JP2000156284A - High frequency heating device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a high frequency heating device in which a nickel-cadmium storage battery or a nickel-hydrogen storage battery is mounted to make it portable, and in which a battery action (discharge) condition can be determined to protect the battery. SOLUTION: This device is provided with a battery 11, an inverter 12 to convert power of the battery 11, a command part 15 to control action of the inverter 11 and a charging part 14, and an operation part 16 to give action instruction to the command part 15 from the external, and as the command part 15 commands action of the inverter 12 based on a signal from the operation part 16, discharge of battery power is started, while the stop of it is conducted not based on the signal from the operation part 16 but with priority to an action condition of the battery 11.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-frequency heating device using a battery as a power source, and more particularly to preventing overdischarge of the battery.

[0002]

2. Description of the Related Art FIG. 8 is a circuit block diagram showing a configuration of a conventional high-frequency heating device. An AC commercial power supply 1 is converted into a high frequency high voltage by an inverter 12, and a magnetron 13 is driven. That is, the commercial power supply 1 is temporarily converted into a DC voltage by the rectifier circuit 4 and this DC power is converted to 20 kHz by the inverter 2 by turning on and off the semiconductor switching element 5.
Converted to high frequency power of z or more. Further, the inverter 2 boosts the high-frequency power to a high-frequency high voltage by the boosting transformer 6 and applies the high-frequency power to the magnetron 13 via the high-voltage rectifier circuit 7. The magnetron 13 is driven by the high DC voltage and radiates a microwave of 2.45 GHz to the heating chamber to heat the object to be heated. In addition, since a high frequency heating device for home uses a converted power of 1000 W or more, it is important technology to increase the efficiency of the inverter 2.

A conventional home-use high frequency heating apparatus has a circuit configuration as shown in FIG. The inverter 2 has a rectifying / smoothing circuit 4 composed of a rectifier diode for rectifying a commercial power supply, an inductor, and a capacitor, and converts the commercial power supply into a pulsating DC voltage once. By turning on and off the first semiconductor switching element 5 at a high frequency of 20 kHz or more, high frequency power is generated in the primary winding of the step-up transformer 6. The step-up transformer 6 is excited by the high-frequency power, generates a step-up output in the secondary winding, and applies a high-frequency high voltage to the high-voltage rectifier circuit 7. The high voltage rectifier circuit 7 is a step-up transformer 6
Is rectified and a high DC voltage is applied to the magnetron 3. The inverter circuit 2 forms a resonance circuit by the capacitors 8, 10 and the primary winding of the step-up transformer 6, and utilizes the resonance phenomenon of the resonance circuit to reduce the voltage when the semiconductor switching elements 5, 9 are turned off or turned on. The slope is gentle. As a result, when the semiconductor switching elements 5 and 9 are turned on, switching is performed at zero current and zero voltage, and there is no period in which voltage and current overlap. Further, when turning off, since the voltage gradually rises from zero voltage, the area where the voltage and the current overlap is very small. Therefore, the switching loss of the semiconductor switching elements 5 and 9 is reduced, and the inverter circuit is configured to have high efficiency.

[0004]

A household high-frequency heating apparatus is a cooker that heats food with microwaves by receiving power of about 1000 W to 1500 W from a 100 V commercial power supply. Since a large amount of electric power is handled, it is necessary to supply electric power from a commercial power supply. However, there is a great demand from users who want to use it on a desk or outdoors. In order to realize this, it is necessary to mount a power supply source on the high-frequency heating device itself and have a cordless configuration that can be used without supplying power from an external power supply. In recent years, the development of rechargeable secondary batteries has progressed for applications such as mobile phones, personal computers, and electric vehicles. Small size and light weight are realized. Against this background, it has become practical to use a configuration in which a secondary battery is mounted for a short period of time even for electrical equipment that handles large power, such as a high-frequency heating device.

