WO2012127515A1

WO2012127515A1 - Led lighting device

Info

Publication number: WO2012127515A1
Application number: PCT/JP2011/001632
Authority: WO
Inventors: 直人丸尾; 大澤　孝
Original assignee: 三菱電機株式会社
Priority date: 2011-03-18
Filing date: 2011-03-18
Publication date: 2012-09-27
Also published as: JP5490311B2; JPWO2012127515A1

Abstract

During a period of time when an output current is turned off and on and an LED light source (4) is dimmed and lit, a first switch (SW1) and a second switch (SW2) are opened when the light is turned off, and the operation of a DC/DC converter unit (3) is discontinued while the duty value and operating frequency of a switching element (Q0) during the immediately preceding time when the light is on are kept unaltered. When the light is turned on, the first switch (SW1) and the second switch (SW2) are shorted, the switching element (Q0) is actuated at the operating frequency and duty value maintained during the immediately preceding time when the light is off, and the operation of the DC/DC converter unit (3) is started.

Description

LED lighting device

The present invention relates to an LED lighting device that performs dimming lighting by passing an intermittent current through an LED (Light Emitting Diode).

As an in-vehicle light source, LEDs that are long-life and do not require maintenance are widely used instead of conventional tungsten light bulbs. The LED has a long lifetime and can secure the necessary brightness with a small amount of power, and can maintain a stable brightness by a simple control that supplies a constant current. Therefore, it is suitable as an in-vehicle light source. It is.

However, the brightness emitted by the LEDs varies greatly from one LED to another, and the light emission characteristics are not uniform with respect to the amount of current applied. Therefore, the brightness of the LED is often defined by the brightness when the LED is lit with the rated current.
Further, the emission color emitted by the LED also varies greatly depending on the individual LED, and the emission characteristics are not uniform with respect to the amount of current applied. For this reason, the light emission color of the LED is often defined by the light emission color when it is lit by the rated current, as well as the brightness.

In a lighting device that dims and lights an LED having a potential variation as described above, in order to cause each LED to emit light with a desired color and with uniform brightness. In addition, it is common to perform dimming lighting by intermittently energizing a current having a peak current as a rated current in a comb shape. For example,

Patent Documents

1 and 2 have been proposed as a configuration of a lighting device that performs dimming lighting by supplying an intermittent current to an LED.

JP 2006-49423 A (FIG. 6) JP 2010-176853 A

The constant current driving circuit according to Patent Document 1 has a configuration in which the output current of the DC / DC converter is intermittently turned on and off by the on / off operation of a switching element connected in series with the LED to dimm the LED. The purpose is to finely control the current when the switching element is turned on during the dimming lighting using a constant voltage control DC / DC converter. The DC / DC converter is controlled by intermittent oscillation. As a result, a large ripple was superimposed on the output current. Therefore, there is a problem that the output current does not become an ideal rectangular wave.

On the other hand, in Patent Document 2, in order to make the current rise steep when the switching element is turned on and energized during the dimming lighting period, the current is predetermined from the current rise point (first period T1). The duty value of the switching element of the DC / DC converter is uniformly increased until it increases to the value of (the first time point of the second period T2).
Incidentally, in Patent Document 2, a proportional integration means is included in a feedback control loop, and this proportional integration means integrates from the last time of the second period T2 to the first time of the second period T2 in the next period. Although the configuration for holding the term is described, the period until the current rises to a predetermined value at the rising point of the rectangular wave (the first time point from the first period T1 to the second period T2), that is, the Duty value In this increase period, an appropriate duty value is not supplied to the switching element.

When dimming lighting is performed by intermittent output current, the intermittent frequency needs to be intermittent to some extent early so as not to be recognized as flickering of light emission, and is practically about 100 Hz to 1 kHz. Further, the frequency of the on / off operation of the switching element of the DC / DC converter largely depends on the characteristics of the electronic unit used, and is practically about 100 kHz to 1 MHz.
Here, for example, if the intermittent frequency is 500 Hz, the operating frequency of the switching element is 500 kHz, and the output current during dimming lighting is 1/50 of the rated current, the DC / DC converter for dimming the LED The number of operations of the switching element is 500 kHz / 500 Hz / 50 = 20 (times).
Therefore, the DC / DC converter is required to output the target current by feeding back the output current while the switching element performs switching operation 20 times at 500 kHz. It is difficult to output a current with no excess or deficiency close to a rectangular wave by making the rise of the intermittent current steep.
For this reason, also in the case of Patent Document 2, if the period for increasing the duty value is short, feedback control may not be in time.

The present invention has been made to solve the above-described problems. When the current supplied to the LED is intermittently lit and dimmed, the current rises steeply while suppressing overcurrent, and the rectangular shape is reduced. The purpose is to supply an intermittent current close to a wave to an LED.

In the LED lighting device according to the present invention, the switching element is turned on and off at a predetermined operating frequency and duty value to generate a predetermined voltage for LED lighting from the power source, and the operation of the DC / DC converter unit The control unit controls the DC / DC converter unit when the LED light source is turned off when the LED light source is turned off during the period in which the LED light source is dimmed by interrupting the output current. When the operation of the DC / DC converter unit is stopped while the operating frequency and duty value of the switching element are held and the LED light source is turned on, the switching element is operated with the operating frequency and duty value held when the light source is turned off immediately before. It operates to start the operation of the DC / DC converter unit.

