JP4513456B2 - DC-DC converter transformer magnetism detector - Google Patents

DC-DC converter transformer magnetism detector Download PDF

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JP4513456B2
JP4513456B2 JP2004229056A JP2004229056A JP4513456B2 JP 4513456 B2 JP4513456 B2 JP 4513456B2 JP 2004229056 A JP2004229056 A JP 2004229056A JP 2004229056 A JP2004229056 A JP 2004229056A JP 4513456 B2 JP4513456 B2 JP 4513456B2
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diodes
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隆二 山田
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Fuji Electric Co Ltd
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Description

本発明は、絶縁形直流−直流変換装置における変圧器の磁気飽和に対する保護に関し、特に高価な電流検出器や直流分除去用のコンデンサなどを用いることなく、変圧器の偏磁を検出する装置に関する。   The present invention relates to protection against magnetic saturation of a transformer in an insulation type DC-DC converter, and more particularly, to an apparatus for detecting a magnetic bias of a transformer without using an expensive current detector or a capacitor for removing a DC component. .

図４に、従来方式の回路例を示す。図４において、1は直流電源、２〜５は半導体スイッチ素子、６は変圧器、７〜１０はダイオード、１１はリアクトル、１２は負荷である。
半導体スイッチ素子２と５をオンすると変圧器６の一次巻線に正の電圧が、半導体スイッチ素子３と４をオンすると負の電圧が印加される。正負の電圧を交互に印加することで高周波の交流が変圧器６の一次巻線に入力される。変圧器６によってこれを変圧、絶縁した後ダイオード７〜１０からなるダイオード整流器により整流し、リアクトル１１により平滑することで負荷１２に直流電圧を印加する。負荷１２に印加する電圧はパルス幅制御回路１５により半導体スイッチ素子２〜５がオン・オフする時比率を変えることで制御可能である。
ここで、半導体スイッチ素子２〜５の特性の違い、オン・オフ信号の伝達時間のバラツキ等により、変圧器６には意図しない直流電圧成分が印加されることがある。直流電圧成分が印加されると変圧器６は偏磁を起こし、はなはだしい場合には磁気飽和に至る。磁気飽和が発生すると負荷に正常に電力を伝達できないばかりか、変圧器６がほぼ短絡に等しい状態となるので過電流が発生し、半導体スイッチ素子２〜５を損傷する原因となる。 FIG. 4 shows an example of a conventional circuit. In FIG. 4, 1 is a DC power source, 2 to 5 are semiconductor switch elements, 6 is a transformer, 7 to 10 are diodes, 11 is a reactor, and 12 is a load.
When semiconductor switch elements 2 and 5 are turned on, a positive voltage is applied to the primary winding of transformer 6, and when semiconductor switch elements 3 and 4 are turned on, a negative voltage is applied. By applying positive and negative voltages alternately, high-frequency alternating current is input to the primary winding of the transformer 6. This is transformed and insulated by the transformer 6, then rectified by a diode rectifier composed of diodes 7 to 10, and smoothed by the reactor 11 to apply a DC voltage to the load 12. The voltage applied to the load 12 can be controlled by changing the time ratio at which the semiconductor switch elements 2 to 5 are turned on / off by the pulse width control circuit 15.
Here, an unintended DC voltage component may be applied to the transformer 6 due to a difference in characteristics of the semiconductor switch elements 2 to 5 and a variation in transmission time of the on / off signal. When a DC voltage component is applied, the transformer 6 is demagnetized, and in extreme cases, magnetic saturation is reached. When magnetic saturation occurs, not only can the power not be normally transmitted to the load, but also the transformer 6 is almost equal to a short circuit, so that an overcurrent is generated, which causes damage to the semiconductor switch elements 2-5.

これを防止する手段として、電流検出器１３によって変圧器６の一次巻線電流を検出しその直流成分をローパスフィルタ等からなる直流分検出器１４により抽出し、これをパルス幅制御器１５に入力して直流成分が減少するよう制御することで偏磁を抑制する。以上の方式はたとえば特許文献１に一例が示されている。
特開平9-168278（４頁、図1、図2） 特開平11-98835（６頁、図1〜図３他） As means for preventing this, the primary winding current of the transformer 6 is detected by the current detector 13, and the DC component is extracted by the DC component detector 14 composed of a low-pass filter or the like, and this is input to the pulse width controller 15. By controlling so that the direct current component is reduced, the demagnetization is suppressed. An example of the above method is shown in Patent Document 1, for example.
JP 9-168278 (4 pages, Fig. 1 and Fig. 2) Japanese Patent Laid-Open No. 11-98835 (6 pages, FIGS. 1 to 3 and others)

