KR20100084256A - Driving apparatus of light emitting diode and driving method thereby - Google Patents

Abstract

PURPOSE: An apparatus for driving a light emitting device and a driving method thereof are provided to reduce harmonic distortion by removing harmonic components loaded on the voltage of the node by a capacitor. CONSTITUTION: A power converter converts input power into the power for driving a light emitting device. A controller control the output power of the power converter by detecting the current related to the driving of the light emitting device. An energy accumulating unit is arranged between an input terminal and a first output terminal of the power converter. A rectifier is arranged between the energy accumulating unit and the first output unit. A smoothing unit is connected between the first output terminal and the second output terminal of the power converter in parallel. A current detector(22) detects the current related to the driving of the light emitting device. A pulse width modulation controller(26) generates a pulse width modulation signal corresponding to the current detected by the current detector.

Description

Light emitting device driving device and driving method {DRIVING APPARATUS OF LIGHT EMITTING DIODE AND DRIVING METHOD THEREBY}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light emitting device driving apparatus and a driving method, and more particularly, to a light emitting device driving apparatus and a driving method capable of improving power factor, increasing power efficiency, and reducing harmonic distortion.

Light emitting diodes (LEDs), in particular light emitting diodes (LEDs), are increasingly being adopted and popularized in various applications, and are even replacing conventional lamps with filaments. For example, LEDs are also used for traffic lights and are also widely used for backlighting liquid crystal display (LCD) panels.

In many applications, it may be necessary to vary the light output (brightness) of the LED. In general, using voltage control to control the light output of an LED is not easy. Therefore, since the brightness of the LED is proportional to the current input to the LED, the current input to the LED is controlled to control the brightness of the LED. The brightness control of such LEDs is called LED dimming.

In many applications that require varying the brightness of the LEDs, there is an increasing demand for suitable power converters to control the LED current. In many applications, the current to drive the LED may be in the form of an alternating current (AC) input, in which case the AC current is synchronized to the voltage to minimize current distortion, in order to maximize the energy delivered from the power source. it needs to be synchronized.

If there is a phase delay between the input voltage and the current, the power delivered from the power source to the load (ie LED), which can be expressed in terms of the cosine of such phase difference, is reduced. If the voltage and current are in phase, the phase difference is zero and the cosine is one. This technique is known as power factor correction (PFC). For lighting and other applications, this power factor correction circuit is almost an essential component.

According to the prior art, the LED driving circuit needed to have at least two power stages for power factor correction as well as LED current control. Each power stage performs some form of power conversion, typically one power stage is a pre-regulator, a power stage for performing power factor control, and the other power stage is DC-DC (DC-DC). As a converter, it performs LED current control. Since the power efficiency of the added power stage is not 100% (which is difficult to actually implement when the power efficiency is 100%), there is a respective power loss for such power stages.

Therefore, the power efficiency of the entire LED driving circuit having a plurality of power stages becomes that much lower. For example, assuming that the respective power efficiencies in the two power stages are 90% and 90%, the overall efficiency is expressed as the product of the respective power efficiencies, resulting in 81% (0.9 x 0.9 = 0.81).

As described above, although two power stages are used in the LED driving circuit, three or more power stages are used, and in such cases, there is a problem in that power efficiency becomes less and less.

Therefore, there is an urgent need for an LED driving circuit that can improve these problems and improve power efficiency.

 Accordingly, the problem to be solved by the present invention is a problem of lowering the power efficiency, which is a problem of the conventional LED driving circuit including at least two power stages for LED current control as well as power factor correction in driving the LED. To provide a light emitting device driving apparatus and a driving method for improving.

Another object of the present invention is to provide a light emitting device driving apparatus and a driving method capable of improving power factor and reducing harmonic distortion (THD).

According to an aspect of the present invention, there is provided a light emitting device driving apparatus including: a power converter converting input power into power for driving a light emitting device, and detecting a current related to driving of the light emitting device. And a controller for controlling the output power of the power converter.

Preferably, the power converter includes an energy accumulator disposed between an input terminal of the power converter and a first output terminal of the power converter, a rectifier disposed between the energy accumulator and the first output terminal, and the first output terminal. And a smoothing unit connected in parallel between an output terminal and a second output terminal of the power converter, wherein the second output terminal may be commonly connected to the input terminal.