According to this invention, the operation of the DC / DC converter unit is stopped while maintaining the operating frequency and duty value of the switching element at the time of extinction when intermittent lighting is performed, and the operating frequency and duty value held at the time of the previous extinction during subsequent lighting. By operating the switching element to start the operation of the DC / DC converter unit, it is possible to supply an intermittent current close to a rectangular wave to the LED while making the rise of the current steep while suppressing the overcurrent. As a result, each of the LEDs can be dimly lit with uniform brightness and a prescribed light emission amount.

It is a circuit diagram which shows the structure of the LED lighting device which concerns on Embodiment 1 of this invention. 3 is a timing chart showing the operation of the LED lighting device according to Embodiment 1. 5 is a timing chart illustrating a first reference example having a configuration in which the LED lighting device according to Embodiment 1 is modified. 6 is a timing chart showing a second reference example having a modified configuration of the LED lighting device according to Embodiment 1. 6 is a timing chart illustrating a third reference example having a configuration in which the LED lighting device according to Embodiment 1 is modified. 10 is a timing chart showing a fourth reference example having a modified configuration of the LED lighting device according to Embodiment 1. It is a circuit diagram which shows the structure of the LED lighting device which concerns on Embodiment 2 of this invention. 6 is a timing chart showing the operation of the LED lighting device according to Embodiment 2. It is a circuit diagram which shows the structure of the LED lighting device which concerns on Embodiment 3 of this invention. It is a circuit diagram which shows the structure of the LED lighting device which concerns on Embodiment 4 of this invention.

Hereinafter, in order to explain the present invention in more detail, modes for carrying out the present invention will be described with reference to the accompanying drawings.
Embodiment 1 FIG.
An LED lighting device 1 shown in FIG. 1 is a device for lighting an LED light source 4 by using a DC voltage of a DC power source 2, and mainly includes a DC / DC converter (power source unit) unit 3, a control power source unit 5, and a control unit. 6. An input interface (hereinafter referred to as I / F) unit 7 is provided. The DC power source 2 is a power source that supplies a DC voltage to the DC / DC converter unit 3, and the DC voltage to the DC / DC converter unit 3 is supplied or cut off by the power switch 2a.

The LED light source 4 is configured by connecting a plurality of LEDs in series.
Since the emission color of the LED is defined by a predetermined current value (rated), the emission color changes when a current other than the specified current value is supplied, and the variation in the emission color variation among the individual LEDs is large. . Therefore, when the current value is decreased for dimming, it is difficult to obtain a desired light emission color and to make the light emission colors of a plurality of LEDs uniform.
Further, since the light emission amount of the LED is also defined by a predetermined current value (rated value), when a current other than the predetermined current value is supplied, the light emission amount changes nonlinearly, and the non-linear degree varies greatly between the individual LEDs. . Therefore, when the current value is reduced for dimming, it is difficult to obtain a desired light emission amount and to make the light emission amounts of a plurality of LEDs uniform.
Because of these characteristics, it is desirable to light (dim) the supplied current with a rectangular wave intermittently in a comb shape in order to lighten the LED.
Further, since the LED has a constant voltage characteristic, a current flows when the applied voltage exceeds a predetermined voltage, and no current flows when the applied voltage is lower than the predetermined voltage. Therefore, by stopping the DC / DC converter unit 3, the electric charge stored in the smoothing capacitor C0 is discharged and the output voltage is slightly lowered, but the current rapidly decreases and the output current is interrupted. Due to the constant voltage characteristics of the LED, the output current does not continue to flow slowly until the charge stored in the smoothing capacitor C0 disappears as when the DC / DC converter connected to the resistive load is turned off, and the DC / DC converter unit 3 The output current can be stopped relatively easily only by turning off the power.

The LED light source 4 is used as an in-vehicle light source (Daytime Running Light; head lamp with DRL and tail lamp with stop lamp) that switches between normal lighting and dimming lighting with a rated current, for example.
The headlamp with DRL performs rated lighting of the LED as a headlamp at night, and performs dimming lighting of the LED as DRL during the daytime.
The tail lamp with a stop lamp performs the rated lighting of the LED when the stop lamp (braking lamp) is lit, and performs the dimming lighting when the tail lamp (tail lamp) is lit.

The DC / DC converter unit 3 generates power for lighting the LED by the transformer 3a, the switching element Q0 composed of a MOS field effect transistor, the rectifier diode D0, and the smoothing capacitor C0. Further, as an arrangement for controlling the operation for generating the LED lighting power, an integration capacitor C1, an integration resistor R1, an error amplifier 3b, a waveform generator (comparator) 3c, a current detection resistor R2, a first switch SW1, and a second switch SW2 is provided. In the example of FIG. 1, the switch SW100 is illustrated, but this is a switch provided to explain the effect of the first embodiment in comparison with the conventional one (details will be described later). In form 1, it is an unnecessary part.

In the DC / DC converter unit 3, the on / off operation of the switching element Q0 is controlled by the operation signal output from the waveform generator 3c, the magnetic energy is stored in the transformer 3a, and the magnetic energy is discharged, which is generated in the transformer 3a. The voltage is rectified by a rectifier diode D0 and smoothed by a smoothing capacitor C0 to generate a DC voltage. Further, the DC / DC converter unit 3 includes a current detection resistor R <b> 2 that detects an output current supplied from the smoothing capacitor C <b> 0 to the LED light source 4, and the value of the output current is input to the control unit 6. The output voltage of the DC / DC converter unit 3 branches in the course of the path from the rectifier diode D0 to the LED light source 4, and is input to the control unit 6.
The transformer 3a may be a coil. The DC / DC converter unit 3 may be a charge pump type DC / DC converter that uses a capacitor instead of the transformer 3a.

