JP2005033853A - Loading driver and portable apparatus - Google Patents

Loading driver and portable apparatus

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Publication number
JP2005033853A
JP2005033853A JP2003192784A JP2003192784A JP2005033853A JP 2005033853 A JP2005033853 A JP 2005033853A JP 2003192784 A JP2003192784 A JP 2003192784A JP 2003192784 A JP2003192784 A JP 2003192784A JP 2005033853 A JP2005033853 A JP 2005033853A
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current
dc
voltage
load
lt
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JP2003192784A
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JP3755770B2 (en )
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Teiichi Murakami
禎一 村上
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Rohm Co Ltd
ローム株式会社
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    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02BCLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
    • Y02B20/00Energy efficient lighting technologies
    • Y02B20/30Semiconductor lamps, e.g. solid state lamps [SSL] light emitting diodes [LED] or organic LED [OLED]
    • Y02B20/34Inorganic LEDs
    • Y02B20/341Specially adapted circuits
    • Y02B20/346Switching regulators
    • Y02B20/347Switching regulators configured as a current source

Abstract

<P>PROBLEM TO BE SOLVED: To vary a load current for driving a load within a specified range using a DC/DC conversion power supply circuit and to drive a load efficiently by avoiding increase in loss incident to increase in the load current. <P>SOLUTION: A load 10, e.g. an LED, and a constant current source I1 are connected in series between the output voltage Vo1 point of a DC/DC conversion power supply circuit 100 and the ground. Current Io of the constant current source can be regulated and the DC/DC conversion power supply circuit controls the output voltage such that the voltage drop of the constant current source, i.e. a detection voltage Vdet, becomes equal to a reference voltage Vref. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【0001】 [0001]
【発明の属する技術分野】 BACKGROUND OF THE INVENTION
本発明は、直流−直流変換型の電源回路を用いて、電源電圧から変換された出力電圧により負荷を駆動する負荷駆動装置及びそれを用いた携帯機器に関する。 The present invention, DC - using the power circuit of the DC converter type, a portable device using the load driving device and it drives the load by the conversion output voltage from the power supply voltage.
【0002】 [0002]
【従来の技術】 BACKGROUND OF THE INVENTION
従来から、電源電圧と異なる電圧を発生する直流−直流変換型の電源回路を用いてLEDなどの負荷を駆動する負荷駆動装置が多く用いられている。 Conventionally, a direct current for generating a supply voltage different from the voltage - current conversion type load driving device for driving a load such as an LED with a power supply circuit is often used. この負荷駆動装置は、それを駆動するための電源回路から所定の出力電圧、出力電流を発生させるために、入力電圧または負荷に印加される負荷電圧や負荷に流れる負荷電流を検出して、電源回路の制御回路に帰還させる(特許文献1参照)。 The load driving apparatus, predetermined output voltage from the power supply circuit for driving it, in order to generate an output current, by detecting the load current flowing to the load applied voltage and the load to the input voltage or load, the power supply is fed back to the control circuit of the circuit (see Patent Document 1).
【0003】 [0003]
この従来の駆動装置では、制御電圧は入力電圧や負荷電圧を高抵抗で分圧して検出される。 This conventional driving device, the control voltage is detected by dividing the input voltage and the load voltage at a high resistance. また、負荷電流は負荷に直列に接続された抵抗器の電圧降下によって検出される。 The load current is detected by a voltage drop across the resistor connected in series with the load. この制御電圧や負荷電流を基準値と比較して電源回路からの出力電圧や出力電流を所定値に制御している。 Thereby controlling the output voltage and the output current from the power supply circuit to a predetermined value the control voltage and the load current is compared with a reference value.
【0004】 [0004]
【特許文献1】 [Patent Document 1]
特開2001−313423号公報【0005】 Japanese Unexamined Patent Publication No. 2001-313423 Publication [0005]
【発明が解決しようとする課題】 [Problems that the Invention is to Solve
携帯電話などの携帯型電子機器(携帯機器)においては、負荷を駆動するための負荷電流を、その負荷が設けられる電子機器側の使用上の要請によって、ある範囲内で増加させたり或いは減少させたりする場合がある。 In portable electronic devices such as cellular phones (portable device) is a load current for driving a load, the load at the request of the use of electronic devices side provided is allowed to or reduced or increased within a certain range there is a case to be or. 例えば、負荷が、発光素子(発光ダイオード等)である場合に、その発光量を任意の値に調整する場合などが考えられる。 For example, the load is, when a light-emitting element (light-emitting diode, etc.), can be considered a case of adjusting the amount of light emission to an arbitrary value.
【0006】 [0006]
このような場合に、負荷と直列に負荷電流検出用抵抗が挿入されていると、負荷電流の増加に応じて、電流検出用抵抗による損失が増加する。 In such a case, if the load in series with the load current detecting resistor is inserted, in accordance with an increase in load current, the loss due to the current detection resistor increases. したがって、電源回路や負荷を含む電子機器の全体としての効率が、大電流時(即ち、重負荷時)に低下してしまう問題があった。 Thus, overall efficiency of the electronic apparatus including a power supply circuit and a load, when a large current (i.e., heavy load) there is a problem that deteriorates the.
