JP6527741B2

JP6527741B2 - LED lighting device

Info

Publication number: JP6527741B2
Application number: JP2015078865A
Authority: JP
Inventors: 充弘門田; 古矢　幸生; 幸生古矢; 古城　卓也; 卓也古城; 菅原　浩一; 浩一菅原
Original assignee: Hitachi Global Life Solutions Inc
Current assignee: Hitachi Global Life Solutions Inc
Priority date: 2015-04-08
Filing date: 2015-04-08
Publication date: 2019-06-05
Anticipated expiration: 2035-04-08
Also published as: JP2016201194A

Description

本発明は，ＬＥＤ点灯装置に関する。
The present invention relates to an LED lighting device.

発光ダイオード（以下，ＬＥＤ：ＬｉｇｈｔＥｍｉｔｔｉｎｇＤｉｏｄｅ）は，高効率かつ長寿命の光源デバイスであり，自動車の車内照明やヘッドライト，信号機，液晶ディスプレイのバックライト，一般照明などの幅広い分野において利用されている。また，オフィス，店舗，工場といったあらゆる施設において，省エネ施策としてＬＥＤ照明の導入が進んでいる。 Light emitting diodes (hereinafter, LED: Light Emitting Diode) are light source devices with high efficiency and long life, and are used in a wide range of fields such as automobile interior lighting and headlights, traffic lights, backlights of liquid crystal displays, general lighting, etc. There is. In addition, LED lighting is being introduced as an energy saving measure in all facilities such as offices, stores, and factories.

ＬＥＤを点灯させるＬＥＤ点灯装置は，電力変換回路を備えており，これによって電源電圧を変換してＬＥＤ負荷に給電する。照明用途などで交流電源を用いる場合，上記の電力変換回路の構成として，ＡＣ−ＤＣ回路によって交流電源電圧を一旦直流電圧に変換し，この直流電圧をＤＣ−ＤＣ回路によって電圧変換してＬＥＤ負荷に給電する構成が用いられる。このうちＡＣ−ＤＣ回路は，入力電流の低次高調波成分を低減する力率改善（ＰＦＣ：ＰｏｗｅｒＦａｃｔｏｒＣｏｒｒｅｃｔｉｏｎ）回路としての役割を担い，ＤＣ−ＤＣ回路は，ＬＥＤ負荷に出力する電流（以下，ＬＥＤ電流と記す）を制御する。具体的な回路方式として，ＡＣ−ＤＣ回路を全波整流回路（ダイオードブリッジ）と昇圧チョッパで，ＤＣ−ＤＣ回路を降圧チョッパでそれぞれ実現する方式がよく用いられる。すなわち，ＡＣ−ＤＣ回路とＤＣ−ＤＣ回路の両者にスイッチング方式の電源回路を利用する方式である。 The LED lighting device for lighting the LED includes a power conversion circuit, thereby converting the power supply voltage and supplying the LED load. When using an AC power supply for lighting applications etc., as the configuration of the above power conversion circuit, the AC power supply voltage is once converted to a DC voltage by an AC-DC circuit, and this DC voltage is voltage converted by a DC-DC circuit to perform LED load The configuration for feeding power is used. Among these, the AC-DC circuit plays a role as a Power Factor Correction (PFC) circuit that reduces low-order harmonic components of the input current, and the DC-DC circuit , LED current) is controlled. As a specific circuit system, a system in which an AC-DC circuit is realized by a full wave rectifier circuit (diode bridge) and a step-up chopper and a DC-DC circuit is realized by a step-down chopper is often used. That is, it is a system which utilizes the power supply circuit of a switching system for both AC-DC circuit and DC-DC circuit.

近年、小型のＬＥＤ点灯装置の実現が望まれている。 In recent years, realization of a small-sized LED lighting device is desired.

上記の構成と比べて小型のＬＥＤ点灯装置を実現するために，ＤＣ−ＤＣ回路を省略し，ＡＣ−ＤＣ回路の出力をＬＥＤ負荷に直接接続する構成（ワンコンバータ方式と呼ばれることもある）が考えられる。 Compared with the above configuration, in order to realize a small LED lighting device, the DC-DC circuit is omitted, and the output of the AC-DC circuit is directly connected to the LED load (sometimes called one converter method). Conceivable.

小型のＬＥＤ点灯装置を実現する別の方式として，ＤＣ−ＤＣ回路として降圧チョッパのようなスイッチング回路の代わりにドロッパ方式の電源回路（以下、ドロッパ回路）を用いる構成が考えられる。ドロッパ回路は，スイッチング回路において大きな体積を占めるチョークコイル（またはトランス）が不要であるため，ＬＥＤ点灯装置の小型化に有利である。また，ＡＣ−ＤＣ回路の出力電圧をＬＥＤ負荷の電圧（以下，ＬＥＤ電圧と記す）より十分高く設定して，ドロッパ回路を定電流回路として動作させれば，ＡＣ−ＤＣ回路を力率改善動作させる場合もＬＥＤ電流を一定に（脈動なしで）制御できる。特開２００６−３１４１６８号（特許文献１）には，ドロッパ回路（文献ではシリーズレギュレータと記載されているが，ドロッパ回路と考えられる）によってＬＥＤに給電する構成が示されている。
As another system for realizing a small-sized LED lighting device, a configuration using a dropper type power supply circuit (hereinafter referred to as a dropper circuit) as a DC-DC circuit instead of a switching circuit such as a step-down chopper can be considered. The dropper circuit is advantageous for the miniaturization of the LED lighting device because a choke coil (or a transformer) which occupies a large volume in the switching circuit is unnecessary. Also, if the output voltage of the AC-DC circuit is set sufficiently higher than the voltage of the LED load (hereinafter referred to as the LED voltage) and the dropper circuit is operated as a constant current circuit, the power factor improvement operation of the AC-DC circuit Also in the case of making it possible to control the LED current constant (without pulsation). Japanese Patent Laid-Open No. 2006-314168 (Patent Document 1) shows a configuration in which power is supplied to an LED by a dropper circuit (which is described as a series regulator in the literature but considered as a dropper circuit).

特開２００６−３１４１６８号公報JP, 2006-314168, A

ワンコンバータ方式では，ＡＣ−ＤＣ回路によって力率改善を行う都合上，ＬＥＤ電流が交流電源（の２倍）の周波数で大きく脈動する。ＬＥＤ及び点灯装置の寿命を考慮すると，この脈動の振幅，特にピーク値は小さくするべきである。また，周波数が高いとはいえ，ちらつき（フリッカ）の点からもＬＥＤ電流の脈動は小さい方がよい。ＡＣ−ＤＣ回路の出力端子間に接続するコンデンサを大容量化すればＬＥＤ電流の脈動を低減できるが，コンデンサの体積が大きくなり，ＬＥＤ点灯装置を小型化するメリットは損なわれる。 In the one-converter system, the LED current greatly pulsates at the frequency of (twice that of) the AC power supply for the purpose of improving the power factor by the AC-DC circuit. Considering the lifetime of the LED and the lighting device, the amplitude of this pulsation, especially the peak value, should be small. Moreover, although the frequency is high, it is preferable that the pulsation of the LED current be small also in terms of flicker. Pulsating the LED current can be reduced by increasing the capacitance of the capacitor connected between the output terminals of the AC-DC circuit, but the volume of the capacitor increases, and the merit of downsizing the LED lighting device is lost.