[0005] One secondary battery of a certain type (single unit) is called a cell. The voltage per cell is nominally 1.2 V for nickel-cadmium and nickel-metal hydride storage batteries, and nominally 3.2 V for lithium ion.
The voltage is as low as 7V. When supplying large power at such a low voltage, a very large current must be passed. An inverter that drives a magnetron that generates microwaves when the current increases increases in size and price in order to reduce the loss of semiconductor switching elements and capacitors used therein. When handling 1000 W of power,
If the power source is a commercial power source of 100 V, the current of the commercial power source is 10 A when the power factor is 100%. However, if the power source is 50 V, a current of 20 A flows through the power source, and the current handled by the inverter increases accordingly. In order to keep the loss at the same level even if the current increases in an electric component such as a semiconductor switching element and a capacitor in the inverter, the size must be increased. Considering the production of inverters in factories, when the size of electrical components changes, it is necessary to partially or entirely change existing production equipment, and in any case, a large investment is imposed. Therefore, it is necessary to prevent a large change in the product size.

For this purpose, it is necessary to connect a plurality of cells in series and supply a certain voltage to the inverter. However, when multiple cells are connected in series and 30V
When the above voltage is obtained, the following problems occur.

First, battery life is significantly degraded by overdischarging or overcharging. In particular, in applications where a large amount of power is used in a short time, such as a high-frequency heating device, overdischarge becomes a problem.

[0008]

According to the present invention, there is provided a high-frequency heating apparatus for driving a magnetron by converting electric power in a battery by an inverter and driving a magnetron.
A charging unit for charging the battery with power, a command unit for controlling the operation of the inverter and the constant current unit, an operation unit for giving an external operation instruction to the command unit, and an operation state detection unit for detecting the operation state of the battery The stop of the discharge of the electric power from the battery is performed by giving priority to the signal from the operation state detection unit over the signal from the operation unit.

[0009] Even in a device that consumes a large amount of power in a short time, such as a high-frequency heating device, such as a high-frequency heating device, it is possible to prevent the battery life from being shortened by overdischarge.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention provides a battery, an inverter for converting the power of the battery, a magnetron energized by the inverter, a charging unit for charging the battery with power from an external power supply, A command unit for controlling the operation of the charger, an operation unit for giving an external operation instruction to the command unit, and a display unit for displaying the operation state of the command unit, the command unit is a signal from the operation unit , The operation of the inverter is instructed to start the discharge of the battery power, and the stop is performed by giving priority to the operation state of the battery over the signal from the operation unit. With this configuration, even if the remaining amount of electricity in the battery is smaller than the amount of electricity to be released during the time set by the operation unit, the operation of the inverter is stopped before the remaining amount of electricity in the battery is used up And the discharge can be terminated.

[0011] The operation state of the battery is determined by the temperature rise of the battery. With this configuration, the discharge state of the battery can be detected.

The operating state of the battery is determined based on the gradient of the temperature rise of the battery. With this configuration, the discharge state of the battery can be determined.

The operating state of the battery is determined based on the difference between the temperature rise of the battery and the ambient temperature. With this configuration, the discharge state of the battery can be determined.

The operating state of the battery is determined based on the voltage of the battery during discharging. With this configuration, the discharge state can be determined based on a decrease in the battery voltage at the end of discharge.

[0015]

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

FIG. 1 is a circuit block diagram showing a configuration of a high-frequency heating device according to a twelfth embodiment. 11 is a battery, 1
2 is an inverter, 13 is a magnetron, 14 is a charging unit,
Reference numeral 15 denotes a command unit, 16 denotes an operation unit, 17 denotes a display unit, and 18 denotes an operation state detection unit.

As the battery, a secondary battery such as a nickel-cadmium storage battery or a nickel-hydrogen storage battery or a lithium-ion storage battery is used, and a plurality of cells are connected in series to have a high voltage.

When a lunch box kept in a refrigerator by a high-frequency heating device is heated, it is necessary to heat the microwave for about 2 minutes at a power of about 500 W with microwave output. Since the efficiency of the high frequency heating device is about 56%, the battery supplies about 900 W of power. For example, when a nickel-cadmium storage battery is used, the rated current capacity of the battery is 1.7 Ah.
If the average voltage is 1.2 V, the power capacity per cell is 2.04 wh. The electric energy when outputting 900 W for 2 minutes is 30 wh, and when this is repeated three times, the electric energy required for the battery is 90 wh. Since the power capacity per cell is 2.04 wh, 44 cells are required. When these are connected in series, the battery voltage is about 52.8 V,
The current will be about 17A. The charging of the battery 11 is performed by the charging unit 14 according to a command from the command unit 15. Charging unit 14
Converts the voltage of the external power supply 19 into a voltage of 52.8 V or more necessary for charging, and charges the battery 11.