A reference voltage V corresponding to a current value for turning on the LED light source 4 with a desired light emission amount is input to one input terminal of the error amplifier 3b, and the other input terminal is connected in series with the LED light source 4. The output current signal detected by the current detection resistor R2 is input via the integration resistor R1. Further, an integrating capacitor C1 is combined with the error amplifier 3b to constitute an integrator, and the output voltage is feedback-controlled so that the value of the output current signal approaches the reference voltage (target value) V, and the LED light source 4 is energized. Controls the output current.

The output voltage of the error amplifier 3b is input to one input terminal of the waveform generator 3c, a triangular wave having a predetermined frequency output from the control unit 6 is input to the other input terminal, and the triangular wave is sliced at the output voltage level. The rectangular wave operation signal is output to the gate terminal of the switching element Q0. The frequency of the operation signal (operation frequency) is determined by the frequency of the triangular wave output from the control unit 6, and the duty value is determined by the voltage output from the error amplifier 3b.

The first switch SW1 is provided between the output terminal of the waveform generator 3c and the gate terminal of the switching element Q0, and is short-circuited (turned on) by the operation of the control unit 6 to supply an operation signal to the switching element Q0. Open (off) and shut off.
The second switch SW2 is provided between the integrating resistor R1 and the error amplifier 3b. The second switch SW2 is short-circuited (ON) by the operation of the control unit 6 to supply an output current signal to the error amplifier 3b, and open (OFF) to shut off. To do. Since the output voltage of the error amplifier 3b is held by the integrating capacitor C1 while the second switch SW2 is opened (turned off), the value of the output voltage does not change. Since the operating frequency of the switching element Q0 is set by the frequency of the triangular wave from the control unit 6 and the duty value is generated from the triangular wave and the output of the error amplifier 3b, holding the output voltage of the error amplifier 3b is a duty value. Is equivalent to holding

The controller 6 generates a triangular wave having the same frequency as the operating frequency and inputs it to the waveform generator 3c. Further, the control unit 6 turns on the first switch SW1 and the second switch SW2 in the case of rated lighting, and continuously supplies output current from the DC / DC converter unit 3 to the LED light source 4, while In the case of dimming lighting, the first switch SW1 and the second switch SW2 are turned on / off, and the output current from the DC / DC converter unit 3 to the LED light source 4 is intermittently supplied at a predetermined cycle.
In addition, what is necessary is just to set beforehand the information of the intermittent period of the output current at the time of performing dimming lighting, and the lighting time width of each period as a function of the control part 6.
In addition, an instruction to perform rated lighting or dimming lighting is, for example, from the dimming instruction device 8 (such as a headlamp switch on a vehicle instrument panel) via the input I / F unit 7 to the control unit. 6 may be input.

When the LED light source 4 is intermittently lit (dimmed lighting), if there is no fluctuation as a load between the current lighting timing and the next lighting timing, the DC / DC converter unit 3 outputs at both timings. There is no change in the power to be transmitted, and therefore there is no change in the frequency and duty value of the operation signal of the switching element Q0. Therefore, the frequency and duty value of the operation signal of the switching element Q0 at the timing of lighting this time and the timing of lighting next are equal.
That is, between the timing of lighting this time and the timing of next lighting (while it is turned off), the frequency and duty value of the operation signal are held and it is preferable that the LED lighting device 1 does not change. Become.

The control that maintains and does not change the frequency and duty value of the operation signal at the timing when the operation of the DC / DC converter unit 3 is stopped has a constant voltage characteristic, and the current does not flow at the timing when the operation stops. It is suitable for controlling a DC / DC converter that supplies power to a load that does not flow. As described above, since the LED is a load having a constant voltage characteristic, control that maintains the frequency and duty value of the operation signal and does not change it is suitable as a control method of the DC / DC converter unit 3.

Next, the operation of the LED lighting device 1 according to the first embodiment will be described using the timing chart shown in FIG. The LED lighting device 1 is configured to use a first switch SW1 and a second switch SW2 to intermittently light the LED light source 4 by intermittently outputting an output current.

(1) Operation at timings T1 and T3 for turning off the LED light source 4 At timings T1 and T3, the control unit 6 turns off the first switch SW1 to cut off the operation signal to the switching element (FET) Q0 ( FIG. 2 (a)). At the same time, the control unit 6 also turns off the second switch SW2 and cuts off the output current signal input to the error amplifier 3b (FIG. 2B). Note that the switch SW100 is always turned on (FIG. 2C). 2D shows the output voltage of the DC / DC converter unit 3, and FIG. 2E shows the output current of the DC / DC converter unit 3.

Since the LED has a constant voltage characteristic as described above, when the first switch SW1 is turned off and the DC / DC converter unit 3 is stopped, the charge stored in the smoothing capacitor C0 is discharged and the output voltage is slightly reduced. Only the current decreases rapidly and the output current is interrupted.
Since the charge amount of the integration capacitor C1 can be held by turning off the second switch SW2, the output voltage of the error amplifier 3b does not change. During this extinguishing period, since the duty value of the operation signal generated by comparing the output voltage of the error amplifier 3b and the triangular wave of the control unit 6 does not change in the waveform generator 3c, immediately before the DC / DC converter unit 3 is stopped. The duty value of the operation signal supplied to the switching element Q0 is held (FIG. 2 (f)).

