JP3249251B2 - Load circuit abnormality detection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for detecting an abnormality in a load circuit in a series resonance type high-frequency induction heating oscillator or a power supply device, and more particularly to a signal of a current flowing in a load circuit of the device. The present invention relates to a load circuit abnormality detection device that detects an abnormality such as disconnection of a load circuit by comparing with an ON signal of the device.

[0002]

2. Description of the Related Art Conventionally, an oscillation circuit and a load circuit of a series resonance type high frequency induction heating apparatus are configured as shown in FIG.
And a capacitor (C) connected in series to minimize the impedance of the load circuit at the time of resonance between L and C, and to apply the maximum power to the object to be heated in the work coil so as to remove the object to be heated in the work coil. I have a fever.

On the other hand, there are various shapes of the object to be heated, and when the object is to be incorporated into an automation line to perform a heating operation, the work coil itself must be movable.

However, since a high-frequency high current of several hundred amperes or more flows through a load circuit, a work coil can be made movable by stacking several thin copper plates on a feeder from an output terminal to the work coil, By using a copper flat braided wire, a flexible feeder is provided with flexibility. These flexible feeders have a problem that they break in several months due to poor durability.

[0005] Further, even in a device for fixing a work coil, there is a problem that a connection failure occurs due to corrosion of a connection portion between a feeder and a work coil or an oscillation circuit for a long period of time. When such a load circuit disconnection accident occurs, since the load circuit disconnection detection circuit is not provided in the conventional induction heating oscillator, the abnormality of the oscillator is detected by detecting the heating state of the object to be heated.

However, since the cause of the heating failure of the object to be heated may be due to a factor other than an accident due to disconnection of the load circuit or abnormal contact failure, it is not possible to immediately judge that the load circuit is abnormal. was there.

[0007]

SUMMARY OF THE INVENTION In order to eliminate these drawbacks, the present invention converts a high-frequency current signal inside an induction heating oscillator through a current transformer (CT) into a high-frequency current when a power supply device is operating. It is an object of the present invention to provide a load circuit abnormality detection device that detects the presence or absence of a load circuit and outputs a load circuit abnormality alarm signal.

[0008]

A current flowing in a transistor of a drive circuit of a power supply device for supplying power to a load circuit is converted into an AC voltage by a current transformer (CT), and then rectified to a DC voltage. Abnormality of the load circuit is detected as a load current signal when the voltage is equal to the current value that has exceeded a certain level determined by the zener diode inserted in the circuit indicating the condition of normal operation of the device. Input to the device.

The load circuit abnormality detection device identifies an abnormality in which the current of the drive circuit is not flowing when the switch of the high-frequency induction heating device is on, and issues an alarm. More specifically, a reset set flip-flop circuit that outputs an abnormality, an initialization circuit that performs an initial reset when the power is turned on to the device, and a heating circuit ON signal that indicates an ON state of a transistor drive circuit that supplies power. An output of an exclusive OR circuit (exclusive OR circuit) with a load current signal of the drive circuit, an output of a NAND circuit (NAND circuit) constituting an oscillation on rising malfunction prevention circuit of the oscillation circuit, and the exclusive OR The output of the first AND circuit (AND circuit) with the output of the circuit, the reset output is reset via the signal inversion circuit, the output of the signal of the set simultaneous ON prevention circuit and the output of the first AND circuit are output. Second AND circuit (AND circuit)
And a circuit for inputting an ON signal to the set terminal of the reset set flip-flop circuit based on the output of the second AND circuit and turning on the output of the reset set flip-flop circuit to activate the alarm device Configuration.

That is, the present invention relates to a device for detecting an abnormality of a load circuit in a power supply device for supplying power to a work coil, comprising a capacitor having one end grounded to the other end of a resistor connected in series to a DC power supply. An initialization circuit that is connected in series and outputs a signal that is turned on when the DC power supply is turned on from a connection point of the resistor and the capacitor via a signal inverting circuit; an output signal of the initialization circuit; and a manual switch from the DC power supply. An OR circuit to which an output signal is input in parallel, and a load current signal whose operation level is determined by comparing an AC load current flowing in a drive circuit of the power supply device to a DC voltage and comparing with a Zener voltage, An exclusive-OR circuit to which a heating circuit on signal of the power supply device is input in parallel, and an exclusive OR circuit that directly receives the heating circuit on signal and the heating circuit on signal. A capacitor having one end grounded is connected in series to the other end of the resistor connected in series via a signal inverting circuit connected to the resistor and a negative product circuit in which a signal from a connection point between the resistor and the capacitor is input in parallel. An oscillation-on rising malfunction prevention circuit for preventing simultaneous ON, an output signal of the NOT product circuit of the malfunction prevention circuit, and a first output signal of the exclusive OR circuit which are input in parallel via a switch. A simultaneous ON prevention circuit comprising an AND circuit and a second AND circuit to which an output signal of the first AND circuit and an output signal of the OR circuit via a signal inverting circuit are again inputted in parallel And a reset set in which the output of the second AND circuit is connected to a set terminal, the output of the OR circuit is connected to a reset terminal, and the power supply device outputs an ON signal when an abnormality occurs. A simultaneous flip-flop circuit, wherein the simultaneous on prevention circuit prevents the signal input to the reset terminal and the signal input to the set terminal from being simultaneously turned on while the power supply device is turned on. After the reset / set flip-flop circuit is reset and the heating circuit ON signal is turned on and the malfunction prevention circuit is turned on and the load current signal is not present, the set terminal is turned on and the load circuit is turned on. A load circuit abnormality detection device characterized by detecting an abnormality of the load circuit.

