JP2013222516A - Led lighting device, and vehicular lighting system and luminaire using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an LED lighting device that shortens a rise time of an output current required for arbitrary lighting of an LED while using a Cuk circuit in a DC power circuit.SOLUTION: An LED lighting device 1 includes: a DC power circuit 5 for supplying a current to an LED 3; and a control section 6 for controlling the current supplied from the DC power circuit 5 to the LED 3. The DC power circuit 5 has the Cuk circuit with choke coils disposed in input and output lines, respectively. The control section 6 has a detection section 61 for detecting a load voltage of the LED 3 during continuous lighting of the LED 3, and performs feedback control of outputting a driving signal to drive a switch element Q1 of the Cuk circuit on the basis of the detection result of the detection section 61 and, at the start of lighting of the LED 3, gives a predetermined initial value A to the duty of the driving signal to drive the switch element Q1 of the Cuk circuit. A rise time of an output current Iout required for arbitrary lighting of the LED 3 can be shortened by a time T1 in which the duty of the driving signal would reach the initial value A from zero.

Description

  The present invention relates to an LED lighting device that drives an LED to light, a vehicle lighting device using the LED lighting device, and a lighting fixture.

  Light emitting diodes (hereinafter referred to as LEDs) are capable of emitting light with low power and high luminance, and are used as light sources for various electric devices such as displays and lighting equipment. In recent years, LEDs have been used as light sources for in-vehicle lighting devices that replace discharge lamps.

  In an in-vehicle lighting device using an LED as a light source, an LED lighting device equipped with a DC power supply circuit that converts a DC power supply voltage of a car battery (DC power supply) into a predetermined voltage suitable for LED lighting driving is used. In a general DC power supply circuit, a DC-DC converter incorporating a transformer is used. However, since a DC-DC converter incorporating this transformer requires a control unit using a high-spec microcomputer that is fast in arithmetic processing, the device becomes expensive. Therefore, in a lighting device using LEDs as a light source, a DC-DC converter using a Cuk circuit in which a choke coil is arranged in each input / output line instead of a transformer is employed (for example, see Patent Document 1).

  FIG. 11 shows a configuration in which an LED lighting device composed of a DC power supply circuit (DC-DC converter) using a general Cuk circuit is incorporated between a DC power supply DC and an LED (load). The Cuk circuit includes two choke coils (an input inductor L1 and an output inductor L2) arranged in series between a smoothing input capacitor C1 and an output capacitor C3, and a coupling capacitor C2 provided therebetween. Have. A switching element Q1 for turning on and off the current to the input inductor L1 is disposed between the input inductor L1 and the coupling capacitor C2, and a rectifying diode D1 is disposed between the coupling capacitor C2 and the output inductor L2. Has been. This DC power supply circuit has a detection resistor Rs for detecting the load of the LED on the output side of the Cuk circuit. If such a Cuk circuit is used, drive control by a microcomputer with relatively low specifications for switching the switching element Q1 is possible, and the cost of the apparatus can be reduced.

Japanese Patent Laid-Open No. 2005-224094

  However, the DC-DC converter using the Cuk circuit has a problem that the rise time necessary for obtaining an output current for arbitrarily lighting the LED is slow. Specifically, in the Cuk circuit, when the duty of the drive signal of the switch element Q1 gradually increases from 0 at the start of LED lighting, when the switch element Q1 is turned off, a current flows from the coupling capacitor C2 of the Cuk circuit to the input side. Backflow. Therefore, as shown in FIG. 12A, the current IL1 flowing through the input inductor L1 instantaneously becomes negative. When charging of the coupling capacitor C2 is completed, the current IL1 is always positive as shown in FIG.

  Therefore, at the start of LED lighting, as illustrated in FIG. 12C, the rising waveform of the output current Iout has a stepped shape, and the output current Iout continues to a continuous mode that maintains a constant value necessary for arbitrary lighting of the LED. Will slow down the transition. In addition, when the rising waveform of the output current Iout is stepped, particularly when the output current Iout that can arbitrarily turn on the LED is 100%, the output current Iout is higher than that of a DC power supply circuit using a general transformer. Time to reach 50% is delayed.

