【０００１】
【発明の属する技術分野】
本発明は、交流電源半周期に１回もしくは複数回の短絡動作を行って、電源の力率改善を行う電力変換装置に係り、特に、整流回路を全波整流回路から倍電圧整流回路に切替える手段を備えた電力変換装置に関する。
【０００２】
【従来の技術】
従来技術の電源装置では、電源の力率を改善するために電源半周期に１回もしくは複数回の短絡動作を行い、さらに整流回路を全波整流回路または倍電圧整流回路に切替える手段を備えている。この整流回路を全波整流回路から倍電圧整流回路へと切替える際、平滑コンデンサへの充電電流が電源から急激に流れ、同時に直流電圧が急上昇する。このように急激な電流と直流電圧の急上昇は、負荷に影響を与えるだけでなく、リアクトル，短絡手段，整流回路，平滑コンデンサ等の各素子の寿命などにも影響を与える。そのため、整流回路を切替える際の過渡状態を制御する必要がある。
【０００３】
特開平１１−２０６１３０号公報に記載されている電源装置は、整流回路を全波整流回路から倍電圧整流回路へと切替える場合に、電源装置の出力電圧が倍電圧整流回路に切替えた後に得られる出力電圧値になるように短絡時間を制御して、全波整流回路から倍電圧整流回路に切替えた際の直流電圧変動を抑制している。
【０００４】
【発明が解決しようとする課題】
前記特開平１１−２０６１３０号公報に記載の従来技術は、整流回路を全波整流回路から倍電圧整流回路へと切替えた後に得られる出力電圧値のみを用いて短絡時間を制御していて、装置の入力電流の変動は配慮していない。すなわち、整流回路を切替える場合には、直流電圧の変動を抑制するとともに、装置への入力電流の変動を抑制することも必要である。また、前記従来技術には電源変動に対する配慮もない。
【０００５】
本発明の目的は、整流回路を全波整流回路から倍電圧整流回路へ切替える場合に、直流電圧の変動を抑制し、かつ装置入力電流変動を抑制した電力変換装置の提供と、電源の電圧変動に対応した全波整流回路から倍電圧整流回路への切替方法の提供である。
【０００６】
【課題を解決するための手段】
本発明の電源装置は、整流回路切替手段が整流回路を全波整流回路から倍電圧整流回路に切替える場合、全波整流回路の状態で整流回路切替移行期間を設け、この整流回路切替移行期間内の短絡動作方法を、この移行期間前とは異なる方法で行う。
【０００７】
▲１▼本発明の電源装置は、倍電圧整流回路に切替える前に必要最低電圧値まで直流電圧を昇圧して、整流回路を全波整流回路から倍電圧整流回路に切替える際の直流電圧の急変動と電源電流のピーク値を下げる。
【０００８】
本発明の電源装置では、直流電圧の昇圧を、▲２▼短絡時間を長くする方法、もしくは▲３▼交流電源の半周期に複数回短絡動作する方法の何れかで行う。
【０００９】
整流回路を切替える前に昇圧する必要最低電圧値は、入力電力と電源電圧等の条件で異なるので、本発明の電源装置では、▲４▼電力変換装置の出力直流電圧、または電源電圧、または電力変換装置の入力電流、または入力電力、または出力電力の少なくとも一つを用いて、短絡時間、または短絡回数、または短絡時間と短絡休止期間の比率を制御して直流電圧を昇圧し、切替えの際の直流電圧の急変動と電源電流のピーク値とを下げる。
【００１０】
本発明の電源装置では、▲５▼切替え直前と切替え直後との交流電源に流れる電流のピーク値の差を２０％以内にするように、短絡時間、または短絡回数、または短絡時間と短絡休止期間の比率を制御し、全波整流回路から倍電圧整流回路に切替える際の直流電圧の変動を抑制し、電源電流のピーク値を下げる。
【００１１】
本発明の電源装置では、▲６▼整流回路の切替えを交流電源のゼロクロスのタイミングの近傍で行うので交流電源の電流が小さく整流回路切替手段５への影響を最小限にできる。もし、整流回路切替手段に動作遅れがある場合には、▲７▼ゼロクロスから整流回路切替手段が動作するまでの間に１回もしくは複数回短絡動作をして切替え前に昇圧した直流電圧の低下を防ぎ、直流電圧の変動を抑制する。
【００１２】
【発明の実施の形態】
以下、本発明の実施例を図面を用いて詳しく説明する。
【００１３】
（実施例１）
図１は、本実施例の電力変換装置１００を用いたモータ制御装置１０１の基本構成図である。図１に示すように、電力変換装置１００は、交流電源１の一方の出力端に一端が接続したリアクトル２と、そのリアクトル２を介して交流電源１を短絡する短絡手段３と、交流電源１に接続されていない側のリアクトル２の他端とリアクトル２が接続されていない側の交流電源１の他端を交流入力とする整流回路４と、整流回路４の直流出力の両端に直列接続した平滑コンデンサ６と、整流回路４の交流入力の一方と平滑コンデンサ６を構成する平滑コンデンサ６１と平滑コンデンサ６２との接続点の間に接続した整流回路切替手段５と、交流電源１のゼロクロスを検出するゼロクロス検出回路８と、前記平滑コンデンサ６の直流電圧Ｖｄを入力しゼロクロス信号９２を基準タイミングとして短絡手段３へ短絡動作させる短絡パルス信号９６を出力するとともに、整流回路切替手段５に整流回路切替信号９７を出力する制御回路７と、前記交流電源１から入力される入力電流Ｉｓを検出し前記制御回路７に入力電流値９８を出力する入力電流検出回路３０とを備えている。
【００１４】
図１に前記電力変換装置１００の直流出力に接続したインバータ回路１０と電動機を内蔵した圧縮機２０を合わせて示す。本実施例の制御回路７は、例えばマイクロコンピュータ等の半導体集積回路で構成しており、全ての動作をソフトウエアで処理している。