一方，ドロッパ方式定電流回路でも半導体素子を利用するが，その制御方式がスイッチング回路の場合とは異なる。ドロッパ回路では，入力電圧の大きさに依らず一定の電流を出力するように半導体素子の導通抵抗が制御される。その結果，半導体素子には入力電圧と負荷電圧の差分がドロップ電圧として印加される。ドロップ電圧と負荷電流の積として大きな損失が発生し，ＬＥＤ点灯装置の効率を低下させる。また，放熱フィンを取り付けるなどして半導体素子の放熱を強化する必要があり，これがＬＥＤ点灯装置の大型化を招く。 On the other hand, semiconductor elements are used in the dropper type constant current circuit, but the control method is different from that in the switching circuit. In the dropper circuit, the conduction resistance of the semiconductor element is controlled so as to output a constant current regardless of the magnitude of the input voltage. As a result, the difference between the input voltage and the load voltage is applied to the semiconductor device as a drop voltage. A large loss occurs as the product of the drop voltage and the load current, which reduces the efficiency of the LED lighting device. In addition, it is necessary to enhance the heat radiation of the semiconductor element by attaching a radiation fin or the like, which leads to the enlargement of the LED lighting device.

以上を踏まえて，小型・高効率であり，ＬＥＤ電流の脈動（ピーク値）を所定値以下に低減可能なＬＥＤ点灯装置を実現することが本発明の課題である。

Based on the above, it is an object of the present invention to realize an LED lighting device that is compact and has high efficiency and can reduce pulsation (peak value) of LED current to a predetermined value or less.

上記課題は，交流電源電圧を整流するＡＣ−ＤＣ回路と，該ＡＣ−ＤＣ回路の出力電圧を平滑する第１コンデンサと，前記ＡＣ−ＤＣ回路の出力端子間に接続されるＬＥＤ負荷と半導体素子と電流検出手段と，前記ＡＣ−ＤＣ回路と前記半導体素子を制御する制御回路を備え，該制御回路は，前記半導体素子をドロッパ方式（リニアレギュレータ方式）定電流回路用の素子として利用する第１動作と，前記半導体素子をオン（スルー）状態として前記ＡＣ−ＤＣ回路によって出力を制御する第２動作の２通りの動作を行うことを特徴とするＬＥＤ点灯装置によって解決される。
The above-mentioned subject includes an AC-DC circuit for rectifying an AC power supply voltage, a first capacitor for smoothing an output voltage of the AC-DC circuit, and an LED load and a semiconductor element connected between output terminals of the AC-DC circuit. A current detection means, the AC-DC circuit, and a control circuit for controlling the semiconductor element, the control circuit using the semiconductor element as an element for a dropper type (linear regulator type) constant current circuit The LED lighting device is characterized by performing two operations of an operation and a second operation of controlling the output by the AC-DC circuit with the semiconductor element in the on (through) state.

小型・高効率であり，ＬＥＤ電流の脈動（ピーク値）を所定値以下に低減可能なＬＥＤ点灯装置を実現する。
A small size, high efficiency LED lighting device capable of reducing the pulsation (peak value) of the LED current to a predetermined value or less is realized.

実施例１におけるＬＥＤ点灯装置のブロック図である。FIG. 2 is a block diagram of an LED lighting device in Embodiment 1. 実施例１の動作タイミングチャートである。7 is an operation timing chart of the first embodiment. 本発明（図２）との比較対象であり，ＡＣ−ＤＣ回路の出力をＬＥＤ負荷に直接接続する構成において考えられる動作タイミングチャートである。It is an operation timing chart considered in the composition which is comparison object with the present invention (Drawing 2), and directly connects the output of an AC-DC circuit to LED load. 実施例１（図１）におけるＡＣ−ＤＣ回路１０２と制御回路１０６の具体例である。It is a specific example of the AC-DC circuit 102 and the control circuit 106 in Example 1 (FIG. 1). 実施例１の別例であり，ＡＣ−ＤＣ回路１０２としてフライバックコンバータ１１８を，半導体素子１０４としてバイポーラトランジスタを用いる構成である。This is another example of the first embodiment, in which a flyback converter 118 is used as the AC-DC circuit 102 and a bipolar transistor is used as the semiconductor element 104. 実施例１の別例であり，ＡＣ−ＤＣ回路１０２として昇圧チョッパ１２５を用いる構成である。This is another example of the first embodiment, and is configured to use the step-up chopper 125 as the AC-DC circuit 102. 実施例２の動作タイミングチャートである。7 is an operation timing chart of the second embodiment. 実施例２における制御回路１０６の具体例である。21 is a specific example of the control circuit 106 in the second embodiment. 実施例３の動作タイミングチャートである。15 is an operation timing chart of the third embodiment. 実施例３におけるＬＥＤ点灯装置の具体例である。21 is a specific example of the LED lighting device in the third embodiment. 実施例３の動作タイミングチャートの別例である。15 is another example of the operation timing chart of the third embodiment. 実施例４におけるＬＥＤ点灯装置のブロック図である。FIG. 14 is a block diagram of an LED lighting device in a fourth embodiment. 実施例４の動作タイミングチャートである。15 is an operation timing chart of the fourth embodiment.

以下，本発明の実施例について，図面を用いて説明する。 Hereinafter, embodiments of the present invention will be described with reference to the drawings.

＜ブロック図＞
図１は，実施例１におけるＬＥＤ点灯装置のブロック図である。図１のＬＥＤ点灯装置は，外部から入力される交流電源１００の電圧を変換してＬＥＤ負荷１０１に出力（給電）する。ＬＥＤ点灯装置は，交流電源１００の電圧を整流するＡＣ−ＤＣ回路１０２と，ＡＣ−ＤＣ回路１０２の出力電圧を平滑するコンデンサ１０３（第１コンデンサ）と，ＡＣ−ＤＣ回路１０２の出力端子間に接続されるＬＥＤ負荷１０１と半導体素子１０４と電流検出手段１０５と，ＡＣ−ＤＣ回路１０２と半導体素子１０４を制御する制御回路１０６を備える。 <Block diagram>
FIG. 1 is a block diagram of the LED lighting device in the first embodiment. The LED lighting device of FIG. 1 converts the voltage of the AC power supply 100 input from the outside and outputs (feeds) to the LED load 101. The LED lighting device includes an AC-DC circuit 102 for rectifying the voltage of the AC power supply 100, a capacitor 103 (first capacitor) for smoothing the output voltage of the AC-DC circuit 102, and an output terminal of the AC-DC circuit 102. The LED load 101, the semiconductor element 104, the current detection means 105, and the control circuit 106 for controlling the AC-DC circuit 102 and the semiconductor element 104 are provided.

ＬＥＤ負荷１０１は，少なくとも１個のＬＥＤを備える。ＬＥＤ負荷１０１が複数のＬＥＤを備えるとき，ＬＥＤの個数や接続形態は問わない。また，ＬＥＤには，保護用素子などを内蔵したＬＥＤモジュールも含まれる。 The LED load 101 comprises at least one LED. When the LED load 101 includes a plurality of LEDs, the number and the connection form of the LEDs do not matter. In addition, the LED also includes an LED module incorporating a protective element and the like.

図１では，半導体素子１０４としてＭＯＳＦＥＴ（Ｍｅｔａｌ−Ｏｘｉｄｅ−ＳｅｍｉｃｏｎｄｕｃｔｏｒＦｉｅｌｄ−ＥｆｆｅｃｔＴｒａｎｓｉｓｔｏｒ）を示したが，バイポーラトランジスタやＩＧＢＴ（ＩｎｓｕｌａｔｅｄＧａｔｅＢｉｐｏｌａｒＴｒａｎｓｉｓｔｏｒ）など他種の素子であってもよい。 Although FIG. 1 shows a MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor) as the semiconductor element 104, another type of element such as a bipolar transistor or an IGBT (Insulated Gate Bipolar Transistor) may be used.

