JP2005044670A - High frequency heating device - Google Patents

High frequency heating device Download PDF

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JP2005044670A
JP2005044670A JP2003278578A JP2003278578A JP2005044670A JP 2005044670 A JP2005044670 A JP 2005044670A JP 2003278578 A JP2003278578 A JP 2003278578A JP 2003278578 A JP2003278578 A JP 2003278578A JP 2005044670 A JP2005044670 A JP 2005044670A
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input current
reference value
unit
zener diode
shunt resistor
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JP4015598B2 (en
Inventor
Haruo Suenaga
治雄 末永
Hideaki Moriya
英明 守屋
Hisashi Morikawa
久 森川
Shinichi Sakai
伸一 酒井
Makoto Mihara
誠 三原
Nobuo Shirokawa
信夫 城川
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Panasonic Holdings Corp
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Matsushita Electric Industrial Co Ltd
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Priority to JP2003278578A priority Critical patent/JP4015598B2/en
Priority to KR1020057019341A priority patent/KR100989329B1/en
Priority to PCT/JP2004/005142 priority patent/WO2004093498A1/en
Priority to DE602004022271T priority patent/DE602004022271D1/en
Priority to EP04726762A priority patent/EP1614326B1/en
Priority to US10/550,576 priority patent/US7414228B2/en
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    • HELECTRICITY
    • H05ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05BELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B6/00Heating by electric, magnetic or electromagnetic fields
    • H05B6/64Heating using microwaves
    • H05B6/66Circuits
    • H05B6/68Circuits for monitoring or control
    • H05B6/681Circuits comprising an inverter, a boost transformer and a magnetron
    • H05B6/682Circuits comprising an inverter, a boost transformer and a magnetron wherein the switching control is based on measurements of electrical values of the circuit
    • H05B6/685Circuits comprising an inverter, a boost transformer and a magnetron wherein the switching control is based on measurements of electrical values of the circuit the measurements being made at the low voltage side of the circuit

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Control Of High-Frequency Heating Circuits (AREA)

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a high frequency heating device in which an input current error can be obtained accurately, and in which a high frequency oscillation control of superior precision to keep the input current constant can be carried out even if atmospheric temperatures vary with progress of cooking time. <P>SOLUTION: As a shunt resistor 102 in order to detect the input current I<SB>in</SB>, the resistor having the same temperature characteristic or nearly the same temperature characteristic as that of a Zener diode 107 used for generation of a reference value REF, is used. By this, even if elevation of the reference value REF due to a Zener voltage increase occurs according to the elevation of the atmospheric temperatures, because in the shunt resistor 102 the resistance value increases in such a form that the temperature characteristic follows that of the Zener diode 107, controlling the input current constant becomes possible. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

本発明は、電子レンジ等のマグネトロンを備えた機器に用いて好適な高周波加熱装置に関する。   The present invention relates to a high-frequency heating apparatus suitable for use in equipment equipped with a magnetron such as a microwave oven.

従来、上述した高周波加熱装置には、商用電源が入力される入力側の電流をカレントトランスにて検出し、当該入力電流が所定値になるように半導体スイッチング素子のオン/オフ制御でマグネトロンの電磁波出力を一定に制御する構成を採ったもの(例えば、特許文献1参照)が提案されている。なお、特許文献1で開示された高周波加熱装置では入力電流の検出にカレントトランスを使用しているが、このカレントトランスに代わってシャント抵抗を使用した高周波加熱装置も知られている。
特開平8−96947号公報(第7頁、図1)
Conventionally, in the above-described high-frequency heating device, the current on the input side to which a commercial power source is input is detected by a current transformer, and the electromagnetic current of the magnetron is controlled by on / off control of the semiconductor switching element so that the input current becomes a predetermined value. There has been proposed a configuration in which the output is controlled to be constant (see, for example, Patent Document 1). In addition, although the current transformer is used for the detection of input current in the high frequency heating apparatus disclosed by patent document 1, the high frequency heating apparatus which uses shunt resistance instead of this current transformer is also known.
JP-A-8-96947 (page 7, FIG. 1)

