JP3610382B2 - Power supply - Google Patents

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JP3610382B2
JP3610382B2 JP2001308162A JP2001308162A JP3610382B2 JP 3610382 B2 JP3610382 B2 JP 3610382B2 JP 2001308162 A JP2001308162 A JP 2001308162A JP 2001308162 A JP2001308162 A JP 2001308162A JP 3610382 B2 JP3610382 B2 JP 3610382B2
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semiconductor element
load
load current
current
heat
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JP2003116274A (en
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愛郎 高木
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Origin Electric Co Ltd
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L2924/00—Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
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    • H01L2924/0002—Not covered by any one of groups H01L24/00, H01L24/00 and H01L2224/00

Description

【０００１】
【発明の属する技術分野】
本発明は、軽負荷時にダミ−負荷として働くバイポーラトランジスタのような半導体素子を有する電源に関する。
【０００２】
【従来の技術】
一般に、スイッチング電源回路などにあっては、負荷電流が非常に小さくなると、平滑用コンデンサと平滑回路を構成する平滑用インダクタがカットオフすることがあり、このような場合には出力電圧がかなり高くなってしまうとい現象が生じる。この現象を防ぐため、ダミ−抵抗を負荷と並列に接続して通常の負荷電流の電流値の１〜２％の電流を流し、平滑用インダクタを流れる電流が途切れないようにしていた。しかし、この回路構成では常時ダミ−抵抗を電流が流れ、その電流は無効電流であるので、電力効率が低下するばかりでなく、ダミ−抵抗の発熱が問題になる。
【０００３】
この問題点を解決するために図５に示すようなＤＣ−ＤＣコンバータ回路が提案されている。この回路を説明すると、１と２は直流入力端子、３は入力側平滑用コンデンサ、４は１次巻線４Ｐと２次巻線４Ｓとを有するトランス、５は図示しない制御回路からのパルス幅制御信号により高周波でスイッチングを行うＦＥＴのようなスイッチング半導体素子、６は２個のダイオードを並列接続してなる整流素子、７は通常のフライホイールダイオード、８は平滑用コンデンサ９ａ、９ｂと平滑回路を構成する平滑用インダクタ、１０は並列接続された複数の抵抗からなるダミ−抵抗、１１はダミ−抵抗に直列接続されたトランジスタのような半導体スイッチ、１２は負荷電流を検出するためのシャントのような電流検出器、１３は電流検出器１２を流れる電流が下限値以下になるとき半導体スイッチ１１をターンオンさせる制御回路、１４と１５は負荷端子である。
【０００４】
この回路にあっては、軽負荷状態になって、電流検出器１２を流れる負荷電流が設定値よりも小さくなると、制御回路１３はタ−ンオ−ン信号を半導体スイッチ１１に与える。これに伴い、半導体スイッチ１１はターンオンし、複数のダミ−抵抗１０を通して電流を流す。つまり、図４の電源では軽負荷時以外の負荷状態ではダミ−抵抗１０を通して電流が流れることは無く、負荷電流が所定の値以下に減少しようとすると、半導体スイッチ１１がオンしてダミ−抵抗１０を通して電流を流し、平滑用インダクタ８を流れる電流を確保し、平滑用インダクタ８がカットオフしないようにしている。
【０００５】
【発明が解決しようとする課題】