電流検出手段１０５として，抵抗（シャント抵抗）が一般的であるが，ホールセンサなど他種の検出手段であってもよい。電流検出手段１０５は，ＬＥＤ電流を検出するために利用されるが，図１のようにＬＥＤ電流を直接検出する位置に接続する必要はない。例えば，ＡＣ−ＤＣ回路１０２の部品に流れる電流を検出する位置に電流検出手段１０５を接続し，この部品の電流から間接的にＬＥＤ電流を検出してもよい。 A resistor (shunt resistor) is generally used as the current detection means 105, but other types of detection means such as a Hall sensor may be used. The current detection means 105 is used to detect the LED current, but does not have to be connected to a position where the LED current is directly detected as shown in FIG. For example, the current detection means 105 may be connected to a position where the current flowing to the component of the AC-DC circuit 102 is detected, and the LED current may be indirectly detected from the current of this component.

制御回路１０６は，図１に記載したように，半導体素子１０４をドロッパ方式（リニアレギュレータ方式）定電流回路用の素子として利用する第１動作と，半導体素子１０４をオン（スルー）状態としてＡＣ−ＤＣ回路１０２によって出力電流を制御する第２動作の２通りの動作を行う。 As described in FIG. 1, the control circuit 106 performs the first operation using the semiconductor element 104 as an element for a dropper type (linear regulator type) constant current circuit, and performs the AC operation with the semiconductor element 104 in the on (through) state. The DC circuit 102 performs two operations of the second operation of controlling the output current.

図１では，制御回路１０６がＡＣ−ＤＣ回路１０２に発生する電圧または電流を検出する構成を示したが，制御回路１０６の構成によってはこの検出を省略できる。また，図１では，ＬＥＤ点灯装置の外部から制御回路１０６に調光信号が入力され，制御回路１０６が調光信号に従ってＬＥＤ電流を可変することを想定した。調光信号は，専用の制御配線を介して制御回路１０６に入力されるものであっても，無線通信によって制御回路１０６に入力されるものであってもよい。ＬＥＤ電流を一定値に制御するのであれば，調光信号は不要である。
Although FIG. 1 shows the configuration in which the control circuit 106 detects the voltage or current generated in the AC-DC circuit 102, this detection may be omitted depending on the configuration of the control circuit 106. Further, in FIG. 1, it is assumed that the dimming signal is input to the control circuit 106 from the outside of the LED lighting device, and the control circuit 106 varies the LED current according to the dimming signal. The dimming signal may be input to the control circuit 106 via a dedicated control wiring, or may be input to the control circuit 106 by wireless communication. If the LED current is controlled to a constant value, the dimming signal is unnecessary.

＜動作タイミングチャート＞
図２は，実施例１の動作タイミングチャートである。具体的には，交流電源１００の１周期における交流電源１００の電圧，ＡＣ−ＤＣ回路１０２の出力電圧，ＬＥＤ電圧，半導体素子１０４の電圧，ＬＥＤ電流の動作波形を示した。半導体素子１０４の電圧とは，半導体素子１０４がＭＯＳＦＥＴであればそのドレイン−ソース電圧，バイポーラトランジスタやＩＧＢＴであればコレクタ−エミッタ電圧である。また，図２には制御回路１０６の動作についても記載しており，制御回路１０６は（１）と記載された期間において上記の第１動作を，（２）と記載された期間において第２動作をそれぞれ行う。図２では，ＡＣ−ＤＣ回路１０２によって力率改善を行う，すなわちＰＦＣ回路として動作させることを想定した。そのため，図２のようにＬＥＤ電流は脈動するが，後に説明するようにＡＣ−ＤＣ回路１０２によってその平均値を所定の第１設定値（Ｉ１）に制御することを想定した。 <Operation timing chart>
FIG. 2 is an operation timing chart of the first embodiment. Specifically, the operating waveforms of the voltage of the AC power supply 100, the output voltage of the AC-DC circuit 102, the LED voltage, the voltage of the semiconductor element 104, and the LED current in one cycle of the AC power supply 100 are shown. The voltage of the semiconductor element 104 is the drain-source voltage if the semiconductor element 104 is a MOSFET, and the collector-emitter voltage if the semiconductor element 104 is a bipolar transistor or IGBT. FIG. 2 also describes the operation of the control circuit 106, and the control circuit 106 performs the first operation in the period described as (1) and the second operation in the period described as (2). Do each one. In FIG. 2, it is assumed that power factor correction is performed by the AC-DC circuit 102, that is, it is operated as a PFC circuit. Therefore, although the LED current pulsates as shown in FIG. 2, it is assumed that the average value is controlled to a predetermined first set value (I1) by the AC-DC circuit 102 as described later.

図３には，本発明（図２）との比較対象として，ＡＣ−ＤＣ回路の出力をＬＥＤ負荷に直接接続する（図１において半導体素子１０４をショートする）構成において考えられる動作タイミングチャートを示した。図３は本発明の動作タイミングチャートではないため，交流電源やＡＣ−ＤＣ回路などに付加する符号は省略した。既に説明したように，ＡＣ−ＤＣ回路が力率改善動作する場合，ＬＥＤ電流は交流電源（の２倍）の周波数でほぼ正弦波状に脈動する。ＬＥＤ電流の平均値については図２と同様にＩ１とし，その振幅をΔＩとした。ＬＥＤ電圧もＬＥＤ電流と同期して脈動するが，ＬＥＤ負荷の電圧−電流（Ｖ−Ｉ）特性上，ＬＥＤ電流に比べて脈動振幅は十分小さいため，図３では一定値とした。なお，電流検出手段での電圧降下を無視すれば，図３に記載したようにＡＣ−ＤＣ回路の出力電圧とＬＥＤ電圧は一致する。 FIG. 3 shows a possible operation timing chart in a configuration in which the output of the AC-DC circuit is directly connected to the LED load (the semiconductor element 104 is shorted in FIG. 1) as a comparison object with the present invention (FIG. 2) The Since FIG. 3 is not an operation timing chart of the present invention, the reference numerals attached to the AC power supply and the AC-DC circuit are omitted. As described above, when the AC-DC circuit performs a power factor correction operation, the LED current pulsates in a substantially sinusoidal manner at a frequency of (two times) that of the AC power supply. The average value of the LED current is I1 as in FIG. 2 and the amplitude is ΔI. Although the LED voltage also pulsates in synchronization with the LED current, the pulsation amplitude is sufficiently smaller than the LED current in view of the voltage-current (V-I) characteristics of the LED load, and therefore, it is set to a constant value in FIG. If the voltage drop in the current detection means is neglected, the output voltage of the AC-DC circuit and the LED voltage match as shown in FIG.