【００１５】
ゼロクロス検出回路８は、交流電源１の両端の電圧を入力し、交流電源１の交流電圧（電源電圧Ｖｓと略記する。）がゼロクロス点を通過し極性が変わるタイミングで、Ｈｉｇｈ信号からＬｏｗ信号、もしくはＬｏｗ信号からＨｉｇｈ信号に切替わるゼロクロス信号９２を出力し、このゼロクロス信号９２を制御回路７へ入力する。
【００１６】
制御回路７は、入力したゼロクロス信号９２の立ち上がり、もしくは立ち下がりを基準タイミングとして、そこから短絡手段３が短絡動作を開始するまでの期間（ディレイ時間Ｔｄと略記する。）と短絡する時間（パルス幅Ｔｗと略記する。）を設定し、短絡パルス信号９６（Ｈｉｇｈ，Ｌｏｗ信号）を短絡手段３に出力する。ディレイ時間Ｔｄとパルス幅Ｔｗとは、制御回路７に記憶したり、制御回路７で計算で求める。
【００１７】
短絡手段３は短絡パルス信号９６に従って短絡開閉動作する。本実施例では、制御回路７が出力する短絡パルス信号９６がＨｉｇｈの時に、短絡手段３が短絡動作する。短絡手段３は、ダイオードブリッジと、ＩＧＢＴ，バイポーラトランジスタ，パワーＭＯＳＦＥＴなどの電力半導体スイッチング素子とを備えており、短絡パルス信号９６に従って、リアクトル２を介して交流電源１を短絡する。
【００１８】
整流回路切替手段５は、パワーリレー，トライアック，ダイオードブリッジと電力半導体スイッチング素子（ＩＧＢＴ，バイポーラトランジスタ，パワー
ＭＯＳＦＥＴ）の組み合わせなどの双方向スイッチで構成され、制御回路７が出力する整流回路切替信号９７（Ｈｉｇｈ，Ｌｏｗ信号）を受けて整流回路４を切替える。本実施例では、整流回路切替信号９７がＬｏｗ信号のときに整流回路４を全波整流回路に切替え、Ｈｉｇｈ信号の場合に倍電圧整流回路に切替える。
【００１９】
制御回路７は、平滑コンデンサ６の両端の直流電圧Ｖｄや入力電流値９８を入力し、短絡パルス信号９６の制御と整流回路切替信号９７を出力する。
【００２０】
本実施例の電源装置では、交流電源１を電源半周期につき一回もしくは複数回，リアクトル２を介して短絡手段３が短絡動作し、交流電源１の電流（以下、入力電流Ｉｓと略記する。）の通流角を広げ電源の力率を改善しながら、交流電力を直流電力に変換する。本実施例の電力変換装置１００では、整流回路切替手段５によって、整流回路４を全波整流回路と倍電圧整流回路の両方の動作ができるので、パルス幅Ｔｗで直流電圧Ｖｄを所定の値に制御するだけでなく、幅広い範囲の直流電圧Ｖｄを出力できる。
【００２１】
整流回路４を全波整流回路から倍電圧整流回路に切替える際の各部の動作波形を図２に示す。図２においてｔ＝Ｔ１以前の電源１周期では、電力変換装置１００が全波整流回路で運転し、短絡手段３が交流電源１の電源電圧Ｖｓの半周期に１回短絡動作して強制的に電流を流して力率を改善している。図２の入力電流Ｉｓの波形に示すように、短絡動作していないときの入力電流Ｉｓの波形に比べ、通流角が広くなり力率を改善している。この期間の短絡パルス信号９６のディレイ時間Ｔｄとパルス幅Ｔｗは、制御回路７に予め記憶されている値である。制御回路７に入力した直流電圧Ｖｄ、もしくは入力電流Ｉｓ、もしくは電力変換装置
１００の出力電流などから、ディレイ時間Ｔｄとパルス幅Ｔｗとを演算で決定することもできる。なお、電源電圧Ｖｓの半周期に複数回の短絡動作しても力率改善動作はできる。
【００２２】
ここで、切替移行期間なしで、整流回路４を全波整流回路から倍電圧整流回路に切替えると、平滑コンデンサ６への充電電流である入力電流Ｉｓが急激に流れ、同時に直流電圧Ｖｄが急上昇する。
【００２３】
先に示す特開平１１−２０６１３０号公報に記載の従来技術では、切替移行期間（図２のｔ＝Ｔ１からＴ２までの期間）のある時点で、倍電圧整流回路に切替えた後に得られる電圧値までパルス幅Ｔｗを制御して昇圧している。直流電圧
Ｖｄを昇圧した場合、切替前後での直流電圧Ｖｄの変動は小さいが、倍電圧整流回路に切替えた後に得られる電圧値まで急に昇圧するために、全波整流回路で力率改善動作していたときのパルス幅Ｔｗより広いパルス幅Ｔｗで動作するので、入力電流Ｉｓのピーク値が大きくなる。このように、特開平１１−２０６１３０号公報に記載の従来技術では、切替え直後の入力電流Ｉｓのピーク値は下がるが、切替える直前までの入力電流Ｉｓのピーク値が大きくなる。反対に、切替える前の昇圧が十分でない場合には、切替える直前までの入力電流Ｉｓのピーク値は小さいが切替えた直後の入力電流Ｉｓのピーク値が高くなる。
【００２４】
本実施例では、図２に示すように、短絡パルス信号のパルス幅Ｔｗを、切替移行期間に入ると、切替移行時点Ｔ１以前のパルス幅Ｔｗを徐々に広げる制御を行い、切替える直前と直後の入力電流Ｉｓのピーク値が、ほぼ同じになる電圧値まで昇圧する。これにより入力電流Ｉｓのピーク値を低減すると同時に直流電圧
Ｖｄの急変動を防止する。
【００２５】
切替え直前と直後との入力電流Ｉｓのピーク値の変化分は、素子のばらつき，電源事情，ゼロクロス検出回路８の検出誤差等を考えると、０〜２０％の範囲であればよい。また、切替える直前と直後の入力電流Ｉｓのピーク値が同じになる電圧値まで昇圧するディレイ時間Ｔｄとパルス幅Ｔｗの値とは、シミュレーションもしくは実験で予め求めて、制御回路７に設定する。
【００２６】
本実施例で示すように、切替え直前と直後との入力電流Ｉｓのピーク値の変化分を０〜２０％の範囲にすると、切替移行期間に昇圧する電圧値は、倍電圧整流回路に切替えた後に得られる電圧値より小さい電圧値で済む。この理由は、倍電圧整流回路に切替えた際に流れる充電電流によって昇圧されるためである。
