KR100938861B1 - Limit circuit of Induction heating cooker and Induction heating cooker comprsing thereof - Google Patents

Abstract

The present invention relates to an induction heating cooking appliance comprising a protection circuit and a protection circuit of an induction heating cooking appliance.

The present invention is to ensure that the operation of the induction heating cooker can be stably performed through the operation of the inverter circuit when the induction heating cooker is used in a no-load state or an improper container before operation, and in an eccentric or no-load state of the container during operation. It provides an induction heating cooking apparatus comprising a protection circuit and a protection circuit of the induction heating cooking appliance.

Induction cooker, eccentric, no load

Description

Induction heating cooker comprising a protection circuit and a protection circuit of the induction heating cooker {Limit circuit of Induction heating cooker and Induction heating cooker comprsing}

The present invention relates to an induction heating cooking apparatus, which induces heating of a cooking apparatus using an induction heating method and prevents the induction heating cooking apparatus from operating in an eccentric or no load state, thereby preventing the stability of the induction heating cooking apparatus. It relates to an induction heating cooking appliance comprising a protection circuit and a protection circuit of a heating cooker.

Induction heating cookers, unlike gas cookers, do not use flames and have no risk of gas leakage. They are excellent in stability, and generally have a flat, sleek shape, which is superior in aesthetics, due to high efficiency and ease of use. Demand is rising

1 is a view illustrating a state in which a cooking vessel is eccentrically placed on a general induction heating cooking appliance.

As shown in FIG. 1, the induction heating device includes a cook zone 2 in which the main body 1 and the container 3 are seated, and a control panel 4 for allowing a user to set an operation of the induction heating device. .

The induction heating method used in the induction heating device is a method of providing cooking heat to the container using an inverter circuit for generating a high frequency current. Due to the magnetic field generated by supplying a high frequency current to the working coil formed on the inner lower portion of the cook zone 2, an induced current is generated in the container made of a magnetic material, which is generated by the resistance of the container itself and the induced current. It means the manner in which the container is heated by the heat amount. Induction heating electric cookers, cooktop (Cooktop) and a slow cooker (Slow cooker) is used as a typical induction heating type cooking apparatus.

In a typical induction heating cooking apparatus, when the container is eccentrically settled out of the area of the cook zone as shown in FIG. 1 and the non-load state or the specific resistance such as aluminum is settled out of the area of the cook zone 3 completely In the case of a container using a small metal material, the output decreases. Therefore, a high output high frequency current flows inside the inverter circuit to compensate for this.

That is, in the eccentric mode, overcurrent flows than in the normal driving state. Accordingly, there is a problem that an overload or malfunction occurs in the inverter circuit due to the overcurrent, which may lead to a decrease in reliability and stability of the product.

Therefore, the present invention has been proposed to solve the above problems, the present invention is to provide a protective circuit of the induction heating cooking apparatus and induction heating cooking apparatus which can prevent the generation of overcurrent in the eccentric and no load state of the container. The purpose.

The protection circuit of the induction heating cooking apparatus according to the present invention for achieving the above object is a reference voltage for determining whether the resonant current supplied to the working coil is overloaded, and the limit voltage having three or more different magnitudes is measured. Being a node; A start limiting unit and an intermediate output limiting unit connected to the node such that the level of the limiting voltage is differently output depending on whether a short circuit exists; and a limiting voltage measured at the node and a resonance current supplied to the working coil. And a comparison unit for comparing the voltage levels.

Induction heating cooking apparatus according to the present invention for achieving the above object is a power supply for supplying power to the circuit of the induction heating cooking apparatus; An inverter unit performing a switching operation on the power supplied from the power supply unit to apply a resonant current to the working coil; An inverter part driving circuit for controlling driving of the inverter part; A resonance voltage detector for outputting a voltage signal with respect to the resonance current supplied to the working coil; And a protection circuit that determines whether an overload occurs due to a resonance current supplied to the working coil.

Therefore, the induction heating cooking apparatus including the protection circuit and the protection circuit of the induction heating cooking apparatus according to the present invention is determined whether the operation according to the container eccentricity and the material of the container in the start section and the container eccentric state and no load in the intermediate output section Operation of the induction heating cooker can be stably performed by blocking the operation of the inverter circuit in the state.

