WO2013137678A1

WO2013137678A1 - Driving device for light-emitting device

Info

Publication number: WO2013137678A1
Application number: PCT/KR2013/002096
Authority: WO
Inventors: 이정훈; 이성진; 이종국; 최재영
Original assignee: 서울반도체 주식회사
Priority date: 2012-03-15
Filing date: 2013-03-15
Publication date: 2013-09-19
Also published as: KR20130104800A

Abstract

The present invention relates to a driving device for a light-emitting device comprising: a filter unit which receives an alternating current voltage, and which outputs the voltage by removing noise; a rectifying unit which rectifies the output of the filter unit, and which outputs a driving voltage; a compensation unit which removes noise of an input current corresponding to the alternating current voltage, and which transfers the driving voltage to a light-emitting device by compensating for the size of the driving voltage; and a constant current unit for constantly maintaining a current flowing into the light-emitting device, thereby improving a power factor and total harmonics distortion characteristics, driving the light-emitting device using a constant current, and at the same time, reducing flicker.

Description

Light emitting element drive

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light emitting element driving apparatus, and more particularly to a light emitting element driving apparatus driven by an AC voltage.

In general, incandescent lamps or fluorescent lamps are widely used as indoor or outdoor lighting lamps, and these incandescent lamps or fluorescent lamps have a short life and have a problem of frequent replacement. In order to solve this problem, a lighting apparatus using light emitting diodes having excellent controllability, fast response speed, high electro-optical conversion efficiency, long life, low power consumption and high luminance has been developed.

Since the light emitting diode is usually driven at a small current of several tens of mA, when the light emitting diode is directly connected to an AC voltage, the current is not limited because the current is not limited. There was a problem that is easily broken. Therefore, an AC / DC converter for converting an AC voltage into a low DC voltage or the like is used, or a circuit for limiting current using a rectifier circuit and a resistor is used.

1 is a circuit diagram showing a light emitting device driving apparatus according to the prior art.

Referring to FIG. 1, a conventional light emitting device driving apparatus includes a rectifier 10, a capacitor C1, and a resistor R1. The rectifier 10 receives an AC voltage Vac and rectifies and outputs it. The capacitor C1 charges and discharges the voltage output from the rectifier 10. The resistor R1 restricts the magnitude of the current corresponding to the voltage output from the rectifier 10 and the voltage Vc charged in the capacitor C1 and supplies it to the light emitting diode L1.

2 is a waveform diagram illustrating an operation of a light emitting device driving apparatus according to the prior art.

Referring to FIG. 2, the AC voltage Vac is full-wave rectified through the rectifier 10 and output. Next, when the voltage output from the rectifier 10 becomes equal to or greater than the forward voltage Vf of the light emitting diode L1, a current Iled flows through the resistor R1 through the light emitting diode L1. At the same time, the voltage Vc starts to be charged across the capacitor C1. At this time, the capacitor C1 is charged with the voltage Vc from the time when the AC voltage Vac becomes equal to or greater than the forward voltage Vf of the light emitting diode L1, and the voltage Vc from the time when the AC voltage Vac falls. ) Is discharged. Accordingly, there is a problem in that the waveform of the input current Iin is distorted, thereby degrading power factor and total harmonic distortion. In addition, the ripple of the current Iled flowing in the light emitting diode L1 is large, so that the flicker phenomenon of the light emitting diode L1 is severely seen. In order to solve this problem, when the capacitor C1 uses an electrolyte capacitor having a capacity of several tens of μF, the size of the circuit is increased and the life of the circuit is shortened due to the life of the electrolyte capacitor.

In addition, when using a constant current IC to control the constant current flows to the light emitting diode (L1), a separate constant current control circuit for control is required, there is a problem that the price increases.

An object of the present invention is to improve the power factor, total harmonic distortion and power efficiency of a light emitting device driving apparatus for driving a light emitting diode using an AC voltage.

In addition, an object of the present invention is to make the current driving the light emitting device as close to the direct current as possible to suppress the flicker of the light emitting device using a small capacity capacitor for the ripple filter.