図２の本発明では，交流電源周期のうちＬＥＤ電流が大きくなる期間において，制御回路１０６が第１動作を行う。すなわち，半導体素子１０４をドロッパ方式定電流回路の素子として利用し，その電流設定値を所定の第２設定値（Ｉ２）とすることで，ＬＥＤ電流のピーク値をＩ２に抑制（クランプ）する。図２では省略したが，制御回路１０６は，半導体素子１０４に流れる電流がＩ２で一定になるように，半導体素子１０４に制御信号を出力する（半導体素子１０４がＭＯＳＦＥＴやＩＧＢＴであれば，ゲート電圧を出力し，バイポーラトランジスタであれば，ベース電流を出力する）。ＬＥＤ電流がＩ２で一定となる一方，ＡＣ−ＤＣ回路１０２の出力電圧がＬＥＤ電圧より高くなり，図２のように変動する。半導体素子１０４の電圧，すなわちドロップ電圧は，ＡＣ−ＤＣ回路１０２の出力電圧とＬＥＤ電圧の差分となる。以上から，ＬＥＤ電流脈動のピーク値を所定値に制御可能であり，ＬＥＤ負荷１０１やＬＥＤ点灯装置に過大な電流が流れること，ひいては，これらの寿命短縮を防止できる。ただし，この期間では，上記の通り半導体素子１０４でドロップ電圧が発生するため，ドロップ電圧とＩ２の積として半導体素子１０４の損失が発生する。 In the present invention shown in FIG. 2, the control circuit 106 performs the first operation during a period in which the LED current increases in the AC power supply cycle. That is, the peak value of the LED current is suppressed (clamped) to I2 by using the semiconductor element 104 as an element of the dropper type constant current circuit and setting the current setting value to a predetermined second setting value (I2). Although omitted in FIG. 2, the control circuit 106 outputs a control signal to the semiconductor element 104 so that the current flowing to the semiconductor element 104 becomes constant at I2 (if the semiconductor element 104 is a MOSFET or an IGBT, the gate voltage Output, and if it is a bipolar transistor, it outputs the base current). While the LED current becomes constant at I2, the output voltage of the AC-DC circuit 102 becomes higher than the LED voltage and fluctuates as shown in FIG. The voltage of the semiconductor element 104, that is, the drop voltage is the difference between the output voltage of the AC-DC circuit 102 and the LED voltage. From the above, it is possible to control the peak value of the LED current pulsation to a predetermined value, and it is possible to prevent an excessive current from flowing in the LED load 101 and the LED lighting device, and in turn prevent the shortening of their life. However, in this period, since the drop voltage is generated in the semiconductor element 104 as described above, the loss of the semiconductor element 104 is generated as a product of the drop voltage and I2.

ＬＥＤ電流が小さくなる期間では，制御回路１０６は第２動作を行い，半導体素子１０４をオン（スルー）状態にする。このオン状態とは，半導体素子１０４がスイッチング電源回路の素子として利用される場合のオン状態を意味する。制御回路１０６の具体的な動作としては，半導体素子１０４がＭＯＳＦＥＴやＩＧＢＴであれば，そのオン閾値電圧より十分高い電圧をゲートに印加すればよい。半導体素子１０４のドロップ電圧は略ゼロ，すなわち半導体素子１０４は短絡状態と見なせる。したがって，この期間では半導体素子１０４の損失は小さくなる。その一方，ＬＥＤ電流は図２のように脈動する。 During a period in which the LED current decreases, the control circuit 106 performs the second operation to turn on (through) the semiconductor element 104. The on state means the on state when the semiconductor element 104 is used as an element of the switching power supply circuit. As a specific operation of the control circuit 106, if the semiconductor element 104 is a MOSFET or IGBT, a voltage sufficiently higher than the on threshold voltage may be applied to the gate. The drop voltage of the semiconductor element 104 is substantially zero, that is, the semiconductor element 104 can be regarded as a short circuit state. Therefore, the loss of the semiconductor element 104 is small in this period. On the other hand, the LED current pulsates as shown in FIG.

以上のように，本発明の第１実施例では，交流電源周期の一部期間において制御回路１０６が第１動作を，残りの期間において第２動作を行う。これによって，従来（図３）と比べて同じ容量すなわち寸法のコンデンサ１０３に対してＬＥＤ電流の脈動をより小さくできる。言い換えれば，同じＬＥＤ電流の条件に対して，コンデンサ１０３を小容量化すなわち小型化できる。また，従来（特許文献１から考えられる構成）と比べて半導体素子１０４のドロップ電圧による損失を低減でき，ＬＥＤ点灯装置を高効率化できる。 As described above, in the first embodiment of the present invention, the control circuit 106 performs the first operation in part of the AC power supply cycle and performs the second operation in the remaining period. This makes it possible to reduce the pulsation of the LED current for a capacitor 103 of the same capacity or size as in the prior art (FIG. 3). In other words, for the same LED current condition, the capacitor 103 can be reduced in capacity, that is, miniaturized. Further, the loss due to the drop voltage of the semiconductor element 104 can be reduced as compared with the related art (the configuration considered from Patent Document 1), and the efficiency of the LED lighting device can be improved.

図２の動作タイミングチャートを実現するためには，第２設定値Ｉ２を適切に設定する必要がある。図２から分かるように，Ｉ２は，第１設定値Ｉ１より大きく設定される。また，図３の動作タイミングチャートを，特にＬＥＤ電流の脈動振幅ΔＩを実験または回路シミュレーションによって測定できるのであれば，Ｉ２は（Ｉ１＋ΔＩ）より小さく設定することが目安となる。すなわち，Ｉ２の設定範囲は，Ｉ１＜Ｉ２＜（Ｉ１＋ΔＩ）となる。
In order to realize the operation timing chart of FIG. 2, it is necessary to set the second set value I2 appropriately. As can be seen from FIG. 2, I2 is set larger than the first set value I1. In addition, if it is possible to measure the pulsation amplitude ΔI of the LED current particularly by experiment or circuit simulation, it is a guideline to set I2 smaller than (I1 + ΔI) in the operation timing chart of FIG. That is, the setting range of I2 is I1 <I2 <(I1 + ΔI).

＜ＡＣ−ＤＣ回路１０２の具体例＞
図４では，図１に示したＬＥＤ点灯装置について，ＡＣ−ＤＣ回路１０２及び制御回路１０６の構成をより具体的に示した。ＡＣ−ＤＣ回路１０２は，整流回路１０７と昇降圧チョッパ１０８を備える。これらの他に，ノイズフィルタやヒューズなどを備えていてもよい。図４では，電流検出手段１０５を抵抗１１６として構成した。抵抗１１６に発生する電圧が，ＬＥＤ電流及び半導体素子１０４に流れる電流を示す。 <Specific Example of AC-DC Circuit 102>
FIG. 4 more specifically shows the configuration of the AC-DC circuit 102 and the control circuit 106 in the LED lighting device shown in FIG. The AC-DC circuit 102 includes a rectifier circuit 107 and a buck-boost chopper 108. In addition to these, a noise filter or a fuse may be provided. In FIG. 4, the current detection unit 105 is configured as the resistor 116. The voltage generated in the resistor 116 indicates the LED current and the current flowing to the semiconductor element 104.

整流回路１０７の具体的構成として，ダイオードブリッジによる全波整流回路が考えられる。図４の昇降圧チョッパ１０８は，スイッチング素子であるＭＯＳＦＥＴ（１０９と１１０）とダイオード（１１１と１１２）を２個ずつ，さらにチョークコイル１１３を備えるＨブリッジ方式である。昇降圧チョッパ１０８は，力率改善回路として利用可能であり，また，名称の通り降圧も昇圧も可能であるため，他の方式と比べて幅広い入力電圧条件に対応できる。スイッチング素子として，ＭＯＳＦＥＴの他にバイポーラトランジスタやＩＧＢＴを用いてもよい。昇降圧チョッパ１０８の詳細な動作については説明を省略する。
As a specific configuration of the rectifier circuit 107, a full wave rectifier circuit with a diode bridge can be considered. The step-up / step-down chopper 108 in FIG. 4 is an H-bridge system including two switching element MOSFETs (109 and 110) and two diodes (111 and 112) and a choke coil 113. The step-up / step-down chopper 108 can be used as a power factor correction circuit, and as the name suggests it can be stepped down or stepped up, so that it can cope with a wider range of input voltage conditions than other methods. As a switching element, a bipolar transistor or IGBT may be used other than the MOSFET. The detailed operation of the step-up / step-down chopper 108 will not be described.

＜制御回路１０６の具体例＞
図２を用いて説明した動作を実現できれば，制御回路１０６の具体的な構成については問わない。ここでは，図４を用いてその一例について説明する。 <Specific Example of Control Circuit 106>
The specific configuration of the control circuit 106 is not limited as long as the operation described with reference to FIG. 2 can be realized. Here, an example will be described with reference to FIG.

