JP2011060615A - Led lighting device and lighting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an LED lighting device which controls dimming by an inverter, maintains an LED current at a target current value by feedback control, and reduces the LED current without increasing a drive frequency of the inverter so high. <P>SOLUTION: The LED lighting device 110-1 includes a resonance capacitor 9 serially connected to a second inductor 8. In the LED lighting device 110-1, a feedback control part 105 detects a corresponding signal corresponding to an LED current flowing in the LED 13, inputs a signal to be compared for comparing with the corresponding signal from a dimming controller 19, generates a comparison result by comparing the corresponding signal with the compared signal, and outputs the generated comparison result to a voltage control oscillator 20. The voltage control oscillator 20 outputs a frequency control signal depending on the input comparison result to a driver 21. The driver 21 drives the inverter circuit 102 in accordance with the frequency control signal. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an LED lighting device and an illumination device having the LED lighting device.

  When an LED (Light Emitting Diode) is turned on, if a voltage source is directly connected, an excessive current may flow due to the voltage-current characteristics of the LED, causing the LED to break down. Therefore, in order to limit the current flowing through the LED, it is common to connect a current limiting element such as a resistor or a transistor in series with the LED to limit the current. However, in such a system, the power loss in the resistor and the transistor is large, the efficiency is reduced, and the heat generation from the resistor and the transistor becomes a problem, and the LED lighting apparatus using the high power LED or the high brightness LED which is becoming mainstream in recent years Use is unsuitable. Therefore, there is an ideal method of limiting the current using an inductor that does not cause power loss. For example, this is a method of turning on an LED using an inverter circuit (for example, Patent Document 1). This limits the current by utilizing the fact that the inductor L has an inductive reactance of 2πfL in proportion to the frequency f. According to this method, a dimming function that adjusts the brightness of the LED by adjusting the inverter frequency is also possible.

JP 2004-111104 A

  According to the technique described in Patent Document 1, when dimming, for example, when the brightness is reduced, the drive current of the inverter is increased to increase the impedance of the inductor to reduce the LED current. When dimming is performed simply by changing the inverter frequency as in this method, it is difficult to perform dimming control accurately due to LED life, manufacturing variations, component variations of LED lighting devices, etc. This causes a problem that the brightness varies. In addition, when dimming only with an inductor, the change range of the inverter frequency becomes too wide, and in order to reduce the brightness, it must be increased to a very high frequency. For this reason, the increase of the switching loss and the switching noise accompanying the increase in the inverter frequency increases.

  Further, Patent Document 1 proposes a system in which LEDs are connected in antiparallel to flow current in both directions, or a system in which a diode bridge circuit is provided at the inverter output to supply current in only one direction. However, in such a circuit system, the LED current waveform becomes a pulsating waveform synchronized with the inverter frequency, so that the peak value of the current becomes high, which may exceed the maximum absolute rating of the LED, and shorten the life of the LED. Invite.

  The present invention has been made to solve the above-described problems, and performs feedback control of the LED current, supplies an appropriate current to the LED in an LED lighting system using an inverter, and varies in brightness. An object of the present invention is to provide an LED lighting device that enables accurate dimming control with reduced brightness.

The LED lighting device of the present invention is
A DC power supply circuit that converts AC voltage to DC voltage;
An inverter circuit for converting the DC voltage converted by the DC power supply circuit into a high-frequency voltage;
A DC cut capacitor connected to the output side of the inverter circuit to cut a DC component;
An inductor connected in series with the DC cut capacitor;
A resonant capacitor for resonance connected in series with the inductor;
A full-wave rectifier circuit that is connected in parallel with the resonant capacitor, converts an output current from the inverter circuit into a direct current, and supplies the converted direct current to an LED (Light Emitting Diode) from an output terminal;
The corresponding signal and the comparison target signal are input from the comparison target signal output device that detects the corresponding signal corresponding to the LED current flowing through the LED and outputs the comparison target signal to be compared with the corresponding signal. And a feedback control unit for controlling the drive frequency of the inverter circuit according to the generated comparison result.

  According to the LED lighting device of the present invention, since the corresponding signal corresponding to the LED current is detected and the inverter circuit is feedback-controlled, the LED current can be maintained at the target current value. Further, since the LED lighting device of the present invention includes the resonance capacitor, the LED current can be reduced without increasing the drive frequency of the inverter circuit so much.