  In-vehicle lighting devices need to light a light source (LED) immediately with a desired light output in response to an ON operation of a lighting switch, as compared with a general lighting fixture. For this reason, it is difficult to apply the Cuk circuit required for obtaining the required output current with a slow rise time to the DC power circuit of the LED lighting device for the in-vehicle lighting device.

  The present invention solves the above-mentioned problems, and uses an LED lighting device that uses a Cuk circuit as a DC power supply circuit and has an early rise time required to obtain an output current for arbitrarily lighting an LED, and a vehicle using the same An object of the present invention is to provide a lighting device and a lighting fixture.

  In order to solve the above problems, the present invention is an LED lighting device comprising: a DC power supply circuit that supplies current to an LED; and a control unit that controls supply current from the DC power supply circuit to the LED, The DC power supply circuit has a Cuk circuit in which a choke coil is disposed on each of the input and output lines, and the control unit has a detection unit that detects a load voltage of the LED when the LED is continuously lit. Based on the detection result, feedback control is performed to output a drive signal for driving the switch of the Cuk circuit, and at the start of lighting of the LED, a predetermined initial value is given to the duty of the drive signal for driving the switch of the Cuk circuit. Features.

  In the LED lighting device, the control unit includes an input voltage detection unit that detects an applied voltage on the input side of the Cuk circuit, and an initial value of the duty of the drive signal is set to a detection voltage by the input voltage detection unit. It is preferable to be determined accordingly.

  In the LED lighting device, the control unit includes a storage unit that stores a load of the LED detected by the detection unit, and an initial value of the duty of the drive signal is the previous value of the LED stored in the storage unit. It is preferably determined according to the load during driving.

  The said LED lighting device WHEREIN: It is preferable that the said control part controls the change part of the output current with respect to LED per unit time uniformly.

  In the LED lighting device, it is preferable that the control unit starts the duty of the drive signal from 0 when an abnormal state is stored in the load at the previous drive of the LED in the storage unit.

  In the LED lighting device, the control unit sets an initial value of the duty of the driving signal based on an input voltage obtained by resistance division of a predetermined external voltage, and the input voltage can be changed by an external resistor. It is preferable.

  In the LED lighting device, the DC power supply circuit includes a detection circuit in which a capacitor and a detection resistor are arranged in parallel between a primary side ground line and a secondary side anode line in the Cuk circuit, It is preferable that the control unit includes an overcurrent detection unit that detects a current flowing in the overcurrent detection resistor from a voltage across the detection resistor of the detection circuit.

  The LED lighting device is preferably used for an in-vehicle lighting device.

  It is preferable that the said LED lighting device is used for a lighting fixture.

  According to the present invention, since the predetermined initial value is given to the duty of the drive signal for driving the switch of the Cuk circuit, the output current required for arbitrarily lighting the LED only for the time when the duty of the drive signal reaches from the initial value to 0 The rise time can be shortened.

The perspective view which shows schematic structure of the vehicle-mounted illuminating device using the LED lighting device which concerns on the 1st Embodiment of this invention. The circuit diagram of the LED lighting device. (A) is a figure which shows the example of control of the duty of the drive signal which controls the output current in the LED lighting device, (b) is a figure which shows another example of control. (A) is a figure which shows transition of the rising part of the output current in the LED lighting device using a Cuk circuit and the change of the output current per unit time, (b) is a modification of the LED lighting device, The figure which shows the example of control of the change of the rising current and the output current per unit time. The flowchart for demonstrating the output stop operation | movement at the time of load abnormality in the modification of the LED lighting device. The circuit diagram of the LED lighting device which concerns on the 2nd Embodiment of this invention. The figure which shows the control example of the duty of the drive signal which controls the output current in the LED lighting device. The circuit diagram of the LED lighting device which concerns on the 2nd Embodiment of this invention. The figure which shows the example of control of the change of the output current detected in the detection part of the LED lighting device, and an output stop operation | movement. (A) is a side view of the lighting fixture using the LED lighting device, (b) is a front view. The circuit diagram of the LED lighting device using a general Cuk circuit. (A) is a diagram showing a change in the current flowing through the input inductor when the drive is disclosed in an LED lighting device using a general Cuk circuit, (b) a diagram showing a change in the current flowing through the input inductor after the drive is disclosed, (C) is a figure which shows the rising waveform of the output current of the LED lighting device.

