KR20150145025A - Apparatus for driving light emitting diode - Google Patents

Abstract

The present invention relates to a light-emitting diode driving device. In particular, the present invention relates to a light-emitting diode driving device capable of stably driving a light-emitting diode. According to the present invention, the light-emitting diode driving device comprises: a transformer including a first coil on a first side, and a second coil on a second side; a rectifying unit disposed on the first side of the transformer, and rectifying alternate current power to supply an output voltage to a light-emitting unit; a light-emitting unit connected to the second side of the transformer, and including one or more light-emitting diodes; a control unit disposed between one end of the rectifying unit and the transformer, and including a switch device and a control circuit for controlling the switch device so as to control output of the rectifying unit to be supplied to the light-emitting unit; and a ripple reducing unit disposed between the other end of the rectifying unit and the transformer, and including a coupling inductor and a capacitor to transfer output power of the rectifying unit to the transformer by using two different paths according to operation of the switch device.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light emitting diode driving apparatus, and more particularly, to a light emitting diode driving apparatus capable of stably driving a light emitting diode.

Recently, light emitting diodes (LEDs) having advantages such as efficiency, color diversity, and design autonomy have been attracting attention as a light source of illumination .

A light emitting diode is a semiconductor device that emits light when a voltage is applied in a forward direction, has a long lifetime, low power consumption, and has electrical, optical, and physical characteristics suitable for mass production.

In order to effectively use such a light emitting diode as a light source of illumination, a driving apparatus including a driving circuit capable of driving with commercial AC power is required.

In such a drive system, improvement of the power factor of the rectifier circuit and improvement of waveform such as harmonic elimination are important in terms of efficient utilization of energy.

To this end, a power factor correction circuit for reducing harmonic regulation and power loss and a DC-DC converter for controlling constant voltage and constant current are used in two independent stages to improve power factor Conversion method.

This power conversion scheme has the advantage that the power factor compensation and the output current control are independent of each other. However, since the circuit is complicated and the power is changed twice, the conversion efficiency is lowered.

In addition, since a bulk capacitor or a boost up inductor having a large element volume is used, it can not exceed the limit of miniaturization.

In order to overcome such disadvantages, the power factor correction circuit and the DC-DC converter can be implemented in a single stage, but the output current ripple is increased.

SUMMARY OF THE INVENTION The present invention provides a light emitting diode driving apparatus capable of stably driving a light emitting diode.

According to a first aspect of the present invention, there is provided a transformer comprising: a transformer including a first winding on a primary side and a second winding on a secondary side; A rectifying part located on the primary side of the transformer and rectifying the AC power to supply an output voltage to the light emitting part; A light emitting unit connected to a secondary side of the transformer, the light emitting unit including at least one light emitting diode; A control unit provided between one end of the rectifying unit and the transformer and including a switching element and a control circuit for controlling the switching element so as to supply the output of the rectifying unit to the light emitting unit; And a ripple reducing unit which is provided between the other end of the rectifying unit and the transformer and includes a coupling inductor and a capacitor for transferring the output power of the rectifying unit to the transformer using two different paths according to the operation of the switching device Lt; / RTI >

Here, the capacitor may have one end connected to the coupling inductor and the other end connected to the other end of the rectifying part.

Here, the coupling inductor may have a first side connected to one end of the first winding and the switch element, and a second side connected to the other end of the first winding and the capacitor.

The ripple reduction unit may include: a first diode connected between the second side of the coupling inductor and the switch element; And a second diode coupled between the first side of the coupling inductor and the capacitor.

The ripple reduction section may further include: a first path in which the first side of the coupling inductor is charged and the capacitor is discharged to the secondary side of the transformer when the switching element is turned on; And a second path through which the second side of the coupling inductor is discharged and the capacitor is charged when the switch element is off.

An output capacitor connected to the light emitting unit in parallel on a secondary side of the transformer; And a third diode coupled between the transformer and the output capacitor.

