KR100994456B1 - Light emitting diode driver for phase control - Google Patents

Abstract

A light emitting diode driver for phase control is disclosed. The LED driver for phase control includes a bridge rectifier circuit for full-wave rectification by applying an AC current controlled in phase, a transformer for transforming an output of the bridge rectifier circuit, and a transformer for detecting magnetic flux and providing an operating current. It operates by receiving the operating current from the magnetic flux detector and the transformer magnetic flux detector, and adjusts the duty ratio of the pulse width modulated signal according to the input signal, the detected current, and the magnetic flux detected by the transformer magnetic flux detector, and outputs the pulse width modulated signal. A control unit for controlling the primary side current of the transformer controlled by the pulse width modulation signal output from the control unit, a current detection unit for detecting a current flowing in the switching transistor unit and providing the detected current as a detection current to the control unit; Depends on the change of voltage of input terminal of light emitting diode During operation period of the optical coupler, and a light emitting diode to increase or decrease the input signal over the control, a target effective power corresponding to the phase control and a constant current circuit for light modulation to be applied to the LED.

Light Emitting Diode, Driver, Dimming, Phase Control

Description

Light emitting diode driver for phase control {LIGHT EMITTING DIODE DRIVER FOR PHASE CONTROL}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a phase control light emitting diode driver, and more particularly, to a phase control light emitting diode driver capable of performing dimming by controlling an effective value of an output through a phase controller without using a separate communication line.

A light emitting diode (hereinafter referred to as an LED) has a PN junction structure using a semiconductor. When a voltage is applied to the PN junction in a forward direction, the energy of electrons is converted into light energy to emit light. The device was first developed in 1962 by Nick Horoniak of the University of Illinois and has been used in a variety of applications such as lighting and light sources for backlight units in liquid crystal displays (LCDs). It is attracting attention as a light source to replace a light bulb.

Such light emitting diodes, when used for lighting, have a need for dimming according to a user's needs, and in particular, dimmers are often used for high-quality lighting. Many dimmers currently in use are in the form of phase control, and are controlled by controlling the effective value of the output. This dimming method is not a problem when used for a light source that emits light using Joule heat, such as a conventional incandescent lamp or a halogen lamp.

However, when such a dimming method is used for the LED light source, there is a problem that the actual dimming function is not performed at all because the constant current driver circuit is used for the LED light source. Accordingly, there is a problem in that a separate communication line or power line communication (Power Line Communication, PLC) must be used to perform the dimming function, and thus the cost increases.

Therefore, there is a need for a method capable of performing a dimming function while improving the above problems in an LED light source using a constant current circuit.

The problem to be solved by the present invention is to provide a phase control LED driver for performing a substantially dimming function in the LED light source is used a constant current circuit.

Another problem to be solved by the present invention is to provide an LED driver for phase control that can reduce the inconvenience of using a separate communication line or power line communication to perform dimming of the LED light source, thereby reducing the cost.

According to an aspect of the present invention, a phase control light emitting diode driver according to an aspect of the present invention provides a constant current to a light emitting diode side during a period in which phase controlled input power is applied, and applies a phase controlled AC current to perform full wave rectification. A bridge rectifier circuit, a transformer for transforming an output of the bridge rectifier circuit, a transformer magnetic flux detector connected to the transformer to detect magnetic flux, and providing an operating current, and receiving and operating the operating current from the transformer magnetic flux detector. A controller for adjusting a duty ratio of a pulse width modulated signal and outputting the pulse width modulated signal depending on an input signal, a detected current, and a magnetic flux detected by the transformer magnetic flux detector, and the pulse width modulated signal output from the controller Switching to regulate the primary side current of the transformer A current detector for detecting a current flowing through the transistor unit, the current being supplied to the controller as the detection current, an optocoupler for increasing or decreasing the input signal of the controller in response to a change in the voltage at an input terminal of the light emitting diode; And a constant current circuit for applying a constant current to the light emitting diode during a period corresponding to the phase control during the operation period of the light emitting diode.

Preferably, the light emitting diode may include a comparator connected to an input terminal of the light emitting diode to compare a reference voltage and output a comparison result to the optocoupler.

Preferably, the comparator comprises: a first comparator for comparing a voltage applied to a resistor connected to an input terminal of the light emitting diode and a first reference voltage, and a second comparator for comparing an input voltage of the light emitting diode and a second reference voltage And a reference voltage generator for generating the first reference voltage and the second reference voltage, wherein the constant current circuit comprises: the first comparator, the second comparator and Power may be provided to cause the reference voltage generator to operate.

Preferably, the constant current circuit, when the voltage applied to the light emitting diode during the operation period of the light emitting diode is smaller than the voltage for operating the first comparator, the second comparator and the reference voltage generator, A voltage for driving the first comparator, the second comparator, and the reference voltage generator may be provided.

Preferably, the constant current circuit, the first capacitor connected in parallel to the input terminal of the light emitting diode, the voltage applied to the light emitting diode during the operation period of the light emitting diode is the first comparator, the second comparator and the reference When less than a voltage for operating a voltage generator, the second capacitor providing a voltage for driving the first comparator, the second comparator and the reference voltage generator, and the comparison with the first input of the light emitting diode. The first input terminal may include a diode connected between the parts in a forward direction toward the comparator.

Preferably, the capacitance value of the first capacitor may be within ± 20% of the Cout value determined by the following equation.

≪ Equation &

Cout = (Iout * τ) / Vripple,

Cout: capacitance of the first capacitor, Iout: input current of the light emitting diode,

τ: period of the switching transistor section,

Vripple: Permissible output ripple voltage (peak to peak value).

According to another aspect of the present invention, there is provided a phase-controlled light emitting diode driver for supplying a constant current to a light emitting diode side during a phase-controlled input power, and applying a phase-controlled alternating current to full-wave rectification. A bridge rectifier circuit, a buck converter for converting the output of the bridge rectifier circuit to supply power for the operation of the light emitting diode, and an output of the bridge rectifier circuit to be applied to the light emitting diode according to the phase control. And a control signal generator for generating a control signal for pulse width modulation controlling the buck converter to provide power.