しかしながら、入力電流の検出にシャント抵抗を用い、さらに入力電流一定制御のための基準値の生成に定電圧ダイオード(ツェナーダイオード)を用いている高周波加熱装置にあっては、ツェナーダイオードが温度特性を有していることから、調理時間経過に伴う雰囲気温度(回路周辺の温度)の上昇によって上述した基準電圧(すなわち入力電流)を増加させてしまう。この基準電圧の増加に対し、シャント抵抗は、一般的に安定した温度特性のものが用いられており、そのため、入力電流は一定に制御されず、基準電圧に追従して増加していくという問題がある。   However, in a high-frequency heating device that uses a shunt resistor to detect the input current and further uses a constant voltage diode (zener diode) to generate a reference value for constant input current control, the zener diode has a temperature characteristic. Therefore, the reference voltage (that is, the input current) described above is increased due to an increase in the ambient temperature (temperature around the circuit) with the cooking time. As the reference voltage increases, a shunt resistor having a stable temperature characteristic is generally used. Therefore, the input current is not controlled to a constant value and increases following the reference voltage. There is.

また、カレントトランスについても、温度特性は設計段階で一義的に決まってしまうため、同様の問題が有る。   The current transformer also has a similar problem because the temperature characteristics are uniquely determined at the design stage.

ここで、図5はツェナー電圧温度係数の一例を示す図である。この図において、横軸がツェナー電圧(Vz)であり、縦軸がツェナー電圧温度係数γz(%/℃)である。この例では約5Vを中心に±方向に変化している。なお、周知のようにツェナー電圧Vzはチップ接合部の温度変化により変化し、その変化率即ちツェナー電圧温度係数γzは次式で表すことができる。   Here, FIG. 5 is a diagram illustrating an example of a Zener voltage temperature coefficient. In this figure, the horizontal axis is the Zener voltage (Vz), and the vertical axis is the Zener voltage temperature coefficient γz (% / ° C.). In this example, it changes in the ± direction around about 5V. As is well known, the Zener voltage Vz changes with the temperature change of the chip junction, and the rate of change, that is, the Zener voltage temperature coefficient γz can be expressed by the following equation.

γz=△Vz/△Tj
但し、△Vz:ツェナー電圧変化分、
△Tj:接合部温度(自己発熱温度+周囲温度)変化分
実際のツェナー電圧温度係数γz(周囲温度T1〜T2)は一般的に次式で算出できる。
γz = ΔVz / ΔTj
However, ΔVz: Zener voltage change amount,
ΔTj: Junction temperature (self-heating temperature + ambient temperature) change The actual Zener voltage temperature coefficient γz (ambient temperatures T 1 to T 2 ) can be generally calculated by the following equation.

γz=[(Vz(T2)−Vz(T1))/(Vz(25℃)|T2−T1|)]×100
また、図6は、温度変化に伴う基準値REFとシャント抵抗値との関係を示す図である。この図において、横軸が雰囲気温度Ta(℃)であり、縦軸が電圧及び抵抗値である。雰囲気温度Taが高くなると、基準値REFがツェナー電圧の上昇とともに増加するが、シャント抵抗の値は、既述したように、安定した温度特性のものが用いられていて、ほぼ一定である。
γz = [(Vz (T 2 ) −Vz (T 1 )) / (Vz (25 ° C.) | T 2 −T 1 |)] × 100
FIG. 6 is a diagram showing the relationship between the reference value REF and the shunt resistance value accompanying the temperature change. In this figure, the horizontal axis is the ambient temperature Ta (° C.), and the vertical axis is the voltage and resistance value. As the ambient temperature Ta increases, the reference value REF increases as the Zener voltage increases. However, as described above, the shunt resistance has a stable temperature characteristic and is almost constant.

従って、基準値REFが雰囲気温度Taの上昇に伴って増加すると、上記したとおり、シャント抵抗の値がほぼ一定であることから、基準値の増加に追従して入力電流Iinも増加していまい、入力電流一定制御が困難になる。 Therefore, when the reference value REF is increased with increasing ambient temperature Ta, as described above, since the value of the shunt resistor is substantially constant, the input current I in to follow the increase of the reference value even Mai has increased Therefore, it becomes difficult to control the input current constant.

また、図7は雰囲気温度Taと入力電流Iinとの関係を示す図である。この図において、横軸が経過時間t(sec)であり、縦軸が温度(℃)及び電流(A)である。 Further, FIG. 7 is a graph showing the relationship between the input current I in the ambient temperature Ta. In this figure, the horizontal axis represents elapsed time t (sec), and the vertical axis represents temperature (° C.) and current (A).