  An LED lighting device according to a first embodiment of the present invention and an in-vehicle lighting device using the LED lighting device will be described with reference to FIGS. 1 to 3. As shown in FIG. 1, the LED lighting device 1 according to the present embodiment is used for an in-vehicle lighting device 2. The in-vehicle illumination device 2 includes a lamp 4 that uses a light emitting diode (hereinafter, LED 3) as a light source, a battery (DC power supply DC) that supplies current to the LED 3, and a switch SW that turns on and off the supply current to the LED 3. . The LED lighting device 1 controls the supply current from the DC power source DC to the LED 3 according to an on / off operation in the switch SW. In the illustrated example, the LED lighting device 1 is arranged in each of the pair of left and right lamps 4 (headlights). However, one LED lighting device 1 controls the supply current of the LEDs 3 in the plurality of lamps 4. It may be configured.

  As shown in FIG. 2, the LED lighting device 1 is arranged between the DC power supply DC and the lamp 4, and supplies a DC power supply circuit 5 that supplies current to the LED 3 and a supply current Io from the DC power supply circuit 5 to the LED 3. And a control unit 6 for controlling. In the following description, the LED 3 is a generic term for a group of light emitting diode elements arranged in series. The DC power supply circuit 5 is a DC-DC converter using a Cuk circuit in which choke coils are arranged on input / output lines.

  The LED 3 is an LED that can emit illumination light of a desired light color. For example, a GaN-based blue LED chip is coated with a YAG-based yellow phosphor, and white light is emitted by mixing blue light and yellow light. LEDs are used. In addition, not only white LEDs but also a plurality of LEDs having different emission colors of red, green, and green may be used in combination as appropriate, or an OLED using an organic light emitting material for the light emitting part may be used. Good.

  The Cuk circuit of the DC power supply circuit 5 is provided between the smoothing input capacitor C1 and the output capacitor C3, and between the two inductor elements (input inductor L1 and output inductor L2) arranged directly between them. And a coupling capacitor C2. A switching element Q1 for turning on and off the current to the input inductor L1 is disposed between the input inductor L1 and the coupling capacitor C2, and a rectifying diode D1 is disposed between the coupling capacitor C2 and the output inductor L2. Has been. The DC power supply circuit 5 has a detection resistor Rs for detecting the load voltage of the LED on the output side of the Cuk circuit, and both ends of the detection resistor Rs are amplifying composed of resistors R1 to R4 and an operational amplifier OP. The circuit is connected to the comparator CP1 of the detection unit 61 of the control unit 6 through a circuit.

  The control unit 6 includes a detection unit 61 that detects the load voltage of the LED 3, and a drive signal transmission unit 62 that outputs a drive signal that drives the switch element Q <b> 1 of the Cuk circuit based on the detection result by the detection unit 61. The drive signal transmitter 62 performs feedback control by outputting the duty of the drive signal for driving the switch element Q1 of the Cuk circuit based on the detection result by the detector 61 when the LED 3 is continuously lit. The control unit 6 includes an input voltage detection unit 63 that detects an applied voltage on the input side of the Cuk circuit, and a storage unit 64 that stores the load of the LED 3 detected by the detection unit 61.

  In the present embodiment, the control unit 6 gives a predetermined initial value A to the duty of the drive signal output from the drive signal transmission unit 62 at the start of lighting of the LED 3 as shown in FIG. It is configured. Thus, by giving the initial value A to the duty (Duty) of the drive signal, the rise time of the output current Iout required for the arbitrary lighting of the LED 3 can be accelerated by the time (T1) when the duty reaches from 0 to A. it can. Further, the transition to the continuous mode in which the output current Iout maintains the duty (constant value B) of the drive signal necessary for arbitrarily lighting the LED is accelerated, and the rising waveform of the output current Iout approaches linear (see FIG. 4 (described later)). b)).

