KR101322939B1 - Light Emitting Apparatus and LED Driving Method using the same - Google Patents

Abstract

The present invention relates to a light emitting device and a LED driving method using the same.
The light emitting device according to an aspect of the present invention, which is driven by a direct current power source and sequentially connected in series with the first to n-th LED group, and detects a current flowing through the output terminal of the light source is out of the preset current range In this case, the control unit may include a driving controller for changing the number of LED groups driven by the light source unit.

Description

Light Emitting Apparatus and LED Driving Method using the same}

The present invention relates to a light emitting device and a LED driving method using the same.

A light emitting device (LED) is a semiconductor device that can emit light of various colors by configuring a light emitting source by changing compound semiconductor materials such as GaAs, AlGaAs, GaN, and InGaAlP. Such a light emitting device has been widely used in various fields such as TV, computer, lighting, automobile and the like due to advantages of excellent monochromatic peak wavelength, excellent light efficiency and miniaturization, and environment friendly and low power consumption. It is the situation that is going out.

Such a light emitting device (LED) has an exponential current with respect to the voltage applied to both ends.

Since the light emitting device is used as a light source for a commercial AC power source used in homes, offices, or outdoors, it is common to use a constant current circuit that generates a constant current. That is, since the current is very sensitive to the voltage applied to the LED, an apparatus or method for stably controlling the current flowing through the LED is required in order to use an AC power source having a very wide voltage fluctuation range as an input power source.

One of the objects of the present invention is to provide a light emitting device having a high efficiency and a low cost and a LED driving method using the same.

According to an aspect of the present invention,

A light source unit which is driven by a DC power source and includes first to n-th LED groups sequentially connected to each other, and detects a current flowing through an output terminal of the light source unit to determine the number of LED groups driven by the light source unit when it is out of a preset current range. It is possible to provide a light emitting device including a driving control unit for changing.

According to an embodiment of the present disclosure, the driving controller detects a current flowing through the output terminal of the light source unit to generate an input signal, and compares the input signal with a reference signal to determine whether the predetermined current range is out of the predetermined range. Can be.

In an embodiment of the present disclosure, the driving controller may include a comparator configured to output a control signal when the input signal generated by detecting a current flowing in the light source unit is out of the preset current range by comparing with the reference signal; A control signal outputted from the controller is input, and when the control signal is input, the switch controller outputs a signal for changing the number of LED groups to be driven; It may include a switch that is turned on / off by the signal output from the switch controller.

In an embodiment of the present disclosure, the comparator may output an upper limit or a lower limit control signal when the current detected at the output of the light source is outside the preset current range.

In one embodiment of the present invention, the switch controller, the signal for controlling to increase the number of LED groups to drive when the upper limit control signal is input, and the signal for controlling to reduce the number of LED groups to drive when the lower limit control signal is input You can output

According to an embodiment of the present disclosure, the driving controller may be configured to output the upper limit limit signal for a predetermined period within a period in which the lower limit limit signal is first output from the point at which the upper limit limit signal is first output in a cycle of driving the DC power supply. If not output, it may further include a flicker prevention circuit for forcibly turning off the switch (OFF).

The comparator may include a first comparator configured to output an upper limit control signal when the input signal is greater than the first reference signal by comparing the input signal with a first reference signal. And a second comparator configured to output a lower limit control signal when the input signal is smaller than the second reference signal in comparison with a second reference signal.

In an embodiment, the first and second comparators are comparators or operational amplifiers (OP Amps), and a first reference signal is input to the first comparator inverting input terminal. The input signal is input to the non-inverting input terminal of the first comparator, the input signal is input to the inverting input terminal of the second comparator, and the second reference signal is input to the non-inverting input terminal of the second comparator. Can be.

In an embodiment of the present disclosure, the electronic device may further include a voltage regulator configured to receive a portion of the DC power and output a constant voltage, and a plurality of resistors connected in series between an output terminal of the voltage regulator and a ground, wherein the first and second references may be used. The signal may be set to a voltage divided by the plurality of resistors.

In an embodiment of the present disclosure, the comparator may further include a resistor connected between the output terminal of the light source unit and the ground, and the input signal may be generated in the form of a voltage by the resistor.

According to an embodiment of the present disclosure, the switch may include first to n-1 switches connected between the output terminals of the first to n-1 LED groups and the resistor, respectively.

In one embodiment of the present invention, the switch controller may control the switch on / off.

In one embodiment of the present invention, it may further include a rectifier for converting an AC power input from the outside into a DC power.

In one embodiment of the present invention, the rectifying unit may include a bridge diode.

In one embodiment of the present invention, each of the first to n-th LED group may include at least one LED.

In an embodiment of the present disclosure, at least one of the first to n-th LED groups includes a plurality of LEDs, and the plurality of LEDs are electrically connected in any one of a series, parallel, and a combination of serial and parallel types. It can have

Another aspect of the invention,

Detecting a current flowing through the first through n-th LED groups sequentially connected to a DC power supply; setting a range of a driving current for controlling the current flowing through the first through n-th LED groups; The method may include controlling the number of LED groups to be driven at a time point when the current detected from the 1 st to n th LED groups is out of the preset driving current range.

In one embodiment of the present invention, the range of the driving current may be set to have an upper limit and a lower limit of the current.

In an embodiment of the present disclosure, the controlling of the number of LED groups to be driven may include controlling the number of LEDs to be driven when the current flowing through the first to n-th LED groups is greater than the upper limit. When the current flowing through the first to nth LED groups is smaller than the lower limit, the number of LEDs to be driven may be reduced.

In an embodiment of the present disclosure, the controlling of the number of LED groups to be driven may include changing the first to nth times at a time when a current detected from the first to nth LED groups is out of a range of a preset current. The current detected from the LED group can be controlled to decrease or increase momentarily.

According to an embodiment of the present invention, when the current flowing through the first to nth LED groups is greater than the upper limit, the current detected from the first to nth LED groups decreases instantaneously, and the first to nth LED groups When the current flowing in the lower than the lower limit, the current detected from the first to n-th LED group can be controlled to increase instantly.

In one embodiment of the present invention, during the driving of the DC power supply, the current flowing through the first to n-th LED group is detected for a predetermined period of time within a section that becomes smaller than the lower limit for the first time from the time when the current flowing through the first to n-th LED groups becomes larger than the upper limit for the first time. If the current is within the predetermined current range, the method may further include controlling the number of LED groups to be forcibly changed.