The inverter 12 converts the DC voltage of the battery 11 from 20 kHz to 3 using a semiconductor switching element.
The voltage is converted to a high-frequency AC voltage of 0 kHz, the voltage is boosted by a step-up transformer, and this voltage is converted to a high DC voltage by a rectifier. Since the peak value of the current flowing through the semiconductor switching element reaches about 50 A, a low-pass filter including a coil and a capacitor is provided at the input terminal of the inverter 12, and the battery 11 generated when the semiconductor switching element operates at 20 kHz to 30 kHz is generated. The amount of current ripple is reduced, and a current having an average of 17 A and a similar peak value flows through the battery 11. The DC high voltage energizes the magnetron 13. The magnetron 13 is energized and driven by a high voltage to generate a microwave. Inverter 12 is controlled by command unit 15.

The command section 15 receives an operation command of the inverter 12 and a display section 17 based on a signal from a key input from the operation section 16.
Command to display the status. As a result, the inverter 1
2 starts operation, and the battery 11 starts discharging. Since the battery 11 discharges 1/3 of the total amount of electricity in a short time of 2 minutes with a large current of 17 A, if the time set in the operation unit is long, the remaining amount of electricity in the initial stage of the battery is within the set operation time. It could be zero,
In this case, if the operation is continued, the battery is overdischarged and the battery 11
Will significantly impair the life of the device. Even for a short time, the amount of discharge electricity is large, so that the degree of overdischarge becomes deep. For this reason, the operation state detection unit 1 of the battery 11
8 is provided to the command unit 15, and the command unit 15 stops the operation of the inverter 12 by giving priority to the signal of the operation state detection unit 18 over the signal from the operation unit 16. As a result, overdischarge of the battery can be suppressed, and the life of the battery can be prevented from being significantly impaired.

(Embodiment 2) FIG. 2 is a simplified perspective view showing the structure of a high-frequency heating device, as viewed from the side. Reference numeral 20 denotes a door, and 21 denotes an object to be heated placed in a heating chamber. Since the battery 11 weighs about 2 kg and is heavy, the batteries 11 are arranged as close to the bottom of the high-frequency heating device as possible. The battery 11 is packaged in two blocks in order to connect 40 or more cells in series. Reference numeral 18 denotes an operation state detection unit provided on a package of the battery 11. The operating state detecting unit 18 uses a thermistor, and detects the temperature of the battery 11 by using the thermistor. Battery 11 has a large current of 17A and 2
Since 1/3 of the total amount of electricity is discharged in a short time of one minute, the heat generation of each cell becomes large. Since the temperature rise of the cell increases as the discharge proceeds, a certain degree of discharge can be known from the cell temperature. Since a plurality of cells are connected and packaged, the operation state detection unit 18 is provided at the center of the package where the temperature rise is highest. In addition, the bottom plate of the high-frequency heating device is used for dissipating the heat of the battery.
Is configured to be in close contact with the bottom plate.

The broken line in FIG.
This shows the battery temperature based on the output of the operation state detection unit 18, and the solid line is a characteristic diagram showing the temperature inside the cell. Since the operating state detector 18 is attached to the surface of the packaged battery 11, the temperature is lower than that inside the cell, and there is a time delay in the temperature rise. As described above, the battery 11 has a large current of 17
Since 1/3 of the total amount of electricity is discharged in a short time of one minute, if there is a delay in detection of the progress of the discharge, overdischarge may occur. Since the full discharge level is reached at the cell temperature T1, the command unit 15 instructs the inverter 12 to stop the operation in order to stop the discharge when the output level of the operation state detection unit 18 reaches the level of the temperature T2. It is configured to give. With such a configuration, discharge can be stopped at an appropriate cell temperature, and overdischarge does not occur.

FIG. 4 is a characteristic diagram showing the temperature characteristics of the battery 11. The temperature rises with the start of discharge of the battery 11 at time zero, and the temperature T rises during the operation time set by the operation unit.
2 shows a state in which the state has reached 2 and the inverter 12 has stopped and has finished discharging. The internal temperature of the cell starts to decrease after slightly increasing, but the temperature increase detected by the operation state detecting unit 18 is the heat capacity of the battery 11, and continues to increase for a while after the discharge is stopped. Overshoot becomes large and the stop determination temperature level T
May rise to 2. The internal temperature of the cell decreases almost at the same time as the end of the discharge. However, it takes t until the output signal of the operation state detecting unit 18 again decreases to the stop determination temperature level T2.
It takes a long time of three. Therefore, the inverter 12 cannot be restarted until after the time t3.
It is desirable that the temperature of the battery 11 does not rise as much as possible after the shutdown of the inverter 2.
After that, the fan 22 is operated to suppress the temperature rise of the battery 11.