点線で示すように、雰囲気温度Taが変化しても入力電流Iinは一定であることが理想であるが、上述したように基準値REFが雰囲気温度の上昇に伴って増加することから、入力電流Iinは、実線で示すように雰囲気温度Taに追従して、増加してしまう。また半導体素子やマグネトロン等はその損失増大による異常温度上昇から破壊等を招く場合もある。 As indicated by the dotted line, it is ideal that the input current I in is constant even when the ambient temperature Ta changes. However, as described above, the reference value REF increases as the ambient temperature increases. current I in is to follow the atmospheric temperature Ta as shown by the solid line, increases. In addition, semiconductor elements, magnetrons, and the like may be destroyed due to abnormal temperature rise due to increased loss.

本発明は係る点に鑑みてなされたもので、調理時間経過に伴い、雰囲気温度が変化しても入力電流を一定に保つ、マグネトロンに対して精度の良い高周波発振制御を行い、また半導体素子やマグネトロン等の異常温度上昇による破壊を防止することができる高周波加熱装置を提供することを目的とする。   The present invention has been made in view of the above points, and as the cooking time elapses, the input current is kept constant even when the ambient temperature changes. An object of the present invention is to provide a high-frequency heating device capable of preventing destruction due to an abnormal temperature rise such as a magnetron.

前記課題を解決するために請求項1に係る発明の高周波加熱装置は、少なくともプリント基板上に、商用電源よりインバータ電源電圧を生成する整流平滑部と、半導体スイッチング素子を含みこの半導体スイッチング素子をオン/オフすることにより前記整流平滑部からの電力を高周波電力に変換するインバータ部と、前記整流平滑部から前記インバータ部に流入する入力電流を検出するためのシャント抵抗と、ツェナーダイオードを含んで直流電源を生成する直流電源部と、前記直流電源部にて生成された直流電源から前記入力電流を一定に制御するための基準値を生成する基準値生成部と、前記基準値生成部にて生成された基準値を基に前記入力電流値との差を求め、この入力電流値との差を加味して前記インバータ部を制御する制御部とを具備する高周波加熱装置であって、
前記シャント抵抗は、前記ツェナーダイオードの温度特性と同じか又は近い温度特性を有することを特徴とする。
In order to solve the above-mentioned problem, a high-frequency heating device according to a first aspect of the present invention includes a rectifying / smoothing unit that generates an inverter power supply voltage from a commercial power supply and a semiconductor switching element at least on a printed circuit board. Including an inverter unit that converts power from the rectifying / smoothing unit to high-frequency power by turning it off, a shunt resistor for detecting an input current flowing from the rectifying / smoothing unit into the inverter unit, and a zener diode A DC power source that generates a power source, a reference value generator that generates a reference value for controlling the input current from the DC power source generated by the DC power source, and a reference value generator A control unit that obtains a difference from the input current value based on the reference value and controls the inverter unit in consideration of the difference from the input current value A high-frequency heating apparatus comprising,
The shunt resistor has a temperature characteristic that is the same as or close to the temperature characteristic of the Zener diode.

この構成によれば、雰囲気温度の上昇によりツェナー電圧が増加して基準値が増加しても、その増加に追従してシャント抵抗の値が増加して基準値の増加量を相殺するため、入力電流を一定に制御することが可能になる。したがって、雰囲気温度が上昇しても入力電流を一定に保つ、マグネトロンに対して精度の良い高周波発振制御を行うことが可能となる。   According to this configuration, even if the Zener voltage increases due to an increase in ambient temperature and the reference value increases, the shunt resistance value increases following the increase to offset the increase in the reference value. It becomes possible to control the current to be constant. Therefore, accurate high-frequency oscillation control can be performed on the magnetron that keeps the input current constant even when the ambient temperature rises.

また、請求項2に係る発明の高周波加熱装置は、請求項1に係る発明の高周波加熱装置において、前記シャント抵抗が、プリント基板上で前記ツェナーダイオードの近傍に配置されることを特徴とする。   According to a second aspect of the present invention, there is provided a high-frequency heating apparatus according to the first aspect, wherein the shunt resistor is disposed in the vicinity of the Zener diode on a printed circuit board.

この構成によれば、シャント抵抗とツェナーダイオードが同じ温度雰囲気中に置かれるので、入力電流と基準値との相関誤差を最小限に抑えることが可能となる。   According to this configuration, since the shunt resistor and the Zener diode are placed in the same temperature atmosphere, it is possible to minimize the correlation error between the input current and the reference value.