In addition, the induction heating cooking apparatus including the protection circuit and the protection circuit of the induction heating cooking apparatus according to the present invention can prevent the deterioration of the efficiency of the induction heating cooking apparatus due to eccentricity and no load through the prevention of the occurrence of overcurrent.

Referring to the accompanying drawings, the induction heating cooking apparatus and the protection circuit of the induction heating cooking apparatus according to the present invention will be described in detail as follows.

2 is a circuit diagram showing the configuration of an induction heating cooking apparatus according to an embodiment of the present invention.

In the induction heating cooking apparatus, the inverter circuit includes a switch element therein and is switched by a microcomputer (8) for outputting a control signal in accordance with a cooking instruction including a heating temperature, a heating time, a cooking method, and the like operated by a user. It is a circuit for applying a power to the coil to drive the container seated on the coil to heat.

Here, the vessel containing the food becomes a heating load, and the inverter circuit eliminates the heating load by applying power to the coil.

In the induction heating cooker, the position where the wound coil is provided is indicated on the top of the induction heating cooker, which is referred to as a cook zone 2 (see FIG. 1). The cooking vessel is mounted so that the cook zone 2 does not deviate from the marked area, and a heating operation is performed. At this time, it is called an eccentric state that the container is out of the cook zone 2. In addition, the container is completely out of the cook zone 2 is called a no-load state.

The circuit of the induction heating cooking apparatus according to the present invention is largely the power supply unit 9, the inverter unit 5, the inverter unit driving circuit 6, the protection circuit 30, the resonance voltage detection unit 7, the working coil 20 ) And the microcomputer 8.

The power supply unit 9 converts normal AC power supplied to the home into DC power through a rectification and filter unit not shown in the drawing, and supplies the same to the inverter unit 5.

The inverter unit 5 includes an insulated gate bipolar transistor (IGBT) element, that is, an insulated gate bipolar transistor, and supplies a high frequency current to the working coil 20 through a high speed switching operation of the IGBT element.

The inverter unit driving circuit 6 drives the operation of the inverter unit 5 and serves to maintain the constant output of the inverter unit 5.

In detail, the inverter unit driving circuit 6 adjusts the duty time of the on / off of the inverter unit 5 with respect to a constant current value at a value equal to or less than a predetermined output relative to the maximum output. To adjust the output value applied to the working coil 20.

And, at a value equal to or greater than a predetermined output relative to the maximum output, the output value applied to the working coil 20 is adjusted by adjusting the current value applied to the inverter unit 5.

In addition, the inverter driving circuit 6 is connected to the microcomputer 8 to drive a process for compensating for the output value less than the value set by the user due to a predetermined event when the induction heating cooking apparatus is driven. Formed.

The resonance voltage detector 7 measures a voltage value of the resonance current applied to the working coil 20 and applies a signal related to the measured resonance current voltage to the protection circuit 30.

The protection circuit 30 compares the resonance current voltage of the working coil 20 with a predetermined limit voltage, and when the resonance current voltage exceeds the limit voltage, sends a signal to the inverter unit driving circuit 6. To block the operation of the inverter drive circuit 6 to protect the inverter circuit. Detailed description of the protection circuit 30 will be described later.

3 is a circuit diagram illustrating a protection circuit of an induction heating cooker according to an embodiment of the present invention.

According to the exemplary embodiment of the present invention, the operation section of the protection circuit may be divided into first to third sections according to the voltage level applied to the working coil 20, that is, the magnitude of the limit voltage. That is, the first section is a section in which voltage is supplied to the working coil to determine whether the container is eccentric and the material of the container, and the second section and the third section are the limits for preventing overload due to the container eccentricity. It can be said to be divided according to the level of the voltage.

In the following description, the case where the level of the limit voltage in the third section is greater than the limit voltage in the second section will be described as an embodiment, and the second section is referred to as an intermediate output section. The third section will be referred to as the maximum output section. In addition, the first section will be referred to as a start section.

That is, in the following description, when the first to third sections are sequentially performed, the protection circuit is provided so that the level of the limit voltage gradually increases in each of the sections.

Referring to FIG. 3, the protection circuit 30 according to the present invention includes a start limiting unit 31, a comparing unit 32, an intermediate output limiting unit 33, a DC converting unit 34, a filter unit 35, and the like. Insulation portion 36 is included.