この回路構成では従来よりもダミ−抵抗１０の電力損失が小さくなるが、しかし、例えば、この電源装置が４８Ｖ１００Ａを出力するものであり、軽負荷時には負荷電流の１〜２％に等しい電流をダミ−抵抗１０に流すとすると、単純計算でも４８〜９６Ｗの抵抗器が必要となる。通常、抵抗器は放熱などを考慮して１／３〜１／４の負荷で使用するので、三分の一の負荷で使用したとすると、５Ｗの抵抗器を３０〜６０本必要となり、これらをプリント基板に実装しなければならず、小型化が難しいばかりでなく、実装に時間がかかり、コストアップになるという欠点がある。なお、図示しないが、実際の装置にあっては、スイッチング半導体素子５、整流素子６とフライホイールダイオード７のような主発熱素子、半導体スイッチ１１はそれぞれ別々の放熱器に取り付けられているか、共通の放熱器に取り付けた場合にはそれらの発熱の和に見合った放熱能力をもつ大きな放熱器を用いている。
本発明は、特定の回路構成の電源において放熱器を小さくすることが可能な構造を提供することを主目的としている。
【０００６】
【課題を解決するための手段】
この課題を解決するため、入力電源側から負荷に供給される電力を調整するスイッチング半導体素子、整流素子、フライホイール素子のような主発熱素子と、平滑用インダクタと平滑用コンデンサとからなる平滑回路とで構成されたコンバータ回路と、
該コンバータ回路の出力端子間に跨がって接続された半導体素子と、
負荷電流が減少するとき前記半導体素子を抵抗素子として動作させるよう制御する制御回路とを備え、
前記制御回路は、負荷電流が設定値よりも小さくなったとき前記半導体素子にオン信号を与え、負荷電流値に見合ったインピーダンスを呈するように抵抗素子として前記半導体素子を制御し、負荷電流が設定値以上の場合には前記半導体素子をオフ状態で保持させる電源装置において、
前記主発熱素子の一つ以上と前記半導体素子とが断面Ｌ字状の放熱板又はヒートパイプを介し、前記主発熱素子の最大発熱量に対応する放熱能力をもつ放熱器に一緒に取り付けたことを特徴とする電源装置を提供するものである。
【０００９】
【発明の実施の形態】
この発明は、負荷電流が最少設定値以上の場合には電流を流さず、負荷電流が最少設定値よりも小さい場合には負荷電流の２％程度以下の電流を流すダミ−抵抗として作用する半導体素子を備えた回路構成の電源に適用され、前記負荷電流に対応する主回路電流を調整するためのスイッチング半導体素子、主回路電流を整流するための整流素子、フライホイルダイオードのいずれか、あるいはそれら二つ以上が取り付けられた放熱器に前記ダミ−用の半導体素子を一緒に取り付けたことを特徴とする。
【００１０】
先ず、この発明が適用される回路構成の電源の一例について図１により説明する。この図１において、図５で示した記号と同じ記号は相当する部材を示すものとし、１６は制御回路１３からの制御信号により軽負荷時に、例えば負荷電流の１〜２％程度の電流を流す可変インピーダンスとして働くバイポーラトランジスタのような半導体素子であり、１７は半導体素子１６を流れる電流を保護するための保護用抵抗である。この回路では、負荷電流の減少により電流検出抵抗器１２を流れる電流が設定値以下に低下するとき、制御回路１３は検出電流値に見合った電流が半導体素子１６を流れるように、半導体素子１６のインピーダンスを制御する。つまり、平滑用インダクタ８がカットオフしないように、軽負荷時、つまり負荷電流が非常に小さいとき、平滑用インダクタ８を流れる電流が定常時の負荷電流の１〜２％以上確保されるように、半導体素子１６は不飽和状態で導通する。そして、負荷電流が設定値、つまり平滑用インダクタ８がカットオフしない値以上であるときには、制御回路１３は、電流検出器１２の電流検出値が基準値以上であるので、半導体素子１６にオン信号を与えず、したがって、半導体素子１６はオフであり、この状態では半導体素子１６の電力損失はゼロである。
【００１１】
ここで、負荷電流が定常状態であるときには、スイッチング半導体素子５、整流素子６、フライホイルダイオード７を流れる電流の定常状態にあり、それら電子部品の発熱は大きい状態にある。しかし、このときには半導体素子１６はオフであるから、電力損失はゼロであり、発熱しない。一方、軽負荷時には、定常時に比べてスイッチング半導体素子５、整流素子６、フライホイ−ルダイオード７を流れる電流はかなり小さく、したがって、それらの発熱量は定常時に比べてかなり小さくなる。このとき半導体素子１６は負荷電流の大きさに逆比例する電流を流すようにインピーダンス制御されるので、その発熱量は大きくなる。つまり、この回路ではスイッチング半導体素子５、整流素子６、及びフライホイルダイオード７の発熱が大きいとき、半導体素子１６の発熱はほぼゼロであり、逆にスイッチング半導体素子５、整流素子６、及びフライホイルダイオード７の発熱が小さいときには、半導体素子１６の発熱は大きくなる。
