher than the voltage formed at the positive input (+) of the comparator And the like.

The hysteresis voltage can be interpreted according to the Kirchhoff's current law as shown in Equations (1) to (3) below.

Therefore, the hysteresis voltage V + has a characteristic of rising or falling depending on VOUT.

It can be understood that VOUT has a positive polarity when it rises according to a rectified voltage, and has a negative polarity when it falls. It can be understood that VOUT has a positive polarity with respect to the rise period of noise since the same applies to the fine ripple component of noise, and it can be understood that VOUT has a negative polarity with respect to the falling period of noise.

A hysteresis voltage V + having a level higher than the reference voltage VREF may be defined as VH when the rectified voltage increases and VOUT has a positive polarity, and when the rectified voltage falls and VOUT has a negative polarity, The hysteresis voltage V + having a level lower than VREF may be defined as VL. Then, the potential difference between VH and VL can be defined as the hysteresis band (VHYS).

The VH of the level higher than the reference voltage VREF, the VL of the level lower than the reference voltage, and the hysteresis band VHYS may be defined by the following equations (4) to (6).

That is, the hysteresis voltage V + formed at the positive input terminal (+) of the comparator changes to VH at a level higher than the reference voltage VREF or VL at a level lower than the reference voltage VREF in accordance with rising and falling of the rectified voltage.

The operation of the comparison circuit of FIG. 2 (B) will be described.

3, a hysteresis voltage V + is formed at the VH level higher than the reference voltage VREF at the positive input terminal (+) of the comparator when the input voltage VIN rises as the rectified voltage rises. Therefore, when the input voltage VIN applied to the negative input terminal (-) is higher than the level VH of the hysteresis voltage (V +) of the positive input terminal (+), the comparator of FIG. Level output voltage VOUT (SH2)

In the comparator of FIG. 2B, even if the input voltage VIN temporarily falls below VH due to the noise component after the output voltage VOUT is converted to the low level, the output remains stable due to the hysteresis characteristic.

This is because a hysteresis voltage V + of a VL level is formed at the positive input terminal (+) of the comparator when the input voltage V IN temporarily drops due to the noise component.

If the noise component does not fall below the VL level, the output voltage VOUT of the comparator is not converted to the high level. Then, the hysteresis band VHYS is set so as to include the variable width due to the noise components that can be generated, so that the stability of the output of the comparator can be secured.

Conversely, when the input voltage VIN falls as the rectified voltage drops, the hysteresis voltage V + is formed at the positive input terminal (+) of the comparator at a VL level lower than the reference voltage VREF. Therefore, when the input voltage VIN applied to the negative input terminal (-) is lower than the level VL of the hysteresis voltage (V +) of the positive input terminal (+), the comparator of FIG. Level output voltage VOUT (SL2)

2B, even if the input voltage VIN temporarily increases to VL or the reference voltage VREF or more due to the noise component after the output voltage VOUT is converted to the high level, the output of the comparator in FIG. Maintain a stable state.

This is because a hysteresis voltage V + having a VH level higher than the reference voltage VREF is formed at the positive input terminal (+) of the comparator when the input voltage VIN temporarily increases due to the noise component.

If the noise component does not rise above the VH level, the output voltage VOUT of the comparator is not converted to a low level, and the hysteresis band VHYS is set to include the variable width due to the noise component that can be generated, Can be secured.

In the embodiment according to the present invention, the comparison circuit of the switching circuits 30_1, 30_2, and 30_3 is configured to have the hysteresis characteristics of FIGS. 2 to 4 described above.

Therefore, the switching circuits 30_1, 30_2, and 30_3 can provide a current path while maintaining a stable switching state without being affected by the noise component applied to the sensing voltage of the current sensing resistor Rs.

The specific operation of the embodiment according to the present invention having the hysteresis characteristic described in FIG. 1 and described with reference to FIGS. 2 to 4 will be described with reference to FIG.

5 is a waveform diagram illustrating the case of driving three light emitting diode channels (LED1, LED2, and LED3), and is for explaining light emission and quenching operations of light emitting diode channels (LED1, LED2, LED3) by hysteresis characteristics.

5, the level of the hysteresis voltage V + formed to have a level higher than the channel-specific reference voltage VREF by the hysteresis characteristic in FIGS. 3 and 4 is set to VON1, VON2, VON3 And the level of the hysteresis voltage V + formed to have a level lower than the channel-specific reference voltage VREF is expressed as VOFF1, VOFF2, and VOFF3 in view of the operational characteristics of the embodiment.