In an embodiment of the present disclosure, in the controlling of changing the number of LED groups forcibly driven, the number of LED groups for driving may be increased.

In one embodiment of the present invention, the first to n-th LED group is sequentially lit after the first to n-th LED group in the driving period of the DC power, the n-th to the first LED group is sequentially It can be controlled to turn off.

According to an embodiment of the present invention, in the sections sequentially lit from the first LED group to the n-th LED group, when the n-th LED group is turned on, the first to n-th LED groups may be turned on. have.

In one embodiment of the present invention, the current flowing in the first to n-th LED group may be detected in the form of a voltage.

In one embodiment of the present invention, the current flowing through the first to n-th LED group may be detected at the output terminal of the n-th LED group.

In an embodiment of the present disclosure, the method may further include converting an AC power input from the outside into a full wave rectifier and converting the AC power into DC power.

It can be provided in a light emitting device and a LED driving method capable of driving with a low cost, high efficiency by consisting of a simple circuit.

1 is a view schematically showing a light emitting device according to an embodiment of the present invention.
FIG. 2 is a diagram illustrating an example of a light emitting device according to the embodiment illustrated in FIG. 1.
3 schematically shows waveforms of voltage and current that can be applied to a light emitting device according to an embodiment of the present invention.
4 is a view schematically showing a light emitting device according to another embodiment of the present invention.
5 is a diagram illustrating waveforms of voltages and currents of a light source unit that may be driven by the light emitting device illustrated in FIG. 4.
FIG. 6 is a diagram for describing an operation of the light emitting device illustrated in FIGS. 4 and 5.

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

However, the embodiments of the present invention can be modified into various other forms, and the scope of the present invention is not limited to the embodiments described below. Further, the embodiments of the present invention are provided to more fully explain the present invention to those skilled in the art. Accordingly, the shape and size of elements in the drawings may be exaggerated for clarity, and the elements denoted by the same reference numerals in the drawings are the same elements.

1 is a view schematically showing a light emitting device according to an embodiment of the present invention.

Referring to FIG. 1, the light emitting device according to the present embodiment includes a light source unit 20 including first to nth LED groups G1, G2... The driving controller 30 may detect a current flowing through the output terminal of the light source unit 20 to change the number of LED groups driven by the light source unit when it is out of a preset current range.

In the present embodiment, the light emitting device may further include a rectifying unit 10 for converting the AC power input from the outside into a DC power source, the DC power converted by the rectifying unit 10 is input to the light source unit 20. Can be.

The rectifier 10 may rectify an AC power (for example, 220VAC or 100VAC commercial AC power) applied from the outside. Among the output voltages rectified from the rectifying unit 10, the side connected to the light source unit 20 has a higher potential, and the side connected to the drive control unit 30 refers to a side having a lower potential. The lower side can be understood as the reference potential, that is, ground (GND). Therefore, the current flows from the rectifying unit 10 to the ground GND via the light source unit 20. In the present embodiment, a description will be made based on the fact that the external AC power is full-wave rectified in the rectifying unit 10.

On the other hand, the DC power source described in the present invention refers to a DC power source having a broad meaning including not only a case where the magnitude of the voltage is constant with time, but also a case where the magnitude changes with time but the polarity is constant. In addition, the fundamental frequency of the voltage change is assumed to be 100 Hz or more so that the flicker cannot be recognized by the human eye.

The light source unit 20 may include first to n-th LED groups G1 and G2 to Gn sequentially connected in series, and each of the first to n-th LED groups G1 and G2 to Gn. May be connected to the driving controller 30. The first to n-th LED groups G1, G2, ... Gn are devices that use at least one LED as a light source, and in the case of a plurality of LEDs, a plurality of LEDs are used in series, parallel, or parallel connection in series. It is configured to have various electrical connections in the form and can be driven as one unit. In FIG. 1, each LED group G1, G2... Gn constituting the light source unit 20 is illustrated as including one LED for convenience of description, but is not limited thereto. It can be configured to have a relationship.

The driving controller 30 may include at least one of the first to nth LED groups G1, G2... Gn constituting the light source unit 20 according to the magnitude of the voltage V1 output from the rectifying unit 10. Some can be controlled to drive.

The driving controller 30 increases the number of LED groups driving in a section in which the size of the rectified DC power voltage V1 increases, and the number of LED groups driving in a section in which the size of the rectified DC power voltage decreases. The number of LEDs that can be driven may be driven according to the periodically changing input voltage, V1. In this case, the operation of reducing or increasing the number of LED groups to be driven may be controlled by detecting a current flowing in the light source unit 20, comparing it with a reference signal, and maintaining the detected current within a predetermined range.

Hereinafter, the operation of the driving controller 30 will be described in more detail with reference to FIGS. 2 and 3.

FIG. 2 is a view showing an example of a light emitting device according to the embodiment shown in FIG. 1, and FIG. 3 schematically shows waveforms of voltage and current applicable to the light emitting device according to an embodiment of the present invention.

First, referring to FIG. 2, the light emitting device 100 according to the present embodiment includes a rectifying unit 10 for converting AC power input from the outside into a DC power source and a DC power source converted by the rectifying unit 10. The light source unit 20 includes a first to n-th group of LEDs sequentially connected to each other, and the light source unit 20 detects a current flowing through an output terminal of the light source unit 20 to move out of a preset current range. It may include a drive control unit 30 for changing the number of LED groups.

In the present embodiment, a bridge diode may be applied to the rectifier 10 to convert AC power Vac input from the outside into DC power. The DC power supply voltage V1 rectified by the rectifier 10 represents a form of a full-wave rectified sinusoidal wave, and a driving current (GND) from the output terminal of the rectifier 10 to the ground GND through the light source 20. If) flows.

The light source unit 20 includes first to fourth LED groups G1, G2, G3, and G4 sequentially connected to an output terminal of the rectifier 10, and the first to fourth LED groups G1 and G2. , G3, G4) is illustrated as including one LED, but is not limited thereto, and each group may include a plurality of LEDs connected in series and in parallel.