Preferably, the control signal generation unit is connected between the first output terminal of the bridge rectifier circuit and the first input terminal of the light emitting diode rectifier circuit for rectifying the output of the bridge rectifier circuit, and parallel connection to the rectifier circuit And a smoothing circuit for smoothing the output of the rectifier circuit, a voltage divider circuit for dividing the output voltage of the bridge rectifier circuit, and a voltage connected in parallel to the voltage divider circuit to limit the voltage divided by the voltage divider circuit. And a limit circuit, wherein the divided voltage and the limiting voltage may be applied as a control signal for pulse width modulation control of the buck converter.

The present invention provides an improved phase control light emitting diode driver, and has an effect of performing a substantially dimming function without using a separate communication line or power line communication in an LED light source in which a constant current circuit is used. Therefore, the present invention can reduce the inconvenience of using a separate communication line or power line communication to perform the dimming of the LED light source, it has the effect that can reduce the cost.

Hereinafter, with reference to the accompanying drawings, it will be described in detail preferred embodiments of the present invention. The following description and the annexed drawings are by way of example only and intended to help those of ordinary skill in the art to understand the present invention to which the present invention pertains. It should not be used to limit the scope of the law.

1 is a block diagram of an LED driver for phase control according to an embodiment of the present invention. Referring to FIG. 1, the phase control LED driver according to the present invention receives an alternating current controlled in phase and supplies a constant current provided to a light emitting diode for a controlled phase angle time, and includes a bridge rectifying circuit 120 and a transformer 130. ), The transformer magnetic flux detector 160, the optocoupler 170, the switching transistor unit 180, the current detector 150 that detects the primary side current of the transformer 130, the controller 140, and the constant current circuit 190. It includes. Furthermore, the phase control LED driver according to the present invention may further include an EMI (EletroMagnetic Interference) filter 112, a rectifier circuit 132, and a starting current supply unit 122. For better understanding, the present invention will be described with reference to FIGS. 1 and 5.

First, the phase control unit 110, which is not included in the phase control light emitting diode driver according to the present invention but is a means for performing phase control at the front end of the driver, is described with reference to FIG. 2 below. It is used to control the brightness of the LED which is the load by controlling the phase angle θ of AC ₁ ) by varying the effective power supplied to the load.

The EMI filter 112 is disposed at the front end of the bridge rectifier circuit 120 to remove noise on the power line. The EMI filter 112 is an impulse generated at the front end or the rear end of the electromagnetic interference filter 112, that is, externally or internally. Filter sex noise.

A bridge rectifier circuit 120 is a portion coming to rectifying the phase controlled AC input (AC _2), such a bridge phase through the rectifier circuit 120 controls the AC input (AC ₂₎ is rectified radio (full wave rectified The output is applied to AC ₃ ) transformer 130 side.

The starting current supply unit 122 is a part for supplying a predetermined starting current to the control unit 140 by receiving the full wave rectified output provided from the bridge rectifying circuit 120 to enable the control unit 140 to start.

The transformers T ₁ and 130 receive and rectify the rectified output from the bridge rectifier circuit 120 and are connected to the switching transistor unit 180 controlled by the control unit 140 by a pulse width modulation signal. To work.

The rectifier circuit 132 is a circuit for rectifying the output of the transformer 130.

The constant current circuit 190 allows a constant current to be applied to the light emitting diodes 210 for a time corresponding to the phase control through the phase controller 110 during the operation period of the light emitting diodes 210, and the light emitting diodes through the phase controller 110. This is the portion required for the actual dimming function of 210 to be performed. Here, the voltage applied to the light emitting diode 210 side, that is, the output of the phase control light emitting diode driver exhibits a waveform characteristic of high frequency having a frequency corresponding to the switching frequency of the switching transistor unit 180 or the output of the rectifying circuit 132. .

The transformer magnetic flux detector 160 is coupled to the transformer 130 to detect the magnetic flux of the transformer 130. Thus, the transformer magnetic flux detector 160 determines the set time point of the pulse width modulated signal for controlling the switching transistor unit 180. In addition, the current provided from the output terminal of the transformer 130 to which the transformer magnetic flux detecting unit 160 is rectified is provided as an operating current to the control unit 140. An example of rectifying and providing the controller 140 as an operating current is illustrated in the circuit diagram of FIG. 5 below, and thus will be described in detail in FIG. 5.

Since the circuit portion for providing such an operating current is connected in parallel between the output terminal of the transformer 130 and the controller 140, the portion for providing such an operating current is also included in the transformer magnetic flux detector 160 below. It will be described as.

The node in which the operating current is provided from the transformer flux detection unit 160 to the control unit 140 and the node in which the starting current is provided from the starting current supply unit 122 to the control unit 140 are commonly connected to one pin of the control unit 140. do. Therefore, the starting current is provided at the start of the control unit 140, and the operating current is continuously supplied thereafter.

The comparator 200 is for controlling the current flowing through the input terminal of the light emitting diode 210. The comparator 200 is a voltage applied to a resistor connected between the output terminal of the light emitting diode driver and the input terminal of the light emitting diode 210. This is a part for comparing the reference voltage of. In addition, the comparator 200 may further compare the input voltage of the light emitting diode 210 with the second reference voltage. Thus, when the light emitting diode 210 is opened, it is possible to prevent the overvoltage from being applied to both ends of the input terminal of the light emitting diode 210.

The optocoupler 170 increases or decreases a current detected according to a voltage at an input terminal of the light emitting diode 210. That is, the optocoupler 170 adjusts the duty ratio of the pulse width modulated signal by increasing or decreasing the current flowing through R ₂ of FIG. 5 according to the comparison result of the comparator 200. One end of the transistor constituting the optocoupler 170 is connected together to a node provided with an operating current, and changes the current flowing in R ₂ of FIG. 5 depending on the output of the comparator 200 to input the input of the controller 140. A path for changing the voltage (voltage of pin 1 of the controller in FIG. 5) is formed.

The switching transistor unit 180 is controlled by the pulse width modulation signal to adjust the primary side current of the transformer 130.

The current detector 150 is a part for detecting a current flowing through the switching transistor unit 180. That is, the current detection unit 150 detects the current flowing through the switching transistor unit 180, and the control unit 140 determines the reset point of time of the pulse width modulation signal.