Preferably, the energy accumulator may include an inductor that repeats an operation of storing energy and supplying the energy to the light emitting device according to the control of the controller during operation.

Preferably, the smoothing unit may include a capacitor having a cathode connected to the second output terminal and a cathode connected to the first output terminal.

Preferably, the rectifier may include a rectifier diode forward connected to the first output end in the energy accumulator.

Preferably, the control unit includes a current detector for detecting a current associated with driving the light emitting device, a pulse width modulation controller for generating a pulse width modulated signal corresponding to the current detected by the current detector, and the energy accumulation. And a switching unit connected between the unit and the pulse width modulation controller to change an amount of current flowing under control of the pulse width modulation controller.

Preferably, the current related to driving of the light emitting device may be any one of a current supplied to the light emitting device, a current of the energy storage unit, and a current flowing in the switching unit.

Preferably, the control unit may further include a voltage detector for detecting the output voltage of the power converter.

The light emitting device driving apparatus according to another aspect of the present invention for solving the above problems is located between the bridge rectifier for full-wave rectification by applying AC power, between the output terminal of the bridge rectifier and the first input terminal of the light emitting device, An inductor for providing power to drive the light emitting device, a capacitor connected to the first input terminal and the second input terminal of the light emitting device in parallel to stabilize a current supplied to the light emitting device, and a reverse direction to the light emitting device. Rectifying diodes to prevent current from flowing, switching elements for controlling the power supplied from the inductor to the light emitting elements, and controlling the currents of the switching elements corresponding to changes in the currents related to driving of the light emitting elements. It includes a pulse width modulation control unit for.

Preferably, the current associated with driving the light emitting device may be any one of a current supplied to the light emitting device, a current of the inductor, and a current of the switching device.

Preferably, it may include a current detector for detecting at least one of the current supplied to the light emitting device, the current of the inductor, and the current of the switching device.

Preferably, the electronic device may further include a voltage detector for detecting an input voltage of the light emitting device.

According to an aspect of the present invention for solving the above problems, a light emitting device driving method using a buck boost circuit and a pulse width modulation control circuit, the step of supplying power to the light emitting device, the current supplied to the light emitting device, Detecting any one of an internal current of a buck boost circuit and a current of a switching transistor of the pulse width modulation control circuit, generating a pulse width modulated signal corresponding to the detected current, and generating the generated pulse width Controlling the input current of the light emitting device by a modulation signal.

Preferably, the light emitting device driving method includes detecting an input voltage of the light emitting device, generating a pulse width modulated signal corresponding to the detected voltage, and generating the pulse width modulated signal by the generated pulse width modulated signal. The method may further include controlling an input voltage of the light emitting device.

As described above, the present invention provides an improved light emitting device driving apparatus and driving method, thereby reducing power efficiency by including at least two power stages for power factor correction as well as current control of LEDs when driving LEDs. The conventional problem that can be solved.

In addition, the present invention can improve the power factor and reduce the harmonic distortion by providing an improved light emitting device driver and driving method.

In addition, the present invention can increase the life of the light emitting device driving apparatus by providing an improved light emitting device driving apparatus and driving method.

Hereinafter, exemplary embodiments of the present invention will be described with reference to the accompanying drawings. The accompanying drawings and the following description are simplified for the purpose of helping those skilled in the art to understand the present invention, and therefore, the scope of protection of the present invention should not be limited by these. .

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

Referring to FIG. 1, a power converter 10, a controller 20, and a light emitting device 30 are illustrated. First, the power converter 10 receives the input power (V0, I0) to convert the power (V1, I1) for driving the light emitting device 30, the control unit 20 of the light emitting device 30 The current related to the driving is detected, and the output powers V1 and I1 of the power converter 10 are controlled according to the detected current (S1).

Here, the current related to the driving of the light emitting device 30 may be detected by the current I2 and the control unit 20 which are detectable in relation to the operation of the light emitting device 30 in the power converter 10 in the light emitting device driving apparatus. The current I3 may be detected in relation to the operation of the light emitting device 30, and the current such as the actual input current I1 of the light emitting device 30 may be one. A more specific example of the current related to the driving of the light emitting element 30 is described below with reference to FIGS. 3 to 7.