[0011]

The present invention relates to a load circuit abnormality detecting device for a series resonance type high frequency induction heating device, which immediately detects an abnormality in a load current signal due to a disconnection, a contact failure, or the like. The initialization circuit resets the last-stage reset-set flip-flop circuit that outputs an error when the power of the device is turned on, and the logic between the DC power supply and the output of the initialization circuit via a manual switch in parallel with the initialization circuit. The output of the sum circuit is input to the reset terminal of the reset set flip-flop circuit. And the output of the heating circuit ON signal indicating that the device has started to operate and the output of the load current signal are input to the exclusive OR circuit, and the output is input to the set terminal of the reset / set flip-flop circuit to operate. Let it.

In parallel with the exclusive-OR circuit of the output of the heating circuit ON signal and the output of the load current signal, the output of the heating circuit ON signal and the output of the capacitor whose one end is grounded via the signal inverting circuit are input to the NOT product circuit. As a result, an oscillation on rising malfunction prevention circuit is formed. Therefore, when the heating circuit ON signal of the device is output and there is no load current signal, the reset / set / flip-flop circuit is set, the output side is turned on, and the alarm is activated by the ON signal, or the work coil is turned on. The supply of the work to be heated is stopped, and the abnormality of the output circuit is alerted. Further, the power supply of the power supply device is cut off.

An oscillation-on rising malfunction prevention circuit connected to the output of the heating circuit ON signal and inputted to the first AND circuit in parallel with an exclusive OR circuit of the load current signal and the heating circuit ON signal, Performs an operation to turn off during the erroneous output time of the exclusive OR output due to the difference between the output of the heating circuit ON signal and the rise of the load current signal, and the output of the exclusive OR circuit generated at the rise when the oscillation is ON Prevent malfunction.

Also, an exclusive OR circuit of an output via a signal inverting circuit from a circuit connected to a reset terminal of a reset / set / flip-flop circuit of an initialization circuit, an output of a heating circuit ON signal, and a load current signal is provided. By inputting the output through the second AND circuit to the set terminal of the reset / set flip-flop circuit, it is possible to prevent a signal input to the reset terminal and a signal input to the set terminal from being simultaneously turned on.

[0015]

FIG. 2 is a circuit block diagram of a load circuit abnormality detecting device according to the present invention. The current flowing through the transistor 1a of the transistor full-bridge drive circuit 1 shown in FIG. 1 is detected by a current detection current transformer (CT) 4, the load AC current is converted into an AC voltage, and the smoothing circuit 5 converts it into a DC voltage. and level conversion circuit 6 when a constant voltage above (current) is operated with a through Zener diode 6a, and outputs a load current signal I ₁ to the circuit of the next stage.

FIG. 3 shows details of the load circuit abnormality detecting device 7 shown in FIG. 2 of the present invention. An exclusive OR circuit (EXOR circuit) 1 converts the load current signal I ₁ and the heating circuit ON signal S ₁ indicating that the high-frequency induction heating circuit is switched on.
3 and the output is input to a first AND circuit (AND circuit) 20. On the other hand, the heating circuit ON signal S ₁
A signal inversion circuit (inverter) 18 as resistor R ₂ and the negative output of the capacitor C ₂ with one end grounded AND circuit (NAND circuit) 19 oscillating on rising malfunction prevention circuit 9 which is inputted configuration, said first The signal is input to a logical product circuit (AND circuit) 20, and the output is input to a second logical product circuit (AND circuit) 21.
To enter.