The controller 140 is operated by receiving a predetermined starting current from the starting current supplying unit 122, and is operated by receiving an operating current from the transformer magnetic flux detecting unit 160, and detecting the current and the current detecting unit by the optocoupler 170. The switching transistor unit 180 is controlled by adjusting the duty ratio of the pulse width modulated signal depending on the detection current by the 150 and the magnetic flux detected by the transformer magnetic flux detecting unit 160. For example, the control unit 140 is L6560, L6561, L6562, L6563 of Onst Microelectronics, NCP1606, NCP1601 of ON Semiconductor, UC3852, UC3853, UC3854, UC28019, UCC28060 of Texas Instruments, ML4810, ML4812, ML4821, of Fairchild. SG6980 and the like, but is not particularly limited thereto.

Furthermore, the LED driver may further include a snubber circuit (see R ₁₀ , C ₄ , and D ₂ of FIG. 5) for protecting the switching transistor unit 180. The snubber circuit is connected to the primary side circuit of the transformer 130 between the bridge rectifier circuit 120 and the switching transistor unit 180.

The constant current circuit 190 is a portion for providing a current corresponding to the output of the bridge rectifying circuit 120 to the light emitting diode during the period in which the output of the bridge rectifying circuit 120 appears. That is, the constant current circuit 190 controls the phase of the sine wave AC input AC ₁ (to maintain the voltage only for θ time) so that the effective power is varied and supplied to the light emitting diode 210 on the load side. For this purpose, a small capacitor (C ₇ of FIG. 5) is used. This will be described in detail with reference to FIGS. 2 to 4 below.

First, the operation of the LED driver based on the voltage comparison in the comparator 200 without considering the phase control aspect, will be described. The voltage of the first input terminal (OUT ₂ of FIG. 5) of the LED 210 is briefly described. When the first reference voltage (V _{ref1 in} FIG. 5) is smaller than the first reference voltage (V _{ref1 in} FIG. 5), the resistance value of the optocoupler 170 increases and the pulse width modulated signal output from the controller 140 to control the switching transistor unit 180 is increased. Duty ratio increases. As a result, the output of the light emitting diode driver increases.

On the contrary, when the voltage is compared in the comparator 200, when the voltage of the first input terminal OUT ₂ of FIG. 5 is greater than the first reference voltage V _ref1 of FIG. 5, the optocoupler ( As a result, the resistance value of 170 decreases and the duty ratio of the pulse width modulated signal output from the controller 130 decreases, so that the output of the LED driver decreases.

Therefore, the comparison control unit 200 achieves a current control loop that can increase or decrease the driving current of the light emitting diode 210 within a predetermined range.

In addition, when comparing voltages in the comparator 200, when the divided voltage (voltage applied to R ₁₂ in FIG. 5) of the input voltage of the light emitting diode 210 is smaller than the second reference voltage (V _{ref2 in} FIG. 5), The resistance value of the coupler 170 increases, and the duty ratio of the pulse width modulated signal output from the controller 140 to control the switching transistor unit 180 increases. As a result, the output of the light emitting diode driver increases.

On the contrary, in the voltage comparison in the comparator 200, when the divided voltage of the input voltage of the light emitting diode 210 is greater than the second reference voltage (V _ref2 of FIG. 5), the resistance value of the optocoupler 170 decreases. In addition, the duty ratio of the pulse width modulated signal is reduced, and the voltage at the output terminal of the light emitting diode driver 100 is reduced.

As such, a voltage control loop for adjusting the light emitting diode driver output is formed through the comparison in the comparator 200, so that the light emitting diode driver outputs the output voltage of the light emitting diode driver when the light emitting diode 210 is opened or disconnection occurs. This can reduce excessive problems.

FIG. 2 is a diagram illustrating a graph for explaining the principle of a dimmer by phase control, and FIG. 3 is a diagram showing graphs of output waveforms of a phase control light emitting diode driver according to an exemplary embodiment of the present invention.

Referring first to Figure 2, the principle of the dimmer by the phase control is a principle of controlling the brightness by controlling the phase angle of the sine wave alternating current large or small by varying the effective power supplied to the load. In FIG. 2, the hatched portion is a phase controlled portion that is full-wave rectified through the bridge rectifier circuit 120. Thus, if the θ is large, the effective power delivered to the load side is increased, so the load power will increase. If the θ is small, the effective power delivered to the load side will be small, so the load power will be reduced.

3 (a) is the same as FIG. 2, and only the hatched portion is transmitted to the light emitting diode side through phase control. That is, when the AC power is applied and phase controlled, the light emitting diode is turned on only for the phase control angle θ time. When the value of θ is changed, the ratio of the lighting time and the unlit time of the light emitting diode is changed to be dimmed.

FIG. 3 (b) shows an AC waveform (AC ₃ of FIG. 5), which is full-wave rectified through the bridge rectifying circuit 120 after phase control. That is, the input AC power source AC ₁ is phase-controlled and full-wave rectified to show a waveform as shown in FIG. 3B, and the hatched portion is converted to DC through a series of conversion processes by subsequent stages.

FIG. 3C is a view schematically showing a waveform after the AC waveform (AC ₃ of FIG. 5), which has been subjected to full-wave rectification, passes through the constant current circuit 190. Since DC operation characteristics of the LED 210 should be considered, input of a DC waveform to the LED 210 is preferable. However, as described above, when the ripple waveform as shown in FIG. 3 (b) is made close to the ideal DC waveform by using a smoothing circuit or other constant current circuit, the dimming function through phase control does not operate at all.

Therefore, as shown in (c) of FIG. 3, the DC waveform (DC of FIG. 5) is output through the constant current circuit 190 to correspond to the AC waveform that is full-wave rectified within one period. The direct current waveform here is not a direct current in a strict sense, but the dimming by the control unit 110 and the section T ₁ without output to the load side within one period corresponding to the input AC power source AC1 are effective. Is a waveform having an interval T ₂ including an essential high frequency (which has a time constant?). However, in terms of waveforms input to the light emitting diodes 210 operating in a direct current environment, they are named as direct current waveforms (DC) for convenience of description.

