JPH11297461A - Induction heat cooking device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect the temperature of a switching element of an induction heat cooking device, in a simple constitution and with good responsiveness. SOLUTION: A terminal part of a thermistor 31 is solder-connected to copper foil patterns 31a, 31b from the copper foil pattern side of a printed wiring board 33 adjacent to an emitter terminal 37 of an inverse continuity transistor 25, and the thermistor 31 is thermally coupled with a semiconductor part of the inverse continuity transistor 25 through the emitter terminal 37 as a main heat conductivity passage. A high-reliability and low-cost induction heat cooling device, capable of detecting failure of a cooling system or rapid abnormal temperature rise of the inverse continuity transistor 25 with satisfactory responsivenes can thus be provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an induction heating cooker having a frequency converter for turning on and off a switching semiconductor and supplying a high frequency current to a heating coil by resonance.

[0002]

2. Description of the Related Art Conventionally, a temperature sensor is fixed to a cooling fin in which a switching element is fixed for cooling, and the temperature of the switching element of a frequency converter such as an inverter for supplying a high-frequency current to a heating coil is fixed. An induction heating cooker that controls the output of a frequency conversion device based on the temperature detected by a sensor has been developed.

[0003] A conventional induction heating cooker will be described below. FIG. 8 is a block circuit diagram of a conventional induction heating cooker having a two-stone inverter. A full-wave rectifier (hereinafter referred to as a rectifier) 2 is connected to a commercial power supply 1, a choke coil 3 is connected to a positive output terminal of the rectifier 2, and a smoothing capacitor is connected between the other end of the choke coil 3 and a negative output terminal of the rectifier 2. 4 are connected. A series circuit of a transistor 5, a forward diode 7 and a transistor 8 is connected to both ends of the smoothing capacitor 4. A diode 6 is connected in antiparallel to the transistor 5 on the high potential side, and a diode 9 is connected in antiparallel to the transistor 8 on the low potential side. A series circuit of a heating coil 10 and a capacitor 11 is connected between a connection point between the cathode of the diode 7 and the collector of the transistor 8 and a negative electrode of the rectifier 2, and a diode 12 is connected in parallel with the capacitor 11.

The parts surrounded by the dashed lines 13 are parts fixed to the aluminum cooling fins 13 shown in FIG. That is, transistor 5, diode 6, diode 7,
The rectifier 2 is fixed to the cooling fins 14 and is cooled by a cooling fan. Components surrounded by wavy lines 14 are components fixed to the cooling fins 13 shown in FIG. That is, the transistor 8, the diode 9, and the diode 12 are fixed to the cooling fin 14, and as shown in FIG.
Cooled by cooling air.

In the transistor 8 shown in FIG. 8, the external metal base of the element package has the same potential as the collector terminal.
The metal base is screwed and fixed so as to contact the cooling fin 14. Similarly, the transistor 5 has an external metal base of the element package at the same potential as the collector terminal, and is fixed with screws so that the metal base is in contact with the cooling fins 13. The cooling fins 13 and 14 are screwed and fixed from the back side to the printed wiring board 14 having wiring printed on the back side with copper foil, and the terminals of the semiconductor elements fixed to the cooling fins 13 and 14 such as the transistors 5 and 8 are printed. It is bent toward the wiring board 18, penetrates a hole provided in the printed wiring board 18, and is immersed in a solder bath together with the copper foil pattern of the printed wiring board 18 on the back side to be connected by soldering.

The cooling fin 13 includes a thermostat 16
Are fixed with an adhesive, and transistors 5 and 8
Is connected to a control circuit 15 for controlling the on / off of the power supply.
In the vicinity of the cooling fin 14, the thermistor 17 bends a lead wire from the front surface side of the printed wiring board 18, penetrates the hole of the printed wiring board, and connects the cooling fin 1 to the printed wiring board 18 on the back side.
It is connected and fixed in the same manner as the semiconductor elements fixed to 3 and 14.

[0007]

In the induction heating cooker described above, the cooling fins 13 have the same potential as the collector potential of the transistor 5, and the cooling fins 14 have the same potential as the collector potential of the transistor 8. Since the thermostat 16 and the thermistor 17 are connected to the control circuit 15, and the control circuit 15 uses the common potential as the emitter of the transistor 8, a high voltage is applied between the thermostat 16 and the cooling fins 15, and between the thermistor 17 and the cooling fins 14. Is done.

Therefore, in the above-described configuration of the induction heating cooker, it is necessary to provide an insulating member that can withstand the high pressure between the thermostat 16 and the cooling fins 13. In addition, an operation such as bonding and fixing the thermostat 16 to the cooling fin 13 or fixing with a screw using a fixing metal is required. In addition, it is necessary to provide an insulation distance corresponding to the voltage between the thermistor 17 and the cooling fins, and the thermistor 17 transfers the heat of the cooling fins 13 by the insulating distance of the printed wiring board 18 by the insulation distance. At the same time, the thermistor element portion and the lead portion are exposed above the printed wiring board and are cooled by the cooling air of the cooling fan 19, so that the cooling fin 13
The temperature detection sensitivity is poor. For example, when the power supply switch is turned off and the heating operation is stopped, and at the same time the cooling fan 19 is stopped, the cooling fins 14 and other heat generating components cause
There was a risk that the detected temperature would not drop immediately and would overshoot, resulting in erroneous detection.

The present invention provides an inexpensive induction heating cooker that can detect the temperature of a semiconductor switching element constituting an inverter with high sensitivity and perform a protective operation with good responsiveness in response to a failure of a cooling fan or an abnormality of a cooling system. The purpose is to:

[0010]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention relates to a method of connecting a temperature sensing element for outputting a signal to a control circuit having a low potential side terminal of a switching element as a common potential and a semiconductor section of the switching element. The temperature sensing element is arranged on the printed wiring board so that the thermal coupling is performed using the low potential side terminal of the switching element as its main heat conduction path, and the terminal part of the temperature sensing element does not penetrate the substrate. From the conductor foil side,
It is configured to be connected by soldering to the conductor foil of the printed wiring board.