In detail, the start limiting unit 31 receives a signal from the microcomputer 8 and the power supply unit 9 to operate in the start section of the inverter circuit, and the operation is blocked when the start section passes.

Here, an input voltage Vac output from the power supply unit 9 and a resonance current voltage Vcurrent applied to the working coil 20 are applied to an input terminal of the start limiter 31.

The voltage at the output terminal of the start limiter 31 is a limit voltage (Vlimit), which is a kind of reference voltage for determining whether the container is eccentric or the material of the container.

Therefore, the protection circuit 30 compares the magnitude of the voltage output from the resonance voltage sensing unit 7 with the magnitude of the measured limit voltage, and sends the resulting signal to the inverter unit driving circuit 6. The inverter unit driving circuit 6 controls the operation of the inverter unit 5 using the resultant signal, which will be described in detail later.

The start limiter 31 may include a first comparator 312 receiving the input voltage Vac and a resonance current voltage Vcurrent, and a diode or a resistor connected to an output terminal of the first comparator 312. It may include.

The start limiting unit 31 is connected or short-circuited with the intermediate output limiting unit 33 or the comparing unit 32 by the first comparator 312 therein. That is, the first comparator 312 allows the start limiting unit 31 to be driven in the start section before the inverter circuit performs the normal operation, and after the start section ends, the normal operation section. It is provided to cut off the driving of the start limiting part 31 when entering.

The start section is a step of determining the material of the cooking vessel and whether the cooking vessel is eccentricity before the inverter circuit enters a normal operation section in which the cooking vessel is heated to perform the cooking operation. When the cooking vessel is eccentric or when the cooking vessel is made of a material in which an induction current flows excessively, such as aluminum, the resonance current applied to the working coil 20 may flow with an overcurrent. In order to prevent this, it is provided before the normal operation period.

The intermediate output limiting section 33 is provided between the start limiting section 31 and the comparing section 32, so that the eccentricity of the container in the normal operation section of cooking vessel heating, the drive unit drive circuit (6) To judge.

The start limiter 31 and the intermediate output limiter 33 are connected to the comparator 32 and a single node, and the voltage of the node is the limit voltage Vlimint. do.

As a result, the node is connected to the negative input terminal of the second comparator 322 provided in the comparator 32.

The intermediate output limiter 33 receives a control signal (predetermined voltage) applied from the microcomputer 8 and a voltage of 12 V as an input, and as a result of comparison, a short or short circuit to the node. (Open) is made.

For reference, as a result of the operation of the third comparator 332 in the intermediate output limiting unit 33, the limit in the intermediate output section in FIG. 4 which will be described later when the connection with the node is maintained. The level of the voltage Vlimit is maintained.

The signal from the microcomputer 8 is applied to the (+) terminal of the third comparator 332 in the intermediate output limiting unit 33, and the start section and the 12-V input signal are received to the (-) terminal. Perform the operation in the intermediate output section.

The intermediate output section is provided between the start section and the maximum output section in which the limit voltage Vlimit is maximum, and the limit voltage Vlimit in the intermediate output section is the limiting voltage in the start section. Vlimit) and the limit voltage Vlimit in the maximum output section.

However, in the embodiment according to the present invention, the intermediate output section is set based on one voltage, but the idea according to the present invention is not limited by the above embodiment and the intermediate output section is divided into a plurality of sections based on the plurality of voltages. Embodiments of dividing and controlling the inverter circuit may also be proposed.

The insulating part 36, the filter part 35, and the DC converting part 34 may be provided between the intermediate output limiting part 33 and the microcomputer 8.

The insulating part 36 connected to the intermediate output limiting part 33 is to be insulated so that a signal applied from the microcomputer 8 is not shorted.

One end of the photocoupler of the insulation unit 36 is connected to the microcomputer 8, and the other end thereof is connected to an input voltage of 12V. If there is a signal from the microcomputer 8, a signal is applied to the intermediate output limiting unit 33. If there is no signal from the microcomputer 8, the signal applied to the intermediate output limiting unit 33 is removed. .

A low pass filter is applied to the filter unit 35 to remove noise of a high frequency component included in the signal applied from the microcomputer 8.