FIG. 2 is a block diagram illustrating a specific example of the power converter 10 of FIG. 1. Referring to FIG. 2, the power converter 10 includes an energy accumulator 12, a rectifier 14, and a smoother 16.

The energy accumulator 12 includes an input terminal of the power converter 10, that is, a terminal to which input powers V0 and I0 are supplied (hereinafter referred to as V0 and I0 for convenience) and a first output terminal of the power converter 10. That is, disposed between stages (hereinafter, referred to as V1 and I1 for convenience) to which the input powers V1 and I1 of the light emitting device 20 are supplied, and accumulate energy according to the control S1 of the control unit 20 during operation. Then, the operation of supplying the light emitting element 30 to the side is repeated. For example, the energy accumulator 12 may include an inductor.

The rectifier 14 is disposed between the energy accumulator 12 and the first output terminals V1 and I1 to block the reverse flow of the current I1. For example, the rectifier 14 may include a rectifier diode that is forward-connected from the energy accumulator 12 toward the first output terminals V1 and I1.

The smoothing unit 16 is connected in parallel between the first output terminal V1 and I1 and the second output terminal of the power converter 10, and the second output terminal is connected to the same node as the input terminals V0 and I0. For example, the smoothing unit 16 includes a capacitor connected between the first output terminal V1 and I1 and the second output terminal V0 and I0. The smoothing portion 16 smoothes an alternating current component, that is, a current having a large ripple, so that a stable direct current is supplied to the diode 30 side.

3 is a block diagram illustrating a specific example of the control unit 20 in FIG. 1. Referring to FIG. 3, the controller 20 includes a current detector 22, a pulse width modulation controller 26, and a switching unit 28. In addition, the controller 20 may further include a voltage detector 24.

The current detector 22 detects a current related to the driving of the light emitting element 30. As described above, the electric current related to the driving of the light emitting element 30 is a current I2 detectable in relation to the operation of the light emitting element 30 in the power converter 10 and the control unit in the light emitting element driving apparatus. 20 may be any one of a detectable current I3 and an actually input current I1 of the light emitting device 30 in connection with the operation of the light emitting device 30.

The pulse width modulation control unit 26 corresponds to the currents I1, I2, and I3 detected by the current detection unit 22, that is, a period of the high level and the low level of the pulse width modulation signal PWM (that is, the duty ratio (duty ratio). (Indicated by)).

For example, the current detector 22 provides the current detection results (output according to the magnitudes of I1, I2, and I3) to the pulse width modulation controller 26. If the detected current is increased than the set size, When the voltage is greater than or equal to the set voltage, the pulse width modulation control unit 26 outputs a low level pulse width modulation signal PWM to the switching unit 28. Accordingly, the switching unit 28 is turned off, and controls to reduce the power supplied to the light emitting element 30 by the power converter 10 (S1). On the contrary, when the detected current is smaller than the set magnitude, the pulse width modulation controller 26 outputs a high level pulse width modulation signal PWM to the switching unit 28. As a result, the energy accumulated in the energy storage unit 12 increases, and the power supplied to the light emitting element 30 increases.

In addition, the voltage detector 24 outputs a resultant voltage corresponding to the input voltage difference of the light emitting device 30 to the pulse width modulation controller 26. If the detected voltage V1 is equal to or greater than the set voltage, The pulse width modulation control unit 26 outputs a low level pulse width modulation signal PWM to the switching unit 28. Accordingly, the switching unit 28 is turned off, and controls to reduce the power supplied to the light emitting element 30 by the power converter 10 (S1). On the contrary, when the detected voltage V1 is smaller than the set voltage, the pulse width modulation control unit 26 outputs the high level pulse width modulation signal PWM to the switching unit 28, and thus the energy storage unit 12 The energy accumulated in the light source increases to increase the power supplied to the light emitting device 30.

The switching unit 28 is connected between the energy accumulating unit 10 and the pulse width modulation control unit 26, so that the amount of current I3 controlled and controlled by the pulse width modulation control unit 26 is changed. The switching unit 28 is a switchable device, and may be, for example, a bipolar junction transistor or a field effect transistor.