As a result, the heat generated by the power loss of the semiconductor portion of the switching element is conducted to the low potential side terminal having good thermal conductivity because of the conductive metal material, so that the semiconductor portion of the switching element and the switching element The thermal resistance between the solder connection between the low potential side terminal and the printed wiring board is reduced.

Further, the temperature sensing element is configured to output a signal to a control unit having the low potential side terminal of the switching element as a common potential, and a voltage of about 40 V is normally applied between the temperature sensing element and the low potential side terminal of the switching element. Only the following low voltage is applied.Even if the distance between them is reduced, there is no risk of dielectric breakdown or high frequency noise being transmitted to the control unit by coupling due to stray capacitance between the connection lines. The thermal resistance between the connection between the potential side terminal and the conductor foil of the printed wiring board and the temperature sensing element can be minimized.

Further, since the terminal portion of the temperature sensing element is connected to the conductor foil of the printed wiring board by soldering from the conductor foil side without penetrating the printed wiring board, the terminal portion of the temperature sensing element can be minimized. Heat radiation at the lead part due to cooling air etc. is suppressed,
Thermal resistance between the solder connection part and the temperature sensing part of the temperature sensing element can be minimized.

As described above, the thermal resistance between the semiconductor part of the switching element and the temperature-sensitive part of the temperature-sensitive element is minimized in the heat conduction path, and the temperature of the temperature-sensitive element changes with the temperature change of the semiconductor part of the switching element. By following quickly, an induction heating cooker capable of detecting an abnormality in the cooling system or an abnormality in the element and accurately controlling the output can be obtained.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention according to claim 1 is a heating coil, a switching element having terminals penetrated and soldered to a printed wiring board having a conductor foil adhered to the surface of an insulating member, and the switching element. A temperature-sensing element thermally coupled to the semiconductor part, and changing the control content in accordance with a detection result of the temperature-sensing element, and controlling on / off of the switching element with the low potential side terminal of the switching element as a common potential. A frequency converter for generating a high-frequency current in the heating coil, wherein a thermal coupling between the temperature-sensitive element and the switching element causes a low-potential side terminal of the switching element, through which a main current flows, to generate heat. The temperature-sensitive element is disposed on the printed wiring board so that the temperature-sensitive element is provided as a conduction path, and the terminal of the temperature-sensitive element does not penetrate through the substrate, and is connected to the conductive foil side. Et al., Is obtained by an induction heating cooker configured to connect soldered to the conductor foil of the printed circuit board, heat generated in the power loss of the semiconductor portion of the switching element,
Since it is a conductive metal material and conducts through the low potential side terminal through which the main current with good thermal conductivity flows, the thermal resistance between the semiconductor part of the switching element and the solder connection between the low potential side terminal of the switching element and the printed wiring board Becomes smaller. In addition, since the temperature sensing element is configured to output a signal to a control unit having the low potential side terminal of the switching element as a common potential, a voltage of about 40 V or less is normally applied between the temperature sensing element and the low potential side terminal of the switching element. By applying a low voltage only and reducing the distance between the conductive foil of the printed wiring board connected to the low potential side terminal of the switching element and the temperature sensitive element, malfunction due to high frequency noise or insulation breakdown may occur. There is no danger that the thermal resistance between the low potential side terminal of the switching element and the temperature sensitive element can be reduced. In addition, since the terminal of the temperature-sensitive element is configured to be soldered to the conductor foil of the printed wiring board from the conductor foil side without penetrating the printed wiring board, the terminal of the temperature-sensitive element is minimized and cooling is achieved. Heat radiation at the terminal portion due to wind or the like is suppressed, and the thermal resistance between the solder connection portion and the temperature-sensitive portion of the temperature-sensitive element can be reduced. From the above, the thermal resistance between the semiconductor part of the switching element and the temperature sensing part of the temperature sensing element is minimized in the heat conduction path, and the rapid temperature change of the switching element is detected with high sensitivity, and the abnormality of the cooling system is detected. It has an effect of being able to detect abnormality of the element and the element with high accuracy.

According to a second aspect of the present invention, the temperature sensing element has an insulating property to the conductor foil extending from the low potential side terminal of the switching element and the solder connection part of the conductor foil. Through the adhesive, by making the induction heating cooker disposed to face, heat conducted through the low potential side terminal of the switching element is conducted to the temperature-sensitive element via the extended conductive foil and the adhesive, The thermal resistance between the low potential side terminal of the switching element and the temperature sensing part of the temperature sensing element can be further reduced, and the rapid temperature rise of the semiconductor part of the switching element can be detected by the temperature sensing element with better responsiveness. There is.

According to a third aspect of the present invention, in addition to the configuration of the first or second aspect, the temperature-sensitive element is
The thermal coupling between the temperature-sensitive element and the semiconductor portion of the switching element is arranged such that the low potential side terminal of the switching element through which the main current flows is used as its main heat conduction path, so that the conductive metal material is usually used. By passing the main current of the switching element, which is a high-frequency large current, to the terminal part of the switching element composed of a single wire, the terminal part itself or the conductor foil of the printed wiring board to which the terminal part is connected has a skin effect or Because it generates heat due to its large current value,
Corrects the amount of heat that is lost due to the cooling air hitting the terminals and the heat dissipated from the printed wiring board, and increases the amount of heat transferred to the temperature-sensitive element. As a result, the output can be suppressed.

