JP3533725B2 - Voltage transformation circuit - Google Patents
Voltage transformation circuitInfo
- Publication number
- JP3533725B2 JP3533725B2 JP27094094A JP27094094A JP3533725B2 JP 3533725 B2 JP3533725 B2 JP 3533725B2 JP 27094094 A JP27094094 A JP 27094094A JP 27094094 A JP27094094 A JP 27094094A JP 3533725 B2 JP3533725 B2 JP 3533725B2
- Authority
- JP
- Japan
- Prior art keywords
- resistance
- winding
- voltage
- temperature coefficient
- equation
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Fee Related
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- Transformers For Measuring Instruments (AREA)
Description
【発明の詳細な説明】
【０００１】
【産業上の利用分野】この発明は、計器用変圧器を用い
た電圧変成回路に関する。
【０００２】
【従来の技術】従来より電力制御システムや電動力制御
システムを監視制御する制御盤等においては、監視対象
である電圧信号を入力するために、その入力部に電圧変
成回路を用いている。特にマイクロプロセッサ等のディ
ジタル演算処理回路に対する電圧データを入力するため
に、Ａ／Ｄコンバータにアナログ電圧信号を入力する場
合等、最終的に必要とする電圧レベルが微弱である場合
には、超小型の計器用変圧器が用いられる。
【０００３】このような超小型の計器用変圧器において
は、その小型化による１次巻線の自己インダクタンスの
減少に起因する励磁電流の増大を抑えるために、全体の
外形寸法を大型化することなく、径の細い巻線を数多く
巻回している。そのため、通常の計器用変圧器に比較し
て巻線抵抗が大きく、巻線の許容電流値も低い。そこ
で、このような超小型の計器用変圧器を用いた従来の電
圧変成回路は、図３に示すように、１次側に電流制限抵
抗を挿入し、２次側には、電流電圧変換回路を接続し
て、１次側入力電圧に比例した一定比率の電圧信号を２
次側に得るようにしている。
【０００４】
【発明が解決しようとする課題】ところが、このように
計器用変圧器の１次側に電流制限抵抗を挿入し、２次側
に電流電圧変換回路を接続した電圧変成回路において
は、周囲の温度変化があれば、以下に述べるように電流
制限抵抗Ｒ1 と計器用変圧器ＰＴの巻線抵抗の抵抗変化
などに応じて、電圧変成比が変動する。
【０００５】すなわち、ここで入力電圧をＶ1 、１次巻
線の抵抗と２次巻線の１次換算抵抗との合成巻線抵抗を
ｒとすれば、１次電流Ｉ1 は、
Ｉ1 ＝Ｖ1 ／（Ｒ1 ＋ｒ） （式１）
で定まり、また、電流電圧変換回路の変換係数をｋと
し、出力電圧をＶ2 とすれば、図３に示した２次電流Ｉ
2 は、
Ｉ2 ＝Ｖ2 ／ｋ （式２）
となる。
【０００６】図３に示した計器用変圧器ＰＴは１次側に
電流制限抵抗Ｒ1 が設けられ、２次側に低入力インピー
ダンスの回路が接続されることになるため、変流器のよ
うに作用し、次式が成り立つ。
【０００７】
Ｉ2 ／Ｉ1 ＝Ｎ1 ／Ｎ2 （式３）
ここでＮ1 ，Ｎ2 は計器用変圧器ＰＴの１次巻線，２次
巻線の巻回数である。
【０００８】（式１）〜（式３）から、
Ｎ2 ／Ｎ1 ＝Ｉ1 ／Ｉ2
＝｛Ｖ1 ／（Ｒ1 ＋ｒ）｝／（Ｖ2 ／ｋ）
＝（Ｖ1 ／Ｖ2 ）・｛ｋ／（Ｒ1 ＋ｒ）｝
が成り立ち、図３に示した電圧変成器全体の電圧変成比
（Ｖ2 ／Ｖ1 ）は、
Ｖ2 ／Ｖ1 ＝（Ｎ1 ／Ｎ2 ）｛ｋ／（Ｒ1 ＋ｒ）｝ （式４）
となる。したがって、上記電圧変成比（Ｖ2 ／Ｖ1 ）
は、周囲温度の変化があれば｛ｋ／（Ｒ1 ＋ｒ）｝の変
化に比例して変化する。このうち電流制限抵抗Ｒ1と電
流電圧変換係数ｋの温度変化による変動は充分小さく抑
えられるとしても、計器用変圧器ＰＴの巻線材料は銅線
であり、その抵抗温度係数は比較的大きく、上述したと