FIG. 3 is a circuit diagram of LED lighting device 110-1 in the first embodiment. The operation | movement flow of the LED lighting apparatus 110-1 in Embodiment 1. FIG. FIG. 3 shows frequency-LED current characteristics in the first embodiment. 5 is a flow of feedback control of LED lighting device 110-1 in the first embodiment. FIG. 2 is a circuit diagram of LED lighting device 110-2 in the first embodiment. The circuit diagram of the LED lighting device 120-1 in Embodiment 2. FIG. FIG. 6 is a circuit diagram of an LED lighting device 120-2 in the second embodiment. The circuit diagram of the LED lighting device 120-3 in Embodiment 2. FIG. FIG. 5 shows a method for detecting a current flowing through a switching element in a second embodiment. FIG. 6 is a circuit diagram of an LED lighting device 130 according to Embodiment 3. FIG. 10 shows no-load resonance characteristics in the third embodiment. FIG. 11 is a diagram illustrating switch switching timing in the third embodiment. 10 is a flow showing fade-in lighting in the third embodiment. 10 is a flow showing fade-out extinguishing in the third embodiment. Sectional drawing of the illuminating device 500 in Embodiment 5. FIG.

Embodiment 1 FIG.
FIG. 1 is a circuit diagram of an LED (Light Emitting Diode) lighting device 110-1 according to the first embodiment. In FIG. 1, the commercial AC power supply 1, the dimming controller 19 (comparison target signal output device), and the LED unit 106 including a plurality of LEDs 13 connected in series are not constituent elements of the LED lighting device 110-1.

  The LED lighting device 110-1 is a device that turns on the LED 13 by receiving power from the commercial AC power supply 1. The LED lighting device 110-1 includes a first rectifier circuit 2, a first inductor 3, a switching element 4, a diode 5, a first smoothing capacitor 6, switching elements 7a and 7b, a second inductor 8, a resonant capacitor 9, and a second rectifier. Circuit 10 (full wave rectification circuit), DC cut capacitor 11, second smoothing capacitor 12, LED unit 106, LED current detection resistor 14 (first resistor), LED current detection circuit 15 (corresponding signal detection unit), error amplifier 17 (comparator), a voltage controlled oscillator 20 (also referred to as a VCO), and a switching element drive circuit 21 (also referred to as a driver). The target signal 18 (comparison target signal) is input from the dimming controller 19 to the error amplifier 17.

(DC power supply circuit 103)
The first rectifier circuit 2 performs full-wave rectification on the AC voltage supplied from the commercial AC power supply 1. The first inductor 3, the switching element 4, the diode 5, and the first smoothing capacitor 6 constitute a boost chopper circuit 101. The step-up chopper circuit 101 steps up and smoothes the direct-current voltage that has been full-wave rectified by the first rectifier circuit 2. Note that. As long as the circuit configuration generates a DC voltage, a circuit configuration other than the step-up chopper circuit may be used. For example, a capacitor input type rectifier circuit may be used. As shown in FIG. 1, the first rectifier circuit 2 and the step-up chopper circuit 101 constitute a DC power supply circuit 103.

(Inverter circuit 102)
The switching element 7 a (first switching element) and the switching element 7 b (second switching element) constitute a half-bridge inverter circuit 102. The inverter circuit 102 is connected in parallel to the first smoothing capacitor 6 and converts the DC voltage converted from the AC voltage by the DC power supply circuit 103 into a high frequency voltage. A DC cut capacitor 11 is connected to the output side of the inverter circuit 102. The DC cut capacitor 11 serves to cut the DC component and output only the AC component. In addition, the 1st rectifier circuit 2 and the 2nd rectifier circuit 10 comprise a diode bridge circuit, for example.

(Feedback control unit 105)
The LED current detection circuit 15 detects the LED current flowing through the LED 13 via the LED current detection resistor 14 (first resistor) as a voltage signal (an example of a corresponding signal), and inputs it to the error amplifier 17 (comparison unit). The error amplifier 17 (comparison unit) compares the detection signal with the target signal 18 (always output from the dimming controller 19), amplifies and outputs the difference, and inputs it to the voltage controlled oscillator 20 (VCO). The voltage controlled oscillator 20 outputs a frequency signal (control signal) for driving the inverter circuit 102 to the switching element drive circuit 21 based on the voltage signal output from the error amplifier 17. As shown in FIG. 1, the LED current detection circuit 15, the error amplifier 17, and the voltage controlled oscillator 20 constitute a feedback control unit 105. The switching element drive circuit 21 (driver) drives the inverter circuit 102 (switching elements 7a and 7b) based on the frequency signal output from the voltage controlled oscillator 20.