Although not specifically illustrated in FIG. 3C, the half cycle T ₁ + T ₂ of the waveform may be viewed as shown in FIG. 4D. Of course, the high frequency ripple is exaggerated and the frequency is reduced for ease of explanation. For example, when the frequency of the AC power source is 60 Hz, the half cycle (T ₁ + T ₂ ) may be 120 Hz as shown in FIG.

4 illustrates an envelope during a period corresponding to a half period T ₁ + T ₂ of the output of the constant current circuit 190 in FIG. 1, a frequency characteristic of the switching transistor unit 180, and a rectification circuit 132 of FIG. A graph showing frequency characteristics and output voltage characteristics of the constant current circuit 190.

Referring to FIG. 4A, the peaks of the currents at the output terminal of the constant current circuit 190 (main current peak value envelope g ₂ and negative current peak value envelope g ₁ ) are shown, and the average primary Current g ₃ is shown. As can be seen from the operation of the light emitting diode driver, the time constant τ of the high frequency coincides with the on-off period of the switching transistor unit 180 or the on-off period of the rectifier circuit 132. The on-off period of the switching transistor 180 or the on-off period of the rectifier circuit 132 is small at a low magnitude of voltage within one period, as shown in (b) or (c) of FIG. 4. Is large in size. That is, the on-off period tau is as follows.

τ _min ≤ τ ≤ τ _max

The on-off period τ is not constant, and is relatively large (largest period τ _max ) in a region where the peak value in the main current peak envelope g ₂ or the negative current peak envelope g ₁ is high as described above. In the lower intervals, they appear relatively small (the smallest period is defined as τ _min ).

In addition, the constant current circuit 190 has a section in which the output AC ₃ of the bridge rectifying circuit 120 does not appear, or the output of the corresponding constant current circuit 190 as shown in FIGS. 3B and 3C. In the section where there is no output in the waveform DC, power for driving the comparator 200 must be supplied separately. Accordingly, in this case, the constant current circuit 190 further performs a function of allowing the LED driver to operate normally by separately supplying power for driving the comparator 200.

As such, the phase control light emitting diode driver according to the present invention is provided with a constant current circuit 190, so that the dimming function does not work properly due to the constant current characteristics supplied to the light emitting diodes even though the phase control is performed to perform the conventional dimming function. Therefore, it is possible to improve the problem of using a separate additional circuit, for example, communication line or power line communication.

FIG. 5 is a circuit diagram of the phase control light emitting diode driver of FIG. 1. A light emitting diode driver for phase control according to the present invention will be described in detail below with reference to FIGS. 1 to 5. For ease of understanding, the following description has been given together with reference numerals of corresponding components in FIGS. 1 and 5.

First, since the phase controller 110 is not shown in FIG. 5, the phase-controlled AC input AC ₂ as described with reference to FIG. 1 may be regarded as corresponding to IN ₁ and IN ₂ .

EMI filter 112 includes capacitors C ₁₁ , C ₁₂ , C ₁₃ , C ₁₄ and inductor L ₁ . A fuse F ₁ may be further included between the AC input AC ₂ and the EMI filter 112 to protect the LED driver.

Capacitors C ₁₂ and C ₁₃ secure the ground voltage and remove impulsive noise from the outside. Capacitors C ₁₁ , C ₁₄ and inductor L ₁ form a low pass filter (LPF). In particular, the inductor L ₁ is wound so that the primary side and the secondary side have the same phase to remove the in-phase component.

The output of the EMI filter 112 is full-wave rectified by the bridge rectifier circuit 120. Bridge rectification circuit 120 may be composed of four diodes as shown, this bridge rectification circuit 120 full-wave rectified the output of the EMI filter 112, the full-wave rectified bridge rectifier circuit 120 of The output is fed to the rear end in the form of a ripple. The high frequency component induced at the output of the full-wave rectified bridge rectifying circuit 120, that is, the ripple output AC ₃ of the N ₁ node, is removed by the capacitor C ₁ . The capacitor C ₁ is preferably a small film capacitor, and may have a size of about ₁ μF, but is not particularly limited to a capacitor of this capacity.

Looking at the resistor (R ₆ ) and the capacitor (C ₅ ) constituting the starting current supply unit 122, when the voltage of the N ₁ node is supplied, the charge is charged to the capacitor (C ₅ ) through the resistor (R ₆ ), the node The voltage of N ₅ , that is, the voltage applied to pin 8 of the controller 140 increases. When the voltage applied to pin 8 of the controller 140 continues to rise and rises to a voltage sufficient to start the controller 140, the operation of the controller 140 is started.

When the control unit 140 operates to output the pulse width modulation signal PWM to pin 7 as an output terminal, the switching transistor unit 180 is turned on. That is, as illustrated, the switching transistor unit 180 may include a resistor R ₇ and a switching transistor Q ₁ , and a pulse width modulation signal output to pin 7 which is an output terminal of the control unit 140. Turns on the switching transistor Q ₁ through a resistor R ₇ .

Then, the main current is the source of the transformer node connected to the primary winding (130a) of _{(T 1, 130) (N} 1, N 6), a switching transistor (Q ₁₎ a drain terminal, a switching transistor (Q ₁₎ of the terminal, It flows through the path of the resistor R ₉ . This current induces the output voltage to the secondary winding 130b of the transformers T ₁ and 130. The output induced on the secondary winding 120b side is rectified by the rectifier circuits D ₄ and 122. The rectifier circuits D ₄ and 122 may be formed of one diode D ₄ , as shown.

After rectification by the rectifier circuits D ₄ and 122, it is then smoothed by the capacitor C ₇ of the constant current circuit 190 to provide a direct current DC to the light emitting diode 210 side.

Transformers T ₁ and 130 are primary windings 130a connected between node N ₁ and node N ₆ , and secondary windings 130b connected between node N ₉ and node N ₄ . And further, it further comprises an auxiliary winding (130c) connected between the node (N ₈ ) and node (N ₂ ).

Therefore, when the switching transistor Q ₁ is turned on and current flows through the drain terminal and the source terminal thereof, the voltage is induced in the auxiliary winding 130c of the transformers T ₁ and 130. The voltage induced by the auxiliary winding 130c is rectified by the diode D ₃ to provide the operating voltage V _CC of the controller 140 to the node N ₅ connected to the pin 8 of the controller 140. do. The operating voltage V _CC of the controller 140 is applied to the node N ₅ , in which case the current input to the eighth pin of the controller 140 has been expressed as the operating current above.