おり、巻線抵抗の増大のともない、周囲温度の変化によ
る電圧変成比の変動（誤差）が大きくなる。例えば、上
記｛ｋ／（Ｒ1 ＋ｒ）｝の値が２０°Ｃ±２０°Ｃにお
いて０．２％変動すれば、電圧変成器全体の電圧変成比
も２０°Ｃ±２０°Ｃにおいて０．２％変動し、精密測
定器における電圧変成回路に適さない。
【０００９】この発明の目的は、温度変化による上記計
器用変圧器の巻線抵抗の変化に起因する電圧変成比の変
動を抑えて、温度変化に拘らず一定の測定精度を保つよ
うにした電圧変成回路を提供することにある。
【００１０】
【課題を解決するための手段】この発明の電圧変成回路
は、オペアンプの反転入力端子と出力端子との間に帰還
抵抗を接続し、前記オペアンプの反転入力端子と非反転
入力端子との間に計器用変圧器の２次巻線を接続し、前
記計器用変圧器の１次巻線に電流制限抵抗を接続して電
圧変成回路を構成し、前記帰還抵抗の抵抗温度係数を、
前記計器用変圧器の１次側換算合成巻線抵抗と前記電流
制限抵抗との合成抵抗の抵抗温度係数に略等しくする。
【００１１】
【作用】この発明の電圧変成回路の構成例を図１に示
す。図１においてオペアンプＯＰの反転入力端子と出力
端子との間に帰還抵抗を接続しているため、計器用変圧
器ＰＴの２次巻線からオペアンプＯＰを見た、オペアン
プＯＰの入力インピーダンスは極めて小さく、イマジナ
リショート状態であるから、１次巻線に流れる電流Ｉ1
は帰還抵抗Ｒ2 の値に拘らず次式が成り立つ。
【００１２】
Ｉ1 ＝Ｖ1 ／（Ｒ1 ＋ｒ） （式５）
ここでｒは計器用変圧器ＰＴの１次側換算合成巻線抵抗
であり、計器用変圧器ＰＴの１次巻線抵抗をｒ1 、その
２次巻線抵抗をｒ2 とし、１次巻線と２次巻線の巻回比
（Ｎ1 ／Ｎ2 ）をａとすれば、
ｒ＝ｒ1 ＋ａ2 ｒ2 （式６）
と表せる。
【００１３】また、計器用変圧器ＰＴの２次電流Ｉ2 に
等しい電流がオペアンプＯＰの帰還抵抗Ｒ2 に流れるた
め、
Ｉ2 ＝Ｖ2 ／Ｒ2 （式７）
が成り立つ。図１に示した計器用変圧器ＰＴの２次側は
イマジナリショート状態であるため、ＰＴは変流器のよ
うに作用し、次式が成り立つ。
【００１４】
Ｉ2 ／Ｉ1 ＝Ｎ1 ／Ｎ2 （式８）
（式５），（式７），（式８）から、
Ｎ2 ／Ｎ1 ＝Ｉ1 ／Ｉ2
＝｛Ｖ1 ／（Ｒ1 ＋ｒ）｝／（Ｖ2 ／Ｒ2 ）
＝（Ｖ1 ／Ｖ2 ）・｛Ｒ2 ／（Ｒ1 ＋ｒ）｝
が成り立ち、図１に示した電圧変成器全体の電圧変成比
（Ｖ2 ／Ｖ1 ）は
Ｖ2 ／Ｖ1 ＝（Ｎ1 ／Ｎ2 ）｛Ｒ2 ／（Ｒ1 ＋ｒ）｝ （式９）
となる。
【００１５】（式９）で、抵抗Ｒ2 の抵抗温度係数はこ
の発明では計器用変圧器の１次側換算合成巻線抵抗ｒと
電流制限抵抗Ｒ1 との合成抵抗の抵抗温度係数にほぼ等
しいため、電圧変成比Ｖ2 ／Ｖ1 は温度変化によらず一
定値を保つ。
【００１６】
【実施例】この実施例では、巻線としてφ０．０５の絶
縁被覆銅線を用い、１次巻線の巻回数Ｎ1 を３２００、
２次巻線の巻回数Ｎ2 を２１５０とした計器用変圧器を
用いる。この計器用変圧器の１次巻線抵抗ｒ1 は８００
Ω、２次巻線抵抗ｒ2 は５１０Ωである。したがって１
次側換算合成巻線抵抗ｒは、前記（式６）より、
ｒ＝ｒ1 ＋ａ2 ｒ2
＝８００＋（３２００／２１５０）2 ×５１０
＝１１３０Ω
である。
【００１７】前記（式９）に対して抵抗温度係数を考慮
すると次式が成り立つ。
【００１８】
Ｖ2 ／Ｖ1 ＝（Ｎ1 ／Ｎ2 ）〔Ｒ2 （１＋α2 ｔ）／｛Ｒ1 （１＋α1 ｔ）
＋ｒ（１＋α3 ｔ）｝〕 （式１０）
ここで、α1 は電流制限抵抗Ｒ1 の抵抗温度係数、α2
は帰還抵抗の抵抗温度係数、α3 は巻線抵抗の抵抗温度
係数である。また、ｔは基準温度に対する変化温度であ
る。
【００１９】上記Ｖ2 ／Ｖ1 の値が使用温度範囲で略一
定となるように、電流制限抵抗Ｒ1の抵抗温度係数α1
と巻線抵抗の抵抗温度係数α3 に応じて、帰還抵抗Ｒ2
の抵抗温度係数α2 を求める。
【００２０】そこで、
（Ｎ1 ／Ｎ2 ）〔Ｒ2 （１＋α2 ｔ）／｛Ｒ1 （１＋α
1 ｔ）＋ｒ（１＋α3 ｔ）｝〕＝（Ｎ1 ／Ｎ2 ）｛Ｒ2
／（Ｒ1 ＋ｒ）｝
とおいて、次式を得る。
【００２１】
α2 ＝（α1 Ｒ1 ＋α3 ｒ）／（Ｒ1 ＋ｒ） （式１１）
ここで電流制限抵抗Ｒ1 を２００ｋΩ、その電流制限抵
抗Ｒ1 の抵抗温度係数α1 を０．７５×１０-4、１次側
換算合成巻線抵抗ｒを１１３０Ω、その抵抗温度係数を
