JPH04137387A - Induction heating cooker - Google Patents

Abstract

PURPOSE:To prevent a breaking of a switching element by applying a high dV/dT and the like, by turning off the switching element when the power source voltage is less than a specific level and the operation in a controller is stopped, in a starting time or in a stopping time CONSTITUTION:A control voltage detector 6 stops the operation in a controller 5 to prevent an unstable operation of a microcomputer and the like in the controller 5 when the power source voltage of the controller 5 is less than a specific level in a starting time of in a stopping time, and turns off the output of a drive circuit 4 when the operation in the controller 5 is stopped. As a result, the input terminal of a switching element 2 can be turned off, and a breaking by applying a high dV/dT and the like can be prevented. Furthermore, a drive voltage detector 8 is provided, and by turning off the switching element 2 when the power source voltage of the drive circuit 4 is less than a specific value, the ON/OFF oscillation of the element 2 when the power source voltage is not sufficient is prevented, and a breaking of the element 2 owing to an excessive loss can be also prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an induction heating cooker used in general households.

BACKGROUND OF THE INVENTION In recent years, induction heating cookers have become popular in general households as their superior features of safety, cleanliness, and high efficiency have been recognized. Induction heating cookers are configured to inductively heat a load pan that is magnetically coupled to the heating coil by applying a high frequency current of several tens of kilohertz to a heating coil wound on a spiffle flat plate. Complex processing was required. In addition, because induction heating cookers are safe and clean, they are often used for frying, etc. Therefore, it is becoming common for induction heating cookers to be equipped with functions such as automatic temperature control. There is.

As described above, the control circuit for the induction heating cooker is required to control an automatic temperature control function in addition to controlling the high-frequency inverter, making it complicated and expensive.

As a countermeasure to this problem, it has recently become possible to implement complex processing with a simple circuit by using a microcomputer in the control circuit. FIG. 4 shows a conventional induction heating cooker. In FIG. 4, 1 is a heating coil, 2 is a switching element, 3 is an inverter circuit that supplies high-frequency current to the heating coil 1 by turning on and off the switching element 2, and 6 is a control unit that outputs on/off timing of the switching element 2. , 4 is a drive circuit that receives a signal from the control unit 5 and drives the switching element 2 on or off;
Reference numeral 9 denotes a control voltage detector that detects the power supply voltage in the control section 5 and stops the operation of the control section 5 when the voltage is below a predetermined level.

With the above configuration, when the power supply voltage of the control unit 6 is below a predetermined level during startup, etc., the operation of the control unit 5 is controlled to prevent unstable operation of the microcomputer, etc. in the control unit 5. It is stopped.

Problems to be Solved by the Invention However, according to the conventional induction heating cooker,
When the power supply voltage of the control unit 6 is below a predetermined level, the operation of the control unit 5 is stopped, so the output to the drive circuit 4 is not determined and becomes unstable, so the output of the drive circuit 4 is also unstable. As a result, high dV/d at power-on
There is a problem in that when T is applied to the switching element 2, the switching element 2 is destroyed.

The present invention addresses the above problem and aims to prevent destruction of switching elements when power is turned on.

Means for Solving the Problems In order to achieve the above objects, the present invention provides a heating coil, a switching element, an inverter circuit that supplies a high frequency current to the heating coil by turning on and off the switching element, and a heating coil that supplies a high frequency current to the heating coil by turning on and off the switching element. a drive circuit for driving; a control unit that outputs on/off timing of the switching element to the drive circuit; and a control unit that detects a power supply voltage in the control unit and stops the operation of the control unit when the voltage is below a predetermined level. The drive circuit includes a control voltage detection section that outputs a signal to turn off the switching element, and when the power supply voltage at the control section is below a predetermined level at startup or stop, the operation at the control section is stopped. The switching element is turned off when the device is in use.

The configuration further includes a delay circuit that delays the switching element off signal from the control voltage detection section, and releases the switching element off after a predetermined period of time has elapsed after canceling the stoppage of the operation of the control section. .

Furthermore, the drive voltage detection section detects the power supply voltage of the drive circuit and outputs a signal to the drive circuit to turn off the switching element when the power supply voltage is below a predetermined value, and the power supply voltage of the control section and the power supply voltage of the drive circuit are both The switching element is configured to be turned off when the respective predetermined values are exceeded.

According to the above configuration of the present invention, when the power supply voltage of the control unit is below a predetermined level and the operation of the control unit is stopped at startup or stop, the drive circuit switches the switching element to It operates to turn off. Therefore, it is possible to prevent damage to the switching element due to application of high dV/dT or the like.

Further, a delay circuit is provided to delay an off signal for the switching element from the control voltage detection section, and the switching element is released from off after a predetermined period of time has elapsed after the stoppage of the operation of the operating section is canceled. This makes it possible to release the output off of the drive circuit until the control section is operating stably, for example, after the control section's microcomputer is operating normally and the initialization of each section is completed. protection becomes possible.

Furthermore, a drive voltage detection unit is provided that detects the power supply voltage of the drive circuit and outputs a signal to the drive circuit to turn off the switching element when the power supply voltage is below a predetermined value, so that both the power supply voltage of the control unit and the power supply voltage of the drive circuit are By configuring the switching element to be turned off when the voltage exceeds a predetermined value, it is possible to prevent the switching element from being destroyed due to excessive loss when the power supply voltage in the drive circuit is insufficient.

EXAMPLE Hereinafter, an example of the present invention will be described with reference to FIG.