(2) Operation at timing T2 at which the LED light source 4 is turned on At timing T2, the control unit 6 turns on the first switch SW1 and supplies an operation signal to the switching element Q0. At the same time, the control unit 6 also turns on the second switch SW2, and inputs an output current signal to the error amplifier 3b.
When the first switch SW1 is turned on, the DC / DC converter unit 3 starts operating, and when the second switch SW2 is turned on, the charge amount of the integrating capacitor C1 starts feedback from the state (1). At this time, the duty value of the operation signal generated by comparing the output voltage of the error amplifier 3b and the triangular wave of the control unit 6 starts to change from the duty value when the operation signal was operating immediately before. That is, an error amplification operation by the error amplifier 3b is performed, and an output current feedback operation is started.
The switching element Q0 repeats the on / off operation according to the supplied operation signal, and the output voltage value or output current value to the LED light source 4 is controlled by the duty ratio.

In each period of rising operation (timing T2 in FIG. 2) when the LED light source 4 is intermittently lit by repeating the operations (1) and (2) during the period when the output current is intermittently dimmed. The DC / DC converter unit 3 can be operated according to the immediately preceding Duty value. Therefore, as shown in FIG. 2E, an overcurrent does not occur, and an intermittent current close to a rectangular wave can be output. As a result, appropriate power can be supplied from the DC / DC converter unit 3 to the LED light source 4.

Next, a first reference example will be described using the timing chart shown in FIG. In this example, the switch SW100 shown in FIG. 1 is used, and the LED lighting device 1 is configured to have the same configuration as that of Patent Document 1 to perform dimming lighting. This switch SW100 is provided between the LED light source 4 and the current detection resistor R2, and is turned on / off by the operation of the control unit 6 to switch between current output to the LED light source 4 and output stop.
In the first reference example, the LED lighting device 1 does not have the first switch SW1 and the second switch SW2, that is, is always short-circuited (ON) (FIGS. 3A and 3B). .

(1) Operation at timings T1 and T3 for turning off the LED light source 4 At timings T1 and T3, the control unit 6 turns off the switch SW100 to cut off the output current (FIG. 3C). Due to the interruption of the output current during this extinguishing period, the duty value of the operation signal gradually increases in the feedback operation (FIG. 3 (f)). For this reason, the output voltage of the DC / DC converter unit 3 also rises (FIG. 3D).

(2) Operation at Timing T2 to Light LED Light Source 4 At timing T2, the control unit 6 turns on the switch SW100 and supplies an output current from the DC / DC converter unit 3 to the LED light source 4. At this time, the duty value rises due to the feedback operation while the lamp is turned off, and excessive charge stored in the smoothing capacitor C0 of the DC / DC converter unit 3 is released, so that a large overcurrent is supplied to the LED light source 4. (FIG. 3 (e)). As a result, each LED cannot be lit (dimmed) with uniform brightness or cannot be lit with a specified emission color, and the LED may be deteriorated or destroyed.

Next, a second reference example will be described using the timing chart shown in FIG. In this example, the LED lighting device 1 shown in FIG. 1 is configured to be dimly lit using the first switch SW1 and the switch SW100.
In the second reference example, the LED lighting device 1 does not have the second switch SW2, that is, is always short-circuited (ON) (FIG. 4B).

(1) Operation at timings T1 and T3 at which the LED light source 4 is turned off At timings T1 and T3, the control unit 6 turns off the first switch SW1 to cut off the operation signal of the switching element Q0 (FIG. 4A )). At the same time, the control unit 6 also turns off the switch SW100 and cuts off the output current (FIG. 4C). Due to the interruption of the output current during this extinguishing period, the duty value of the operation signal gradually increases in the feedback operation (FIG. 4 (f)), but the DC / DC converter unit 3 is turned off by turning off the first switch SW1. It stops and the output voltage hardly rises (FIG. 4 (d)).

(2) Operation at timing T2 at which the LED light source 4 is turned on At timing T2, the control unit 6 turns on the first switch SW1 and supplies an operation signal to the switching element Q0. At the same time, the control unit 6 turns on the switch SW100 to supply an output current from the DC / DC converter unit 3 to the LED light source 4. At this time, an excessive current corresponding to the duty value increased by the feedback operation while the lamp is turned off is output (FIG. 4E), but excessive charge is accumulated in the smoothing capacitor C0 of the DC / DC converter unit 3. Therefore, the LED light source 4 is not supplied with an overcurrent as large as that shown in FIG. 3E (FIG. 4E). However, since overcurrent still occurs, there is a possibility that the LED is deteriorated due to this overcurrent.

As shown in the first reference example and the second reference example, in the LED lighting device 1 using the DC / DC converter unit 3, the switch SW100 is operated for intermittent lighting (dimming) of the LED light source 4. If the DC / DC converter unit 3 is stopped and operated, the operation is not sufficient.

Although a detailed description is omitted, a configuration in which only the first switch SW1 is turned on and off to stop and operate the switching element Q0 as in the timing chart (third reference example) shown in FIG. . In the case of this configuration, changes in the output voltage, output current, and operation signal shown in FIG. 5 are almost the same as in the case shown in FIG. 4 (second reference example), and the on / off of the switch SW100 is the basic of the LED lighting device 1. Almost no effect on operation.

