JP2010287430A - Led lighting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an LED lighting device with little or no generation of flickering. <P>SOLUTION: The LED lighting device includes an input smoothing circuit 10 to output direct current by converting alternating current from a commercial power source 1, an inverter circuit 11 to output direct current with pulsating flow by stepping down the direct current, an output smoothing circuit 12 to arrange smoothing of the direct current with pulsating flow which is output from the inverter circuit 11, and an LED module 5 to which smoothed direct current arranged by the output smoothing circuit 12 is supplied, and the output smoothing circuit 12 includes a capacitor C3 for smoothing purposes arranged in parallel with the LED module 5. For the capacitor C3 of the output smoothing circuit 12, a large capacity capacitor is used, a capacitor with almost double digits larger capacity than a normally used small capacity capacitor with single digit capacity. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an LED lighting device that controls lighting of an LED as an illumination light source.

  2. Description of the Related Art Conventionally, LED lighting devices are known in which an LED array (LED array) as an illumination light source is turned on by an LED lighting device. As this LED lighting device, AC from a commercial power source is converted to DC by a rectifying and smoothing circuit, and then this DC is stepped down through a step-down chopper circuit and the stepped DC with a pulsating current is smoothed by an output smoothing circuit. What supplies to LED as an illumination light source and makes this LED light is known (for example, refer patent document 1).

  By the way, in the LED lighting device described above, a capacitor having a capacitance of 1 to 2 μF is sufficiently lit in the output smoothing circuit without causing noticeable flicker (flicker). In addition, in this LED lighting device, since the capacity | capacitance of a capacitor | condenser is as very small as 1-2 micro F, the whole was able to be comprised compactly.

JP 2004-296205 A

  However, in the LED lighting device described above, slight flicker (flickering) occurs in the LED, and there are cases in which some users are concerned.

  Accordingly, an object of the present invention is to provide an LED lighting device in which flicker (flickering) hardly occurs or does not occur at all in an LED.

Therefore, the present invention provides an input smoothing circuit that outputs alternating current from a commercial power source as direct current, an inverter circuit that steps down the direct current and outputs it as direct current with pulsating current, and pulsating current output from the inverter circuit. An output smoothing circuit for smoothing a certain direct current, and an LED module supplied with the direct current smoothed by the output smoothing circuit,
The output smoothing circuit is an LED lighting device including a smoothing capacitor provided in parallel with the LED module, and the capacitor of the output smoothing circuit has a capacity higher than that of a normally used single-digit small-capacitance capacitor. The LED lighting device uses a large-capacitance capacitor that is approximately two orders of magnitude larger.

  According to this configuration, the flicker (flicker) hardly occurs in the LED, or it can be prevented from occurring at all.

It is a circuit diagram which shows the LED lighting device (LED lighting circuit) which concerns on this invention. It is explanatory drawing which shows the voltage of the input side of the LED lighting device (LED lighting circuit) of FIG. 1, and the electric current of an output side. It is explanatory drawing of the voltage and electric currents, such as an inverter circuit and a diode of FIG. It is a circuit diagram which shows the other example of the LED lighting device (LED lighting circuit) which concerns on this invention.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[Constitution]
FIG. 1 shows an LED lighting device (LED lighting circuit) according to the present invention. In FIG. 1, reference numeral 1 denotes a commercial power source having electric wires 1 a and 1 b, and 2 denotes an LED lighting device used by being connected to the commercial power source 1.

The LED lighting device 2 includes a dimmer 3, a lighting device (lighting circuit) 4, and an LED module 5 including a plurality of LEDs 5a.
<Dimmer 3>
The dimmer 3 includes a triac (dimming element) 6 whose input side is connected to one electric wire 1 a of the commercial power source 1, a coil 7 connected in series to the triac 6, and the triac 6 and the coil 7. A phase control circuit 8 connected in parallel is provided. The phase control circuit 8 inputs a control signal to the triac 6 so as to turn the triac 6 on and off.
<Lighting device 4>
The lighting device 4 has an input terminal 4a connected to the coil 7 and an input terminal 4b connected to the electric wire 1b. Further, the lighting device 4 has an output terminal 4 c connected to the anode side of the LED module 5 and an output terminal 4 d connected to the cathode side of the LED module 5.