The reference voltage generating circuit 20 generates the reference voltages VREF1 (VREF1), VREF2 (VREF1), VREF2 (VREF1), VREF2 , VREF2, VREF3.

In the initial state in which the rectified voltage rises, each of the switching circuits 30_1, 30_2, and 30_3 is turned on in response to the hysteresis voltage V + by the reference voltages VREF1, VREF2, and VREF3 formed at the positive input terminal (+ The level of the sensing voltage applied to the negative input terminal (-) of the comparator 50 is low. Therefore, the comparator 50 outputs a high-level signal to the NMOS transistor 52, and the NMOS transistor 52 maintains the turned-on state.

The switching circuits 30_1, 30_2, and 30_3 remain turned on, but in the initial state, the level of the rectified voltage is not sufficient, so that the light emitting diode channel can not emit light. Therefore, a current path is not formed.

Thereafter, when the rectified voltage rises and rises to a level at which the light emitting diode channel LED1 can emit light, the light emitting diode channel LED1 emits light.

When the light emitting diode channel LED1 is lit, a current path including the NMOS transistor 52 and the current sensing resistor Rs of the switching circuit 30_1 connected to the output terminal CH1 of the light emitting diode channel LED1 is formed do. Then, a sensing voltage by the rectified voltage is formed in the current sensing resistor Rs.

After the light emitting diode channel LED1 is lit as described above, the rectifying voltage rises and the current path for the light emission of the light emitting diode channel LED1 is turned on by the switching circuit 30_1 until the light emitting diode channel LED2 emits light Can be provided.

At this time, a positive input terminal (+) of the comparator 50 of the switching circuit 30_1 providing a current path is supplied with a hysteresis voltage VON1 having a level of the reference voltage VREF1 changed by the hysteresis characteristic described with reference to FIGS. (V +) is applied to the sensing voltage formed corresponding to the rise of the rectified voltage.

When the rectified voltage gradually rises, the level of the sensing voltage formed in the current sensing resistor Rs also rises.

The comparator 50 of the switching circuit 30_1 outputs a high level voltage until the current sensing resistance Rs reaches the VOFF level of the hysteresis voltage V +, so that the NMOS transistor 52 maintains the turn-on state do.

In the state where the light emitting diode channel LED1 is illuminated and the current path through the switching circuit 30_1 and the current sensing resistor Rs is formed as described above, the rectified voltage rises to reach the level at which the light emitting diode channel LED2 emits light do.

The current path including the NMOS transistor 52 and the current sensing resistor Rs of the switching circuit 30_2 connected to the output terminal CH2 of the light emitting diode channel LED2 is formed when the light emitting diode channel LED2 is lighted do.

When the light emitting diode channel LED2 is lit, a current path is formed which is connected to the switching circuit 30_2 in the turned-on state by the current sensing resistor Rs. Therefore, a current flows in accordance with the application of the rectified voltage to the current path, and a sensing voltage due to a rectified voltage of a higher level than a state in which only the light emitting diode channel LED1 is emitted is formed in the current sensing resistor Rs.

The sensing voltage applied to the negative input terminal (-) of the comparator 50 of the switching circuit 30_1 is set to be higher than the VON1 level of the hysteresis voltage V + at the time of light emission of the light emitting diode channel LED2.

Accordingly, the comparator 50 of the switching circuit 30_1 outputs a low level signal, and the NMOS transistor 52 of the switching circuit 30_1 is turned off.

The sensing voltage formed in the current sensing resistor Rs at the time when the comparator 50 of the switching circuit 30_1 is switched to output a low level signal may include a noise component. However, even if the noise component is included in the sensing voltage, the comparator 50 of the switching circuit 30_1 stably maintains the state of outputting the low level signal by the hysteresis characteristic described with reference to Figs.

That is, even if the sensing voltage of the current sensing resistor Rs temporarily falls, the comparator 50 of the switching circuit 30_1 outputs the hysteresis voltage V + of the VON1 level lower than the reference voltage VREF1 at the time of the falling of the noise component So that the low level signal can be stably maintained and output as described above.

After the light emitting diode channels LED1 and LED2 are emitted as described above, the rectified voltage is increased. The switching of the current path of the light emitting diode channel LED2 and the light emission of the light emitting diode channel LED3 are the same as the switching of the current path of the light emitting diode channel LED1 and the light emitting of the light emitting diode channel LED2, Is omitted.

