JP4982221B2 - Electrical equipment - Google Patents

Description

  The present invention relates to an electric device designed to stabilize microcomputer operation when a control circuit is powered off.

2. Description of the Related Art Conventionally, various types of electric devices that control loads with a control circuit including a microcomputer have been provided (for example, Patent Document 1). This document describes a configuration in which a control circuit is turned on and off using a microcomputer and a relay. When the driving of the load is stopped, a microcomputer and a relay are used to reduce power consumption in the standby state.
Japanese Patent No. 3400930

  By the way, in an electric apparatus using a microcomputer, when the power supply of a control circuit including the microcomputer is turned off, the microcomputer power supply becomes transiently unstable, and the microcomputer may malfunction. In this case, there is a possibility that the microcomputer and thus the control circuit may operate again without stopping the power supply.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to control a load by a control circuit including a microcomputer. Even if the control circuit power supply may become unstable during a power-off operation. An object of the present invention is to provide an electric device that can reliably cut off a control circuit power supply.

The invention of claim 1 includes a microcomputer and self-conducting holding means which is a separate component from the microcomputer, and the microcomputer can enable / disable control the self-conducting holding function of the self-conducting holding means. A control circuit for controlling the load, a DC power supply circuit for the control circuit that supplies power to the control circuit, a first switch means for power on / off instruction that is turned on / off on the operator side, Provided in the energization path from the DC power supply circuit for the control circuit to the control circuit to supply / stop the power supply. Conduction / non-conduction based on the on / off operation of the first switch means And when the first switch means is turned on and operated in a standby state in which no power is supplied to the control circuit, the second switch means is guided. With the power to the control circuit is supplied by the microcomputer to enable the self-conducting holding function of the self-conductive holding means, said second switch by the self-conducting retaining means Self conductive holding function holding the conductive state means, the with the microcomputer to disable the self-conducting holding function of the self-conductive holding means, said second switching means is nonconductive when said first switching means off operation characterized in was configured to stop power supply to the control circuit by the.

  In the above configuration, when the first switch means is turned on and operated in a standby state in which power to the control circuit is not supplied, the second switch means is turned on to supply power to the control circuit. At the same time, the microcomputer activates the self-conduction holding function of the self-conduction holding means. Therefore, the conduction of the second switch means is continued. When the first switch means is turned off while the microcomputer is operating, the microcomputer invalidates the self-conduction holding function of the self-conduction holding means and the second switch means is non-activated. Since the power supply to the control circuit is stopped due to the conduction, the power supply to the control circuit can be stopped reliably, and the power consumption in the control circuit in the standby state can be eliminated.

  After the first switch-off operation, the power supply to the control circuit is normally zero without becoming unstable. However, in the transition period of this power supply voltage drop, the power supply voltage becomes unstable such as chattering and becomes microscopic. There is concern about the computer malfunctioning.

  However, in the first aspect of the present invention, since the first switch means is turned off, the second switch means remains in a non-conductive state, so that the microcomputer malfunctions due to unstable power supply voltage. Even if the self-conducting holding function of the self-conducting holding unit is validated, the self-conducting holding unit does not conduct, and therefore the second switch unit does not conduct again, and the control circuit The power to the can be stopped reliably. As a result, malfunction of the microcomputer can be stopped reliably.

  According to the present invention, the load is controlled by the control circuit including the microcomputer. Even when the control circuit power supply becomes unstable during the power-off operation, the control circuit power supply can be reliably cut off.

  Hereinafter, a first embodiment in which the present invention is applied to an induction heating cooker will be described with reference to the drawings. FIG. 2 shows the appearance of the induction heating cooker 1, and this induction heating cooker 1 is a cooker (so-called oden warmer) for keeping the oden warm. An operation panel 3 is provided in front of the lower portion of the outer box 2 of the induction heating cooker 1, and the operation panel 3 is provided with a switch operation unit 4 for operating an on / off switch 28 described later. ing. The operation panel 3 is provided with a display 3a.

  A vent 2a is formed on the side surface of the lower portion of the outer box 2. Although not shown, vents are also formed on the other surface below the outer box 2. Further, a top plate (not shown) is provided on the upper upper surface of the outer box 2. The oden pan 5 is placed on the top plate.