Here, the ripple reduction unit may transmit the output power of the rectifying unit to the transformer through the capacitor during a period in which the switching device is off.

According to a second aspect of the present invention, there is provided a light emitting device comprising: a light emitting portion including at least one light emitting diode; A transformer including a first winding on a primary side and a second winding on a secondary side, a rectifying part connected to a primary side of the transformer, a switching element connected to the rectifying part, and a control circuit controlling the switching element, A flyback converter in which a secondary side of the transformer is connected to the light emitting unit; And a ripple reduction unit connected to the primary side of the flyback converter and including a coupling inductor and a capacitor for transferring the output power of the rectification unit to the transformer using two different paths according to the operation of the switching element Lt; / RTI >

Here, the coupling inductor may have a first side connected to one end of the first winding and the switch element, and a second side connected to the other end of the first winding and the capacitor.

At this time, the ripple reduction section may include: a first path in which the first side of the coupling inductor is charged and the capacitor is discharged to the secondary side of the transformer when the switching element is turned on; And a second path through which the second side of the coupling inductor is discharged and the capacitor is charged when the switch element is off.

Here, the capacitor may have one end connected to the coupling inductor and the other end connected to the other end of the rectifying part.

Here, the ripple reduction unit may transmit the output power of the rectifying unit to the transformer through the capacitor during a period in which the switching device is off.

The present invention has the following effects.

First, the light-emitting diode driving apparatus of the present invention can reduce power consumption by reducing power factor correction circuit and DC-DC converter in one step, realize high efficiency and high power density, It is possible to maximize the space utilization.

In addition, the output current ripple in the LED driving apparatus can be greatly reduced.

Accordingly, it is possible to perform stable driving without flicker or flicker of the light emitting diode.

1 is a circuit diagram showing an example of a light-emitting diode driving apparatus.
2 to 5 are diagrams showing an equivalent circuit in each mode in an example of the LED driving apparatus of the present invention.
6 to 9 are circuit diagrams showing respective operation modes according to the progress of time in an example of the LED driving apparatus of the present invention.
10 is a waveform diagram showing output current ripple of the LED driving apparatus according to an embodiment of the present invention.

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

While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings and will herein be described in detail. Rather, the intention is not to limit the invention to the particular forms disclosed, but rather, the invention includes all modifications, equivalents and substitutions that are consistent with the spirit of the invention as defined by the claims.

It will be appreciated that when an element such as a layer, region or substrate is referred to as being present on another element "on," it may be directly on the other element or there may be an intermediate element in between .

Although the terms first, second, etc. may be used to describe various elements, components, regions, layers and / or regions, such elements, components, regions, layers and / And should not be limited by these terms.

1 is a circuit diagram showing an example of a light-emitting diode driving apparatus.

1, an example of a light-emitting diode driving apparatus includes a DC-DC converter type including a rectifying unit 20 for rectifying an AC power source 10 and outputting a rectified output voltage Can be achieved.

As shown in the drawing, the rectifying unit 20 may be a full-wave rectifying circuit in the form of a bridge diode, but is not limited thereto. That is, the rectifying unit 20 may include a plurality of diodes Dz.

The rectifying unit 20 is connected to a control unit 40 including a switching device Q1 and a control circuit 41 for controlling the switching device Q1 so that a power transistor or a MOSFET The output voltage can be controlled by making the device of the on / off switching region operate.

In order to control the output voltage constantly, the control unit 40 detects an output voltage and compares the output voltage with a reference voltage. The control unit 40 adjusts the ON time and the OFF time of the switch element Q1 in a direction for compensating for an error to be generated. ) The ratio of the time (duty ratio) can be adjusted to control the output voltage. For this purpose, pulse width modulation (PWM) can be applied. Here, the voltage is described based on the reference, but can be similarly described based on the power or energy. Hereinafter, a detailed description of the operation of the DC-DC converter will be omitted.