【００１２】
したがって、この発明では図２にその１実施例を示すように、整流素子６の取り付けられた放熱器２０に半導体素子１６を取り付けている。図２において、２１はプリント回路基板であり、整流素子６はそのリード線６ａを介してプリント回路基板２１にハンダ付けされ、半導体素子１６はそのリード線１６ａを介してプリント回路基板２１にハンダ付けされている。そして、整流素子６は断面Ｌ字状の放熱板２２を通して放熱器２０に固定され、半導体素子１６は断面Ｌ字状の放熱板２３を通して放熱器２０に固定されている。したがって、この構造では整流素子６の発熱は断面Ｌ字状の放熱板２２を通して放熱器２０に伝達されて放熱され、半導体素子１６の発熱は断面Ｌ字状の放熱板２３を通して放熱器２０に伝達されて放熱される。前述したように、半導体素子１６は負荷電流が設定値以下のときだけ発熱し、その期間では整流素子６を流れる電流は小さく、したがって発熱も小さいから、放熱器２０の放熱能力は整流素子６が単独で取り付けられる場合と同程度で済む。つまり、別途放熱器を用意したり、半導体素子１６の発熱分だけ放熱器を大きくする必要がないので、電源の小型化、経済性に優れているばかりでなく、負荷電流が設定値以下に減少しない限り半導体素子１６はオフであるので、電力効率を向上させることができる。
【００１３】
なお、整流素子６、半導体素子１６は図示しない熱伝導の良好な電気絶縁シートを介してそれぞれの断面Ｌ字状の放熱板２２、２３に取り付けられている。また、放熱器２０に整流素子６と半導体素子１６を一緒に取り付ける例を述べたが、必要に応じて整流素子６と半導体素子１６の他に、スイッチング半導体素子５とフライホイルダイオード７の双方又はいずれか一方を一緒に放熱器２０に取り付けても良い。この場合には、放熱器２０に取り付けられる整流素子６の最大発熱量、スイッチング半導体素子５とフライホイルダイオード７の双方の最大発熱量又はいずれか一方の最大発熱量の和の発熱量に対応する放熱能力を有する放熱器を用いる。
【００１４】
次に、図３はこの発明を適用するためのチョッパ型電源の回路構成の一例を示す図である。図３において、図１で示した記号と同一の記号は相当する部材を示すものとし、３１と３２は出力端子１４と１５間の負荷電圧を分割する抵抗器であり、抵抗器３２は出力電圧検出抵抗として働く。３３は主制御回路であり、出力端子１４と１５間の負荷電圧が一定になるようにスイッチング半導体素子５をパルス幅制御する。この回路においても図１の回路と同様に、負荷電流が定常状態のときには半導体素子１６は制御回路１３によってオフ状態に保持される。軽負荷状態、つまり平滑用インダクタ８がカットオフに至る寸前の電流値に負荷電流が減少すると、制御回路１３は電流検出抵抗器１２の両端の電圧が基準値よりも小さくなるので、半導体素子１６にオン信号を与え、負荷電流値に見合ったインピーダンスを呈するように半導体素子１６を制御する。このとき半導体素子１６を流れる電流は負荷電流の２％程度以下であり、負荷電流と半導体素子１６を流れる電流との和の電流が平滑用インダクタ８をカットオフさせないように、制御回路１３は半導体素子１６を制御する。
【００１５】
したがって、軽負荷時にはスイッチング半導体素子５を流れる電流は非常に小さいのでその発熱量も大幅に小さくなるが、半導体素子１６は不飽和状態で動作するので、半導体素子１６の発熱量は大きくなる。一方、定常状態では、スイッチング半導体素子５を流れる電流は大きいのでその発熱量も大きいが、半導体素子１６はオフであるのでその発熱量は実質的にゼロである。上記から、定常時及び軽負荷時にかかわらず動作期間全体におけるスイッチング半導体素子５の発熱量と半導体素子１６の発熱量の和はあまり変わらないことが分かる。したがって、この実施例ではスイッチング半導体素子５の最大発熱量に対応する放熱能力を有する放熱器２０’（鎖線で示す）に、半導体素子１６を取り付けている。したがって、この実施例においても半導体素子１６の発熱を放熱するための専用の放熱器は不要であり、また半導体素子１６の発熱を放熱するために放熱器２０’を大きくする必要も無いので、小型化と低コスト化が可能である。なお、放熱器２０’にはフライホイールダイオード７も一緒に取り付けても良い。この場合には、スイッチング半導体素子５の最大発熱量とフライホイールダイオード７の最大発熱量との和の発熱量に対応する放熱能力をもつ放熱器２０’を使用することになる。
