JP2894145B2 - Induction heating cooker - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an induction cooking device.

[0002]

2. Description of the Related Art In recent years, an induction heating cooker for inducing an eddy current in the bottom of a load pan by using a high-frequency magnetic field to heat has attracted attention as a clean, safe and highly heat-efficient cooking means. , High output has been achieved.

Hereinafter, a conventional induction heating cooker will be described with reference to FIG. As shown in the figure, a power cord 2 having one end connected to a power plug 1 connected to a commercial power source.
Reference numerals a and 2b house electrical components and are connected to input terminals B and B 'inside the housing 3 made of a conductive material. The power plug 1 has a ground terminal for preventing electric shock, and is connected to a ground coil 14 via a ground wire 2c. The other end of the ground coil 14 is connected to a conductive portion of the housing 3. The capacitor 5 and the input terminal of the common mode choke coil 6 are connected between the input terminals B and B '. Between the output terminals of the common mode choke coil 6, the capacitor 8 and the input terminal of the full-wave rectifier 9 and the capacitor 7a and the capacitor are connected. 7b are connected to each other. The capacitor 7
The connection point of the series circuit of the capacitor a and the capacitor 7b is connected to the housing 3. A capacitor 10 is connected between the output terminals of the full-wave rectifier 9, and a choke coil 11 is connected in series to the positive electrode. A load-side terminal of the choke coil 11 is connected to an input terminal A of an inverter 4 which is a kind of frequency converter, and a negative output terminal of the full-wave rectifier 9 is connected to the inverter 4.
Is connected to the input terminal A ′. The inverter 4 includes a heating coil 12 and a high-frequency circuit section 13 for supplying a high-frequency current to the heating coil 12.

[0004] The operation of the induction heating cooker configured as described above will be described below. The high-frequency circuit unit 13 includes a resonance capacitor that resonates with the heating coil 12, a high-frequency power supply capacitor that bypasses a resonance current, and a semiconductor switching element. The resonance circuit of the heating coil 12 and the resonance capacitor is excited by switching of the semiconductor switching element. Thus, a high-frequency large current is generated in the heating coil 12. Not only the heating coil 12 but also the high-frequency circuit section 13 generates a high-frequency radiated electromagnetic field around it. The high-frequency circuit section 13 includes a semiconductor switching element and generates a cutoff current having a sharper current change rate in addition to the current supplied to the heating coil 12, so that a radiated electromagnetic field including a higher frequency component is generated.

The high-frequency voltage that could not be filtered by the high-frequency power supply capacitor inside the high-frequency circuit 13 is applied to the high-frequency circuit 1
3 is superimposed on the low-frequency pulsating DC voltage between the input terminals A and A ′. The superimposed high-frequency noise is so-called normal mode noise, and includes the choke coil 11 and the capacitor 1.
0, the capacitor 8 and the capacitor 5 prevent the leakage from the input terminals B and B 'to the commercial power supply.

[0006] Further, since the electric components constituting the inverter 4 and the connection lines thereof are close to the housing 3 and the power supply line through which the low-frequency current flows, the above-mentioned high-frequency radiated electromagnetic field is also supplied by the power supply through which the low-frequency current flows. High-frequency noise is induced between the lines or between the power supply line and the housing 3. Among the high-frequency noise induced between the power lines of the low-frequency part and the high-frequency noise induced between the power line of the low-frequency part and the housing 3, those having different phases in each power line become normal mode noise. Filtered.

In the high-frequency noise voltage induced by the high-frequency radiated electromagnetic field between the power supply line in the internal low-frequency part and the housing 3, those having the same phase in each power supply line are so-called common mode noises. , Choke coil 11, common mode choke coil 6, capacitor 7a, capacitor 7
(b) Leakage conduction noise, which is filtered by the ground coil 14 and enters the commercial power supply, is suppressed to a low level.

[0008]

However, the above configuration has a problem that even when the capacitors 7a and 7b are connected, the common mode noise level is not reduced or increased in a range higher than a specific frequency. Also, when the earth coil 14 is connected, resonance occurs between the inductance component and the capacitance of the capacitors 7a and 7b, and there is a problem that common mode noise increases near a specific frequency. The earth coil 14 is usually made of heavy ferrite or the like. The core of the material is necessary and becomes heavy, and even if a large current flows in the winding at the time of earth leakage, the winding diameter needs to be large to prevent disconnection and abnormal heat generation, and the overall shape of the coil becomes large. , When mounting on a device, it is necessary to secure a large space inside the device, and it takes time to mount There was a problem.