It is also an object of the present invention to drive a light emitting device with a constant current without using a complicated switching power supply circuit or a constant current control circuit that detects and feeds back a current.

The present invention includes a filter unit for receiving an AC voltage to remove noise and output it; A rectifying unit rectifying the output of the filter unit to output a driving voltage; A compensator which removes noise of an input current corresponding to the AC voltage and compensates the magnitude of the driving voltage and transmits the magnitude of the driving voltage to the light emitting device; And a constant current unit for maintaining a constant current flowing through the light emitting device. Here, the compensation unit compensates the rising and falling slope of the input current flowing through the filter unit, the compensation unit to charge and discharge the driving voltage to compensate for the light emitting period of the light emitting device, the compensation unit of the light emitting device It characterized in that to remove the turn off period.

The filter unit may include a low pass filter, and the AC voltage may be input through first and second AC input terminals, and the filter unit may include first and second connected to the first and second AC input terminals, respectively. resistance; And a first capacitor connected between the first and second resistors. The driving voltage may be output through first and second driving voltage output terminals, and the rectifying unit may include a cathode terminal connected to the first driving voltage output terminal and an anode terminal connected to one end of the first capacitor. 1 diode; A cathode diode connected to the first driving voltage output terminal and a second diode connected to the other end of the first capacitor; A third diode including a cathode terminal connected to one end of the first capacitor and an anode terminal connected to the second driving voltage output terminal; And a fourth diode including a cathode terminal connected to the other end of the first capacitor and an anode terminal connected to the second driving voltage output terminal. The compensation unit may include at least one charge / discharge device connected between the first and second driving voltage output terminals. The compensator includes a second capacitor including one end connected to the second driving voltage output terminal and the other end connected to a node to which an anode terminal of the second diode and a cathode terminal of the fourth diode are commonly connected; And a third capacitor including one end connected to the node and the other end connected to the second driving voltage output terminal.

The constant current unit may include a constant current diode connected to the light emitting device, and the constant current unit further includes a current compensation device configured to compensate for a current flowing through the light emitting device to have a current component having a phase angle equal to the driving voltage. The current compensating device may include a resistor connected in parallel with the constant current device.

The present invention provides the effect of improving the power factor, total harmonic distortion and power efficiency.

In addition, the present invention provides an effect of suppressing the flicker of the light emitting device by using a capacitor for a small capacity ripple filter and improving the LED lifetime by lowering the peak value of the current driving the light emitting diode.

In addition, the present invention provides the effect of miniaturizing the light emitting device driving apparatus by driving the light emitting device at a constant current without using a switching power supply circuit or a complex feedback constant current control circuit.

Figure 2 is a waveform diagram for explaining the problem of the light emitting device driving apparatus according to the prior art.

3 is a circuit diagram showing a light emitting device driving apparatus according to an embodiment of the present invention.

4 is a waveform diagram illustrating an operation of a light emitting device driving apparatus according to an embodiment of the present invention.

5 is a circuit diagram showing a light emitting device driving apparatus according to another embodiment of the present invention.

6 is a waveform diagram illustrating an operation of a light emitting device driving apparatus according to another exemplary embodiment of the present invention.

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

3 is a circuit diagram illustrating a light emitting device driving apparatus according to an embodiment of the present invention.

Referring to FIG. 3, the light emitting device driving apparatus 100 of the present invention includes a filter unit 110, a rectifying unit 120, a compensating unit 130, and a constant current unit 140. The filter unit 110 receives the AC voltage Vac through the first AC input terminal A1 and the second AC input terminal A2, removes the noise, and outputs the noise. Here, the second AC input terminal A2 is connected to the ground terminal GND. In detail, the filter unit 110 includes a first resistor R11, a second resistor R12, and a first capacitor C11. The first resistor R11 is connected between the first AC input terminal A1 and one end of the first capacitor C11, and the second resistor R12 is the second AC input terminal A2 and the capacitor C11. It is connected between the other ends of. Here, the first and second resistors R11 and R12 preferably have a size of several hundred Ω. The first and second resistors R11 and R12 and the first capacitor C11 according to the embodiment of the present invention may constitute a low pass filter (LPF). In addition, the first and second resistors R11 and R12 and the second and third capacitors C12 and C13 may be configured to remove ripples of the input current Iin. This will be described in detail below.