4 is a diagram illustrating a specific configuration example of the light emitting device driving circuit of FIG. 1. Referring to FIG. 4, the bridge rectifiers D42, D43, D44, and D45, the inductor L41, the capacitor C41, the rectifier diode D41, the switching element Q41, the pulse width modulation controller 26, and the current detector And a voltage detector 24. For clarity, the components in FIGS. 1 to 3 correspond to the elements of FIG. 4.

The bridge rectifiers D42, D43, D44, and D45 full-wave rectify the applied AC power supply Vac. Nodes N41 and N44 are output nodes (or output stages) of the bridge rectifiers D42, D43, D44 and D45.

The inductors L41 and 12 are positioned between the output terminal N41 of the bridge rectifiers D42, D43, D44, and D45 and the first input terminal (node N42) of the light emitting device LED 30 to provide a light emitting device 30. Provide a range of currents. As described above, the inductors L41 and 12 repeat the operation of accumulating energy and supplying the energy to the light emitting element 30 in accordance with the control S1 of the control unit 20 during operation.

The capacitors C41 and 16 are connected in parallel between the first input terminal (node N42) and the second input terminal (node N41) of the light emitting device 30 to stabilize the current supplied to the light emitting device 30.

The rectifier diodes D41 and 14 prevent the reverse current from flowing through the light emitting device 30. Thus, rectifying diodes D41 and 14 are forward connected from node N43 to node N42.

The switching elements Q41 and 28 serve to control the current supplied from the inductors L41 and 12 to the light emitting element 30. That is, the switching elements Q41 and 28 control the magnitude of the current supplied from the inductors L41 and 12 to the light emitting element 30 by repeating the on or off operation by the pulse width modulation signal PWM.

The pulse width modulation control unit 26 detects a current related to driving of the light emitting element 30 and controls the currents of the switching elements Q41 and 28 according to the detected current. The electric current related to the driving of the light emitting element 30 is a current detectable in connection with the operation of the light emitting element 30 in the power converter 10 in the light emitting element driving apparatus (hereinafter referred to as I2) and the control unit ( 20 may be any one of a current detectable in relation to the operation of the light emitting device 30 (hereinafter referred to as I3), and a current such as an actual input current I1 of the light emitting device 30.

For example, the current I1 can be detected by measuring the actual input current of the light emitting element 30, and the current I2 is the current detected from the average current of the inductors L41, 12 using a current transformer (CT). Can be. In addition, the current I3 is a current of the switching elements Q41 and 28, and a detection resistor (see R74 in FIG. 7) is inserted between the source terminal and the ground terminal of the switching elements Q41 and 28, and to such a resistor R74. The applied resistance can be used to detect the current I3.

The light emitting element driving apparatus detects at least one of the current I1 supplied to the light emitting element 30, the current I2 of the inductors L41 and 12, and the current I3 of the switching elements Q41 and 28. It includes a current detection unit 22 for.

5 is a diagram illustrating a configuration example of the current detector 22 in FIG. 4. Referring to FIG. 5, the current detector 22 includes an operational amplifier 50, resistors Rf, Rs, and Ri, and a diode D51.

In FIG. 5, when the voltage at the output terminal of the operational amplifier 50 is Vo, Vo ∝ {(Rf + Rs) / Rs} * Is, that is, the voltage Vo at the output terminal of the operational amplifier 50 is detected current. Has a relationship proportional to (Is). Here, the detected current Is is any one of the current I1 supplied to the light emitting element 30, the current I2 of the inductors L1, 12, and the current I3 of the switching elements Q41, 28. May be associated with For example, as mentioned above, the current I1 can be obtained by directly detecting the current I1 supplied to the light emitting element 30, and the current I2 can be obtained by using the current transformer CT. It may be a current detected from an average current of. In addition, the current I3 can be detected from the voltage across the resistor connected between the source terminal of the switching element Q41 and ground, but the method of detecting the currents I1, I2, and I3 is not limited to these examples. In addition to the methods described above, various methods may be used.