In the LED driving circuit using a general AC commercial power source, except for the boost circuit of the SMPS, when a plurality of LEDs are connected in series to the output terminal of the rectifying unit 10 composed of a bridge diode, the output voltage V1 of the rectifying unit No current flows in a section smaller than the total driving voltage of the plurality of LEDs. That is, all the LEDs are driven only in a section showing a voltage greater than the driving voltage Vf in the full-wave rectified sine wave, and all LEDs cannot be driven in a section showing a voltage smaller than the driving voltage Vf.

However, in the light emitting device 100 according to the present embodiment, the first to nth LED groups G1 and G2 .. according to the magnitude of the power supply voltage V1 rectified by the switch 31 of the driving control unit 30. By sequentially lighting at least a part of Gn), the driving efficiency may be improved by minimizing a section in which all LEDs are not lit.

In addition, by arranging a small capacitor at the output terminal of the rectifier 10, it is also possible to eliminate the section where the drive current If becomes zero while satisfying the power supply current harmonic regulation.

To this end, the driving control unit 30 is connected to the output terminal of the light source unit 20, and compares the input signal generated by detecting the current flowing in the light source unit 20 with the reference signal outside the predetermined current range A comparator 31 for outputting a control signal, a switch controller 32 for outputting a signal for controlling to increase or decrease the number of LED groups driven by receiving the control signal output from the comparator 31 '; The switch controller 32 is connected to at least some of the output terminals of the first to nth LED groups G1, G2..., Gn, and here, the first to fourth LED groups G1, G2, G3, and G4. It may include a switch 33 that is turned on / off by the output signal.

Here, the comparator 31 may output an upper limit or a lower limit control signal when the current detected at the output terminal of the light source unit 20 is outside a preset current range, and the upper limit control signal is set by the switch controller 32. When the input is controlled, the number of driving LED groups may be increased, and when the lower limit control signal is input, the number of driving LED groups may be reduced.

The comparator 31 may include at least two first and second comparators U1 and U2 for detecting a current flowing through the light source unit 20 and comparing it with a reference signal, and the first and second comparators. For example, a comparator or an operational amplifier (OP amp) may be applied.

The first comparator U1 may output an upper limit control signal UL when the input signal is greater than the first reference signal VR1 by comparing the input signal with the first reference signal VR1. The comparator U2 may output the lower limit control signal LL when the input signal is smaller than the second reference signal VR2 by comparing the input signal with the second reference signal VR2.

In this case, a first reference signal VR1 may be input to the inverting input terminal (-) of the first comparator U1 and a second reference signal to the non-inverting input terminal (+) of the second comparator U2. VR2 may be input. The first and second reference signals VR1 and VR2 are fixed values and may be set as part of the voltage VREF stabilized by the voltage regulator as in the present embodiment. Although not shown in detail, the switch controller may be driven using a part of the voltage output from the voltage regulator.

The voltage regulator may be connected to an output terminal of the rectifier 10 to receive a portion of the DC power voltage V1 converted by the rectifier 10 to output a constant voltage. A plurality of resistors R3, R4, and R5 may be connected between the output terminal and the ground GND. In this case, the first and second reference signals VR1 and VR2 input to the first and second comparators U1 and U2 may be set to voltages divided by the plurality of resistors R3, R4 and R5. Can be.

로 설정될 수 있으며, 이와 유사하게, 상기 제2 기준신호(VR2)는

로 설정될 수 있다. 이때, 상기 제1 및 제2 기준신호(VR1, VR2) 각각은 상기 광원부(20)에 흐르는 전류의 상한(If(UL)) 및 하한(If(LL))을 설정할 수 있다.
Specifically, in the embodiment shown in FIG. 2, the first reference signal VR1 is

It may be set to, similarly, the second reference signal VR2 is

Lt; / RTI > In this case, each of the first and second reference signals VR1 and VR2 may set an upper limit If (UL) and a lower limit If (LL) of the current flowing through the light source unit 20.

Upper limit (UL) and lower limit (LL) of the driving current If detected at the output terminal d of the light source unit 20 are the first and second comparators U1 and U2 as follows. Resistors R3, R4, and R5 connected between the ground and ground GND, and the output terminal of the light source unit 20; The size of the resistor R2 connected between the ground GND may be set as follows. Here, the upper limit and the lower limit of the driving current indicate the driving voltage of the LED group constituting the light source unit 20. Can be set in consideration.

The comparator 31 outputs an upper limit control signal UL to the switch controller 32 when If> If (UL) through the first comparator U1, and at this time, the upper limit control signal The switch can be controlled to increase the number of LED groups driving according to UL).

On the contrary, the comparator 31 outputs the lower limit control signal LL to the switch controller 32 when the driving current If <If (LL) is reached through the second comparator U2, and lowers the switch controller 32. The switch may be controlled to reduce the number of LEDs driven according to the control signal LL.

Specifically, the first comparator U1 receives the voltage Vd detected from the current flowing through the light source unit 20 as a non-inverting input terminal (+), and converts the first reference signal VR1 into an inverting input terminal ( The upper limit control signal UL may be generated by the switch controller 32 when the detected voltage Vd is greater than the first reference signal VR1.

Meanwhile, the second comparator U2 receives the voltage Vd detected from the current flowing in the light source unit 20 as an inverting input terminal (−) and receives the second reference signal VR2 as a non-inverting input terminal (+). When the input voltage is inputted as a reference signal, the magnitude of the signal is compared, and if the detected voltage Vd is smaller than the second reference signal VR2, the lower limit control signal LL may be generated by the switch control 32.

The switch controller 32 receives the upper or lower limit control signal UL or LL output from the comparator 31, and is driven when the upper limit control signal UL is input from the first comparator U1. The number of groups may be controlled to increase, and conversely, the lower limit control signal LL may be input from the second comparator U2 to control the number of LED groups to be reduced. In this case, a shift resistor, a counter, a decoder, or the like may be applied to the switch controller 32, but is not limited thereto.

The switch 33 is connected to at least some of the output terminals of the first to nth LED groups G1, G2... Gn, and is turned on / off by a signal output from the switch controller 32. By doing so, the path of the current flowing through the light source unit 20 can be changed.

As shown in FIG. 2, the switch 33 includes first to n-th LED groups G1 and G2 to Gn− among the first to nth LED groups G1 and G2 to Gn. The first through n-th switches SW1, SW2, SWn-1 may be connected between the output terminal 1) and the current detection resistor R2 or ground GND, respectively. In addition, other active and passive elements other than the current detection resistor may be further added between the output terminal of the LED group and the ground GND.