  FIG. 1 shows an electric circuit configuration of the induction heating cooker 1. In FIG. 1, a commercial AC power supply 6 is connected to a DC power supply circuit 7 for heating means. The DC power supply circuit 7 is configured by connecting a full-wave rectifier circuit 8, a choke coil 9, and a smoothing capacitor 10 as shown in the figure. Between the positive power supply output terminal 7a and the negative power supply output terminal 7b of the DC power supply circuit 7, a heating coil 11 as a load and heating means and a switching element 12 made of IGBT are connected in series. Furthermore, a resonance capacitor 13 is connected in parallel to the heating coil 11, and a flywheel diode 14 is connected in antiparallel to the switching element 12. The heating coil 11, the switching element 12, the resonance capacitor 13, and the flywheel diode 14 constitute an inverter 15.

The heating coil 11 is disposed below a top plate (not shown), and a high-frequency current flows through the heating coil 11 by conduction / non-conduction control (on / off control) of the switching element 14 to inductively heat the pan 5. (Induction heating method).
The control circuit 16 includes a microcomputer 17 and a thyristor 18 serving as a self-conduction holding means. The gate of the switching element 12 of the inverter 15 is connected to the output port P3 of the microcomputer 17 via a resistor 19, and the microcomputer 17 controls the switching element 12 on and off.

  Once the thyristor 18 is turned on (hereinafter referred to as “on”), it cannot be turned off (hereinafter referred to as “off”) by a gate signal. In order to turn it off, it is necessary to set the current flowing through the element to be equal to or lower than the holding current or apply a reverse voltage to the element (self-conducting holding function).

Further, as will be described later, the microcomputer 17 controls the self-conduction holding function of the thyristor 18 to be enabled / disabled.
An input terminal of the switching power supply 20 which is a control power supply DC power supply circuit is connected to the DC power supply circuit 7 via a diode 21. A capacitor 22 is connected between the input terminal of the switching power supply 20 and the ground GND.

  The switching power supply 20 adjusts the voltage of the DC power supplied from the DC power supply circuit 7 by using a switching element (not shown), rectifies the DC power by a rectifying means, converts it to a DC power supply for a control circuit power supply, and outputs it. The output terminal of the switching power supply 20 is connected to the power input terminal Vcc of the microcomputer 17 through the emitter / collector of a PNP transistor 23 which is the second switch means. A fan motor 24 is connected between the collector of the transistor 23 and the ground GND, and a capacitor 25 is connected.

The fan motor 24 is for driving a fan (not shown) provided in the outer box 2, and the fan sucks air from the vent 2a and discharges it from another vent (not shown). The inside of the outer box 2 is cooled.
The base of the transistor 23 is connected to the resistor 26, the forward thyristor 18, and the input port P1 of the microcomputer 17 in this order. Further, the base of the transistor 23 is connected in turn to a resistor 27, an on / off switch 28 as a first switch means, and an input port P2 of the microcomputer 17. The on / off switch 28 is a normally open type and has a mechanical contact that is turned on (conductive) only when the operation unit 4 is pushed by an operator.

  A common connection point Q between the input port P2 and the on / off switch 28 is connected to the ground GND via a pull-down resistor 29. The gate of the thyristor 18 is connected to the common connection point Q through a resistor 30, and the common connection point Q is connected to the power input terminal Vcc of the microcomputer 17 through a forward diode 31. Yes.

  The microcomputer 17 includes an internal switch 32 (third switch means) inside, and the internal switch 32 is composed of an FET having a high operating speed. The internal switch 32 is controlled to be turned on / off according to the program of the microcomputer 17. That is, when the port P2 becomes high level (the on / off switch 18 is turned on) by executing the program immediately after the microcomputer 17 is activated, an internal switch-on signal is generated and the internal switch 32 is turned on (the triac 18 self-conducting holding function When the next port P2 becomes high level again, an internal switch-off signal is generated and the internal switch 32 is turned off (the self-conduction holding function of the triac 18 is disabled).

  The operation of the above configuration will be described together with operations related to power supply / stop to the microcomputer 17. In a state where the DC power supply circuit 7 is simply connected to the commercial AC power supply 6 (standby state), the thyristor 18 is off and the transistor 23 is off. For this reason, power from the switching power supply 20 is not supplied to the control circuit 16 or the fan motor 24, and the output current Id of the switching power supply 20 does not flow. In this state, the current to the switching power supply 20 is almost zero, the switching element 12 of the inverter 15 is also off, and the current from the commercial AC power supply 6 is also almost zero. The power is almost zero.