In Fig. 1, 1 is a heating coil, 2 is a switching element, 3 is an inverter circuit that supplies high-frequency current to the heating coil/I/1 by turning on and off switching element 2, and 5 is an output that outputs the on/off timing of switching element 2. 4 is a drive circuit that receives a signal from the control unit 5 and drives the switching element 2 to turn on or off;
Reference numeral 6 denotes a control voltage detection section that detects the power supply voltage in the control section 5 and, when the voltage is below a predetermined level, stops the operation of the control section 5 and turns off the output of the drive circuit 4.

According to the above configuration, when the power supply voltage of the control unit 6 is below a predetermined level during startup or stop, etc., the operation of the control unit 6 is disabled in order to prevent unstable operation of the microcomputer, etc. in the control unit S. While stopping, the output of the drive circuit 4 is turned off while it is stopped. Therefore, the input terminal of the switching element 2 can be determined to be off, and damage caused by application of high dV/dT or the like can be prevented.

Next, a second embodiment of the present invention will be described with reference to FIG.

In FIG. 2, 1 is a heating coil, 2 is a switching element, 3 is an inverter circuit that supplies high-frequency current to the heating coil 1 by turning on and off the switching element 2;
6 is a control unit that outputs the on/off timing of the switching element 2; 4 is a drive circuit that receives a signal from the control unit 5 and drives the switching element 2 to turn on or off; 6 is a drive circuit that detects the power supply voltage in the control unit 6; When the level is below a predetermined level, the operation of the control unit 6 is stopped and the drive circuit 4 is
The control voltage detection section 7 outputs the output off signal to the delay circuit 7, and 7 is a delay circuit that delays the release of the output off of the drive circuit 4 by the control voltage detection section θ for a certain period of time.

According to the above configuration, the turning off of the switching element 2 is canceled after a predetermined period of time has elapsed after the stoppage of the operation of the control section 5 is canceled, so that the switching element 2 is turned off until the control section 5 stably operates, for example. It is possible to release the output off of the drive circuit 4 after the microcomputer in the control section 5 operates normally and completes the initialization of each section, and more stable protection of the switching element 2 becomes possible. .

Further, a third embodiment of the present invention will be described with reference to FIG. In FIG. 3, 1 is a heating coil, 2 is a switching element, 3 is an inverter circuit that supplies high-frequency current to the heating coil 1 by turning on and off the switching element 2, and 5 is a control unit that outputs the on/off timing of the switching element 2. , 4 is a drive circuit that receives a signal from the control unit 6 and drives the switching element 2 to turn on or off. 6 detects the power supply voltage in the control unit 5 and stops the operation of the control unit 5 when the voltage is below a predetermined level. A control voltage detection unit 8 detects the power supply voltage of the drive circuit 4 and outputs a signal to turn off the switching element 2 to the drive circuit 4 when the power supply voltage of the drive circuit 4 is lower than a predetermined value. This is the drive voltage detection section.

With the above configuration, it is possible to detect the power supply voltage of the drive circuit 4 and output a signal to the drive circuit 4 to turn off the switching element 2 when the voltage is below a predetermined value. Therefore, on/off oscillation of the switching element 2 is prevented when the power supply voltage in the drive circuit 4 is insufficient, and destruction of the switching element 2 due to excessive loss at that time can be prevented.

Although this embodiment uses one switching element, it is clear that the effects of the present invention will not be affected in any way even if two or more switching elements are used.

Effects of the Invention As is clear from the above embodiments, according to the present invention, when the power supply voltage of the control section or the power supply voltage of the drive circuit is below a predetermined level, the output of the drive circuit can be determined to be turned off. As a result, it is possible to prevent the switching element from being destroyed when a high dV/dT is applied to the switching element when the power is turned on. Further, the on/off oscillation of the switching element is prevented when the power supply voltage of the drive circuit is below a predetermined level, and it is also possible to prevent destruction of the switching element due to excessive loss at that time.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of an induction heating cooker according to an embodiment of the present invention, FIG. 2 is a block diagram showing the configuration of an induction heating cooker according to a second embodiment of the invention, and FIG. FIG. 4 is a block diagram showing the structure of an induction heating cooker according to a third embodiment of the present invention, and FIG. 4 is a block diagram showing the structure of a conventional induction heating cooker. 1...Heating coil, 2...Switching element, 3...Inverter circuit, 4...
・Drive circuit, 5... Control section, 6...
・Control voltage detection section, 7...delay circuit, 8...
...Drive voltage detection section. Name of agent: Patent attorney Akira Kokaji and 2 others f -
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Claims (3)

[Claims] (1) A heating coil, a switching element, an inverter circuit that supplies a high frequency current to the heating coil by turning on and off the switching element, a drive circuit that drives the switching element, and a drive circuit that supplies the switching element to the drive circuit. a control unit that outputs on/off timing; and a control that detects a power supply voltage in the control unit and stops the operation of the control unit when the voltage is below a predetermined level, and at the same time outputs a signal to the drive circuit to turn off the switching element. and a voltage detection section, and turns off the switching element when the power supply voltage at the control section is below a predetermined level and the operation at the control section is stopped at startup or stop. vessel. (2) A delay circuit for delaying a switching element off signal from a control voltage detection section, wherein the switching element is released from off after a predetermined period of time has elapsed after the stoppage of the operation of the control section is released. 1. The induction heating cooker according to 1. (3) It has a drive voltage detection unit that detects the power supply voltage of the drive circuit and outputs a signal to the drive circuit to turn off the switching element when the power supply voltage is below a predetermined value, and the power supply voltage of the control unit and the power supply voltage of the drive circuit are The induction heating cooker according to claim 1, wherein the switching element is turned off when both of the switching elements reach respective predetermined values or higher.