JP2000299182A - Induction heating cooker - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the power consumption in an induction heating coil in standby. SOLUTION: This induction heating cooker (a rice cooker 1) comprises a rectifier circuit 12 connected with an ac power source 11, an induction heating coil 4 for induction-heating a container (an inner pot 2) through a non conductive member by carrying high frequency current, a switch element (an IGMT 16) for turning on and off electricity to the induction heating coil, a switch element control circuit (an IGBT control circuit 20) for controlling on and off of the switch element, and a delay circuit 21 for outputting a signal of control timing to the switch element control circuit. A trigger circuit 22 comprising a diode 23 connected with an one end of the induction heating coil and an insulation semiconductor (a photocoupler 25) including a luminescent element (a light emitting diode 26) and a light receiving switch element (a phototransistor 27) is provided to the induction heating cooker, and the trigger circuit detects a potential difference between both ends of the induction heating coil and controls the switch element.

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 such as a hot plate or a rice cooker for reducing power consumption during standby operation.

[0002]

2. Description of the Related Art In an induction heating cooker of this type, an induction heating coil is disposed below a partition member made of a non-conductive material, and a high frequency current is applied to the induction heating coil so that the partition member can be heated. Induction heating is performed on a metal container set on the upper portion to cook food in the container.

[0003] The induction heating coil is connected to an inverter circuit having an IGBT as a switching element, a capacitor and a diode, and a control circuit for turning on and off the supply of a high-frequency current to the induction heating coil. The control circuit compares a voltage between both ends of the induction heating coil and outputs a Hi or Lo signal;
The IGB according to the signal input from this comparator
A delay circuit for outputting a control timing of T and an IGBT control circuit for turning on or off the IGBT according to an input from the delay circuit.

[0004] In the induction heating cooker provided with the control circuit, the delay circuit determines when the potential difference between one end (between the emitter and collector of the IGBT) and the other end of the induction heating coil becomes 0 V by an input from the comparator. And outputs a timing of transmitting an ON signal to the IGBT to the IGBT control circuit with a predetermined delay time from that point. When the IGBT is turned on, a high-frequency current is applied to the induction heating coil, and when the IGBT is turned off, a resonance circuit is formed by the induction heating coil and a capacitor. The voltage gradually increases and then gradually decreases.
As a result, the induction heating coil generates an alternating magnetic field, and the container is induction-heated through the partition member by the alternating magnetic field.

[0005]

However, in the induction heating cooker, the voltage at both ends of the induction heating coil is divided by a comparator and converted into a low voltage.
Since the signal must be transmitted to the delay circuit, there is a problem that the circuit configuration becomes complicated.

[0006] In recent years, there has been an increasing demand for energy saving of electric appliances. However, in the induction heating cooker, since both ends of the induction heating coil are grounded, a small amount of power of about 2 W is consumed even when the induction heating coil is not operated via the control circuit. I have.

Accordingly, an object of the present invention is to provide an induction heating cooker which can prevent power consumption of the induction heating coil during operation standby.

[0008]

In order to solve the above-mentioned problems, an induction heating cooker according to the present invention comprises a rectifier circuit connected to an AC power supply, and a container connected via a non-conductive member by supplying a high-frequency current. An induction heating coil for induction heating, a switching element for turning on / off the energization of the induction heating coil, a switching element control circuit for controlling on / off of the switching element, and a control timing signal to the switching element control circuit In the induction heating cooker provided with a delay circuit that outputs a signal, a diode connected to one end of the induction heating coil, a light emitting element interposed between the diode and the other end of the induction heating coil, and the delay circuit A trigger circuit provided with an insulating semiconductor comprising a light receiving switching element to be connected; By detecting the potential difference between the ends is configured to control the switching element.

According to the induction heating cooker, it is not necessary to divide the voltage at both ends of the induction heating coil and convert it to a low voltage as in the conventional example using a comparator, so that the circuit configuration is simplified. be able to.

In the induction heating cooker, the light receiving switching element is connected to a DC power supply, the delay circuit is connected between the switching elements, the potential difference between both ends of the induction heating coil is easily detected, and the signal is delayed. It is preferable to be able to reliably output to the circuit.

Preferably, when the potential difference between both ends of the induction heating coil becomes 0 or less, the light receiving switching element is turned off. In this way, there is no potential between both ends of the induction heating coil during a standby state such as a warm state or a non-use state. In this operation standby state, the light emitting element of the insulating semiconductor connected via the diode does not emit light. Therefore, the light receiving switching element maintains the off state, and as a result, both ends of the induction heating coil are in a short-circuit state, so that it is possible to prevent the minute power consumption during the standby.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a rice cooker 1 which is an induction heating cooker of the present invention. The rice cooker 1 generally includes an inner pot 2 that is a container for storing food, a main body 3 having a protective frame 3a made of a non-conductive material that houses the inner pot 2, an induction heating coil 4, and an inner pot 2. Temperature sensor 5, lid 6, lid heater 7,
It has a well-known configuration including a temperature sensor 8 for a lid and a circuit board 10.

