JP3567145B2 - Induction heating rice cooker - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an induction heating rice cooker.
[0002]
[Prior art]
Conventionally, in an induction heating rice cooker, a high frequency current is supplied from an inverter power supply circuit to an IH coil by controlling the ON / OFF timing of an IGBT by an IH control circuit based on a control signal from a microcomputer. Is induction-heated. An input port of the IH control circuit is connected to an inverter output line of an inverter power supply circuit, and a voltage at each part is detected and used for IGBT switching control by the IH control circuit. Further, the standby voltage is applied to the IH control circuit from the power supply even when the IH coil is not energized. Thus, it is possible to start the induction heating by supplying the high frequency current to the IH coil in a short time from the state where the induction heating is not performed.
[0003]
By the way, various proposals have been made to reduce standby power consumed by the IH control circuit and the like. For example, Japanese Patent Application Laid-Open No. H11-318700 discloses a configuration in which when power supply to a rice cooker is not necessary, a commercial power supply and a rice cooker are separated by a power supply switching unit.
[0004]
[Problems to be solved by the invention]
However, if an attempt is made to reduce the standby power in the IH control circuit, the voltage value on the inverter output line side will increase, and a current flowing through the IH control circuit will be generated, possibly leading to damage.
[0005]
Therefore, an object of the present invention is to provide an induction heating rice cooker that can prevent reverse current and appropriately prevent breakage even when the standby power of the IH control circuit is reduced. I do.
[0006]
[Means for Solving the Problems]
According to the present invention, as a means for solving the above problems, a high frequency current is supplied from an inverter power supply circuit to an IH coil by controlling the ON / OFF timing of an IGBT by an IH control circuit based on a control signal from a microcomputer. In the induction heating type rice cooker that supplies and heats the inner pot by induction,
An inverter output line and a standby voltage output line of the inverter power supply circuit are connected to the IH control circuit, respectively.
When reducing the standby voltage in the IH control circuit, a Schottky barrier diode for preventing a current flowing from the inverter output line to the standby voltage line via the IH control circuit is installed, and the inverter output line and the standby voltage It is designed to be connected to an output line.
[0007]
With this configuration, even if the standby power in the IH control circuit is reduced and the voltage on the inverter output line side is increased, the Schottky barrier diode blocks the current flowing through the IH control circuit. Damage can be prevented.
[0008]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments according to the present invention will be described with reference to the accompanying drawings.
[0009]
FIG. 1 shows a circuit configuration for controlling energization of an induction heating coil (IH coil) 3 of the induction heating rice cooker according to the present embodiment.
[0010]
In this circuit, electric power from an AC power supply 1 is supplied to an IH coil 3 via an inverter power supply circuit 2 and supplied to a control circuit 5 via a rectifier circuit 4.
[0011]
A capacitor C1 is connected in parallel to the IH coil 3, and a noise removing coil I and a capacitor C2 are connected between the IH coil 3 and the inverter power supply circuit 2. The IH coil 3 is supplied with a high-frequency current by switching an insulated gate bipolar transistor (IGBT) 6 and inductively heats the inner pot 7.
[0012]
The control circuit 5 includes a voltage control circuit 8, an IH control circuit 9, and a microcomputer 10. The IH control circuit 9 is provided on a first substrate 11, and the voltage control circuit 8 and the microcomputer 10 are provided on a second substrate 12. The first substrate 11 and the second substrate 12 are connected via a relay line 13.
[0013]
The IH control circuit 9 of the first substrate 11 switches the IGBT 6 based on a control signal from the microcomputer 10. Here, the IH control circuit 9 is generally composed of a plurality of comparators and a semiconductor IC (control IC) including these comparators. The control IC includes input ports p1 to p3 that use the output line of the inverter and the power supply line as input signals or the power supply line p4 of the control IC. Inverter output lines I1 to I3 are connected to the input ports p1 to p3, respectively. That is, the first input port p1 has a divided voltage of the resistors R1 and R2 connected between the IH coil 3 and the IGBT 6, and the second input port has a resistor R3 connected between the coil I and the IH coil 3. The divided voltage of R4 and the divided voltage of the resistors R5 and R6 connected between the inverter power supply circuit 2 and the coil I are input to the third input port, respectively. Schottky barrier diodes D1 to D3 are connected between the inverter output lines I1 to I3 and the standby voltage output lines, respectively. A Schottky barrier diode refers to a diode that uses a function (Schottky barrier) of blocking a reverse voltage at a contact surface between a metal and a semiconductor by directly attaching an electrode (Schottky gate) to an N-type semiconductor. These Schottky barrier diodes D1 to D3 cut off the standby voltage to the IH control circuit 9, so that even if the voltage on the inverter output lines I1 to I3 side becomes higher than the input ports p1 to p3, the IH control circuit No reverse current flows into 9. Further, the power input port p4, standby voltage V _CC output from the voltage control circuit 8 via a standby voltage output line I4 is input.