【0007】 [0007]
そこで、本発明は、電源電圧を変換して負荷に供給する、直流−直流変換型電源回路等の出力回路を用いて、負荷を駆動する負荷電流を所定範囲に変化させるとともに、負荷電流の増加に伴う損失の増大を避けて効率よく負荷を駆動することができる負荷駆動装置、及びそれを用いた携帯機器を提供することを目的とする。 Accordingly, the present invention is supplied to a load by converting a power supply voltage, a DC - using an output circuit such as the DC conversion type power supply circuit, together with changing the load current for driving a load in a predetermined range, an increase in the load current the increase in loss due to avoid the load driving apparatus capable of driving efficiently load, and aims to provide a portable apparatus using the same.
【0008】 [0008]
【課題を解決するための手段】 In order to solve the problems]
請求項1の負荷駆動装置は、電源電圧を変換して所定の出力電圧として負荷に供給する出力回路と、前記負荷に直列に接続されて調整可能な定電流を流す定電流源とを備え、前記出力回路は、前記負荷と前記定電流源との接続点の電圧が一定電圧になるように前記所定の出力電圧を制御することを特徴とする。 Load driving apparatus according to claim 1, comprising an output circuit for supplying to a load as a predetermined output voltage by converting a power supply voltage, and a constant current source for supplying an adjustable constant current is connected in series with the load, the output circuit is characterized in that the voltage at the node between the constant current source and the load to control the predetermined output voltage to be constant voltage.
【0009】 [0009]
請求項2の負荷駆動装置は、請求項1記載の負荷駆動装置において、前記定電流源は、電流可変型の定電流回路と、この定電流回路と直列に接続されたカレントミラー用入力側トランジスタと、このカレントミラー用入力側トランジスタと同じ制御入力が与えられるカレントミラー用出力側トランジスタとを含んでカレントミラー回路が構成されており、前記カレントミラー用出力側トランジスタに前記調整可能な定電流が流されることを特徴とする。 Load driving apparatus according to claim 2, in the load driving device according to claim 1, wherein the constant current source is a current-variable and the constant current circuit, constant current circuit connected in series with the input-side transistor current mirror When is configured by the current mirror circuit and a same control input the output side transistor current mirror is given this current mirror input side transistor, wherein the adjustable constant current to said output side transistor current mirror characterized in that it is flowed.
【0010】 [0010]
請求項3の負荷駆動装置は、請求項2記載の負荷駆動装置において、前記外部負荷は、少なくとも1つの発光ダイオードを含む発光ダイオード群であることを特徴とする。 Load driving apparatus according to claim 3, in the load driving device according to claim 2, wherein the external load, characterized in that it is a light emitting diode group including at least one light emitting diode.
【0011】 [0011]
請求項4の負荷駆動装置は、請求項2記載の負荷駆動装置において、前記一定電圧は、前記カレントミラー用出力側トランジスタの飽和電圧より高い電圧であることを特徴とする。 Load driving apparatus according to claim 4, in the load driving device according to claim 2, wherein the constant voltage, wherein said a voltage higher than the saturation voltage of the output-side transistor current mirror.
【0012】 [0012]
請求項5の負荷駆動装置は、請求項1乃至4記載の負荷駆動装置において、前記出力回路は、コイルと、このコイルへの通電をスイッチングするスイッチと、前記コイルと前記スイッチとの接続点と出力端子との間に設けられた整流素子とを有するスイッチング電源回路であることを特徴とする。 Load driving apparatus according to claim 5, in the load driving device according to claim 1 to 4, wherein said output circuit includes a coil, a switch for switching the current supply to the coil, the connection point between the coil switch characterized in that it is a switching power supply circuit having a rectifying element provided between an output terminal.
【0013】 [0013]
請求項6の負荷駆動装置は、請求項5記載の負荷駆動装置において、前記スイッチング電源回路は、さらに、前記整流素子の出力電圧点側に接続された平滑回路と、前記負荷と前記定電流源との接続点の電圧が基準電圧に等しくなるように前記スイッチのオンオフスイッチングを行う制御回路と、を有することを特徴とする。 Load driving apparatus according to claim 6, in the load driving device according to claim 5, wherein the switching power supply circuit further includes a smoothing circuit connected to the output voltage point side of the rectifying element, the constant current source and the load and having a control circuit for the voltage at node performs on-off switching of the switch to be equal to the reference voltage with.