4 and 5 together, if the detected current Is increases more than the normal state, the output voltage Vo is increased by the above relation with the output voltage Vo. When the output voltage Vo is increased, the input voltage of the pulse width modulation controller 26 is increased. When the input voltage increases, the pulse width modulation controller 26 turns off the switching element Q41 to reduce the power supplied to the light emitting element 30.

On the contrary, when the detected current Is decreases from the steady state, the output voltage Vo is reduced by the above relation with the output voltage Vo. When the output voltage Vo decreases, the input voltage of the pulse width modulation controller 26 decreases. In this case, the pulse width modulation controller 26 turns on the switching element Q41 to the light emitting element 30. Increase the power supplied.

In this way, the current detector 22 detects currents (eg, I1, I2, I3) related to the driving of the light emitting element, and controls the amount of current supplied to the light emitting element 30 side accordingly.

In the light emitting device driving apparatus according to the exemplary embodiment of the present invention, the controller 20 may further include a voltage detector 24 for detecting an output voltage of the power converter 10.

FIG. 6 is a diagram illustrating an example of the configuration of the voltage detector 24 in FIG. 3. Referring to FIG. 6, an operational amplifier 60 and resistance elements R61, R62, R63, R64, R65, and R66 are illustrated. It is.

The output voltage of the comparator 60 (voltage of node N61, Vo) is divided into a resistor R65 and a resistor R66 and provided to an input of the pulse width modulation controller 26. The output voltage Vo of the comparator 60 may be expressed as the product of the difference between the inverting input voltage V63 and the non-inverting input voltage V64 of the comparator 60 and the gain m of the differential amplifier. For example, in order to divide and supply each of the voltages of the inverting input voltage V63 and the non-inverting input voltage V64 of the comparator 60 at a predetermined ratio, while providing the same gain of the amplifier, the gain m R65 / R61 and R65 / R62 can be designed identically.

4 and 6 together, the output voltage Vo of the comparator 60 proportional to the difference between the inverting input voltage V63 and the non-inverting input voltage V64 of the comparator 60 is a predetermined reference voltage ( If the pulse width modulation control unit 26 is set in advance), the pulse width modulation control unit 26 provides a low level pulse width modulation signal PWM to the gate terminal of the switching element Q41. On the contrary, when the output voltage Vo of the comparator 60 is less than the predetermined reference voltage, the pulse width modulation control section 26 provides the high level pulse width modulation signal PWM to the gate terminal of the switching element Q41. do.

Thus, the voltage detector 24 controls the voltage supplied to the light emitting device 30 to be lower when the voltage supplied to the light emitting device 30 is higher than the normal voltage, and to increase the voltage when the voltage supplied to the light emitting device 30 is higher than the normal voltage. The input voltage of 30 is controlled.

7 is a view showing a specific configuration example of a light emitting device driving apparatus according to an embodiment of the present invention. Referring to FIG. 7, the light emitting device driving apparatus includes a fuse F71, an EMI filter C71, L71 and C72, a bridge rectifier B71, an inductor L72, a rectifier diode D71, a capacitor C74, and a switching. An element Q71, a pulse width modulation control unit 26, current detectors D72, 82, R82, R83, R84, and voltage detectors 80, R76, R77, R78, R79, R80, R81 are included.

The input terminals IN1 and IN2 are portions for applying AC power, and a fuse F71 is provided between the input terminals IN1 and IN2 and the EMI filters C71, L71 and C72 to protect the light emitting device driving apparatus. do.

Electromagnetic Interference Filters (C71, L71, C72) form an LC low pass filter, as shown, where the inductor (L71) is used to remove the primary and second phases. It is preferable that the difference side is wound so as to have the same phase.

The outputs of the EMI filters C71, L71, C72 are rectified by the bridge rectifier B71. The bridge rectifier B71 full-wave rectifies the output of the EMI filters C71, L71, and C72, and the full-wave rectified current is supplied to the rear end in the form of a pulse wave.

Capacitor C73 removes harmonic components carried by the voltage at node N72.

The current with the harmonics removed is provided to the inductor L72. That is, the inductor L72 is positioned between the output terminal N72 of the bridge rectifier B71 and the first input terminal OUT1 of the light emitting device, and serves to provide a range of current to the light emitting device.