The lighting device 4 includes an input filter circuit 9, an input smoothing circuit 10, an inverter circuit 11, and an output smoothing circuit 12.
(Input filter circuit 9)
The input filter circuit 9 includes a resistor R1, a capacitor C1, and a line filter LF. The line filter LF has magnetically coupled coils L1 and L1 ′. The resistor R1 has one end connected to the input terminal 4a and the other end connected to the coil L1 of the line filter LF. One end of the capacitor C1 is connected between the other end of the resistor R1 and the coil L1, and the other end is connected between the input terminal 4b and the coil L1 ′.

Such an input filter circuit 9 prevents the damped vibration generated in the power supply loop of the commercial power source 1 -the dimmer 3 -the lighting device 4 and the like, and prevents external noise.
(Input smoothing circuit 10)
The input smoothing circuit 10 includes a rectifier circuit (full-wave rectifier circuit) RC1 that forms a bridge circuit with diodes and converts alternating current into direct current including pulsating current. Coils L1 and L1 ′ of the input filter circuit 9 are connected to one input side of the rectifier circuit RC1, and alternating current from the commercial power source 1 is input via the input filter circuit 9. .

  Thereby, the rectifier circuit RC1 performs full-wave rectification of the AC voltage supplied from the commercial power supply 1 via the dimmer 3 and the line filter LF. A positive side wiring 13 is connected to the positive output side of the rectifier circuit RC1, and a negative side (ground side) wiring 14 is connected to the negative output side of the rectifier circuit RC1. The plus side wiring 13 is connected to the plus side output terminal 4 c of the lighting device 4. Further, the minus side wiring 14 is connected to the output terminal 4d through the resistor R2, the transistor Q1, and the inductor L2.

Further, the input smoothing circuit 10 includes a capacitor C2 that smoothes the AC voltage rectified by the rectifying circuit RC1. The capacitor C2 is connected to the plus side wiring 13 and the minus side wiring 14 of the rectifier circuit RC1.
(Inverter circuit 11)
The inverter circuit 11 uses a general step-down chopper circuit that converts a DC voltage from the input smoothing circuit 10 into a predetermined DC voltage.

  The inverter circuit 11 includes a diode D1, a transistor (switching element) Q1, a resistor R2, and an inductor L2.

  The resistor R2, the transistor Q1, and the inductor L2 are interposed in the middle of the minus side wiring 14, and are arranged in this order from the rectifier circuit RC1 to the output terminal 4d side.

  The diode D1 has an anode side connected to the transistor Q1 and a cathode side connected to the plus side wiring 13. Reference numerals 14 a and 14 b are part of the minus side wiring 14. The wiring 14a connects the diode D1 and the transistor Q1, and the wiring 14b connects the output terminal 4d and the middle of the wiring 14a via the inductor L2.

  Further, the inverter circuit 11 includes a control circuit (control IC) IC1 that controls ON / OFF of the transistor Q1. The control circuit IC1 turns on the transistor Q1 by inputting a control signal to the base of the transistor Q1 via the resistor R3.

Further, the control circuit IC1 detects a current flowing between the resistor R2 and the transistor Q1 via the wiring 15. When a current of a predetermined value or more flows, the control circuit IC1 interrupts the output of the control signal and supplies the current to the base of the transistor Q1 The control signal input is stopped.
(Output smoothing circuit 12)
The output smoothing circuit 12 has a capacitor C3. One end of the capacitor C3 is connected to the wiring 13 between the cathode side of the diode D1 and the output terminal 4c, and the other end is connected to the wiring 14b between the other end of the inductor L2 and the output terminal 4d. The capacitor C3 is a large-capacity capacitor having a three-digit capacity compared to a small-capacitance capacitor having a single-digit capacity. For example, a normal small-capacitance capacitor is, for example, 1 to 2 μF, whereas a large-capacitance capacitor of 100 μF or more or 400 μF or more is used for the capacitor C3. That is, a capacitor having a large capacity several hundred times that of the small-capacitance capacitor is used for the capacitor C3. If the capacitor C3 is between 100 μF and 400 μm and the capacitor C3 is 400 μm or more, it will not be recognized at all.
[Action]
Next, the operation of such a configuration will be described.