【0014】 [0014]
請求項7の負荷駆動装置は、請求項1記載の負荷駆動装置において、前記負荷及び前記定電流源が複数であり、前記複数の負荷に前記複数の定電流源がそれぞれ直列に接続されてそれぞれ調整可能な定電流を流すとともに、前記複数の負荷と前記複数の定電流源との各接続点の電圧のうちの最も低い電圧が一定電圧になるように前記所定の出力電圧を制御することを特徴とする。 Load driving apparatus according to claim 7, in the load driving device according to claim 1, wherein the load and the a constant current source is more, each of the plurality of constant current source to the plurality of loads are connected in series with flow adjustable constant current, that the lowest voltage among the voltages of the connection point between the plurality of constant current source and the plurality of loads to control the predetermined output voltage to be constant voltage and features.
【0015】 [0015]
請求項8の負荷駆動装置は、請求項1乃至7記載の負荷駆動装置を用いていることを特徴とする携帯機器。 Load driving apparatus according to claim 8, the portable device being characterized in that by using the load driving device according to claim 1 to 7, wherein.
【0016】 [0016]
【発明の実施の形態】 DETAILED DESCRIPTION OF THE INVENTION
以下、本発明の負荷駆動装置の実施の形態について、図を参照して説明する。 Hereinafter, an embodiment of a load driving device of the present invention will be described with reference to FIG. 図1は、本発明の第1の実施の形態に係る負荷駆動装置の構成を示す図である。 Figure 1 is a diagram showing a configuration of a load driving device according to a first embodiment of the present invention.
【0017】 [0017]
図1において、出力回路であるスイッチング電源回路100は、入力される電源電圧Vccを昇圧して、昇圧された出力電圧Vo1を出力する昇圧型の電源回路である。 In Figure 1, the switching power supply circuit 100 is an output circuit boosts the power supply voltage Vcc is input, a power supply circuit of the step-up type that outputs the boosted output voltage Vo1.
【0018】 [0018]
電源電圧Vccとグランド間にコイルL1とN型MOSトランジスタであるスイッチQ1が直列に接続される。 Switch Q1 is a coil L1 and N-type MOS transistor are connected in series between supply voltage Vcc and the ground. その直列接続点Aから、整流用ダイオードD1と平滑用コンデンサC1とにより、直列接続点Aの電圧が整流し平滑されて、出力電圧Vo1として出力される。 From the series connection point A, by a rectifying diode D1 and smoothing capacitor C1, the voltage of the series connection point A is rectified and is smoothed and outputted as an output voltage Vo1. なお、電圧は、特に断らない場合には、グランドに対する電位である。 The voltage, if not otherwise specified is the potential for ground.
【0019】 [0019]
出力電圧Vo1点(P1)とグランドとの間に、外部負荷10と定電流源I1とが直列に接続される。 Between the output voltage Vo1 points (P1) and the ground, and the external load 10 and the constant current source I1 is connected in series. 外部負荷10は、動作させるべき点が流れる電流で決まる負荷であり、外部負荷10には定電流源I1で設定された所定の駆動電流Ioが流れる。 External load 10 is a load determined by the current point to be operated flows, flows a predetermined drive current Io is set by the constant current source I1 to the external load 10. そして、定電流源I1の一端P2に生じる電圧が検出電圧Vdetとなる。 Then, voltage is the detection voltage Vdet generated at one end P2 of the constant current source I1.
【0020】 [0020]
制御回路Contは、検出電圧Vdetと基準電圧源B1からの基準電圧Vrefとが入力され、検出電圧Vdetが基準電圧Vrefに等しくなるように、スイッチQ1をスイッチング制御するためのスイッチング信号を発生する。 The control circuit Cont is fed with the reference voltage Vref from the detected voltage Vdet and a reference voltage source B1 is, as the detection voltage Vdet becomes equal to the reference voltage Vref, generates a switching signal for controlling switching of switch Q1. ここでは、基準電圧Vrefと検出電圧Vdetとの差を増幅して出力するエラーアンプEampと、このエラーアンプEampの出力に基づいてPWM信号を形成してスイッチング信号として出力するパルス幅変調制御回路Pwmを含んで構成されている。 Here, an error amplifier Eamp for amplifying and outputting a difference between the reference voltage Vref and the detection voltage Vdet, a pulse width modulation control circuit Pwm for outputting a switching signal to form a PWM signal based on the output of the error amplifier Eamp It is configured to include a.
【0021】 [0021]
外部負荷10は、端子P1と端子P2との間に接続される。 External load 10 is connected between the terminal P1 and the terminal P2. 本発明は、負荷駆動装置の外部負荷をも含めて、携帯機器などの電子機器として構成することができる。 The present invention, including an external load of the load driving device may be configured as an electronic device such as a mobile device. この場合には、端子P1、P2は省略されることもある。 In this case, terminals P1, P2 is sometimes omitted.
