JP5431899B2 - Electromagnetic induction heating cooker - Google Patents
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Description
本発明は、インバータ回路を使用して誘導加熱コイルに高周波電流を供給し電磁誘導で鍋を加熱する電磁誘導加熱調理器に係り、特に、電流制限の技術に関するものである。 The present invention relates to an electromagnetic induction heating cooker that uses an inverter circuit to supply a high-frequency current to an induction heating coil to heat a pan by electromagnetic induction, and more particularly to a current limiting technique.
図7は、従来技術の電磁誘導加熱装置の電気接続図である。同図において、DR1は商用交流電源の出力を整流して直流電圧に変換する整流回路であり、C1は整流回路DR1で直流に変換した電圧を平滑する平滑コンデンサであり、TR1及びTR2はハーフブリッジ形のインバータ回路を形成するスイッチング素子で、例えば、MOSFETやIGBTが使用されている。Lは共振コンデンサC2、C3とで直列共振回路を形成する誘導加熱コイルで、この誘導加熱コイルの上に調理鍋を置いて電磁誘導により加熱を行う。 FIG. 7 is an electrical connection diagram of a conventional electromagnetic induction heating apparatus. In the figure, DR1 is a rectifier circuit that rectifies the output of the commercial AC power source and converts it into a DC voltage, C1 is a smoothing capacitor that smoothes the voltage converted into DC by the rectifier circuit DR1, and TR1 and TR2 are half bridges For example, a MOSFET or an IGBT is used as a switching element forming an inverter circuit. L is an induction heating coil that forms a series resonance circuit with the resonance capacitors C2 and C3. A cooking pot is placed on the induction heating coil and heated by electromagnetic induction.
POは平滑コンデンサC1の電圧(インバータの入力電圧)を検出する電圧検出器PT1からの信号と、インバータの入力端の電流を検出する一次電流検出器CT1からの信号とを入力してインバータの入力電力を演算する電力演算回路で、DCはスイッチング素子TR1、TR2を駆動する駆動回路である。 PO inputs the signal from the voltage detector PT1 for detecting the voltage of the smoothing capacitor C1 (input voltage of the inverter) and the signal from the primary current detector CT1 for detecting the current at the input terminal of the inverter to input the inverter. A power calculation circuit that calculates power, and DC is a drive circuit that drives the switching elements TR1 and TR2.
図8は図7に示す電力制御用差動増幅回路DA1の詳細図で、非反転入力端子に電力演算回路POからの入力信号Poが、反転入力端子に電力設定回路WAによって設定した電力設定信号Waがそれぞれ入力される。そして、電力制御用差動増幅回路DA1は、電力演算信号Poが電力設定信号Waより小さいときは両者の編差分を増幅した負の電力制御用差動増幅信号Da1を出力し、電力演算信号Poが電力設定信号Waより大きいときは両者の編差分を増幅した正の電力制御用差動増幅信号Da1を出力する。 FIG. 8 is a detailed diagram of the power control differential amplifier DA1 shown in FIG. 7, in which the input signal Po from the power calculation circuit PO is set to the non-inverting input terminal and the power setting signal set to the inverting input terminal by the power setting circuit WA. Each Wa is input. When the power calculation signal Po is smaller than the power setting signal Wa, the power control differential amplifier circuit DA1 outputs a negative power control differential amplification signal Da1 obtained by amplifying the knitting difference between the two, and the power calculation signal Po. Is greater than the power setting signal Wa, a positive power control differential amplification signal Da1 obtained by amplifying the difference between the two is output.
運転指令回路SCは、起動スイッチSW及び過電流検出回路CPの各信号に応じて、駆動回路DCの動作を制御する。過電流検出回路CPは、過電流設定回路IOによって設定された予め定めた過電流設定信号Ioと出力電流検出信号Ct2とを比較して出力電流検出信号Ct2が過電流設定信号Ioより大きくなると過電流検出信号Cpを出力し、運転指令回路SCは過電流検出信号Cpが入力されると駆動回路DCの動作を停止し、誘導加熱コイルに流れる電流の供給を止める。 The operation command circuit SC controls the operation of the drive circuit DC according to the signals of the start switch SW and the overcurrent detection circuit CP. The overcurrent detection circuit CP compares the predetermined overcurrent setting signal Io set by the overcurrent setting circuit IO with the output current detection signal Ct2, and when the output current detection signal Ct2 becomes larger than the overcurrent setting signal Io, The current detection signal Cp is output, and the operation command circuit SC stops the operation of the drive circuit DC when the overcurrent detection signal Cp is input, and stops supplying the current flowing through the induction heating coil.