【００１６】
図２の実施例では、主発熱素子である整流素子６も半導体素子１６もそれぞれの放熱板２２、２３を介して同一の放熱器２０に取り付けられたが、図４に示す実施例では、主回路におけるスイッチング半導体素子、整流素子、フライホイールダイオードのような主発熱素子４０、４１、４２をそれぞれ熱伝導の良好な電気絶縁シート４３、４４、４５を介して放熱器２０に取り付け、また、ダミー負荷抵抗の役割を果たす半導体素子１６、１６’は通常のヒートパイプ４６を介して放熱器２０に取り付けられている。半導体素子１６、１６’もそれぞれ熱伝導の良好な電気絶縁シート４７、４８を通してヒートパイプ４６に固定されている。これら電気絶縁シートは主発熱素子４０、４１、４２と放熱器２０との間、あるいは半導体素子１６、１６’とヒートパイプ４６との間の密着性を高め、放熱を高める役割も果たす。
【００１７】
放熱器２０はネジ止めなどの方法でプリント基板４９に固定されている。また、図示していないが、主発熱素子４０、４１、４２及び半導体素子１６、１６’のリード端子はプリント基板４９にハンダ付けされている。ヒートパイプ４６についても図示していないが、ヒートパイプ４６の先端部分に固定されたフランジを放熱器２０にネジ止めするなどの方法で固定されている。この実施例でも、動作時の各時点における予測される主発熱素子４０、４１、４２の最大発熱量の和に対応する放熱能力をもつ放熱器２０に、ヒートパイプ４６を介して半導体素子１６、１６’を取り付けることにより、放熱器を不要に大形化する必要がなく、小型化することができる。
【００１８】
なお、本発明は以上述べた実施例に限られることはなく、図１のシングルエンデッド形インバータに代えて通常の構成のフルブリッジ形インバータ、ハーフブリッジ形インバータでも良く、また図３の降圧形コンバータに代えて通常の構成の昇圧形コンバータでも良い。また、コンバータが整流素子とフライホイールダイオードとしてＦＥＴを用いる同期整流回路であっても勿論よい。このように本発明はインダクタを持ついずれの構成のコンバータでも良く、そのコンバータの直流出力端子間に跨がってダミー負荷として働く半導体素子を備え、軽負荷時以外にはその半導体素子はオフに制御され、軽負荷時にはその半導体素子は負荷電流に見合ったインピーダンスを持つように制御されれば良い。
【００１９】
【発明の効果】
以上述べたように本発明では、軽負荷時以外にはオフで、軽負荷時には負荷電流に見合ったインピーダンスを持つように制御される半導体素子を、コンバータ回路のスイッチング半導体素子、整流素子、フライホイールダイオードのような主発熱素子の少なくともいずれかと一緒に放熱器に取り付けているので、その放熱器を大きくすることなく前記半導体素子の放熱器を省略することができ、電源装置の小型化と低コスト化が達成できる。
【図面の簡単な説明】
【図１】本発明が適用される電源回路の一例を示す図である。
【図２】本発明を説明するための構成を示す図である。
【図３】本発明が適用される電源回路の別の一例を示す図である。
【図４】本発明を説明するための構成を示す図である。
【図５】従来の電源装置の一例を示す図である。
【符号の説明】
【符号の説明】
１、２・・・入力端子 ３・・・コンデンサ
４・・・トランス ５・・・スイッチング半導体素子
５・・・フィラメントトランス
６・・・整流素子 ７・・・フライホイールダイオード
８・・・平滑用インダクタ ９・・・平滑用コンデンサ
１２・・・電流検出用抵抗 １３・・・制御回路
１４、１５・・・出力端子 １６・・・半導体素子（ダミ−負荷）
２１・・・プリント回路基板 ３１、３２・・・出力電圧分割抵抗
３３・・・主制御回路 ４０、４１、４２・・・主発熱素子
４３、４４、４５、４７、４８・・・電気絶縁シ−ト
４６・・・ヒートパイプ ４９・・・プリント回路基板[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a power supply having a semiconductor element such as a bipolar transistor that acts as a dummy load at a light load.