(Embodiment 3) FIG. 5 is a characteristic diagram showing the relationship between the amount of electric discharge of the battery 11 and the internal resistance of the battery 11, and the internal resistance increases as the amount of discharge approaches 100%. . In particular, the internal resistance sharply increases from the point where the discharge amount exceeds 80%. If the current supplied from the battery 11 is controlled to be constant, the heat generated by the battery 11 is proportional to the internal resistance.
From the point where the percentage exceeds%, the value rapidly rises. Therefore,
The amount of discharge can be detected based on the amount of change in the temperature rise with time, that is, the temperature gradient. The command unit 15 determines the time change of the output signal of the operation state detection unit 18 formed of a thermistor, and controls the inverter 12 so that the discharge amount does not exceed 100%, thereby preventing overdischarge. .

The magnetron 13 energized by the high voltage generated by the inverter 12 rises in temperature due to internal loss,
As a result, the magnetic permeability of the permanent magnet constituting the magnetron 13 decreases, and the operating voltage decreases. Therefore, when the inverter 12 performs control to keep the output current constant, the output power is reduced by an amount corresponding to the decrease in the operating voltage of the magnetron 13, and
As a result, the current of the battery 11 decreases. In this case, when the amount of discharged electricity of the battery 11 exceeds 80% and the current of the battery 11 decreases even if the internal resistance increases, the amount of discharge can be detected without a sharp rise in temperature due to the increase in internal resistance. May disappear. For this reason, when the discharge amount is detected based on the temperature gradient of the battery 11, it is more preferable that the inverter 12 performs input current constant control.

(Embodiment 4) When judging the amount of discharge electricity based on a rise in the temperature of the battery 11, the state of the ambient temperature is a problem. According to the method described in the second embodiment, when the ambient temperature is low, the temperature of the battery 11 is the determination level of the discharge stop according to the signal of the operation state detecting unit 18.
Before reaching T2, the amount of discharge electricity may reach 100%.

In this case, overdischarging may occur.
It is necessary to consider the ambient temperature, and as shown in FIG. 2, the command section 15 provides the ambient temperature detecting means 23 at a position which is not affected by heat from other heating elements. An operation is performed to change the level at which the signal is determined. That is, when the ambient temperature is low, the determination level is set low, and when the ambient temperature is high, the determination level is set high, so that the amount of discharged electricity is properly determined.

In a nickel-cadmium storage battery or the like, 2
It can be considered that there is almost no change in the internal resistance when left in an atmosphere of 0 ° C. to 60 ° C. as compared with the change in the internal resistance during discharge. When the inverter 12 controls the input current to be substantially constant, the power supply from the battery 11 is also substantially constant, and the internal resistance increases as the amount of discharged electricity increases, as shown in FIG. The rate of increase is from 20 ° C to 6 ° C.
Since it becomes the same regardless of the ambient temperature between 0 ° C., even if the battery 11 is configured to stop the discharge at a point where the temperature rises by a specified temperature with respect to the ambient temperature during the discharge, the discharge amount of electricity is appropriately adjusted. Can be determined. Therefore, the command unit 15 can stop the inverter 12 when the difference between the signal of the operation state detecting unit 18 and the signal of the ambient temperature detecting unit 23 reaches a specified value.

This specified value is 10 deg with respect to the ambient temperature.
Is set between 20 and 20 deg. (Embodiment 5) The cell voltage and the amount of discharged electricity have the characteristics shown in FIG. In the same figure, 8c, 4c, 1c and 0.2c indicate the magnitude (multiple) of the discharge current with respect to the rated current.
c indicates that the discharge current was set to 8 times the rated capacity. As can be seen from this characteristic, when the amount of discharged electricity increases, the cell voltage decreases, so that the amount of discharged electricity can be determined based on the cell voltage. Therefore, as shown in FIG. 7, the operation state detection unit 18 of the present invention is configured by a resistor 24, detects by dividing the voltage of the battery 11, and transmits the signal to the command unit 15.