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems. In an induction heating cooker having a structure in which a conductive portion of a main body housing or an internal part is grounded to earth to prevent an electric shock, a common terminal covering a wide range from low frequency to high frequency is provided. The purpose is to suppress modal noise components with small components that are easy to mount on equipment.

[0010]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a frequency conversion device for inputting power from a DC power supply or a low-frequency power supply and generating a high-frequency current in a heating coil for inductively heating a load. And a housing for housing a part or all of the components constituting the frequency conversion device,
A grounding means for grounding a conductive part of the housing or a component attached to or provided in the housing to ground,
Between the DC power supply potential portion or the low frequency power supply potential portion to be input to the frequency converter and the conductive portion of the housing grounded to ground by the grounding means, or the DC power supply potential portion or the low frequency power supply potential portion And between the conductive part of the component grounded to the earth by the grounding means and attached to or disposed on the housing, has a series resistance component of several tens of ohms or more and about tens of kiloohms or less, and up to near a predetermined frequency. Is configured to connect an impedance whose absolute value decreases substantially in proportion to the frequency.

[0011]

According to the above construction, between the DC power supply potential portion or the low frequency power supply potential portion input to the frequency converter and the conductive portion of the housing grounded to the ground by the grounding means, or the DC power supply potential portion or the low power supply potential portion. Since the impedance is connected between the frequency power supply potential portion and a conductive portion of a component which is grounded to the ground by the grounding means and is attached to or disposed on the housing, the input power supply potential portion is grounded to the housing. High frequency common mode noise generated between the input power supply potential portion and the conductive portion of the component grounded and attached to or provided to the housing is bypassed by the above impedance. In addition, the leakage of the common mode noise to the power supply side outside the housing can be suppressed.

On the other hand, high-frequency noise of about 500 kHz or more is bypassed from the input power supply potential portion on which common mode noise is superimposed, to the conductive portion of the housing or the component, which is grounded, through the impedance. When the amount of the component increases, this high-frequency noise component is radiated from the conductive part of the housing or components to the surrounding space, and a feed line outside the housing for supplying DC power or low-frequency power supplies reduces the radiated noise. Received, the noise reaches the DC power supply or low-frequency power supply, which is an external power supply, passes through the ground wire from the grounding part of the power supply, and returns from the grounding means of the induction heating cooker to the conductive part of the housing or the conductive part of the part. High-frequency noise component generated by the frequency converter of the induction heating cooker leaks to the external power supply, causing damage to other electronic devices connected to the same power supply. There is a Les.

However, as described above, the absolute value of the bypass impedance decreases substantially in proportion to the frequency, that is, decreases as the frequency increases.
Since the magnitude of the absolute value of the impedance does not depend on the frequency, it has a series resistance component of about 10 ohms or more and about 10 kohms or less, so at frequencies near the predetermined frequency and above, the absolute value is equal to the resistance value. When the impedance for bypass includes a small inductance component, the impedance becomes larger, and the component of common mode noise near a predetermined frequency or higher is applied to the conductive part or component of the grounded housing via the impedance. Excessive bypass by the conductive portion of the housing is suppressed, and the conductive portion of the housing or the conductive portion of the component attached to or provided to the housing radiates to the surroundings and is directed to the external DC power supply or the low frequency power supply side. High frequency noise that leaks can be suppressed.

On the other hand, at low frequencies below the predetermined frequency, the bypass impedance has a capacitive characteristic whose impedance decreases in proportion to the frequency. It is possible to have a large absolute value impedance,
The current of the external low-frequency power supply frequency component flows into the bypass impedance or the housing, and the direct current resistance component of the bypass impedance generates heat. Increases the amount of common mode noise that bypasses the conductive part of the housing or component grounded through the amplifier in proportion to the frequency, and attenuates the common mode noise leaking to the external power supply in proportion to the frequency up to a predetermined frequency. The amount can be reduced by increasing it.