  In this standby state, when the operator (user) pushes the switch operation unit 4 and turns on / off switch 28 (the first push operation is the turn-on operation and the next push operation is the turn-off operation), the transistor 23 Emitter, base, resistor 27, on / off switch 28 in the on state, resistor 30, base of thyristor 18, port P1 of microcomputer 17, internal switch 32 (but off in this state), and ground GND circuit are formed. (Current does not flow yet).

  When the on / off switch 28 is turned on, power is supplied to the power terminal Vcc of the microcomputer 17 via the diode 32 (step S1 in FIG. 3), and the microcomputer 17 starts operating (step S2). That is, the microcomputer 17 is activated, and the microcomputer 17 executes control according to a program stored in the memory. As the first control process after the activation, it is determined whether or not the input port P2 is at a high level (whether or not the on / off switch 28 is turned on) (step S3), and the high level (the on / off switch 28 is turned on). If so, an internal switch-on signal is generated to turn on the internal switch 32 (step S4). In this case, an appropriate temperature display is performed on the display 3a, a gate signal for the switching element 12 is output from the output port P3, the switching element 12 is turned on / off, and heating cooking (heat retention) is started.

Since the current flows from the gate of the thyristor 18 to the ground GND when the internal switch 32 is turned on, the thyristor 18 is turned on, and the current Ih is supplied via the resistor 26 to the anode, cathode, and microcomputer 17 of the thyristor 18. It flows with the internal switch 32 and the ground GND. Then, the transistor 23 for supplying / stopping power to the control circuit 16 and the fan motor 24 is turned on. After that, even when the on / off switch 28 is turned off after the switch operation unit 4 is released, the thyristor 18 is kept on by the self-conducting holding function, and the transistor 23 is kept on. Will do. Thereafter, when the input of the input port 2 does not fall to the low level after waiting for a predetermined time (for example, 2 seconds) (“NO” in Step S5 to Step S6), the microcomputer 17 sets the on / off switch 28 in the display 3a. Display that there is a possibility of contact welding (abnormal display) (step S11). That is, when the operator turns on / off the switch 28, the on / off switch is normally released within 2 seconds, so that the high level after the release is judged as an abnormality such as contact welding. Is.
In addition, the switching element 12 is turned on / off at high frequency, a high frequency current flows through the heating coil 11, and the pan 5 is induction heated.

  In such an operating state of the microcomputer 17, when the switch operation unit 4 is pushed (turned off) next and the on / off switch 28 is turned on and the port P 2 becomes high level (“YES” in step S 7), The gate signal output from the port P3 is stopped, the temperature display on the display 3a is stopped, and the internal switch 32 is turned off according to the program (step S8).

  As a result of turning off the internal switch 32, the thyristor 18 is turned off. However, while the switch operation unit 4 is turned off, that is, while the on / off switch 28 is turned on, a current flows through the base of the transistor 23 and the transistor 23 is turned on. The power source of the switching power source 20 is continuously applied to Vcc. Therefore, the microcomputer 17 continues normal operation.

  When the switching operation of the switch operation unit 4 is released and the on / off switch 28 is turned off (step S9), the power supply of the microcomputer 17 is lowered, the operation of the microcomputer 17 is stopped (step S10), and the standby is performed. It becomes a state.

In this way, while the microcomputer 17 continues normal operation, the power supply is normally lowered and the operation is stopped, and the operation ends normally.
In the standby state, since the transistor 23 is turned off and the power supply to the control circuit 16 is stopped, the power consumption in the control circuit 16 can be eliminated.

According to this embodiment, when the on / off switch 28 is turned off while the microcomputer 17 is operating, the microcomputer 17 turns off the internal switch 32 and maintains the self-conduction of the thyristor 18. In addition to invalidating the function, the transistor 23 is turned off and the power supply to the control circuit 16 is stopped, so that the power supply to the control circuit 16 can be stopped reliably and the consumption in the control circuit 16 in the standby state. Electric power can be lost.
Therefore, it is possible to eliminate the temperature rise in the standby state, so that the temperature environment preferred by pests (such as cockroaches) is not caused, and in the standby state (the situation where the user is not near the induction heating cooker 1), Pests can be prevented from entering the outer box 2 from the vent 2a or the like.

  Here, after the on / off switch 28 is turned off, the power supply to the control circuit 16 is normally zero as described above. However, the power supply voltage becomes unstable such as chattering during the transition period of the power supply voltage drop. There is a concern that the microcomputer 17 malfunctions.