  The configuration of the LED lighting device 110-1 according to the first embodiment has been described above. Next, the operation of the LED lighting device 110-1 according to the first embodiment will be described.

  FIG. 2 is a flowchart of the overall operation of the LED lighting device 110-1. When the commercial AC power source 1 is turned on to the LED lighting device 110-1 (S01), the first rectifier circuit 2 rectifies the AC voltage supplied from the commercial AC power source 1 (S02), and the obtained DC voltage is The voltage is boosted and smoothed by the boost chopper circuit 101 including the 1 inductor 3, the switching element 4, the diode 5, and the first smoothing capacitor 6 (S03). The DC power source smoothed by the first smoothing capacitor 6 is converted into a high-frequency voltage when the switching elements 7a and 7b of the inverter circuit 102 are alternately turned on and off (S04).

  When converted to a high frequency voltage by the inverter circuit 102, the high frequency voltage is converted again to a DC voltage by the second rectifier circuit 10 via the second inductor 8 and the resonant capacitor 9, and a DC current is supplied to the LED 13 (S05). ). Here, since the second smoothing capacitor 12 is provided at the output terminal of the second rectifier circuit 10, the ripple current due to the high frequency output from the inverter circuit 102 can be reduced, and the peak value of the current flowing through the LED 13 can be reduced. It is possible to suppress the peak value of the LED current from exceeding the maximum absolute rated current.

(Dimming control operation)
Next, dimming control will be described. In order to reduce the brightness by reducing the current flowing through the LED 13, it is achieved by increasing the drive frequency of the inverter circuit 102, that is, the switching frequency of the switching elements 7a and 7b. This is because the inductive reactance XL (XL = 2πfL [Ω]) of the second inductor 8 increases in proportion to the inverter drive frequency. Here, f is the inverter frequency, and L is the inductance of the second inductor 8.

(Suppression of frequency rise by resonant capacitor 9)
Further, in the case of only the second inductor 8, when the current flowing through the LED 13 is reduced, the inverter drive frequency must be raised very high, and the switching loss and switching noise accompanying the increase in the inverter frequency increase. Therefore, a resonant capacitor 9 is provided in parallel with the input side of the second rectifier circuit. That is, a resonance capacitor 9 for resonance is connected in series with the second inductor 8. The resonant capacitor 9 reduces the capacitance reactance XC (XC = 1 / (2πfC) [Ω]) of the capacitor in inverse proportion to the increase of the inverter driving frequency, so that the voltage applied to the LED 13 is reduced and the LED current is reduced. Can be reduced. Here, f is the inverter drive frequency, and C is the capacitance of the resonant capacitor 9.

  FIG. 3 shows an example of the comparison of the LED current value as the frequency increases when only the second inductor 8 is used and when the resonant capacitor 9 is provided in parallel on the input side of the second rectifier circuit. The characteristic 41 is a case where the resonance capacitor 9 is provided, and the characteristic 42 is a case where only the second inductor 8 is provided. In FIG. 3, the second inductor 8 is 1.5 mH and the resonant capacitor 9 is 0.01 uF. Thus, by providing the resonant capacitor 9 in parallel on the input side of the second rectifier circuit 10, it is possible to reduce the LED current while suppressing an increase in the inverter frequency during dimming.