【0022】 [0022]
外部負荷10としては、発光ダイオードLED1〜LED3が用いられる。 The external load 10, light emitting diode LED1~LED3 is used. この発光ダイオードLEDは、例えば白色発光ダイオードであり、LCD(液晶表示パネル)やキーのバックライト用等に用いられる。 The light emitting diode LED is, for example, a white light emitting diode, used for LCD, etc. for backlight (liquid crystal display panel) or a key. したがって、図1では3個の直列の例を示しているが、異なった数の直列接続、並列接続、或いは直並列接続など、その必要とされる発光エリアや発光量などに応じて、その組み合わせは種々の形態がある。 Therefore, an example is shown of a series of three in FIG. 1, different numbers of series-connected with parallel connection, or a series-parallel connection, depending on the light emitting area or the light-emitting amount of its required, the combination there are various forms.
【0023】 [0023]
この発光ダイオードLEDの電流ー電圧特性が図2に示されている。 Current - voltage characteristics of the light emitting diode LED is shown in FIG. この特性は、白色発光ダイオードLEDの電流If−電圧Vf特性の例である。 This property is an example of a current If- voltage Vf characteristic of a white light emitting diode LED. この図2は、横軸が対数表示の電流Ifであり、縦軸が電圧Vfである。 FIG 2, the horizontal axis is the logarithmic current If, the vertical axis is the voltage Vf. この発光ダイオードLEDは、電流Ifが20mA(図中A点)〜1.5mA(図中B点)の範囲で発光する。 The light emitting diode LED is current If emits light in the range of 20 mA (in the figure point A) ~1.5MA (figure B point). この電流Ifを変化させることにより、その電流Ifの大きさに応じて発光ダイオードLEDからの発光量が変化する。 By varying the current If, amount of light emitted from the light emitting diode LED is changed according to the magnitude of the current If.
【0024】 [0024]
電流Ifを20mAで使用すると、同図中のA点で示されるように、順方向電圧Vfが電圧3.4Vで動作する。 When the current If used in 20 mA, as shown at point A in the figure, the forward voltage Vf is operated at a voltage 3.4 V. しかし、各々の発光ダイオードLEDの特性は一律でなく、同じ電流20mAでもその順方向電圧Vfは、例えば3.4V〜4.0V程度の範囲でばらつく。 However, the characteristics of each of the light emitting diode LED is not uniform, the forward voltage Vf even the same current 20mA is varied in the range for example of about 3.4V~4.0V. このように、一般に白色発光ダイオードLEDは順方向電圧Vfが他色の発光ダイオードLEDよりも高く、これを3個直列に接続して使用するには、出力電圧Vo1は12.0V以上必要になる。 Thus, generally white light emitting diode LED is higher than the light emitting diodes LED of other colors forward voltage Vf, for use by connecting it to the three series, the output voltage Vo1 becomes unnecessarily 12.0V .
【0025】 [0025]
図3は、定電流源I1の回路構成の例を示す図である。 Figure 3 is a diagram showing an example of a circuit configuration of the constant current source I1. この図3において、電源電圧Vccとグランド間に定電流回路I11とN型MOSトランジスタ(以下、N型トランジスタ)Q2とが直列に接続されている。 In FIG. 3, the power supply voltage Vcc and the constant current circuit I11 between ground and N type MOS transistors (hereinafter, N-type transistor) and Q2 are connected in series. このN型トランジスタQ2のドレインとゲートが直接接続されている。 The drain and gate of the N-type transistor Q2 are directly connected. また、駆動電流Ioを流すためにN型トランジスタQ2よりも駆動能力の高いN型トランジスタQ3が設けられている。 Further, N-type transistor Q3 high driving capability is provided than N-type transistor Q2 to pass a drive current Io. 入力側トランジスタであるN型トランジスタQ2のゲートが、出力側トランジスタであるN型トランジスタQ3のゲートに接続されて、カレントミラー回路を構成している。 The gate of the N-type transistor Q2 which is the input side transistor, is connected to the gate of the N-type transistor Q3 is an output-side transistors constitute a current mirror circuit.
【0026】 [0026]
この図3で、定電流回路I11の電流を調整することにより、N型トランジスタQ3を流れる駆動電流Ioの大きさを所望の値に設定する。 In this Figure 3, by adjusting the current of the constant current circuit I11, it sets the magnitude of the drive current Io flowing through the N-type transistor Q3 to a desired value.
【0027】 [0027]
再び、図1に戻って説明する。 Again, referring back to FIG. 定電流源I1は、それに使用しているトランジスタ(図3のN型トランジスタQ3)の飽和電圧(約0.3V)以上の電圧があれば定電流動作できる。 The constant current source I1 can constant current operation if the saturation voltage (about 0.3V) or more voltage are used therefor transistor (N-type transistor Q3 of Fig. 3). その飽和電圧(約0.3V)を越える部分の電圧は、定電流源I1の内部での不要な損失分(即ち、損失は、電圧×電流)になる。 Voltage of the portion exceeding the saturation voltage (about 0.3V), the unnecessary loss of the inside of the constant current source I1 (i.e., loss, voltage × current) becomes. 定電流源I1の降下電圧Vdetが基準電圧Vrefになるように、電源回路100の出力電圧Vo1が制御される。 As the voltage drop Vdet of the constant current source I1 is equal to the reference voltage Vref, the output voltage Vo1 of the power supply circuit 100 is controlled. したがって、基準電圧Vrefは、定電流源I1に使用しているトランジスタの飽和電圧(約0.3V)に若干の余裕分の電圧を見込んだ値に設定される。 Therefore, the reference voltage Vref is set to a value in anticipation of some voltage margin to the saturation voltage of the transistor using the constant current source I1 (approximately 0.3V).