A resistor R ₁ and a capacitor C ₁ having one end grounded are connected in series to a +5 V power supply, and a signal inverting circuit is connected in parallel in three stages in this embodiment from the connection point of the resistor R ₁ and the capacitor C ₁ . The initialization circuit 8 performs an operation of resetting the detection signal holding reset set flip-flop circuit via the OR circuit 14 when the power is turned on.
The circuit that enters the OR circuit 14 from the + 5V power supply through the manual switch (SW ₁ ) 11 in parallel with the initialization circuit 8 is operated by manually operating the manual switch (SW ₁ ) 11 to reset, hold, and set the detection signal. The flip-flop circuit (RSF / F circuit) 15 can be reset,
The signal input to the set terminal of the reset set flip-flop circuit (RSF / F circuit) 15 is controlled by the signal inverting circuit 17 incorporated in the output of the OR circuit 14 and the input of the second AND circuit 21. This prevents a signal input to the reset terminal from being turned on at the same time.

FIG. 4 shows a time chart of the circuit of the present invention, and the operation of the load circuit abnormality detecting device of the present invention will be described with reference to FIG. As soon as the power supply (+ 5V) is turned on, the output of the signal inverting circuit 16 of the initialization circuit (INIT circuit) 8 is turned on, and the reset for holding the detection signal of the output circuit is performed.
The set flip-flop circuit (RSF / F circuit) 15 is reset, the output voltage of the output Q becomes 0 V (off),
The alarm device 22 becomes inactive. In the initialization circuit 8, the signal inverting circuit 16 when the power is turned on, the output level is turned on, + from a 5V supply through a resistor R _1, to charge the capacitor C _1, an input signal inverting circuit 16 after a lapse of a certain time Side voltage rises and the signal inverting circuit 1
The output voltage of the circuit 6 becomes 0 V, and the output voltage of the initialization circuit 8 has a waveform shown by INIT in FIG.

The high-frequency induction heating device oscillates, and oscillates _one hour T than the oscillation ON start. When high-frequency induction heating device oscillates, the heating circuit ON signal S ₁ is delivered to the load circuit fault detecting device. As a result, if the high frequency induction heating device is normal, the load current flows to the load, and the load current signal I
₁ is input to the load circuit abnormality detection device. Heating circuit ON signals S ₁ and the load current signal smoothing circuit 5 until between I ₁ of the signal is displayed load current signal I ₁ shown in FIG. 2, the Zener diode 6a is inserted, the load current signal A delay of time T ₂ occurs in I ₁ . Therefore, the load current signal I
A of the output of the exclusive OR circuit of ₁ and the heating circuit ON signal S ₁
The point, although the output waveform A in FIG. 4, a delay T ₂ of the time at the point A by heating circuit ON signal and the load current signal I ₁ of the delay at the rising edge. If the load circuit is disconnected, or contact abnormality such as defective, even heating circuit ON signal S ₁ is a ON, the load current signal I ₁ is to connect turned off, examples of a case where the breaking of Figure 4 As shown in the figure, the point A keeps the ON state.

The oscillation on the rising erroneous output B of the working prevention circuit 9 is at power-on the output of negative AND circuit 19 is turned on, heating on signal output of negative AND circuit S ₁ is turned on off The voltage of the output of the signal inversion circuit 18 whose output is turned on is attenuated by the time constant of the resistor R ₂ and the capacitor C ₂ connected in series to the signal inversion circuit 18.
When the terminal voltage of the capacitor becomes 0, the output of the NAND circuit 19 is turned on again, and the heating-on signal S generated at the point A is turned on.
₁ between the output of time occurring T ₂ of the from the time the input to the load current signal I ₁ flows as 0, to prevent the next stage malfunction by the output time T _2. Therefore, to transmit to the oscillation on the rising edge detection circuit signal AND circuit 20 from the heating circuit ON signals S ₁ rise time T ₃ hours delayed from the time signal of the first of the next B.

The output of the second AND circuit 21 is connected to the set (S) terminal of the reset / set flip-flop circuit (RSF / F circuit) 15 that activates the alarm device 22. The input of the AND circuit 21 and the output of the signal inversion circuit 17 for the initialization signal and the load current signal I
₁ and an exclusive OR circuit 13 of the heating circuit ON signals S _1, the output is input to the first AND circuit 20 of the output of the oscillation on the rising malfunction prevention circuit 9, thus heating circuit ON signals S ₁ There have been inputted, when no output of the load current signal I ₁ is the output of the reset-set flip-flop circuit (RSF / F circuit) 15 is turned on, the alarm device 22
Activate Further, by taking measures such as immediately stopping the work of heating the work coil at the same time as the operation of the alarm device 22, it is possible to immediately stop the occurrence of the failure of the work coil and to immediately know the abnormality of the device.

[0022] In addition, at the time of adjustment up and output setting adjustment alignment of the oscillator load, the load current signal is also OFF, the signal of the exclusive OR circuit by the exclusive OR circuit output of the switch SW ₂ Is turned off to release the apparatus.