In accordance with the rise of the rectified voltage, the current path is sequentially switched in the order of the switching circuit 30_1, the switching circuit 30_2 and the switching circuit 30_3 in synchronization with the sequential light emission of the light-emitting diode channels LED1, LEd2 and LED3 .

Thereafter, the light emitting diode channel LED3 emits light, and a current path is formed through the switching circuit 30_3 and the current sensing resistor Rs. In this state, the rectified voltage rises to the peak and then begins to fall.

That is, after all the light emitting diode channels LED1, LED2, and LED3 are lit, the rectified voltage drops.

When the rectified voltage begins to fall and falls below the light emitting voltage of the light emitting diode channel (LED3), the light emitting diode channel (LED3) is extinguished and the current path is formed by the switching circuit 30_2.

At this time, the sensing voltage formed in the current sensing resistor Rs is connected to the light emitting diode channel LED2 and the switching circuit 30_2, which are farthest from the position where the rectified voltage is applied, among the light emitting diode channels LED1 and LED2, And the current is supplied through the resistor.

The sensing voltage applied to the current sensing resistor Rs is set to be the same as the sensing voltage applied to the light emitting diode channel that is the farthest from the position where the rectified voltage is applied It falls due to the current supplied through the diode channel and the switching circuit.

The current paths of the light-emitting diode channels LED1, LED2, and LED3 are sequentially extinguished one by one from a position away from the position where the rectified voltage is applied to the light-emitting diode channels LED1, LED2, and LED3 in accordance with the lowering of the rectified voltage.

As described above, in the embodiment of the present invention, the light-emitting diode channels LED1, LED2, and LED3 are turned on and off according to the rising and falling of the sensing voltage and the rectified voltage due to the current flowing through one current sensing resistor Rs It can be additionally emitted one by one from the applied position or additionally extinguished one by one in the opposite direction.

At this time, the switching circuits 30_1, 30_2, and 30_3, which provide the current path, can eliminate the influence of the noise included in the rectified voltage due to the hysteresis characteristic, so that the turn-on and turn-off states can be stabilized.

Meanwhile, the embodiment of the present invention can be implemented with an independent current sensing resistor as shown in FIG. 6 for driving the three LED channels LED1, LED2, and LED3.

The embodiment of FIG. 6 is different from the embodiment of FIG. 1 in that the current sensing resistors Rs1, Rs2, and Rs3 independently connected to the respective switching circuits 30_1, 30_2, and 30_3 are configured And the remaining components are the same. Therefore, redundant configuration explanation and operation explanation will be omitted.

In the configuration of Fig. 6, it is preferable that the three current sensing resistors Rs1, Rs2 and Rs3 have a uniform resistance value so as to satisfy the turn-on condition for each of the switching circuits 30_1, 30_2 and 30_3.

The reference voltages VREF1, VREF2 and VREF3 applied to the three switching circuits 30_1, 30_2 and 30_3 are provided so as to have a higher voltage as the rectifying voltage is applied. The emission voltage of each of the three light-emitting diode channels (LED1, LED2, LED3) increases with distance from the position where the rectified voltage is applied. Therefore, the three current sensing resistors Rs1, Rs2 and Rs3 of FIG. 8 having a uniform resistance value are applied to the switching circuits 30_1, 30_2 and 30_3 Quot;) < / RTI > of the sensing voltage.

The embodiment of the present invention can be implemented with a configuration in which a uniform reference voltage and a current sensing resistor independent of the reference voltage are used as shown in FIG. 7 to drive the three LED channels LED1, LED2, and LED3.

The embodiment of FIG. 7 differs from the embodiment of FIG. 6 in the configuration of the reference voltage generation circuit 20, and the remaining components are the same, so that redundant description of components and operation will be omitted.

7, the reference voltage generating circuit 20 provides the fixed reference voltage VREFC to each of the switching circuits 30_1, 30_2, and 30_3, and the constant voltage VR is divided by the resistors Rr1 and Rr2, And outputs a reference voltage VREFC.

It is preferable that the three current sensing resistors Rs1, Rs2, and Rs3 have a lower resistance value as the rectifying voltage is applied to the switching circuits 30_1, 30_2, and 30_3 so as to satisfy the turn-on condition.

The emission voltage for each of the light-emitting diode channels (LED1, LED2, LED3) increases as the voltage increases from the position where the rectified voltage is applied.

Therefore, as the current sensing resistors Rs1, Rs2, and Rs3 having a low resistance value become farther from the position where the rectified voltage is applied, a higher emission voltage is applied to the fixed reference voltage Vrefc as the rectifying voltage increases, And can provide a corresponding sensing voltage.