For example, when the second switch SW2 is closed and the first and third switches SW1 and SW3 are open, the current If passes through the first and second LED groups G1 and G2 to the second. It flows through the switch SW2 and the resistor R2 to the ground GND. At this time, when the voltage Vd = If × R2 detected by the comparator 31 is between the first and second reference signals VR1 and VR2, the states of the first to third switches SW1, SW2, and SW3 are It remains the same as before.

On the other hand, when the voltage Vd detected by the comparator 31 is greater than the first reference signal VR1, the second switch SW2 is opened and the third switch SW3 is closed to drive the drive current If. To the ground GND from the third LED group G1, G2, and G3 through the resistor R2, and, conversely, the voltage Vd detected by the comparator 31 is greater than the second reference signal VR2. In a small case, the second switch SW2 is opened and the first switch SW1 is closed so that the driving current If flows from the first LED group G1 through the resistor R2 to the ground GND.

3 schematically shows waveforms of voltage and current that can be applied to a light emitting device according to an embodiment of the present invention. Specifically, the voltage and current waveforms and the operation of the LED group and the switch when the light emitting device 100 shown in FIG. 2 is applied are shown based on one cycle of the rectified DC power supply voltage V1. .

The two waveforms shown in the upper portion of FIG. 3A are voltage V1 propagated and rectified by the rectifier 10 and the driving voltages of the first to fourth LED groups G1, G2, G3, and G4. The waveform of Vf) is shown, and the waveform shown in the lower part of FIG. 3 (a) shows the driving current If flowing through the light source unit 20. 3 (b) shows the on / off operation of the first to third switches SW1, SW2, and SW3 of the switch 33, and FIG. 3 (c) shows the first and second comparators of the comparator 31 ( The signal detected at U1, U2) and the LED group driven accordingly are shown.

2 and 3, an operation and a driving method in one cycle of the full-wave rectified DC power supply voltage V1 will be described in detail. Here, it is assumed that the rectified DC power supply voltage V1 is used only to drive the light source unit 20 to facilitate the convenience of description and easy understanding of the invention, and the power consumed to drive the rest of the circuit is very high. It is small and will not be considered.

However, this is not intended to limit the light emitting device according to the present embodiment to an embodiment in which the rectified DC power supply voltage V1 is applied only to drive the light source unit 20. It will be apparent to those skilled in the art that some may be used as power sources for driving other drive circuits.

An LED driving method according to an embodiment of the present invention, detecting the current flowing through the first to n-th LED group (G1, G2 ... Gn) connected in series to the rectified DC power supply, and the first Setting a range of a driving current for controlling a current flowing through the n th through n th LED groups G1, G2 ... Gn, and detecting from the first th n th LED groups G1, G2 ... Gn The method may include controlling the number of LED groups to be driven at a time when the current is out of the preset current range.

First, in operation t1 to t2, the driving current If does not flow in the initial state where the voltage is low (If = 0), and the voltage Vd detected by the driving current If is the second comparator. It has a smaller value than the second reference signal VR2 of U2. (In this case, the reference signal of the second comparator U2 may be set to an appropriate value using a resistor as described above.) Therefore, the second comparator U2 uses the switch controller 32 as a lower limit signal ( LL), and accordingly, the switch controller 32 can be controlled to turn on the first switch SW1. Once the first switch SW1 is turned on, even if the lower limit signal LL is detected H, the state of the first switch SW1 does not change. As the DC power voltage V1 gradually increases, the driving current If begins to flow, and the voltage Vd detected by the driving current If is greater than the first reference signal VR1 and the second reference signal ( It has a smaller value than VR2 (VR1 < Vd < VR2), and in this case, the first switch SW1 is kept closed.

As the DC power supply voltage V1 increases, the driving current If also increases so that the voltage Vd detected by the driving current If becomes greater than the first reference signal VR1 of the first comparator U1. That is, when it is time t2 in FIG. 3, the first comparator U1 outputs an upper limit control signal UL to the switch controller 32, and inputs the switch controller 32 from the first comparator U1. According to the upper limit control signal UL, the first switch SW1 is turned off and the second switch SW2 is turned on to increase the number of LEDs to be driven.

At this time, the driving current If flowing from the first switch SW1 to the ground GND in the first LED group G1 is the first and second LED groups G1 and G2 and the second switch SW2. ) Is passed through R2 to ground (GND). In addition, when the first switch SW1 is turned off and the second switch SW2 is turned on (t2), the driving voltage Vf is increased by the second LED group G2. As a result, the driving current If decreases instantaneously.

에서

로 변화된다.
Hereinafter, for convenience of explanation, it is assumed that the driving voltages of the first to fourth LED groups G1, G2, G3, and G4 are all the same as Vf0. The driving current If at t2 is reduced by the second LED group G2 which is additionally driven, specifically,

in

Is changed.

Next, the operation in the period t2 to t3 is detected by the driving current If and the driving current If as the rectified DC power supply voltage V1 increases while the driving current If decreases. The voltage Vd gradually increases.

에서

로 변경될 수 있다.
When the voltage Vd detected by the driving current If becomes greater than the first reference signal VR1 (Vd> VR1), that is, when t3, the first comparator U1 switches the switch controller 32. Outputs a low signal (UL), turns off the second switch SW2 so that a larger number of LEDs can be driven by the switch controller 32, and turns on the third switch SW3. The signal H can be output. In this case, the driving current If flowing from the first and second LED groups G1 and G2 to the ground GND through the resistor R2 is a resistance (from the first to third LED groups G1, G2 and G3). The current flows to ground GND through R2), and the driving current If decreases momentarily as the driving voltage Vf of the LED increases at t3. That is, the driving current If at t3 is

in

. &Lt; / RTI &gt;

Next, referring to the operation of the period t3 to t4, when the voltage Vd detected by the reduced driving current If is between the first reference signal VR1 and the second reference signal VR2, that is, When VR2 <Vd <VR1, the driving current If flows through the first to third LED groups G1, G2, and G3, and therefore, the first to third LED groups G1, G2, and G3 It can work.