Further, since the impedance has a substantially constant resistance characteristic in a high frequency band near a predetermined frequency or higher, a very small inductance in a leakage path of common mode noise from the frequency converter to the external power supply. The resonance characteristic of the component and the capacitive impedance component can be relaxed to suppress an increase in leakage noise near a specific resonance frequency.

[0016]

【Example】

(Embodiment 1) An embodiment of the present invention will be described below with reference to the drawings.

In FIG. 1, a commercial power supply 15 of 200 [V] having a frequency of 50 [Hz] or 60 [Hz] includes:
The power supply lines 16a and 16b are connected. Further, a ground wire 16c is connected to the ground. To the terminals of the power plug 17, power cords 18a, 18b integrally formed of resin and a ground wire 18c are connected.
The other terminal of the ground wire 18 c is connected to the conductive portion of the housing 32 by the housing 3.
The power cords 18a, 18
b are connected to other terminals. 0.56 capacity
[ΜF] filter capacitor 19 is connected to input terminals C and C ′.
The input terminal of the common mode choke coil 20 is connected to the load side. 0.56 [μ] between the output terminals of the common mode choke coil 20.
F] of the filter capacitor 25 and the full-wave rectifier 26
AC input terminals are connected.

A series circuit of a filter capacitor 21 and a resistor 22 and a series circuit of a filter capacitor 23 and a resistor 24 are provided between both output terminals of the common mode choke coil 20 and the conductive portion of the housing 32 connected to the ground. It is connected. The capacitances of the filter capacitor 21 and the filter capacitor 23 are both 2200 [pF], and the resistors 22 and 24 both have a resistance value of 200 [ohm].

A choke coil 28 of about 300 μH is connected to the positive terminal of the output of the full-wave rectifier 26, and a 2.2 μF capacitor 27 is connected between the output terminals of the full-wave rectifier 26. ing. An inverter 30 is connected between the load terminal of the choke coil 28 and the negative terminal of the full-wave rectifier 26.
Are connected to the input terminals D and D ′. Inverter 30
Is composed of a heating coil 29 and a high-frequency circuit section 31. The high-frequency circuit section 31 includes a resonance capacitor 31c that forms a resonance circuit with the heating coil 29, reverse conducting transistors 31a and 31b that excite the resonance circuit by switching, a switching current or a resonance current. And a control circuit 31e for controlling on / off of the transistors 31a and 31b.

The operation of the induction heating cooker configured as described above will be described. When this induction heating cooker is operated, the transistors 31a,
31b are alternately turned on and off alternately, and the heating coil 2
9 and the resonance capacitor 31c, the heating coil 2
9 generates a high-frequency current of about 20 [kHz]. The high-frequency current generated in the heating coil 29 has a large current value, but does not flow a steep current having a substantially continuous waveform. On the other hand, the transistors 31a and 31b of the high-frequency circuit unit 31 and the high-frequency power supply capacitor 31d are connected to the transistors 31a and 31b, respectively.
A large current having a sharp current change accompanying the on / off of the device flows.

As described above, a large current or a high voltage including a wide frequency spectrum is applied to the inverter 30, and these currents or voltages generate an electromagnetic field having a spectrum distributed over a wide frequency range. This electromagnetic field generates a noise current and a noise voltage on the connection line connecting the electric components inside the housing 32. Among the noise current and noise voltage, the normal mode noise superimposed between the commercial power supply line to which the current and the voltage are applied or between the output terminals of the rectifier 26 is included in the choke coil 28, the filter capacitor 27, the filter capacitor 25, and the filter. It can be suppressed by the capacitor 19.

On the other hand, the voltage induced between the ground wire or the housing 32 connected to the ground and the electric parts of the inverter 31 or the connection line connecting them is generated between the commercial power supply line and the output terminal of the rectifier 26. The common mode noise, which changes in phase with respect to the ground, is caused by the common mode choke coil 20 and the filter capacitor 21 connected between the load side terminal of the common mode choke coil 20 and the conductive part of the housing 32 grounded. This can be suppressed by a series circuit of the resistor 22 and a series circuit of the filter capacitor 23 and the resistor 24.