図8は図7に示す電流制御用差動増幅回路Da2の詳細図で、非反転入力端子に出力電流検出器CT2からの出力電流検出信号Ct2が、反転入力端子に電流制限回路ICから電流制限信号Icがそれぞれ入力される。そして、電流制御用差動増幅回路DA2は、出力電流検出信号Ct2が電流制限信号Icより小さいときは両者の編差分を増幅した負の電流制御用差動増幅信号Da2を出力し、出力電流検出信号Ct2が電流制限信号Icより大きいときは両者の編差分を増幅した正の電流制御用差動増幅信号Da2を出力する。 FIG. 8 is a detailed diagram of the current control differential amplifier circuit Da2 shown in FIG. 7. The output current detection signal Ct2 from the output current detector CT2 is supplied to the non-inverting input terminal and the current limiting circuit IC is supplied to the inverting input terminal. Each of the signals Ic is input. When the output current detection signal Ct2 is smaller than the current limit signal Ic, the current control differential amplifier circuit DA2 outputs a negative current control differential amplification signal Da2 obtained by amplifying the knitting difference between the two to detect the output current. When the signal Ct2 is larger than the current limit signal Ic, a positive current control differential amplification signal Da2 obtained by amplifying the knitting difference between the two is output.
電流制限制御回路は、図7に示す、ダイオードDR2、ダイオードDR3、抵抗器R1及びV/FコンバータVFによって形成されている。そして、電流制限制御回路は、ダイオードDR2を介して電力制御用差動増幅回路DA1と、ダイオードDR3を介して電流制御用差動増幅回路DA2と接続し、オアー論理を構成し、電力制御用差動増幅信号Da1及び電流制御用差動増幅信号Da2の最大値を選択しViとして出力する。V/FコンバータVFは、Viの値に応じて周波数指令信号Vfを出力し、駆動回路DCでレベル変換してインバータ回路の出力周波数を制御する。 The current limit control circuit is formed by a diode DR2, a diode DR3, a resistor R1, and a V / F converter VF shown in FIG. Then, the current limit control circuit is connected to the power control differential amplifier circuit DA1 via the diode DR2 and the current control differential amplifier circuit DA2 via the diode DR3 to form an OR logic, and to control the power control difference. The maximum value of the dynamic amplification signal Da1 and the current control differential amplification signal Da2 is selected and output as Vi. The V / F converter VF outputs a frequency command signal Vf according to the value of Vi, and performs level conversion by the drive circuit DC to control the output frequency of the inverter circuit.
ステンレスの鍋を調理者が、例えば、規格外のアルミ製又は銅製の鍋に置き換えて煮物等の調理を行うと、鍋の材質の違いにより、例えば、図5に示すように電力設定値Waをc点に設定したとき、インバータ回路の出力電流に大きな違いが生じる。このとき、アルミ製又は銅製の鍋で金属内部に大きな渦電流が発生するが、表面抵抗値が小さいために渦電流損失が小さくなりステンレスの鍋に比べて充分加熱できなくなる。
(例えば、特許文献1)
For example, when a cooker replaces a stainless steel pan with a non-standard aluminum or copper pan and cooks boiled food, the power setting value Wa is set as shown in FIG. When the point c is set, a large difference occurs in the output current of the inverter circuit. At this time, a large eddy current is generated inside the metal in the aluminum or copper pan, but since the surface resistance value is small, the eddy current loss is small and it is not possible to sufficiently heat compared with the stainless steel pan.
(For example, Patent Document 1)
電磁誘導加熱調理器で規格外のアルミ製又は銅製の鍋を使用したとき、インバータ回路の出力電流が急激に増加するが、出力電流が所定値を越えないように、電流制限を設けてインバータ回路を形成する各スイッチング素子の保護を行っている。
そして、電流制限設定値は、ステンレス製の鍋に最大電力が供給できる電流を若干越えた値に設定されている。このとき、ステンレス製の鍋をアルミ製又は銅製の鍋に置き換えて使用するとインバータ回路の出力電流が急激に増加するが、この出力電流の増加に比べて鍋の電力供給が低く、鍋が充分加熱する前に電流制限設定値によってインバータ回路の出力電流が制限され鍋が充分加熱できない。
この鍋が充分加熱できない状態を長時間放置すると、インバータ回路を形成する各スイッチング素子の出力電流が最大定格近傍で出力し、スイッチング時に発生する熱損失によって部品の劣化を誘導し、製品の寿命を短くする。
When a non-standard aluminum or copper pan is used in an electromagnetic induction heating cooker, the output current of the inverter circuit increases rapidly, but a current limit is provided so that the output current does not exceed the specified value. Each of the switching elements forming the circuit is protected.