[0002]
[Prior art]
Generally, in a switching power supply circuit or the like, if the load current becomes very small, the smoothing capacitor and the smoothing inductor constituting the smoothing circuit may be cut off. In such a case, the output voltage is considerably high. When this happens, a phenomenon occurs. In order to prevent this phenomenon, a dummy resistor is connected in parallel with the load so that a current of 1 to 2% of a normal load current value flows, so that the current flowing through the smoothing inductor is not interrupted. However, in this circuit configuration, a current always flows through the dummy resistor, and the current is a reactive current. Therefore, not only is the power efficiency lowered, but heat generation of the dummy resistor becomes a problem.
[0003]
In order to solve this problem, a DC-DC converter circuit as shown in FIG. 5 has been proposed. Describing this circuit, 1 and 2 are DC input terminals, 3 is an input side smoothing capacitor, 4 is a transformer having a primary winding 4P and a secondary winding 4S, and 5 is a pulse width from a control circuit (not shown). Switching semiconductor element such as FET that performs switching at high frequency by a control signal, 6 is a rectifying element formed by connecting two diodes in parallel, 7 is a normal flywheel diode, 8 is a smoothing capacitor 9a, 9b and a smoothing circuit 10 is a dummy resistor composed of a plurality of resistors connected in parallel, 11 is a semiconductor switch such as a transistor connected in series to the dummy resistor, and 12 is a shunt for detecting a load current. Such a current detector 13 is a control circuit for turning on the semiconductor switch 11 when the current flowing through the current detector 12 falls below a lower limit value. And 15 is a load terminal.
[0004]
In this circuit, when the light load state occurs and the load current flowing through the current detector 12 becomes smaller than the set value, the control circuit 13 gives a turn-on signal to the semiconductor switch 11. Along with this, the semiconductor switch 11 is turned on, and a current flows through the plurality of dummy resistors 10. That is, in the power supply of FIG. 4, no current flows through the dummy resistor 10 in a load state other than during light load. If the load current is reduced to a predetermined value or less, the semiconductor switch 11 is turned on and the dummy resistor is turned on. A current is passed through 10 to ensure a current flowing through the smoothing inductor 8 so that the smoothing inductor 8 is not cut off.
[0005]
[Problems to be solved by the invention]
In this circuit configuration, the power loss of the dummy resistor 10 is smaller than in the prior art. However, for example, this power supply device outputs 48V100A, and when the load is light, a current equal to 1 to 2% of the load current is damaged. -If it flows through the resistor 10, a simple calculation requires a resistor of 48 to 96 W. Normally, resistors are used with a load of 1/3 to 1/4 taking heat dissipation into consideration, so if they are used with 1/3 load, 30-60 resistors of 5W are required. Must be mounted on a printed circuit board, which is not only difficult to reduce in size, but also takes time to mount and increases costs. Although not shown, in an actual device, the switching semiconductor element 5, the main heating element such as the rectifying element 6 and the flywheel diode 7, and the semiconductor switch 11 are each attached to a separate heatsink or common. When it is attached to a heatsink, a large heatsink with a heat radiation capacity commensurate with the sum of the heat generation is used.
The main object of the present invention is to provide a structure that can reduce the size of a heatsink in a power supply having a specific circuit configuration.
[0006]
[Means for Solving the Problems]
In order to solve this problem, a smoothing circuit comprising a main heating element such as a switching semiconductor element, a rectifying element, and a flywheel element for adjusting power supplied to a load from the input power source side, and a smoothing inductor and a smoothing capacitor A converter circuit composed of
A semiconductor element connected across the output terminals of the converter circuit;
A control circuit for controlling the semiconductor element to operate as a resistance element when a load current decreases ,
The control circuit gives an ON signal to the semiconductor element when the load current becomes smaller than a set value, controls the semiconductor element as a resistance element so as to exhibit an impedance corresponding to the load current value, and the load current is set In a power supply device that holds the semiconductor element in an off state when the value is equal to or greater than the value,
One or more of the main heating elements and the semiconductor element are attached together with a radiator having a heat radiation capacity corresponding to the maximum heat generation amount of the main heating element via a heat sink or heat pipe having an L-shaped cross section. The power supply device characterized by the above is provided.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
The present invention does not flow current when the load current is equal to or greater than the minimum set value, and acts as a dummy resistor for flowing current of about 2% or less of the load current when the load current is smaller than the minimum set value. One of a switching semiconductor element for adjusting a main circuit current corresponding to the load current, a rectifying element for rectifying the main circuit current, a flywheel diode, or the like, which is applied to a power supply having a circuit configuration including elements The semiconductor element for the dummy is attached together to a radiator to which two or more are attached.