For comparison, when the resistors 22 and 24 of FIG. 1 are not used, that is, when they are short-circuited and connected while leaving the filter capacitors 21 and 23, according to experiments, the filter capacitors 21 and 23 are not used ( About 100 [kHz] to about 500
In the frequency band of [kHz], the effect of suppressing the amount of common mode noise leakage to the commercial power supply increases in proportion to the frequency, but in the frequency band of about 500 [kHz] or more,
Conversely, as the frequency increases, the effect of suppressing the amount of leakage tends to decrease, and in the frequency band of a specific high-frequency width, the effect of suppressing the effect further decreases locally. In some cases, it was higher.

On the other hand, the resistors 22 and 24 are replaced by the filter capacitor 21 and the filter capacitor 2 as in the embodiment of FIG.
3 are connected in series with each other, the common mode of the capacitors 21 and 23 in the frequency range of 100 [kHz] to about 500 [kHz] is compared to connecting the filter capacitor 21 and the filter capacitor 23 alone. Although the noise filtering effect is slightly reduced, it is about 500 [kHz].
At the above frequencies, a great reduction effect was obtained.

The action of the series impedance of the filter capacitor 21 and the resistor 22 and the series impedance of the filter capacitor 23 and the resistor 24 will be described below. About 5
When the frequency becomes higher than 00 [kHz], the radiation energy to the space increases, so that the radiation efficiency of the electromagnetic wave of the antenna fed from the noise source increases, and the reception efficiency of the antenna receiving the electromagnetic wave propagating in the space also increases. Become. Therefore, when such high-frequency noise is supplied to a large-area object such as the conductive casing 32, the noise becomes a transmitting antenna and is easily radiated to the surroundings.
If there is a long conductor such as 8a and the power supply line 18b, it becomes a receiving antenna, and it becomes easy to receive the induction of noise radiated into the space from the housing 32 or the like.

The absolute value | Z | of the combined impedance of the series circuit of the capacitor and the resistor is expressed by the following equation (1), where C is the capacitance of the capacitor, R is the pure resistance of the resistor, and f is the frequency.

[0027]

(Equation 1)

The frequency characteristic of | Z | in the above equation is shown in FIG. The broken line a in FIG. 2 is a frequency characteristic of the absolute value of the impedance of the resistor alone, and the broken line b in FIG. 2 is a frequency characteristic of the absolute value of the impedance of the capacitor alone. As shown in FIG. 2, the combined impedance | Z |
At frequencies below 0 = 1 / (2 * π * R * C), the capacitance C is almost dominant and becomes smaller in proportion to the frequency. At frequencies above f0 and above, the resistance R is almost constant. Become. In this embodiment, R = 200 [ohm],
Since C = 2200 [pF], f0 = about 362 [kHz]
z], and the absolute value of the impedance of the series circuit of the filter capacitor 21 and the resistor 22 or the series circuit of the filter capacitor 23 and the resistor 24 is about 400
In the case of [kHz] or less, it is substantially equivalent to the case where a capacitor of 2200 [pF] is connected alone, and is approximately 400 [kHz].
At the above frequency, it is substantially equivalent to a resistance of 200 [ohm] connected alone.

In the above embodiment, the series circuit of the filter capacitor 21 and the resistor 22 and the filter capacitor 23
Is connected between the commercial power supply potential on the load side of the common mode choke coil 20 and the housing 32, so that common mode noise in a frequency region of about 400 [kHz] or less is generated by the common mode choke. Blocked by the inductance of the coil 20, the filter capacitor 21
The housing 32 includes a series circuit of a filter capacitor 21 and a resistor 22 substantially equivalent to the magnitude of a single impedance and a series circuit of a filter capacitor 23 and a resistor 24 substantially equivalent to the magnitude of a single impedance of the filter capacitor 23.
The common mode noise leaking to the commercial power supply can be filtered by increasing the suppression amount in proportion to the frequency.

Further, the frequency component of the common mode noise of the commercial power supply potential of 400 kHz or more is also blocked by the inductance of the common mode choke coil 20, and the filter capacitor 21 and the resistor 22 are substantially equal in impedance to the resistor 22. Is bypassed to the case 32 via the filter capacitor 23 and the impedance of the resistor 24 which are substantially equal to the impedance of the resistor 24, but the impedance of the capacitor is reduced in proportion to the frequency. Unlike the bypass, the bypass is performed with an impedance having a substantially constant magnitude independent of the frequency. Therefore, the excessive supply of the high frequency component of the common mode noise to the housing 32 is suppressed.