０．４２７×１０-2とすれば、これらを（式１１）に代
入して、
α2 ＝０．９８５×１０-4
を求める。したがって帰還抵抗Ｒ2 の抵抗温度係数とし
て０．９８５×１０-4に近似する抵抗器を用いる。
【００２２】上記所定の抵抗温度係数を有する帰還抵抗
を備えた電圧変成回路の例を図２に示す。図２において
（Ａ）は帰還抵抗を抵抗Ｒ21とＲ22の直列回路で構成し
た例、（Ｂ）は帰還抵抗を抵抗Ｒ21とＲ22の並列回路で
構成した例である。このように複数の抵抗器を組み合わ
せる際、Ｒ21，Ｒ22の抵抗値と抵抗温度係数を選択する
ことによって、その合成抵抗値を所望の値（例えば１０
ｋΩ）にするとともに、合成抵抗の抵抗温度係数α2 を
前記の所定値に近似させる。
【００２３】
【発明の効果】この発明によれば、計器用変圧器の巻線
抵抗が比較的大きくて、周囲温度の変化によって、入力
電流値が変化する場合であっても、計器用変圧器の２次
側に設けたオペアンプによる電流電圧変換回路部でその
補正が行われ、全体の電圧変成比が一定に保たれるた
め、周囲の温度変化に拘らず一定の測定精度が保たれ
る。
【００２４】Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a voltage transforming circuit using a transformer for an instrument. 2. Description of the Related Art Conventionally, in a control panel or the like for monitoring and controlling a power control system or an electric power control system, in order to input a voltage signal to be monitored, a voltage transforming circuit is used at an input portion thereof. I have. Particularly, when the voltage level finally required is weak, such as when an analog voltage signal is input to an A / D converter in order to input voltage data to a digital operation processing circuit such as a microprocessor, an ultra-compact Instrument transformer is used. In such an ultra-compact instrument transformer, the overall external dimensions must be increased in order to suppress an increase in the exciting current due to a decrease in the self-inductance of the primary winding due to the miniaturization. Instead, many small diameter windings are wound. For this reason, the winding resistance is large and the allowable current value of the winding is low as compared with a normal instrument transformer. Therefore, a conventional voltage transformer using such a miniature instrument transformer has a current limiting resistor inserted on the primary side and a current-voltage converter circuit on the secondary side as shown in FIG. And a constant-rate voltage signal proportional to the primary-side input voltage.