[0010]
First, an example of a power supply having a circuit configuration to which the present invention is applied will be described with reference to FIG. In FIG. 1, the same symbols as those shown in FIG. 5 indicate corresponding members. Reference numeral 16 denotes a control signal from the control circuit 13 that causes a current of about 1 to 2% of the load current to flow at a light load. A semiconductor element such as a bipolar transistor that works as a variable impedance, and 17 is a protective resistor for protecting the current flowing through the semiconductor element 16. In this circuit, when the current flowing through the current detection resistor 12 decreases below the set value due to a decrease in the load current, the control circuit 13 causes the current corresponding to the detected current value to flow through the semiconductor element 16. Control impedance. That is, in order to prevent the smoothing inductor 8 from being cut off, at a light load, that is, when the load current is very small, the current flowing through the smoothing inductor 8 is ensured to be 1 to 2% or more of the load current at the steady state. The semiconductor element 16 conducts in an unsaturated state. When the load current is equal to or greater than the set value, that is, the value at which the smoothing inductor 8 is not cut off, the control circuit 13 determines that the current detection value of the current detector 12 is equal to or greater than the reference value, Therefore, the semiconductor element 16 is off, and in this state, the power loss of the semiconductor element 16 is zero.
[0011]
Here, when the load current is in a steady state, the current flowing through the switching semiconductor element 5, the rectifying element 6, and the flywheel diode 7 is in a steady state, and the heat generation of these electronic components is large. However, since the semiconductor element 16 is off at this time, the power loss is zero and no heat is generated. On the other hand, when the load is light, the current flowing through the switching semiconductor element 5, the rectifying element 6, and the flywheel diode 7 is considerably smaller than that at the time of steady state. At this time, since the impedance of the semiconductor element 16 is controlled so that a current inversely proportional to the magnitude of the load current flows, the amount of generated heat increases. That is, in this circuit, when the heat generation of the switching semiconductor element 5, the rectifying element 6 and the flywheel diode 7 is large, the heat generation of the semiconductor element 16 is almost zero, and conversely the switching semiconductor element 5, the rectifying element 6 and the flywheel. When the heat generation of the diode 7 is small, the heat generation of the semiconductor element 16 is large.
[0012]
Accordingly, in the present invention, as shown in FIG. 2 as one embodiment, the semiconductor element 16 is attached to the radiator 20 to which the rectifying element 6 is attached. In FIG. 2, reference numeral 21 denotes a printed circuit board, the rectifying element 6 is soldered to the printed circuit board 21 through the lead wire 6a, and the semiconductor element 16 is soldered to the printed circuit board 21 through the lead wire 16a. Has been. The rectifying element 6 is fixed to the radiator 20 through a heat sink 22 having an L-shaped cross section, and the semiconductor element 16 is fixed to the heat radiator 20 through a heat sink 23 having an L-shaped cross section. Therefore, in this structure, the heat generated by the rectifying element 6 is transmitted to the radiator 20 through the L-shaped radiator plate 22 and radiated, and the heat generated by the semiconductor element 16 is transmitted to the radiator 20 through the L-shaped radiator plate 23. Is dissipated. As described above, the semiconductor element 16 generates heat only when the load current is equal to or less than the set value. During this period, the current flowing through the rectifying element 6 is small, and thus the heat generation is also small. It can be as much as when it is attached alone. In other words, it is not necessary to prepare a separate heatsink or increase the heatsink by the amount of heat generated by the semiconductor element 16, so that not only is the power supply smaller and more economical, but the load current is reduced below the set value. Unless otherwise, the semiconductor element 16 is off, so that power efficiency can be improved.
[0013]
Note that the rectifying element 6 and the semiconductor element 16 are attached to the heat radiating plates 22 and 23 having L-shaped cross sections through unillustrated electrical insulating sheets having good heat conduction. Moreover, although the example which attaches the rectifier 6 and the semiconductor element 16 to the heat radiator 20 was described together, in addition to the rectifier 6 and the semiconductor element 16, both the switching semiconductor element 5 and the flywheel diode 7 or Either one may be attached to the radiator 20 together. In this case, it corresponds to the maximum heat generation amount of the rectifying element 6 attached to the radiator 20, the maximum heat generation amount of both the switching semiconductor element 5 and the flywheel diode 7, or the sum of the heat generation amounts of either one. Use a radiator with heat dissipation capability.