The current limit set value is set to a value slightly exceeding the current at which the maximum power can be supplied to the stainless steel pan. At this time, if the stainless steel pan is replaced with an aluminum or copper pan, the output current of the inverter circuit increases rapidly. However, compared to this increase in output current, the pan's power supply is low and the pan is heated sufficiently. Before the operation, the output current of the inverter circuit is limited by the current limit setting value, and the pan cannot be heated sufficiently.
If this pan cannot be heated sufficiently for a long time, the output current of each switching element that forms the inverter circuit is output near the maximum rating, and the deterioration of parts is induced by the heat loss that occurs during switching, thus prolonging the life of the product. shorten.
そこで、本発明は、上記課題を解決するためになされたものであって、その目的は、ステンレス製の鍋からアルミ製又は銅製の鍋に置き換えて使用しても部品の劣化が抑制できる電磁誘導加熱調理器を提供することを目的とする。 Accordingly, the present invention has been made to solve the above-described problems, and its purpose is to provide electromagnetic induction that can suppress deterioration of parts even when used by replacing a stainless steel pan with an aluminum or copper pan. An object is to provide a cooking device.
上述した課題を解決するために、第1の発明は、共振コンデンサと、前記共振コンデンサとともに直列共振回路を形成する誘導加熱コイルと、前記誘導加熱コイルに高周波電流を供給するインバータ回路と、前記インバータ回路の入力電流と入力電圧とに基づいて入力電力を演算する電力演算回路と、前記インバータ回路の出力電流値を検出し予め定めた過電流設定値を越えると前記インバータ回路を停止させる過電流検出回路と、前記電力演算値と予め定めた電力設定値とを差動増幅して電力制御用差動増幅値を出力する電力制御用差動増幅回路と、予め定めた電流制限設定値を出力する電流制限設定回路と、前記出力電流値と予め定めた電流制限設定値とを差動増幅して電流制御用差動増幅値を出力する電流制御用差動増幅回路と、前記電力制御用差動増幅値及び前記電流制御用差動増幅値を入力して値の大きい方を前記インバータ回路を制御する周波数変換回路に出力する電流制限制御回路と、を備えた電磁誘導加熱調理器において、
前記電流制限設定回路は、前記電力設定値に応じて前記電流制限設定値が変化すると共に前記電流制限設定値の最大値が前記過電流設定値未満であること、をを特徴とする電磁誘導加熱調理器である。
In order to solve the above-described problems, a first invention includes a resonance capacitor, an induction heating coil that forms a series resonance circuit together with the resonance capacitor, an inverter circuit that supplies a high-frequency current to the induction heating coil, and the inverter A power calculation circuit that calculates input power based on an input current and an input voltage of the circuit, and an overcurrent detection that detects an output current value of the inverter circuit and stops the inverter circuit when a predetermined overcurrent set value is exceeded. A circuit, a power control differential amplification circuit that differentially amplifies the power calculation value and a predetermined power setting value to output a power control differential amplification value, and outputs a predetermined current limit setting value A current limit setting circuit; a current control differential amplification circuit that differentially amplifies the output current value and a predetermined current limit setting value to output a current control differential amplification value; and A current limiting control circuit that inputs a differential amplification value for force control and a differential amplification value for current control and outputs the larger value to a frequency conversion circuit that controls the inverter circuit; and electromagnetic induction heating cooking In the vessel
The current limit setting circuit is characterized in that the current limit set value changes according to the power set value and the maximum value of the current limit set value is less than the overcurrent set value. It is a cooker.
第2の発明は、前記電流制限設定値は、前記電力設定値に応じて直線的又は放物線的に変化し前記電力設定値が予め定めた電力設定基準値を越えると前記変化が終了し最終変化値が維持されること、を特徴とする請求項1記載の電磁誘導加熱調理器である。
According to a second aspect of the invention, the current limit set value changes linearly or parabolically according to the power set value, and when the power set value exceeds a predetermined power set reference value, the change ends and the final change The electromagnetic induction heating cooker according to
第3の発明は、前記電流制限設定値は、前記電力設定値に応じて台形的に変化し前記電力設定値が予め定めた電力設定基準値を越えると前記変化が終了し最終変化値が維持されること、を特徴とする請求項1記載の電磁誘導加熱調理器である。
According to a third aspect of the invention, the current limit set value changes trapezoidally according to the power set value, and when the power set value exceeds a predetermined power set reference value, the change ends and the final change value is maintained. The electromagnetic induction heating cooker according to
第1の発明は、電力設定値に応じて電流制限設定値が変化する。このとき、電力設定値を、例えば、最大から中間に設定すると電流制限設定値は電力設定値の減少に応じて小さくなる。ステンレス製の鍋では電力設定値を中間に設定しても充分加熱できる。しかし、この状態でアルミ製又は銅製の鍋に置き換えると、インバータ回路の出力電流が急激に増加するが、この電流の増加に比べてアルミ製又は銅製の鍋では表面抵抗値が小さいために渦電流損失が小さくなり充分加熱できない。そして、インバータ回路を形成する各スイッチング素子の熱損失のみ大きくなる。
しかし、本発明では電力設定値の減少に応じて電流制限設定値を小さくするので、規格外のアルミ製又は銅製の鍋を加熱したとき熱損失が小さな電流制限設定値によって制限されるので、各スイッチング素子の熱損失が抑制でき熱損失による部品の劣化が防止できる。
In the first invention, the current limit set value changes according to the power set value. At this time, for example, when the power setting value is set from the maximum to the middle, the current limit setting value decreases as the power setting value decreases. Stainless steel pans can be heated sufficiently even if the power setting is set to the middle. However, if it is replaced with an aluminum or copper pan in this state, the output current of the inverter circuit will increase rapidly. Loss is small and heating is not possible. And only the heat loss of each switching element which forms an inverter circuit becomes large.