この従来例において、電流検出器１３は、高周波交流から直流までの広い帯域を持つ必要があり、さらに交流に含まれるわずかな直流成分を捉えるためには高精度であることが要求されるが、一般にそのような検出器は高価である。他の偏磁防止方法としては、たとえば特許文献２にあるように変圧器に直列にコンデンサを挿入し、直流成分を除去する方法があるが、コンデンサに大きな電流が流れるため大型のコンデンサが必要となり、特に大容量器においては価格、大きさの点で不利になる。   In this conventional example, the current detector 13 needs to have a wide band from high-frequency alternating current to direct current, and is required to be highly accurate in order to capture a slight direct current component contained in the alternating current. In general, such detectors are expensive. As another method for preventing demagnetization, there is a method of removing a direct current component by inserting a capacitor in series with a transformer as disclosed in Patent Document 2, for example. However, a large current flows through the capacitor, so a large capacitor is required. In particular, a large capacity device is disadvantageous in terms of price and size.

直流を交流に変換する、いわゆるインバータの出力に変圧器の入力を、前記変圧器の出力に複数のダイオードからなる整流回路の入力を、前記整流回路の出力にリアクトルと負荷との直列回路を接続してなる直流−直流変換装置において、前記整流回路の出力に並列接続した環流ダイオードと、上記整流回路内のダイオードの少なくとも2個についてその導通を検出する導通検出手段と、前記ダイオードの導通時間を比較する時間比較手段とを備え、環流期間中には整流回路のダイオードには励磁電流のみ流れるようにした上で、各々のダイオードのオン時間のアンバランスにより偏磁を検出する。   Converting direct current to alternating current, connecting the transformer input to the output of the so-called inverter, connecting the input of the rectifier circuit consisting of a plurality of diodes to the output of the transformer, and connecting the series circuit of the reactor and load to the output of the rectifier circuit In the DC-DC converter, the circulating diode connected in parallel to the output of the rectifier circuit, the continuity detecting means for detecting the continuity of at least two of the diodes in the rectifier circuit, and the conduction time of the diode Time comparison means for comparison, and during the circulation period, only the excitation current flows through the diodes of the rectifier circuit, and the bias is detected by imbalance of the on-time of each diode.

少なくとも２個の整流ダイオードの導通時間差を検出するだけで、従来のように高価な電流検出器や直流分除去用のコンデンサを用いることなく偏磁検出を可能とし、それによる偏磁抑制が安価に実現できる。   By detecting the difference in conduction time between at least two rectifier diodes, it is possible to detect demagnetization without using an expensive current detector or capacitor for removing a DC component as in the past, thereby reducing demagnetization. realizable.