According to a fourth aspect of the present invention, the heating coil and the case portion formed by molding the semiconductor portion with resin are fixed to the cooling fins, and the terminals are soldered to the connection lines formed by the conductor foil of the printed wiring board. A second switching element on the high potential side and a first switching element on the low potential side to be connected;
A frequency converter for generating a high-frequency current in the heating coil by alternately conducting the first switching element and the second switching element, and fixing the first switching element and the second switching element to the same cooling fin; The space between the conductor foils connected between the terminals of the first switching element through which the main current flows and the space between the conductor foils connected to both terminals of the second switching element through which the main current flows is formed by the cooling fin. An induction heating cooker configured to cover simultaneously, wherein the first switching element is thermally coupled to the second switching element, and abnormal heat generation of the semiconductor portions of the first switching element and the second switching element. Can be simultaneously detected by a single temperature-sensitive element, and the cooling fins are connected to the first switching element on the high potential side and the cooling fin for the first switching element on the low potential side. Radiation that is not divided into two for the switching element and covers the space between the conductor foils through which the main current flows, which is connected to the first switching element and the second switching element, without any gap, and leaks from the gap between the cooling fins Since the noise is eliminated, radiation noise generated from the space between the conductive foils when the first and second switching elements are turned on and off alternately can be reduced.

According to a fifth aspect of the present invention, in addition to the configuration of the first, second, or third aspect, a case in which the semiconductor portion is molded from resin is fixed to the cooling fins and printed wiring is provided. A second switching element on the high-potential side and a first switching element on the low-potential side, the terminals of which are connected by soldering to connection lines formed of a conductive foil of the plate, and thermal coupling with the semiconductor portion of the first switching element And the control content is changed in accordance with the detection result of the temperature sensing element, and the low potential side terminal of the first switching element is set to a common potential to turn on / off the first switching element and the second switching element. And a frequency converter for generating a high-frequency current in the heating coil by alternately conducting the first switching element and the second switching element, And the second switching element are fixed to the same cooling fin, so that the cooling fin simultaneously covers the space between the conductor foils, through which the main current flows, connected to the first switching element and the second switching element. And the thermal sensing element is connected to the semiconductor portion of the first switching element by using the low-potential side terminal of the first switching element as its main heat conduction path. With the induction heating cooker configured to be disposed on the printed wiring board, heat generated by power loss of the semiconductor portion of the first switching element is a conductive metal material, has good thermal conductivity, and has a long length. Since the short terminal portion is transmitted as a main heat conduction path and reaches the solder connection portion on the conductor foil of the printed wiring board, the semiconductor portion of the first switching element and the solder connection portion Heat resistance becomes small.

The temperature sensing element is configured to output a signal to a control unit having the low potential side terminal of the first switching element as a common potential, and to output a signal between the temperature sensing element and the low potential side terminal of the first switching element. Since only a low voltage of about 40 V or less is normally applied and there is no danger of dielectric breakdown, the distance between the two is reduced so that the solder connection portion of the low potential side terminal of the first switching element and the temperature sensitive element The thermal resistance between them can be reduced.

Further, since the terminal portion of the temperature sensing element is connected to the conductor foil of the printed wiring board by soldering from the conductor foil side without penetrating the printed wiring board, the terminal portion of the temperature sensing element can be minimized. Thus, heat radiation at the terminal portion due to cooling air or the like is suppressed, and the thermal resistance between the solder connection portion of the low potential side terminal of the first switching element and the temperature sensing portion of the temperature sensing element can be reduced.

From the above, the thermal resistance between the semiconductor section of the first switching element and the temperature sensing section of the temperature sensing element is minimized in the heat conduction path to follow the temperature of the semiconductor section of the first switching element. Thus, the output can be accurately detected, and the output can be accurately controlled in accordance with the rapid temperature change caused by the abnormality of the cooling system or the abnormality of the frequency converter.

Further, the first switching element and the second switching element are fixed to the same cooling fin, and the first switching element is thermally coupled to the second switching element. Therefore, the semiconductor portion of the second switching element Can also be detected at the same time.

Further, since the cooling fin is not divided into two parts, one for the high-potential side switching element and one for the low-potential side switching element, the conductor foil through which the main current flows is connected to the first switching element and the second switching element. And the radiation noise leaking from the clearance between the cooling fins is eliminated, so that the effect of reducing the radiation noise generated when the first and second switching elements are turned on and off can be increased. .

According to a sixth aspect of the present invention, there is provided the configuration according to the fourth or fifth aspect, further comprising a cooling fan for blowing air to the cooling fins, and reducing a loss of the first switching element and the second switching element. The smaller one is an insulation type package that electrically insulates the semiconductor portion from the cooling fins, and the larger one is a non-insulating package that electrically insulates the specific electrode of the semiconductor portion from the cooling fins. A semiconductor part of a switching element having a large loss by adopting an induction heating cooker having a configuration in which the switching element of the non-insulating type package is fixed to the cooling fan side more than the switching element of the insulating type package. -To reduce the thermal resistance between the cases and increase the heat dissipation to the cooling fins to enhance the cooling effect of the semiconductor part of the switching element with large loss, By placing the leeward of the cooling air can reduce the heat influence on the case temperature of the insulating type switching element. On the other hand, the switching element of the insulation type package having a large thermal resistance between the semiconductor portion and the cooling fin is used as a side having a small loss to reduce the temperature difference between the semiconductor portion and the case, and to the cooling fan side (upwind). By reducing the effect of heat transmitted from the non-insulating type switching element to the cooling fins with a large semiconductor part loss and suppressing the rise of the case temperature and reducing the temperature rise of the semiconductor part In addition, the semiconductor device of the first switching element and the second switching element has an effect of suppressing the temperature rise in a well-balanced manner and cooling.