(LED current feedback control)
FIG. 4 is a flowchart of feedback control of LED current. Next, feedback control of LED current will be described with reference to FIG. The current flowing through the LED 13 is converted into a voltage signal by the LED current detection resistor 14 and the LED current detection circuit 15 and input to the error amplifier 17 (S101). The target signal 18 of the target LED current value set by the dimming controller 19 is also input to the error amplifier 17 (S102) and compared with the detection signal of the LED current detection circuit 15. The error amplifier 17 outputs the difference between the two voltage signal values as an integral value (S103). The output signal is input to the voltage controlled oscillator 20. The voltage controlled oscillator 20 outputs a frequency signal according to the input voltage value, determines the drive frequency of the inverter circuit 102 according to the output voltage of the error amplifier 17, and determines the detected current value and the target LED current value. Feedback control is performed by controlling the inverter drive frequency so that the difference becomes smaller (S104). Here, since the LED current detection circuit 15 is provided on the output side of the second rectifier circuit 10, the error amplifier 17 and the reference potential are different. Therefore, as shown in FIG. 5, in the LED lighting device 110-2, a photocoupler 16 is provided inside the LED current detection circuit 15, and signal transmission from the LED current detection circuit 15 to the error amplifier 17 is performed by the photocoupler 16. Is going through.

  By detecting the LED current by the above method and performing feedback control, the LED current can be maintained at the target current value, and there are variations in the LED life, characteristics due to manufacturing variations, component variations in the LED lighting circuit, and the like. However, it becomes possible to supply a substantially constant current to the LEDs, so that variations in brightness among devices can be suppressed, and accurate dimming control of the LEDs can be achieved. In addition, since the LED current is smoothed by the second smoothing capacitor 12, the ripple current of the LED can be reduced even in the inverter lighting method, and it can be suppressed from exceeding the maximum absolute rated current. Because of the LED current, accurate LED current detection is possible with a simple LED current detection circuit. Note that the LED current may be detected from an alternating current on the input side of the second rectifier circuit 10, and may be detected using a current tunnel, a detection resistor, or the like (not shown).

  Furthermore, by providing the resonant capacitor 9 on the input side of the second rectifier circuit 10, it is possible to suppress an increase in inverter drive frequency during dimming, and to suppress an increase in switching loss and switching noise accompanying an increase in inverter drive frequency. it can.

Embodiment 2. FIG.
FIG. 6 is a circuit diagram of the LED lighting device 120-1 of the second embodiment. The description of the same components as those of the LED lighting device of Embodiment 1 is omitted. The difference from the first embodiment is that the LED lighting device 120-1 does not have the LED current detection circuit 15 on the output side of the second rectifier circuit 10, but has the inverter current detection resistor 22 (second resistor). is there.

  Next, although operation | movement of the LED lighting device 120-1 which concerns on this Embodiment 2 is demonstrated, description is abbreviate | omitted about the operation part similar to Embodiment 1, and dimming control is demonstrated. Here, the LED current is not directly detected, but the inverter current detection resistor 22 detects a voltage (an example of a corresponding signal) corresponding to a current flowing through the switching element 7b of the inverter circuit 102 (hereinafter referred to as an inverter current). If the product of the average value of the inverter current and the voltage inputted to the inverter circuit 102, here the product of the voltage of the first smoothing capacitor 6, the power consumed on the load side, that is, the power consumed by the LED is calculated. it can. If the voltage of the first smoothing capacitor 6 is constant, the power consumed on the load side of the inverter circuit 102 can be detected equivalently only by detecting the inverter current. Furthermore, the forward voltage of the LED can be regarded as almost constant regardless of the LED current from the electrical characteristics of the LED, so that the LED current can be detected indirectly from the inverter current detection resistor 22.

  Therefore, in the second embodiment, when dimming the LED, the inverter current detection resistor 22 detects a voltage corresponding to the inverter current, and the detected signal (corresponding signal) is input to the error amplifier 17 to be dimmed. It is compared with the target signal 18 (comparison target signal) of the inverter current output from the controller 19. The subsequent steps are the same as in the first embodiment. That is, the error amplifier 17 amplifies the difference between the inverter current detection value and the target value, and the amplified signal is input to the voltage controlled oscillator 20. The voltage controlled oscillator 20 converts the input voltage signal into a corresponding frequency signal and outputs it. The voltage controlled oscillator 20 outputs a frequency signal corresponding to the output voltage of the error amplifier 17, and the difference between the detected current value and the target inverter current value. Feedback control is performed by adjusting the inverter drive frequency in the direction of decreasing.