However, in the present invention, since the current limit set value is reduced in accordance with the decrease in the power set value, the heat loss is limited by the small current limit set value when the non-standard aluminum or copper pan is heated. The heat loss of the switching element can be suppressed, and the deterioration of the parts due to the heat loss can be prevented.
上述の効果に加えて、本発明では、過電流設定値と電流制限設定値との差は、電力設定値が小さくなると大きくなる。
例えば、電力設定値を最大から中間にすると、過電流設定値と電流制限設定値との差が大きくなり、この状態でステンレス製の鍋からアルミ製又は銅製の鍋に置き換えると、インバータ回路の出力電流が急激に増加するが、電流制限設定値が小さく設定されるのでインバータ回路の出力電流も小さく制限される。このとき、出力制御の応答性の遅れにより出力電流の出力制限時にオーバシュートが発生する。しかし、過電流設定値と電流制限設定値との差が大きいために出力電流は過電流設定値に達する前に電流制限設定値で制限される。よって、ステンレス製の鍋からアルミ製又は銅製の鍋に置き換えたとき、過電流保護の動作によってインバータ回路の動作を停止することがなくなり、調理者が規格外の鍋を交換したときに感じる加熱が切れるという違和感を取り除くことができる。
In addition to the effects described above, in the present invention, the difference between the overcurrent set value and the current limit set value increases as the power set value decreases.
For example, if the power setting value is changed from the maximum to the middle, the difference between the overcurrent setting value and the current limit setting value becomes large. If the stainless steel pot is replaced with an aluminum or copper pot in this state, the output of the inverter circuit Although the current increases rapidly, the output current of the inverter circuit is also limited to a small value because the current limit set value is set small. At this time, an overshoot occurs when the output current is limited due to a delay in the response of the output control. However, since the difference between the overcurrent set value and the current limit set value is large, the output current is limited by the current limit set value before reaching the overcurrent set value. Therefore, when the stainless steel pan is replaced with an aluminum or copper pan, the operation of the inverter circuit is not stopped by the overcurrent protection operation, and the heating felt when the cooker replaces the nonstandard pan You can remove the sense of incongruity of being cut.
第2の発明及び第3の発明は、電流制限設定値が電力設定値に応じて精度良く変化するので、ステンレス製の鍋から規格外のアルミ製又は銅製の鍋に置き換えたとき過電流保護の保護協調がさらに向上する。 In the second and third inventions, the current limit set value changes with high accuracy according to the power set value. Therefore, when the stainless steel pan is replaced with a non-standard aluminum or copper pan, Protection coordination is further improved.
本発明の実施形態1について、図1〜図5を参照して説明する。図1は、本発明の電磁誘導加熱装置の電気接続図である。また、図2は図1に示す電流制限設定回路の詳細接続図である。図1において、図7に示す従来技術の電気接続図と同一符号は、同一動作を行うので相違する点についてのみ説明を行う。
図2は電流制限設定回路IC2の詳細図で、オペアンプで構成された加算回路とリミッタ回路とで形成され、加算回路は、電力設定回路WAからの電力設定信号Waと所定の基準信号Vaとを加算し、反転増幅して負の信号を出力する。リミッタ回路は、負の信号を正の信号に反転し、予め定めた電力設定基準値(ツェナ・ダイオードの基準電圧)未満のとき、電力設定信号Waの値に応じて電流制限設定値Ic2を変化させ、電力設定基準値を越えると過電流設定値Ioより小さい予め定めた電流制限設定値Ic2を出力する。このとき、電力設定信号Waの値が零でも電流制限設定値Ic2の値は、加算回路により所定の値を出力する。 FIG. 2 is a detailed diagram of the current limit setting circuit IC2, which is formed by an adder circuit and a limiter circuit composed of operational amplifiers. The adder circuit generates a power setting signal Wa from the power setting circuit WA and a predetermined reference signal Va. Add, invert and amplify to output a negative signal. The limiter circuit inverts the negative signal to a positive signal, and changes the current limit setting value Ic2 according to the value of the power setting signal Wa when it is less than a predetermined power setting reference value (the Zener diode reference voltage). When the power setting reference value is exceeded, a predetermined current limit setting value Ic2 smaller than the overcurrent setting value Io is output. At this time, even if the value of the power setting signal Wa is zero, the value of the current limit setting value Ic2 is output as a predetermined value by the adding circuit.