[0026]

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

As shown in FIG. 1, a rectifier 21 for performing full-wave rectification is connected to a commercial power supply 20, and a choke coil 22 is connected to its positive electrode. A smoothing capacitor 27 is connected between the load terminal of the choke coil 22 and the negative terminal of the rectifier 21. A series circuit of a reverse conducting transistor 25 in which a transistor 25a and a diode 25b are packaged in one package and a heating coil 26 are connected to both ends of the smoothing capacitor 27, and a resonance capacitor 24 is connected in parallel with the heating coil 26. The transformer 29 has a primary coil connected to the commercial power supply 20, and the power supply circuit 30
From the secondary coil is supplied with an AC voltage reduced to about 30V. The control circuit 28 inputs a control DC power supply from the power supply circuit 30. The thermistor 31 is a temperature detecting element of the reverse conducting transistor 25 and is connected to the control circuit 28.

FIG. 2 shows the reverse conducting transistor 25 of FIG.
FIG. 4 is a partial perspective view showing a state where the cooling fins 32 and the thermistor 31 are mounted on a printed wiring board 33. The cooling fin 32 is fixed to the printed wiring board 3 by screws 34, 35, 36.
5 and fixed. As shown in the cross-sectional view of FIG.
2, the conductive metal plate 38b is exposed at the contact surface with the cooling fins 32. The conductive metal plate 38b is connected to the collector of the semiconductor chip 25c and the cathode of the diode 25b, and has the same potential as the external collector terminal 38. ing.

The emitter terminal 37 which is a low potential side terminal through which the main current of the reverse conducting transistor 25 flows, the collector terminal 38 which is a high potential side terminal through which the main current flows, and a low potential side terminal to which a drive signal is applied. The gate terminal 39 is bent, penetrates a hole provided in the printed wiring board 33, and is connected to a pattern 37 b, 38 b, 39 b formed of a copper foil having a thickness of about 35 μm on one surface of the printed wiring board 33,
a, 38a, and 39a are respectively connected by soldering.

The thermistor 31 has a substantially rectangular parallelepiped shape.
As shown in the sectional view of FIG. 4, soldered connection portions 31c and 31d are provided at both ends, and are mounted between the connection portion 37a of the emitter terminal 37 and the gate terminal 39a.
At the solder connection portions formed by partially removing the insulating film 41 from the copper foil patterns 31a and 31b for connection to the soldering portions 8, the soldering portions 31e and 31f are attached and connected. Further, a copper foil pattern 37 near the connection portion 37a of the emitter terminal 37 is provided between the thermistor 31 and the printed wiring board 32.
A copper foil pattern 37c extending from b is provided, filled with an electrically insulating adhesive 42, and fixed so that the thermistor 31 and the copper foil pattern 37c face each other.

The operation of the heating cooker configured as described above will be described. The rectifier 21 receives the commercial power supply 20 and performs full-wave rectification. The choke coil 22, the smoothing capacitor 27, the resonance capacitor 24, the heating coil 26, and the reverse conducting transistor 25 are one type of a frequency conversion device.
A stone inverter is configured to input a low frequency direct current to generate a high frequency current in the heating coil 26. The control circuit 28 connects the common potential to the emitter terminal of the transistor (IGBT) 25a, outputs a pulse of about 20 V between the gate terminal and the emitter terminal of the transistor 25a,
By turning on and off 5 a, a high-frequency current is generated in the heating coil 26 by resonance between the heating coil 26 and the resonance capacitor 24. The control circuit 28 includes a current transformer 28
a, the input current is supplied to the transistor 25 via the resistor 28b.
The voltage between the collector and the emitter of a is monitored by monitoring the temperature of the semiconductor portion of the reverse conducting transistor 25 with the thermistor 31.
The output is controlled by controlling the on / off of the transistor 25a, the display content is changed, or the intensity of the cooling air is changed by changing the rotation speed of the cooling fan and the like.

The reverse conducting transistor 25 conducts and cuts off a large current of several tens of amperes at a peak value and has a frequency of about 20 to 50 kHz, so that a turn-on loss, a turn-off loss, or a power loss due to a forward voltage / current of the diode 25b is reduced. Semiconductor portion 25 of reverse conducting transistor 25
Occurs in c. The heat generated by this loss is conducted to the cooling fins 32, which are air-cooled by the cooling fan, through the metal base 38b to which the collector is connected, and radiated.

On the other hand, the heat of the semiconductor portion 25c is conducted to the emitter terminal 37 via the bonding wire and the resin, and the copper foil pattern 37 printed on the printed wiring board 33 is formed.
Through the solder connection portion 37a with b, the conduction is made to the copper foil pattern 37c (the same potential as the copper foil pattern 37b) extended in a tongue shape. The copper foil pattern 37c intersects the thermistor 31 as shown in FIG. 4 and faces the thermistor 31, and the adhesive 42 is filled between the insulating film 41 coated on the pattern 37c and the thermistor 31. Therefore, even through these members, the heat is stably conducted to the temperature sensing portion of the thermistor 31.

Further, since the thermistor 31 is connected to the control circuit 28 having the common potential as the common potential (common potential) at the emitter of the reverse conducting transistor 25, the thermistor 31 is connected to the terminals 31c and 31d of the thermistor 31 and to them. The voltage applied between the copper foil patterns 31a and 31b and the copper foil patterns 37b and 37c connected to the solder connection portion 37a of the emitter terminal and the emitter of the reverse conducting transistor 25 can be usually about 40 V or less. Since there is little danger of insulation breakdown between them and crosstalk of high-frequency noise, the distance between them on the printed wiring board is set to a small distance of at least about 0.5 mm. This allows
The heat transmitted from the reverse conducting transistor 25b and the semiconductor portion 25c to the emitter terminal 37 as a heat conduction path is transferred to the solder connection portion 37a of the emitter terminal 37 and the printed wiring board 33.
Terminal part 31 of the thermistor 31 via the resin material of
c, 31d, or a copper foil pattern 37b,
The conduction from the thermistor 31 to the thermistor 31 is facilitated in a path extending from the terminal 37c to the terminals 31c and 31d of the thermistor 31 via the patterns 31a and 31b.