また、請求項3に係る発明の高周波加熱装置は、請求項1に係る発明の高周波加熱装置において、前記シャント抵抗が、プリント基板上で前記ツェナーダイオードの配置場所の温度雰囲気に近い温度雰囲気の場所に配置されることを特徴とする。   The high-frequency heating device of the invention according to claim 3 is the high-frequency heating device of the invention according to claim 1, wherein the shunt resistance is a place in a temperature atmosphere close to the temperature atmosphere of the place where the Zener diode is arranged on the printed circuit board. It is characterized by being arranged.

この構成によれば、シャント抵抗をツェナーダイオードの実装場所と同じ温度雰囲気の場所に実装するので、回路設計上でシャント抵抗をツェナーダイオードの近傍に配置できない場合でも入力電流と基準値との相関誤差を最小限に抑えることが可能となる。   According to this configuration, the shunt resistor is mounted in a place with the same temperature atmosphere as the place where the Zener diode is mounted, so even if the shunt resistor cannot be placed near the Zener diode in circuit design, the correlation error between the input current and the reference value Can be minimized.

本発明に係る発明の高周波加熱装置によれば、入力電流を検出するためのシャント抵抗にツェナーダイオードの温度特性と同じか又は近い温度特性を持つものを用いたので、雰囲気温度の上昇によりツェナー電圧が変化して基準値に変化が生じてもその変化に追従してシャント抵抗の値が変化することから、入力電流と基準値との相関誤差を最小限に抑えることができ、これによってマグネトロンに対し精度の良い高周波発振制御を行うことが可能となる。   According to the high-frequency heating device of the present invention, since the shunt resistor for detecting the input current has a temperature characteristic that is the same as or close to the temperature characteristic of the Zener diode, the Zener voltage is increased by increasing the ambient temperature. Even if a change occurs in the reference value due to a change in the value of the shunt resistor, the value of the shunt resistor changes following the change, so that the correlation error between the input current and the reference value can be minimized. On the other hand, high-frequency oscillation control with high accuracy can be performed.

更に、シャント抵抗をツェナーダイオードと同じ温度環境下におけば、入力電流と基準値との相関誤差を更に最小限に抑えることができる。   Furthermore, if the shunt resistor is placed in the same temperature environment as the Zener diode, the correlation error between the input current and the reference value can be further minimized.

以下、本発明の実施の形態について、図面を参照しながら詳細に説明する。   Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

図1は、本発明の一実施の形態に係る高周波加熱装置の構成を示す回路図である。   FIG. 1 is a circuit diagram showing a configuration of a high-frequency heating device according to an embodiment of the present invention.

図1において、本実施の形態に係る高周波加熱装置は、電源部1と、整流平滑部2と、インバータ部3と、高圧整流回路4と、マグネトロン8と、電源部1に接続したシャント抵抗102から入力電流Iinを検出するための入力電流検出部5と、入力電流Iinの誤差を検出するための基準値を生成する基準値生成部6と、基準値に対する入力電流Iinの誤差を元にインバータ部3を制御する制御部7とを不図示のプリント基板上に備えている。 1, the high-frequency heating device according to the present embodiment includes a power supply unit 1, a rectifying / smoothing unit 2, an inverter unit 3, a high-voltage rectifier circuit 4, a magnetron 8, and a shunt resistor 102 connected to the power supply unit 1. an input current detector 5 for detecting the input current I in from the reference value generating unit 6 for generating a reference value for detecting an error of the input current I in, the error of the input current I in to the reference value A control unit 7 that originally controls the inverter unit 3 is provided on a printed board (not shown).

整流平滑部2は、商用電源20からの交流電源を全波整流するダイオードブリッジ101と、ダイオードブリッジ101の負出力側端子に対し直列に介挿され、入力電流Iinを検出するためのシャント抵抗102とフィルタ用のチョークコイル110と平滑コンデンサ109とを備えており、インバータ部3を動作させる直流電源を生成している。 Rectifying and smoothing portion 2 includes a diode bridge 101 for full-wave rectifying an AC power from the commercial power source 20 is interposed in series with the negative output terminal of the diode bridge 101, a shunt resistor for detecting an input current I in 102, a filter choke coil 110, and a smoothing capacitor 109 are provided, and a DC power source for operating the inverter unit 3 is generated.