I try to get to the next side. [0004] However, in a voltage transforming circuit in which a current limiting resistor is inserted on the primary side of the instrument transformer and a current-voltage converting circuit is connected on the secondary side as described above, If there is a change in the ambient temperature, the voltage transformation ratio fluctuates according to the resistance change of the current limiting resistor R1 and the winding resistance of the instrument transformer PT as described below. That is, if the input voltage is V1 and the combined winding resistance of the resistance of the primary winding and the primary conversion resistance of the secondary winding is r, the primary current I1 is I1 = V1 / V (R1 + r) (Equation 1) Further, if the conversion coefficient of the current-voltage conversion circuit is k and the output voltage is V2, the secondary current I shown in FIG.
2 is I2 = V2 / k (Equation 2). The instrument transformer PT shown in FIG. 3 is provided with a current limiting resistor R1 on the primary side and a low input impedance circuit connected on the secondary side. And the following equation holds. I 2 / I 1 = N 1 / N 2 (Equation 3) where N 1 and N 2 are the number of turns of the primary winding and the secondary winding of the instrument transformer PT. From equations (1) to (3), N2 / N1 = I1 / I2 = {V1 / (R1 + r)} / (V2 / k) = (V1 / V2) .multidot.k / (R1 + r) 、 Holds, and the voltage transformation ratio (V2 / V1) of the entire voltage transformer shown in FIG. 3 is as follows: V2 / V1 = (N1 / N2) {k / (R1 + r)} (Equation 4). Therefore, the above-mentioned voltage transformation ratio (V2 / V1)
Changes in proportion to the change of {k / (R1 + r)} if the ambient temperature changes. Among them, even if the fluctuation of the current limiting resistor R1 and the current-voltage conversion coefficient k due to the temperature change can be suppressed sufficiently small, the winding material of the instrument transformer PT is a copper wire, and its resistance temperature coefficient is relatively large. As described above, as the winding resistance increases, the fluctuation (error) in the voltage conversion ratio due to the change in the ambient temperature increases. For example, if the value of {k / (R1 + r)} fluctuates by 0.2% at 20 ° C. ± 20 ° C., the voltage conversion ratio of the entire voltage transformer is also 0.2% at 20 ° C. ± 20 ° C. %, Which is not suitable for voltage transformation circuits in precision measuring instruments. SUMMARY OF THE INVENTION It is an object of the present invention to suppress a change in a voltage transformation ratio caused by a change in winding resistance of the above-mentioned instrument transformer due to a temperature change, and to maintain a constant measurement accuracy regardless of a temperature change. An object of the present invention is to provide a transformation circuit. [0010] The voltage converting circuit according to the present invention has a feedback resistor connected between an inverting input terminal and an output terminal of an operational amplifier, and has an inverting input terminal and a non-inverting input terminal of the operational amplifier. The secondary winding of the instrument transformer is connected between them, a current limiting resistor is connected to the primary winding of the instrument transformer to form a voltage transformer circuit, and the temperature coefficient of resistance of the feedback resistor is
A resistance temperature coefficient of a combined resistance of the primary-side converted combined winding resistance of the instrument transformer and the current limiting resistance is set to be substantially equal. FIG. 1 shows an example of the configuration of a voltage conversion circuit according to the present invention. In FIG. 1, since the feedback resistor is connected between the inverting input terminal and the output terminal of the operational amplifier OP, the input impedance of the operational amplifier OP is extremely small when the operational amplifier OP is viewed from the secondary winding of the instrument transformer PT. Current I1 flowing in the primary winding because of the imaginary short state.