  However, according to the above embodiment, since the transistor 23 remains non-conductive because the on / off switch 28 is turned off, the microcomputer 17 malfunctions due to instability of the power supply voltage, and the internal switch 32 is turned off. Even if the thyristor 18 is turned on (the self-conduction holding function is activated), the thyristor 18 is not turned on. Therefore, the transistor 23 is not turned on again, and the power supply to the control circuit 16 is ensured. Can be stopped. As a result, the malfunction of the microcomputer 17 can be stopped reliably.

In particular, according to the present embodiment, as the first switch means, the on / off switch 28 having a mechanical contact which is conductive only at the time of operation is used. Therefore, an inexpensive switch for an electronic circuit can be employed, and low Cost can be reduced.
In this embodiment, since the thyristor 18 is used as the self-conduction holding means, the microcomputer 17 malfunctions unless the microcomputer 17 turns on the internal switch 32 and turns on / off the switch 28. However, the thyristor 18 is not turned on, and safety can be improved.

Further, according to this embodiment, since the switching power supply 20 is used as the DC power supply circuit for the control power supply, unlike the case where the series regulator is used, the current consumption when the load current is zero is extremely small, and the power saving effect is achieved. Is high and there is no fever.
Further, according to the present embodiment, the DC power supply circuit 7 for the heating means is provided, and the output of the DC power supply circuit 7 is supplied to the inverter 15 including the heating coil 11 as the heating means and for the control circuit 16. Therefore, the circuit can be simplified because it is input to the switching power supply 20 which is a DC power supply circuit for control power supply.

  The present invention is not limited to the above embodiment. For example, as a self-conduction holding means, not only a thyristor but also a PNP type as shown in FIG. 4 shown as the second embodiment of the present invention. The transistor 41 and the NPN transistor 42 may be equivalent to the thyristor. In addition to the heating means, the load can be applied to various loads of electrical equipment. The internal switch 32 may be externally attached to the microcomputer 17.

Electric circuit diagram showing a first embodiment of the present invention Diagram showing the appearance of induction heating cooker Diagram showing the flow of on / off switch operation and microcomputer control contents Electric circuit diagram showing a second embodiment of the present invention

Explanation of symbols

  In the drawings, 1 is an induction heating cooker (electrical device), 7 is a DC power supply circuit, 11 is a heating coil (heating means), 15 is an inverter, 16 is a control circuit, 17 is a microcomputer, and 18 is a thyristor (self-conducting holding). Means), 20 is a switching power supply (DC power supply circuit for control power supply), 23 is a transistor (second switch means), 24 is a fan motor, 28 is an on / off switch (first switch means), and 32 is an internal switch. Show.

Claims (6)

It includes a microcomputer and a self-conducting holding means that is a separate part from the microcomputer, and the microcomputer can enable / disable the self-conducting holding function of the self-conducting holding means to control the load. A control circuit to
A DC power supply circuit for a control circuit that supplies power to the control circuit;
A first switch means for power on / off instruction that is turned on / off by the operator;
Provided in the energization path from the DC power supply circuit for the control circuit to the control circuit to supply / stop the power supply. Conduction / non-conduction based on the on / off operation of the first switch means A second switch means
When the first switch means is turned on and operated in a standby state in which power to the control circuit is not supplied, the second switch means is turned on to supply power to the control circuit, and the microcomputer The self-conduction holding function of the self-conduction holding means is enabled, the self-conduction holding means holds the conduction state of the second switch means by the self-conduction holding function, and the first switch means is turned off. and with the microcomputer to disable the self-conducting holding function of the self-conducting retaining means when, said second switching means is configured to stop power supply to the control circuit by a non-conductive Features electrical equipment. Said first switch means, electrical apparatus according to claim 1, characterized in that a structure having a mechanical contact and rendered conductive only when operating.   The electric device according to claim 1, wherein the self-conducting holding unit includes a thyristor.   The electric device according to claim 1, wherein the load is an induction heating type heating unit.   The electrical apparatus according to claim 1, wherein the control power supply DC power supply circuit includes a switching power supply.   A DC power supply circuit for the heating means is provided, and an output of the DC power supply circuit is supplied to the heating means and input to the control power supply DC power supply circuit for generating a power supply for the control circuit. The electric device according to claim 4.

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