制御回路１０６の電流設定値生成部は，第１設定値Ｉ１を生成する。図４のように，外部から入力される調光信号がある場合，調光信号にしたがってＩ１を可変する。 The current setting value generation unit of the control circuit 106 generates a first setting value I1. As shown in FIG. 4, when there is a dimming signal input from the outside, I1 is varied according to the dimming signal.

抵抗１１６によって検出されるＬＥＤ電流は，図２で示したように脈動，すなわちＡＣ成分を含む。制御回路の平均値演算部は，ＡＣ成分を除去して交流電源周期におけるＬＥＤ電流の平均値を計算する。 The LED current detected by the resistor 116 includes a pulsation, ie, an AC component as shown in FIG. An average value calculation unit of the control circuit removes an AC component to calculate an average value of LED currents in an AC power supply cycle.

Ｉ１と検出したＬＥＤ電流との誤差は，制御演算部に入力される。制御演算部は，例えばＰＩ（比例−積分）制御などの演算によって上記の誤差を増幅する，すなわちエラーアンプとして動作する。その一方，制御回路１０６は，整流回路１０７の直流出力電圧に当たる整流電圧を検出する。なお，整流電圧を検出する過程で，分圧，ローパスフィルタリングなどの処理を実施してもよい。検出した整流電圧は，乗算部にて上記の制御演算部の出力と乗算される。乗算の結果は，ＡＣ−ＤＣ回路１０２の電流設定値となり，その波形は全波整流された正弦波状になる。ＰＷＭ制御部は，ＡＣ−ＤＣ回路１０２のスイッチング素子やチョークコイルに流れる電流を上記の設定値にしたがって制御するように，ＡＣ−ＤＣ回路１０２の駆動信号を生成する。これらの部品に流れる電流の波形は，設定値と同様，全波整流された正弦波状となる。結果として，ＬＥＤ点灯装置に入力される電流波形は正弦波状となり，力率改善が実現される。以上の制御演算によって，ＬＥＤ電流の平均値をＩ１に制御し，かつ，入力電流波形を正弦波状にする力率改善動作が可能である。制御演算部とＰＷＭ制御部の詳細な動作については省略する。 The error between I1 and the detected LED current is input to the control calculation unit. The control operation unit amplifies the above error by an operation such as PI (proportional-integral) control, for example, and operates as an error amplifier. On the other hand, the control circuit 106 detects a rectified voltage corresponding to the DC output voltage of the rectifier circuit 107. In the process of detecting the rectified voltage, processing such as voltage division and low pass filtering may be performed. The detected rectified voltage is multiplied by the output of the control operation unit in the multiplication unit. The result of the multiplication becomes the current setting value of the AC-DC circuit 102, and the waveform becomes a full wave rectified sine wave. The PWM control unit generates a drive signal of the AC-DC circuit 102 so as to control the current flowing through the switching element and the choke coil of the AC-DC circuit 102 according to the above set value. The waveform of the current flowing to these parts is a full wave rectified sine wave as well as the set value. As a result, the current waveform input to the LED lighting device becomes sinusoidal and power factor improvement is realized. By the above control calculation, it is possible to control the average value of the LED current to I1 and to perform the power factor improvement operation to make the input current waveform sinusoidal. Detailed operations of the control calculation unit and the PWM control unit are omitted.

制御回路１０６のＩ２演算部は，Ｉ１をもとにドロッパ方式定電流回路の電流設定値である第２設定値Ｉ２を生成する。既に説明したように，Ｉ２はＩ１より大きい値に設定される。図４のように外部から入力される調光信号を利用する場合，Ｉ２演算部はＩ１の変更に合わせて適宜Ｉ２を変更する。調光信号を利用せず，Ｉ１を一定にする場合では，Ｉ２演算部を省略してもよい。 The I2 operation unit of the control circuit 106 generates a second set value I2 which is a current set value of the dropper type constant current circuit based on I1. As described above, I2 is set to a value larger than I1. As shown in FIG. 4, in the case of using a light control signal input from the outside, the I2 operation unit appropriately changes I2 in accordance with the change of I1. If the light adjustment signal is not used and I1 is made constant, the I2 operation unit may be omitted.

制御回路１０６の半導体素子制御部は，第１動作を行う，すなわち，半導体素子１０４をドロッパ方式定電流回路の素子として動作させるために，オペアンプ（演算増幅器）１１４を備える。図４には，オペアンプ１１４の動作電圧を生成する直流電源１１５を示した。直流電源１１５の生成方法については問わないが，検出した整流電圧を利用する方法が考えられる。直流電源１１５の電圧は，半導体素子１０４をオン（スルー）状態にするために十分な電圧とする。半導体素子１０４がＭＯＳＦＥＴやＩＧＢＴであれば，そのオン閾値電圧より十分高い電圧，例えば８Ｖ以上とすればよい。 The semiconductor element control unit of the control circuit 106 includes an operational amplifier (operational amplifier) 114 in order to perform the first operation, that is, to operate the semiconductor element 104 as an element of the dropper type constant current circuit. FIG. 4 shows a DC power supply 115 for generating an operating voltage of the operational amplifier 114. The method of generating the DC power supply 115 is not limited, but a method of using the detected rectified voltage can be considered. The voltage of the DC power supply 115 is a voltage sufficient to turn on (through) the semiconductor element 104. If the semiconductor element 104 is a MOSFET or IGBT, the voltage may be sufficiently higher than the on threshold voltage, for example, 8 V or more.

オペアンプ１１４のプラス入力端子には，ドロッパ方式定電流回路の電流設定値Ｉ２に対応する電圧が印加される。ＬＥＤ電流を検出する抵抗１１６の抵抗値をＲｓとすると，＋端子に印加する電圧を（Ｒｓ×Ｉ２）とすればよい。オペアンプ１１４のマイナス入力端子には，抵抗１１６に発生する電圧，すなわち，検出したＬＥＤ電流に対応する電圧が印加される。オペアンプ１１４の出力端子は，半導体素子１０４の制御端子，すなわち，半導体素子１０４がＭＯＳＦＥＴやＩＧＢＴであればそのゲート端子に，バイポーラトランジスタであればそのベース端子に接続される。図４では，抵抗１１７を介してゲート端子に接続する構成としたが，抵抗１１７は省略（短絡）してもよい。 A voltage corresponding to the current setting value I2 of the dropper constant current circuit is applied to the positive input terminal of the operational amplifier 114. Assuming that the resistance value of the resistor 116 for detecting the LED current is Rs, the voltage applied to the + terminal may be (Rs × I2). A voltage generated at the resistor 116, that is, a voltage corresponding to the detected LED current is applied to the negative input terminal of the operational amplifier 114. The output terminal of the operational amplifier 114 is connected to the control terminal of the semiconductor element 104, that is, to the gate terminal of the semiconductor element 104 if it is a MOSFET or IGBT, or to the base terminal if it is a bipolar transistor. In FIG. 4, the gate terminal is connected via the resistor 117, but the resistor 117 may be omitted (short circuited).

オペアンプ１１４，半導体素子１０４，抵抗１１６によって構成されるドロッパ方式定電流回路によって，ＬＥＤ電流はＩ２より大きくなることはない。図２でも説明したように，交流電源周期のうちＬＥＤ電流が大きくなる期間でも，ＬＥＤ電流をＩ２に抑制できる。この動作は，制御回路１０６の第１動作に当たる。一方，ＬＥＤ電流がＩ２より小さくなる期間，すなわち，ドロッパ回路による電流制限が不要となる期間では，オペアンプ１１４の出力が飽和する。このとき，直流電源１１５の電圧が半導体素子１０４のゲートに印加され，半導体素子１０４はオン状態となる。すなわち，制御回路１０６は第２動作を行う。 Due to the dropper type constant current circuit constituted by the operational amplifier 114, the semiconductor element 104, and the resistor 116, the LED current never exceeds I2. As described with reference to FIG. 2, the LED current can be suppressed to I2 even in a period in which the LED current increases in the AC power supply cycle. This operation corresponds to the first operation of the control circuit 106. On the other hand, the output of the operational amplifier 114 is saturated in a period in which the LED current is smaller than I2, that is, in a period in which the current restriction by the dropper circuit is not required. At this time, the voltage of the DC power supply 115 is applied to the gate of the semiconductor element 104, and the semiconductor element 104 is turned on. That is, the control circuit 106 performs the second operation.