Satisfies the following equation regardless of the value of the feedback resistor R2. I 1 = V 1 / (R 1 + r) (Equation 5) where r is a primary-side converted composite winding resistance of the instrument transformer PT, and the primary winding resistance of the instrument transformer PT is r 1, the secondary winding resistance and r2, if the winding ratio of the primary winding and the secondary winding (N1 / N2) and a, expressed as r = r1 + a 2 r2 (equation 6). Further, since a current equal to the secondary current I2 of the instrument transformer PT flows through the feedback resistor R2 of the operational amplifier OP, I2 = V2 / R2 (Equation 7) holds. Since the secondary side of the instrument transformer PT shown in FIG. 1 is in an imaginary short state, the PT acts like a current transformer, and the following equation holds. I2 / I1 = N1 / N2 (Equation 8) From (Equation 5), (Equation 7) and (Equation 8), N2 / N1 = I1 / I2 = {V1 / (R1 + r)} / (V2 // R2) = (V1 / V2) ｛{R2 / (R1 + r)} holds, and the voltage transformation ratio (V2 / V1) of the entire voltage transformer shown in FIG. 1 is V2 / V1 = (N1 / N2) ｛R2. / (R1 + r)｝ (Equation 9). In equation (9), the resistance temperature coefficient of the resistor R2 is substantially equal to the resistance temperature coefficient of the combined resistance of the primary-side converted combined winding resistance r and the current limiting resistor R1 of the instrument transformer in the present invention. , The voltage conversion ratio V2 / V1 maintains a constant value regardless of the temperature change. In this embodiment, an insulated copper wire having a diameter of 0.05 is used as the winding, and the number of turns N1 of the primary winding is set to 3,200.
An instrument transformer in which the number of turns N2 of the secondary winding is 2150 is used. The primary winding resistance r1 of this instrument transformer is 800
Ω, and the secondary winding resistance r2 is 510Ω. Therefore 1
Next side converted synthesis winding resistance r, the more (Equation 6), r = r1 + a 2 r2 = 800 + (3200/2150) is 2 × 510 = 1130Ω. Considering the temperature coefficient of resistance with respect to (Equation 9), the following equation is established. V 2 / V 1 = (N 1 / N 2) [R 2 (1 + α 2 t) / {R 1 (1 + α 1 t) + r (1 + α 3 t)}] (Equation 10) where α 1 is the current limiting resistance R 1 Temperature coefficient of resistance, α 2
Is the temperature coefficient of resistance of the feedback resistor, and α 3 is the temperature coefficient of resistance of the winding resistance. Further, t is a change temperature with respect to the reference temperature. The resistance temperature coefficient α 1 of the current limiting resistor R1 is set so that the value of V2 / V1 becomes substantially constant in the operating temperature range.
Depending on the resistance temperature coefficient alpha 3 in winding resistance and the feedback resistor R2
Determination of the resistance temperature coefficient alpha 2. [0020] Therefore, (N1 / N2) [R2 (1 + α 2 t) / {R1 (1 + α
1 t) + r (1 + α 3 t)} ] = (N1 / N2) {R2
/ (R1 + r)}, the following equation is obtained. Α 2 = (α 1 R 1 + α 3 r) / (R 1 + r) (Equation 11) Here, the current limiting resistor R 1 is 200 kΩ, and the temperature coefficient α 1 of the current limiting resistor R 1 is 0.75 × 10 − 4. Assuming that the primary-side converted combined winding resistance r is 1130Ω and its temperature coefficient of resistance is 0.427 × 10 −2 , these are substituted into (Equation 11), and α 2 = 0.985 × 10 − Ask for 4 . Therefore, a resistor that approximates the resistance temperature coefficient of the feedback resistor R2 to 0.985 × 10 −4 is used. FIG. 2 shows an example of a voltage conversion circuit provided with a feedback resistor having the above-mentioned predetermined temperature coefficient of resistance. 2A shows an example in which the feedback resistor is formed by a series circuit of resistors R21 and R22, and FIG. 2B shows an example in which the feedback resistor is formed by a parallel circuit of resistors R21 and R22. When a plurality of resistors are combined in this way, by selecting the resistance values of R21 and R22 and the resistance temperature coefficient, the combined resistance value can be set to a desired value (for example, 10%).