【００２７】
切替える前に直流電圧Ｖｄを昇圧する必要最低値は、切替える際の入力電力や電源電圧Ｖｓ等の条件で異なる。
【００２８】
全波整流回路から倍電圧整流回路への切替えを行うときのパルス幅Ｔｗの変化を、図３を用いて説明する。図３の横軸は時刻、縦軸はパルス幅Ｔｗである。図３は、全波整流回路で短絡手段３が力率改善動作を行っているときから、切替移行期間を経て倍電圧整流回路に切替える直前までを示す。但し、実際のパルス幅Ｔｗは、図中の縦の点線で示す電源周期の半周期ごとに階段状に変化するが、図３では説明の都合上、直線で示す。
【００２９】
図３に、切替移行期間前の全波整流回路運転時のパルス幅Ｔｗを、入力電力の大小に応じて制御する場合と、切替移行期間前の全波整流回路運転時のパルス幅Ｔｗを固定値とする場合の３つ場合の制御方法を示す。さらに、図３の切替移行期間では、前記３つの制御方法に対して、それぞれ電源電圧Ｖｓが、８０％と、１００％と、１２０％との場合のパルス幅Ｔｗの変化を示す。また、パルス幅
Ｔｗが固定値の場合では、入力電力の大きさが異なる３つの場合のパルス幅Ｔｗの変化も合わせて示す。図３で、切替移行期間の最終時点（ｔ＝Ｔ２）におけるパルス幅Ｔｗｂが、倍電圧整流回路に切替える際に必要な最小限の直流電圧Ｖｄを発生させるためのパルス幅である。
【００３０】
図３に示すように切替移行期間に入る最初のパルス幅Ｔｗは、切替移行期間に入る前のパルス幅Ｔｗから始まり、切替移行期間に入ると、そのときの負荷の大きさに応じてパルス幅Ｔｗを増加していく。本実施例では入力電力の大小と電源電圧Ｖｓの大きさによりパルス幅Ｔｗを変化している。
【００３１】
移行期間前のパルス幅Ｔｗが固定の場合を例に説明する。切替移行期間前はパルス幅Ｔｗは入力電力等で変化しないが、切替移行期間に入ると入力電力の大きさと電源電圧Ｖｓとにより変化する。パルス幅Ｔｗは、図３に示すように、入力電力が小さいときは直線Ａ、入力電力が基準値の場合は直線Ｂ、入力電力が大きい場合は直線Ｃとなる。このように本実施例の電力変換装置では入力電力の大きさ、すなわち負荷の大きさに応じて切替移行期間にパルス幅Ｔｗを変化させる傾きを変え、切替時の直流電圧Ｖｄの急変動を抑えかつ入力電流Ｉｓのピークを低減する。
【００３２】
電源電圧Ｖｓが変動すると、直流電圧Ｖｄも変動するので、整流回路４を切替える前に昇圧する電圧の必要最低値も変動する。本実施例の電源装置では、電源電圧Ｖｓの値は、短絡パルス信号９６のディレイ時間Ｔｄとパルス幅Ｔｗが同じであれば、全波整流回路時や倍電圧整流回路時に得られる直流電圧Ｖｄの値の変動は電源電圧Ｖｓの変動にほぼ比例する。そこで、直流電圧Ｖｄを制御回路７に入力して電源電圧Ｖｓの変動を求めておく。
【００３３】
電源電圧Ｖｓが変動した場合の昇圧パルス幅Ｔｗｂの決定方法を図４を用いて説明する。図４の横軸は電源電圧Ｖｓを示し、縦軸は昇圧パルス幅Ｔｗｂを示す。図４では、電源電圧Ｖｓが±２０％変動した場合の昇圧パルス幅Ｔｗｂの決定方法を示す。基準となる電源電圧Ｖｓ（１００％）に対応する昇圧パルス幅Ｔｗｂ（１００％）から、電源電圧Ｖｓの変動に応じて昇圧パルス幅Ｔｗｂを増減し、切替え前に昇圧する電圧値を変更する。例えば、電源電圧Ｖｓが基準値の１２０％の場合には、昇圧パルス幅Ｔｗｂを基準値の９７％に設定する。この理由は、電源電圧Ｖｓが高くなったので、倍電圧整流時の直流電圧Ｖｄも大きくなるが、倍電圧整流回路に切替えた際に流れる充電電流も大きくなり、充電電流による昇圧も大きくなる。そのために、電源電圧Ｖｓが高くなった場合は、昇圧パルス幅Ｔｗｂを基準値より狭くする。電源電圧Ｖｓが基準値の８０％の場合は、逆に充電電流が減るために昇圧幅が小さくなるので、昇圧パルス幅Ｔｗｂを基準値の
１０３％に設定する。
【００３４】
図４に示すように、電源電圧Ｖｓの増加に対して昇圧パルス幅Ｔｗｂは単調減少し、単調減少関数の傾きは電源変換装置の回路定数や電源電圧Ｖｓの大きさに依存する。図４の電源電圧Ｖｓと昇圧パルス幅Ｔｗｂとの関係を図３に適用すると、図３に一点鎖線で示すようになり、電源電圧Ｖｓが大きい時に、パルス幅
Ｔｗを小さい値にする。本実施例の電力変換装置では、負荷の変動に応じて図３に示す実線の傾きを変え、電源電圧Ｖｓの変動に応じて図３の実線と一点鎖線に示すようにパルス幅Ｔｗを調整するので、入力電力の変動と電源電圧Ｖｓの変動の両方に対応できる。
【００３５】
次に、整流回路４を全波整流回路から倍電圧整流回路に切替えるタイミングと短絡動作のタイミングとを説明する。整流回路４が切替わると、少なくとも交流電源１の半周期以上に渡って平滑コンデンサ６へ充電電流が流れる。充電電流が流れている間に短絡手段３が短絡動作すると直流電圧Ｖｄが大きく上昇し、整流回路４を切替えるときにオーバーシュートを生じるので、本実施例の電源装置は充電電流が流れている間、つまり、整流回路切替手段５が倍電圧整流回路に切替えてから電源電圧Ｖｓの少なくとも半周期以上の期間は短絡動作を停止する。また、電源電圧Ｖｓのゼロクロス付近で整流回路４を切替えると電力変換装置１００への入力電流Ｉｓが小さく、整流回路切替手段５が受ける影響も小さいので、整流回路切替信号９７を、ゼロクロス信号９２の立ち上がりもしくは立ち下がりと同タイミングでＬｏｗからＨｉｇｈに切替える。
【００３６】