  Here, the initial value A is described above in order to suppress overshoot of the circuit in view of light amount variation based on individual differences of the LEDs 3, characteristics of the DC-DC converter, responsiveness of the microcomputer used for the drive signal transmission unit 62, and the like. A value lower than the constant value B is set.

  Further, as shown in FIG. 3B, if the slope of the duty (duty) -time waveform from the initial value A to the constant value B is reduced, the circuit overshoot can be more effectively suppressed. it can. In addition, if this inclination is small, time until it reaches the fixed value B is delayed by time T. However, if the slope is set so that the delay time T2 is shorter than T1, the rise time of the output current Iout for arbitrarily lighting the LED 3 is faster than when the initial value A is not given to the duty, and Overshoot can be effectively suppressed.

  Incidentally, the duty of the drive signal necessary for obtaining the output current Iout for arbitrarily lighting the LED 3 varies depending on the input voltage of the DC power supply circuit 5 and the load of the LED 3. For example, when the input voltage of the DC power supply circuit 5 is low and the load of the LED 3 is large, the duty value of the drive signal is high, and when the input voltage of the DC power supply circuit 5 is high and the load of the LED 3 is small, the drive is performed. The duty value of the signal is lowered. Therefore, in the present embodiment, the initial value A of the duty of the drive signal that drives the switch element Q1 of the Cuk circuit is changed as appropriate.

  Specifically, the input voltage detection unit 63 constantly monitors the applied voltage on the input side of the Cuk circuit, that is, the input voltage. The storage unit 64 stores the load of the LED 3 detected by the detection unit 61. Here, the storage unit 64 stores the load of the LED 3 only when the input voltage falls below a certain value, or periodically stores the load of the LED 3 and updates the latest state. In the latter case, when the stop of voltage supply is detected in the input voltage detection unit 63, the update of the load storage of the LED 3 is stopped. The storage unit 64 stores in advance a table (not shown) that defines an initial value of an appropriate duty for a combination of an input voltage and a load when the LED 3 is driven last time. Then, the drive signal transmission unit 62 refers to the input voltage detected by the input voltage detection unit 63 at the start of lighting of the LED 3 and the load at the time of the previous driving of the LED 3 stored in the storage unit 64, from the above table. Read the initial value A of the duty of the drive signal. As described above, at the start of lighting of the LED 3, the drive signal transmission unit 62 can read the optimum initial value A of the duty of the drive signal under various input voltage conditions and load conditions of the LED 3.

  Next, the LED lighting device which concerns on the modification of the said embodiment is demonstrated with reference to FIG. As shown in FIG. 4A, in the DC power supply circuit 5 using the Cuk circuit, the rising waveform of the output current Iout is stepped, which is necessary for arbitrary lighting of the LED 3 as compared with other DC-DC converter systems. It takes a long time to reach the output current I1. Therefore, in this modification, the detection unit 61 monitors the change di of the output current Iout per unit time dt, and as shown in FIG. 4B, the detection unit 61 per unit time with respect to time (Time). The duty (Duty) of the drive signal output from the drive signal transmission unit 62 is controlled so that the change (di / dt) of the output current Iout of the drive signal becomes constant.

  As a method of making the di / dt constant, first, the control unit 6 causes the storage unit 64 to store a table in which di / dt is associated with the duty of the drive signal. Then, the drive signal transmission unit 62 refers to the above table and performs control to increase the duty increment of the drive signal when the value of di / dt is lower than a predetermined value (di1 / dt1). On the other hand, when the value of di / dt is higher than a predetermined value (di1 / dt1), the drive signal transmission unit 62 performs control to decrease the duty increment. The constant control of di / dt is performed until immediately before the output current Iout reaches the output current I1 necessary for arbitrary lighting of the LED 3 in order to suppress overshoot of the circuit, and when the output current Iout reaches the output current I1, The control unit 6 performs only normal feedback control. According to this modified example, the control unit 6 can perform the above-described control, whereby the rising waveform of the output current Iout can be brought close to linear.