【0028】 [0028]
このように構成された負荷駆動装置の動作を、駆動電流Ioと出力電圧Vo1との特性を示す図4をも参照して説明する。 The operation of the thus configured load drive apparatus, reference will be described also to FIG. 4 showing the characteristics of the drive current Io and the output voltage Vo1. まず、負荷10である発光ダイオードに流す駆動電流Ioが定電流回路I11に設定される。 First, the drive current Io flowing in the light-emitting diode as a load 10 is set to the constant current circuit I11. スイッチング電源回路100は、検出電圧Vdetが基準電圧Vrefに等しくなるように、スイッチQ1のオンオフスイッチング制御が開始される。 Switching power supply circuit 100, the detection voltage Vdet is to be equal to the reference voltage Vref, the on-off switching control of the switch Q1 is started. これにより、出力電圧Vo1が徐々に上昇する。 Thus, the output voltage Vo1 gradually increases.
【0029】 [0029]
その結果、検出電圧Vdetと基準電圧Vrefとが等しくなり、駆動電流Ioが負荷10である発光ダイオードLED1〜LED3に流れる。 As a result, the detection voltage Vdet and a reference voltage Vref is equal, flowing through the LEDs LED1~LED3 drive current Io is the load 10. これにより、発光ダイオードは、所定の発光量で発光する。 Thus, the light emitting diode emits light at a predetermined light emission amount.
【0030】 [0030]
このとき、発光ダイオードLED1〜LED3の順方向高電圧Vfの特性がばらついていたとしても、出力電圧Vo1がそのばらつきに応じて所定値からばらつくだけであり、発光ダイオードLED1〜LED3からの発光の制御には格別の影響はない。 In this case, even if the characteristic of the forward high voltage Vf of the light-emitting diode LED1~LED3 were varied, only vary from the predetermined value the output voltage Vo1 is in accordance with the variation control of the light emission from the light emitting diode LED1~LED3 there is no particular effect on the. 定電流源I11の降下電圧、即ち検出電圧Vdetは一定である。 Drop voltage of the constant current source I11, i.e. the detected voltage Vdet is constant. したがって、出力電圧Vo1は、一定の検出電圧Vdetに、その時点での駆動電流Ioに応じた発光ダイオードLED1〜LED3の降下電圧Vled(=3×Vf)を加えた大きさになる。 Therefore, the output voltage Vo1 is constant detection voltage Vdet, becomes voltage drop Vled (= 3 × Vf) size plus the light emitting diode LED1~LED3 corresponding to the drive current Io at that time.
【0031】 [0031]
次に、発光ダイオードLED1〜LED3からの発光量を変更する場合には、駆動電流Ioの大きさを変更する。 Next, when changing the amount of light emitted from the light emitting diode LED1~LED3 changes the magnitude of the drive current Io. 例えば、駆動電流Ioを大きくすると、それに応じて発光ダイオードLED1〜LED3からの発光量が多くなる。 For example, increasing the drive current Io, amount of light emitted from the light emitting diode LED1~LED3 increases accordingly. これとともに、発光ダイオードLED1〜LED3の降下電圧Vledも、図2の特性に依って大きくなる。 Simultaneously, the voltage drop Vled emitting diodes LED1~LED3 also increases depending on the characteristics of FIG. なお、図4の出力電圧Vo1の傾きは、図2のIf−Vf特性に従う。 Note that the slope of the output voltage Vo1 of Figure 4 is in accordance with the If-Vf characteristic of Fig.
【0032】 [0032]
したがって、駆動電流Ioの増加に応じて発光ダイオードLED1〜LED3の降下電圧Vledが大きくなるから、出力電圧Vo1は図4のような特性で大きくなる。 Therefore, since the voltage drop Vled emitting diode LED1~LED3 increases with an increase in the drive current Io, the output voltage Vo1 increases with characteristics as shown in FIG 4. しかし、検出電圧Vdetは一定の値を維持するから、発光量を大きくするために駆動電流を大きくしても、定電流源I1での損失は増加しない。 However, since the detection voltage Vdet is maintained at constant value, increasing the driving current in order to increase the light emission amount, the loss of the constant current source I1 does not increase. したがって、負荷駆動装置の効率は高く維持される。 Therefore, the efficiency of the load driving device is maintained high.