しかし、現実には整流回路切替手段５が動作するのは瞬間的でなく遅れが生じ、たとえば、パワーリレー等機械的スイッチ回路では、遅れが数ｍｓｅｃ 以上になる。このように整流回路４が切替わるまでに遅れがある場合に整流回路切替信号９７と同時に短絡動作を中止すると、切替直前までに昇圧した直流電圧Ｖｄが低下する。昇圧した直流電圧Ｖｄが低下すると、整流回路４が切替わった直後の入力電流Ｉｓのピーク値が大きくなる。そのため、本実施例の電力変換装置は、切替え遅れがある場合には、整流回路切替信号９７がＬｏｗからＨｉｇｈに切替わった後から整流回路切替手段５が動作するまでの間に短絡動作を１回もしくは複数回行い、昇圧した電圧の低下を防ぐ。
【００３７】
（実施例２）
本実施例について図５を用いて説明する。図５は、短絡手段３が短絡動作しない場合にｔ＝Ｔ３から流れ始めている入力電流の波形と、ｔ＝Ｔ３以前から複数パルスのチョッピングによる短絡動作を始める場合（破線）と、ｔ＝Ｔ３以後から複数パルスでチョッピングによる短絡動作を始める場合（実線）との、入力電流Ｉｓと直流電圧Ｖｄとを示す。図５の実線に示すようにチョッピングによる短絡動作を、ｔ＝Ｔ３以後の位相から開始すると、リアクトル２に流れる電流が連続となり効率よく昇圧ができ、入力電流Ｉｓのピーク値を低減できる。一方、ｔ＝Ｔ３より以前の位相でチョッピングをする場合は、点線で示すように直流電圧Ｖｄを高くできない。
【００３８】
チョッピング周波数は、交流電源１の周波数の１０〜１００倍程度が良い。説明のために図５のパルスのデューティ比を５０％で示してあるが、リアクトル２に流れる電流が連続であればデューティ比は５０％以外でもよい。
【００３９】
本実施例では、電源電圧Ｖｓの半周期に行う短絡動作の回数と、短絡パルス信号９６のデューティ比とによって直流電圧Ｖｄを制御できる。また、切替移行期間に短絡動作の回数を徐々に増すことで、直流電圧Ｖｄも徐々に上昇することができ、電力変換装置１００を構成する素子と平滑コンデンサ６に与えるストレスを低減できる。
【００４０】
本実施例も実施例１と同様に、電力変換装置１００の負荷と電源電圧Ｖｓに変動があった場合は、切替え前に直流電圧Ｖｄを昇圧する必要最低値を変更する。本実施例では、実施例１の図３と図４の縦軸のパルス幅を短絡動作の回数または短絡パルス信号９６のデューティに置き換えれば実施例１と同様の効果を得られる。
【００４１】
図２に、本実施例の波形を併せて示す。図２中の短絡パルス信号９６で、黒く塗りつぶした波形は、拡大図に示すように高い周波数でチョッピングする信号である。本実施例では、高い周波数のチョッピング信号で制御しているので、制御応答が高く、切替移行期間終了前後の入力電流Ｉｓ波高値が小さい。本実施例では、整流回路４や短絡手段３が高速ダイオード（ファーストリカバリーダイオード）を備えている電力変換装置に特に有効である。
【００４２】
（実施例３）
本実施例について図６を用いて説明する。本実施例は、切替移行期間中に、電源電圧Ｖｓの半周期あたり複数回の短絡動作をするが、リアクトル２に流れる短絡電流が一回ゼロか、ゼロ近くになった後に、図６の短絡パルス信号９６に示すように、２回目以降の短絡動作をする。言い換えると、ダイオードに流れるリカバリー電流が０になりダイオードがいったんターンオフした後に２回目以降の短絡動作する。これにより、入力電流Ｉｓのピーク値を低減し、直流電圧Ｖｄの急変動も抑制する。本実施例は低速ダイオードを用いた電源装置に好適である。
【００４３】
【発明の効果】
以上説明したように、本発明の電力変換装置によれば、短絡パルス幅とパルス数を制御して、全波整流回路から倍電圧整流回路に切替える際の直流電圧の変動を抑制し、入力する交流電流のピーク値を下げることができる。
【図面の簡単な説明】
【図１】実施例１の電力変換装置の構成を示す説明図。
【図２】実施例１，実施例２の電力変換装置の各部の波形の説明図。
【図３】実施例１の電力変換装置で整流回路を切替える際のパルス幅変化の説明図。
【図４】実施例１で、電源電圧変動時の短絡パルス幅の決定する方法の説明図。
【図５】実施例２で、複数回短絡動作させる際の短絡動作開始タイミングの説明図。
【図６】実施例３の電力変換装置の各部の波形の説明図。
【符号の説明】
１…交流電源、２…リアクトル、３…短絡手段、４…整流回路、５…整流回路切替手段、６…平滑コンデンサ、７…制御回路、８…ゼロクロス検出回路、１０…インバータ回路、２０…圧縮機、３０…入力電流検出回路、９２…ゼロクロス信号、９６…短絡パルス信号、９７…整流回路切替信号、１００…電力変換装置、Ｔｗ…パルス幅、Ｔｄ…ディレイ時間、Ｖｄ…直流電圧、Ｉｓ…入力電流。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a power converter that performs a short-circuit operation once or a plurality of times in a half cycle of an AC power supply to improve a power factor of a power supply, and in particular, switches a rectifier circuit from a full-wave rectifier circuit to a voltage doubler rectifier circuit. The present invention relates to a power conversion device provided with means.