電源部1は、制御部7と後述するトランジスタ203を駆動するための電源を生成するために、整流用ダイオード111,112と、セメント抵抗103及びツェナーダイオード104と、アルミ電解コンデンサ105と、基準値生成部6に与える直流電圧を生成するための抵抗106、ツェナーダイオード107及びコンデンサ108とを備えている。なお、本発明では、上記の電源部1のうち、ツェナーダイオード104,107を含んで直流電源(20V,12V)を生成する回路部を直流電源部と称している。また直流電源部は、インバータ部を含む主基板とは別基板として形成し、主基板上の基準値生成部へ直流電源を供給するようにしてもよい。   The power supply unit 1 generates rectifier diodes 111 and 112, a cement resistor 103 and a Zener diode 104, an aluminum electrolytic capacitor 105, a reference value, and a power source for generating a power source for driving the control unit 7 and a transistor 203 described later. A resistor 106, a Zener diode 107, and a capacitor 108 for generating a DC voltage to be applied to the generating unit 6 are provided. In the present invention, among the power supply unit 1 described above, a circuit unit that includes the zener diodes 104 and 107 and generates a DC power supply (20V, 12V) is referred to as a DC power supply unit. The DC power supply unit may be formed as a separate substrate from the main substrate including the inverter unit, and the DC power supply may be supplied to the reference value generating unit on the main substrate.

セメント抵抗103と、ツェナーダイオード104及びアルミ電解コンデンサ105は直列に接続されている。抵抗106は、その一端がツェナーダイオード104のカソード側に接続され、他端がツェナーダイオード107のカソード側に接続されている。ツェナーダイオード107は、そのカソードが上述した抵抗106の他端に接続されて、アノードがツェナーダイオード104のアノードと共に接地されている。コンデンサ108はツェナーダイオード107に並列接続されている。   The cement resistor 103, the Zener diode 104, and the aluminum electrolytic capacitor 105 are connected in series. The resistor 106 has one end connected to the cathode side of the Zener diode 104 and the other end connected to the cathode side of the Zener diode 107. The Zener diode 107 has a cathode connected to the other end of the resistor 106 described above, and an anode grounded together with the anode of the Zener diode 104. The capacitor 108 is connected to the Zener diode 107 in parallel.

インバータ部3は、共振コンデンサ201と、トランジスタ203と、転流ダイオード204とから構成される。トランジスタ203は、制御部7より与えられる20〜50kHzのスイッチング制御信号によってスイッチング動作する。これにより、昇圧トランス202の一次巻線には高周波電圧が発生する。なお、トランジスタ203は、主に転流ダイオード204と一体に形成されて、IGBT(Insulated Gate Bipolar Transistor)205と呼ばれており、本願ではこのIGBT205を使用しているが、他の半導体スイッチング素子を用いても同様の効果が得られる。   The inverter unit 3 includes a resonance capacitor 201, a transistor 203, and a commutation diode 204. The transistor 203 performs a switching operation by a switching control signal of 20 to 50 kHz supplied from the control unit 7. As a result, a high frequency voltage is generated in the primary winding of the step-up transformer 202. The transistor 203 is mainly formed integrally with the commutation diode 204 and is called an IGBT (Insulated Gate Bipolar Transistor) 205. In the present application, the IGBT 205 is used, but other semiconductor switching elements are used. Even if it is used, the same effect can be obtained.

高圧整流回路4は、コンデンサ301及び302と、ダイオード303及び304とから構成されており、昇圧トランス202の二次巻線で発生した電圧を両波倍電圧整流することで高圧直流電圧を発生しマグネトロン8に印加する。マグネトロン8には昇圧トランス202のヒータ巻線からヒータ用の交流電圧も印加される。マグネトロン8は、ヒータ用の交流電圧が印加されることで陰極が傍熱されてエミッション可能な状態となり、この状態で高圧直流電圧が印加されると電磁波エネルギーを発生する。   The high voltage rectifier circuit 4 includes capacitors 301 and 302 and diodes 303 and 304. The high voltage rectifier circuit 4 generates a high voltage DC voltage by rectifying the voltage generated in the secondary winding of the step-up transformer 202 by double wave rectification. Applied to magnetron 8. An AC voltage for the heater is also applied to the magnetron 8 from the heater winding of the step-up transformer 202. The magnetron 8 is in a state in which the cathode is side-heated by the application of the AC voltage for the heater and can be emitted, and when a high-voltage DC voltage is applied in this state, electromagnetic energy is generated.