  When an AC voltage having a sinusoidal waveform with a half cycle T as shown in FIG. 2A is input from the commercial power supply 1 to the dimmer 3, the dimmer 3 displays FIG. As shown in b), an AC voltage that is cut-controlled only by the voltage waveform interval t1 is output. The alternating current at this time has a waveform of peaks i1 and i2 having sharp edges on the positive side and rising and falling portions as shown in FIG. Similarly, the negative side has peaks -i1, -i2. The alternating voltage in FIG. 2B and the alternating current in FIG. 2C are input to the lighting device 4 from the input terminals 4a and 4b.

  The alternating voltage in FIG. 2B and the alternating current in FIG. 2C are input to the input filter circuit 9. The AC voltage from the input filter circuit 9 is input to the input smoothing circuit 10. This AC voltage is full-wave rectified by the rectifier circuit RC1 of the input smoothing circuit 10 and smoothed by the capacitor C2, and then output from the input smoothing circuit 10 as a DC voltage having a pulsating current. Then, the DC voltage having the pulsating current is applied to the inverter circuit 11.

The DC voltage including the pulsating current from the input smoothing circuit 10 is applied to the capacitor C3 and the LED module 5, and is applied to the transistor Q1 via the capacitor C3 and the LED module 5.
(Turn on transistor Q1)
On the other hand, the control circuit IC1 of the inverter circuit 11 inputs, for example, a control signal having a frequency of about 100 kHz to the base of the transistor Q1. At this time, the control circuit IC1 inputs a control signal to the base of the transistor Q1 during the period st every predetermined half cycle ST (period st1 + st), and sets the transistor Q1 every predetermined half cycle T during the period st. Only ON.

  Accordingly, a current Q1i flows through the transistor Q1 during the period st as shown in FIG. At this time, the voltage of the transistor Q1 is “0” during the period st as shown in FIG.

  Further, no current flows through the diode D1 during the period st as shown in FIG. 3B, and the voltage of the diode D1 becomes D1v during the period st as shown in FIG. 3B.

With the ON control of the transistor Q1 by the control circuit IC1, the current Io-Q flows through the LED module 5, the inductor L2, the transistor Q1, and the resistor R2 when the transistor Q1 is ON. Due to the current Io-Q, the voltage L2v is generated between both ends of the inductor L2 only during the period st as shown in FIG.
(Turn off transistor Q1)
The current flowing between the transistor Q1 and the resistor R2 is detected by the control circuit IC1 via the wiring 15. When the current Io-Q flowing through the inductor L2 becomes equal to or higher than a predetermined value, the control circuit IC1 goes to the transistor Q1. Is stopped and the transistor Q1 is turned off.

  Accordingly, no current flows through the transistor Q1 during the period st1, as shown in FIG. At this time, the voltage of the transistor Q1 is Q1v during the period st1, as shown in FIG.

In addition, a current D1i flows through the diode D1 during the period st1, as shown in FIG. 3B. At this time, the voltage of the diode D1 is “0” during the period st1, as shown in FIG.
(Lighting state of LED module 5)
Such ON / OFF control of the transistor Q1 by the control circuit IC1 is repeatedly performed. When the transistor Q1 is on, the current Io-Q flows through the LED module 5, the inductor L2, the transistor Q1, and the resistor R2, and when the transistor Q1 is off, the current Io flows through the LED module 5, the inductor L2, and the diode D1. -D flows.

  At this time, the voltage between both ends of the inductor L2 becomes “0” during the period st1, as shown in FIG. 3C, and becomes L2v only during the period st.