以上から，制御回路１０６は，交流電源１００の位相やＬＥＤ点灯装置の動作状態に応じて第１動作と第２動作を切り替えることができる。これによって，制御目的であるＬＥＤ電流の平均値を制御すること，ＬＥＤ電流のピーク値を制限すること，力率改善動作をすることの３点を実現できる。 As described above, the control circuit 106 can switch between the first operation and the second operation according to the phase of the AC power supply 100 and the operating state of the LED lighting device. In this way, it is possible to realize three points of controlling the average value of the LED current which is the control purpose, limiting the peak value of the LED current, and performing the power factor improvement operation.

以上で説明した制御回路１０６の各構成要素の実現方法は問わないが，簡単なアナログ回路によって実現可能である。また，制御回路１０６の実現においてマイクロコンピュータ（以下，マイコンと記す），ＤＳＰ（ＤｉｇｉｔａｌＳｉｇｎａｌＰｒｏｃｅｓｓｏｒ），ＩＣといった制御デバイスを利用する場合，これらの全部または一部をこれらの制御デバイスに実装してもよい。
There is no limitation on how to realize each component of the control circuit 106 described above, but it can be realized by a simple analog circuit. When using control devices such as a microcomputer (hereinafter referred to as a microcomputer), DSP (Digital Signal Processor), or IC in the realization of the control circuit 106, all or part of these may be mounted on these control devices. Good.

＜ＡＣ−ＤＣ回路１０２と半導体素子１０４の別例＞
図５は，ＡＣ−ＤＣ回路１０２としてフライバックコンバータ１１８を，半導体素子１０４としてバイポーラトランジスタを用いる構成である。フライバックコンバータ１１８は，トランス１１９を備え，その１次側にはスイッチング素子であるＭＯＳＦＥＴ１２０を，２次側にはダイオード１２１をそれぞれ備える。トランス１１９の１次巻線には，コンデンサ１２２，抵抗１２３，ダイオード１２４から成るスナバ回路が接続される。フライバックコンバータ１１８は，交流電源１００とＬＥＤ負荷１０１の間で絶縁が必要な場合に利用可能であり，昇降圧チョッパ１０８と同様に降圧も昇圧も可能であるため，幅広い入力電圧条件に対応できる。 <Another Example of AC-DC Circuit 102 and Semiconductor Element 104>
FIG. 5 shows a configuration in which a flyback converter 118 is used as the AC-DC circuit 102 and a bipolar transistor is used as the semiconductor element 104. The flyback converter 118 includes a transformer 119, and includes a MOSFET 120 as a switching element on its primary side and a diode 121 on its secondary side. The primary winding of the transformer 119 is connected to a snubber circuit comprising a capacitor 122, a resistor 123 and a diode 124. The flyback converter 118 can be used when insulation is required between the AC power supply 100 and the LED load 101, and can be stepped down or stepped up similarly to the buck-boost chopper 108, so that a wide range of input voltage conditions can be accommodated. .

制御回路１０６は第２動作において，バイポーラトランジスタがオン状態となるのに十分なベース電流を供給すればよい。図４に示した制御回路１０６の構成を適用し，直流電源１１５の電圧及び抵抗１１７を調整することでこれを実現できる。 In the second operation, the control circuit 106 may supply sufficient base current to turn on the bipolar transistor. This can be realized by applying the configuration of the control circuit 106 shown in FIG. 4 and adjusting the voltage of the DC power supply 115 and the resistor 117.

図６は，ＡＣ−ＤＣ回路１０２として昇圧チョッパ１２５を用いる構成である。昇圧チョッパ１２５は，スイッチング素子であるＭＯＳＦＥＴ１２６，ダイオード１２７，チョークコイル１２８を備え，図４の昇降圧チョッパ１０８より少ない部品数で構成できる。 FIG. 6 shows a configuration in which a boost chopper 125 is used as the AC-DC circuit 102. The step-up chopper 125 includes a MOSFET 126 as a switching element, a diode 127, and a choke coil 128, and can be configured with a smaller number of parts than the step-up / step-down chopper 108 of FIG.

しかし，昇圧チョッパ１２５は名称の通り昇圧しかできないため，昇圧チョッパ１２５で安定に力率改善動作を行うためには，ＬＥＤ電圧を交流電源１００のピーク電圧より高く設定する必要がある。例えば，交流電源１００の電圧実効値が２００Ｖａｃであるとき，そのピーク値は約２８３Ｖであり，ＬＥＤ電圧の設定例として約３００Ｖが考えられる。ＬＥＤ電圧は，ＬＥＤ負荷１０１におけるＬＥＤの直列接続数によって調整可能である。 However, since the step-up chopper 125 can only perform the step-up operation as the name suggests, it is necessary to set the LED voltage higher than the peak voltage of the AC power supply 100 in order to perform the power factor correction operation stably by the step-up chopper 125. For example, when the voltage effective value of the AC power supply 100 is 200 Vac, its peak value is about 283 V, and about 300 V can be considered as a setting example of the LED voltage. The LED voltage can be adjusted by the number of series connected LEDs in the LED load 101.

なお，以上の別例は，本発明の全ての実施例に適用できる。
Note that the other examples described above can be applied to all the embodiments of the present invention.

図７は，本発明の実施例２における動作タイミングチャートであり，図８は，これを実現する制御回路１０６の具体例である。実施例２において，制御回路１０６以外の構成については，実施例１で説明した構成をそのまま適用できる。図７と図２を比較すると分かるように，実施例１とほぼ同様の動作タイミングチャートとなる。そのため，図７の詳細な説明については省略する。 FIG. 7 is an operation timing chart according to the second embodiment of the present invention, and FIG. 8 is a specific example of the control circuit 106 for realizing this. In the second embodiment, the configuration described in the first embodiment can be applied as it is to the configuration other than the control circuit 106. As can be seen by comparing FIGS. 7 and 2, the operation timing chart is almost the same as that of the first embodiment. Therefore, the detailed description of FIG. 7 is omitted.

図８の制御回路１０６は，検出されたＬＥＤ電流の最小値検出部を備え，交流電源周期におけるＬＥＤ電流の最小値を検出する。この最小値検出は，マイコンやＤＳＰといった制御デバイスを用いて簡単に実現できる。制御回路１０６は，ＬＥＤ電流の最小値を所定の第３設定値（Ｉ３）に制御するようにＡＣ−ＤＣ回路１０２の駆動信号を生成する。すなわち，実施例１ではＬＥＤ電流の平均値を制御することに対して，実施例２ではＬＥＤ電流の最小値を制御する。制御回路１０６の第１動作と合わせて，ＬＥＤ電流の最大値をＩ２に，最小値をＩ３にそれぞれ制御可能であり，脈動振幅を実施例１より厳密に制御できる。 The control circuit 106 of FIG. 8 includes a minimum value detection unit for the detected LED current, and detects the minimum value of the LED current in the AC power supply cycle. This minimum value detection can be easily realized using a control device such as a microcomputer or DSP. The control circuit 106 generates a drive signal of the AC-DC circuit 102 so as to control the minimum value of the LED current to a predetermined third set value (I3). That is, while the embodiment 1 controls the average value of the LED current, the embodiment 2 controls the minimum value of the LED current. In combination with the first operation of the control circuit 106, the maximum value of the LED current can be controlled to I2, and the minimum value can be controlled to I3, and the pulsation amplitude can be controlled more precisely than in the first embodiment.