Next, a fourth reference example will be described using the timing chart shown in FIG. In this example, the LED lighting device 1 shown in FIG. 1 operates and stops the DC / DC converter unit 3 by turning on and off the first switch SW1, and further performs soft start control when the DC / DC converter unit 3 operates. This is a configuration in which the LED light source 4 is dimmed by interrupting the output current.
In the fourth reference example, the LED lighting device 1 does not have the second switch SW2 and the switch SW100, that is, is always short-circuited (ON) (FIGS. 6B and 6C).

In the soft start control, the duty value is set to a low level when the operation of the DC / DC converter unit 3 is stopped, and the duty value is gradually increased immediately after the operation of the DC / DC converter unit 3 (timing T2). As a result (FIG. 6E), control is performed to gradually increase the output power (FIG. 6E). For this reason, the rise of the output current when the light is intermittently lit at the timing T2 becomes slow, and the current becomes insufficient. As a result, the LED light source 4 is dark, and the individual LEDs cannot be lit (dimmed) with uniform brightness, or cannot be lit with a specified emission color.
Therefore, the soft start control of the DC / DC converter unit 3 is not suitable for intermittent lighting for dimming the LED light source 4.

As described above, according to the first embodiment, the LED lighting device 1 is DC / DC which generates a predetermined voltage for LED lighting from the DC power source 2 by the switching element Q0 being turned on / off at the predetermined operating frequency and duty value. The control unit 6 includes a DC converter unit 3 and a control unit 6 that controls the operation of the DC / DC converter unit 3, and the control unit 6 switches the LED light source 4 in a period in which the LED light source 4 is dimmed by intermittently outputting the output current. In the case of turning off the light, the operation of the DC / DC converter unit 3 is stopped while maintaining the operating frequency and duty value of the switching element Q0 when the DC / DC converter unit 3 is operating by the previous lighting, and the LED light source 4 Is turned on, the switching element Q0 is operated at the operating frequency and Duty value held at the time of the previous turn-off, and the operation of the DC / DC converter unit 3 is performed. It was configured to start. For this reason, the next lighting is performed by the duty value held at the time of the last extinction, so that the rising of the current can be made steep while suppressing the overcurrent, and an intermittent current close to a rectangular wave is applied to the LED light source 4. Can supply. Therefore, each LED can be dimmed with uniform brightness, and each LED can be dimmed with a specified emission color.

Further, according to the first embodiment, the DC / DC converter unit 3 receives the DC power supply 2 and generates a predetermined output current, and rectifies the output current of the transformer 3a (or coil). A rectifying diode D0 for smoothing, a smoothing capacitor C0 for smoothing the output current of the rectifying diode D0, a current detection resistor R2 for detecting an output current signal energized to the LED light source 4, an output current signal detected by the current detection resistor R2 and a reference An error amplifier 3b that also serves as an integrator that integrates the difference of the voltage V and feedback-controls the output voltage so that the output current signal value is asymptotic to the reference voltage V that is the target value, and a triangular wave from the control unit 6 is converted into an error amplifier. And a waveform generator 3c that generates an operation signal having a duty value rectangular wave corresponding to the output voltage 3b and outputs the operation signal to the switching element Q0. The formation, the holding of the Duty value, was performed by holding the output voltage of the error amplifier 3b. Further, the DC / DC converter unit 3 blocks a first switch SW1 that cuts off an operation signal input from the waveform generator 3c to the switching element Q0, and a first switch that cuts off an output current signal input from the integration resistor R1 to the error amplifier 3b. The control unit 6 stops the operation of the DC / DC converter unit 3 by operating the first switch SW1 to cut off the operation signal input to the switching element Q0. The output voltage of the error amplifier 3b is held by cutting off the output current signal input to the error amplifier 3b by operating the switch SW2. For this reason, it is possible to supply an intermittent current close to a rectangular wave to the LED light source 4 by using the DC / DC converter unit 3 configured using analog components, and each LED has uniform brightness and prescribed light emission. Can be dimmed with color.

In the first embodiment, the operation signal input from the waveform generator 3c to the switching element Q0 is blocked by the on / off operation of the first switch SW1, but the control unit 6 stops the output of the triangular wave. The operation signal input from the waveform generator 3c to the switching element Q0 may be fixed to the off side by fixing the signal to the H level.
That is, the control unit 6 outputs a triangular wave to cause the waveform generator 3c to generate an operation signal for supplying and blocking the operation signal from the waveform generator 3c to the switching element Q0, which has been performed by the first switch SW1. Then, the control unit 6 stops the output of the triangular wave and fixes the operation signal generated by the waveform generator 3c to the off side.
In this case, the first switch SW1 is unnecessary, and an intermittent current close to a rectangular wave can be supplied to the LED light source 4 with a simple configuration. Therefore, the LED lighting device 1 can be miniaturized and the cost can be reduced.

Embodiment 2. FIG.
FIG. 7 is a circuit diagram showing the configuration of the LED lighting device 1 according to Embodiment 2 of the present invention. The same or corresponding parts as those in FIG. As shown in FIG. 7, the LED lighting device 1 according to the second embodiment is a third that short-circuits both ends of some LEDs of the LED light source 4 in addition to the first switch SW1 and the second switch SW2. Switch SW3.