The rectifier 120 receives the AC voltage Vac through the filter 110 and rectifies the rectifier 120 to output the driving voltage Vrec through the first and second driving voltage output terminals B1 and B2. To this end, the rectifier 120 includes a full-wave rectifier circuit composed of the first to fourth diodes D1 to D4. Here, the first diode D1 includes a cathode terminal connected to the first driving voltage output terminal B1 and an anode terminal connected to one end of the first capacitor C11. The second diode D2 includes a cathode terminal connected to the first driving voltage output terminal B1 and an anode terminal connected to the other end of the first capacitor C11. The third diode D3 includes a cathode terminal connected to one end of the first capacitor C11 and an anode terminal connected to the second driving voltage output terminal B2. The fourth diode D4 includes a cathode terminal connected to the other end of the first capacitor C11 and an anode terminal connected to the second driving voltage output terminal B2.

The compensator 130 compensates for the light emission period of the light emitting device L11 by charging and discharging the driving voltage Vrec. In addition, the compensation unit 130 compensates for the rising and falling slope of the input current Iin flowing through the filter unit 110 to mitigate the ripple of the input current Iin. To this end, the compensator 130 includes second and third capacitors C12 and C13. Here, the second capacitor C12 has a node N1 in which one end connected to the second driving voltage output terminal B1 and the anode terminal of the second diode D2 and the cathode terminal of the fourth diode D4 are commonly connected. It includes the other end connected to. The third capacitor C13 includes one end connected to the node N1 and the other end connected to the second driving voltage output terminal B2. The second and third capacitors C12 and C13 according to an embodiment of the present invention are preferably configured of a multilayer ceramic capacitor (MLCC) having a size of several μF. In this case, the lifetime is less limited than that of the conventional electrolyte capacitor, and the circuit can be miniaturized.

Meanwhile, in the exemplary embodiment of the present invention, the case in which the compensator 130 includes two capacitors has been described as an example. However, the present invention is not limited thereto, and the first and second driving voltage output terminals B1 and B2 are not limited thereto. One capacitor connected between them can be used.

In addition, the constant current unit 140 controls the current Iled to flow through the light emitting device L11. To this end, the constant current unit 140 includes a constant current element J1 and a third resistor R13. The constant current device J1 includes an anode terminal connected to the light emitting element L11 in series and a cathode terminal connected to one end of the third resistor R13. The constant current device J1 according to the embodiment of the present invention includes a constant current diode (CRD). The constant current diode has a characteristic of supplying a constant current in response to a change in input voltage, temperature, and the like, and does not require a separate switching element, so that a circuit can be easily configured. However, the embodiment of the present invention is not limited thereto, and the constant current device J1 may be configured by using another device such as a FET. The other end of the third resistor R13 is connected to the second driving voltage output terminal B2. The third resistor R13 limits the magnitude of the voltage across the constant current device J1 so that the constant current device J1 operates stably. The present invention is not limited thereto, and a diode may be used instead of the third resistor R13, and the third resistor R13 may be omitted.

Meanwhile, the light emitting device L11 illustrated in FIG. 3 includes a light emitting diode, and only one light emitting diode is illustrated for convenience of description. However, the present invention is not limited thereto, and the number of light emitting diodes may be changed. The light emitting diodes of may be connected in series or in parallel. In addition, the light emitting diode L11 according to the embodiment of the present invention is preferably a white light emitting diode. However, the present invention is not limited thereto and may include a light emitting diode that emits red, blue, green, yellow, and the like instead of white.