[0014]
The voltage control circuit 8 of the second substrate 12 includes a transistor Tr and resistors R7 and R8. The emitter of the transistor Tr is connected to the microcomputer 10, and can directly apply the output voltage _VDD from the rectifier circuit 4. Further, the collector of the transistor Tr is connected to the IH control circuit 9 via the standby voltage output line I4, and can apply the output voltage _VCC . Further, the divided voltage of the resistors R1 and R2 is inputted to the base of the transistor Tr, and the microcomputer 10 is connected to the microcomputer 10 via these resistors R1 and R2. Therefore, based on a control signal from the microcomputer 10, the transistor Tr is turned on and off, and the standby voltage _VCC output to the IH control circuit 9 is turned on and off.
[0015]
The microcomputer 10 of the second substrate 12 controls the high-frequency current supplied to the IH coil 3 by outputting a control signal to the IH control circuit 9 and adjusting the switching timing of the IGBT 6. Thereby, appropriate rice cooking and heat retention are possible. Further, the microcomputer 10 outputs a control signal to the voltage control circuit 8 and controls on / off of the standby voltage applied to the IH control circuit 9. This makes it possible to suppress wasteful consumption of standby power.
[0016]
In addition to the AC power supply 1 of AC100 (V), a sub-heater 14 and a temperature fuse 15 are connected to the first substrate 11, and the fan 16 and the temperature sensor 17, which are powered by DC low voltage, are connected to the second substrate 12. It is connected to the. That is, by supplying power to each substrate separately for AC and DC, it is possible to make each member less susceptible to external noise and conductive noise. In addition, since a power supply line between the substrates is not required, the number of relay lines 13 can be reduced.
[0017]
Next, the operation of the induction heating rice cooker provided with the circuit having the above configuration will be described.
[0018]
In the induction heating type rice cooker, after connection to the AC power supply 1, processing is performed in accordance with the cancellation mode, the reserved rice cooking mode, the rice cooking mode, and the heat retention mode.
[0019]
In the cancellation mode before the start of rice cooking, the microcomputer 10 outputs a control signal to the voltage control circuit 8 to turn off the transistor Tr, so that the standby voltage in the IH control circuit 9 is output to the _IO output (for example, 0 (V )). The reserved rice cooking mode is processed only when the reserved rice cooking switch is operated and the rice cook start time is input. Similarly, in the reserved rice cooking mode, the standby voltage in the IH control circuit 9 is used as the _IO output. In either the cancellation mode or the reserved rice cooking mode, the voltage value on the inverter output line side becomes larger than the voltage value at each of the input ports p1 to p3 of the IH control circuit 9, but is connected to the power input port. The standby voltage output line is an _IO output. For this reason, the voltage value of each input port drops to 0.2 to 0.4 (V) by the function of the Schottky barrier diode, and it is possible to prevent the reverse current from flowing into the IH control circuit 9. Therefore, it is possible to reliably prevent the IH control circuit 9 from being damaged. In the rice cooking mode, energization of the IH coil 3 is started when a rice cooking switch (not shown) is operated or when a rice cooking start time is reached by operating a reserved rice cooking switch (not shown). In the warming mode, power is supplied to the IH coil 3 as appropriate, and the temperature of the cooked rice is adjusted to a constant temperature.
[0020]
【The invention's effect】
As is apparent from the above description, according to the present invention, the Schottky barrier diode is connected in the middle of the inverter output line connected to the input port of the IH control circuit. Can be prevented, the current flowing into the IH control circuit can be prevented, and the damage can be accurately prevented.
[Brief description of the drawings]
FIG. 1 is a circuit diagram showing a configuration of an electric circuit employed in an induction heating rice cooker according to the present embodiment.
[Explanation of symbols]
2 ... Inverter power supply circuit 3 ... IH coil 4 ... Rectifier circuit 5 ... Control circuit 6 ... IGBT
8 Voltage control circuit 9 IH control circuit 10 Microcomputer 11 First substrate 12 Second substrate 13 Relay wire 14 Subheater 15 Temperature fuse 16 Fan 17 Temperature sensors p1 to p3 Input ports I1 to I3 ... Inverter output line I4 ... Stand-by voltage output lines D1 to D3 ... Schottky barrier diode

Claims (1)

Induction heating in which the IH control circuit controls the ON / OFF timing of the IGBT based on a control signal from the microcomputer, thereby supplying a high-frequency current from the inverter power supply circuit to the IH coil and inductively heating the inner pot. In a rice cooker,
An inverter output line and a standby voltage output line of the inverter power supply circuit are connected to the IH control circuit, respectively.
When reducing the standby voltage in the IH control circuit, a Schottky barrier diode for preventing a current flowing from the inverter output line to the standby voltage line via the IH control circuit is installed, and the inverter output line and the standby voltage An induction heating rice cooker characterized by being connected to an output line.

Images