第３設定値Ｉ３は，Ｉ２より小さく設定されることはもちろん，実施例１で説明したＬＥＤ電流の平均値に関する第１設定値Ｉ１より小さく設定される。実施例２の制御動作は，以下で説明する他の実施例にも適用できる。
The third set value I3 is set smaller than I2, and is set smaller than the first set value I1 related to the average value of the LED current described in the first embodiment. The control operation of the second embodiment can be applied to the other embodiments described below.

図９は，本発明の実施例３における動作タイミングチャートである。図９では，制御回路１０６が調光信号にしたがってＬＥＤ電流の平均値（上記の第１設定値Ｉ１）を可変することを前提として，（ａ）調光レベル（Ｉ１）が所定の閾値より大きい場合，（ｂ）調光レベル（Ｉ１）が同閾値より小さい場合について示した。図９（ａ）の調光レベルが大きい場合，制御回路１０６の動作，及び，タイミングチャートは，図２に示した実施例１と同様である。一方，図９（ｂ）の調光レベルが小さい場合，制御回路１０６は第１動作のみを行う。このとき，ＬＥＤ電流は上記の第２設定値（図９（ａ）のＩ２とは異なる値であるため，図９（ｂ）では区別するためにＩ２’と記した）に従って一定に制御される。図９（ｂ）に記載した通り，Ｉ２’はＩ１と同値に設定される。ＡＣ−ＤＣ回路１０２が力率改善動作をするため，その出力電圧は交流電源（の２倍の）周波数で脈動するが，交流電源周期に渡ってＬＥＤ電圧より高くなるように制御される。 FIG. 9 is an operation timing chart in the third embodiment of the present invention. In FIG. 9, assuming that the control circuit 106 varies the average value of the LED current (the first set value I1 above) according to the dimming signal, (a) the dimming level (I1) is larger than a predetermined threshold value In the case (b), the dimming level (I1) is smaller than the same threshold. When the dimming level in FIG. 9A is large, the operation of the control circuit 106 and the timing chart are the same as in the first embodiment shown in FIG. On the other hand, when the dimming level in FIG. 9B is small, the control circuit 106 performs only the first operation. At this time, the LED current is constantly controlled according to the above-mentioned second set value (denoted as I2 'for distinction in FIG. 9B because it is a value different from I2 in FIG. 9A) . As described in FIG. 9 (b), I2 'is set to the same value as I1. In order for the AC-DC circuit 102 to perform a power factor correction operation, its output voltage pulsates at (the double of) the frequency of the AC power supply, but is controlled to be higher than the LED voltage over the AC power supply cycle.

図１０は，図９の動作を実現するＬＥＤ点灯装置，特に制御回路１０６の具体例である。図１０と図４を比較すると分かるように，制御回路１０６以外の構成については，図４の実施例１と同様である。図１０のように，制御回路１０６は，ＬＥＤ電流の平均値をＩ１に制御する構成と，ＡＣ−ＤＣ回路１０２の出力電圧を所定の第４設定値（Ｖ１）に制御する構成の両方を備え，調光レベルによっていずれかの制御構成を選択する。図９の動作を実現するためには，（ａ）調光レベルが所定の値より大きい場合，ＬＥＤ電流の制御を選択し，（ｂ）調光レベルが同値より小さい場合，ＡＣ−ＤＣ回路１０２の出力電圧の制御を選択すればよい。２通りの制御構成のうちＬＥＤ電流の平均値を制御する構成については，実施例１（図４）と同様であるため，詳細な説明を省略する。なお，図１０では，（ｂ）調光レベルが所定の値より小さい場合について示した。 FIG. 10 is a specific example of the LED lighting device for realizing the operation of FIG. 9, particularly the control circuit 106. As can be seen by comparing FIG. 10 with FIG. 4, the configuration other than the control circuit 106 is the same as that of the first embodiment of FIG. As shown in FIG. 10, the control circuit 106 has both a configuration for controlling the average value of the LED current to I1 and a configuration for controlling the output voltage of the AC-DC circuit 102 to a predetermined fourth set value (V1). , Select one of the control configurations according to the dimming level. In order to realize the operation of FIG. 9, (a) control of the LED current is selected when the dimming level is larger than a predetermined value, and (b) the AC-DC circuit 102 is selected when the dimming level is smaller than the same value. It is sufficient to select control of the output voltage of Of the two control configurations, the configuration for controlling the average value of the LED current is the same as that of the first embodiment (FIG. 4), and thus the detailed description will be omitted. FIG. 10 shows the case where (b) the dimming level is smaller than a predetermined value.

制御回路１０６の設定値生成部は，Ｉ１の他にＶ１を生成する。既に説明した通り，Ｖ１はＬＥＤ電圧より高い値に設定される。また，制御回路１０６は，ＡＣ−ＤＣ回路１０２の出力電圧を検出する。制御切替部は，Ｖ１と検出されたＡＣ−ＤＣ回路１０２の出力電圧の誤差，または，Ｉ１と検出されたＬＥＤ電流の誤差のうち，どちらを制御演算部に入力するか選択する。また，制御切替部は，どちらの制御を行うかによって，制御演算部のゲインを変更する機能を備えていてもよい。なお，ＡＣ−ＤＣ回路１０２の出力電圧を直接検出してこれを制御する構成の他に，半導体素子１０４の電圧を検出し，これを所定の値に制御する構成もある。 The set value generation unit of the control circuit 106 generates V1 in addition to I1. As described above, V1 is set to a value higher than the LED voltage. The control circuit 106 also detects the output voltage of the AC-DC circuit 102. The control switching unit selects which of an error of the output voltage of the AC-DC circuit 102 detected as V1 or an error of the LED current detected as I1 is to be input to the control operation unit. Also, the control switching unit may have a function of changing the gain of the control calculation unit depending on which control is performed. In addition to the configuration in which the output voltage of the AC-DC circuit 102 is directly detected and controlled, there is also a configuration in which the voltage of the semiconductor element 104 is detected and this is controlled to a predetermined value.

制御回路１０６のＩ２演算部は，Ｉ１に基づいてＩ２を生成する。調光レベルが所定の閾値より大きい場合，すなわち，図９（ａ）の場合については，実施例１と同様であるため説明を省略する。調光レベルが同閾値より小さい場合，すなわち，図９（ｂ）の場合については，Ｉ２’をＩ１と同値に設定すればよい。上記の通りＡＣ−ＤＣ回路１０２の出力電圧がＬＥＤ電圧より常に高く制御されれば，半導体素子１０４は自動的にドロッパ方式定電流回路の素子として動作し，ＬＥＤ電流はＩ２’で一定に制御される。 The I2 operation unit of the control circuit 106 generates I2 based on I1. The case where the dimming level is larger than the predetermined threshold value, that is, the case of FIG. If the dimming level is smaller than the same threshold, that is, in the case of FIG. 9B, I2 'may be set to the same value as I1. As described above, if the output voltage of the AC-DC circuit 102 is controlled to be always higher than the LED voltage, the semiconductor element 104 automatically operates as an element of the dropper type constant current circuit, and the LED current is controlled to be constant by I2 '. Ru.

調光レベルが小さい場合，ＬＥＤ電流が小さいため，半導体素子１０４をドロッパ方式定電流回路で動作させたときの損失も小さくなる。図９（ｂ）に示した動作によって，半導体素子１０４の損失低減と比べてＬＥＤ電流の脈動低減を優先し，ＬＥＤ電流を一定値に制御できる。 When the dimming level is small, the LED current is small, so that the loss when the semiconductor element 104 is operated by the dropper type constant current circuit is also small. By the operation shown in FIG. 9B, it is possible to control the LED current to a constant value by prioritizing the pulsation reduction of the LED current compared to the loss reduction of the semiconductor element 104.