The resistor R ₂₇ is a component for detecting the magnetic flux of the transformers T ₁ and 130 through the output induced by the auxiliary winding 130c and generates a zero current of the transformers T ₁ and 130. It is detected and reflected in the pulse width modulation signal for controlling the switching transistor Q ₁ .

In FIG. 1, the transformer magnetic flux detector 160 for providing an operating current to the controller 140 and detecting the magnetic flux of the transformers T ₁ and 130, which are described as one component, has a resistance R as shown in FIG. 4. ₂₇ ), and may be seen to include a diode D ₃ and a capacitor C ₅ .

When the operating voltage V _CC of the control unit 140 is applied to the node N ₅ through the series of operations as described above, the starting current supply to the control unit 140 by the starting current supply unit 122 is stopped. That is, substantially no current flows through the resistor R ₆ of the starting current supply unit 122.

The resistor R ₁₀ , the capacitor C ₄ , and the diode D ₂ constitute a snubber circuit. The snubber circuit is connected in parallel to the primary winding 130a of the transformers T ₁ and 130 between the node N ₁ and the node N ₆ . This switch naebeo circuit, the transformer as a circuit for suppressing them in the event of excessive spike voltage exceeding the rating of the switching transistor (Q ₁₎ by the magnetic force of (T _1, 130), a switching transistor (Q ₁₎ Function to protect

The current detector 150 including the resistor R ₈ and the resistor R ₉ is a portion for detecting a current flowing through the switching transistor Q ₁ and applying it to the fourth pin of the controller 140. That is, the current detector 150 is a voltage applied to the fourth pin of the controller 140 through the resistor R ₈ by the resistor R ₈ and the resistor R ₉ , and is applied to the resistor R ₉ . Detects whether the flowing current is a predesigned current.

The resistor R ₁ and the resistor R ₅ are portions for dividing the voltage rectified by the bridge rectifying circuit 120, that is, the voltage at the node N ₁ , to be provided to the controller 140. The capacitor C ₂ connected in parallel to the resistor R ₁ is a small capacitor for noise reduction. In addition, the resistor R ₄ and the capacitor C ₃ are stabilizing elements for preventing oscillation of the components in the controller 130.

The comparator 200 may include a reference voltage generator 202, a first comparator 204, and a second comparator 206. The comparison unit 200 may compare the voltage of the output terminal (the input terminal of the light emitting diode 210) OUT ₂ of the driver of the phase control light emitting diode with the first reference voltage V _ref1 , and further, the light emitting diode 210. The input voltage (divided by the resistor R ₁₁ and the resistor R ₁₂ ) and the second reference voltage (V _ref2 ) can be further compared.

In the former case, the voltage of the input terminal OUT ₂ of the light emitting diode 210 and the first reference voltage V _ref1 are compared by the first comparator 204 of the comparator, and in the latter case, the light emitting diode 210 The divided voltage of the input voltage OUT ₁ and OUT ₂ and the second reference voltage Vref ₂ are compared by the second comparator 206 of the comparator. The second reference voltage Vref _{2 is} provided from the reference voltage generator 202, and the first reference voltage Vref ₁ is the second reference voltage Vref ₂ by the resistor R ₁₅ and the resistor R ₁₆ . Is the partial pressure of. The reference voltage generator 202 receives the voltage of the input terminal OUT ₁ of the light emitting diode 210 to provide the precision reference voltages Vref ₁ and Vref ₂ to the comparators 204 and 206.

Subsequently, referring to the operation after the secondary winding 130b of the transformers T ₁ and 130, the output voltage, that is, the input voltage of the light emitting diode 210 (the voltage between the OUT ₁ stage and the OUT ₂ stage) is determined by the resistance R _11. ) Is divided by the resistor R ₁₂ and applied to the inverting input of the second comparator 206, and the second reference voltage provided from the reference voltage generator 164 is provided to the non-inverting input of the second comparator 206. V _ref2 ) is applied.

First, in the first comparator 204, the voltage of the input terminal OUT ₂ of the light emitting diode 210, which is a voltage detected by the resistor R ₁₃ and proportional to the output current, is determined by the first reference voltage V _ref1 . In comparison, when the voltage at the input terminal OUT ₂ is lower than the first reference voltage V _ref1 , the voltage at the output terminal OP ₂ of the first comparator 204 is increased. When the voltage at the output terminal OP ₂ increases, the current flowing to the outputs of the resistor R ₁₄ , the output terminal OP ₁ , the output terminal OP ₂ , and the first comparator COM ₁ decreases, thereby causing the optocoupler. The LED of ISO ₁ darkens and flows to the transistor-side current of the optocoupler ISO ₁ (i.e., node N ₅ , the transistor of optocoupler ISO ₁ , resistor R ₂ and node N ₂ ). The current) decreases to lower the voltage across the resistor R ₂ . As a result, the voltage input to pin 1 of the controller 130 is lowered, thereby increasing the duty ratio of the pulse width modulated signal output to pin 7, thereby increasing the output voltage of the driver.

On the contrary, when the voltage of the input terminal OUT ₂ of the light emitting diode 210 is compared with the first reference voltage V _ref1 , and the voltage of the input terminal OUT ₂ is higher than the first reference voltage V _ref1 , the first comparator The voltage at the output terminal OP ₂ of 204 is lowered. When the voltage at the output terminal OP ₂ decreases, the current flowing to the output of the resistor R ₁₄ , the output terminal OP ₁ , the output terminal OP ₂ , and the first comparator 204 increases, thereby causing the optocoupler ( The LED of ISO ₁ ) becomes brighter, and the current at the transistor side of the optocoupler ISO ₁ increases to increase the voltage across the resistor R ₂ . As a result, the voltage input to pin 1 of the controller 140 is increased, thereby reducing the duty ratio of the pulse width modulated signal output to pin 7, thereby lowering the output voltage of the driver.