kΩ), and the resistance temperature coefficient α 2 of the combined resistor is approximated to the predetermined value. According to the present invention, even if the winding resistance of the transformer for an instrument is relatively large and the input current value changes due to a change in the ambient temperature, the transformer for the instrument can be used. The correction is performed in the current-voltage conversion circuit section by the operational amplifier provided on the secondary side of the above, and the entire voltage conversion ratio is kept constant, so that a constant measurement accuracy is kept regardless of the ambient temperature change. [0024]
【図面の簡単な説明】
【図１】この発明の電圧変成回路の構成例を示す図であ
る。
【図２】この発明の実施例に係る電圧変成回路の構成を
示す図である。
【図３】従来の電圧変成回路の構成例を示す図である。
【符号の説明】
ＯＰ−オペアンプ
Ｒ1 −電流制限抵抗
Ｒ2 −帰還抵抗
ＰＴ−計器用変圧器BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram showing a configuration example of a voltage conversion circuit according to the present invention. FIG. 2 is a diagram illustrating a configuration of a voltage conversion circuit according to an embodiment of the present invention. FIG. 3 is a diagram illustrating a configuration example of a conventional voltage conversion circuit. [Description of Signs] OP-Op Amp R1-Current Limiting Resistor R2-Feedback Resistor PT-Instrument Transformer
───────────────────────────────────────────────────── フロントページの続き (56)参考文献 特開 平６−96972（ＪＰ，Ａ) (58)調査した分野(Int.Cl.7，ＤＢ名) H01F 27/42 ────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-6-96972 (JP, A) (58) Fields investigated (Int. Cl. 7 , DB name) H01F 27/42
Claims (1)
の間に帰還抵抗を接続し、前記オペアンプの反転入力端
子と非反転入力端子との間に計器用変圧器の２次巻線を
接続し、前記計器用変圧器の１次巻線に電流制限抵抗を
接続してなる電圧変成回路であって、前記帰還抵抗の抵
抗温度係数を、前記計器用変圧器の１次側換算合成巻線
抵抗と前記電流制限抵抗との合成抵抗の抵抗温度係数に
略等しくしたことを特徴とする電圧変成回路。(57) [Claim 1] A feedback resistor is connected between an inverting input terminal and an output terminal of an operational amplifier, and an instrument transformer is connected between the inverting input terminal and the non-inverting input terminal of the operational amplifier. A voltage limiting circuit, wherein a secondary winding of a measuring device is connected, and a current limiting resistor is connected to a primary winding of the measuring transformer, wherein a temperature coefficient of resistance of the feedback resistor is determined by the measuring device. A voltage conversion circuit, wherein a resistance temperature coefficient of a combined resistance of the primary-side converted combined winding resistance and the current limiting resistance is substantially equal.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP27094094A JP3533725B2 (en) | 1994-11-04 | 1994-11-04 | Voltage transformation circuit |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP27094094A JP3533725B2 (en) | 1994-11-04 | 1994-11-04 | Voltage transformation circuit |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH08138955A JPH08138955A (en) | 1996-05-31 |
| JP3533725B2 true JP3533725B2 (en) | 2004-05-31 |
Family
ID=17493129
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP27094094A Expired - Fee Related JP3533725B2 (en) | 1994-11-04 | 1994-11-04 | Voltage transformation circuit |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP3533725B2 (en) |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102682985B (en) * | 2012-05-16 | 2015-04-22 | 深圳市深泰明科技有限公司 | High-voltage electronic type voltage transformer |
| CN104917405B (en) * | 2015-05-14 | 2018-09-07 | 华为技术有限公司 | Circuit for silicon-controlled driving circuit and AC module |
-
1994
- 1994-11-04 JP JP27094094A patent/JP3533725B2/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| JPH08138955A (en) | 1996-05-31 |
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