The capacitor C74 is connected in parallel with the first input terminal OUT1 and the second input terminal OUT2 of the light emitting device to stabilize the current supplied to the light emitting device.

The rectifier diode D71 is forward connected from the node N73 to the node N74 in order to prevent the reverse current from flowing to the light emitting element side, that is, the OUT1 and OUT2 sides.

In the above, the circuit including the inductor L72, the rectifying diode D71, and the capacitor C74 is sometimes referred to as a buck boost circuit because it may lower or raise the input voltage in some cases.

The switching element Q71 controls the power supplied from the inductor L72 to the light emitting element, and the pulse width modulation control unit 26 controls the current of the switching element Q71 to correspond to the change of the current related to the driving of the light emitting element. To control.

As described above, the current related to the driving of the light emitting device may be related to any one of the current I1 directly supplied to the light emitting device, the current I2 of the inductor, and the current I3 of the switching device. For example, the current I1 supplied to the light emitting element 30 can be obtained by directly detecting the current flowing through the output terminal OUT1, and the current I2 is the average current of the inductors L41 and 12 using the current transformer CT. Can be detected from. In addition, the current I3 can be detected from the voltage across the resistor connected between the source terminal of the switching element Q41 and ground, but the method of detecting the currents I1, I2, and I3 is not limited to these examples. In addition to the methods described above, various methods may be used.

In addition, the current detectors 82, R82, R83, and R84 for detecting at least one of the current I1 supplied to the light emitting element, the current I2 of the inductor L72, and the current of the switching element Q71 are provided. Also shown are voltage detectors 80, R76, R77, R78, R79, R80, and R81 for detecting the input voltage of the light emitting device.

Specific descriptions of the current detectors 82, R82, R83, and R84 and the voltage detectors 80, R76, R77, R78, R79, R80, and R81 have been described with reference to FIGS. 5 and 6, respectively, and thus detailed descriptions thereof will be omitted. .

The pulse width modulation controller 26 controls the switching element Q71 according to the detected current Is, and further controls the switching element Q71 according to the detected voltage (difference between V72 and V71). As a result, by controlling the current flowing through the switching element Q71, the power supplied from the inductor L72 to the light emitting element sides OUT1 and OUT2 is controlled.

Examples of the pulse width modulation control section 26 include the L6560, L6561, L6562, L6563, and TI (Texas Instruments) UC3852, UC3853, and UC3854 of STM (STMicroelectronics), which are ICs that are widely used for power factor correction and brightness adjustment. ICs such as Fairchild's ML4810 and ML4812 may be used, but are not particularly limited thereto. In FIG. 7, an example of the pulse width modulation control unit 26 uses the L6561 IC of STM.

When the pulse width modulation control unit 26 operates by receiving the operating voltage Vcc through pin 8, the pulse width modulation signal PWM is output to pin 7 as an output terminal, and the pulse width modulation signal PWM is output. At the high level, the switching element Q71 is turned on, and at the low level, the switching element Q71 is turned off.

As pin 5 of the pulse width modulation controller 26, a voltage induced by the inductor L72 is applied through the resistor R72. Thus, the zero current of the inductor L72 is detected and reflected in the generation of the pulse width modulated signal PWM of the switching element Q71. More specifically, the set time point of the pulse width modulated signal PWM is involved in the determination.

Pin 4 of the pulse width modulation control unit 26 is connected to the source terminal of the switching element Q71 through the resistor R73, and the voltage of the source terminal of the switching element Q71 is divided by the resistors R74 and R73. . That is, the voltage applied to pin 4 of the pulse width modulation control section 26 is a portion for detecting whether the current flowing through the resistor R74 becomes a current having a predetermined magnitude in the pulse width modulation control section 26. It is involved in the determination of the reset timing of the width modulated signal PWM.

Pin 6 of the pulse width modulation controller 26 is grounded, and pins 1 and 2 are connected to the output terminals of the current detector 22 and the voltage detector 24. Pin 3 of the pulse width modulation control unit 26 is an input of a multiplier inside the pulse width modulation control unit 26 to reset the pulse width modulation signal PWM through calculation with a voltage applied to pin 4. Involved in the decision of the time point.