4 is a waveform diagram illustrating an operation of a light emitting device driving apparatus according to an embodiment of the present invention. FIG. 4A illustrates second and third voltages such that the voltage when the second and third capacitors C12 and C13 shown in FIG. 3 is charged is greater than the forward voltage Vf of the light emitting element L11. The case where the capacitance of the capacitors C12 and C13 is selected is shown. (B) shows that the voltage when the second and third capacitors C12 and C13 are charged is the forward voltage of the light emitting element L11. The case where the capacitances of the second and third capacitors C12 and C13 are selected to be smaller than Vf) is shown.

Referring to FIG. 4, the AC voltage Vac is input to the filter unit 110 through the first AC input terminal A1 and the second AC input terminal A2. First, the AC voltage Vac is output after the high frequency component is removed through the first resistor R11 and the first capacitor C11 during the half period of the positive voltage of the AC voltage Vac. Next, the AC voltage Vac is rectified by the first diode D1 and the fourth diode D4, and the driving voltage Vrec is output through the first and second driving voltage output terminals B1 and B2. . At the same time, a constant voltage starts to be charged across the second capacitor C12. As a result, the driving voltage Vrec is compensated to a magnitude higher than the effective value of the AC voltage Vac, thereby accelerating the time when the driving voltage Vrec rises above the forward voltage Vf of the light emitting element L11. That is, the period in which the driving voltage Vrec becomes equal to or higher than the forward voltage Vf of the light emitting element L11 is long, so that the turn-on period of the light emitting element L11 increases.

Then, when the light emitting element L11 is turned on and the current Iled starts to flow, the current Iled is limited to a constant size through the constant current element J1. Then, the voltage charged across the second capacitor C12 starts to be discharged. Here, when the capacitance of the second capacitor C12 is selected such that the voltage at the time of charging the second capacitor C12 is greater than the forward voltage Vf of the light emitting device L11, for example, the capacitance of the second capacitor C12 is 4.7. If μF, the current Iled flowing through the light emitting element L11 has a direct current waveform without ripple, as shown in Fig. 4A. On the other hand, when the capacitance of the second capacitor C12 is selected such that the voltage at the time of charging the second capacitor C12 is smaller than the forward voltage Vf of the light emitting element L11, for example, the capacitance of the second capacitor C12 is 2.2. If μF, the current Iled flowing in the light emitting element L11 has a ripple component for some periods, as shown in Fig. 4B. However, even in this case, since the size of the ripple component is reduced as compared with the related art, the phenomenon that the light emitting element L11 flickers can be suppressed. In addition, since the section in which the light emitting device L11 is turned off is removed, the light emission efficiency may increase.

On the other hand, the input current Iin is the first resistor R11, the first diode D1, the second diode and the third capacitor from the first AC input terminal A1 during a half period of the positive voltage of the AC voltage Vac. (C12, 13), and flows in the direction of the second AC input terminal A2 via the fourth diode D4. That is, the input current Iin slowly rises in response to the charging of the first capacitor C12, and slowly falls in response to the discharge of the first capacitor C12 by turning on the light emitting element L11. That is, the input current Iin flows in a form similar to the waveform of the AC voltage Vac. As a result, power factor and total harmonic distortion characteristics may be improved.

Next, the same operation as described above is performed even during the negative half period of the AC voltage Vac. As a result, the driving voltage Vrec is compensated by the second and third capacitors C12 and C13 so that the turn-off period of the light emitting element L11 is eliminated, and the turn-on period in which ripple is suppressed increases.

5 is a circuit diagram illustrating a light emitting device driving apparatus according to another exemplary embodiment of the present invention. The filter unit 110, the rectifying unit 120, and the compensating unit 130 of the light emitting device driving apparatus 100_1 illustrated in FIG. 5 are the same as those shown in FIG. 3, and are illustrated with the same reference numerals. Omit. Here, the configuration of the constant current unit 140_1 of FIG. 5 further includes a current compensating element connected in parallel with the constant current element J1.