Further, since the thermistor 31 is provided between the solder connection portion 37a of the emitter terminal and the solder connection portion 39a of the gate terminal, the heat of the semiconductor portion of the reverse conducting transistor 25 is also transmitted from the gate terminal 39. The amount of heat received by the thermistor 31 can be increased.

The terminal of the transistor is made of a copper alloy.
Normally, the cross section is in the form of a plate with a side of about 1 mm. Considering the assemblability of the transistor itself or the workability of rolling the transistor and soldering it to a printed wiring board, it is difficult to enlarge the cross section. is there. On the other hand, since a large high-frequency current flows through the emitter terminal 37, a skin effect is added, and the terminal generates heat. Similarly, the copper foil patterns 37b and 38b connected to the emitter terminal 37 also generate heat. These heat values are proportional to the loss of the semiconductor portion of the reverse conducting transistor. As described above, since the emitter terminal 37 itself generates heat, of the heat conducted from the semiconductor portion, the amount of heat radiated from the terminal portion and the copper foil pattern portion 37 is supplemented, and as a result, the amount of heat received by the thermistor 31 increases. I do.

As described above, according to the present embodiment, the heat generated by the power loss of the semiconductor portion 25c of the reverse conducting transistor 25 is conducted through the emitter terminal 37 made of copper and having good heat conductivity. Then, the thermal resistance between the solder connection portions 37a decreases. Further, since the thermistor 31 is configured to output a signal to the control unit 28 having the emitter terminal 37 as a common potential, the thermistor 31 and the emitter terminal 37
A voltage of about 40 V or less is normally applied between the copper foil pattern 37b of the printed wiring board connected to the solder connection portion 37a or the emitter terminal 37a and the copper foil pattern connected to the thermistor 31 itself or the thermistor 31 3
Even if the distance between 1a and 31b is reduced, there is no danger of malfunction due to high frequency noise due to the coupling by the stray capacitance between the copper foil patterns or dielectric breakdown. The thermal resistance between 37 and the thermistor 31 can be reduced. Also, the terminal portions 31c and 31d of the thermistor 31 are not penetrated through the substrate, but from the copper foil side.
Since the connection is made by soldering to the copper foil patterns 31a and 31b, the terminal portion of the thermistor 31 is minimized, heat radiation at the lead portion due to cooling air or the like is suppressed, and the solder connection portion 37a and the temperature sensing portion of the thermistor 31 are formed. The thermal resistance between them can be reduced. Therefore, the thermal resistance between the semiconductor part 25c and the temperature sensing part of the thermistor 31 is minimized in the heat conduction path, and the rapid temperature rise of the semiconductor part 25c is detected with high sensitivity, and the abnormality of the cooling system or the abnormality of the element is detected. Can be detected with high accuracy.

The thermistor 31 has an emitter terminal 37.
a is connected to the copper foil pattern 37c having the same potential as the copper foil pattern 37b to which the solder is connected by an insulating film and an insulating adhesive,
By being opposed and fixed, the copper foil pattern 37
c, the heat is stably conducted to the thermistor 31 via the insulating film 41 and the adhesive 42, so that the thermal resistance between the solder connection portion 37a and the thermistor 31 can be further reduced, and the thermistor 31 is connected to the semiconductor portion 25c. A rapid temperature rise can be detected with better responsiveness.

The thermistor 31 and the copper foil pattern 31 are so connected that the thermal connection between the thermistor 31 and the semiconductor portion 25c is performed using the emitter terminal 37 as a heat conduction path.
a and 31b are connected to the solder connection portion 37a and the copper foil pattern 3
7b and 37c, when a high-frequency, large-current main current is applied to the emitter terminal portion 37 composed of a single wire, the terminal portion itself or the conductive foil of the printed wiring board connected to the terminal portion is removed. Since heat is generated due to the skin effect and the large current value, the heat corrects the heat radiation from the terminal portion 37 and the printed wiring board, and the amount of heat received by the thermistor 37 during operation increases. When the switching element is operated in the state where
The thermistor 37 can respond to a rapid rise in the temperature of the semiconductor portion of the switching element with high sensitivity and suppress the output.

(Embodiment 2) A second embodiment of the present invention will be described below with reference to FIG.

FIG. 5 is a circuit diagram showing a two-stage inverter. A rectifier 52 for performing full-wave rectification is connected to a commercial power supply 51.
A choke coil 53 is connected to the positive electrode side. A smoothing capacitor 58 is connected between the load terminal of the choke coil 53 and the negative terminal of the rectifier 52. A transistor 59a and a diode 59b are provided at both ends of the smoothing capacitor 58.
Are connected in series with a series circuit of a reverse conducting transistor 59 and a heating coil 57 in a single package.
A diode 59b is connected in antiparallel to a. A capacitor 54, a series circuit of the capacitor 55 and the transistor 26 are connected in parallel with the heating coil 57, and a diode 60 is connected in antiparallel to the transistor 59.

The control circuit 61 sets the emitter of the reverse conducting transistor 59 to a common potential, outputs a pulse between the emitter and the gate, and supplies the driving circuit 63 with the transistor 5.
6 is output. The drive circuit 63 includes a photocoupler, and outputs a pulse between the emitter and the gate of the transistor 56 according to a drive signal of the control circuit 61. The thermistor 62 is a temperature detecting element of the reverse conducting transistor 59 and is connected to the control circuit 63.