As such, a current control loop for controlling a current input to the light emitting diode 210 is formed, wherein the reference voltage V _ref2 generated by the reference voltage generator 202 is _directly connected to the first comparator 204. The reason for voltage-dividing using the resistors R ₁₅ and R ₁₆ without applying the inverting input is that, when the reference voltage is large, a resistor for detecting current at the output terminal of the driver, that is, the input terminal OUT ₂ of the light emitting diode 210, is used. (R _13), so the resistance (R ₁₃₎ must be larger, so the greater the voltage across, and the increase in the power loss resulting therefrom, is to prevent this.

Next, the second comparator 206, if the resistors (R _11, R ₁₂₎ compares the partial pressure and the second reference voltage (V _ref2) of, if the partial pressure is lower than the second reference voltage (V _ref2), the The voltage at the output terminal OP ₂ of the two comparator 206 is increased. When the voltage at the output terminal OP ₂ increases, the current flowing to the outputs of the resistor R ₁₄ , the output terminal OP ₁ , the output terminal OP ₂ , and the second comparator 206 decreases, thereby causing the optocoupler ( The LED of ISO ₁ darkens and the current flowing to the transistor side current of the optocoupler ISO ₁ (i.e., node N ₅ , the transistor of optocoupler ISO ₁ , resistor R ₂ and node N ₂ ). ) Decreases to decrease the voltage across the resistor (R ₂ ). As a result, the voltage input to pin 1 of the controller 140 is lowered, thereby increasing the duty ratio of the pulse width modulated signal output to pin 7, thereby increasing the output voltage of the driver.

On the contrary, when the divided voltage is higher than the second reference voltage V _ref2 , the voltage at the output terminal OP ₂ of the second comparator 206 is lowered. When the voltage at the output terminal OP ₂ is lowered, the LED of the optocoupler ISO ₁ becomes brighter, so that the transistor-side current of the optocoupler ISO ₁ increases to increase the voltage across the resistor R ₂ . As a result, the voltage input to pin 1 of the controller 130 is increased, thereby reducing the duty ratio of the pulse width modulated signal output to pin 7, thereby lowering the output voltage of the driver.

As such, since the second comparator 206 is a circuit for safety, the second comparator 206 is set to be slightly higher than the required voltage so that only the current control loop associated with the first comparator 204 is operated during normal operation. It is preferable to adjust the voltage set value such that the voltage control loop is performed so that the output voltage does not excessively increase when the light emitting diode 210 is disconnected or the output is opened.

To further simplify the circuit, the first comparator 204, the second comparator 206, and the reference voltage generator 202 constituting the comparator 160 may be integrated circuits configured in one package.

The constant current circuit 190 is a power for causing the comparator 200 to operate during a period in which the output of the first capacitor C ₇ and the bridge rectifier circuit 120 connected in parallel to the input terminal of the light emitting diode 210 does not appear. And a second capacitor C ₈ providing a forward connection between the first input terminal OUT ₁ of the light emitting diode 210 and the comparator 200 in the direction of the comparator 200 at the first input terminal OUT ₁ . Diode D ₅ .

The first capacitor C ₇ is a bridge rectifying circuit 120 during a section in which an output of the bridge rectifying circuit 120 appears, that is, a section in which an output appears within a section of the output after the rectifying circuits D ₄ and 120. The current corresponding to the output of the light emitting diode 210 is provided. Referring to (a) to (d) of FIG. 3, an AC output of phase controlled and full-wave rectified is applied to the light emitting diode 210 via the rectifying circuits D ₄ and 120. The high frequency is generated by C ₇ ) as shown in FIGS. 3 (c) and 4 (d), so that the phase control by the phase controller 110 becomes effective.

Here, the capacitance value of the first capacitor C ₇ is such that the current flowing through the output terminals OUT ₁ and OUT ₂ of the driver, that is, the input terminal of the light emitting diode 210, enables phase control to be effective in the phase controller 110. It must be appropriate. If the capacitance value of the first capacitor C ₇ is large, a voltage waveform as shown in FIGS. 3 (c) and 4 (d) cannot be output, and thus a separate communication line may be formed as in the conventional dimming method. It should be dimmed as described above.

The capacitance value of the first capacitor C ₇ is within ± 20% of the value determined by the following equation.

Cout = (Iout * τ) / Vripple.

Here, Cout is the capacitance of the first capacitor, Iout is the input current of the light emitting diode or the output current of the driver, τ is the charge that is charged to Cout in the period of the phase-controlled and full-wave rectified AC waveform load or light emitting diode 210 Is the switching period of the switching transistor Q ₁ , where Vripple is the peak-to-peak value as the allowable output ripple voltage.

For example, in the phase control, the period is 0.05 ms when the minimum frequency of the switching transistor Q1 is set at 20 KHz, and the period is 0.005 ms when the dead time of the actual rectifying circuit is about 10%. Assuming that the allowable output ripple is 0.5 V and the output current is 1 A, the capacity magnitude of Cout for phase control is Cout = 1 (A) * 0.005 (ms) / 0.5 (V) = 10 µF.

Meanwhile, the first comparator 204 and the second comparator 206 during the section in which the output of the bridge rectifying circuit 120 does not appear, that is, the section in which the output does not appear in one section of the output after the rectifying circuits D ₄ and 120. And a second capacitor C ₈ to provide a voltage to the reference voltage generator 202. After the second capacitor C ₈ charges the voltage during the period in which the output of the bridge rectification circuit 120 appears, the comparator 200 operates as described above during the period in which the output of the bridge rectification circuit 120 does not appear. Provide power for

In addition, when the second capacitor C ₈ provides power for operating the comparator 200, a diode D ₅ may be further provided to prevent a reverse current from flowing. That is, the diode D ₅ is forwardly connected between the first input terminal OUT1 of the light emitting diode 210 and the comparator 200 in the direction of the comparator 200 at the first input terminal OUT1.

Thus, the LED driver for phase control according to the present invention can perform a substantially dimming function without using a separate means for dimming in the LED light source using the constant current circuit.

6 is a circuit diagram of a phase control light emitting diode driver according to another embodiment of the present invention. According to another embodiment of the present invention, a phase control LED driver includes a bridge rectifier circuit for supplying a constant current to a light emitting diode side during a period in which phase controlled input power is applied, and receiving a phase controlled AC current to perform full wave rectification ( 610, the buck converter 620 for converting the output of the bridge rectifier circuit 610 to supply the power required for the operation of the light emitting diode, and the output of the bridge rectifier circuit 610 is applied to the light emitting diode corresponding to the phase control The control signal generator 630 generates a control signal for pulse width modulation control of the buck converter 620 to provide power to the buck converter.