図１１は，本発明の実施例３における動作タイミングチャートの別例である。図１１では，（ａ）調光レベルが所定の閾値より大きい場合，制御回路１０６は第２動作のみを行う。これを実現するためには，図１０の制御回路１０６において，Ｉ２をＩ１に比べて十分大きく設定すればよい。なお，（ｂ）調光レベルが同閾値より大きい場合については，図９（ｂ）の動作と同様である。 FIG. 11 is another example of the operation timing chart in the third embodiment of the present invention. In FIG. 11, (a) when the dimming level is larger than the predetermined threshold, the control circuit 106 performs only the second operation. In order to realize this, in the control circuit 106 of FIG. 10, I2 may be set sufficiently larger than I1. The case (b) where the dimming level is larger than the threshold is the same as the operation of FIG. 9 (b).

調光レベルが大きい場合，ＬＥＤ電流が大きいため，半導体素子１０４をドロッパ方式定電流回路で動作させたときの損失も大きくなる。図１１（ａ）の動作によって，ＬＥＤ電流の脈動低減と比べて半導体素子１０４の損失低減を優先し，半導体素子１０４のドロップ電圧を略ゼロにして損失を低減できる。 When the dimming level is large, the loss when the semiconductor element 104 is operated by the dropper type constant current circuit is also large because the LED current is large. By the operation of FIG. 11A, it is possible to prioritize the reduction of the loss of the semiconductor element 104 compared to the reduction of the pulsation of the LED current, reduce the drop voltage of the semiconductor element 104 to substantially zero, and reduce the loss.

以上から，実施例３では，制御回路１０６は調光レベル（Ｉ１）に応じて第１動作と第２動作を切り替えると言うこともできる。
From the above, in the third embodiment, it can be said that the control circuit 106 switches the first operation and the second operation according to the dimming level (I1).

図１２は，本発明の実施例４におけるＬＥＤ点灯装置のブロック図であり，図１３は動作タイミングチャートである。図１２のように，ＡＣ−ＤＣ回路１０２の出力を平滑するコンデンサ１０３（第１コンデンサ）とは別に，ＬＥＤ負荷１０１と並列にコンデンサ１２９（第２コンデンサ）を接続する。これによって，図１３のようにＬＥＤ電流の脈動をより低減できる。また，ＬＥＤ電流に含まれる高周波成分を低減し，脈動波形を正弦波に近づけることができる。なお，実施例４の構成は，本発明の全ての実施例に適用できる。

FIG. 12 is a block diagram of the LED lighting device in Embodiment 4 of the present invention, and FIG. 13 is an operation timing chart. As shown in FIG. 12, a capacitor 129 (second capacitor) is connected in parallel with the LED load 101 separately from the capacitor 103 (first capacitor) for smoothing the output of the AC-DC circuit 102. By this, the pulsation of the LED current can be further reduced as shown in FIG. Moreover, the high frequency component contained in LED current can be reduced, and a pulsation waveform can be closely approached to a sine wave. The configuration of the fourth embodiment can be applied to all the embodiments of the present invention.

１００交流電源
１０１ＬＥＤ負荷
１０２ＡＣ−ＤＣ回路
１０３コンデンサ（１２２，１２９も同様）
１０４半導体素子
１０５電流検出手段
１０６制御回路
１０７整流回路
１０８Ｈブリッジ方式昇降圧チョッパ
１０９ＭＯＳＦＥＴ（１１０，１２０，１２６も同様）
１１１ダイオード（１１２，１２１，１２４，１２７も同様）
１１３チョークコイル（１２８も同様）
１１４オペアンプ
１１５直流電源
１１６抵抗（１１７，１２３も同様）
１１８フライバックコンバータ
１１９トランス
１２５昇圧チョッパ 100 AC power supply 101 LED load 102 AC-DC circuit 103 capacitor (same as 122, 129)
104 semiconductor element 105 current detection means 106 control circuit 107 rectification circuit 108 H bridge type buck-boost chopper 109 MOSFET (same as 110, 120, 126)
111 diodes (the same applies to 112, 121, 124 and 127)
113 choke coil (same for 128)
114 Op amp 115 DC power supply 116 Resistance (same as 117, 123)
118 flyback converter 119 transformer 125 boost chopper

Claims

AC-DC circuit for rectifying AC power supply voltage, first capacitor for smoothing output voltage of the AC-DC circuit, LED load connected between output terminals of the AC-DC circuit, semiconductor element and current detection means And a control circuit for controlling the AC-DC circuit and the semiconductor element,
The control circuit performs a first operation using the semiconductor element as an element for a dropper type (linear regulator type) constant current circuit, and controls an output by the AC-DC circuit with the semiconductor element turned on (through) An LED lighting device characterized in that two operations of a second operation are performed.

In the LED lighting device according to claim 1,
The AC-DC circuit controls the average value of the current flowing through the LED load to a predetermined first setting value, and the control circuit sets the current setting value of the dropper constant current circuit in the first operation to a predetermined value. An LED lighting device set to a second set value, wherein the second set value is larger than the first set value.

In the LED lighting device according to claim 1,
The AC-DC circuit controls the minimum value of the current flowing through the LED load to a predetermined third setting value, and the control circuit sets the current setting value of the dropper constant current circuit in the first operation to a predetermined value. An LED lighting device set to a second set value, wherein the second set value is larger than the third set value.

The LED lighting device according to any one of claims 1 to 3,
The LED lighting device, wherein the control circuit performs the first operation in a part of a period of the AC power supply and performs the second operation in the remaining period.

The LED lighting device according to any one of claims 1 to 4,
The control circuit has a function of changing the average value of the current flowing through the LED load, and performs only the first operation when controlling the average value of the current flowing through the LED load smaller than a predetermined threshold value. An LED lighting device comprising: controlling an output voltage of an AC-DC circuit to a predetermined fourth set value, wherein the fourth set value is higher than a voltage of the LED load.

In the LED lighting device according to claim 5,
The LED lighting device, wherein the control circuit performs only the second operation when controlling the average value of the current flowing to the LED load to be larger than the predetermined threshold value.

The LED lighting device according to any one of claims 1 to 6,
The AC-DC circuit includes a rectifier circuit that rectifies the AC power supply voltage to generate a rectified voltage, and a buck-boost chopper that converts the rectified voltage to supply the LED load, and the control circuit An LED lighting device characterized by operating a pressure chopper as a power factor correction (PFC) circuit.

The LED lighting device according to any one of claims 1 to 6,
The AC-DC circuit includes a rectifier circuit that rectifies the AC power supply voltage to generate a rectified voltage, and a boost chopper that converts the rectified voltage to supply the LED load, and the control circuit is configured to boost the chopper A power factor correction (PFC) circuit, wherein a voltage of the LED load is set higher than a peak value of a voltage of the AC power supply.

The LED lighting device according to any one of claims 1 to 8,
An LED lighting device comprising: a second capacitor connected in parallel to the LED load.

In the LED lighting device according to claim 2 or 3 ,
The current detection means is a resistor that converts the current flowing through the semiconductor element into a voltage and detects it.
The control circuit includes an operational amplifier (operational amplifier) for performing the first operation, a voltage corresponding to the second set value is input to the positive input terminal of the operational amplifier, and the negative input terminal of the operational amplifier The voltage generated at the resistor is input, the output terminal of the operational amplifier is connected to the control terminal of the semiconductor device, and the voltage of the DC power supply for operating the operational amplifier turns the semiconductor device on. An LED lighting device characterized in that the voltage is set to a sufficient voltage.