As shown in FIG. 6, the rectifier 52, the transistor 56, the diode 60, and the reverse conducting transistor 59 are fixed to the cooling fin 65 with screws in the same manner as in the first embodiment. FIG. 4 is a plan view showing a schematic arrangement in a case where the semiconductor device is inserted into a hole of FIG. The cooling fin 32 has a sectional shape as shown in FIG. 7 and is extruded. FIG.
A cooling fan is disposed in the upper direction of the cooling fan, and cooling air is blown from above to below.

In FIG. 6, a portion indicated by a dashed line and a hatched portion is a copper foil pattern on the back surface of the printed wiring board 64, and the collector terminal and the emitter terminal of the transistor 56 and the reverse conducting transistor 5
9 shows the respective terminals and the peripheral portion of the place where the terminals of the thermistor 31 are soldered. Copper foil pattern 67
Since a high voltage of about 100 V is applied between the copper foil pattern 66c, the copper foil pattern 67b and the copper foil pattern 68b, and between the copper foil pattern 70a and the copper foil pattern 67b, a distance of about 4 mm is provided. Both ends of the bar-shaped thermistor 62 are connected by soldering to the copper foil patterns 62a and 62b. Near the solder connecting portion 68a of the emitter terminal 66, a distance of about 0.3 mm from the copper foil pattern 66b is provided. , 62b are arranged so as to surround them. The copper foil pattern 68b connected to the gate of the transistor 59 also has a portion adjacent to the copper foil pattern 62b at an interval of about 0.3 mm near the thermistor 62a.

The operation of the heating cooker configured as described above will be described. When the transistor 59b is conducting, a current flows at a constant gradient from the smoothing capacitor 58 via the heating coil 57, and when the transistor 59a is turned off (time t1), the heating coil 57 is turned on by the energy accumulated in the heating coil 57. Resonates with the capacitor 54,
A resonance voltage is applied between the collector and the emitter of the transistor 59b.

When the collector potential of the transistor 59b rises due to resonance and reaches the cathode potential of the diode 60 (time t2), a current flows through the diode 60, and the capacity of the capacitor 55 is reduced from about 10 to 2 times the capacity of the capacitor 54.
If it is set to a sufficiently large capacity of 0 times or more, the heating coil 5
7, a current that increases with a substantially constant gradient flows, and the voltage is clamped. During this time, a current that decreases with a substantially constant gradient flows through the diode 60. If the transistor 56 is driven and kept in a standby state when a current is flowing through the diode 60, even if the current of the diode 60 becomes zero, a current that increases with a substantially constant slope is heated via the transistor 56. The current flows through the coil 57 and the clamped state of the resonance voltage is continued.

After that, when a current flows through the heating coil 57 via the transistor 56 and the transistor 56 is turned off (time t3), the energy stored in the heating coil 57 causes the heating coil 57 and the capacitor 54 to resonate. As a result, the collector potential of the transistor 59 decreases in a short time.

When the collector potential of the transistor 59 decreases and reaches the emitter potential of the transistor 59 (time t4), a current flows through the diode 59b and is clamped at the emitter potential. At this time, a current that decreases at a constant gradient flows through the diode 59b. If the transistor 59a is driven to stand by while the current is flowing through the diode 59, the current flowing through the diode 59b becomes zero. Then, the transistor 59b becomes conductive, and a current that increases with a constant gradient flows through the heating coil 57 and the transistor 59b, and the collector of the transistor 59b maintains zero voltage.

Thereafter, at the time point t1, the transistor 5
9b turns off and the above operation is repeated. By making the repetition period constant and changing the off timing of the transistors at the time points t1 and t3, that is, by controlling the transistors 29 and 56 by the control circuit 31,
It is possible to control the current of the heating coil 57 and change the output by changing the ratio of the driving times of both while keeping the driving repetition cycle constant.

As described above, the transistor 56 clamps the resonance voltage between the heating coil 57 and the capacitor 60. The current when the transistor 56 is turned off is smaller than the value of the transistor 59a. In this case, the loss is similarly reduced by the transistor 5
The transistor 56 is smaller than 9a. As an example of the configuration of the present embodiment, in an experiment in which an input of 200 V and an output of 2 kW is obtained, the loss of the transistor 56 is about 20%.
As for the reverse conduction transistor 59, the transistor 59a has a data of about 40 W and the diode 59b has a data of about 5 W with a total of 45 W.

As described above, the current of the transistor 56 and the diode 60 is suppressed to reduce the loss, and both are separated and fixed on the windward side of the rectifier 52 and the cooling fin 65 as insulating packages, respectively, and the transistor 59a and the diode 59b are connected. By reducing the thermal resistance between the semiconductor portion and the case by reducing the thermal resistance between the semiconductor portion and the case by reducing the thermal resistance between the semiconductor portion and the case by integrally molding the package in the same package to reduce the size, the loss is increased. By suppressing the temperature rise of the semiconductor portion, the semiconductor element of the inverter can be mounted on the same cooling fin 65 and cooled in a well-balanced manner.

Further, since the thermistor 62 is soldered from the copper foil side to the end of the thermistor 62 by soldering in the vicinity of the solder connection portion 66a of the emitter terminal 66 of the reverse conduction transistor 59, the reverse conduction is performed with high sensitivity. The temperature of the semiconductor portion of the transistor 59 can be detected, and the transistor 56, the rectifier 52, and the diode 60 are thermally coupled to the reverse conducting transistor 59 via the cooling fins.

At time t1, time t2, time t3, and time t4 at which a discontinuity in the current waveform occurs due to turning on and off of the transistor 56 and the reverse conducting transistor 59, the transistor 5 is removed from the gap shown by A and B in FIG.
Radiation noise occurs at a frequency corresponding to the current waveform when the diode 6 and the reverse conducting transistor 59 are turned off and when the diode 60 and the diode of the reverse conducting transistor 59 are conducting. Because it covers, leakage to the outside can be suppressed.