Meanwhile, a feedback circuit for feeding back the operation of the switching element Q1 may be additionally provided, but a detailed description thereof will be omitted.

Such a DC-DC converter may take the form of an isolated transformer including a transformer (T1). That is, the driving apparatus may be provided with a transformer T1 including a first winding Np on the primary side and a second winding Ns on the secondary side.

The primary side of the transformer T1 may be connected to the rectifying unit 20 and the control unit 40 and the secondary side may be connected to the light emitting unit 30 including at least one light emitting diode D _L.

An output capacitor C2 and a diode D3 are connected between the secondary winding Ns of the secondary side of the transformer T1 and the light emitting portion 30 so that the driving circuit can be a flyback converter structure as a whole .

The light emitting unit 30 may include a plurality of light emitting diodes (D _L ) connected in series. In addition, the light emitting units 30 including the plurality of light emitting diodes D _L may be divided into at least two groups and may be driven for each group.

In this way, the driving device has a flyback converter structure including a transformer T1, and the control unit 40 can be provided between the other end 22 of the rectifying unit 20 and the transformer T1. Further, the control unit 40 can perform an operation of controlling the output of the rectifying unit 20 to be supplied to the light emitting unit 30 as described above.

The control unit 40 may be connected to a ripple reduction unit 50 for reducing the ripple of the output current (or output power).

That is, the ripple reduction unit 50 may be connected to the control unit 40 between the one end 21 of the rectifying unit 20 and the transformer T1.

The ripple reduction unit 50 is a coupling inductor that transfers the output power (energy) of the rectifying unit 20 to the transformer T1 side using two different paths 51 and 52 according to the operation of the switching device Q1 L1 and a capacitor C1.

For example, when the switch element Q1 is turned on, the ripple reducing section 50 is turned on when the first side N1 of the coupling inductor L1 is charged and the capacitor C1 is charged to the secondary side of the transformer T1 The second path N2 of the coupling inductor L1 is discharged and the second path 52 in which the capacitor C1 is charged when the first path 51 and the switching element Q1 are discharged off ).

The ripple reduction unit 50 can transmit the output power of the rectifying unit 20 to the transformer T1 via the capacitor C1 during a period in which the switching device Q1 is off.

1, one end of the capacitor C1 may be connected to the coupling inductor L1, and the other end may be connected to the other end 22 of the rectifying part 20. As shown in FIG.

The coupling inductor L1 has the first side N1 connected to one end of the first winding Np of the transformer T1 and the switching element Q1 and the second side N2 connected to the first winding Np, And the capacitor C1.

The ripple reduction section 50 includes a first diode D1 connected between the first side N1 of the coupling inductor L1 and the switch element Q1 and a second side N2 of the coupling inductor L1, And a second diode (D2) connected between the capacitor (C1) and the capacitor (C1).

As described above, the circuit of the driving apparatus constitutes a flyback converter for driving the light emitting portion 30 including at least one light emitting diode (D _L ), and this flyback converter is provided with a ripple of the output current or voltage And a ripple reduction unit 50 capable of reducing the amount of the ripple.

As described above, the flyback converter includes a transformer T1 including a first winding Np on the primary side and a second winding Ns on the secondary side, and a transformer T1 connected to the primary side of the transformer T1. And a control circuit 41 for controlling the switching element Q1 so that the secondary side of the transformer T1 is connected to the light emitting portion 30).

The switch device (Q1) of the same drive system performs a periodic operation by the control circuit 41, the operation mode according to this periodical operation is t ₀ a first mode for a time interval -t _1, t ₁ a second mode for a time interval of -t ₂ , a third mode for a time interval of t ₂ -t ₃ , and a fourth mode for a time interval of t ₃ -t ₄ .

That is, the driving device can operate in four operation modes as shown in FIGS. 2 to 5 according to the operation time interval of the switching device Q1. 2 to 5 show an equivalent circuit in each mode of the driving apparatus of the present invention.