図1に示すように、V/FコンバータVFの入力端は抵抗器R1を介して接地されている。よって、電力制御用差動増幅回路DA1の出力信号Da1及び電流制御用差動増幅回路DA2の出力信号Da2は正の値とならない限りV/FコンバータVFの入力端の電圧は零電位に保たれ、V/FコンバータVFはその入力電位が零のときインバータを最低周波数で制御するための周波数信号を出力する。ここで、インバータ回路の最低周波数は、載置される調理鍋を含む加熱コイルLと共振コンデンサC2,C3とからなる直列共振回路の共振周波数より若干高い値に設定される。 As shown in FIG. 1, the input end of the V / F converter VF is grounded via a resistor R1. Therefore, the voltage at the input terminal of the V / F converter VF is kept at zero potential unless the output signal Da1 of the power control differential amplifier DA1 and the output signal Da2 of the current control differential amplifier DA2 become positive values. The V / F converter VF outputs a frequency signal for controlling the inverter at the lowest frequency when its input potential is zero. Here, the minimum frequency of the inverter circuit is set to a value slightly higher than the resonance frequency of the series resonance circuit including the heating coil L including the cooking pot to be placed and the resonance capacitors C2 and C3.
図3は、本発明の実施形態1の電磁誘導加熱調理器にアルミ製又は銅製の鍋を使用し、電力設定値Waの増加に応じて電流制限設定値Ic2の値を増加させたときのタイミング図である。同図において、同図(A)は、出力電流検出信号Ct2を示し、同図(B)は、電力設定信号Waを示し、同図(C)は、電力演算信号Poを示し、同図(D)は、電流制御用差動増幅信号Da2を示し、同図(E)は、電力制御用差動増幅信号Da1を示し、同図(F)は、V/FコンバータVFの入力信号Viを示し、同図(G)は、電流制限設定値Ic2を示す。以後、同図を用いて動作を説明する。 FIG. 3 shows a timing when an aluminum or copper pan is used for the electromagnetic induction heating cooker according to the first embodiment of the present invention, and the value of the current limit set value Ic2 is increased in accordance with the increase of the power set value Wa. FIG. In the same figure, (A) shows the output current detection signal Ct2, (B) shows the power setting signal Wa, (C) shows the power calculation signal Po, D) shows the differential amplification signal Da2 for current control, (E) shows the differential amplification signal Da1 for power control, and (F) shows the input signal Vi of the V / F converter VF. FIG. 5G shows the current limit set value Ic2. Hereinafter, the operation will be described with reference to FIG.
アルミ製又は銅製の鍋を誘導加熱コイル上に載置し、図3に示す時刻t=t0において、図1に示す電力設定回路WAにより、図5に示す電力設定信号Waの値をa点から増加させると、電力設定信号Waの値の増加に応じて、図3(C)に示す電力演算信号Poの値が増大していくが、それ以上に図3(A)に示す出力電流検出信号Ct2の値の増加が著しい。 An aluminum or copper pan is placed on the induction heating coil, and at time t = t0 shown in FIG. 3, the power setting circuit WA shown in FIG. When the value is increased, the value of the power calculation signal Po shown in FIG. 3C increases as the value of the power setting signal Wa increases. However, the output current detection signal shown in FIG. The increase in the value of Ct2 is remarkable.