In the embodiment of the present invention, an object to be heated is inserted into a work coil, a capacitor is connected in series to a feeder for supplying a high-frequency current to the work coil, and the inductance of the work coil and the capacitor are connected in series. Although the load circuit abnormality detection device for the series resonance type high frequency induction heating device in which the load current flowing through the work coil is increased in the resonance state has been described, the load circuit abnormality detection device according to the present invention can be used even when the power is on. Regardless, it is natural that the present invention can be applied to other power supply devices and electronic devices that detect a situation where no current is flowing to the load due to an abnormality on the load side.

[0024]

As described above, according to the present invention, the oscillation ON signal indicating that the induction heating device has been operated and the load circuit abnormality detection device for comparing and detecting the load current as the load current signal are incorporated. By outputting the alarm, it is possible to detect the abnormality of the load circuit with high reliability, and it is possible to obtain the effect that the number of defective products to be heated can be extremely reduced.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a drive circuit and a load circuit of a general series resonance type high frequency induction heating apparatus (however, an oscillation circuit and a gate circuit of a transistor are not included).

FIG. 2 is a circuit block diagram of a load circuit abnormality detection device according to the present invention.

FIG. 3 is a circuit diagram showing a load circuit abnormality detection device according to the present invention.

FIG. 4 is a time chart showing the operation of the device according to the present invention at each circuit position.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Transistor full bridge drive circuit 1a Transistor 2 Series resonance load circuit by L and C 2a Transformer for load coupling 3 Feeder part connecting output terminal and work coil 4 Current transformer (CT) for current detection 5 Smoothing circuit 6 Level Conversion circuit 6a Zener diode 7 Load circuit abnormality detection circuit (RBC circuit) 8 Initialization circuit 9 Oscillation on rising malfunction prevention circuit 10 Reset set flip-flop (RSF /
F) Simultaneous ON prevention circuit 11 Manual switch (SW ₁ ) 12 Abnormality detection circuit release switch (SW ₂ ) 13 Exclusive OR circuit (of load current signal (I ₁ ) and heating circuit ON signal (S ₁ )) Exclusive OR circuit 14 OR circuit (OR circuit) 15 Reset set flip-flop circuit (RS
F / F circuit 16, 17, 18 Signal inversion circuit 19 Negative product circuit (NAND circuit) 20 First logical product circuit (AND circuit) 21 Second logical product circuit (AND circuit) 22 Alarm device + 5V power supply INIT Initialize Circuit output signal S ₁ Heating circuit ON signal I ₁ Load current signal A Exclusive OR circuit output signal B Oscillation ON rising detection circuit signal C Inverter (17) output circuit signal S Reset set flip-flop circuit (RSF /
F circuit) Set input signal Q Abnormal signal output

Claims (1)

(57) [Claims] An apparatus for detecting an abnormality of a load circuit in a power supply device for supplying power to a work coil, comprising:
A capacitor whose one end is grounded is connected in series to the other end of the resistor connected in series to the DC power supply, and a signal that is turned on when the DC power supply is turned on is output from a connection point of the resistor and the capacitor via a signal inversion circuit. An initialization circuit, an OR circuit to which an output signal of the initialization circuit, and an output signal from the DC power supply via a manual switch are input in parallel, and an AC load current flowing to a drive circuit of the power supply device. An exclusive OR circuit in which a load current signal whose operation level is determined by comparison with the Zener voltage and a heating circuit ON signal of the power supply device is input in parallel, the heating circuit ON signal, A capacitor having one end grounded is connected in series to the other end of the resistor connected in series via a signal inverting circuit connected in series to the heating circuit ON signal, and the capacitor is connected to the capacitor. An oscillation-on rising malfunction prevention circuit for preventing simultaneous ON consisting of a NOT product circuit in which a signal from a connection point of the inverter is input in parallel, an output signal of the NOT product circuit of the malfunction prevention circuit, and a switch A first AND circuit to which an output signal of the exclusive OR circuit is input in parallel, an output signal of the first AND circuit, and an output signal of the OR circuit via a signal inverting circuit again. A simultaneous ON prevention circuit including a second AND circuit input in parallel, an output of the second AND circuit is connected to a set terminal, and an output of the OR circuit is connected to a reset terminal. A reset-set flip-flop circuit that outputs an ON signal when the power supply device is abnormal, wherein the simultaneous ON-prevention circuit includes a signal input to the reset terminal and an input signal to the set terminal. The reset set flip-flop circuit is reset when the power supply device is turned on while preventing simultaneous signals from being turned on, and the heating circuit on signal is turned on and the malfunction prevention circuit is turned on. A load circuit abnormality detecting device for detecting an abnormality in the load circuit by turning on the set terminal when the load current signal does not exist even after the detection.