In the second embodiment, the LED light source 4 is used as a DRL headlamp for in-vehicle use, and a plurality of LEDs are connected in series to form a passing light (low beam). A traveling light (high beam) is configured by the LED block 4b configured by connecting the two in series. Then, one terminal of the third switch SW3 is connected to a connection point where the LED block 4a and the LED block 4b are connected in series, and the other terminal of the third switch SW3 is connected to the LED block 4b and the current detection resistor R2. It is connected to a connection point connected in series.
When the third switch SW3 is turned on by the operation of the control unit 6, both ends of the LED block 4b are short-circuited, and only the LED block 4a for the passing lamp is connected to the LED lighting device 1. When the third switch SW3 is turned off, the short circuit is opened and the LED block 4a for the passing lamp and the LED block 4b for the traveling lamp are connected in series.

In this configuration, when the low light is turned on, both ends of the LED block 4b for running light are short-circuited and turned off, and only the low light LED block 4a is turned on. Further, when the traveling light is turned on, the short circuit at both ends of the traveling light LED block 4b is opened, and the passing light LED block 4a and the traveling light LED block 4b are lighted simultaneously.

Next, the operation of the LED lighting device 1 according to the second embodiment will be described using the timing chart shown in FIG. In the example of FIG. 8, the first switch SW1 and the second switch SW2 are used to intermittently turn on the LED block 4a for the passing lamp by intermittently outputting the output current, thereby constituting the DRL.

(1) Operation at timings T1 and T3 for turning off the LED block 4a for the passing lamp At timings T1 and T3, the control unit 6 turns off the first switch SW1 to cut off the operation signal to the switching element Q0. Then, the switching operation of the switching element Q0 is stopped (FIG. 8A). At the same time, the control unit 6 also turns off the second switch SW2 and cuts off the output current signal input to the error amplifier 3b (FIG. 8B). Further, the control unit 6 also turns off the third switch SW3 to open the short circuit of the LED block 4b for traveling light, and the DC block 4a for passing light and the LED block 4b for traveling light connected in series are connected to the DC. The output voltage of the DC converter unit 3 is applied.
By turning off the third switch SW3, the number of LEDs connected in series to the output terminal of the LED lighting device 1 increases, and the total forward voltage of the LED light source 4 increases, so that the DC / DC converter unit 3 The total forward voltage of the LED light source 4 becomes higher than the voltage of the smoothing capacitor C0 remaining when the operation is stopped. Therefore, the output current does not flow through the LED block 4a for the passing lamp and the LED block 4b for the traveling lamp, and the charge and voltage of the smoothing capacitor C0 are maintained as they are (FIG. 8 (d)).

(2) Operation at timing T2 for lighting the LED block 4a for the passing lamp At timing T2, the control unit 6 turns on the first switch SW1 to supply an operation signal to the switching element Q0. Start on / off operation. At the same time, the control unit 6 also turns on the second switch SW2, and inputs an output current signal to the error amplifier 3b. Further, the control unit 6 also turns on the third switch SW3 to short-circuit the LED block 4b for traveling light, and maintains the output voltage of the DC / DC converter unit 3 only for the LED block 4a for passing light. Applied together with the voltage of the smoothing capacitor C0.

By repeating the operations (1) and (2) during the period in which the output current is intermittently turned on and the LED block 4a for the passing light is dimmed, the rise when the output current to the LED light source 4 is energized The fall when stopping can be made steep, and the output current can be made close to an ideal rectangular wave.

As described above, according to the second embodiment, the LED lighting device 1 has the third switch SW3 that short-circuits both ends of the LED block 4b for traveling light in the LED light source 4 in which a plurality of LEDs are connected in series. Then, the control unit 6 intermittently turns on the LED block 4a for the passing lamp and turns off the LED block 4a for the passing lamp during the period when the LED block 4a for the passing lamp is turned off. The operation of the DC / DC converter unit 3 is stopped while maintaining the operating frequency and duty value of the switching element Q0 when 3 is operating, and a short circuit of the LED block 4b for traveling light by the third switch SW3 is performed. When the LED block 4a for the passing lamp is turned on and turned on, the switching element is operated with the operating frequency and duty value held by the previous extinction. 0 is operated with starting the operation of the DC / DC converter unit 3, and configured to short-circuit the LED blocks 4b of the running lamp by the third switch SW3. For this reason, the LED lighting device for DRL which carries out the dimming lighting of the LED for passing lamps of the headlamp which uses LED for a running light and a passing lamp is realizable. In addition, since an intermittent current close to an ideal rectangular wave can be supplied to the low-light LED, it is possible to realize a DRL that is dimmed with a desired brightness and a predetermined emission color.

Embodiment 3 FIG.
FIG. 9 is a circuit diagram showing a configuration of the LED lighting device 1 according to Embodiment 4 of the present invention. The same or corresponding parts as those in FIG.
In the second embodiment, the DRL is configured by dimming the LED block 4a for the passing lamp, and conversely, the DRL can be configured by dimming the LED block 4b for the traveling lamp. . Therefore, in the third embodiment, for example, as shown in FIG. 9, in addition to the third switch SW3 that short-circuits both ends of the LED block 4b for traveling light, both ends of the LED block 4a for passing light are newly connected. A fourth switch SW4 for short-circuiting is provided.

In the LED lighting device 1 having the configuration shown in FIG. 9, when the passing lamp is lit, the control unit 6 turns on the third switch SW3 and turns off the fourth switch SW4, so that the LED block 4b for the running light is turned on. Both ends are short-circuited and turned off, and only the LED block 4a for the passing lamp is turned on.
When the traveling light is lit, the control unit 6 turns off both the third switch SW3 and the fourth switch SW4 to open the short circuit, and simultaneously connects the LED block 4a for passing light and the LED block 4b for traveling light simultaneously. Light up.