【0033】 [0033]
図5は、本発明の第2の実施の形態に係る負荷駆動装置の構成を示す図である。 Figure 5 is a diagram showing a configuration of a load driving device according to a second embodiment of the present invention. 図5においては、負荷10に加えて、他の負荷20を付加しており、また、負荷が増えたことに伴って、負荷20に対応して定電流源I20を設けている。 In FIG. 5, in addition to the load 10, which adds another load 20, also in association with the load is increased, there is provided a constant current source I20 in response to the load 20. なお、付加する他の負荷は2以上でも良い。 Incidentally, other loads may be two or more to be added.
【0034】 [0034]
図5では、負荷10に直列に定電流源I10が設けられ、その直列回路に駆動電流Io1が流れる。 In Figure 5, the constant current source I10 is provided in series with the load 10, the drive current Io1 flows through the series circuit. 定電流源I10の降下電圧が第1検出電圧Vdet1になる。 Drop voltage of the constant current source I10 is the first detection voltage Vdet1. 同様に、負荷20に直列に定電流源I20が設けられ、その直列回路に駆動電流Io2が流れる。 Similarly, the constant current source I20 is provided in series with the load 20, the drive current Io2 flows through the series circuit. 定電流源I20の降下電圧が第2検出電圧Vdet2になる。 Drop voltage of the constant current source I20 is the second detection voltage Vdet2. P11、P12、P21、P22は、負荷接続用の端子である。 P11, P12, P21, P22 is a terminal for the load connections.
【0035】 [0035]
また、制御回路ContのエラーアンプEampは、2つの非反転入力端子(+)と1つの反転入力端子(−)を持っている。 The error amplifier Eamp of the control circuit Cont has two non-inverting input terminal (+) and one inverting input terminal - has (). 2つの非反転入力端子(+)には、第1検出電圧Vdet1及び第2検出電圧Vdet2がそれぞれ入力され、反転入力端子(−)には基準電圧Vrefが入力される。 The two non-inverting input terminal (+), the first detection voltage Vdet1 and the second detection voltage Vdet2 is inputted, the inverting input terminal (-) of the reference voltage Vref is input to. このエラーアンプEampでは、2つの非反転入力端子(+)に入力される第1検出電圧Vdet1と第2検出電圧Vdet2のうちの低い方の電圧が選択されて、基準電圧Vrefと比較される。 In the error amplifier Eamp, lower voltage ones of the first detection voltage Vdet1 to be input to the two non-inverting input terminal (+) and the second detection voltage Vdet2 is selected and compared with the reference voltage Vref. その他の構成は、図1の第1の実施の形態におけるものと同様である。 Other configurations are the same as those in the first embodiment of FIG.
【0036】 [0036]
この図5の負荷駆動回路では、複数の負荷10、20の駆動電流Io1、Io2を個別に調整することができる。 In the load driving circuit of FIG. 5, it is possible to adjust the drive current Io1, Io2 of the plurality of loads 10 and 20 separately. そして、定電流源I10、I20の降下電圧Vdet1、Vdet2のうちの低い方の電圧が自動的に選択されて、電源回路100のスイッチング制御が行われる。 The lower voltage ones of drop voltage Vdet1, Vdet2 of the constant current source I10, I20 is automatically selected, the switching control of the power supply circuit 100 is performed.
【0037】 [0037]
複数の負荷10、20の駆動電流Io1、Io2を流す定電流源I10、I20の定電流動作は、確保される。 Constant current operation of the drive current Io1, flow Io2 constant current source I10, I20 of the plurality of loads 10 and 20, is ensured. したがって、複数負荷に対しても、第1の実施の形態におけると同様の効果を得ることができる。 Therefore, even for multiple loads, it is possible to obtain the same effect as in the first embodiment.
【0038】 [0038]
【発明の効果】 【Effect of the invention】
本発明によれば、出力電圧を出力回路(直流ー直流変換型電源回路)を用いて電源電圧から変換して得るとともに、流れる電流で動作点が決まる負荷、例、発光ダイオード群に直列に電流値が調整できる定電流源を接続するから、負荷側で要求される電流を、安定して負荷に流すことができる。 According to the present invention, together with obtained by converting the power supply voltage using an output circuit the output voltage (DC over the DC conversion type power supply circuit), the operating point in the current flowing is determined load, eg, the current in series with the light emitting diode group since the value is to connect the constant current source can be adjusted, the current required by the load, can flow to stably load.
【0039】 [0039]
また、定電流源の降下電圧が、その定電流源が安定して動作できる電圧値に設定された基準電圧に等しくなるように、直流ー直流変換型電源回路の出力電圧が制御される。 Further, the voltage drop of the constant current source, its constant current source to be equal to a reference voltage set to a voltage value that can operate stably, the output voltage of the DC over the DC conversion type power supply circuit is controlled. したがって、負荷である発光ダイオード群に特性のばらつきがあっても予定の発光量のために必要な電流が流れるように、直流ー直流変換型電源回路の出力電圧は、自動調整される。 Thus, as current flows required for light emission amount of scheduled even if variations in characteristics to the light emitting diode group as a load, the output voltage of the DC over the DC conversion type power supply circuit is automatically adjusted.