図１に本発明の第1の実施例を、図２にその動作を示す。図４と同一の部品については同一符号を付してその説明は省略する。図１において、１０１は環流ダイオード、１０２、１０３は電圧検出器、１０４は時間差測定器である。
半導体スイッチ素子２〜５は図４の動作と同様に、半導体スイッチ素子２、５がオン、半導体スイッチ素子３、４がオンを交互に繰り返す。半導体スイッチ素子２、５がオンすると、変圧器６に電圧が印加され、変圧器６に励磁電流が流れ、さらに二次側巻線にはダイオード７、１０が導通してリアクトル１１と負荷１２を通る経路で電流が流れる。次に、半導体スイッチ素子２，５をオフするとリアクトル１１の平滑作用によりリアクトル１１の電流が保持され、この電流は環流ダイオード１０１を流れる。
ここで電流経路としては整流ダイオード７〜１０を通る経路も存在し得るが、こちらの経路ではダイオードが２直列になり、順電圧が２倍発生することになるため、電流は環流ダイオード１０１に流れる。この期間を環流期間と称する。次に、半導体スイッチ素子３、４がオンすると、変圧器６に電圧が印加され、変圧器６に励磁電流が流れ、さらに二次側巻線にはダイオード８、９が導通してリアクトル１１と負荷１２を通る経路で電流が流れる。次に、半導体スイッチ素子３，４をオフするとリアクトル１１の平滑作用によりリアクトル１１の電流が保持され、この電流は環流ダイオード１０１を流れる。ここで電流経路としては整流ダイオード７〜１０を通る経路も存在し得るが、こちらの経路ではダイオードが２直列になり、順電圧が２倍発生することになるため、電流は環流ダイオード１０１に流れる。
なお、環流ダイオード１０１を設ける方法は環流期間中の損失を低減するために一般的に用いられる方法である。このとき変圧器６の励磁電流は一次側ないし二次側で流れつづけようとするが、一次側を流れると直流電源１の電圧が電流を減少させる方向にかかるのに対し、二次側を流れるとそれよりはるかに小さい７〜１０の順電圧が２個分かかるだけなので、励磁電流は二次側を流れる。例えば環流期間に入るときに一次側で励磁電流が正極性であったとすると、二次側では励磁電流は負極性になるので変圧器６→ダイオード９→リアクトル１１→負荷１２→ダイオード８→変圧器６の経路で流れ、ダイオード８と９が導通する。同様に、環流期間に入るときに励磁電流が負極性であったとすると、二次側では励磁電流は正極性になるのでダイオード７と１０が導通する。 FIG. 1 shows a first embodiment of the present invention, and FIG. 2 shows its operation. The same parts as those in FIG. 4 are denoted by the same reference numerals, and the description thereof is omitted. In FIG. 1, 101 is a free-wheeling diode, 102 and 103 are voltage detectors, and 104 is a time difference measuring device.
In the semiconductor switch elements 2 to 5, the semiconductor switch elements 2 and 5 are alternately turned on and the semiconductor switch elements 3 and 4 are alternately turned on similarly to the operation of FIG. When the semiconductor switch elements 2 and 5 are turned on, a voltage is applied to the transformer 6, an exciting current flows through the transformer 6, and the diodes 7 and 10 are conducted to the secondary winding to connect the reactor 11 and the load 12. Current flows through the path. Next, when the semiconductor switch elements 2 and 5 are turned off, the current of the reactor 11 is held by the smooth action of the reactor 11, and this current flows through the freewheeling diode 101.
Here, there may be a path through the rectifier diodes 7 to 10 as the current path. However, in this path, two diodes are connected in series, and a forward voltage is generated twice. . This period is called a reflux period. Next, when the semiconductor switch elements 3 and 4 are turned on, a voltage is applied to the transformer 6, an exciting current flows through the transformer 6, and the diodes 8 and 9 are conducted to the secondary winding to connect the reactor 11. Current flows in a path through the load 12. Next, when the semiconductor switch elements 3 and 4 are turned off, the current of the reactor 11 is held by the smoothing action of the reactor 11, and this current flows through the freewheeling diode 101. Here, there may be a path through the rectifier diodes 7 to 10 as the current path. However, in this path, two diodes are connected in series, and a forward voltage is generated twice. .
The method of providing the freewheeling diode 101 is a method that is generally used to reduce the loss during the freewheeling period. At this time, the exciting current of the transformer 6 tries to continue to flow from the primary side to the secondary side, but when flowing through the primary side, the voltage of the DC power source 1 is applied in the direction of decreasing the current, whereas it flows through the secondary side. Since only two forward voltages of 7 to 10 much smaller than that are required, the exciting current flows on the secondary side. For example, if the excitation current is positive on the primary side when entering the recirculation period, the excitation current becomes negative on the secondary side, so that the transformer 6 → the diode 9 → the reactor 11 → the load 12 → the diode 8 → the transformer 6 flows and diodes 8 and 9 become conductive. Similarly, assuming that the excitation current has a negative polarity when entering the reflux period, the diodes 7 and 10 are conductive because the excitation current has a positive polarity on the secondary side.