When used as a DRL, when the LED block 4b for running lights is turned off, the first switch SW1 and the second switch SW2 are opened and the DC / DC converter unit 3 operates by the previous lighting. The operation of the DC / DC converter unit 3 is stopped while maintaining the operating frequency and Duty value of the switching element Q0 at the same time, and the short circuit of the LED block 4a for the passing lamp by the fourth switch SW4 is opened.
When the LED block 4b for running lights is lit, the switching element Q0 is operated with the operating frequency and duty value held by the first switch SW1 and the second switch SW2 being short-circuited and immediately before being turned off. The operation of the DC converter unit 3 is started, and the LED block 4a for the passing lamp is short-circuited by the fourth switch SW4.

As described above, the output current to the LED light source 4 side is repeated in the same manner as in the second embodiment by repeating the above operation during the period in which the output current is intermittently turned on and the LED block 4b for running lights is dimmed. Can rise sharply when it is energized and fall when it stops, making it possible to bring the output current closer to an ideal rectangular wave.
For this reason, the LED lighting device for DRL which carries out the dimming lighting of the LED for driving lights of the headlamp which uses LED for a driving light and a passing lamp is realizable. Further, since an intermittent current close to an ideal rectangular wave can be supplied to the LED for the traveling light, it is possible to realize a DRL that is dimmed with a desired brightness and a predetermined emission color.

Embodiment 4 FIG.
FIG. 10 is a circuit diagram showing the configuration of the LED lighting device 1 according to Embodiment 4 of the present invention. The same or corresponding parts as those in FIG.
In the third embodiment, the operation signal is generated by an analog circuit including the error amplifier 3b, the waveform generator 3c, the second switch SW2, and the like, and the supply and interruption of the operation signal to the switching element Q0 are performed by the first switch. Although the configuration is controlled by SW1, in the fourth embodiment, these functions are performed by the control unit 6 including the CPU 6a.

As shown in FIG. 10, the control unit 6 of the fourth embodiment is configured to include a CPU 6a and a storage unit 6b. Using the functions of the CPU 6a, the error amplifier 3b and the waveform generator 3c in the third embodiment are used. The process for generating the operation signal of the switching element Q0 performed by the first switch SW1, and the process of supplying and shutting off the operation signal to the switching element Q0 performed by the first switch SW1 (operation and stop of the DC / DC converter unit 3) A process of holding the frequency of the operation signal (operation frequency) and the duty value while the operation of the DC / DC converter unit 3 is stopped by the integrator including the integration capacitor C1 and the integration resistor R1 and the second switch SW2. I do.

The storage unit 6b is composed of an EEPROM (Electrically Erasable Programmable Read-Only Memory) and a non-volatile storage element such as a flash memory. Information such as the lighting duration is set in advance.

In the control unit 6, the input of the output voltage and the input of the output current detected by the current detection resistor R2 are performed by an A / D converter (not shown) built in the CPU 6a. Further, the CPU 6a executes a program given in advance to generate an operation signal to the switching element Q0 in which the duty value is changed according to the state of the input output current so that the output current gradually approaches the target value. And a timing control for supplying and shutting off the operation signal to the switching element Q0. Further, during the dimming lighting, the CPU 6a stores the operating frequency and duty value at the time of the previous lighting at the time of extinction in a memory (not shown), and these operating frequency and duty value from the memory for the next lighting operation. Is read and used.

Further, in the fourth embodiment, the control unit 6 and the external device 10 may be connected via the input / output I / F unit 9, and predetermined information can be input / output. For example, with respect to the LED lighting device 1 manufactured in advance, information such as the value of the output current energized to the LED light source 4 at the time of steady lighting using the external device 10, the intermittent period at the time of dimming lighting, and the lighting time width of each period, etc. Is updated to these pieces of information. Thereby, the LED lighting device 1 of the same structure can be set to the characteristic corresponding to an individual vehicle lamp.
Further, for example, when any abnormality occurs in the LED light source 4 or the LED lighting device 1, the control unit 6 stores the information in the storage unit 6 b and outputs the information to the external device 10 via the input / output I / F unit 9. .

As described above, according to the fourth embodiment, the control unit 6 includes the CPU 6a, and the CPU 6a immediately before turning off the LED light source 4 in a period in which the LED light source 4 is dimmed by intermittently outputting the output current. When the operation of the DC / DC converter unit 3 is stopped and the LED light source 4 is lit while maintaining the operating frequency and duty value of the switching element Q0 when the DC / DC converter unit 3 is in operation. The switching element Q0 is operated at the operating frequency and Duty value held at the time of the last extinction, and at least a part of the function of starting the operation of the DC / DC converter unit 3 or an equivalent function is performed. For this reason, parts such as an error amplifier and a waveform generator (comparator) can be reduced by substituting a part of the function of the DC / DC converter unit 3 with the function of the CPU 6a of the control unit 6. Therefore, the LED lighting device 1 can be miniaturized and the cost can be reduced.