The battery 11 used in the high-frequency heating device of the present invention discharges 1/3 of the total electricity in a short time of 2 minutes with a large current of 17 A. Since this is used with a rating of about 1.7 Ah (discharge current 1c becomes 1.7 A), it becomes about 10 c. With such a large current, only about 80% of the discharged electricity is used even if the discharge is stopped when the voltage per cell becomes 0.8 V. For this reason, the command section 15 outputs a signal of the operation state detecting section 18 at, for example, 0.8 / cell.
Discharge is continued for a certain period after V is reached. This is set as a fixed time. With this configuration, the voltage of the battery 11 can be detected, and the inverter 12 can be controlled with almost 100% of the amount of discharged electricity to stop the discharge.

In the above embodiment, the case of the high-frequency heating device has been described. However, it is needless to say that the over-discharge of the battery can be similarly prevented by using the high-frequency heating device in which the battery and the inverter are combined. Absent.

[0032]

As described above, the present invention has the following effects.

A battery, an inverter for converting the power of the battery, a magnetron energized by the inverter, a charging unit for charging the battery with power from an external power supply, and controlling operations of the inverter and the charging unit. A command unit, an operation unit for giving an operation instruction to the command unit from the outside, and a display unit for displaying an operation state of the command unit, wherein the command unit operates the inverter based on a signal from the operation unit. By issuing a command, the battery power is started to be discharged, and the stop is performed by giving priority to the operation state of the battery rather than a signal from the operation unit. It is possible to prevent the battery from being over-discharged even if the battery is used in a device that consumes it, so the battery life is not impaired. There is an effect.

[Brief description of the drawings]

FIG. 1 is a circuit block diagram showing a configuration of a high-frequency heating device according to one embodiment of the present invention.

FIG. 2 is a side perspective view of the high-frequency heating device.

FIG. 3 is a characteristic diagram showing a temperature change of a battery used in the high-frequency heating device.

FIG. 4 is a characteristic diagram showing a temperature change of a battery used in the high-frequency heating device.

FIG. 5 is a characteristic diagram showing the relationship between the internal resistance of the battery and the amount of discharged electricity.

FIG. 6 is a characteristic diagram showing a relationship between a cell voltage and a discharge electricity amount.

FIG. 7 is a circuit diagram showing a configuration of an operation state detection unit of the high-frequency heating device according to one embodiment of the present invention.

FIG. 8 is a circuit block diagram showing a configuration of a conventional high-frequency heating device.

FIG. 9 is a circuit diagram showing a configuration of an inverter used in the high-frequency heating device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Battery 12 Inverter 13 Magnetron 14 Charging part 15 Command part 16 Operation part 17 Display part 18 Operation state detecting part 23 Atmospheric temperature detecting means

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Kazunari Nishii 1006 Kadoma, Kazuma, Osaka Pref. F-term (reference) in Matsushita Electric Industrial Co., Ltd. EB36 5G003 AA01 BA03 CA02 CA11 CB01 DA07 DA13 DA15 EA06 EA08 FA08 GB03 GB06

Claims (6)

[Claims] A battery, an inverter for converting power of the battery, a magnetron energized by the inverter, a charging unit for charging the battery with power from an external power supply, and an operation of the inverter and the charging unit. A command unit for controlling, an operation unit for externally giving an operation instruction to the command unit, and an operation state detection unit for detecting an operation state of the battery, wherein the command unit is an inverter based on a signal from the operation unit. A high-frequency heating device configured to start the discharge of battery power by instructing the operation of the operation state, and to give priority to the signal from the operation state detection unit over the signal from the operation unit. 2. The high-frequency heating apparatus according to claim 1, wherein the operation state of the battery is detected by a rise in the temperature of the battery. 3. The high-frequency heating apparatus according to claim 1, wherein the operation state of the battery is detected by a gradient of a temperature rise of the battery. 4. The high-frequency heating apparatus according to claim 1, wherein the operation state of the battery is detected by a difference between a temperature rise of the battery and an ambient temperature. 5. The high-frequency heating apparatus according to claim 1, wherein the operating state of the battery is detected by a voltage during discharging of the battery. 6. The high-frequency heating apparatus according to claim 1, further comprising a display unit for displaying an operation state of the command unit.