また、時刻t=t0において、電力設定信号Waの値が増加すると、図3(E)に示す電力制御用差動増幅信号Da1の値は減少し、逆に、同図(D)に示す電流制御用差動増幅信号Da2の値は増加する。同図(F)に示すV/FコンバータVFの入力信号Viは、ダイオードDR2、DR3及びV/FコンバータVFの入力端の抵抗器R1によって、電力制御用差動増幅信号Da1又は電流制御用差動増幅信号Da2の正の電圧のどちらか大きい信号が入力信号Viとなる。V/FコンバータVFは、同図(F)に示す入力電圧Viの減少に応じて、インバータの出力周波数を減少させて誘導加熱コイルに流れる電流を増加させる。 Further, when the value of the power setting signal Wa increases at time t = t0, the value of the power control differential amplification signal Da1 shown in FIG. 3E decreases, and conversely, the current shown in FIG. The value of the control differential amplification signal Da2 increases. The input signal Vi of the V / F converter VF shown in FIG. 5F is supplied to the power control differential amplification signal Da1 or the current control difference by the diodes DR2 and DR3 and the resistor R1 at the input end of the V / F converter VF. The signal that is larger of the positive voltage of the dynamic amplification signal Da2 becomes the input signal Vi. The V / F converter VF decreases the output frequency of the inverter and increases the current flowing through the induction heating coil in accordance with the decrease of the input voltage Vi shown in FIG.
時刻t=t1において、図5に示す電力設定信号Waの値がa点からb点に増加すると、出力電流検出信号Ct2の値が電流制限設定信号Ic2の値より大きくなり図3(D)に示す電流制御用差動増幅信号Da2は正の電位となって出力する。このとき、図3(E)に示す電力制御用差動増幅信号Da1の値より大きくなり、ダイオードDR2及びダイオードDR3により、電流制御用差動増幅信号Da2が選択されV/FコンバータVFに入力する。 When the value of the power setting signal Wa shown in FIG. 5 increases from the point a to the point b at time t = t1, the value of the output current detection signal Ct2 becomes larger than the value of the current limit setting signal Ic2, and FIG. The current control differential amplification signal Da2 shown is output as a positive potential. At this time, the value is larger than the value of the power control differential amplification signal Da1 shown in FIG. 3E, and the current control differential amplification signal Da2 is selected by the diode DR2 and the diode DR3 and input to the V / F converter VF. .
時刻t=t2以後は、インバータ回路の出力周波数は電流制御用差動増幅信号Da2に応じて制御され、出力電流検出信号Ct2の値は、図5に示すb点の電流制限設定値で制限される。 After time t = t2, the output frequency of the inverter circuit is controlled in accordance with the current control differential amplification signal Da2, and the value of the output current detection signal Ct2 is limited by the current limit setting value at point b shown in FIG. The
上述より、ステンレス製の鍋を規格外のアルミ製又は銅製の鍋に置き換えたとき、誘導加熱コイルに流れる電流が急激に増加するが、電流制限設定値がステンレス製の鍋に対応した値に設定されているので、インバータ回路の出力電流が電流制限設定値によって制限される。これにより、規格外の鍋を使用してもインバータ回路を形成する各スイッチング素子の熱損失が抑制でき、部品の劣化が防止できる。また、電力設定値が小さいほど電流制限設定値が小さくなるので各スイッチング素子の熱損失の抑制がより大きくなる。 From the above, when the stainless steel pan is replaced with a non-standard aluminum or copper pan, the current flowing through the induction heating coil increases rapidly, but the current limit setting value is set to a value corresponding to the stainless steel pan. Therefore, the output current of the inverter circuit is limited by the current limit setting value. Thereby, even if it uses a nonstandard pan, the heat loss of each switching element which forms an inverter circuit can be controlled, and degradation of parts can be prevented. Moreover, since the current limit set value is smaller as the power set value is smaller, the suppression of heat loss of each switching element is further increased.
図4は、電磁誘導加熱調理器で加熱中にステンレス製の鍋からアルミ製又は銅製の鍋に置き換えたときのタイミング図である。同図において、同図(A)は、出力電流検出信号Ct2を示し、同図(B)は、電力演算信号Poを示し、同図(C)は、電流制御用差動増幅信号Da2を示し、同図(D)は、電力制御用差動増幅信号Da1を示し、同図(E)は、V/FコンバータVFの入力信号Viを示す。以後、同図を用いて動作について説明する。 FIG. 4 is a timing diagram when the stainless steel pan is replaced with an aluminum or copper pan during heating by the electromagnetic induction heating cooker. In the same figure, (A) shows the output current detection signal Ct2, (B) shows the power calculation signal Po, and (C) shows the current control differential amplification signal Da2. FIG. 4D shows the power control differential amplification signal Da1, and FIG. 4E shows the input signal Vi of the V / F converter VF. Hereinafter, the operation will be described with reference to FIG.
図5に示す電力設定信号Waの値をb点に設定し、この状態でステンレス製鍋をアルミ製又は銅製の鍋に置き換えたとき、図4に示す時刻t=t3において、急激な負荷変動が生じ出力電流検出信号Ct2の値が増加する。 When the value of the power setting signal Wa shown in FIG. 5 is set to point b and the stainless steel pan is replaced with an aluminum or copper pan in this state, a sudden load fluctuation occurs at time t = t3 shown in FIG. As a result, the value of the output current detection signal Ct2 increases.