基準値生成部6は、電源部1より入力される電圧を分圧してオペアンプ601の非反転入力端に印加する電圧を生成する抵抗602及び603と、電源部1の直流出力を取り出すための抵抗604,605及びアルミ電解コンデンサ606と、オペアンプ601の動作定数を決定する抵抗607,608と、オペアンプ601の出力を取り出すためのスイッチ609と、スイッチ609で取り出されたオペアンプ601の出力を波形整形する抵抗610とコンデンサ611からなる積分回路と、を備えている。スイッチ609の切り替え時間は、高周波出力設定によるデューティ比によって変化する。   The reference value generation unit 6 divides the voltage input from the power supply unit 1 and generates resistors 602 and 603 for generating a voltage to be applied to the non-inverting input terminal of the operational amplifier 601 and a resistor for taking out the DC output of the power supply unit 1 604 and 605, an aluminum electrolytic capacitor 606, resistors 607 and 608 for determining an operation constant of the operational amplifier 601, a switch 609 for taking out the output of the operational amplifier 601, and a waveform shaping of the output of the operational amplifier 601 taken out by the switch 609. And an integrating circuit including a resistor 610 and a capacitor 611. The switching time of the switch 609 varies depending on the duty ratio according to the high frequency output setting.

制御部7は、基準値生成部6からの基準値REFと入力電流検出部5で検出された入力電流Iinとを比較し、基準値REF=Iin×Rになるように制御する。そして、制御部7からの信号にてインバータ部3のトランジスタ203がオン/オフ制御される。このように、整流平滑部2で商用電源20を単方向電圧に変換し、それをインバータ部3で高周波電圧に変換して昇圧トランス202で昇圧した後、再度高圧整流回路4で倍電圧整流して高圧の直流電圧に変換し、マグネトロン8を駆動する。 The control unit 7 compares the reference value REF from the reference value generation unit 6 with the input current I in detected by the input current detection unit 5 and controls the reference value REF = I in × R. Then, the transistor 203 of the inverter unit 3 is on / off controlled by a signal from the control unit 7. In this way, the rectifying / smoothing unit 2 converts the commercial power source 20 into a unidirectional voltage, the inverter unit 3 converts the commercial power source 20 into a high-frequency voltage, boosts the voltage with the step-up transformer 202, and then doubles the voltage again with the high-voltage rectifier circuit 4. The high voltage DC voltage is converted to drive the magnetron 8.

ここで、本発明の特長的な構成は、整流平滑部2のシャント抵抗102が、ツェナーダイオード107の温度特性に近似した温度特性を有するものであり、雰囲気温度の上昇によってツェナーダイオード107のツェナー電圧に増加が生じて基準値REFが増加すると、シャント抵抗102の抵抗値Rもそれに近似して増加する。したがって、雰囲気温度が上昇してもマグネトロン8に対して精度の良い高周波発振制御が行われる。   Here, the characteristic configuration of the present invention is that the shunt resistor 102 of the rectifying and smoothing unit 2 has a temperature characteristic that approximates the temperature characteristic of the Zener diode 107, and the Zener voltage of the Zener diode 107 increases as the ambient temperature rises. When the reference value REF increases, the resistance value R of the shunt resistor 102 also increases in a similar manner. Therefore, accurate high-frequency oscillation control is performed on the magnetron 8 even when the ambient temperature rises.

ここで、図2は、本実施の形態によるシャント抵抗102の抵抗値Rと基準値REFとの関係を示す図である。雰囲気温度Ta(℃)の上昇とともにツェナーダイオード107のツェナー電圧が高くなって、基準値REFが増加するが、シャント抵抗102の抵抗値も同じように増加し、検出される入力電流情報(Iin×R)も増加するので、制御部7によってこの入力電流情報を基準値REFとを比較して追従制御するため、図3の雰囲気温度Taと入力電流Iinとの関係図に示すように、雰囲気温度Taが上昇しても入力電流Iinが一定になる。すなわち、基準値REFの増加分をシャント抵抗102の抵抗値Rで同じように補えばIinは一定にできる。 Here, FIG. 2 is a diagram showing the relationship between the resistance value R of the shunt resistor 102 and the reference value REF according to the present embodiment. As the ambient temperature Ta (° C.) rises, the Zener voltage of the Zener diode 107 increases and the reference value REF increases. However, the resistance value of the shunt resistor 102 increases in the same way, and the detected input current information (I in XR) also increases, so that the control unit 7 performs follow-up control by comparing the input current information with the reference value REF. As shown in the relationship diagram between the ambient temperature Ta and the input current Iin in FIG. Even if the ambient temperature Ta rises, the input current Iin becomes constant. That is, should be compensated in an increase of the reference value REF in the same way by the resistance value R of the shunt resistor 102 I in can be constant.