The phase control light emitting diode driver illustrated in FIG. 6 is compared with the phase control light emitting diode driver illustrated in FIGS. 1 and 5, and the phase control light emitting diode driver illustrated in FIGS. 1 and 5 is a transformer (130 of FIG. 5). The phase control light emitting diode driver illustrated in FIG. 6 may be classified as a non-isolation type, whereas the primary side and the secondary side are separated from each other.

Referring to FIG. 6, a phase control light emitting diode driver according to another embodiment of the present invention includes a bridge rectifier circuit 610, a buck converter 620, and a control signal generator 630, and generates a control signal. The unit 630 includes a rectifier circuit D ₆₀₁ , a smoothing circuit C ₆₀₁ , voltage divider circuits R ₆₀₂ and R ₆₀₅ , and a limit circuit ZD ₆₀₁ .

The rectifier circuit D ₆₀₁ is connected between the first output terminal N ₆₀₁ of the bridge rectifier circuit 610 and the first input terminal N ₆₀₃ or OUT ₁ of the light emitting diode. That is, the rectifier circuit C ₆₀₁ is forward-connected from the node N ₆₀₁ toward the node N ₆₀₃ and rectifies the full-wave rectified voltage (voltage of the N ₆₀₁ ) and outputs the rectified voltage to the light emitting diode side. The rectifier circuit C ₆₀₁ may be composed of, for example, one rectifier diode.

A smoothing circuit (C ₆₀₁₎ is connected between the parallel connection in the rectifier circuit (D _601), i.e. node (N ₆₀₃₎ and nodes (N _602), the voltage across the node (N ₆₀₃₎ and nodes (N ₆₀₂₎ Smooth.

The divided circuits R ₆₀₂ and R ₆₀₅ are parts for dividing the output voltage of the bridge rectifying circuit 610. For example, a voltage divider circuit (R _602, R ₆₀₅₎ is two R ₆₀₂ and may be implemented as two resistors of the R _605, the output voltage that is a node of the bridge rectifier circuit (610) (N ₆₀₁₎ and nodes (N ₆₀₂₎ by dividing the voltage across it provides a light-control control signal by the pulse width control signal of the controller 640 of the buck converter (620).

Limit circuit (ZD ₆₀₁₎ is parallel connected to a voltage divider circuit (R _602, R _605), and limiting (limiting) the voltage divided by the voltage dividing circuit (R _602, R _605). For example, as shown in FIG. 6, in the limit circuit ZD ₆₀₁ , one zener diode is connected in parallel to the output of the voltage dividing circuits R ₆₀₂ and R ₆₀₅ provided to the controller 640 to control the divided voltage. 640 limits the voltage to the appropriate size required.

Thus, the phase control light emitting diode driver including these components is divided into voltages that are divided and limited, that is, voltages divided by the voltage dividing circuits R ₆₀₂ and R ₆₀₅ and limited by the zener diode ZD601. Is applied as a control signal for pulse width modulation control.

Therefore, even if a separate control means is not added, a dimming function can be realized through phase control by receiving a phase-controlled input power (power applied to IN ₁ and IN ₂ ) and applying a corresponding constant current to the light emitting diode side. It becomes possible.

Referring to FIG. 6, the operation of the non-isolated light emitting diode driver is _first applied to IN ₁ and IN ₂ . Here, a fuse F601 for safety of the circuit and a thermistor NTC _{1 for} preventing inrush current may be further included between the input terminals IN ₁ and IN ₂ and the bridge rectifier circuit 610. Referring to FIG. 3, when the phase-controlled input is shown in FIG. 3A, the ripple waveform propagated by the bridge rectifying circuit 610 may be shown in FIG. 3B.

Then, the output of the bridge rectifying circuit 610 is divided by the voltage dividing circuits R ₆₀₂ and R ₆₀₅ , and is limited by the zener diode ZD ₆₀₁ . The waveform of the voltage limited by the zener diode ZD ₆₀₁ may be as shown in FIG. 3C. The voltage waveform is input to pin 5 (PWMD) of the controller 640. Therefore, it is possible to control the light emitting diode according to the phase control angle θ without a separate control means for dimming.

On the other hand, the full-wave rectified output by the bridge rectifying circuit 610 is smoothed through the smoothing circuit (C ₆₀₁ ) via the rectifying circuit (D ₆₀₁ ).

The controller 640 may be one IC. For example, as illustrated in FIG. 6, the control unit 640 may be HV9910 manufactured by Supertex, but is not particularly limited to such an IC, and various product families for implementing a buck converter may be used.

When a voltage is applied to pin 1 (Vin) of the controller 640, the voltage is adjusted to a voltage suitable for use in the IC (for example, a voltage of about 7V), and is output to pin 6 (Vdd). Pin 7 (LD) is a linear dimming input. For example, an input of 0 to 250 mV can control the current of the LED in the range of 0 to 100%, where it can be used for fine adjustment of the current of the LED. have. Pin 2 (Cs) is an input pin for detecting the current flowing through the switching transistor (Q ₅₀₁ ).

For example, if power is applied and the output rises to a predetermined voltage (for example, about 7V) on pin 4, the switching transistor Q ₆₀₁ is turned on, and the current is a node N ₆₀₃ , light emission. Flow through a diode (connected to OUT ₁ and OUT ₂ (not shown)), inductor L ₆₀₁ , drain of switching transistor Q ₆₀₁ , source, and node N ₆₀₅ . In this case, the current gradually increases due to the inductance of the inductor L ₆₀₁ , and the increased current increases the voltage drop of the resistor R ₆₀₆ . When the voltage drop of the resistor R ₆₀₆ exceeds a predetermined voltage (for example, 250 mV), the output of pin 4 (Gate) is blocked by logic inside the controller 640. The switching transistor (Q ₆₀₁ ) is also cut off at the moment of shutdown, and the inertial current of the inductor (L ₆₀₁ ) is returned to the power supply terminal through the diode (D ₆₀₃ ) to increase energy use efficiency and protect the switching transistor (Q ₆₀₁ ) from transient voltages. You can do it. That is, when the switching transistor Q ₆₀₁ is cut off, the inductor L ₆₀₁ serves as a generator so that current is connected to the inductor L ₆₀₁ , the diode D ₆₀₃ , and the light emitting diodes OUT ₁ and OUT ₂ (not shown). Flows through the path).