偏磁が発生していないときには励磁電流は正負均等の波形であるので、ダイオード７と１０、ダイオード８と９における導通時間は均等である。一方、偏磁が発生すると導通時間が不均等となる。図２に示すように励磁電流が正に偏ると、環流期間中には常にダイオード８と９が導通することになり、ダイオード７と１０、ダイオード８と９の導通時間が不均等となる。これを検出することで偏磁の発生が検出可能となる。
ダイオードの導通は各々の電流を検出することでも可能であるが、より安価に行うため、図１においてはアノード・カソード間の電圧を検出する電圧検出器１０２、１０３を設けている。これらはダイオード８および１０に順電圧が発生したことを検出するもので、逆電圧の検出機能は不要である。また、順電圧の値そのものは問題にしないので、精度も必要ない。同様の理由により個々のダイオードの順電圧のばらつきも問題にならない。電圧検出器としては、抵抗の直列回路などを用いる方法、抵抗の直列回路と増幅器を用いる方法などがある。 When no magnetism has occurred, the excitation current has a positive and negative equal waveform, so that the conduction times of the diodes 7 and 10 and the diodes 8 and 9 are equal. On the other hand, when the demagnetization occurs, the conduction time becomes uneven. As shown in FIG. 2, when the exciting current is positively biased, the diodes 8 and 9 are always conducted during the circulation period, and the conduction times of the diodes 7 and 10 and the diodes 8 and 9 are uneven. By detecting this, the occurrence of bias can be detected.
Although it is possible to conduct the diode by detecting each current, voltage detectors 102 and 103 for detecting the voltage between the anode and the cathode are provided in FIG. These detect the occurrence of forward voltage in the diodes 8 and 10, and do not require a reverse voltage detection function. Further, since the forward voltage value itself does not matter, accuracy is not necessary. For the same reason, variations in forward voltage of individual diodes do not become a problem. As the voltage detector, there are a method using a series circuit of resistors and a method using a series circuit of resistors and an amplifier.

ダイオード８および１０の導通時間の差を、時間差測定器１０４で測定する。時間差測定器１０４はカウンタまたは積分器等からなる。ここで必要な値は環流期間の導通時間差であるが、定常状態において変圧器6に正の電圧を印加する期間、負の電圧を印加する期間の時間差は十分小さいので、全ての期間の導通時間差を測定しても問題ない。
時間差測定器１０４の測定結果に基づき、導通時間差が小さくなるようパルス幅制御器１５によって半導体スイッチ素子２，５のオン時間と、半導体スイッチ素子３，４のオン時間を調整することにより偏磁が抑制される。 The difference in conduction time between the diodes 8 and 10 is measured by the time difference measuring device 104. The time difference measuring device 104 includes a counter or an integrator. The required value here is the conduction time difference in the reflux period, but the time difference between the period in which the positive voltage is applied to the transformer 6 and the period in which the negative voltage is applied in the steady state is sufficiently small. There is no problem to measure.
Based on the measurement results of the time difference measuring device 104, the pulse width controller 15 adjusts the on-time of the semiconductor switch elements 2 and 5 and the on-time of the semiconductor switch elements 3 and 4 so as to reduce the conduction time difference. It is suppressed.

図３に本発明の第２の実施例を示す。図1との違いは、変圧器の２次側巻線がセンタータップとなっており、さらに整流ダイオードとしてダイオード７と９の２個を使用したセンタータップ整流回路としてあり、ダイオード７に電圧検出器１０３が、ダイオード９に電圧検出器１０２が取り付けてある点である。この構成では、環流期間は環流ダイオード１０１と、整流ダイオード７または９と変圧器２次巻線との直列回路が並列接続されるため、環流電流を環流ダイオードに流すために環流ダイオード１０１の順方向電圧は整流ダイオード７、９に比べて小さいものを選択してある。
その他の動作については図１と同様である。即ち、半導体スイッチ素子２、５がオンすると、変圧器６に電圧が印加され、変圧器６に励磁電流が流れ、さらに二次側巻線にはダイオード７が導通してリアクトル１１と負荷１２を通る経路で電流が流れる。次に、半導体スイッチ素子２，５をオフするとリアクトル１１の平滑作用によりリアクトル１１の電流が保持され、この電流は環流ダイオード１０１を流れる。ここで電流経路としては整流ダイオード７、９を通る経路も存在し得るが、環流ダイオード１０１の順電圧は、ダイオード７、９の順電圧に比べて小さく選んであるため、電流は環流ダイオード１０１に流れる。 FIG. 3 shows a second embodiment of the present invention. The difference from Fig. 1 is that the transformer secondary winding is a center tap, and further a center tap rectifier circuit using two diodes 7 and 9 as rectifier diodes. Reference numeral 103 denotes a point where the voltage detector 102 is attached to the diode 9. In this configuration, the freewheeling diode 101 and the series circuit of the rectifier diode 7 or 9 and the transformer secondary winding are connected in parallel during the freewheeling period. Therefore, the forward direction of the freewheeling diode 101 is used to flow the freewheeling current to the freewheeling diode. A voltage smaller than that of the rectifier diodes 7 and 9 is selected.
Other operations are the same as those in FIG. That is, when the semiconductor switch elements 2 and 5 are turned on, a voltage is applied to the transformer 6, an exciting current flows through the transformer 6, and a diode 7 is conducted to the secondary winding to connect the reactor 11 and the load 12. Current flows through the path. Next, when the semiconductor switch elements 2 and 5 are turned off, the current of the reactor 11 is held by the smooth action of the reactor 11, and this current flows through the freewheeling diode 101. Here, there may be paths through the rectifier diodes 7 and 9 as current paths. However, since the forward voltage of the freewheeling diode 101 is selected to be smaller than the forward voltage of the diodes 7 and 9, the current flows to the freewheeling diode 101. Flowing.