That is, when the noise is included in the signal by a predetermined event in the induction heating cooker, the noise flows through the grounded capacitor, and the normal signal is applied to the intermediate output limiter 33. .

In addition, the DC converting unit 34 converts the signal applied from the microcomputer 8 to provide the signal to the intermediate output limiting unit 33.

The protection circuit operates by being divided into the start section, the intermediate output section, and the maximum output section, as described above for each of the sections.

In addition, the resonant current voltage Vcurrent in the eccentric mode is formed to increase as much as a constant value compared to the resonant current voltage Vcurrent in the normal mode at the same output. The limit voltage Vlimit according to the embodiment of the present invention Is formed to have different values in the start section, the intermediate output section and the maximum output section, respectively.

In the eccentric mode, since the area in which the container is in contact with the cook zone 2, that is, the area in which the resonant current flows in the container is reduced, more resonant current should be applied than in the normal mode of the same output. Because.

Here, the limit voltage Vlimit represents a measured voltage at a single node connecting the start limiter 31, the intermediate output limiter 33, and the comparator 32, and the start limiter 31. ) And the magnitude of the limit voltage Vlimit vary depending on whether the intermediate output limiting unit 33 is shorted to the node. This will be described later with reference to FIG. 4.

4 is a graph showing a change in the voltage applied amount according to the protection circuit of the induction heating cooking apparatus according to the embodiment of the present invention.

FIG. 4 shows three levels of limit voltages proposed to prevent overload of the inverter circuit according to the eccentricity of the cooking vessel. As described above, the above limitations in the start section, the intermediate output section and the maximum output section are shown. The level of the voltage Vlimit is formed differently.

The limit voltage Vlimit in the maximum output section is the largest, and the limit voltage Vlimit in the intermediate output section is greater than the limit voltage Vlimit in the start section.

Here, the limit voltage (Vlimit) is set differently for each of the three sections, which is performed by the operation of the start limiting unit 31, the intermediate output limiting unit 33 and the comparison unit 32.

In detail, the start limiter 31 and the intermediate output limiter 33 serve as a voltage devider for the node at the measurement target point of the limit voltage Vlimit, and the start limiter. (31) and the comparators 312 and 332 provided in the intermediate output limiting section 33 are connected or shorted to the node.

When both the start limiting section 31 and the intermediate output limiting section 33 are operated (when all are shorted to the node where the limit voltage Vlimit is formed), the The limit voltage (Vlimit) level is output.

That is, in the start section, since the start limiter 31 and the intermediate output limiter 33 are both connected to the node, resistors 311, 321, and 33 are connected to each other in parallel to the node.

In particular, the equal resistance values 311 / / 321 / / 331 of the resistors connected in parallel are short-circuited due to the operation of the start limiting unit 31 and the intermediate output limiting unit 33 blocked (the start limiting unit ( 31) and both of the comparators 312 and 332 of the intermediate output limiting unit 33 have a relatively small value compared to the maximum output section in FIG. 4 when the node and the short circuit are open. This is because in the maximum output section, only the resistor 321 in the comparator 32 is connected to the node as the start limiter 31 and the intermediate output limiter 33 are shorted.

Thus, the level of the limit voltage Vlimit (measurement voltage at the node) in the maximum output section is formed higher than the level of the limit voltage Vlimit in the start section.

In addition, in the intermediate output section, the operation of the start limiting unit 31 is interrupted, and the intermediate output limiting unit 33 is connected to the node where the limit voltage Vlimit is detected, and the equal resistance value 321 is corresponding thereto. // 331 is a value between the equal resistance 311 / / 321 / / 33 in the start section and the value of the resistance 321 in the maximum output section.

As a result, the limit voltage Vlimit is increased in the level of the voltage in the order of the start section, the intermediate output section and the maximum output section.

On the other hand, Figure 4 is a graph of the resonant current voltage (Vcurrent) in the eccentric mode and the normal mode according to the eccentricity of the cooking vessel, the eccentric mode is the user of the container (during operation of the induction heating cooker) In FIG. 1 to 3), the container 3 is operated so as to be eccentrically away from the region of the cook zone (2 in FIG. 1), in which case an overload of the inverter circuit may occur.