First, when an external AC power source (not shown) is applied to the input terminals IN1 and IN2, and is full-wave rectified by the full-wave rectifier B71, and then a DC voltage is applied to the node N72 side, the pulse width modulation control unit 26 Energy is accumulated in the inductor L72 in a section in which the switching element Q71 is turned on, that is, in a section in which the pulse width modulation signal PWM is at a high level.

The pulse width modulation control unit 26 senses the current flowing through the resistor R74 (actually, the voltage across the resistor R74), and when the set voltage is reached, resets the pulse width modulation signal PWM. That is, the switching element Q71 is turned off so that the pulse width modulation signal PWM becomes low level. When the switching element Q71 is turned off, energy is not accumulated in the inductor L72, and electric power is supplied to the light emitting element via the rectifying diode D71. In addition, charging of the capacitor C74 is also performed.

As described above, by continuously detecting the voltage applied to the resistor R74, the process of repeatedly generating the pulse width modulated signal PWM to turn on the switching element Q71 when the voltage is lower than the set voltage and turn it off when the voltage is higher than the set voltage is high. The light emitting device is driven.

In the normal operation state as described above, the current detectors 82, R82, R83, and R84 provide the current detection result to the pulse width modulation controller 26, if the detected current Is increases more than the set magnitude. The output voltage (voltage of node N75) increases. When the output voltage is increased, the input voltage of pin 1 of the pulse width modulation controller 26 is increased. When the output voltage is increased above the set voltage, the pulse width modulation controller 26 is pin 7 at a low level. The width modulated signal PWM is outputted. Thus, the switching element Q71 is turned off, and the power supplied to the light emitting element is reduced.

Conversely, when the detected current Is decreases below the set magnitude, the output voltage decreases. When the output voltage decreases, since the input voltage of pin 1 of the pulse width modulation control section 26 decreases, a high level pulse width modulation signal PWM is output to pin 7. Thus, the switching element Q71 is turned on, and the energy accumulated in the inductor L72 increases, thereby increasing the power supplied to the light emitting element.

The light emitting device driving apparatus according to the present invention detects a current associated with driving the light emitting device in the above manner, and controls the current accordingly.

In addition, the voltage detectors 80, R76, R77, R78, R79, R80, and R81 have an output voltage proportional to the difference between the inverting input voltage V73 and the non-inverting input voltage V74 of the comparator 80 (node N75). Voltage) is provided to pin 1 of the pulse width modulation control unit 26.

For example, when the output voltage of the comparator 80 is equal to or greater than the set reference voltage, the pulse width modulation controller 26 outputs the low level pulse width modulation signal PWM to pin 7, and accordingly, the switching element Q71. ) Is turned off to reduce the power supplied to the light emitting device.

On the other hand, when the output voltage of the comparator 80 is less than the set reference voltage, the pulse width modulation control section 26 outputs the high level pulse width modulation signal PWM to pin 7, thereby switching element Q71. Is turned on to increase the power supplied to the light emitting device.

As described above, the light emitting device driving apparatus according to the present invention does not use a separate power stage such as a power stage for power factor control, a DC-DC conversion stage for performing current control of the light emitting device, and as a single stage, By detecting the current associated with driving the light emitting device, the current can be controlled accordingly, and the input voltage of the light emitting device can be detected to control the voltage accordingly.

In addition, referring to FIG. 4, the light emitting device driving method according to an exemplary embodiment of the present invention uses a buck boost circuit 4 (L41, D41, C41) and a pulse width modulation control circuit 26. The light emitting device driving method includes: 1) supplying power to the light emitting device 30, 2) current I1 supplied to the light emitting device 30, internal current I2 of the buck boost circuit, and pulse width; Detecting any one of the currents I3 of the switching transistors of the modulation control circuit, 3) generating a pulse width modulation signal PWM corresponding to the detected current, and 4) generating a pulse width modulation signal ( PWM) to control the input current of the light emitting device (30).

Furthermore, the light emitting device driving method according to an embodiment of the present invention, 5) detecting the input voltage of the light emitting device 30, 6) generating a pulse width modulation signal (PWM) corresponding to the detected voltage Step 7 and controlling the input voltage of the light emitting device 30 by the generated pulse width modulation signal PWM.