6 and 7, the current path can be stably maintained by the hysteresis characteristic of each of the switching circuits 30_1, 30_2, and 30_3, thereby realizing a dimming function for eliminating flicker due to noise components.

The embodiment according to the present invention can be applied to the control of the output voltage for varying the illuminance using a dimmer as shown in FIG.

The waveform diagram of FIG. 8 is for explaining that when the phase of the output voltage is controlled by the dimmer, the unstable flicker is improved corresponding to the case where the output voltage is located at the switching boundary voltage between the light-emitting diode channels.

Referring to FIG. 8, the rising reference voltage and the falling reference voltage are set to be larger than the fluctuation width which varies according to the unstable characteristics of the output voltage due to the hysteresis characteristic according to the present invention. That is, the hysteresis band is set to be larger than the fluctuation width of the output voltage according to noise or unstable signal characteristics.

Therefore, when the output voltage is located at the reference voltage, that is, the switching boundary voltage, even if the phase change of the output voltage occurs within the hysteresis band range, the alternation of the switching states of the light-emitting diode channels can be prevented.

That is, when the output voltage increases, the light emitting diode can emit light above the rising reference voltage due to the hysteresis characteristic and maintain a stable light emitting state. When the output voltage decreases, the light emitting diode can be stably lighted out by quenching below the falling reference voltage by the hysteresis characteristic have.

Therefore, when the illuminance is varied using the dimmer, even if the output voltage is located at the switching boundary voltage between the LED diodes, the switching state between the LED diodes can be alternated to eliminate unstable flickering.

10: rectification circuit 12: light source
14: current control circuit 20: reference voltage generating circuit
30_1, 30_2, 30_3: switching circuit 50: comparator
52: NMOS transistor

Claims (17)