When the said container 3 is eccentric, the area | region which the said container 3 contacts with the area | region of the cook zone 2 becomes small, and the fall of an output arises. In this case, the inverter driving circuit 6 applies more resonance current to the working coil 20 than the normal mode in order to compensate for a decrease in output. That is, as shown in FIG. 4, the level of the resonance current voltage Vcurrent in the eccentric mode is higher than the level of the resonance current voltage Vcurrent in the normal mode.

The limit voltage Vlimit by the limit circuit 30 according to the present invention has a different value in the start section, the intermediate output section, and the maximum output section, respectively, and the resonance current voltage Vcurrent in the normal mode. And the resonance current voltage Vcurrent in the eccentric mode.

Therefore, the limit circuit 30 is provided to block the operation of the eccentric mode in which the resonance current voltage Vcurrent exceeds the limit voltage Vlimit based on the limit voltage Vlimit.

In detail, in the protection circuit of the present invention, the comparator 32 allows the resonance current voltage Vcurrent to be applied to the (+) terminal of the second comparator 321, and the limit voltage (Vlimit) to the (-) terminal. ) Is applied.

The comparison unit 32 has a high value when the resonance current voltage Vcurrent is greater than the limit voltage Vlimit by comparing the resonance current voltage Vcurrent with the limit voltage Vlimit. An output signal Vout is applied to the inverter section driving circuit 6, and the inverter section driving circuit 6 is cut off. Through the above process, overcurrent is prevented from occurring in the inverter circuit due to eccentricity and no load of the container.

On the contrary, when the resonant current voltage Vcurrent is smaller than the limit voltage Vlimit, an output signal Vout having a low value is applied to the inverter part driving circuit 6 so that the inverter part driving circuit ( 6) continues to operate.

Although the present invention has been described with reference to the embodiments shown in the drawings, this is merely exemplary, and it will be understood by those skilled in the art that various modifications and equivalent other embodiments are possible. . Therefore, the true technical protection scope of the present invention will be defined by the technical spirit of the appended claims.

1 is a view illustrating a state in which a cooking vessel is eccentrically placed on a general induction heating cooking appliance.

2 is a circuit diagram showing the configuration of an induction heating cooking apparatus according to an embodiment of the present invention.

3 is a circuit diagram illustrating a protection circuit of an induction heating cooker according to an embodiment of the present invention.

4 is a graph showing a change in the voltage applied amount according to the protection circuit of the induction heating cooking apparatus according to the embodiment of the present invention.

Claims (6)

In the protection circuit to prevent overload caused by the eccentricity of the container in the induction heating cooker, A reference voltage for determining whether an overload of a resonance current supplied to a working coil is generated, the node having three or more different limiting voltages measured therein; A start limiting unit and an intermediate output limiting unit connected to the node so that the level of the limiting voltage is output differently from each other according to whether a short circuit occurs; and And a comparison unit for comparing the voltage level of the limit voltage measured at the node and the resonance current supplied to the working coil. The method of claim 1, Each of the start limiting unit and the intermediate output limiting unit is provided with a comparator (Op-amp) for controlling the connection or short-circuit with the node. The method of claim 2, Each of the start limiter, the intermediate output limiter, and the comparer further includes a resistor connected to the node. The protection circuit of the induction heating cooking appliance, characterized in that the magnitude of the limit voltage is formed differently due to the resistance value by the connection and the short circuit of the start limiter and the intermediate output limiter. The method of claim 1, The limit voltage is divided into first to third sections according to the magnitude thereof, The limit voltage is a protection circuit of the induction heating cooking apparatus, characterized in that is formed to gradually increase in the first to third intervals. A power supply unit supplying power to a circuit of the induction heating cooker; An inverter unit performing a switching operation on the power supplied from the power supply unit to apply a resonant current to the working coil; An inverter part driving circuit for controlling driving of the inverter part; A resonance voltage detector for outputting a voltage signal with respect to the resonance current supplied to the working coil; And Induction heating cooking apparatus comprising a; protection circuit of any one of claims 1 to 4 for determining whether the overload caused by the resonance current supplied to the working coil The method of claim 5, wherein The comparison unit includes an induction heating cooking apparatus comprising a comparator (Op-amp) for comparing the voltage output from the resonance voltage detection unit with the magnitude of the limit voltage.

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