Fig. 2 shows the operation of the driving apparatus when the switching element Q1 is on, and Fig. 3 shows the operation of the driving apparatus when the switching element Q1 is off.

That is, in FIG. 2, the power source 10 through the rectifying section 20 is transmitted to the light emitting section 30 through the first side N1 of the coupling inductor L1, It can be seen that the power source 10 is transmitted to the light emitting unit 30 through the side N2 and the light emitting unit 30 is driven by the output voltage Vo.

In FIGS. 4 and 5, it can be seen that this energy is transferred to the secondary side of the transformer T1, and the light emitting unit 30 can be driven by the output voltage Vo.

Hereinafter, with reference to FIGS. 6 to 9, the operation modes of the circuit of FIG. 1 according to the progress of time will be described as follows.

First, the first mode for the time interval t ₀ -t ₁ of the switching element Q1 will be described with reference to FIG.

At this time, the switch element Q1 is turned on and the diode (the third diode D3) of the secondary side is turned off.

In addition, the coupling inductor L1 is charged and this charging current flows through the switching element Q1 via the first diode D1.

At this time, the charge stored in the capacitor C1 is discharged, and the energy stored in the capacitor C1 is transferred to the primary side of the transformer T1, that is, one end of the first winding Np.

In this case, the light emitting portion 30 can emit light by the electric charge accumulated in the output capacitor C2.

Next, with reference to Figure 7 will be described in a second mode for a time interval t ₁ -t ₂ of the switching element (Q1).

At this time, the switch element Q1 is turned off and the diode D3 of the secondary side is turned on.

In addition, the coupling inductor L1 is discharged and the discharging current charges the capacitor C1 via the second diode D2.

At this time, the energy stored in the primary side of the transformer T1, that is, the first winding Np, is transmitted to the output of the secondary winding Ns on the secondary side as indicated by the right arrow.

Hereinafter, a third mode for the time interval t ₂ -t ₃ of the switching element Q1 will be described with reference to FIG.

First, the current of the coupling inductor L1 becomes zero, and this magnetization inductor current continues to flow back to the secondary side of the transformer T1.

And thus the output capacitor C2 is charged.

At this time, the output voltage Vo is formed by the current of the magnetizing inductor to be refluxed, so that the light emitting portion 30 can be continuously driven.

Next, referring to Fig. 9 will be described a fourth mode for a time interval t ₃ -t ₄ of the switching element (Q1).

At this time, the magnetizing inductor current becomes zero, and the output capacitor C2 is discharged to continue to generate the output voltage Vo, so that the light emitting portion 30 can be driven.

The light emitting portion 30 can be driven by four operation modes according to the operation period of the switch element Q1.

At this time, the ripple of the output current can be greatly reduced by this operation.

That is, by the operation of the ripple reduction unit 50 and the control unit 40, the output power of the rectifying unit can be transmitted to the transformer T1 through the capacitor C1 during the period in which the switching device Q1 is off , It is possible to transmit continuous power without a moment when the current becomes zero.

As described above, continuous driving is possible without a discontinuous section, so that the ripple current is greatly reduced and the light emitting unit 30 can be driven more stably.

10 is a waveform diagram showing output current ripple of the LED driving apparatus according to the embodiment of the present invention.

FIG. 10 shows a waveform in which the current waveform according to the embodiment of the present invention is compared with a conventional single-stage flyback drive circuit. Here, the conventional current waveform is indicated by a dotted line, and the current waveform according to the present invention is indicated by a solid line.

Here, the two waveforms show the case of driving the output capacitor C2 equally, and it is confirmed that the output current ripple is reduced to about 1/10 as shown in the figure.

The light emitting diode driving apparatus described above can reduce power consumption by reducing the power factor correction circuit and the DC-DC converter in one step, and can realize high efficiency and high power density, and can be downsized Thereby maximizing the space utilization.