[0002]
[Prior art]
The power supply device of the related art is provided with means for performing one or more short-circuiting operations in a power supply half cycle to improve the power factor of the power supply, and further switching the rectifier circuit to a full-wave rectifier circuit or a voltage doubler rectifier circuit. I have. When this rectifier circuit is switched from a full-wave rectifier circuit to a voltage doubler rectifier circuit, a charging current to a smoothing capacitor flows rapidly from a power supply, and at the same time, a DC voltage rises sharply. Such a sudden increase in current and DC voltage not only affects the load, but also affects the life of each element such as a reactor, short-circuit means, a rectifier circuit, and a smoothing capacitor. Therefore, it is necessary to control a transient state when switching the rectifier circuit.
[0003]
The power supply device described in JP-A-11-206130 is obtained after switching the output voltage of the power supply device to the voltage doubler rectifier circuit when switching the rectifier circuit from the full wave rectifier circuit to the voltage doubler rectifier circuit. The short-circuit time is controlled so that the output voltage value is obtained, thereby suppressing the DC voltage fluctuation when switching from the full-wave rectifier circuit to the voltage doubler rectifier circuit.
[0004]
[Problems to be solved by the invention]
In the prior art described in Japanese Patent Application Laid-Open No. 11-206130, the short-circuit time is controlled using only the output voltage value obtained after switching the rectifier circuit from the full-wave rectifier circuit to the voltage doubler rectifier circuit. The input current fluctuation is not considered. That is, when the rectifier circuit is switched, it is necessary to suppress the fluctuation of the DC voltage and the fluctuation of the input current to the device. In addition, the prior art does not take power fluctuation into consideration.
[0005]
SUMMARY OF THE INVENTION An object of the present invention is to provide a power converter that suppresses fluctuations in DC voltage and fluctuations in device input current when switching a rectifier circuit from a full-wave rectifier circuit to a voltage doubler rectifier circuit, The present invention provides a method for switching from a full-wave rectifier circuit to a voltage doubler rectifier circuit corresponding to the above.
[0006]
[Means for Solving the Problems]
When the rectifier circuit switching means switches the rectifier circuit from the full-wave rectifier circuit to the voltage doubler rectifier circuit, the power supply device of the present invention provides a rectifier circuit switch transition period in the state of the full-wave rectifier circuit, Is performed by a method different from that before the transition period.
[0007]
(1) The power supply device of the present invention boosts the DC voltage to the required minimum voltage value before switching to the voltage doubler rectifier circuit, and rapidly changes the DC voltage when switching the rectifier circuit from the full-wave rectifier circuit to the voltage doubler rectifier circuit. Reduce the fluctuation and the peak value of the power supply current.
[0008]
In the power supply device of the present invention, the DC voltage is boosted by either (2) a method of extending the short-circuit time or (3) a method of performing the short-circuit operation a plurality of times in a half cycle of the AC power supply.
[0009]
Since the required minimum voltage value to be boosted before switching the rectifier circuit varies depending on conditions such as the input power and the power supply voltage, the power supply of the present invention requires (4) the output DC voltage of the power converter or the power supply voltage or the power supply. Using at least one of the input current, input power, or output power of the converter, the short-circuit time, the number of short-circuits, or the ratio between the short-circuit time and the short-circuit rest period is controlled to boost the DC voltage and perform switching. Of the DC voltage and the peak value of the power supply current.
[0010]
In the power supply device of the present invention, (5) the short-circuit time or the number of short-circuits, or the short-circuit time and the short-circuit pause period, so that the difference between the peak values of the current flowing in the AC power supply immediately before and immediately after the switching is within 20%. , The fluctuation of the DC voltage when switching from the full-wave rectifier circuit to the voltage doubler rectifier circuit is suppressed, and the peak value of the power supply current is reduced.
[0011]
In the power supply device of the present invention, (6) the rectifier circuit is switched near the zero-cross timing of the AC power supply, so that the current of the AC power supply is small and the influence on the rectifier circuit switching means 5 can be minimized. If there is a delay in the operation of the rectifier circuit switching means, {circle around (7)} one or more short-circuit operations between zero crossing and the operation of the rectifier circuit switching means, and a drop in the DC voltage boosted before switching. To prevent DC voltage fluctuations.
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0013]
(Example 1)
FIG. 1 is a basic configuration diagram of a motor control device 101 using the power conversion device 100 of the present embodiment. As shown in FIG. 1, a power conversion device 100 includes a reactor 2 having one end connected to one output terminal of an AC power supply 1, a short-circuit unit 3 for short-circuiting the AC power supply 1 via the reactor 2, A rectifier circuit 4 having the other end of the reactor 2 not connected to the reactor and the other end of the AC power supply 1 not connected to the reactor 2 as an AC input, and a rectifier circuit 4 connected in series to both ends of a DC output thereof. Smoothing capacitor 6, rectifier circuit switching means 5 connected between a connection point between one of the AC inputs of rectifier circuit 4 and smoothing capacitor 61 and smoothing capacitor 62 constituting smoothing capacitor 6, and detection of zero crossing of AC power supply 1 And a short-circuit pulse signal 96 for inputting the DC voltage Vd of the smoothing capacitor 6 and short-circuiting the short-circuit means 3 using the zero-cross signal 92 as a reference timing. A control circuit 7 that outputs a rectification circuit switching signal 97 to the rectification circuit switching means 5 and an input that detects an input current Is input from the AC power supply 1 and outputs an input current value 98 to the control circuit 7 And a current detection circuit 30.