By suppressing the excessive supply of the component of about 400 [kHz] or more of the common mode noise to the housing 32, about 500 [kHz] having a large radiant energy is suppressed.
The above common mode noise component Vn radiates to the surrounding space using the housing 32 as an antenna, and the nearby power supply lines 18a,
18b is a receiving antenna, which can prevent the common mode choke coil 20 from jumping over the common mode choke coil 20 and leaking to the commercial power supply 15 along the path shown by the broken line in FIG. In addition,
The capacitor 33, the resistor 34, the capacitor 35, and the resistor 36 shown in FIG. 1 are used to evaluate the amount of conducted noise leaking to the outside of the device. Generally, the voltage Va and the voltage Vb are measured to evaluate the magnitude. is there.

When filter capacitors 21 and 23 having a small capacitance value such as 2200 [pF] are connected between the commercial power supply potential and the housing 32 grounded, the leakage of the common mode noise indicated by the broken line in FIG. In a high frequency range from several megahertz to several tens megahertz due to series resonance due to the inductance of the path (about 0.1 to about 10 [μH]) and its capacitance, the leakage noise level rapidly increases near the resonance frequency. An increasing phenomenon occurs. For reference, FIG.
“PF”, inductance 1 [μH], and resistance 1 [oh]
m] shows the frequency characteristic of the absolute value of the series impedance. However, in the above embodiment, since the resistors 22 and 24 are connected in series to the filter capacitors 21 and 23, respectively, as shown in FIG. 3B, the resistors suppress the sharpness of the resonance and reduce the common frequency around the resonance frequency. An increase in the mode noise level can also be suppressed.

Further, since the capacitance of the filter capacitors 21 and 23 is as small as 2200 [pF], for example, at a commercial power supply frequency of 60 [Hz],
Filter capacitor 21 or filter capacitor 2
The absolute value of the impedance of 3 is about 1.2 mega [ohm].
, The series circuit of the filter capacitor 21 and the resistor 22 and the filter capacitor 23 and the resistor 24
The commercial power frequency component of the current flowing in the series circuit can be made a very small value, and the power loss due to the resistor 22 or the resistor 24 can be reduced, so that a small resistor can be used, and Can be easily installed.

As described above, according to the present embodiment, about 400 [kHz] is set between the commercial power supply potential and the grounded housing 32.
Up to the vicinity, the magnitude of the impedance decreases in proportion to the frequency, and at a frequency of about 400 [kHz] or more, the magnitude of the impedance becomes substantially constant. The series circuit of the filter capacitor 21 and the resistor 22 or the filter capacitor 23 and the resistor By connecting the series circuit of 24, the effect of reducing the leakage noise due to the bypass effect of the common mode noise to the housing 32 is utilized, and the excessive supply of the high frequency component to the housing 32 is restricted. Suppress high-frequency noise radiating from
It can effectively remove common mode noise leaking to a commercial power supply.

In the above embodiment, two resistors, the resistor 22 and the resistor 24, are used. However, a filter capacitor 21 and a filter capacitor 23 are connected in series between a commercial power supply, May be connected with one resistor.

The magnitude of the high-frequency common mode noise varies according to the size and shape of the housing 32, the length of the internal wiring, or the positional relationship between the housing 32 and the internal electric components and internal wiring components. Since it is related to the characteristics of other filter components, the capacitance values of the filter capacitor 21 and the filter capacitor 23 and the resistance values of the resistors 22 and 24 may be selected to be optimum values. 2 of c
A frequency characteristic of an absolute value of a series impedance including a capacitor having a capacitance of 200 [pF], an inductance component of 1 [μH] and a resistance of 10 [ohm], and 47 in FIG.
A frequency characteristic of an absolute value of a series impedance composed of a capacitor having a capacitance of 00 [pF], an inductance component of 1 [μH] and 1 k [ohm], or a frequency of an absolute value of the impedance shown in FIGS. As shown by the characteristics, the capacitance of the filter capacitors 21 and 23 is about 100 [pF] to 0.01 [μF], and the resistance is about 1 [pF].
The maximum effect can be obtained by selecting within the range of 0 to about 10 k [ohm].