【0040】 [0040]
また、定電流源の降下電圧は、設定した電流値が維持できるように基準電圧に自動的に制御されるから、負荷である発光ダイオード群に流れる電流が大きくなった場合でも、抵抗での電圧検出におけるような、損失の増加はない。 Further, the voltage drop of the constant current source, since is automatically controlled to the reference voltage so as to maintain a current value set, even if the current flowing through the LEDs serving as the load is increased, the voltage at resistor as in the detection, no increase in loss. したがって、負荷電流の増加に伴う損失が実質的に増加しないから、広い負荷電流の範囲において高効率で負荷を駆動することができる。 Accordingly, since the loss due to the increase in the load current does not substantially increase, the load can be driven at high efficiency in a wide range of load currents.
【0041】 [0041]
また、直流ー直流変換型電源回路は、コイルへの通電をスイッチングして電源電圧を出力電圧に変換するスイッチング電源回路であるから、変換効率が良く、また、必要な高電圧を出力することができる。 Further, the DC over the DC conversion type power supply circuit, since a switching power supply circuit for converting the energization of the coil to the switching to the power supply voltage output voltage, good conversion efficiency, also is possible to output a high voltage necessary it can.
【0042】 [0042]
また、負荷である発光ダイオード群毎に、対応して可変電流型定電流源が設けられ、かつ、それらの定電流源の降下電圧の低い方の電圧にしたがって直流ー直流変換型電源回路が制御されるから、負荷である発光ダイオード群のそれぞれに所定の定電流を安定して流すことができる。 Further, each light emitting diode group as a load, a variable current type constant current source are provided corresponding and DC over the DC conversion type power supply circuit is controlled in accordance with their voltage lower of drop voltage of the constant current source since the can flow each into a predetermined constant current of the light emitting diode group is load stably.
【図面の簡単な説明】 BRIEF DESCRIPTION OF THE DRAWINGS
【図1】本発明の第1の実施の形態に係る負荷駆動装置の構成を示す図【図2】発光ダイオードLEDの電流ー電圧特性を示す図【図3】定電流源I1の回路構成の例を示す図【図4】駆動電流Ioと出力電圧Vo1との特性を示す図【図5】本発明の第2の実施の形態に係る負荷駆動装置の構成を示す図【符号の説明】 [1] in Figure 1 [2] showing the configuration of a load driving device according to an embodiment of the circuit configuration of FIG. 1. FIG. 3 constant current source I1 indicating the current over-voltage characteristics of the light-emitting diode LED of the present invention an example diagram showing the configuration of a load driving device according to the second embodiment of FIGS. 5A and 5B present invention showing the characteristics of FIG. 4 shows the drive current Io and the output voltage Vo1 [description of symbols]
100 電源回路10、20 負荷LED1〜LED3 発光ダイオードL1 コイルC1 平滑用コンデンサD1 ダイオードQ1 スイッチCont 制御回路B1 基準電圧源I1、I10、I20 定電流源I11 定電流回路Q2、Q3 N型MOSトランジスタVcc 入力電源電圧Vo1 出力電圧Io、Io1、Io2 駆動電流Vled、Vled1、Vled2 発光ダイオード降下電圧Vdet、Vdet1、Vdet2 検出電圧Vref 基準電圧 100 power supply circuits 10 and 20 load LED1~LED3 emitting diode L1 coil C1 smoothing capacitor D1 diode Q1 switch Cont control circuit B1 reference voltage source I1, I10, I20 a constant current source I11 constant current circuit Q2, Q3 N-type MOS transistor Vcc input supply voltage Vo1 output voltage Io, Io1, Io2 drive current Vled, Vled1, Vled2 emitting diode drop voltage Vdet, Vdet1, Vdet2 detection voltage Vref reference voltage

Claims (8)

  1. 電源電圧を変換して所定の出力電圧として負荷に供給する出力回路と、 An output circuit for supplying to a load as a predetermined output voltage by converting a power supply voltage,
    前記負荷に直列に接続されて調整可能な定電流を流す定電流源とを備え、 And a constant current source supplying a constant current adjustable is connected in series with the load,
    前記出力回路は、前記負荷と前記定電流源との接続点の電圧が一定電圧になるように前記所定の出力電圧を制御することを特徴とする負荷駆動装置。 It said output circuit includes a load driving device and a voltage at the node between the constant current source and the load to control the predetermined output voltage to be constant voltage.