Further, the copper foil pattern 31 formed on the printed wiring board 33 is formed by immersing the thermistor 31 in a solder bath.
a, 31b can be connected and fixed by soldering, so that the fixing and wiring work of the thermistor 31 are simplified, and the thermistor 31 and the connection line connected thereto are connected to the reverse conducting transistor 25 or the cooling fin 32 having the same potential as the reverse conducting transistor 25 or the cooling fin 32. ,
It can be fixed on the printed wiring board 33 so as not to be close to high-potential components such as a heating coil and strong magnetic field generating components.
The transmission of high-frequency noise to the control circuit 28 via the detection circuit of the thermistor 31 can be suppressed, and the influence of the high-frequency noise on the control circuit 28 due to variation in wiring work can be prevented.

As described above, the heat generated due to the power loss of the semiconductor portion of the reverse conducting transistor 59 is transmitted through the copper-made, high-heat-conductivity, short-length emitter terminal 66 as the main heat conduction path. The thermal resistance between the semiconductor portion of the reverse conducting transistor 59 and the solder connection portion 66a is reduced.

The thermistor 62 is configured to be connected to a control circuit 61 that uses the emitter of the reverse conducting transistor 59 as a common potential.
Since only a low voltage of about 40 V or less is normally applied between them and there is no fear of dielectric breakdown, the solder connection 66a or the copper foil pattern 66b of the emitter terminal 66 and the thermistor 6
2 or the distance between the copper foil patterns 62a and 62b can be reduced to reduce the thermal resistance between the solder terminal 66a and the thermistor 62.

The terminal portion of the thermistor 62 does not penetrate through the printed wiring board 64, and the copper foil pattern 6
2a and 62b, the terminal portion of the thermistor 62 is minimized, heat radiation at the terminal portion due to cooling air or the like is suppressed, and the heat between the solder connection portion 66a and the temperature sensing portion of the thermistor 62 is reduced. Resistance can be further reduced.

Therefore, the thermal resistance between the semiconductor portion of the reverse conducting transistor 59 and the temperature sensing portion of the thermistor 62 is minimized in the heat conduction path, and the temperature of the semiconductor portion of the reverse conducting transistor 59 is detected with good tracking. In addition, accurate output control can be performed in response to a sudden temperature change due to a cooling system abnormality or an element abnormality.

Further, since the reverse conducting transistor 59 and the transistor 56 are fixed to the same cooling fin 65 and the reverse conducting transistor 59 is thermally coupled to the transistor 56,
Abnormal heat generation of the semiconductor portion of the transistor 56 can be detected at the same time.

Further, since the cooling fin 65 is not divided into two, one for the transistor 56 on the high potential side and the other for the reverse conducting transistor 59 on the low potential side, the main current connected to the transistor 56 and the second switching element flows. Since the conductor foil is covered without any gap and radiation noise leaking from the gap between the cooling fins is eliminated, the effect of reducing the radiation noise generated when the reverse conducting transistor 59 and the transistor 56 are turned on and off can be increased. is there.

Further, the transistor 56 having a small loss
Is an insulated package that electrically insulates the semiconductor portion from the cooling fins 65, and the non-conductive package 59 in which a large loss of the reverse conducting transistor 59 is electrically insulated from the specific electrode of the semiconductor portion and the cooling fins. Since the non-insulated transistor 56 is fixed to the cooling fan side of the insulated reverse conduction transistor 59 in the form of an insulation type package, the thermal resistance between the semiconductor portion and the case of the reverse conduction transistor 59 which causes a large loss can be reduced. , Heat radiation to the cooling fins 65 is large,
By increasing the cooling effect of the semiconductor part and arranging it downstream of the cooling air, the thermal effect on the case temperature of the insulating transistor 65 can be reduced. On the other hand, by reducing the loss of the insulating transistor 56 in which the thermal resistance between the semiconductor portion and the case becomes large, the temperature difference between the semiconductor portion and the case is reduced, and the transistor is arranged on the cooling fan side (upwind). Since the heat effect from the heat generated by the transistor, in which the amount of heat dissipated to the cooling fin is large, is reduced, the rise in the case temperature of the transistor 56 is minimized, and the rise in the temperature of the semiconductor portion is suppressed. In addition, the semiconductor device of the second switching element has an effect that the temperature rise of each semiconductor portion can be suppressed in a well-balanced manner and can be cooled.

[0062]

As described above, according to the first aspect of the present invention, the thermal resistance between the semiconductor part of the switching element and the temperature sensing part of the temperature sensing element is minimized in the heat conduction path, and the switching element Thus, it is possible to provide an inexpensive induction heating cooker capable of detecting a rapid rise in temperature with high sensitivity and capable of performing accurate output control in response to an abnormality in a cooling system or an element.

According to the second aspect of the present invention, the thermal resistance between the low-potential terminal of the switching element and the temperature-sensitive element can be further reduced with a simple configuration, and the rapid temperature rise of the switching element can be prevented. The effect is obtained that an inexpensive induction heating cooker that can be detected with good responsiveness can be provided.

According to the third aspect of the present invention, the heat generated at the low potential side terminal portion of the switching element through which the main current flows is corrected by the amount of heat lost by the cooling air or the heat radiated from the printed wiring board. Since the amount of heat transmitted to the element is increased, the temperature-sensitive element can detect an abrupt temperature rise of the semiconductor portion of the switching element with higher sensitivity, and can provide an induction heating cooker capable of controlling the output with high accuracy. Can be

According to the fourth aspect of the present invention, a small-sized induction heating cooking with less radiation noise generated when a plurality of switching elements constituting the frequency conversion device having different potentials are alternately turned on and off. The effect that a container can be provided is obtained.