Further, when the housing 32 is made of a non-conductive material, a series circuit of a filter capacitor and a resistor may be connected between a grounded inner conductive chassis or a grounded conductive metal part and a commercial power supply potential. Similar effects can be obtained.

When there are a plurality of inverters, the connecting points of two capacitors connected in series between the commercial power supply potentials at the inputs of the inverters are collectively connected to the conductive portion of the housing grounded from the collective points. Since the same effect can be obtained even if the connection is made via a single resistor, the number of components can be reduced.

The input power supply may be a DC power supply instead of the commercial power supply 33 which is a low-frequency AC power supply. In that case, the rectifier 26 becomes unnecessary.

In the above embodiment, the impedance having the required characteristics was obtained in the series circuit of the resistor and the capacitor. However, the impedance element having the above-mentioned characteristics, for example, the high-frequency loss was intentionally increased. A capacitor may be used, or may be combined by another method to have a combined impedance having the characteristics described above, for example,
A capacitor synthesized in a distributed constant manner may be used.

When a resistor element such as a normal film resistor or a wire-wound resistor is used as the resistor 22 and the resistor 24, the resistor has a very small inductance and the capacitance of FIG. 3C becomes 2200 [pF]. Capacitor and 1 [μH]
As shown by the frequency characteristics of the absolute value of the series impedance of the inductance component and the resistance of 10 [ohm], the absolute value of the impedance may increase at high frequencies (for example, several [MHz] or more). It has the effect of suppressing high-frequency common mode noise radiated from the surroundings to the surroundings, and equivalently, the series resistance component need only be about 10 [ohm] or more.

[0042]

As described above, according to the present invention, a DC or low-frequency power supply potential supplied to a frequency converter and a conductive portion of a housing grounded to ground by grounding means, or the power supply potential and ground. Means having a series resistance component of not less than about 10 ohms and not more than about 10 kohms between the conductive parts of the parts which are grounded to the earth and which are attached to or disposed on the housing, and whose absolute value is substantially equal to the frequency up to near a predetermined frequency. By connecting a proportionally decreasing impedance, it is possible to suppress the leakage of common mode noise over a wide frequency range from low frequencies to high frequencies to the commercial power supply by simply adding components that are small and easy to mount on equipment. In particular, 500 [kHz] cannot be sufficiently filtered by simply connecting only a filter capacitor between the DC power supply potential portion or the commercial power supply potential portion and the ground potential. It is possible to suppress the common mode noise in] or more frequencies, but can be realized with less good induction heating cooker of leakage noise.

[Brief description of the drawings]

FIG. 1 is a circuit block diagram of an induction heating cooker according to a first embodiment of the present invention.

FIG. 2 is a frequency characteristic diagram of an absolute value of impedance of a series circuit of a resistor and a capacitor in the first embodiment of the present invention.

FIG. 3 is a frequency characteristic diagram of an absolute value of a series impedance of a resistance, a capacitor, and an inductance component in the first embodiment of the present invention.

FIG. 4 is a circuit block diagram of a conventional induction heating cooker.

[Explanation of symbols]

 18c ground wire (ground means) 21 filter capacitor 22 resistor 23 filter capacitor 24 resistor 29 heating coil 30 inverter (frequency conversion device) 32 housing

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Yoshihiro Yamashita 1006 Kadoma, Kazuma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (56) References JP-A-5-89955 (JP, A) 49397 (JP, U) Jikken 61-16621 (JP, Y2) (58) Fields investigated (Int. Cl. ⁶ , DB name) H05B 6/12 319

Claims (1)

(57) [Claims] 1. A frequency converter for inputting electric power from a DC power supply or a low-frequency power supply and generating a high-frequency current in a heating coil for inductively heating a load, and a part or all of components constituting the frequency converter are housed. And a grounding means for grounding a conductive part of the housing or a component attached to or disposed on the housing to ground, wherein the DC power supply potential unit or the low frequency input to the frequency converter is provided. Between the power supply potential portion and the conductive portion of the housing grounded to the ground by the grounding means, or the DC power supply potential portion or the low frequency power supply potential portion and the grounding means grounded to the housing and attached to the housing or It has a series resistance component of not less than about 10 ohms and not more than about 10 kohms between the conductive part of the component and the absolute value thereof is approximately proportional to the frequency up to a predetermined frequency. Induction heating cooker has a structure for connecting the impedance to be small.