  As described above, as shown in FIG. 6, the inverter circuit 102 is configured by connecting the first switching element 7 a and the second switching element 7 b in series, and the first switching element 7 a is on the positive electrode side of the DC power supply circuit 103. The second switching element 7b is connected to the negative electrode side of the DC power supply circuit 103 via the second inverter current detection resistor 22 through which the current flowing through the second switching element 7b passes. The feedback control unit 105 detects a voltage corresponding to the current flowing through the second switching element 7b from the second inverter current detection resistor 22 as a corresponding signal. With the configuration as described above, the LED current can be indirectly detected from the inverter current detection value, and the reference potential of the inverter current detection signal is the same as that of the error amplifier 17, so that the detection signal is directly input to the error amplifier 17. Thus, the photocoupler 16 described in the first embodiment is not necessary. Therefore, the control circuit can be simplified and downsized.

  FIG. 7 is a diagram showing a configuration of the LED lighting device 120-2 that does not use the second rectifier circuit 10 shown in FIG. The LED lighting device 120-2 is a first series LED unit 107 composed of a series connection of a plurality of LEDs and a second series LED unit composed of a series connection of a plurality of LEDs, and is opposite to the first series LED unit 107. An LED module 109 including a second LED unit 108 connected in parallel is connected in parallel with the resonant capacitor 9. When the LEDs are connected in antiparallel and lit, the half wave current of the AC output current of the inverter circuit 102 is directly supplied to the LED. According to the LED lighting device 120-2 of the second embodiment, Since the current of the switching element 7b is detected, current detection and feedback control can be easily performed regardless of the LED connection method. In FIG. 7, a diode portion 23 composed of two diodes is a reverse voltage protection diode for the LED. In the LED connection method shown in FIG. 7, it goes without saying that feedback control is possible even if a current flowing directly through the LED is detected using a current tunnel, a detection resistor, or the like.

FIG. 8 is a diagram illustrating a configuration of an LED lighting device 120-3 that detects a current flowing directly through the LED in the antiparallel LED connection method illustrated in FIG.
As illustrated in FIG. 8, the LED lighting device 120-3 has a configuration in which a current transformer 36 is disposed instead of the LED current detection resistor 14. That is, the feedback control unit 105 detects a voltage (an example of a corresponding signal) that the LED current flowing through the LED units 107 and 108 generates in the secondary winding of the current transformer 36 and uses it for feedback control.

  FIG. 9 is a diagram illustrating two methods for detecting the current flowing through the switching element 7a or the switching element 7b of the inverter circuit 102. FIG. 9A shows the method shown in FIGS. The method of FIG. 9A is a method of detecting a current flowing through the switching element 7b (second switching element). The method shown in FIG. 9B is not limited to this method. The method shown in FIG. 9B is a method for detecting a current flowing through the switching element 7a (first switching element). As described above, the feedback control unit 105 detects the voltage corresponding to the current flowing through either the switching element 7a or the switching element 7b from the inverter current detection resistor 22 by the method shown in FIG. 9A or 9B. Then, feedback control can be performed based on the detection result.

  According to the LED lighting device of the second embodiment, it is possible to supply a substantially constant current to the LED even if there is a variation in the life of the LED, characteristic variation due to manufacturing variation, component variation in the LED lighting circuit, and the like. It is possible to suppress variations in brightness between the two, and achieve accurate LED light control.

Embodiment 3 FIG.
FIG. 10 is a circuit diagram of the LED lighting device 130 according to the third embodiment. The difference from the LED lighting device of the first embodiment is that switch means 24 and 25 realized by a resistor 26, a capacitor 27, a resistor 28, and a transistor, for example, are provided. Here, the circuit operation at the start of lighting and at the time of turning off will be described. In addition, the description of the same parts as in the first embodiment, such as the circuit configuration, is omitted.

  When the LED unit 106 is in the off state, if the signal for turning on the LED 13 (lighting instruction signal) is output by turning on the commercial AC power source 1 or the dimming controller 19 or the like, the LED 13 is instantly rated (all light). When lit at a state or target current value, a person will instantly feel dazzling and feel uncomfortable. Therefore, there is a need for a so-called fade-in lighting method in which lighting is performed from the dimming state with reduced brightness or the lower limit LED current value at the beginning of lighting when the power is turned on, and lighted brightly with time.

  Therefore, in the third embodiment, when the commercial AC power supply 1 is turned on or a signal instructing lighting is output by the dimming controller 19 or the like, the inverter driving frequency is driven at a sufficiently high frequency that the LED 13 does not light up, and then The inverter drive frequency is lowered with time and the operation is performed with the target current value.