  Next, an LED lighting device according to another modification of the embodiment will be described with reference to FIG. As described in the above embodiment, when the initial value A is set to the duty of the drive signal output from the drive signal transmission unit 62, the control unit 6 detects an abnormality such as an open or short of the LED 3 (load). When the LED is driven again after being stopped, overvoltage and overcurrent are generated in the LED 3. Therefore, in this modification, the load state at the time of lighting of the LED 3 is stored in the storage unit 64, and when the abnormal state at the previous driving of the LED 3 is stored at the start of lighting of the LED 3, the drive signal The initial value A of the duty is reset to zero.

  In general, in an LED lighting device used for an in-vehicle lighting device, when the LED 3 is short-circuited or opened, the control unit 6 detects an abnormality in the load state of the LED 3 and a drive signal to the DC power supply circuit 5. The transmission is stopped, and the circuit is stopped or maintained until the input voltage is reapplied, or repeatedly operated at regular intervals. However, if the initial value A is given to the duty of the drive signal at the time of restart when the LED 3 is short-circuited, conduction from the DC power supply DC to the ground GND causes excessive current to flow into the DC power supply circuit 5. The circuit may flow and be damaged.

  Therefore, as shown in the flowchart of FIG. 5, the storage unit 64 stores the load state at the time of the previous driving of the LED 3, and the drive signal transmitting unit 62 is normal when the load state at the previous driving is normal at the start of lighting of the LED 3. For example, the initial value A is set to the duty of the drive signal. On the other hand, if there is an abnormality in the load state during the previous drive, the initial value is set to 0 for the duty of the drive signal. When the previous load state is not stored in the storage unit 64, the initial value is set to 0 at the start of lighting of the LED 3 for safety. Further, if it is detected that the load state of the LED 3 is normal after the lighting of the LED 3 is started, the control unit 6 sets the initial value A to the duty of the drive signal. Then, when it is detected again that the load state of the LED 3 is normal, the output current Iout outputs the duty of the drive signal (constant value B) necessary for arbitrarily lighting the LED 3. On the other hand, when an abnormality is detected in the load state of the LED 3, the output of the drive signal is completely stopped.

  According to this modification, the control unit 6 performs the above-described control, so that if the load state during the previous drive is normal, the output current lout rises quickly, and overcurrent and overvoltage are suppressed to a minimum when abnormal. be able to.

  Next, an LED lighting device according to a second embodiment of the present invention will be described with reference to FIGS. As shown in FIG. 6, in the LED lighting device 1 of the present embodiment, the drive signal transmission unit 62 of the control unit 6 is driven based on an input voltage (command value) obtained by resistance division of a predetermined external voltage Vcc. The initial value A of the signal duty is set. The controller 6 is provided with a resistor R5 to which an external voltage Vcc is applied, and the input voltage (command value) can be changed by an external resistor Rd. The external resistor Rd is preferably a variable resistor, and the resistance value can be arbitrarily set.

  The rise time up to the set value of the output current Iout required for arbitrarily lighting the LED 3 becomes slower as the load on the LED 3 becomes heavier. Therefore, it is necessary to set the initial value A larger for the heavy-load LED 3 whose rise is slow. Therefore, in this embodiment, as shown in FIG. 7, the duty (Duty) of the drive signal necessary for arbitrarily lighting the two types of LEDs 3 to be controlled by the LED lighting device 1 is B1, B2 (B2> B1), respectively. ), The initial value of the duty of the drive signal is set to A1, A2 (A2> A1), respectively. And the input voltage (command value) at the time of making the drive signal transmission part 62 output each of initial value A1, A2 is switched by changing the resistance value of external resistance Rd.

  According to the present embodiment, since the initial value of the duty of the drive signal is set by the resistance value of the external resistor Rd, the resistance value of the external resistor Rd is changed according to the load on the LED 3. An appropriate initial value can be easily set.