[0014]
FIG. 1 shows an inverter circuit 10 connected to the DC output of the power converter 100 and a compressor 20 having a built-in electric motor. The control circuit 7 of the present embodiment is constituted by a semiconductor integrated circuit such as a microcomputer, for example, and all operations are processed by software.
[0015]
The zero-crossing detection circuit 8 inputs the voltage at both ends of the AC power supply 1 and, at the timing when the AC voltage (abbreviated as power supply voltage Vs) of the AC power supply 1 passes through the zero-cross point and changes the polarity, changes from a High signal to a Low signal, Alternatively, it outputs a zero-cross signal 92 that switches from a Low signal to a High signal, and inputs this zero-cross signal 92 to the control circuit 7.
[0016]
The control circuit 7 uses the rising or falling edge of the input zero-cross signal 92 as a reference timing to start a short-circuiting operation of the short-circuiting means 3 (abbreviated as delay time Td) and a short-circuiting time (pulse). The width Tw is abbreviated.), And a short-circuit pulse signal 96 (High, Low signal) is output to the short-circuit means 3. The delay time Td and the pulse width Tw are stored in the control circuit 7 or calculated by the control circuit 7.
[0017]
The short-circuit means 3 performs a short-circuit opening / closing operation according to the short-circuit pulse signal 96. In this embodiment, when the short-circuit pulse signal 96 output from the control circuit 7 is High, the short-circuit means 3 performs a short-circuit operation. The short-circuit means 3 includes a diode bridge and a power semiconductor switching element such as an IGBT, a bipolar transistor, and a power MOSFET, and short-circuits the AC power supply 1 via the reactor 2 according to the short-circuit pulse signal 96.
[0018]
The rectifier circuit switching means 5 is constituted by a bidirectional switch such as a combination of a power relay, a triac, a diode bridge and a power semiconductor switching element (IGBT, bipolar transistor, power MOSFET), and the rectifier circuit switching signal 97 output by the control circuit 7. The rectifier circuit 4 is switched in response to the (High, Low signal). In the present embodiment, the rectifier circuit 4 is switched to a full-wave rectifier circuit when the rectifier circuit switching signal 97 is a low signal, and is switched to a voltage doubler rectifier circuit when the rectifier circuit switching signal 97 is a high signal.
[0019]
The control circuit 7 receives the DC voltage Vd at both ends of the smoothing capacitor 6 and the input current value 98, controls the short-circuit pulse signal 96, and outputs a rectifier circuit switching signal 97.
[0020]
In the power supply device according to the present embodiment, the short-circuiting means 3 short-circuits the AC power supply 1 once or a plurality of times per half cycle of the power supply via the reactor 2, and the current of the AC power supply 1 (hereinafter abbreviated as input current Is). ) Converts AC power to DC power while widening the conduction angle and improving the power factor of the power supply. In the power converter 100 of the present embodiment, the rectifier circuit switching means 5 allows the rectifier circuit 4 to operate as both a full-wave rectifier circuit and a voltage doubler rectifier circuit, so that the DC voltage Vd is set to a predetermined value with the pulse width Tw. In addition to controlling, a wide range of DC voltage Vd can be output.
[0021]
FIG. 2 shows operation waveforms of the respective parts when the rectifier circuit 4 is switched from the full-wave rectifier circuit to the voltage doubler rectifier circuit. In FIG. 2, in one cycle of the power supply before t = T1, the power conversion device 100 operates with the full-wave rectifier circuit, and the short-circuiting means 3 performs a short-circuit operation once in a half cycle of the power supply voltage Vs of the AC power supply 1 to forcibly. The power factor is improved by passing current. As shown in the waveform of the input current Is in FIG. 2, the conduction angle is wider and the power factor is improved as compared with the waveform of the input current Is when no short-circuit operation is performed. The delay time Td and the pulse width Tw of the short-circuit pulse signal 96 during this period are values stored in the control circuit 7 in advance. The delay time Td and the pulse width Tw can be determined by calculation from the DC voltage Vd input to the control circuit 7, the input current Is, the output current of the power conversion device 100, or the like. Note that the power factor improving operation can be performed even if a plurality of short-circuit operations are performed in a half cycle of the power supply voltage Vs.
[0022]
Here, when the rectifier circuit 4 is switched from the full-wave rectifier circuit to the voltage doubler rectifier circuit without the switching transition period, the input current Is, which is the charging current for the smoothing capacitor 6, flows rapidly, and at the same time, the DC voltage Vd rises sharply. .
[0023]
In the prior art described in Japanese Patent Application Laid-Open No. H11-206130, the voltage value obtained after switching to the voltage doubler rectifier circuit at a certain point in the switching transition period (the period from t = T1 to T2 in FIG. 2). The pulse width Tw is controlled until the voltage is increased. When the DC voltage Vd is boosted, the fluctuation of the DC voltage Vd before and after switching is small, but the power factor improving operation is performed by the full-wave rectifying circuit because the voltage is rapidly increased to a voltage value obtained after switching to the voltage doubler rectifying circuit. Since the operation is performed with a pulse width Tw wider than the pulse width Tw when the input current Is is being performed, the peak value of the input current Is increases. As described above, in the related art described in Japanese Patent Application Laid-Open No. H11-206130, the peak value of the input current Is immediately after the switching decreases, but the peak value of the input current Is immediately before the switching increases. Conversely, if the boost before switching is not sufficient, the peak value of the input current Is immediately before switching is small, but the peak value of the input current Is immediately after switching is high.
[0024]
In this embodiment, as shown in FIG. 2, when the pulse width Tw of the short-circuit pulse signal enters the switching transition period, control is performed to gradually increase the pulse width Tw before the switching transition point T1, and immediately before and after the switching. The input current Is is boosted to a voltage value at which the peak value becomes substantially the same. As a result, the peak value of the input current Is is reduced, and at the same time, a sudden change in the DC voltage Vd is prevented.
[0025]
The change in the peak value of the input current Is immediately before and after the switching may be in the range of 0 to 20% in consideration of variations in elements, power supply conditions, detection errors of the zero-cross detection circuit 8, and the like. In addition, the delay time Td and the value of the pulse width Tw for raising the peak value of the input current Is immediately before and after the switching to the same voltage value are obtained in advance by simulation or experiment and set in the control circuit 7.