In other words, when there is no control signal generator 630 in the phase control light emitting diode driver according to the embodiment of FIG. 6, only the buck converter 620 functions as a general buck converter to supply a constant current to the light emitting diode, and the buck converter 620. By inputting a control signal for pulse width modulation control to the fifth pin (PWMD) of the control unit 640 constituting the control unit to provide a constant current corresponding to the phase control to the light emitting diode side can effectively implement the dimming function.

The divided circuits R ₆₀₂ and R ₆₀₄ and the limit circuit ZD ₆₀₁ in FIG. 6 are just examples, and thus may be implemented in various ways. In addition, the circuit of the LED controller for phase control may be implemented in various ways without being limited to the circuit of FIG. 6 without departing from the scope of the present invention.

Thus, the LED driver for phase control according to the present invention extracts the LED blinking time from the phase control input and converts it into time control without using a separate means for dimming in the LED light source in which the constant current circuit is used, thereby realizing a dimming function. This can be done.

The light emitting diode driver for phase control according to the present invention as described above is not limited to the above embodiments, and can be variously modified and applied within the scope without departing from the basic principles of the present invention. It will be self-evident to those of ordinary knowledge.

1 is a block diagram of an LED driver for phase control according to an embodiment of the present invention.

2 is a diagram illustrating a graph for explaining the principle of a dimmer by phase control.

3 is a diagram illustrating graphs of output waveforms of a phase control light emitting diode driver according to an exemplary embodiment of the present invention.

FIG. 4 is a circuit diagram of the phase control light emitting diode driver of FIG. 1.

FIG. 5 is a circuit diagram of the phase control light emitting diode driver of FIG. 1.

6 is a circuit diagram of a phase control light emitting diode driver according to another embodiment of the present invention.

<Explanation of symbols for main parts of the drawings>

110: phase control unit 112: EMI filter

120: bridge rectifier circuit 130: transformer

132: rectifier circuit 122: starting current supply unit

140: control unit 150: current detection unit

160: transformer flux detection unit 170: optocoupler

180: switching transistor section 190: constant current circuit

200: comparison unit 210: light emitting diode

510: bridge rectifier circuit

Claims (8)

In the phase control light emitting diode driver for supplying a constant current to the light emitting diode side during the period of the phase-controlled input power is applied, A bridge rectifier circuit for receiving full-wave rectification by receiving an AC current controlled in phase; A transformer for transforming an output of the bridge rectifier circuit; A transformer magnetic flux detector coupled to the transformer to detect magnetic flux and provide an operating current; It operates by receiving the operating current from the transformer magnetic flux detector, and adjusts the duty ratio of a pulse width modulated signal according to an input signal, a detection current, and a magnetic flux detected by the transformer magnetic flux detector, and outputs the pulse width modulated signal. A control unit; A switching transistor unit controlled by the pulse width modulation signal output from the controller to adjust a primary side current of the transformer; A current detector for detecting a current flowing in the switching transistor and providing the detected current to the controller; An optocoupler configured to increase or decrease the input signal of the controller in response to a change in voltage at an input terminal of the light emitting diode; And And a constant current circuit for applying a constant current to the light emitting diode during a period of time corresponding to the phase control corresponding to the phase control during the operation period of the light emitting diode. The method according to claim 1, And a comparator for outputting a comparison result to the optocoupler after comparing the voltage at the input terminal of the light emitting diode with a reference voltage. The method of claim 2, wherein the comparison unit A first comparator for comparing a voltage applied to a resistor connected to an input terminal of the light emitting diode with a first reference voltage; A second comparator for comparing the divided voltage of the input voltage of the light emitting diode and a second reference voltage; And And a reference voltage generator configured to generate the first reference voltage and the second reference voltage. The method of claim 3, wherein the constant current circuit When the voltage applied to the light emitting diode is less than the voltage for operating the first comparator, the second comparator and the reference voltage generator during the operation period of the light emitting diode, the first comparator, the second comparator and And a phase control light emitting diode driver providing a voltage for driving the reference voltage generator. The method according to claim 4, wherein the constant current circuit A first capacitor connected in parallel to an input terminal of the light emitting diode; When the voltage applied to the light emitting diode is less than the voltage for operating the first comparator, the second comparator and the reference voltage generator during the operation period of the light emitting diode, the first comparator, the second comparator and A second capacitor providing a voltage for driving the reference voltage generator; And And a diode forwardly connected between the first input terminal of the light emitting diode and the comparator in the direction of the comparator at the first input terminal. The method according to claim 5, The capacitance value of the first capacitor is a phase control light emitting diode driver within ± 20% of the value determined by the following equation. &Lt; Equation & Cout = (Iout * τ) / Vripple Cout: capacitance of the first capacitor, Iout: input current of the light emitting diode, τ: period of the switching transistor section, Vripple: Permissible output ripple voltage (peak to peak voltage). delete In the phase control light emitting diode driver for supplying a constant current to the light emitting diode side during the period of the phase-controlled input power is applied, A bridge rectifier circuit for receiving full-wave rectification by receiving an AC current controlled in phase; A buck converter for converting an output of the bridge rectifier circuit and supplying power required for the operation of the light emitting diode; And A control signal generator for generating a control signal for pulse width modulation control of the buck converter to receive the output of the bridge rectifier circuit and provide power to the light emitting diode according to the phase control; The control signal generator A rectifying circuit connected between a first output terminal of the bridge rectifying circuit and a first input terminal of the light emitting diode to rectify an output of the bridge rectifying circuit; A smoothing circuit connected to the rectifying circuit in parallel to smooth the output of the rectifying circuit; A voltage divider circuit for dividing the output voltage of the bridge rectifier circuit; And A limit circuit connected in parallel to the voltage divider circuit for limiting a voltage divided by the voltage divider circuit, And the divided voltage and the limiting voltage are applied as a control signal for pulse width modulation control of the buck converter.

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