  2. 前記定電流源は、電流可変型の定電流回路と、この定電流回路と直列に接続されたカレントミラー用入力側トランジスタと、このカレントミラー用入力側トランジスタと同じ制御入力が与えられるカレントミラー用出力側トランジスタとを含んでカレントミラー回路が構成されており、前記カレントミラー用出力側トランジスタに前記調整可能な定電流が流されることを特徴とする、請求項1記載の負荷駆動装置。 It said constant current source includes a constant current circuit of the current variable, the input-side transistor current mirror connected to the constant current circuit in series, a current mirror with the same control input is supplied with the current mirror input transistor is constituted by the current mirror circuit and an output side transistor, wherein wherein the adjustable constant current to the output side transistor current mirror is passed through, the load driving apparatus according to claim 1.
  3. 前記外部負荷は、少なくとも1つの発光ダイオードを含む発光ダイオード群であることを特徴とする、請求項2記載の負荷駆動装置。 Said external load, characterized in that it is a light emitting diode group including at least one light emitting diode, the load driving device according to claim 2, wherein.
  4. 前記一定電圧は、前記カレントミラー用出力側トランジスタの飽和電圧より高い電圧であることを特徴とする、請求項2記載の負荷駆動装置。 The constant voltage, characterized in that said a voltage higher than the saturation voltage of the output-side transistor current mirror, the load driving device according to claim 2, wherein.
  5. 前記出力回路は、コイルと、このコイルへの通電をスイッチングするスイッチと、前記コイルと前記スイッチとの接続点と出力端子との間に設けられた整流素子とを有するスイッチング電源回路であることを特徴とする、請求項1乃至4記載の負荷駆動装置。 It said output circuit includes a coil, a switch for switching the current supply to the coil, said a switching power supply circuit having a rectifying element provided between the coil and the connection point between the switch and the output terminal wherein, the load driving device according to claim 1 to 4, wherein.
  6. 前記スイッチング電源回路は、さらに、前記整流素子の出力電圧点側に接続された平滑回路と、前記負荷と前記定電流源との接続点の電圧が基準電圧に等しくなるように前記スイッチのオンオフスイッチングを行う制御回路と、を有することを特徴とする、請求項5記載の負荷駆動装置。 The switching power supply circuit further includes a smoothing circuit connected to the output voltage point side of the rectifying element, off switching of the switch such that the voltage at the node between the constant current source and the load is equal to the reference voltage characterized by and a control circuit that performs load driving device according to claim 5.
  7. 前記負荷及び前記定電流源が複数であり、前記複数の負荷に前記複数の定電流源がそれぞれ直列に接続されてそれぞれ調整可能な定電流を流すとともに、 It said load and said a constant current source is a plurality, the plurality of constant current source to the plurality of loads with each flow of each adjustable constant current are connected in series,
    前記複数の負荷と前記複数の定電流源との各接続点の電圧のうちの最も低い電圧が一定電圧になるように前記所定の出力電圧を制御することを特徴とする、請求項1記載の負荷駆動装置。 And controlling said predetermined output voltage as the lowest voltage becomes constant voltage of the voltage of the connection point of the plurality of constant current source and the plurality of loads, according to claim 1, wherein load driving device.
  8. 請求項1乃至7記載の負荷駆動装置を用いていることを特徴とする携帯機器。 Portable device characterized in that it uses the load driving device according to claim 1 to 7, wherein.
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DE200460008840 DE602004008840T2 (en) 2003-07-07 2004-06-23 Load driving device and portable device using such a load driving device
EP20040014726 EP1499165B1 (en) 2003-07-07 2004-06-23 Load driving device and portable apparatus utilizing such driving device
US10879315 US7235954B2 (en) 2003-07-07 2004-06-29 Load driving device and portable apparatus utilizing such driving device
CN 201010145440 CN101789692B (en) 2003-07-07 2004-07-02 Load driving device and liquid crystal apparatus
CN 200410062174 CN1578095B (en) 2003-07-07 2004-07-02 Load driving device and portable apparatus utilizing such driving device
KR20040052190A KR20050006042A (en) 2003-07-07 2004-07-06 Load driving device and portable equipment
US11750894 US7541785B2 (en) 2003-07-07 2007-05-18 Load driving device and portable apparatus utilizing such driving device
US12428338 US7944189B2 (en) 2003-07-07 2009-04-22 Load driving device and portable apparatus utilizing such driving device
US12731006 US8519680B2 (en) 2003-07-07 2010-03-24 Load driving device, and lighting apparatus and liquid crystal display device using the same
US13080498 US8242756B2 (en) 2003-07-07 2011-04-05 Load driving device and portable apparatus utilizing such driving device
US13952333 US8836295B2 (en) 2003-07-07 2013-07-26 Load driving device, and lighting apparatus and liquid crystal display device using the same
US14454528 US9526138B2 (en) 2003-07-07 2014-08-07 Load driving device, and lighting apparatus and liquid crystal display device using the same
US15002275 US9526139B2 (en) 2003-07-07 2016-01-20 Load driving device, and lighting apparatus and liquid crystal display device using the same
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