  Moreover, since the current flowing through the inductor L2 is further smoothed by the capacitor C3 as shown by L2i (Q1i + D1i) as shown in FIG. 3C, the LED module 5 is turned on by the current Io-Q flowing through the LED module 5. However, flicker (flicker) does not occur in the LED module 5.

  In the lighting device 4, a pulsating current flows through the inductor L2 and the LED module 5 at an operating frequency (several tens of kHz or more) determined by the control circuit IC1. The waveform of the pulsating current has a shape in which a change in current flowing through the transistor Q1 and a change in current flowing through the inductor L2 are combined. At this time, when the capacitor C3 has a small capacity, the change in the waveform of the pulsating current flowing through the LED module 5 is large, and thus the LED module 5 flickers at a commercial frequency.

  However, by increasing the capacity of the capacitor C3 as in this embodiment, the current I2 continues over the entire period as shown in FIG. 2E, and the change in the waveform of the pulsating current is very small. The flicker of the LED module 5 is not recognized due to the commercial frequency of the commercial power supply.

  Here, when the capacity of the capacitor C3 is increased, flicker (flicker) is not recognized. That is, if the capacitor C3 is between 100 μF and 400 μF and the capacitor C3 is 400 μF or more, flicker (flicker) is not recognized at all.

Further, as shown in FIG. 2D, when the current I1 is supplied to the LED lighting device 2 only during the period t every half cycle T, the current I2 flowing through the LED 5a of the LED module 5 is as shown in FIG. Therefore, it becomes necessary to change the output current value in anticipation of this average current. This change can be realized by changing the value of the resistor R2.
[Modification 1]
In the above-described embodiment, an example of a non-insulated type using a step-down chopper circuit system is shown, but the present invention is not necessarily limited thereto. For example, as shown in FIG. 4, an insulation type such as an ON-OFF circuit system or an ON-ON circuit system can be formed by inserting a transformer TR between the inverter circuit 11 and the output smoothing circuit 12.

  The transformer TR in FIG. 4 includes a primary coil La and a secondary coil Lb as inductors. The primary coil La is magnetically coupled to the primary coil La. The secondary coil Lb interposed between the plus side wiring 13 (plus side of the input smoothing circuit 10) and the transistor Q1.

  Further, the output smoothing circuit 12 has a diode D1 whose cathode side is connected to the output terminal 4c via the wiring 13d. A secondary coil Lb of the transformer TR is interposed between the anode side of the diode D1 and the wiring 14b of the output smoothing circuit 12.

  In this configuration, when the transistor Q1 is turned on by the control circuit IC1, a pulsating direct current flows in the primary coil La of the transformer TR, and a pulsating direct current voltage is generated in the secondary coil Lb of the transformer TR. . This pulsating DC voltage is further smoothed by the capacitor C3 via the diode D1 and applied between the output terminals 4c and 4d. Thereby, the pulsating direct current output from the input smoothing circuit 9 is further smoothed and flows to an LED module (not shown) (module 5 in FIG. 1) connected to the output terminals 4c and 4d. Accordingly, the LED module is turned on by a direct current.

  On the other hand, when the transistor Q1 is turned off by the control circuit IC1, the LED module (not shown) connected to the output terminals 4c and 4d via the transformer TR and the diode D1 by the energy stored in the capacitor C3 (module 5 in FIG. 1). Flowing into. Accordingly, the LED module is turned on by a direct current.

  Except for this action, the inductor L2 of the above-described embodiment is merely the transformer TR, and is substantially the same as the above-described embodiment. Therefore, this configuration can be set so as to perform the same control as in the above-described embodiment.

  As described above, the LED lighting device according to the embodiment of the present invention has the input smoothing circuit 10 that outputs the alternating current from the commercial power source 1 as a direct current, and the direct current with a pulsating current by reducing the direct current. An inverter circuit 11, an output smoothing circuit 12 that smoothes the pulsating direct current output from the inverter circuit 11, and an LED module 5 that is supplied with the direct current smoothed by the output smoothing circuit 12. The output smoothing circuit 12 includes a smoothing capacitor C3 provided in parallel with the LED module 5. In addition, as the capacitor C3 of the output smoothing circuit 12, a large-capacitance capacitor having a capacity approximately two orders of magnitude larger than that of a normally used one-digit small capacity capacitor is used.