According to the fifth aspect of the present invention, abnormal heat generation of the semiconductor portions of a plurality of switching elements having different potentials constituting the frequency converter can be detected with a single temperature-sensitive element and with a simple configuration. The effect is obtained that it is possible to provide an induction heating cooker that is highly reliable and has less radiation noise generated when the switching elements are alternately turned on and off.

According to the invention of claim 6, a plurality of switching elements having different potentials constituting the frequency conversion device are cooled in a well-balanced manner by a single cooling fin, and are inexpensive, small, and small inducing radiation noise. The effect that a cooking device can be provided is obtained.

[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 perspective view of the vicinity of a switching element of the induction heating cooker.

FIG. 3 is a sectional view showing the vicinity of a switching element of the induction heating cooker.

FIG. 4 is a sectional view showing the vicinity of another switching element of the induction heating cooker;

FIG. 5 is a circuit block diagram of an induction heating cooker according to a second embodiment of the present invention.

FIG. 6 is a plan view near the switching element of the induction heating cooker.

FIG. 7 is a sectional view of a cooling fin of the induction heating cooker.

FIG. 8 is a circuit block diagram of a conventional induction heating cooker.

FIG. 9 is a perspective view showing the vicinity of a switching element of a conventional induction heating cooker.

[Explanation of symbols]

Reference Signs List 25 reverse conducting transistor (switching element) 25c semiconductor section 26 heating coil 28 control circuit (control section) 31 thermistor (thermosensitive element) 31a, 31b copper foil pattern (conductor foil) 31c, 31d terminal section of thermistor (thermosensitive element) 32 Cooling fin 33 Printed wiring board 37 Emitter terminal (low potential side terminal through which main current flows) 37b, 37c Copper foil pattern (conductor foil) 39 Gate terminal (low potential side terminal) 42 Adhesive agent 56 Transistor (second switching element) 57) heating coil 59 reverse conducting transistor (first switching element) 61 control circuit (control unit) 62 thermistor (temperature sensing element) 62a, 62b, 66b, 67b, 68b copper foil pattern (conductor foil) 64 printed wiring board 65 Cooling fin 66 Emitter terminal (low potential side terminal where main current flows) 6 Gate terminal (low potential side terminal)

Claims (6)

[Claims] 1. A heating coil, and a switching element having a case part formed by molding a semiconductor part made of resin fixed to cooling fins and having terminals soldered to connection lines formed of conductive foil of a printed wiring board. A temperature-sensitive element that is thermally coupled to a semiconductor portion of the switching element, and the control content is changed in accordance with a detection result of the temperature-sensitive element. A frequency converter having a control unit for controlling on / off and generating a high-frequency current in the heating coil is provided, and thermal coupling between the temperature-sensitive element and the semiconductor unit of the switching element is performed by connecting a low-potential side terminal of the switching element to the low-potential side terminal of the switching element. The temperature sensing element is disposed on the printed wiring board so as to be used as a main heat conduction path, and the terminal portion of the temperature sensing element is connected to the printed wiring board. The induction heating cooker is configured to be connected to the conductor foil of the printed wiring board by soldering from the conductor foil side without penetrating through. 2. The induction heating according to claim 1, wherein the temperature-sensitive element is disposed opposite to the conductor foil extending from the low-potential side terminal of the switching element and the solder connection portion of the conductor foil via an insulating adhesive. Cooking device. 3. The temperature sensing element is disposed such that thermal coupling between the temperature sensing element and the semiconductor portion of the switching element is performed using a low potential side terminal of the switching element through which a main current flows as a main heat conduction path. The induction heating cooker according to claim 1 or 2, wherein 4. A high-potential side on which a heating coil and a case portion formed by molding a semiconductor portion with a resin are fixed to cooling fins and terminals are connected by soldering to connection lines formed of conductive foil of the printed wiring board. A second switching element and a first switching element on the low potential side, and a frequency conversion device that alternately conducts the first switching element and the second switching element to generate a high-frequency current in the heating coil, The first switching element and the second switching element are fixed to the same cooling fin, and a space between conductor foils connected to both terminals of the first switching element through which a main current flows, and a main switching element of the second switching element. An induction heating cooker in which a space between conductor foils connected between terminals through which current flows is simultaneously covered with the cooling fins. 5. A second high-potential side in which a case portion formed by molding a semiconductor portion with a resin is fixed to cooling fins and terminals are soldered to connection lines formed of conductive foil of the printed wiring board. A switching element, a first switching element on a low potential side, a temperature-sensitive element thermally coupled to a semiconductor portion of the first switching element, and control contents changed according to a detection result of the temperature-sensitive element, and A control unit that controls on / off of the first switching element and the second switching element by setting a low potential side terminal of the switching element as a common potential, and alternately conducts the first switching element and the second switching element; And a frequency converter for generating a high-frequency current in the heating coil. The first switching element and the second switching element are fixed to the same cooling fin. The first switching element and the second
To simultaneously cover the space between the conductor foils of the printed wiring board through which the main current flows, which is connected to the switching element, and the thermal coupling between the temperature-sensitive element and the semiconductor portion of the first switching element is the first. 5. The structure according to claim 1, wherein said temperature sensing element is arranged on said printed wiring board so that a low potential side terminal of a switching element is used as a main heat conduction path.
The induction heating cooker according to any one of the above. 6. An insulated package including a cooling fan that blows air to the cooling fins, and electrically insulates the semiconductor portion and the cooling fins from the smaller loss of the first switching element and the second switching element. In addition, the non-insulating type package in which the specific electrode of the semiconductor portion and the cooling fin are electrically non-insulated is used for the larger loss, and the switching element of the non-insulating type package is switched to the switching of the insulating type package. The induction heating cooker according to claim 4 or 5, wherein the induction heating cooker is fixed to the cooling fan side of the element.