また、シャント抵抗102は、ツェナーダイオード107が実装されるプリント基板上の近傍に配置される。すなわち、ツェナーダイオード107と同じ温度雰囲気となる位置に配置される。図4は、実装の一例を示す図であり、プリント基板8上のセメント抵抗103及び放熱板206に搭載されるIGBT205が実装される領域にシャント抵抗102とツェナーダイオード107が実装されている。この図に示す例では近傍とは言えないが、シャント抵抗102はIGBT205の発熱による熱雰囲気中にあり、ツェナーダイオード107はセメント抵抗103の発熱による熱雰囲気中にあり、同じような熱環境にあると言える。当然ながら、回路設計上許されるのであれば、シャント抵抗102をツェナーダイオード107の直近に配置することで、全く同じ温度環境に置くことができる。   The shunt resistor 102 is disposed in the vicinity of the printed circuit board on which the Zener diode 107 is mounted. That is, it is disposed at a position where the temperature atmosphere is the same as that of the Zener diode 107. FIG. 4 is a diagram illustrating an example of mounting, where a shunt resistor 102 and a Zener diode 107 are mounted in a region where the cement resistor 103 and the IGBT 205 mounted on the heat sink 206 are mounted on the printed circuit board 8. In the example shown in this figure, although it cannot be said that it is in the vicinity, the shunt resistor 102 is in a thermal atmosphere due to the heat generation of the IGBT 205, and the Zener diode 107 is in a thermal atmosphere due to the heat generation of the cement resistor 103, and has a similar thermal environment. It can be said. Needless to say, if the circuit design permits, the shunt resistor 102 can be placed in the very same temperature environment by being arranged in the immediate vicinity of the Zener diode 107.

このように、本実施の形態に係る高周波加熱装置によれば、入力電流Iinを検出するためのシャント抵抗102として、基準値REFを生成するために用いられるツェナーダイオード107の温度特性と同じか又は近い温度特性を持つものを用いたので、雰囲気温度の上昇に伴ってツェナー電圧増加による基準値REFの増加が生じても、シャント抵抗102の温度特性がツェナーダイオード107の温度特性に近似するかたちで抵抗値が増加するので、入力電流と基準値との相関誤差を最小限に抑えることができる。すなわち入力電流を一定に制御でき、マグネトロン4に対し精度の良い高周波発振制御が可能となる。 Thus, according to the high-frequency heating apparatus according to the present embodiment, as the shunt resistor 102 for detecting the input current I in, or the same as the temperature characteristic of the zener diode 107 used for generating the reference value REF Alternatively, since the one having a close temperature characteristic is used, the temperature characteristic of the shunt resistor 102 approximates the temperature characteristic of the Zener diode 107 even if the reference value REF increases due to the increase in the Zener voltage as the ambient temperature increases. Since the resistance value increases, the correlation error between the input current and the reference value can be minimized. That is, the input current can be controlled to be constant, and the high-frequency oscillation control with high accuracy can be performed for the magnetron 4.

さらに、シャント抵抗102をツェナーダイオード107の近傍に配置することで、入力電流誤差情報の誤差を更に最小限に抑えることができる。   Further, by arranging the shunt resistor 102 in the vicinity of the Zener diode 107, the error of the input current error information can be further minimized.

本発明の一実施の形態に係る高周波加熱装置の構成を示す回路図である。It is a circuit diagram which shows the structure of the high frequency heating apparatus which concerns on one embodiment of this invention. 図1の高周波加熱装置における基準値REFとシャント抵抗の値との関係を示す図である。It is a figure which shows the relationship between the reference value REF and the value of shunt resistance in the high frequency heating apparatus of FIG. 図1の高周波加熱装置における雰囲気温度Taと入力電流Iinとの関係を示す図である。It is a diagram showing a relationship between atmospheric temperature Ta and the input current I in the high frequency heating apparatus of Fig. 図1の高周波加熱装置の各部品が実装されたプリント基板の一部分を示す図である。It is a figure which shows a part of printed circuit board in which each component of the high frequency heating apparatus of FIG. 1 was mounted. ツェナーダイオードの温度特性の一例を示す図である。It is a figure which shows an example of the temperature characteristic of a Zener diode. 従来の高周波加熱装置における基準値REFとシャント抵抗の値との関係を示す図である。It is a figure which shows the relationship between the reference value REF and the value of shunt resistance in the conventional high frequency heating apparatus. 従来の高周波加熱装置における雰囲気温度Taと入力電流Iinとの関係を示す図である。It is a diagram showing a relationship between atmospheric temperature Ta and the input current I in the conventional high-frequency heating apparatus.