電流制御用差動増幅回路DA2に応答遅れが存在するために、図4(A)に示すt=t4において、出力電流に制限が係るときに出力電流検出信号Ct2は過度的にオーバシュートが発生し電流制限設定信号Ic2を越える。このとき、電力設定信号Waの値が図5に示すb点の位置に設定され、過電流設定信号Ioの値と電流制限設定信号Ic2の値との差は大きい。 Since there is a response delay in the current control differential amplifier circuit DA2, the output current detection signal Ct2 excessively overshoots when the output current is limited at t = t4 shown in FIG. Exceeds the current limit setting signal Ic2. At this time, the value of the power setting signal Wa is set at the position of point b shown in FIG. 5, and the difference between the value of the overcurrent setting signal Io and the value of the current limit setting signal Ic2 is large.
図4に示す時刻t=t4において、電流制御用差動増幅信号Da2が電力制御用差動増幅回路Da1より大きくなり、インバータ回路の制御は、電力制御用差動増幅回路Da1から電流制御用差動増幅信号Da2に切り換わる。このとき、V/FコンバータVFの図4(E)に示す入力信号Viの電位は上昇し、インバータの出力周波数を高くして誘導加熱コイルに供給する電流を抑制し、出力電流を電流制限設定信号Ic2の値と略同一にすので、出力電流検出信号Ct2の値は過電流設定信号Ioまで達しない。 At time t = t4 shown in FIG. 4, the current control differential amplification signal Da2 becomes larger than the power control differential amplification circuit Da1, and the control of the inverter circuit is controlled from the power control differential amplification circuit Da1. Switching to the dynamic amplification signal Da2. At this time, the potential of the input signal Vi shown in FIG. 4E of the V / F converter VF rises, the output frequency of the inverter is increased to suppress the current supplied to the induction heating coil, and the output current is set to be current limited. Since the value is substantially the same as the value of the signal Ic2, the value of the output current detection signal Ct2 does not reach the overcurrent setting signal Io.
時刻t=t4〜t5において、出力電流検出信号Ct2の値は過電流設定信号Ioの値に達しないので、ステンレス製の鍋からアルミ製又は銅製の鍋に置き換えても過電流保護が動作しインバータ回路を停止することがなくなり、調理者が鍋を交換したときに感じる加熱が切れるという違和感を取り除くことができる。 At time t = t4 to t5, the value of the output current detection signal Ct2 does not reach the value of the overcurrent setting signal Io. Therefore, even if the stainless steel pot is replaced with an aluminum or copper pot, the overcurrent protection operates and the inverter The circuit is not stopped, and it is possible to remove the uncomfortable feeling that the heating that the cook feels when the pan is changed is cut off.
上述より、過電流設定値Ioと電流制限設定値Ic2との差は、図5に示すように、例えば、電力設定値Waがc点とb点とを比較すると電力設定値が小さいほど差が大きくなる。例えば、電力設定値を図5に示すb点に設定し、この状態で鍋を置き換えると、過電流設定値Ioと電流制限設定値Ic2との差が大きく、この状態でステンレス製の鍋からアルミ製又は銅製の鍋に置き換えると、誘導加熱コイルに流れる電流が急激に増加するが、電流制限設定値が小さく設定されているので、出力電流が制限されるときに発生するオーバシュートの最大値するが過電流設定値に達しない。よって、電力設定値が小さくなるほど過電流保護の保護協調が向上する。 From the above, the difference between the overcurrent set value Io and the current limit set value Ic2 is, for example, as shown in FIG. 5, when the power set value Wa is compared between the c point and the b point, the difference decreases as the power set value decreases. growing. For example, if the power setting value is set to point b shown in FIG. 5 and the pan is replaced in this state, the difference between the overcurrent setting value Io and the current limit setting value Ic2 is large. If it is replaced with a steel or copper pan, the current flowing in the induction heating coil increases rapidly, but the current limit setting value is set small, so the maximum overshoot that occurs when the output current is limited The overcurrent set value is not reached. Therefore, the protection coordination of overcurrent protection is improved as the power setting value is decreased.
[実施形態2]
図6は、実施形態2の電力設定値と出力電流との関係図である。
実施形態1では、図5に示すように電力設定値Waの増加に応じて電流制限設定値Ic2を直線的に増加させているが、電力設定値Waの増加に応じて電流制限設定値Ic2を図6に示すように放物線又は台形的に増加させ、電力設定値Waがc点(例えば、予め定めた電力設定基準値)を越えると図6に示す電流制限設定値Ic2の所定値に維持するようにしてもよい。
[Embodiment 2]
FIG. 6 is a relationship diagram between the power setting value and the output current in the second embodiment.