  The state in which the inverter drive frequency is sufficiently high means that the inverter circuit 102 is in a region sufficiently deviated from the resonance frequency fo of the series resonance circuit including the second inductor 8 and the resonance capacitor 9, that is, the frequency at point a of the resonance curve shown in FIG. Is to drive. In this state, a voltage sufficient to light the LED is not generated in the resonance capacitor 9, and thus the LED 13 connected in parallel with the resonance capacitor 9 via the second rectifier circuit 10 is not lit.

  When the frequency is gradually lowered from this state (in the direction of the arrow in FIG. 11), the direction approaches the resonance point fo, the voltage of the resonance capacitor increases, and the light is lit in a dimmed state at a predetermined frequency. Thereafter, the inverter drive frequency is lowered until the LED current reaches the target level set by the dimming controller 19, and when it reaches the target signal level, the lighting is maintained in that state thereafter.

  In this way, the inverter driving frequency is controlled to be gradually lowered from a high frequency that deviates from the resonant frequency of the series resonant circuit composed of the second inductor 8 and the resonant capacitor 9, thereby instantaneously lighting at the target setting level. The glare can be suppressed.

  Next, with reference to FIG. 12 to FIG. 14, operations for fading in and fading out will be described. FIG. 12 is a diagram illustrating switch switching timing. FIG. 13 and FIG. 14 are operational flows for fading in and fading out. When the lighting instruction signal when the commercial AC power source 1 is turned on or the lighting instruction signal is output from the dimming controller 19 (T = a) (S201), the switch means 24 and the switch means 25 are turned off (S202). That is, the switch means 24 and the switch means 25 are configured to be turned off when a lighting instruction signal is output. As a result, the voltage based on the target signal 18 is charged to the capacitor 27 via the resistor 28 and the resistor 26. Here, by setting the value of the resistor 26 to a sufficiently large value, the charging time for the capacitor 27 becomes longer, and the voltage of the capacitor 27 gradually increases (S203).

  Therefore, the signal of the target LED current value input to the error amplifier 17 is gradually increased as the capacitor 27 is charged, so that it fades in and becomes brighter. Since the voltage of the capacitor 27 is zero immediately after the power is turned on, the target LED current is also zero, and the inverter circuit 102 is driven at a sufficiently high frequency at which the LED does not light up. Further, the time for the voltage of the capacitor 27 to reach the voltage level of the target signal 18 after the power is turned on is determined by the combined resistance value R of the resistors 28 and 26 and the capacitance C of the capacitor 27, and is approximately 5 × C × R [seconds]. ]. After the voltage of the capacitor 27 reaches the target signal level (T = b), the switch unit 24 is turned on (S204) (configured to be turned on). This is to improve the response speed when the target signal 18 changes.

  As described above, fade-in lighting is performed by gradually increasing the target current value of the LED input to the error amplifier 17 when the power is turned on or when a signal instructing lighting is output from the dimming controller 19. I do. Thereby, glare by lighting at the target LED current value instantaneously at the beginning of lighting can be reduced.

  Also, according to the same principle, when the LED is turned on at the brightness of the target setting level, if the signal to turn off the LED is output from the dimming controller, the inverter drive frequency is increased with time. The so-called fade-out can be turned off by gradually turning down the brightness. This prevents the LED from becoming dark instantaneously when the LED is turned off.

  This operation will be described with reference to switch switching in FIG. Assuming that a signal indicating turn-off is output by the dimming controller 19 at time T = c (S301), the switch means 24 is turned off and the switch means 25 is turned on (S302). As a result, the voltage of the target signal 18 is short-circuited through the resistor 28, the input to the error amplifier 17 becomes zero, and the charge charged in the capacitor 27 is discharged through the resistor 26. At this time, if the value of the resistor 26 is sufficiently large, the capacitor 27 is slowly discharged, and the voltage of the capacitor 27 gradually decreases (S303). Following this, the inverter drive frequency gradually increases to reduce the LED current. When the voltage of the capacitor 27 becomes zero with time, the LED is turned off (S304).

  As described above, by gradually decreasing the voltage of the capacitor 27, the target LED current gradually decreases, the inverter frequency is fed back following this, and the fade-out is extinguished.