에서

로 변경될 수 있다.
As before, when the drive current If gradually increases and the voltage Vd detected by the drive current If becomes larger than the first reference voltage VR1 (t4), the switch controller 32 is turned to the third. By turning off the switch SW3 so that all the switches are off, the drive current If can flow through the first to fourth LED groups G1, G2, G3, G4. have. That is, the driving current If at t4 is

in

. &Lt; / RTI &gt;

Next, referring to the operation of the period t4 to t5, the third switch SW3 is turned off at t4, and the voltage Vd detected by the driving current If in the comparator 31 is the first reference. When the voltage VR1 is between the second reference voltage VR2, the third switch SW3 is maintained in the OFF state.

In this case, the driving current If flows from the first to fourth LED groups G1, G2, G3, and G4 to RND via R2, and the rectified DC power supply voltage V1 reaches a peak. As it gradually decreases afterwards, the driving current If also decreases together.

As the driving current If decreases, when the voltage Vd detected by the driving current If becomes smaller than the second reference signal VR2 of the second comparator U2, that is, when t5 is reached, the second The comparator U2 may output the lower limit control signal LL to the switch controller 32 and turn the third switch SW3 ON so that the number of LEDs driving the switch controller 32 is reduced. . In this case, the fourth LED group G4 is turned off, and only the first to third LED groups G1, G2, and G3 are driven.

에서

로 변경될 수 있다.
At this time, since the number of LEDs driven is instantaneously reduced, accordingly, the LED driving voltage Vf decreases and the driving current If temporarily increases, that is, the driving current If at t5 is

in

. &Lt; / RTI &gt;

Next, looking at the operation of the period t5 ~ t6, the increased driving current (If) is gradually reduced with the decrease in the DC power supply voltage (V1) past the peak (peak). In this case, when the voltage Vd detected by the driving current If is between the first and second reference signals VR2 (VR2 <Vd <VR1), the first to third switches SW1, SW2, and SW3. ) Is maintained as it is, and when the driving current If decreases and the voltage detected by the current has a value smaller than the second reference signal VR2 (t6), the second comparator U2 switches to the switch controller ( 32, the lower limit control signal LL can be output.

At this time, according to the lower limit control signal LL input from the second comparator U2, the switch controller 32 turns off the third switch SW3 in the ON state so that fewer LEDs are driven. The second switch SW2 in the OFF state can be turned ON so that only the first and second LED groups G1 and G2 are driven.

에서

로 변경될 수 있다.Next, looking at the operation in the period t6 ~ t7, the driving voltage (Vf) of the LED as the third switch (SW3) is turned off (OFF) at t6, the second switch (SW2) is turned on (ON) This decrease causes the drive current If to increase instantaneously. Specifically, the driving current If at t6 is

in

. &Lt; / RTI &gt;

에서

로 변경될 수 있다.
As in the periods t5 to t6, the increased driving current If decreases together as the rectified DC power supply voltage V1 decreases, and the second comparator U2 switches to the lower limit control signal LL. At the time t7 of generating the second switch SW2 is turned off and the first switch SW1 is turned on, the second LED group G2 is not operated. At this time, the driving current If at t7 is

in

. &Lt; / RTI &gt;

Next, referring to the operation in the period t7 to t8, only the first LED group G1 is driven by the operation of the first and second switches SW1 and SW2 at t7, and the DC power voltage V1 is further increased. When the first LED group G1 is turned off, the first LED group G1 is turned off.

Since the rectified DC power supply voltage V1 increases again after passing the lowest point, the operation of the period t1 to t8 is repeated thereafter.

In the present embodiment, one of the first to third switches SW1, SW2, and SW3 constituting the switch 33 is either ON or OFF, and two or more switches are simultaneously It is not turned ON. However, when the nth switch is ON, whether the ON / OFF switch of the n + 1th or later switch is turned on does not affect the operation of the driving circuit.

As shown in FIG. 3 (b), as the rectified DC power supply voltage V1 increases, the first to third switches SW1, SW2, and SW3 are sequentially turned ON, and then all are OFF. When the rectified DC voltage V1 begins to decrease past the peak, the first switch SW1 is sequentially turned ON.

Accordingly, when the rectified DC power supply voltage V1 increases, the first to fourth LED groups G1, G2, G3, and G4 are sequentially turned on (here, sequentially turned on). It does not mean that the second LED group G2 is turned on after G1 is turned off, but the second to fourth LED groups G2, G3, and G4 are lit in addition to the first LED group G1.) In the period where the rectified DC power supply voltage V1 decreases, the fourth to first LED groups G4, G3, G2, and G1 are sequentially turned off.

According to the present embodiment, the drive current If flowing through the rectifying unit 10 is detected in accordance with the change of the rectified DC voltage V1, and the preset upper limit current value If (UL) and the lower limit current value If (LL)) and the detected drive current If, it is possible to adjust the number of LEDs driven by controlling the switch. In other words, it is possible to control different numbers of LEDs by sections using only switches and resistors without the need of a separate current driving circuit to drive different magnitudes of current in each section, so the configuration is simple and power consumption is reduced. It is possible to provide an LED driving circuit with improved power efficiency.

Unlike the present embodiment, the first to fourth LED groups G1, G2, G3, and G4 are driven in order to drive different numbers of LED groups according to the magnitude of the rectified DC power supply voltage V1. The method of controlling the switch according to the magnitude of the driving voltage of each of the to fourth LED groups G1, G2, G3, and G4 may be applied.

Specifically, the first switch SW1 is turned on when the rectified DC power supply voltage V1 is between the driving voltage of the first LED group G1 and the driving voltages of the first and second LED groups G1 and G2. (ON) so that a current passes through only the first LED group G1 and flows to ground GND, and the rectified DC power supply voltage V1 drives the driving voltages of the first and second LED groups G1 and G2. At a larger time t2, the first switch SW1 is turned off and the second switch SW2 is turned on so that the driving current If is the first and second LED groups G1 and G2. Control to flow to ground (GND).

In this case, however, since each LED has a tolerance in driving voltage, the control point of the switch must be designed in consideration of this. That is, when the average driving voltage of the LED group is called Vf (typical) and the maximum driving voltage in the tolerance is Vf (max), the threshold voltage of the switch is set based on Vf (typical). In this case, the LED group may not light up depending on the operation of the switch.