In the first embodiment, as shown in FIG. 5, the current limit set value Ic2 is linearly increased in accordance with the increase in the power set value Wa, but the current limit set value Ic2 is increased in accordance with the increase in the power set value Wa. As shown in FIG. 6, when the power setting value Wa exceeds a point c (for example, a predetermined power setting reference value), it is maintained at a predetermined value of the current limit setting value Ic2 shown in FIG. You may do it.
図6に示すように電流制限設定値Ic2を電力設定値Waの増加に応じて放物線又は台形的に増加させることで、直線的に増加させるより精度のよい電流制限設定値Ic2が設定でき、規格外のアルミ製又は銅製の鍋を使用したとき過電流保護の保護協調がさらに向上する。 As shown in FIG. 6, by increasing the current limit set value Ic2 in a parabolic or trapezoidal manner according to the increase in the power set value Wa, a more accurate current limit set value Ic2 that can be increased linearly can be set. The protection coordination of the overcurrent protection is further improved when using an outer aluminum or copper pan.
CP 過電流検出回路
C1 平滑コンデンサ
C2 共振コンデンサ
C3 共振コンデンサ
CT1 入力電流検出器
CT2 出力電流検出器
DC 駆動回路
DA1 電力制御用差動増幅回路
DA2 電流制御用差動増幅回路
DR1 整流回路
DR2 ダイオード
DR3 ダイオード
IC2 電流制限設定回路
IO 過電流設定回路
L 誘導加熱コイル
PO 電力演算回路
PT1 電圧検出器
R1 抵抗器
R2 抵抗器
R3 抵抗器
R4 抵抗器
R5 抵抗器
SC 運転指令回路
SW 起動スイッチ
TR1 スイッチング素子
TR2 スイッチング素子
VF V/Fコンバータ
WA 電力設定回路
Cp 過電流検出信号
Ct1 入力電流検出信号
Ct2 出力電流検出信号
Da1 電力制御用差動増幅信号
Da2 電流制御用差動増幅信号
Ic2 電流制限設定信号
Io 過電流設定信号
Po 電力演算信号
Pt1 電圧検出信号
Sc 運転指令信号
Sw 起動信号
Vf V/Fコンバータ信号
Wa 電力設定信号
CP overcurrent detection circuit C1 smoothing capacitor C2 resonance capacitor C3 resonance capacitor CT1 input current detector CT2 output current detector DC drive circuit DA1 power control differential amplifier DA2 current control differential amplifier DR1 rectifier circuit DR2 diode DR3 diode IC2 Current limit setting circuit IO Overcurrent setting circuit L Induction heating coil PO Power calculation circuit PT1 Voltage detector R1 Resistor R2 Resistor R3 Resistor R4 Resistor R5 Resistor SC Operation command circuit SW Start switch TR1 Switching element TR2 Switching element VF V / F converter WA Power setting circuit Cp Overcurrent detection signal Ct1 Input current detection signal Ct2 Output current detection signal Da1 Power control differential amplification signal Da2 Current control differential amplification signal Ic2 Current limit setting signal Io Current setting signal Po power calculating signal Pt1 voltage detection signal Sc operation command signal Sw activation signal Vf V / F converter signal Wa power setting signal
Claims (3)
前記電流制限設定回路は、前記電力設定値に応じて前記電流制限設定値が変化すると共に前記電流制限設定値の最大値が前記過電流設定値未満であること、を特徴とする電磁誘導加熱調理器である。 Calculation of input power based on a resonance capacitor, an induction heating coil that forms a series resonance circuit with the resonance capacitor, an inverter circuit that supplies a high-frequency current to the induction heating coil, and an input current and an input voltage of the inverter circuit A power calculation circuit that detects an output current value of the inverter circuit and stops the inverter circuit when a predetermined overcurrent set value is exceeded, the power calculation value and a predetermined power set value, Differential amplification circuit for power control that outputs a differential amplification value for power control, a current limit setting circuit that outputs a predetermined current limit setting value, and the output current value and a predetermined current A differential amplification circuit for current control that differentially amplifies the limit set value and outputs a differential amplification value for current control, and the differential amplification value for power control and the differential increase for current control In the electromagnetic induction heating cooker, comprising: a current limit control circuit configured to enter a value larger values of the frequency converting circuit for controlling said inverter circuit, and
The current limit setting circuit is characterized in that the current limit set value changes in accordance with the power set value and the maximum value of the current limit set value is less than the overcurrent set value. It is a vessel.
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