Further, as described above, the ripple reduction section can be constituted to greatly reduce the output current ripple.

Accordingly, it is possible to perform stable driving without flicker or flicker of the light emitting diode.

It should be noted that the embodiments of the present invention disclosed in the present specification and drawings are only illustrative of specific examples for the purpose of understanding and are not intended to limit the scope of the present invention. It will be apparent to those skilled in the art that other modifications based on the technical idea of the present invention are possible in addition to the embodiments disclosed herein.

10: AC power supply 20:
30: light emitting unit 40:
41: control circuit 50: ripple-
51: first path 52: second path

Claims (12)

A transformer including a first winding on the primary side and a second winding on the secondary side;
A rectifying part located on the primary side of the transformer and rectifying the AC power to supply an output voltage to the light emitting part;
A light emitting unit connected to a secondary side of the transformer, the light emitting unit including at least one light emitting diode;
A control section which is provided between the other end of the rectifying section and the transformer and includes a switching element and a control circuit for controlling the switching element so as to supply the output of the rectifying section to the light emitting section; And
And a ripple reduction unit that is provided between one end of the rectification unit and the transformer and includes a coupling inductor and a capacitor for transferring the output power of the rectification unit to the transformer using two different paths in accordance with the operation of the switching device, And wherein the light emitting diode drive circuit comprises: The light emitting diode driving circuit according to claim 1, wherein the capacitor has one end connected to the coupling inductor and the other end connected to the other end of the rectifying part. 2. The light emitting diode according to claim 1, wherein the coupling inductor has a first side connected to one end of the first winding and the switch element, and a second side connected to the other end of the first winding and the capacitor. Drive circuit. The apparatus of claim 3, wherein the ripple-
A first diode coupled between the first side of the coupling inductor and the switch element; And
And a second diode coupled between the second side of the coupling inductor and the capacitor. The apparatus of claim 3, wherein the ripple-
A first path in which the first side of the coupling inductor is charged and the capacitor is discharged to the secondary side of the transformer when the switching element is on; And
And a second path through which the second side of the coupling inductor is discharged and the capacitor is charged when the switching element is turned off. The transformer according to claim 1, wherein, on the secondary side of the transformer,
An output capacitor connected in parallel to the light emitting unit; And
And a third diode coupled between the transformer and the output capacitor. The light emitting diode driving circuit according to claim 1, wherein the ripple reduction unit transfers the output power of the rectifying unit to the transformer through the capacitor during a period in which the switching device is off. A light emitting unit including at least one light emitting diode;
A transformer including a first winding on the primary side and a second winding on the secondary side, a rectifying part connected to the primary side of the transformer, a switch element connected to the rectifying part, and a control circuit controlling the switch element A flyback converter in which a secondary side of the transformer is connected to the light emitting unit;
And a ripple reduction unit connected to the primary side of the flyback converter and including a coupling inductor and a capacitor for transferring the output power of the rectification unit to the transformer using two different paths according to the operation of the switching element And the light emitting diode drive circuit is configured to emit light. The light emitting diode according to claim 8, wherein the coupling inductor has a first side connected to one end of the first winding and the switch element, and a second side connected to the other end of the first winding and the capacitor. Drive circuit. The apparatus according to claim 9, wherein the ripple-
A first path in which the first side of the coupling inductor is charged and the capacitor is discharged to the secondary side of the transformer when the switching element is on; And
And a second path through which the second side of the coupling inductor is discharged and the capacitor is charged when the switching element is turned off. The light emitting diode driving circuit according to claim 8, wherein one end of the capacitor is connected to the coupling inductor and the other end is connected to the other end of the rectifying part. The light emitting diode driving circuit according to claim 8, wherein the ripple reduction unit transfers the output power of the rectifying unit to the transformer through the capacitor during a period when the switching device is off.

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