[0014]
Next, FIG. 3 is a diagram showing an example of a circuit configuration of a chopper type power supply for applying the present invention. In FIG. 3, the same symbols as those shown in FIG. 1 indicate corresponding members, 31 and 32 are resistors for dividing the load voltage between the output terminals 14 and 15, and the resistor 32 is the output voltage. Acts as a sensing resistor. A main control circuit 33 controls the pulse width of the switching semiconductor element 5 so that the load voltage between the output terminals 14 and 15 is constant. Also in this circuit, as in the circuit of FIG. 1, the semiconductor element 16 is held in the OFF state by the control circuit 13 when the load current is in a steady state. When the load current is reduced to a light load state, that is, the current value just before the smoothing inductor 8 is cut off, the control circuit 13 causes the voltage across the current detection resistor 12 to become smaller than the reference value. The semiconductor element 16 is controlled so as to exhibit an impedance corresponding to the load current value. At this time, the current flowing through the semiconductor element 16 is about 2% or less of the load current, and the control circuit 13 is configured so that the sum of the load current and the current flowing through the semiconductor element 16 does not cut off the smoothing inductor 8. The element 16 is controlled.
[0015]
Therefore, since the current flowing through the switching semiconductor element 5 at a light load is very small, the heat generation amount is greatly reduced. However, since the semiconductor element 16 operates in an unsaturated state, the heat generation amount of the semiconductor element 16 increases. On the other hand, in a steady state, since the current flowing through the switching semiconductor element 5 is large, the amount of heat generated is also large, but since the semiconductor element 16 is off, the amount of heat generated is substantially zero. From the above, it can be seen that the sum of the amount of heat generated by the switching semiconductor element 5 and the amount of heat generated by the semiconductor element 16 during the entire operation period does not change much regardless of whether the load is steady or light. Therefore, in this embodiment, the semiconductor element 16 is attached to a radiator 20 ′ (indicated by a chain line) having a heat dissipation capability corresponding to the maximum heat generation amount of the switching semiconductor element 5. Therefore, also in this embodiment, a dedicated radiator for dissipating the heat generated by the semiconductor element 16 is unnecessary, and it is not necessary to enlarge the heat dissipator 20 ′ to dissipate the heat generated by the semiconductor element 16. And cost reduction. In addition, you may attach the flywheel diode 7 to radiator 20 '. In this case, a radiator 20 ′ having a heat dissipation capability corresponding to the sum of the maximum heat generation amount of the switching semiconductor element 5 and the maximum heat generation amount of the flywheel diode 7 is used.
[0016]
In the embodiment of FIG. 2, the rectifying element 6 and the semiconductor element 16 which are main heating elements are attached to the same radiator 20 through the respective heat sinks 22 and 23. However, in the embodiment shown in FIG. Main heating elements 40, 41, and 42 such as switching semiconductor elements, rectifying elements, and flywheel diodes in the circuit are attached to the radiator 20 through electrical insulating sheets 43, 44, and 45 having good heat conduction, respectively, and dummy The semiconductor elements 16, 16 ′ that play the role of load resistance are attached to the radiator 20 via normal heat pipes 46. The semiconductor elements 16 and 16 'are also fixed to the heat pipe 46 through electrical insulating sheets 47 and 48 having good heat conduction, respectively. These electrical insulating sheets also enhance the adhesion between the main heating elements 40, 41, and 42 and the radiator 20, or between the semiconductor elements 16, 16 'and the heat pipe 46, and also play a role of increasing heat dissipation.
[0017]
The radiator 20 is fixed to the printed circuit board 49 by screws or the like. Although not shown, the lead terminals of the main heating elements 40, 41, 42 and the semiconductor elements 16, 16 ′ are soldered to the printed circuit board 49. Although not shown, the heat pipe 46 is fixed by a method such as screwing a flange fixed to the tip of the heat pipe 46 to the radiator 20. Also in this embodiment, the semiconductor element 16, via the heat pipe 46, is connected to the radiator 20 having a heat dissipation capability corresponding to the sum of the maximum heat generation amounts of the main heating elements 40, 41, 42 predicted at each time of operation. By attaching 16 ', it is not necessary to unnecessarily increase the size of the heatsink, and the size can be reduced.