Further, according to the fourth embodiment, the LED lighting device 1 sets the target value of the output current used for the dimming control of the LED light source 4, the intermittent period at the time of dimming lighting, the lighting time width of each period, and the like. Based on the input / output I / F unit 9 that inputs / outputs information between the control unit 6 and the external device 10, and new setting information that is input from the external device 10 via the input / output I / F unit 9. The storage unit 6b that can change the setting information already stored is provided. For this reason, by storing information necessary for lighting the LED light source 4 in the nonvolatile memory element, it becomes possible to easily produce LED lighting devices having different characteristics. Therefore, the number of LED lighting devices can be reduced and many of the same products can be produced, the quality is stabilized, and production management is facilitated.

In the fourth embodiment, the configuration example in which the CPU 6a performs a part of the functions of the DC / DC converter unit 3 of the LED lighting device 1 described in the third embodiment has been described. Instead, the LED lighting device 1 shown in the first and second embodiments can also be configured to cause the CPU 6a to perform some functions of the DC / DC converter unit 3 in the same manner.

In addition to the above, within the scope of the invention, the invention of the present application can be freely combined with each embodiment, modified any component of each embodiment, or omitted any component in each embodiment. Is possible.

As described above, the LED lighting device according to the present invention suppresses overcurrent while steepening the rising of the intermittent current supplied to the LED light source during dimming lighting, so that the headlamp with DRL, the tail lamp with stop lamp, etc. It is suitable for use in an LED lighting device for lighting a vehicle lamp.

1 LED lighting device, 2 DC power supply, 2a power switch, 3 DC / DC converter unit, 3a transformer, 3b error amplifier, 3c waveform generator, 4 LED light source, 5 control power supply unit, 6 control unit, 6a CPU, 6b memory Unit, 7 input I / F unit, 8 dimming instruction device, 9 input / output I / F unit, 10 external device.

Claims

A DC / DC converter unit that generates a predetermined voltage for LED lighting from a power source by turning on and off the switching element at a predetermined operating frequency and duty value, and a control unit that controls the operation of the DC / DC converter unit An LED lighting device for intermittently turning on and off the output light source by intermittently turning on and off the output current and dimming the LED light source,
In the period in which the control unit intermittently lights the LED light source by intermittently outputting the output current,
When the LED light source is turned off, the operation of the DC / DC converter unit is stopped while maintaining the operating frequency and duty value of the switching element when the DC / DC converter unit is operating immediately before lighting. ,
An LED lighting device characterized in that when the LED light source is turned on, the operation of the DC / DC converter unit is started by operating the switching element at the operating frequency and Duty value held at the time of the previous light extinction.
The control unit outputs a triangular wave having a predetermined operating frequency,
The DC / DC converter unit includes:
A transformer or a coil that receives the power source and generates a predetermined output current;
A rectifier diode that rectifies the output current of the transformer or the coil;
A smoothing capacitor that smoothes the output current of the rectifier diode and supplies it to the LED light source;
A current detector for detecting an output current supplied to the LED light source;
An error amplifier serving as an integrator that inputs an output current signal detected by the current detector and integrates a difference between the output current signal value and a target value;
A waveform generator that generates a triangular wave from the control unit into a rectangular wave having a duty value corresponding to the output value of the error amplifier, and outputs the operation signal to the switching element;
The LED lighting device according to claim 1, wherein the duty value is held by holding an output value of the error amplifier.
The DC / DC converter unit includes:
A first switch for cutting off an operation signal input from the waveform generator to the switching element;
A second switch for cutting off an output current signal input from the current detector to the error amplifier;
The controller is
The operation of the DC / DC converter unit is stopped by operating the first switch to cut off an operation signal input to the switching element,
3. The LED lighting device according to claim 2, wherein the output value of the error amplifier is held by operating the second switch to cut off an output current signal input to the error amplifier.
The DC / DC converter unit includes a second switch for cutting off an output current signal input from the current detector to the error amplifier,
The controller is
The operation of the DC / DC converter unit is stopped by stopping the output of the triangular wave,
3. The LED lighting device according to claim 2, wherein the output value of the error amplifier is held by operating the second switch to cut off an output current signal input to the error amplifier.
The LED lighting device includes a third switch that short-circuits both ends of some of the LED light sources in which a plurality of LEDs are connected in series.
In the period in which the control unit intermittently turns on the output current and dimms the LED that does not short-circuit both ends of the LED light source,
When the LED that does not short-circuit both ends is turned off, the operation of the DC / DC converter unit is maintained while maintaining the operating frequency and duty value of the switching element when the DC / DC converter unit is operating immediately before lighting. And the short circuit by the third switch is opened,
When the LED that does not short-circuit both ends is lit, the switching element is operated at the operating frequency and duty value that were held at the time of the previous extinction to start the operation of the DC / DC converter unit, and the third switch The LED lighting device according to claim 1, wherein the LED lighting device is short-circuited.
The control unit has a CPU,
In the period in which the LED light source is dimmed by interrupting the output current, the CPU
When the LED light source is turned off, the operation of the DC / DC converter unit is stopped while maintaining the operating frequency and duty value of the switching element when the DC / DC converter unit is operating immediately before lighting. ,
When the LED light source is turned on, at least a part of the function of starting the operation of the DC / DC converter unit by operating the switching element with the operating frequency and duty value held at the time of the previous light extinction or at least a part of the equivalent function is provided. The LED lighting device according to claim 1, wherein the LED lighting device bears.
Input / output unit for inputting / outputting setting information used for control of dimming the LED light source between the control unit and an external device;
The LED lighting according to claim 6, further comprising: a storage unit that can change already stored setting information based on new setting information input from the external device via the input / output unit. apparatus.