[0026]
As shown in the present embodiment, when the amount of change in the peak value of the input current Is immediately before and after the switching is in the range of 0 to 20%, the voltage value to be boosted during the switching transition period is switched to the voltage doubler rectifier circuit. A voltage value smaller than a voltage value obtained later is sufficient. The reason for this is that the voltage is boosted by the charging current flowing when switching to the voltage doubler rectifier circuit.
[0027]
The minimum required value for boosting the DC voltage Vd before switching differs depending on conditions such as input power and power supply voltage Vs at the time of switching.
[0028]
The change in the pulse width Tw when switching from the full-wave rectifier circuit to the voltage doubler rectifier circuit will be described with reference to FIG. The horizontal axis in FIG. 3 is time, and the vertical axis is pulse width Tw. FIG. 3 shows the time from when the short-circuit means 3 is performing the power factor improving operation in the full-wave rectifier circuit to immediately before switching to the voltage doubler rectifier circuit via the switching transition period. However, the actual pulse width Tw changes stepwise at every half cycle of the power supply cycle indicated by the vertical dotted line in the figure, but is shown as a straight line in FIG. 3 for convenience of explanation.
[0029]
FIG. 3 shows a case where the pulse width Tw during the operation of the full-wave rectifier circuit before the switching transition period is controlled according to the magnitude of the input power, and a case where the pulse width Tw during the operation of the full-wave rectification circuit before the switching transition period is fixed. The control method in the case of three values will be described. Further, in the switching transition period in FIG. 3, the change in the pulse width Tw when the power supply voltage Vs is 80%, 100%, and 120% is shown for each of the three control methods. Further, when the pulse width Tw is a fixed value, the change of the pulse width Tw in three cases where the magnitude of the input power is different is also shown. In FIG. 3, the pulse width Twb at the end of the switching transition period (t = T2) is a pulse width for generating the minimum DC voltage Vd required for switching to the voltage doubler rectifier circuit.
[0030]
As shown in FIG. 3, the initial pulse width Tw in the switching transition period starts from the pulse width Tw before entering the switching transition period, and in the switching transition period, the pulse width Tw depends on the load at that time. Tw is increased. In this embodiment, the pulse width Tw is changed depending on the magnitude of the input power and the magnitude of the power supply voltage Vs.
[0031]
An example in which the pulse width Tw before the transition period is fixed will be described. Before the switching transition period, the pulse width Tw does not change due to the input power or the like, but changes into the switching transition period depending on the magnitude of the input power and the power supply voltage Vs. As shown in FIG. 3, the pulse width Tw is a straight line A when the input power is small, a straight line B when the input power is a reference value, and a straight line C when the input power is large. As described above, in the power converter according to the present embodiment, the gradient for changing the pulse width Tw during the switching transition period is changed in accordance with the magnitude of the input power, that is, the magnitude of the load, thereby suppressing the rapid fluctuation of the DC voltage Vd at the time of switching. In addition, the peak of the input current Is is reduced.
[0032]
When the power supply voltage Vs fluctuates, the DC voltage Vd also fluctuates, so that the required minimum value of the voltage boosted before switching the rectifier circuit 4 also fluctuates. In the power supply device of the present embodiment, if the delay time Td of the short-circuit pulse signal 96 and the pulse width Tw are the same, the value of the power supply voltage Vs is equal to the DC voltage Vd obtained during the full-wave rectification circuit or the voltage doubler rectification circuit. The change in the value is substantially proportional to the change in the power supply voltage Vs. Therefore, the DC voltage Vd is input to the control circuit 7 to determine the fluctuation of the power supply voltage Vs.
[0033]
A method of determining the boost pulse width Twb when the power supply voltage Vs fluctuates will be described with reference to FIG. The horizontal axis of FIG. 4 indicates the power supply voltage Vs, and the vertical axis indicates the boost pulse width Twb. FIG. 4 shows a method of determining the boost pulse width Twb when the power supply voltage Vs fluctuates by ± 20%. From the boost pulse width Twb (100%) corresponding to the reference power supply voltage Vs (100%), the boost pulse width Twb is increased or decreased according to the fluctuation of the power supply voltage Vs, and the voltage value to be boosted before switching is changed. For example, when the power supply voltage Vs is 120% of the reference value, the boost pulse width Twb is set to 97% of the reference value. The reason for this is that the DC voltage Vd during voltage doubler rectification also increases because the power supply voltage Vs increases, but the charging current flowing when switching to the voltage doubler rectifier circuit also increases, and the boost due to the charging current also increases. Therefore, when the power supply voltage Vs becomes higher, the boost pulse width Twb is made narrower than the reference value. When the power supply voltage Vs is 80% of the reference value, the boosting width becomes smaller because the charging current decreases, so the boosting pulse width Twb is set to 103% of the reference value.
[0034]
As shown in FIG. 4, as the power supply voltage Vs increases, the boost pulse width Twb monotonically decreases, and the slope of the monotonically decreasing function depends on the circuit constant of the power supply converter and the magnitude of the power supply voltage Vs. When the relationship between the power supply voltage Vs and the boost pulse width Twb in FIG. 4 is applied to FIG. 3, it becomes as shown by a dashed line in FIG. 3, and when the power supply voltage Vs is large, the pulse width Tw is set to a small value. In the power converter of the present embodiment, the slope of the solid line shown in FIG. 3 is changed according to the change in the load, and the pulse width Tw is adjusted as shown by the solid line and the dashed line in FIG. 3 according to the change in the power supply voltage Vs. Therefore, it is possible to cope with both the fluctuation of the input power and the fluctuation of the power supply voltage Vs.