[0018]
The present invention is not limited to the above-described embodiment, and may be a full-bridge inverter or a half-bridge inverter having a normal configuration instead of the single-ended inverter shown in FIG. Instead of the converter, a boost converter having a normal configuration may be used. Of course, the converter may be a synchronous rectifier circuit using FETs as rectifier elements and flywheel diodes. Thus, the present invention may be a converter having any configuration having an inductor, and includes a semiconductor element that acts as a dummy load across the DC output terminals of the converter, and the semiconductor element is turned off except during light loads. The semiconductor element may be controlled so as to have an impedance corresponding to the load current when the load is light.
[0019]
【The invention's effect】
As described above, in the present invention, a semiconductor element controlled to have an impedance commensurate with the load current at a light load is set to a switching semiconductor element, a rectifier element, and a flywheel of a converter circuit. Since it is attached to the radiator together with at least one of the main heating elements such as diodes, the heatsink of the semiconductor element can be omitted without increasing the size of the radiator, and the power supply device can be reduced in size and cost. Can be achieved.
[Brief description of the drawings]
FIG. 1 is a diagram showing an example of a power supply circuit to which the present invention is applied.
FIG. 2 is a diagram showing a configuration for explaining the present invention.
FIG. 3 is a diagram showing another example of a power supply circuit to which the present invention is applied.
FIG. 4 is a diagram showing a configuration for explaining the present invention.
FIG. 5 is a diagram illustrating an example of a conventional power supply device.
[Explanation of symbols]
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1, 2 ... Input terminal 3 ... Capacitor 4 ... Transformer 5 ... Switching semiconductor element 5 ... Filament transformer 6 ... Rectifier 7 ... Flywheel diode 8 ... Smoothing Inductor 9 ... Smoothing capacitor 12 ... Current detection resistor 13 ... Control circuit 14, 15 ... Output terminal 16 ... Semiconductor element (dummy load)
21 ... Printed circuit board 31, 32 ... Output voltage dividing resistor 33 ... Main control circuit 40, 41, 42 ... Main heating element 43, 44, 45, 47, 48 ... Electrical insulation -G 46 ... Heat pipe 49 ... Printed circuit board

Claims (1)

入力電源側から負荷に供給される電力を調整するスイッチング半導体素子、整流素子、フライホイール素子のような主発熱素子と、平滑用インダクタと平滑用コンデンサとからなる平滑回路とで構成されたコンバータ回路と、
該コンバータ回路の出力端子間に跨がって接続された半導体素子と、
負荷電流が減少するとき前記半導体素子を抵抗素子として動作させるよう制御する制御回路とを備え、
前記制御回路は、負荷電流が設定値よりも小さくなったとき前記半導体素子にオン信号を与え、負荷電流値に見合ったインピーダンスを呈するように抵抗素子として前記半導体素子を制御し、負荷電流が設定値以上の場合には前記半導体素子をオフ状態で保持させる電源装置において、
前記主発熱素子の一つ以上と前記半導体素子とが断面Ｌ字状の放熱板又はヒートパイプを介し、前記主発熱素子の最大発熱量に対応する放熱能力をもつ放熱器に一緒に取り付けたことを特徴とする電源装置。 A converter circuit comprising a main heating element such as a switching semiconductor element, a rectifier element, and a flywheel element for adjusting power supplied to a load from the input power source side, and a smoothing circuit including a smoothing inductor and a smoothing capacitor. When,
A semiconductor element connected across the output terminals of the converter circuit;
A control circuit for controlling the semiconductor element to operate as a resistance element when a load current decreases ,
The control circuit gives an ON signal to the semiconductor element when the load current becomes smaller than a set value, controls the semiconductor element as a resistance element so as to exhibit an impedance corresponding to the load current value, and the load current is set In a power supply device that holds the semiconductor element in an off state when the value is equal to or greater than the value,
One or more of the main heating elements and the semiconductor element are attached together with a radiator having a heat radiation capacity corresponding to the maximum heat generation amount of the main heating element via a heat sink or heat pipe having an L-shaped cross section. A power supply characterized by.
JP2001308162A 2001-10-04 2001-10-04 Power supply Expired - Fee Related JP3610382B2 (en)

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JP2006333676A (en) * 2005-05-30 2006-12-07 Omron Corp Current compensating circuit and power supply having the same
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