The circuit board 10, as shown in FIG.
A rectifier circuit 12 composed of a diode bridge connected to an AC power supply 11, a drive circuit 14 for the induction heating coil 4 connected to the rectifier circuit 12, and a microcomputer 13 for operating each drive circuit according to a stored program. ing.

The drive circuit 14 includes a well-known inverter circuit 15 having an IGBT 16 as a switching element, capacitors 17A and 17B and a diode 18,
GBT control circuit 20, delay circuit 21, and trigger circuit 2
2 comprising a control circuit 19 having two.

The IGBT control circuit 20 turns on the IGBT 16 for a predetermined time in accordance with an instruction from a delay circuit 21 which will be described later.
_It boosts _CE .

The delay circuit 21 detects a potential difference between a voltage portion _{VCE at} one end of the inverter circuit 15 and a voltage portion _{VL at the} other end, based on an input voltage from a trigger circuit 22 described later. Then, the voltage section V _CE is boosted and the voltage section V _L
When the potential difference becomes 0 V from the higher voltage state, a signal for turning on the IGBT 16 is output to the IGBT control circuit 20 with a predetermined delay time.

The trigger circuit 22 includes a diode 23 connected to a voltage part V _CE at one end of the induction heating coil 4.
And a resistor 24 connected in series with the diode 23;
A photocoupler 25, which is an insulating semiconductor, is connected between the resistor 24 and the voltage portion _{VL at} the other end of the induction heating coil 4. The photo coupler 25 includes a light emitting diode 26 as a light emitting element and a photo transistor 27 as a light receiving switching element. The light emitting diode 26 has one end connected to the resistor 24 and the other end connected to the voltage unit _VL . The phototransistor 27 has a collector connected to a DC power supply _VDD via a resistor 28, and an emitter grounded. Also,
The delay circuit 21 is connected between the resistor 28 and the collector.

Next, the rice cooker 1 having the drive circuit 14
Will be described. When the user sets the desired amount of rice and the corresponding water in the inner pot 2, stores the inner pot 2 in the protective frame 3 a of the main body 3, and cooks the rice, the microcomputer 13 passes through the delay circuit 21. To transmit an operation instruction to the IGBT control circuit 20.

Then, as shown in FIG. 3, the IGBT control circuit 20 outputs an ON signal (current) to the gate of the IGBT 16 to turn on the IGBT 16. As a result, a high-frequency current is applied to the induction heating coil 4, and the inner pot 2 is induction-heated via the protection frame 3a. And IG
When a predetermined time has elapsed, the BT control circuit 20
The output of the ON signal to T16 is stopped to turn off.

As a result, the voltage of the voltage section V _CE of the inverter circuit 15 gradually rises from 0 V, exceeds the voltage of the voltage section _VL , and then gradually drops to 0 V again.

[0021] Then, the trigger circuit 22, depending on the boosting of the voltage of the voltage unit V _CE, its voltage is towards the voltage of the voltage unit V _CE becomes higher than the voltage of the voltage unit V _L, the voltage unit V
_A current flows through the light emitting diode 26 of the photocoupler 25 via the diode 23 and the resistor 24 connected to _CE , and the light emitting diode 26 emits light. When the light from the light emitting diode 26 is received by the phototransistor 27, the phototransistor 27 is turned on.

On the other hand, when the voltage of the voltage section V _CE falls below the voltage of the voltage section _VL in response to the drop of the voltage, the power supply to the light emitting diode 26 is cut off, and the light emitting diode 26 stops emitting light. Then, the phototransistor 27 is turned off.

The phototransistor 27 is turned off.
The trigger circuit 22 and the delay circuit 21
At point A on the line connecting
Wrong. That is, first, the phototransistor 27
In the off state, the DC power supply V _DDVoltage (5V) is applied
Have been. On the other hand, the phototransistor 27 is turned on.
The DC power supply V_DDPower from the photo tiger
Since it is grounded through transistor 27, the voltage at point A is
0V.

The delay circuit 21 determines when the voltage of the voltage section V _CE falls below the voltage of the voltage section _VL , ie,
The IGBT control circuit 20 has a predetermined delay time from the point when the voltage at the point A changes from 0V to 5V.
To turn on the IGBT 16.

As described above, the delay circuit 21, the IGBT control circuit 20, the inverter circuit 15, and the trigger circuit 22 repeat the respective operations, and
The rice is cooked by inductively heating the inner pot 2 through the.

When the rice-cooking operation is completed and the temperature is maintained, the induction heating coil 4 and the lid heater 7 are operated intermittently. Then, when the user operates the cancel switch, the heat retaining operation is stopped, and the components other than the clock function are in an operation standby state.