[0035]
Next, the timing of switching the rectifier circuit 4 from the full-wave rectifier circuit to the voltage doubler rectifier circuit and the timing of the short-circuit operation will be described. When the rectifier circuit 4 is switched, a charging current flows to the smoothing capacitor 6 over at least a half cycle of the AC power supply 1. If the short-circuiting means 3 performs a short-circuit operation while the charging current is flowing, the DC voltage Vd greatly increases, and an overshoot occurs when the rectifier circuit 4 is switched. That is, the short-circuit operation is stopped during at least a half cycle or more of the power supply voltage Vs after the rectifier circuit switching unit 5 switches to the voltage doubler rectifier circuit. When the rectifier circuit 4 is switched near the zero cross of the power supply voltage Vs, the input current Is to the power converter 100 is small and the influence of the rectifier circuit switching means 5 is small. Switching from Low to High at the same timing as the rise or fall.
[0036]
However, actually, the operation of the rectifier circuit switching means 5 is not instantaneous but delayed. For example, in a mechanical switch circuit such as a power relay, the delay is several milliseconds or more. When the short circuit operation is stopped at the same time as the rectifier circuit switching signal 97 when there is a delay before the rectifier circuit 4 switches, the DC voltage Vd boosted immediately before the switch is reduced. When the boosted DC voltage Vd decreases, the peak value of the input current Is immediately after the switching of the rectifier circuit 4 increases. Therefore, when there is a switching delay, the power converter according to the present embodiment performs one short-circuit operation after the rectification circuit switching signal 97 switches from Low to High until the rectification circuit switching unit 5 operates. One or more times to prevent a drop in boosted voltage.
[0037]
(Example 2)
This embodiment will be described with reference to FIG. FIG. 5 shows a waveform of the input current starting to flow from t = T3 when the short-circuit means 3 does not perform a short-circuit operation, a case where a short-circuit operation by chopping a plurality of pulses is started before t = T3 (broken line), and after t = T3. 5 shows the input current Is and the DC voltage Vd when a short-circuit operation by chopping is started with a plurality of pulses (solid line). As shown by the solid line in FIG. 5, when the short-circuit operation due to chopping is started from the phase after t = T3, the current flowing through the reactor 2 becomes continuous, the voltage can be efficiently boosted, and the peak value of the input current Is can be reduced. On the other hand, when chopping is performed at a phase earlier than t = T3, the DC voltage Vd cannot be increased as indicated by the dotted line.
[0038]
The chopping frequency is preferably about 10 to 100 times the frequency of the AC power supply 1. For the sake of explanation, the duty ratio of the pulse in FIG. 5 is shown as 50%, but the duty ratio may be other than 50% as long as the current flowing through the reactor 2 is continuous.
[0039]
In the present embodiment, the DC voltage Vd can be controlled by the number of short-circuit operations performed in a half cycle of the power supply voltage Vs and the duty ratio of the short-circuit pulse signal 96. Further, by gradually increasing the number of short-circuit operations during the switching transition period, the DC voltage Vd can also be gradually increased, and the stress applied to the elements constituting the power conversion device 100 and the smoothing capacitor 6 can be reduced.
[0040]
In the present embodiment, similarly to the first embodiment, when there is a change between the load of the power conversion device 100 and the power supply voltage Vs, the minimum necessary value for boosting the DC voltage Vd is changed before switching. In this embodiment, the same effects as in the first embodiment can be obtained by replacing the pulse width on the vertical axis in FIGS. 3 and 4 of the first embodiment with the number of short-circuit operations or the duty of the short-circuit pulse signal 96.
[0041]
FIG. 2 also shows the waveform of the present embodiment. In the short-circuit pulse signal 96 in FIG. 2, the waveform painted out in black is a signal that is chopped at a high frequency as shown in the enlarged view. In the present embodiment, since the control is performed by the chopping signal having the high frequency, the control response is high, and the peak value of the input current Is before and after the end of the switching transition period is small. This embodiment is particularly effective for a power converter in which the rectifier circuit 4 and the short-circuit means 3 include a high-speed diode (fast recovery diode).
[0042]
(Example 3)
This embodiment will be described with reference to FIG. In the present embodiment, the short-circuit operation is performed a plurality of times per half cycle of the power supply voltage Vs during the switching transition period, but after the short-circuit current flowing through the reactor 2 once becomes zero or close to zero, the short-circuit operation shown in FIG. As indicated by the pulse signal 96, the second and subsequent short-circuit operations are performed. In other words, after the recovery current flowing through the diode becomes 0 and the diode is once turned off, the second and subsequent short-circuit operations are performed. As a result, the peak value of the input current Is is reduced, and a sudden change in the DC voltage Vd is also suppressed. This embodiment is suitable for a power supply device using a low-speed diode.
[0043]
【The invention's effect】
As described above, according to the power conversion device of the present invention, the short-circuit pulse width and the number of pulses are controlled to suppress the fluctuation of the DC voltage when switching from the full-wave rectifier circuit to the voltage doubler rectifier circuit, and to input. The peak value of the alternating current can be reduced.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram illustrating a configuration of a power conversion device according to a first embodiment.
FIG. 2 is an explanatory diagram of waveforms of respective units of the power conversion devices according to the first and second embodiments.
FIG. 3 is an explanatory diagram of a pulse width change when a rectifier circuit is switched in the power converter according to the first embodiment.
FIG. 4 is an explanatory diagram of a method of determining a short-circuit pulse width when a power supply voltage fluctuates in the first embodiment.
FIG. 5 is an explanatory diagram of a short-circuit operation start timing when a short-circuit operation is performed a plurality of times in the second embodiment.
FIG. 6 is an explanatory diagram of waveforms of each unit of the power conversion device according to the third embodiment.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... AC power supply, 2 ... Reactor, 3 ... Short circuit means, 4 ... Rectifier circuit, 5 ... Rectifier circuit switching means, 6 ... Smoothing capacitor, 7 ... Control circuit, 8 ... Zero cross detection circuit, 10 ... Inverter circuit, 20 ... Compression , 30 ... Input current detection circuit, 92 ... Zero cross signal, 96 ... Short circuit pulse signal, 97 ... Rectifier circuit switching signal, 100 ... Power converter, Tw ... Pulse width, Td ... Delay time, Vd ... DC voltage, Is ... Input current.