次に、半導体スイッチ素子３、４がオンすると、変圧器６に電圧が印加され、変圧器６に励磁電流が流れ、さらに二次側巻線にはダイオード９が導通してリアクトル１１と負荷１２を通る経路で電流が流れる。次に、半導体スイッチ素子３，４をオフするとリアクトル１１の平滑作用によりリアクトル１１の電流が保持され、この電流は環流ダイオード１０１を流れる。ここで電流経路としては整流ダイオード７、９を通る経路も存在し得るが、環流ダイオード１０１の順電圧は、ダイオード７、９の順電圧に比べて小さく選んであるため、電流は環流ダイオード１０１に流れる。偏磁が発生していないときには励磁電流は正負均等の波形であるので、ダイオード７の導通期間とダイオード９における導通時間は均等である。
一方、偏磁が発生すると導通時間が不均等となる。図２と同じように励磁電流が正に偏ると、環流期間中には常にダイオード９が導通することになり、ダイオード７とダイオード９の導通時間が不均等となる。これを検出することで偏磁の発生が検出可能となる。ダイオード７および９の導通時間の差を、時間差測定器１０４で測定する。時間差測定器１０４はカウンタまたは積分器等からなる。ここで必要な値は環流期間の導通時間差であるが、定常状態において変圧器6に正の電圧を印加する期間、負の電圧を印加する期間の時間差は十分小さいので、全ての期間の導通時間差を測定しても問題ない。 Next, when the semiconductor switch elements 3 and 4 are turned on, a voltage is applied to the transformer 6, an exciting current flows through the transformer 6, and a diode 9 is conducted to the secondary winding to cause the reactor 11 and the load 12. Current flows through the path. Next, when the semiconductor switch elements 3 and 4 are turned off, the current of the reactor 11 is held by the smoothing action of the reactor 11, and this current flows through the freewheeling diode 101. Here, there may be paths through the rectifier diodes 7 and 9 as current paths. However, since the forward voltage of the freewheeling diode 101 is selected to be smaller than the forward voltage of the diodes 7 and 9, the current flows to the freewheeling diode 101. Flowing. When no magnetization is generated, the excitation current has a positive and negative equal waveform, so that the conduction period of the diode 7 and the conduction time of the diode 9 are equal.
On the other hand, when the demagnetization occurs, the conduction time becomes uneven. As in FIG. 2, when the exciting current is positively biased, the diode 9 always conducts during the circulation period, and the conduction time between the diode 7 and the diode 9 becomes uneven. By detecting this, the occurrence of bias can be detected. The difference in conduction time between the diodes 7 and 9 is measured by the time difference measuring device 104. The time difference measuring device 104 includes a counter or an integrator. The required value here is the conduction time difference in the reflux period, but the time difference between the period in which the positive voltage is applied to the transformer 6 and the period in which the negative voltage is applied in the steady state is sufficiently small. There is no problem to measure.

時間差測定器１０４の測定結果に基づき、導通時間差が小さくなるようパルス幅制御器１５によって半導体スイッチ素子２，５のオン時間と、半導体スイッチ素子３，４のオン時間を調整することにより偏磁が抑制される。  Based on the measurement results of the time difference measuring device 104, the pulse width controller 15 adjusts the on-time of the semiconductor switch elements 2 and 5 and the on-time of the semiconductor switch elements 3 and 4 so as to reduce the conduction time difference. It is suppressed.

本発明は、フルブリッジ形スイッチングレギュレータの偏磁防止回路に関するもので、高価な電流検出器やコンデンサ等を使用せずに変圧器の偏磁を検出できるので、フルブリッジ形インバータ回路を用い、出力に変圧器を使用するスイッチングレギュレータ、ＤＣ−ＤＣコンバータ、高圧電源などに適用できる。   The present invention relates to a demagnetization prevention circuit of a full-bridge type switching regulator, and can detect the demagnetization of a transformer without using an expensive current detector or capacitor. It can be applied to switching regulators using DC transformers, DC-DC converters, high-voltage power supplies, and the like.