  By controlling the inverter drive frequency as described above, fading in and fading out can be easily performed, and discomfort during lighting and extinguishing can be suppressed.

Embodiment 4 FIG.
The fourth embodiment of the present invention is the same as the circuit configuration shown in the first embodiment, and constant setting of the second inductor 8 and the resonant capacitor 9 will be described. Other circuit configurations, circuit operations, and the like are the same as those in the first embodiment, and a description thereof will be omitted.

The second inductor 8 and the resonance capacitor 9 having the circuit configuration shown in FIG. 1 constitute an LC series resonance circuit, and when the LED 13 is not connected, the resonance characteristics as shown in FIG. 11 are obtained. In FIG. 11, assuming that the inductance of the second inductor 8 is L and the capacitance of the resonant capacitor 9 is C, when the frequency is fo = 1 / (2π (LC) ^1/2 ), the resonant frequency is obtained. 9 has a maximum voltage.

  In such a circuit configuration, when the LED is lit at an operating frequency where the inverter drive frequency is lower than the resonance frequency fo, when the LED fails for some reason and becomes open, the inverter circuit 102 operates in the phase advance region. Therefore, the inverter circuit 102 may be destroyed. In addition, when the inverter drive frequency operates near the resonance frequency fo, and the LED similarly causes an open failure, an excessive voltage is generated in the resonance capacitor 9, and the resonance capacitor 9 and the second smoothing capacitor 12 may be destroyed by the overvoltage. is there.

Therefore, in the fourth embodiment, the values of the second inductor 8 and the resonant capacitor 9 are determined so that the inverter driving frequency fm in all light becomes higher than 1/1 / (2π (LC) ^1/2 ). By setting 1 / (2π (LC) ^1/2 ) <fm in this way, the inverter frequency operates in the slow phase region even if the LED fails for some reason, and operates at a frequency higher than the resonance frequency. As a result, an excessive voltage is not generated in the resonant capacitor 9, and the LED lighting device can be prevented from being destroyed. In addition, there is no problem because the light is operated at a higher frequency than in the case of all light during dimming.

  As described above, by avoiding the operation of the inverter drive frequency at a frequency lower than the series resonance frequency of the second inductor 8 and the resonance capacitor 9, it is possible to suppress the destruction of the LED lighting circuit when the LED fails.

Embodiment 5 FIG.
FIG. 15 is a side sectional view of LED lighting apparatus 500 of the fifth embodiment. One of the LED lighting devices described in the first to fourth embodiments is housed inside the lighting device main body 29 of the LED lighting device 500, and is connected to a power source via the power line 31 and the connector 32. The LED 33 is mounted on the light emitting surface of the lighting device main body 29 and connected to the LED lighting device 30 by the wiring 34 to form the LED lighting device 500.

  According to the LED lighting device 500 according to the fifth embodiment, it is possible to supply a substantially constant current to the LED even when there is a variation in the life of the LED, a characteristic variation due to manufacturing variation, a component variation in the LED lighting circuit, and the like. It is possible to suppress variations in brightness between devices, and to achieve accurate LED dimming lighting.

  DESCRIPTION OF SYMBOLS 1 Commercial AC power source, 2 1st rectifier circuit, 3 1st inductor, 4 Switching element, 5 Diode, 6 1st smoothing capacitor, 7 Switching element, 8 2nd inductor, 9 Resonance capacitor, 10 2nd rectifier circuit, 11 DC Cut capacitor, 12 Second smoothing capacitor, 13 LED, 14 LED current detection resistor, 15 LED current detection circuit, 16 Photocoupler, 17 Error amplifier, 18 Target signal, 19 Dimming controller, 20 Voltage control oscillator, 21 Switching element drive Circuit, 22 Inverter current detection resistor, 23 Diode section, 24 Switch means, 25 Switch means, 26 Resistor, 27 Capacitor, 28 Resistor, 29 Lighting device body, 30 LED lighting device, 31 Power line, 32 Connector, 33 LED, 34 Wiring, 101 Boost chopper circuit, 102 inverter circuit, 103 DC power supply circuit, 105 feedback control unit, 106, 107, 108 LED unit, 109 LED module, 110-1, 110-2, 120-1, 120-2, 120-3, 130 LED lighting device, 500 lighting device.