符号の説明Explanation of symbols

1 単方向電源部
2 インバータ部
3 高圧整流回路
4 マグネトロン
5 入力電流検出部
6 基準値生成部
7 制御部
20 商用電源
101 ダイオードブリッジ
102 シャント抵抗
103 セメント抵抗
104、107 ツェナーダイオード
205 IGBT
DESCRIPTION OF SYMBOLS 1 Unidirectional power supply part 2 Inverter part 3 High voltage rectifier circuit 4 Magnetron 5 Input current detection part 6 Reference value generation part 7 Control part 20 Commercial power supply 101 Diode bridge 102 Shunt resistance 103 Cement resistance 104, 107 Zener diode 205 IGBT

Claims (3)

少なくともプリント基板上に、商用電源よりインバータ電源電圧を生成する整流平滑部と、半導体スイッチング素子を含みこの半導体スイッチング素子をオン/オフすることにより前記整流平滑部からの電力を高周波電力に変換するインバータ部と、前記整流平滑部から前記インバータ部に流入する入力電流を検出するためのシャント抵抗と、ツェナーダイオードを含んで直流電源を生成する直流電源部と、前記直流電源部にて生成された直流電源から前記入力電流を一定に制御するための基準値を生成する基準値生成部と、前記基準値生成部にて生成された基準値を基に前記入力電流値との差を求め、この入力電流値との差を加味して前記インバータ部を制御する制御部とを具備する高周波加熱装置であって、
前記シャント抵抗は、前記ツェナーダイオードの温度特性と同じか又は近い温度特性を有することを特徴とする高周波加熱装置。
A rectifying / smoothing unit that generates an inverter power supply voltage from a commercial power supply on at least a printed circuit board, and an inverter that converts the power from the rectifying / smoothing unit into high-frequency power by turning on / off the semiconductor switching element. Unit, a shunt resistor for detecting an input current flowing into the inverter unit from the rectifying and smoothing unit, a DC power source unit including a Zener diode to generate a DC power source, and a DC generated by the DC power source unit A reference value generation unit that generates a reference value for controlling the input current from a power source constant, and a difference between the input current value based on the reference value generated by the reference value generation unit A high-frequency heating apparatus including a control unit that controls the inverter unit in consideration of a difference with a current value,
The high frequency heating apparatus according to claim 1, wherein the shunt resistor has a temperature characteristic that is the same as or close to a temperature characteristic of the Zener diode.
前記シャント抵抗が、プリント基板上で前記ツェナーダイオードの近傍に配置されることを特徴とする請求項1記載の高周波加熱装置。 The high frequency heating apparatus according to claim 1, wherein the shunt resistor is disposed in the vicinity of the Zener diode on a printed circuit board. 前記シャント抵抗が、プリント基板上で前記ツェナーダイオードの配置場所の温度雰囲気に近い温度雰囲気の場所に配置されることを特徴とする請求項1記載の高周波加熱装置。 2. The high frequency heating apparatus according to claim 1, wherein the shunt resistor is arranged on a printed circuit board at a temperature atmosphere location close to a temperature atmosphere of the Zener diode arrangement location.
JP2003278578A 2003-04-11 2003-07-23 High frequency heating device Expired - Lifetime JP4015598B2 (en)

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JP2003278578A JP4015598B2 (en) 2003-07-23 2003-07-23 High frequency heating device
KR1020057019341A KR100989329B1 (en) 2003-04-11 2004-04-09 High frequency heating apparatus
PCT/JP2004/005142 WO2004093498A1 (en) 2003-04-11 2004-04-09 High frequency heating apparatus
DE602004022271T DE602004022271D1 (en) 2003-04-11 2004-04-09 HIGH FREQUENCY HEATING DEVICE
EP04726762A EP1614326B1 (en) 2003-04-11 2004-04-09 High frequency heating apparatus
US10/550,576 US7414228B2 (en) 2003-04-11 2004-04-09 High frequency heating apparatus

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