Here, the currents I1, I2, and I3 related to the driving of the light emitting device 30 may be detected by various methods as described above, and according to the detection results of the voltage detector 24 and the current detector 22. Since the input control of the light emitting element 30 through the control of the switching element Q41 of the pulse width modulation control unit 26 has been described above with reference to FIGS. 1 to 7, redundant description thereof will be omitted.

The light emitting device driving apparatus and the driving method according to the present invention described above are provided by those skilled in the art without departing from the scope of protection of the present invention defined by the claims. It will be clear that various changes and modifications can be made.

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

FIG. 2 is a block diagram illustrating a specific example of the power converter in FIG. 1.

3 is a block diagram illustrating a concrete example of the controller of FIG. 1.

4 is a diagram illustrating a specific configuration example of the light emitting device driving circuit of FIG. 1.

FIG. 5 is a diagram illustrating an example of a configuration of the current detector of FIG. 4.

6 is a diagram illustrating an example of a configuration of a voltage detector in FIG. 3.

7 is a view showing a specific configuration example of a light emitting device driving apparatus according to an embodiment of the present invention.

<Explanation of symbols for the main parts of the drawings>

10: power conversion unit 20: control unit

30 light emitting element 12 energy storage unit

14 rectification part 16 smoothing part

22: current detector 24: voltage detector

26 pulse width modulation control unit 28 switching unit

D41 ~ D45, D51, D71, D72: Diode

L41, L71, L72: Inductors

C41, C71 ~ C74: Capacitor

Q41, Q71: switching element

Ri, Rs, Rf, R61 ~ R65, R71 ~ R83: Resistance

Claims (11)

A power converter converting input power into power for driving a light emitting device; And And a controller for detecting a current related to driving of the light emitting device to control output power of the power converter. The method of claim 1, wherein the power conversion unit An energy accumulator disposed between an input terminal of the power converter and a first output terminal of the power converter; A rectifier disposed between the energy accumulator and the first output terminal; And And a smoothing unit connected in parallel between the first output terminal and the second output terminal of the power converter, wherein the second output terminal is commonly connected to the input terminal. The method according to claim 2, The control unit, A current detector for detecting a current associated with driving the light emitting device; A pulse width modulation controller configured to generate a pulse width modulated signal corresponding to the current detected by the current detector; And And a switching unit connected between the energy accumulation unit and the pulse width modulation control unit to change an amount of current flowing under control of the pulse width modulation control unit. The method according to claim 3, wherein the current related to the driving of the light emitting element, And a current supplied to the light emitting device, a current flowing in the energy storage unit, and a current flowing in the switching unit. The method of claim 4, wherein the control unit And a voltage detector for detecting an output voltage of the power converter. A bridge rectifier for receiving full-wave rectification by receiving AC power; An inductor positioned between an output terminal of the bridge rectifier and a first input terminal of the light emitting device to provide power to drive the light emitting device; A capacitor connected to the first input terminal and the second input terminal of the light emitting device in parallel to stabilize a current supplied to the light emitting device; A rectifier diode for preventing a reverse current from flowing through the light emitting device; A switching element for controlling power supplied from the inductor to the light emitting element; And And a pulse width modulation controller for controlling the current of the switching element in response to the change of the current related to the driving of the light emitting element. The method according to claim 6, wherein the current related to the driving of the light emitting element, And a current supplied to the light emitting device, a current of the inductor, and a current of the switching device. The method of claim 7, And a current detector for detecting at least one of a current supplied to the light emitting device, a current of the inductor, and a current of the switching device. The method according to claim 8, And a voltage detector for detecting an input voltage of the light emitting device. A light emitting device driving method using a buck boost circuit and a pulse width modulation control circuit, Supplying power to the light emitting device; Detecting any one of a current supplied to the light emitting device, an internal current of the buck boost circuit, and a current of a switching transistor of the pulse width modulation control circuit; Generating a pulse width modulated signal corresponding to the detected current; And And controlling an input current of the light emitting device by the generated pulse width modulation signal. The method of claim 10, wherein the light emitting device driving method Detecting an input voltage of the light emitting device; Generating a pulse width modulated signal corresponding to the detected voltage; And And controlling the input voltage of the light emitting device by the generated pulse width modulation signal.

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