A power supply unit for providing a rectified voltage obtained by converting a commercial power supply;
A light source in which a plurality of light emitting diode channels sequentially emit light in accordance with the rectified voltage; And
And a plurality of switching circuits for providing a current path to the light emitting diode channels, wherein each of the switching circuits provides a rising reference voltage corresponding to the rise of the rectified voltage and a falling reference voltage corresponding to the falling of the rectified voltage And a current control circuit for controlling the light emission of the light source by switching the current path according to a comparison result between the sensing voltage formed by the current flowing through the current path and the rising or falling reference voltage, Light Emitting Diodes. The method according to claim 1,
And the rising reference voltage corresponding to the same channel is provided at a level higher than the falling reference voltage. The power supply circuit according to claim 1,
A reference voltage generation circuit for providing a reference voltage of a different level for each of the plurality of switching circuits;
A plurality of light emitting diode channels connected in parallel to each of the light emitting diode channels and selectively providing the current path for the light emitting diode channels, wherein the rising reference voltage and the rising reference voltage vary according to the rising and falling of the rectified voltage, The plurality of switching circuits providing the falling reference voltage and switching the current path according to a result of comparison between the sensing voltage and the rising reference voltage or the sensing voltage of the falling reference voltage; And
And a current sensing resistor connected in common to the plurality of switching circuits to form the current path and provide the sensing voltage. The power supply circuit according to claim 1,
A reference voltage generation circuit for providing a reference voltage of a different level for each of the plurality of switching circuits;
A current path for the light emitting diode channels that are connected in parallel to the light emitting diode channels and selectively provide the current path for the light emitting diode channels, and the rising reference voltage having the reference voltage varied corresponding to the rising and falling of the rectified voltage, The plurality of switching circuits providing the falling reference voltage and switching the current path according to a result of comparison between the sensing voltage and the rising reference voltage or the falling reference voltage; And
And a plurality of current sensing resistors connected to the plurality of switching circuits to form the current path and provide the sensing voltage to the switching circuit to which the sensing circuit is connected. 5. The method of claim 4,
Wherein the plurality of current sensing resistors have a uniform resistance value. The method according to claim 3 or 4,
Wherein the reference voltage generating circuit provides the reference voltage corresponding to the light emitting voltage of the next light emitting diode channel for each switching circuit and the switching circuit connected to the last light emitting diode channel outputs the reference voltage So as to have a high level. The method according to claim 6,
Wherein the reference voltage generating circuit provides the reference voltage higher than the reference voltage for the switching circuit connected to the light emitting diode channel having the higher light emitting voltage and outputs the lower reference voltage for the switching circuit connected to the light emitting diode channel having the lower light emitting voltage The light emitting diode illuminating device. The power supply circuit according to claim 1,
A reference voltage generating circuit for providing the reference voltage having a fixed level;
A current path for the light emitting diode channels that are connected in parallel to the light emitting diode channels and selectively provide the current path for the light emitting diode channels, and the rising reference voltage having the reference voltage varied corresponding to the rising and falling of the rectified voltage, The plurality of switching circuits providing the falling reference voltage and switching the current path according to a result of comparison between the sensing voltage and the rising reference voltage or the falling reference voltage; And
And a plurality of current sensing resistors connected to the plurality of switching circuits to form the current path and provide the sensing voltage to the switching circuit to which the sensing circuit is connected. 9. The method of claim 8,
Wherein the plurality of current sensing resistors have a lower resistance value as the rectifying voltage increases. The semiconductor integrated circuit according to any one of claims 3, 4, and 8,
A rising reference voltage having a level higher than the reference voltage and a falling reference voltage having a lower level than the reference voltage in conjunction with a falling of the rectified voltage in association with the rise of the rectified voltage and comparing the lowered reference voltage with the sensing voltage Circuit; And
And a switching device for switching the current path according to the output of the comparison circuit. 11. The semiconductor memory device according to claim 10,
A comparator for comparing the voltages of the first and second input terminals and outputting a signal corresponding to the comparison result to an output terminal;
A first resistor to which the reference voltage is applied and is connected to the first input of the comparator; And
And a second resistor coupled between the first input and the output of the comparator,
A sensing voltage is applied to the second input terminal of the comparator, and when the level of the reference voltage is varied by current distribution by the first and second resistors, Wherein when the level of the rectified voltage is lowered, the falling reference voltage is formed at the first input terminal and is compared with the sensing voltage. 12. The method of claim 11,
Wherein the first input terminal is a positive terminal and the second input terminal is a negative terminal. A control circuit of a light emitting diode lighting device for controlling a light source in which a plurality of light emitting diode channels are arranged in series to be driven in accordance with application of a rectified voltage,
And a plurality of switching circuits for providing a current path to the light emitting diode channels, wherein each of the switching circuits provides a rising reference voltage corresponding to the rise of the rectified voltage and a falling reference voltage corresponding to the falling of the rectified voltage And controls the light emission of the light source by switching the current path according to a result of comparison between a sensing voltage formed by the current flowing in the current path and the rising or falling reference voltage. . 14. The method of claim 13,
Wherein the rising reference voltage corresponding to the same channel is provided at a level higher than the falling reference voltage. 14. The semiconductor memory device according to claim 13,
A reference voltage generating circuit for providing the reference voltage at a different level for each of the plurality of switching circuits;
A current path for the light emitting diode channels that are connected in parallel to the light emitting diode channels and selectively provide the current path for the light emitting diode channels, and the rising reference voltage having the reference voltage varied corresponding to the rising and falling of the rectified voltage, A plurality of said switching circuits for providing a falling reference voltage and switching said current path according to a result of comparing said sensing voltage with said rising reference voltage or said falling reference voltage; And
And a current sensing resistor connected in common to the plurality of switching circuits to form the current path and to provide the sensing voltage by the current. 14. The semiconductor memory device according to claim 13,
A reference voltage generating circuit for providing the reference voltage at a different level for each of the plurality of switching circuits;
A current path for the light emitting diode channels that are connected in parallel to the light emitting diode channels and selectively provide the current path for the light emitting diode channels, and the rising reference voltage having the reference voltage varied corresponding to the rising and falling of the rectified voltage, A plurality of said switching circuits for providing said falling reference voltage and switching said current path according to a result of comparing said sensing voltage with said rising reference voltage or said falling reference voltage; And
And a plurality of current sensing resistors connected to the plurality of switching circuits to form the current path and provide the sensing voltage for the current to the switching circuit to which the sensing circuit is connected. 14. The semiconductor memory device according to claim 13,
A reference voltage generating circuit for providing the reference voltage having a fixed level;
A current path for the light emitting diode channels that are connected in parallel to the light emitting diode channels and selectively provide the current path for the light emitting diode channels, and the rising reference voltage having the reference voltage varied corresponding to the rising and falling of the rectified voltage, A plurality of said switching circuits for providing a falling reference voltage and switching said current path according to a result of comparison between said sensing voltage and said rising reference voltage or said falling reference voltage; And
And a plurality of current sensing resistors connected to the plurality of switching circuits to form the current path and provide the sensing voltage for the current to the switching circuit to which the sensing circuit is connected.

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