  Next, an LED lighting device according to a third embodiment of the present invention will be described with reference to FIGS. As shown in FIG. 8, the LED lighting device 1 according to the present embodiment includes a capacitor C4 and a detection resistor Rs2 between the primary ground line and the secondary anode line in the Cuk circuit of the DC power supply circuit 5. A detection circuit 51 arranged in parallel is arranged. Further, the control unit 6 includes an overcurrent detection unit that detects a current flowing through the detection resistor Rs2 from the voltage across the detection resistor Rs2. The overcurrent detection unit includes a comparator CP2 connected to the detection resistor Rs2. Other configurations are the same as those in the first embodiment. In the following description, the detection unit 61 described in the first embodiment is referred to as a first detection unit 61a, and the overcurrent detection unit used in the present embodiment is referred to as a second detection unit 61b. In FIG. 8, the detection resistor Rs described in the first embodiment is represented as a detection resistor Rs1 for distinction.

  The first detection unit 61a detects a voltage value applied to the detection resistor Rs1 arranged in the output line in order to feedback control the output current Iout, and a predetermined first overcurrent threshold set by the comparator CP1. Compare with When the detected voltage value is higher than the first overcurrent threshold, the output of the drive signal in the drive signal transmission unit 62 is completely stopped to suppress the overcurrent. At this time, the detection resistor Rs1 installed in the output line is set to have a very low resistance value in order to suppress circuit loss. Accordingly, since the voltage value applied to the detection resistor Rs1 is very small, signal amplification by the operational amplifier OP is necessary for the control unit 6 to perform feedback control.

  By the way, if the LED 3 is short-circuited while the LED lighting device 1 is stopped, and the LED lighting device 1 is subsequently driven, if the initial value A is given to the duty of the drive signal, the circuit is excessive. There is a risk of current flowing. However, the first detection unit 61a is connected to the DC power supply circuit 5 through an amplifier circuit using an operational amplifier OP, and signal transmission to the control unit 6 is slow due to these complicated circuits. For this reason, the first detector 61a can cope with a gradual current rise, but cannot cope with a steep current rise, delaying the output stop of the drive signal, and possibly preventing the circuit from being protected from an overcurrent. .

  On the other hand, the second detection unit 61b detects the voltage value applied to the detection resistor Rs2 and compares it with a predetermined second overcurrent threshold set by the comparator CP2. When the detected voltage value is higher than the second overcurrent threshold, the output of the drive signal in the drive signal transmission unit 62 is completely stopped to suppress the overcurrent. Since the second detection unit 61b has fewer electronic components that cause a signal transmission delay such as signal amplification by the operational amplifier OP than the first detection unit 61a, it can cope with a steep current rise. If the load state of the DC power supply circuit 5 and the LED 3 is normal, if the resistance value of the detection resistor Rs2 is large to some extent, the capacitor C4 arranged in parallel becomes the main current path, so that the circuit loss is small.

  In FIG. 9, the detection waveform of the output current Iout in the first detector 61a is indicated by a broken line, and the detection waveform of the output current Iout in the second detector 61b is indicated by a solid line. That is, the first detection unit 61a is slightly delayed in detection time compared to the second detection unit 61b.

  In the present embodiment, the first detector 61a and the second detector 61b are used in combination, and the second overcurrent threshold (solid line) is set to be larger than the first overcurrent threshold (broken line). In this way, when a severe overcurrent occurs even once in a short time, the second detection unit 61b operates to stop the output of the drive signal. When a slight overcurrent occurs, the first detector 61a operates to attenuate the duty of the drive signal and maintain the lighting operation as much as possible. When a slight overcurrent occurs a plurality of times, the first detector 61a operates to stop the output of the drive signal, and the circuit can be protected from the overcurrent.