For example, in FIG. 2, when the second switch SW2 is turned on and the first and second LED groups G1 and G2 are driven, the rectified power supply voltage V1 is first to first. Assume that the third switch SW3 is turned on when the average value Vf (typical) of the driving voltages for the three LED groups G1, G2, and G3 is reached. At this time, when the driving voltage of the third LED group G3 has Vf (max) which is the maximum value within the tolerance, the rectified DC power supply voltage V1 is set to 3rd even if the third switch SW3 is turned ON. Since the driving voltage Vf (max) of the LED group G1 has a value smaller than that, the first to third LED groups G1, G2, and G3 may not be driven.

Therefore, in order to prevent such a phenomenon, the threshold voltage value of the switch is designed based on the maximum driving voltage value Vf (max) within the tolerance range for the entire first to fourth LED groups G1, G2, G3, and G4. Should be. That is, when n switches, the threshold voltage for driving the n-th LED group should be set to n × Vf (max) (the first to n-th LED groups each have one LED having the same driving voltage as Vf. If included), the power loss due to the tolerance of the driving voltage (Vf (max)-Vf (min)) increases in proportion to the number of switches (n), so that the power efficiency decreases as the number of switches increases Occurs.

In addition, each switch must be controlled in accordance with the driving voltage, so as many comparators as the number of switches, a circuit for detecting an on / off state of each switch, and a current driving for driving a different current according to the state of the switch. Circuitry is required, which complicates the circuit configuration, and additionally requires power for driving each circuit.

On the other hand, in order to miniaturize the driving circuit, a circuit portion for driving the current must be embedded in the integrated circuit (IC), but since the driving current flows inside the IC, a large power consumption is generated in the integrated circuit, which is thermally disadvantageous. There is a limit to the power consumption of the IC. Therefore, it is difficult to operate in an environment with high ambient temperature, and it is difficult to cope with high power in one unit.

However, in the light emitting device according to the exemplary embodiment of the present invention illustrated in FIG. 2, the driving flows through the light source unit 20 instead of directly detecting and controlling the state of each switch according to the driving voltage of each LED group. Each switch can be automatically controlled by detecting the magnitude of the current If.

That is, since the switch is not controlled in consideration of the magnitude of the driving voltage of each LED group, power loss does not occur due to an increase in the number of switches, thereby providing a high-efficiency light emitting device.

Also, instead of requiring a separate comparator or op amp for each of the first to nth LED groups, the driving current is between the upper limit current value If (UL) and the lower limit current value If (LL). Only two comparators (U1, U2) or op amps can be provided for comparing the presence. Meanwhile, the plurality of LED groups may be individually driven and controlled by a simple circuit including only a switch and a resistor without requiring a separate current driving circuit for driving a preset current for each of the first to nth LED groups.

In addition, in the present embodiment, since the driving current If does not flow into the integrated circuit IC, the power consumption and the heat generation are low, so that the operation in the high temperature environment is advantageous, and therefore, the operation in the high temperature environment is advantageous. . In addition, since the resistor and the switch (for example, the FET) are located outside the integrated circuit (IC), the design freedom is high and the unit can cope with a relatively wide range of power in one unit.

In addition, when the same power is required for the external commercial power supply of the 200V system and the 100V system, the driving current If is approximately doubled in the 100V system when compared with the 200V system. Therefore, in order to apply the same integrated circuit (IC) to the 200V series and the 100V series, there is a problem in that the cost increases and the size of the circuit increases.

However, in the case of the present embodiment, since the drive current If does not flow into the integrated circuit IC, the design of the integrated circuit IC which can be applied to both 200V and 100V power sources is easy.

4 is a view schematically showing a light emitting device 101 according to another embodiment of the present invention, and FIG. 5 is a view showing waveforms of voltages and currents that can be driven by the light emitting device 101 shown in FIG. 4. 6 is a view for explaining the operation of the light emitting device shown in FIG.

First, referring to FIG. 4, the light emitting device 101 according to the present embodiment includes a rectifying unit 10 ′ for converting AC power input from the outside into a DC power source, and a DC power source converted by the rectifying unit 10 ′. A light source unit 20 'including first to fifth LED groups G1, G2, G3, G4, and G5 sequentially connected to each other and driven to control the current flowing through the first to fifth LED groups. It may include a control unit 30 ′.

The driving controller 30 ′ compares an input signal generated by detecting a current flowing in the light source unit 20 ′ with a reference signal and outputs a switch control signal, and outputs from the comparator 31 ′. The switch controller 32 ′ for receiving the switch control signal inputted to control the switch on / off and the output terminal of the first to fifth LED groups G1, G2, G3, G4, and G5. And a switch 33 'for changing the path of the driving current by the signal input from the 32'.

In the present embodiment, the flicker prevention circuit may be further included in the driving controller 30 of the light emitting device 100 according to the embodiment shown in FIG. 2.

4 and 5, the light emitting device 101 according to the present embodiment may be driven in a similar manner to the light emitting device 100 shown in FIGS. 2 and 3 except for the period t5 to t6.

Specifically, in the voltage and current waveforms shown in FIG. 5, the sections t1 to t4 are similar to the sections t1 to t4 shown in FIG. 3, and the sections t7 to t10 are driven in a similar manner to the sections t5 to t8 shown in FIG. 3. Since there is a difference in operation only in a section t4 to t7 including a peak of the rectified DC power supply voltage V1, only the operation in t3 to t7 will be briefly described.

First, when the voltage Vd detected by the driving current If decreased in the period t3 to t4 is between the first reference signal VR1 and the second reference signal VR2, that is, VR2 <Vd <VR1. In this case, the driving current If flows through the first to third LED groups G1, G2, and G3.

As the rectified DC power supply voltage V1 increases, the driving current If gradually increases, and when the voltage Vd detected by the driving current If becomes greater than the first reference voltage VR1 (t4), The switch controller 32 sets the third switch SW3 to OFF and the fourth switch SW4 to ON so that the driving current If is the first to fourth LED groups G1 and G2, It can be made to flow through G3 and G4).

Next, referring to the operation of the sections t4 to t7 except t5 to t6, the fourth switch SW4 is turned ON at t4 and the voltage Vd detected by the drive current If in the comparator 31. ) Is between the first reference voltage VR1 and the second reference voltage VR2, the fourth switch SW4 is kept in an ON state.