Claims (12)

A DC power supply circuit that converts AC voltage to DC voltage;
An inverter circuit for converting the DC voltage converted by the DC power supply circuit into a high-frequency voltage;
A DC cut capacitor connected to the output side of the inverter circuit to cut a DC component;
An inductor connected in series with the DC cut capacitor;
A resonant capacitor for resonance connected in series with the inductor;
A full-wave rectifier circuit that is connected in parallel with the resonant capacitor, converts an output current from the inverter circuit into a direct current, and supplies the converted direct current to an LED (Light Emitting Diode) from an output terminal;
The corresponding signal and the comparison target signal are input from the comparison target signal output device that detects the corresponding signal corresponding to the LED current flowing through the LED and outputs the comparison target signal to be compared with the corresponding signal. And a feedback control unit that controls the drive frequency of the inverter circuit according to the generated comparison result. The feedback control unit includes:
2. The LED lighting device according to claim 1, wherein a voltage when the current passing through the LED passes through a first resistor is detected as the corresponding signal. The inverter circuit is
A first switching element and a second switching element are connected in series, and the first switching element is connected to a positive electrode side of the DC power supply circuit, and the second switching element is connected to the second switching element via a second resistor. A switching element is connected to the negative side of the DC power supply circuit;
The feedback control unit includes:
2. The LED lighting according to claim 1, wherein a voltage corresponding to a current flowing through either the first switching element or the second switching element is detected from the second resistor as the corresponding signal. apparatus. The full wave rectifier circuit is:
The LED lighting device according to claim 1, further comprising a smoothing capacitor that is connected to the output terminal and smoothes the direct current. A DC power supply circuit that converts AC voltage to DC voltage;
An inverter circuit for converting a DC voltage converted by the DC power supply circuit into a high-frequency voltage;
A DC cut capacitor connected to the output side of the inverter circuit to cut a DC component;
An inductor connected in series with the DC cut capacitor;
A first series LED unit comprising a series connection of a plurality of LEDs (Light Emitting Diodes) and a second series LED unit comprising a series connection of a plurality of LEDs, connected in series with the inductor. A resonant capacitor for resonance connected in parallel with the LED module consisting of the second LED unit connected in antiparallel with the series LED unit of
Detecting the corresponding signal corresponding to the LED current flowing in the LED constituting the LED module, and inputting the comparison target signal from the comparison target signal output device that outputs the comparison target signal to be compared with the corresponding signal; And a comparison target signal to generate a comparison result, and a feedback control unit that controls a drive frequency of the inverter circuit according to the generated comparison result. The feedback control unit includes:
6. The LED lighting device according to claim 5, wherein a voltage generated in a secondary winding of a current transformer by a current passing through the LED is detected as the corresponding signal. The inverter circuit is
A first switching element and a second switching element are connected in series, and the first switching element is connected to a positive electrode side of the DC power supply circuit, and the second switching element is connected to the second switching element via a second resistor. A switching element is connected to the negative side of the DC power supply circuit;
The feedback control unit includes:
6. The LED lighting according to claim 5, wherein a voltage corresponding to a current flowing through either the first switching element or the second switching element is detected from the second resistor as the corresponding signal. apparatus. The feedback control unit includes:
A corresponding signal detector that detects the corresponding signal and outputs the detected corresponding signal;
The corresponding signal output from the corresponding signal detection unit is input, the comparison target signal is input from the comparison target signal output device, and a comparison unit that compares the corresponding signal with the comparison target signal is provided.
The corresponding signal detector is
The LED lighting device according to claim 1, further comprising a photocoupler, wherein the corresponding signal is output by the photocoupler. The feedback control unit includes:
9. A lighting instruction signal for instructing lighting is input to control the drive frequency of the inverter circuit to gradually shift the light emitting state of the LED to a high luminance state. LED lighting device according to. The feedback control unit includes:
2. When an extinction instruction signal for instructing extinction is input, by controlling the drive frequency of the inverter circuit, the light emission state of the LED is gradually changed to a low luminance light emission state, and the light is extinguished. The LED lighting device according to any one of 9. The inverter circuit is
The LED lighting device according to any one of claims 1 to 10, wherein a driving frequency is higher than a series resonance frequency determined by the inductor and the resonance capacitor.   The illuminating device provided with the LED lighting device in any one of Claims 1-11.

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