In the operation standby state, the inverter circuit 1
There is no potential between the voltage part V _L and the voltage part V _CE in 5. Therefore, the photocoupler 2 in the trigger circuit 22
Since no power is supplied to the light emitting diode 26 of No. 5, the light emitting diode 26 does not emit light, and the phototransistor 27 remains off. As a result, both ends of the induction heating coil 4 are short-circuited, so that it is possible to prevent a small amount of power from being consumed during the operation standby.

The present invention is not limited to the above embodiment. For example, a phototransistor 27 is applied to the trigger circuit 22 as the light-receiving switching element of the insulating semiconductor, but any element that switches by receiving light, such as a photoelectric switch, can be applied.
Further, instead of an insulating semiconductor comprising a light emitting element and a light receiving switching element, any element can be applied as long as it detects a potential difference between one end and the other end of the induction heating coil 4 and switches the switching element by the potential difference. It is.

In the above embodiment, a rice cooker is used as the induction heating cooker, but any other induction heating type electric appliance such as a hot plate can be used.

[0030]

As is apparent from the above description, in the induction heating cooker according to the present invention, a diode connected to one end of the induction heating coil and a diode interposed between the diode and the other end of the induction heating coil are provided. Since a trigger circuit including a light emitting element and an insulated semiconductor including a light receiving switching element is provided, and the trigger circuit detects the potential difference between both ends of the induction heating coil to control the switching element, Unlike the conventional example using a comparator, it is not necessary to divide the voltage at both ends of the induction heating coil and convert it to a low voltage, so that the circuit configuration can be simplified.

Further, since the light receiving switching element is connected to a DC power supply and the delay circuit is connected therebetween, a potential difference between both ends of the induction heating coil is easily detected, and the signal is sent to the delay circuit. It can output reliably and perform switching control.

Further, when the potential difference between both ends of the induction heating coil becomes equal to or less than 0, the light receiving switching element is turned off. There is no potential between both ends. Therefore, since the light emitting element of the trigger circuit does not emit light, the light receiving switching element maintains the off state. As a result, since both ends of the induction heating coil are short-circuited, it is possible to prevent a very small amount of power from being consumed during the operation standby,
Energy saving can be achieved. Also, if a photocoupler is applied as the insulating semiconductor, a trigger circuit can be configured at low cost.

[Brief description of the drawings]

FIG. 1 is a schematic view of an induction heating cooker according to the present invention.

FIG. 2 is a circuit diagram showing a drive circuit of an induction heating coil applied to the induction heating cooker of FIG.

FIG. 3 is a time chart showing operation timing of each component in the drive circuit of FIG. 2;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Induction heating cooker, 2 ... Inner pot, 3 ... Main body, 3a ... Protection frame, 4 ... Induction heating coil, 10 ... Circuit board, 11 ... AC power supply, 12 ... Rectifier circuit, 13 ... Microcomputer, 14 ... Drive circuit , 15 ... Inverter circuit, 16 ... IGBT (switching element), 17A, 17B ... Capacitor, 18 ... Diode, 19 ... Control circuit, 20 ... IGBT control circuit (Switching element control circuit), 21 ... Delay circuit, 22 ... Trigger circuit 23, a diode, 24, a resistor, 25, a photocoupler (insulated semiconductor), 26, a light emitting diode (light emitting element), 27, a phototransistor (light receiving switching element), 28, a resistor.

 ────────────────────────────────────────────────── ─── Continuing from the front page (72) Inventor Atsushi Betsue 1-20-5 Temma, Kita-ku, Osaka-shi, Osaka Elephant-in-Mahobin Co., Ltd. (72) Inventor Fumiaki Murakami 1-chome, Tenma, Kita-ku, Osaka, Osaka No. 20 No. 5 Elephant In-House Co., Ltd. F-term (reference) 3K051 AA02 AC03 AC14 AD07 AD13

Claims (3)

[Claims] 1. A rectifier circuit connected to an AC power supply, an induction heating coil for inductively heating a container through a non-conductive member by applying a high-frequency current, and turning on and off the power supply to the induction heating coil. An induction heating cooker comprising a switching element, a switching element control circuit for controlling on / off of the switching element, and a delay circuit for outputting a control timing signal to the switching element control circuit; one end of the induction heating coil; A trigger circuit including a diode connected to the light-emitting element interposed between the diode and the other end of the induction heating coil and a light-receiving switching element connected to the delay circuit; The switching element is controlled by detecting a potential difference between both ends of the induction heating coil by a trigger circuit. Induction heating cooker according to claim and. 2. The induction heating cooker according to claim 1, wherein the light receiving switching element is connected to a DC power supply, and the delay circuit is connected between the DC power supply and the switching element. 3. The induction heating cooker according to claim 1, wherein the light receiving switching element is turned off when a potential difference between both ends of the induction heating coil becomes 0 or less.