Compared with the waveform shown in FIG. 3, in FIG. 3C, the third switch SW3 is turned OFF, so that all the switches are OFF, while in FIG. 4C, the third switch ( SW3) is OFF and the fourth switch OFF is ON, but there is a difference in that it is an operation for driving the fourth LED group G4.

When the DC power supply voltage V1 rectified at t4 to t7 begins to decrease past the peak, the driving current If also decreases as the DC power supply voltage V1 decreases. When the voltage Vd detected by the reduced driving current If becomes smaller than the second reference signal VR2 of the second comparator U2, that is, reaches t7, the second comparator U2 is a switch controller. Outputs the lower limit control signal LL to (32), turns off the fourth switch (SW4) and turns on the third switch (SW3) so that the number of LEDs driving the switch controller 32 is reduced. ON). In this case, the fourth LED group G4 is turned off, and only the first to third LED groups G1, G2, and G3 are driven.

Since the operation is described above with reference to FIGS. 2 and 3 will be omitted.

Referring to the waveform of the driving current If shown in the lower part of FIG. 5A, the driving current If in the period t4 to t7 where the rectified DC power supply voltage V1 includes a peak is a current. It is kept below the upper limit UL.

However, due to the fluctuation of the rectified DC power supply voltage V1 or the tolerance of the driving voltage Vf of each LED group, the driving current If occurs accidentally at the peak of the DC power supply voltage V1. If the same as the Upper Limit (If = If (UL)) of the first comparator U1 may occur.

In particular, when the number of switches is increased to increase driving efficiency, the driving voltage (LED total Vf) of the LED group and the waveform of the rectified DC power supply voltage (V1) are as close as possible, driving efficiency is increased while the peak of the voltage ( In the section including the peak, the case where the driving current If becomes equal to the upper limit current value If (UL) of the first comparator U1 increases.

In this case, as shown in FIG. 6A, the first comparator U1 generates an upper limit control signal UL to the switch controller 32 to change the operation of the switch to proceed to the next step, or FIG. 6 ( As shown in b), the previous step may be maintained without generating the upper limit control signal UL.

At this time, if it is fixed to one of the operations to proceed to the next step (Fig. 6 (a)) or the previous step is maintained (Fig. 6 (b)), there is no problem, but proceeds to the next step in one cycle and the previous step in the next cycle When different waveforms shown in FIGS. 6 (a) and 6 (b) alternately appear, the brightness change becomes a frequency lower than 120 Hz or 100 Hz, so that the human eye can be recognized as a flicker.

Hereinafter, the operation of the circuit shown in FIGS. 6 (a) and 6 (b) will be described in detail.

First, referring to FIG. 6 (a), the operation at t1 'to t4' is similar to the operation at t1 to t4 in FIG. 5 (a), but the first to fourth LED groups (t4 'to t5') When the driving current If is equal to the upper limit of the first comparator U1 when the driving devices G1, G2, G3, and G4 are driven, the first to fourth switches SW1, SW2, SW3 and SW4 are turned off to drive the first to fifth LED groups G1, G2, G3, G4, and G5.

When the number of LEDs to be driven increases, the driving current If decreases instantaneously (t5 '). In the period t5 'to t6', as the rectified power supply voltage V1 decreases past the peak, the driving current If also decreases, and the driving current If is smaller than the lower limit of the second comparator U2. By the lower limit control signal LL output from the second comparator U2, the switch controller 32 turns on the fourth switch SW4 to be ON so that fewer LEDs are driven. The operation after t6 'is similar to the operation after t7 in FIG.

Meanwhile, in the case of FIG. 6B, except for the period t5 to t6 of FIG. 5, the operation is similar to that of FIG. 5, and the fifth LED group G5 is not turned on.

Therefore, when the first upper limit control signal UL is generated in the first comparator U1 in order to prevent a flicker phenomenon caused by irregularly appearing waveforms shown in FIGS. 6A and 6B. In the section from (t2) to the first lower limit control signal LL in the second comparator U2, the upper limit control signal in the first comparator U1 for a predetermined period (t4 to t5 in Fig. 5 (a)) In the case where UL) does not occur, the flicker phenomenon can be suppressed by forcibly generating a dummy pulse to proceed to the next step.

That is, when the driving current If becomes equal to the upper limit current value If (UL) detected by the first comparator U1, the process proceeds to the next step so that the waveform shown in FIG. It is possible to prevent flicker caused by showing different waveforms.

The drive control part 30 ′ according to the present embodiment has a range from the time t2 at which the first signal UL occurs at the first comparator U1 to the time at which the first signal LL occurs at the second comparator U2. When the signal UL does not occur in the first comparator U1 for a predetermined period, a dummy pulse is generated from the first comparator U1 (t5 to t6), whereby the rectified DC power supply voltage V1 is generated. An operation for preventing flicker may be performed within the highest section t4 to 47.

As shown in FIG. 5, within a section including a peak of the rectified DC power supply voltage V1 (a section in which the largest number of LED groups can drive), the driving current If is the first. Regardless of whether the upper limit UL of the comparator U1 is equal to the upper limit UL, if the step change is forcibly performed when there is no step change for a predetermined time t4 to t5, the fifth group of LEDs G5 within one period Since it is always lit, flicker can be alleviated.

In this case, as shown in FIG. 5, even when the driving current operates within the current range defined by the upper limit UL and the lower limit LL, the fifth LED group G5 is driven at the predetermined time point t5. By forcibly turning off all the switches so that the driving current flows through the first to fifth LED groups G1, G2, G3, G4, and G5, and by the fifth LED group G5. As the driving voltage Vf increases, the driving current If decreases. When the reduced driving current If is smaller than the lower limit If (LL) of the second comparator U2, the switch controller 32 controls the switch in a direction in which the number of LEDs to be driven is reduced so that the fourth switch SW4 can be used. ) Is turned ON, and proceeds to the next steps t6 to t7 where the first to fourth LED groups G1, G2, G3, and G4 are driven.

That is, in the present embodiment, a dummy pulse is forcibly generated in the section including the peak of the rectified power supply voltage V1 to proceed to the next step, and accordingly, each step goes to the next step. It is possible to suppress the flicker phenomenon that occurs when the progression or non-progression appears differently.

Although the above description has been made with reference to a light emitting device including a light source unit, another aspect of the present invention may provide a power supply device and a driving device for supplying driving power to the light source unit.

The power supply device supplies driving power to the light source unit, and detects a current flowing in the light source unit to control the number of light sources driven by the light source unit when it is out of a preset current range.