本発明の第1の実施例を示す。1 shows a first embodiment of the present invention. 図1の動作波形を示す。The operation waveform of FIG. 1 is shown. 本発明の第２の実施例を示す。2 shows a second embodiment of the present invention. 従来の実施例を示す。A conventional example is shown.

符号の説明Explanation of symbols

１・・・直流電源 ２〜５半導体スイッチ素子 ６・・・変圧器
７〜１０・・・ダイオード １１・・・リアクトル １２・・・負荷
１３・・・電流検出器 １４・・・直流分検出器
１５・・・パルス幅増幅器 １０１・・・環流ダイオード
１０２、１０３・・・電圧検出器 １０４・・・時間差測定器 DESCRIPTION OF SYMBOLS 1 ... DC power supply 2-5 Semiconductor switch element 6 ... Transformer 7-10 ... Diode 11 ... Reactor 12 ... Load 13 ... Current detector 14 ... DC component detector
DESCRIPTION OF SYMBOLS 15 ... Pulse width amplifier 101 ... Freewheeling diode 102, 103 ... Voltage detector 104 ... Time difference measuring device

Claims (1)

直流を交流に変換する、いわゆるインバータの出力に変圧器の入力を、前記変圧器の出力に複数のダイオードからなる整流回路の入力を、前記整流回路の出力にリアクトルと負荷との直列回路を接続してなる直流−直流変換装置において、
還流期間中に前記整流回路のダイオードに励磁電流のみを流すために前記整流回路の出力に並列接続した環流ダイオードと、前記整流回路内のダイオードの少なくとも２個についてその導通を検出する導通検出手段と、前記２個のダイオードの導通時間を比較する時間比較手段とを備えたことを特徴とする直流−直流変換装置の変圧器偏磁検出装置。 Converting direct current to alternating current, connecting the input of a transformer to the output of a so-called inverter, connecting the input of a rectifier circuit consisting of a plurality of diodes to the output of the transformer, and connecting a series circuit of a reactor and a load to the output of the rectifier circuit In the DC-DC converter formed by
Wherein the wheeling diode connected in parallel to the output of the rectifier circuit, conduction detecting means for detecting the conduction for at least two diodes of the previous SL in the rectifier circuit to flow only exciting current to the diode of the rectifier circuit in refluxing period And a time comparison means for comparing the conduction times of the two diodes. A transformer demagnetization detecting device for a DC-DC converter.
JP2004229056A 2004-08-05 2004-08-05 DC-DC converter transformer magnetism detector Expired - Fee Related JP4513456B2 (en)

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US8348551B2 (en) * 2009-07-29 2013-01-08 Terratherm, Inc. Method and system for treating contaminated materials
JP5434527B2 (en) * 2009-11-27 2014-03-05 富士電機株式会社 DC-DC converter circuit
JP5564400B2 (en) * 2010-03-11 2014-07-30 株式会社日立製作所 DC power supply, power converter
WO2013049224A2 (en) * 2011-09-26 2013-04-04 Murata Power Solutions Power transformer active flux balance circuit with driver dead time control
JP2015159711A (en) 2014-01-23 2015-09-03 パナソニックＩｐマネジメント株式会社 Switching power supply and power converter
CN111162680B (en) * 2018-11-08 2021-07-30 中车永济电机有限公司 Current bias adjusting method and device for direct-drive permanent magnet electric locomotive converter
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JPH09163736A (en) * 1995-12-11 1997-06-20 Sanken Electric Co Ltd Dc-dc converter
JPH10337021A (en) * 1997-05-19 1998-12-18 Trw Inc Phase crossing full bridge converter accompanied with soft pwm switching
JP2004015900A (en) * 2002-06-05 2004-01-15 Omron Corp Electric power conversion system of push-pull circuit

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH09163736A (en) * 1995-12-11 1997-06-20 Sanken Electric Co Ltd Dc-dc converter
JPH10337021A (en) * 1997-05-19 1998-12-18 Trw Inc Phase crossing full bridge converter accompanied with soft pwm switching
JP2004015900A (en) * 2002-06-05 2004-01-15 Omron Corp Electric power conversion system of push-pull circuit

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