Here, the current compensation device according to another embodiment of the present invention includes a fourth resistor (R14). The fourth resistor R14 includes one end connected to the light emitting element L11 and the other end connected to the second driving voltage output terminal B2. A current having a magnitude equal to the phase angle of the driving voltage Vrec and corresponding to the resistance value flows through the fourth resistor R14. That is, the current Iled, to which the current flowing through the constant current device J1 and the current flowing through the fourth resistor R14 is added, flows through the light emitting device L11. For example, when the current of 40 mA flows through the light emitting element L11, the current flowing through the constant current element J1 may be 30 mA, and the current flowing through the fourth resistor R14 may be 10 mA.

6 is a waveform diagram illustrating an operation of a light emitting device driving apparatus according to another exemplary embodiment of the present invention. The AC voltage Vac, the input current Iin, and the driving voltage Vrec shown in FIG. 6 are the same as in FIG. 4, and description thereof will be omitted. Hereinafter, the current Iled flowing through the light emitting element L11 will be described. Explain.

Referring to FIG. 6, when the driving voltage Vrec is greater than the forward voltage Vf of the light emitting device L11, the light emitting device L11 is turned on and current starts to flow. At this time, the constant current element J1 keeps the magnitude of the current constant. At the same time, current also begins to flow in the fourth resistor R14. As a result, the current Iled flowing in the light emitting element L11 includes a current component in a form similar to the driving voltage Vrec. As a result, the power efficiency of the light emitting device driving apparatus can be improved.

The present invention has been described above with reference to the above embodiments, but the present invention is not limited thereto. Those skilled in the art will appreciate that modifications and variations can be made without departing from the spirit and scope of the present invention and that such modifications and variations also fall within the present invention.

Claims

A filter unit which receives an AC voltage and removes and outputs noise;

A rectifying unit rectifying the output of the filter unit to output a driving voltage;

A compensator which removes noise of an input current corresponding to the AC voltage and compensates the magnitude of the driving voltage and transmits the magnitude of the driving voltage to the light emitting device; And

A light emitting device driving device comprising a constant current unit for maintaining a constant current flowing through the light emitting device.
The method according to claim 1,

And the compensating part compensates for the rising and falling slope of the input current flowing through the filter part.
The method according to claim 2,

And the compensator is configured to compensate for the light emission period of the light emitting device by charging and discharging the driving voltage.
The method according to claim 3,

And the compensator removes a turn-off period of the light emitting device.
The method according to claim 1,

And the filter part comprises a low pass filter.
The method according to claim 5,

The AC voltage is input through the first and second AC input terminals,

The filter unit,

First and second resistors connected to the first and second AC input terminals, respectively; And

And a first capacitor connected between the first and second resistors.
The method according to claim 6,

The driving voltage is output through the first and second driving voltage output terminal,

The rectifying unit,

A first diode including a cathode terminal connected to the first driving voltage output terminal and an anode terminal connected to one end of the first capacitor;

A cathode diode connected to the first driving voltage output terminal and a second diode connected to the other end of the first capacitor;

A third diode including a cathode terminal connected to one end of the first capacitor and an anode terminal connected to the second driving voltage output terminal; And

And a fourth diode including a cathode terminal connected to the other end of the first capacitor and an anode terminal connected to the second driving voltage output terminal.
The method according to claim 7,

The compensation unit,

And at least one charge / discharge device connected between the first and second drive voltage output terminals.
The method according to claim 8,

The compensation unit,

A second capacitor including one end connected to the second driving voltage output terminal and the other end connected to a node to which an anode terminal of the second diode and a cathode terminal of the fourth diode are commonly connected; And

And a third capacitor including one end connected to the node and the other end connected to the second driving voltage output terminal.
The method according to claim 1,

The constant current unit,

And a constant current diode connected to the light emitting device.
The method according to claim 10,

The constant current unit further comprises a current compensating element for compensating for the current flowing through the light emitting element to have a current component of the same phase angle as the driving voltage.
The method according to claim 11,

And the current compensating element comprises a resistor connected in parallel with the constant current element.