The power supply device may be understood as a configuration excluding the light source units 20 and 20 ′ from the light emitting devices 100 and 101 illustrated in FIGS. 2 and 4. The rectifiers 10 and 10 'may not be included.

In addition, another aspect of the present invention may include a driving device (IC) for driving the light source unit (20, 20 '), the driving device (IC) by comparing the input signal and the reference signal to a predetermined current Comparators outputting a control signal when out of the range and a control signal output from the comparator are input, and when the control signal is input, it may be provided with a switch controller for outputting a signal for changing the number of light sources to drive.

In this case, the driving device IC includes an IC region (voltage regulator, switch controller 32, comparator 31) indicated by dotted lines in the light emitting devices 100 and 101 according to the embodiment shown in FIGS. 2 and 4. It may be understood that the voltage regulator may be omitted as necessary.

The present invention is not limited by the above-described embodiments and the accompanying drawings, but is intended to be limited only by the appended claims. It will be apparent to those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims. something to do.

100, 101: light emitting device 10, 10 ': rectifier
20, 20 ': light source unit 30, 30': drive control unit
31, 31 ': comparator 32, 32': switch controller
33, 33 ': switch

Claims (28)

A light source unit driven by a DC power source and including first to n th LED groups sequentially connected in series; And
And a driving controller detecting the current flowing through the output terminal of the light source unit and changing the number of LED groups driven by the light source unit when the current flowing through the output terminal of the light source unit is outside the preset current range to have an upper limit and a lower limit.
The drive control unit may include:
First to mth switches turned on / off to change the number of LED groups driven by the light source unit, and connected to at least some of the output terminals of the first to nth LED groups;
A comparator for outputting an upper or lower limit control signal when the input signal generated by detecting a current flowing through the output terminal of the light source unit is out of the preset current range by comparing the input signal with a reference signal;
The control signal output from the comparator is input, and when the upper limit control signal is input, the signal for sequentially increasing the number of LED groups to be driven; A light emitting device comprising a switch controller for outputting to the first to m-th switch.
Where n is n

Natural number satisfying 2, m is 2

m

is a natural number satisfying n)
The method of claim 1, wherein the drive control unit,
And detecting an electric current flowing through an output terminal of the light source unit to generate an input signal, and comparing the input signal with a reference signal to determine whether the predetermined current range is exceeded.
delete delete The method of claim 1, wherein the switch controller,
And outputting a signal for controlling the number of LED groups to be driven when the upper limit control signal is input, and for controlling the number of LED groups to be driven when the lower limit control signal is input.
delete delete delete delete The method of claim 1,
The comparator further comprises a current detection resistor connected between the output terminal of the light source and the ground, wherein the input signal is generated in the form of a voltage by the current detection resistor.
The method of claim 10,
And the first to m-th switches are first to n-th switches connected between the output terminals of the first to n-th LED groups and the current detection resistor, respectively.

delete Claim 13 was abandoned upon payment of a registration fee. The method of claim 1,
Light emitting device further comprises a rectifier for converting AC power input from the outside into DC power.
Claim 14 has been abandoned due to the setting registration fee. The method of claim 13,
The rectifier comprises a bridge diode (bridge diode).
Claim 15 is abandoned in the setting registration fee payment. The method of claim 1,
And the first to n-th LED groups each include at least one LED.
Claim 16 has been abandoned due to the setting registration fee. 16. The method of claim 15,
At least one of the first to n-th LED group includes a plurality of LEDs, the plurality of LEDs, characterized in that the electrical connection of any one of the form of a series, parallel and parallel and parallel.
Detecting a current flowing through an output terminal of the first to nth LED groups sequentially connected to the rectified DC power source;
Setting a range of driving currents having an upper limit and a lower limit to control a current flowing through an output terminal of the first to nth LED groups; And
And controlling the number of LED groups to be driven when the current detected from the output terminal of the first to nth LED groups is out of the range of the preset driving current to have the upper limit and the lower limit.
The number of driving LED groups is changed by turning on / off first to mth switches connected to at least some of the output terminals of the first to nth LED groups,
Outputting an upper limit control signal when the detected current is larger than an upper limit of the set driving current range, and outputting a lower limit control signal when smaller than the lower limit;
And sequentially increasing the number of LED groups driven when the upper limit control signal is output, and sequentially decreasing the number of LED groups driven when the lower limit control signal is input.
Where n is n

Natural number satisfying 2, m is 2

m

is a natural number satisfying n) delete 18. The method of claim 17,
The controlling of the number of driving LED groups to be changed may include:
When the current flowing through the first to n-th LED groups is greater than the upper limit, the number of LEDs to be driven is increased. When the current flowing through the first to n-th LED groups is smaller than the lower limit, the number of LEDs to be driven is reduced. LED driving method, characterized in that the control.
18. The method of claim 17,
The controlling of the number of driving LED groups to be changed may include:
And controlling the current detected from the first to nth LED groups to decrease or increase instantaneously when a current detected from the first to nth LED groups is out of a range of a predetermined current. .
18. The method of claim 17,
When the current flowing through the first to nth LED groups is greater than the upper limit, the current detected from the first to nth LED groups decreases instantaneously,
And controlling the current detected from the first to nth LED groups to increase instantaneously when the current flowing through the first to nth LED groups is smaller than the lower limit.
delete delete 18. The method of claim 17,
The first to n-th LED group is characterized in that after the first to the n-th LED group is sequentially turned on in the driving period of the DC power source, the n-th to the first LED group is controlled to turn off sequentially. LED driving method.
Claim 25 is abandoned in setting registration fee. 25. The method of claim 24,
The LED driving method, characterized in that the first to n-th LED group in the lighting state when the n-th LED group is turned on in the section that is sequentially lit from the first LED group to the n-th LED group.
Claim 26 is abandoned in setting registration fee. 18. The method of claim 17,
LED driving method characterized in that the current flowing in the first to n-th LED group is detected in the form of a voltage.
Claim 27 is abandoned due to the setting registration fee. 18. The method of claim 17,
The current flowing through the first to n-th LED group is detected at the output terminal of the n-th LED group.
Claim 28 has been abandoned due to the set registration fee. 18. The method of claim 17,
Fully rectifying the AC power input from the outside to convert the LED power source.

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