  The LED lighting device 1 according to the embodiment described above can be applied not only to an in-vehicle lighting device but also to a lighting fixture using an LED as a light source. Here, as shown in FIGS. 10A and 10C, a downlight type lighting fixture 7 embedded in a ceiling or the like is taken as an example. The lighting fixture 7 includes a light source unit 71 in which a plurality of diode elements D1 and D2 (generally referred to as LED3) are mounted on a circuit board, and a main body unit 72 that houses the LED lighting device 1 that lights the LED3 of the light source unit 71. . In addition, the lighting fixture 7 is a terminal block to which a frame body portion 73 that is fitted in an opening formed in a ceiling or the like and holds the light source portion 71 and the like, and a power supply line for receiving power supply from a commercial power supply AC are connected. 74 and an attachment spring 75 for fixing the frame body portion 73 to the ceiling or the like. In addition, when used for such a lighting fixture 7, it replaces with or adds to the direct-current power supply DC and DC-DC converter 51 which were mentioned above, and the AC-DC converter which converts the alternating current supplied from commercial power supply AC into a direct current (Not shown) is mounted.

  The present invention is not limited to the above embodiment, and various modifications can be made. For example, the control unit 6 may include a timer for measuring the elapsed time from the previous driving of the LED 3 at the start of lighting of the LED, and the elapsed time may be used as a factor for determining the initial value A of the duty of the drive signal. . In this case, for example, as the elapsed time becomes longer, there is a higher possibility that an abnormality will occur in the load state of the LED 3 during the non-driving time, so the initial value A of the duty of the driving signal is set low.

DESCRIPTION OF SYMBOLS 1 LED lighting device 2 In-vehicle lighting device 3 Light emitting diode (LED)
5 DC power circuit (Cuk circuit)
51 Detection Circuit 6 Control Unit 61 Detection Unit 61b Second Detection Unit (Overcurrent Detection Unit)
62 Input voltage detection unit 64 Storage unit 7 Lighting fixture A Initial value of duty of drive signal C4 Capacitor of detection circuit L1 Input inductor (choke coil)
L2 output inductor (choke coil)
Q1 Switch element Rs2 Detection resistance Rd External resistance Vcc External voltage

Claims (9)

An LED lighting device comprising: a DC power supply circuit that supplies current to the LED; and a control unit that controls supply current from the DC power supply circuit to the LED,
The DC power supply circuit has a Cuk circuit in which choke coils are arranged on input / output lines,
The control unit includes a detection unit that detects a load voltage of the LED during continuous lighting of the LED, and performs feedback control that outputs a drive signal that drives the switch element of the Cuk circuit based on a detection result by the detection unit. When the lighting of the LED is started, a predetermined initial value is given to the duty of the drive signal for driving the switch element of the Cuk circuit. The control unit includes an input voltage detection unit that detects an applied voltage on the input side of the Cuk circuit,
2. The LED lighting device according to claim 1, wherein an initial value of the duty of the drive signal is determined according to a voltage detected by the input voltage detector. The control unit includes a storage unit that stores a load of the LED detected by the detection unit,
3. The LED lighting device according to claim 1, wherein an initial value of the duty of the drive signal is determined according to a load at the time of previous driving of the LED stored in the storage unit.   The LED lighting device according to claim 3, wherein the control unit controls a change in output current to the LED per unit time to be constant.   The said control part starts the duty of the said drive signal from 0, when the abnormal state is memorize | stored in the load at the time of the last drive of LED in the said memory | storage part, The Claim 3 or Claim 4 characterized by the above-mentioned. LED lighting device.   The control unit sets an initial value of the duty of the drive signal based on an input voltage obtained by resistance division of a predetermined external voltage, and the input voltage can be changed by an external resistor. The LED lighting device according to any one of claims 1 to 5. The DC power supply circuit has a detection circuit in which a capacitor and a detection resistor are arranged in parallel between a primary side ground line and a secondary side anode line in the Cuk circuit,
7. The overcurrent detection unit according to claim 1, wherein the control unit includes an overcurrent detection unit that detects a current flowing through the overcurrent detection resistor from a voltage across the detection resistor of the detection circuit. LED lighting device as described in the paragraph.   The vehicle-mounted illuminating device using the LED lighting device as described in any one of Claims 1 thru | or 7.   The lighting fixture using the LED lighting device as described in any one of Claim 1 thru | or 7.

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