  According to this configuration, flicker (flickering) can be prevented from occurring at all in the LED.

  In the LED lighting device according to the embodiment of the present invention, the inverter circuit 11 stores energy when the switching element (transistor Q1) is turned on and the switching element that turns on / off the direct current from the input smoothing circuit 10. And a control circuit IC1 that performs ON / OFF control of the switching element (transistor Q1).

  According to this configuration, it is possible to prevent flicker (flicker) from occurring at all in the LED with a simple configuration.

  Furthermore, in the LED lighting device according to the embodiment of the present invention, the inverter circuit 11 allows the direct current to flow to the positive input side of the output smoothing circuit 12 so that the switching element (transistor Q1) and the output smoothing circuit 12 A diode D1 is provided between the positive input side. The inductor L2 is interposed between the wiring 14a between the diode D1 and the switching element (transistor Q1) and the negative input side of the output smoothing circuit 12. Further, the inverter circuit is configured to turn off the switching element for a predetermined time when the current flowing through the transistor becomes a predetermined value or more.

  According to this configuration, the switching element can be turned on and off with a simple configuration so that no flicker (flicker) occurs in the LED.

  Further, in the LED lighting device according to the embodiment of the present invention, the inverter circuit 11 includes a coil (L, La.Lb) as the inductor, and has a transformer for supplying the stepped down direct current to the output smoothing circuit 12. In addition, the inverter circuit is configured to turn off the switching element for a predetermined time when the current flowing through the transistor exceeds a predetermined value.

  According to this configuration, the switching element can be turned on and off with a simple configuration so that no flicker (flicker) occurs in the LED.

DESCRIPTION OF SYMBOLS 1 ... Commercial power supply 10 ... Input smoothing circuit 11 ... Inverter circuit 12 ... Output smoothing circuit 5 ... LED module C3 ... Capacitor Q1 ... Transistor (switching element)
L2 ... Inductor IC1 ... Control circuit D1 ... Diode TR ... Transformer La ... Primary coil Lb ... Secondary coil

Claims (4)

An input smoothing circuit that outputs alternating current from a commercial power supply as direct current, an inverter circuit that steps down the direct current and outputs it as direct current with pulsating current, and an output that smoothes direct current with pulsating current output from the inverter circuit A smoothing circuit, and an LED module to which direct current smoothed by the output smoothing circuit is supplied,
The output smoothing circuit is an LED lighting device including a smoothing capacitor provided in parallel with the LED module,
The LED lighting device characterized in that a large-capacitance capacitor having a capacity approximately two orders of magnitude larger than a normally used single-digit small capacity capacitor is used as the capacitor of the output smoothing circuit.   2. The LED lighting device according to claim 1, wherein the inverter circuit includes a switching element that turns on and off direct current from the input smoothing circuit, an inductor that accumulates energy when the switching element is turned on, and an ON state of the switching element. An LED lighting device comprising a control circuit that performs OFF control.   3. The LED lighting device according to claim 2, wherein the inverter circuit is interposed between the switching element and the positive input side of the output smoothing circuit so that a direct current can flow to the positive input side of the output smoothing circuit. The inductor is interposed between a wiring between the diode and the switching element and a negative input side of the output smoothing circuit, and the inverter circuit has a predetermined current flowing through the transistor. An LED lighting device that turns off the switching element for a predetermined time when the value becomes equal to or greater than a value.   3. The LED lighting device according to claim 2, wherein the inverter circuit includes a coil as the inductor and includes a transformer that supplies a stepped-down direct current to the output smoothing circuit, and the inverter circuit has a predetermined current flowing through the transistor. An LED lighting device that turns off the switching element for a predetermined time when the value becomes equal to or greater than a value.

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