JPH08140255A - Defective connection detecting circuit - Google Patents

Abstract

PURPOSE: To detect defective connection of a connector to which a current transformer for detecting a circuit current is connected. CONSTITUTION: Secondary side terminals 9a, 9b of a current transformer 9 are connected to connection terminals 20b, 20c of a connector 20. Voltage, obtained by full-wave rectifying a secondary current of the current transformer 9 by diodes D1 to D4 , is input to a negative input terminal- of a comparator 22. A DC power supply E is input to a positive input terminal+ of the comparator 22 through a series circuit of a connection terminal 20a, short-circuit line 21 and a connection terminal 20d. The comparator 22 outputs defective connection detecting signal #NG when the voltage obtained by full-wave rectification is increased to reference voltage Vref or more.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a connection failure detection circuit for detecting connection failure of a connector connecting a current transformer.

[0002]

2. Description of the Related Art An electromagnetic cooker, which is a high-frequency heating device, is provided with a current transformer that detects a circuit current, and when an overcurrent is detected, it turns on and off to supply current to an induction heating coil. Stop the operation of the switching element that is
The current of the switching element is cut off to protect the switching element from overcurrent. Further, the current transformer is connected to the control circuit via a detachable connector.

[0003]

By the way, in such an electromagnetic cooker, the assembled state is carefully checked after manufacturing and then shipped, but in the unlikely event that a connection failure occurs in the connector to which the current transformer is connected. If it occurs, the overcurrent of the circuit cannot be detected, the operation of the switching element that is on and off to supply current to the induction heating coil cannot be stopped, and the switching element can be damaged. This may occur and may induce a high voltage on the secondary side of the current transformer to damage the current transformer.

Therefore, when starting the operation, the electromagnetic cooker may be heated at an extremely low output to check whether the output voltage of the current transformer corresponding to the extremely low output can be obtained. In that case, a circuit for checking must be added, which makes the circuit complicated and increases the cost.
Therefore, it does not employ a circuit for such checking. Also, in order to prevent high voltage from being induced on the secondary side of the current transformer, it is possible to add a dummy resistor or varistor between the secondary terminals, but the versatility of the current transformer is lost. In addition, there is a problem such as an increase in size.

In view of the above problems, it is an object of the present invention to provide a connection failure detection circuit that can reliably detect a connection failure when the connector connecting the current transformer has a connection failure. .

[0006]

A connection failure detection circuit according to a first aspect of the present invention compares a current transformer for detecting a circuit current with an output voltage of the current transformer and a reference voltage provided by a DC power source. A comparator is provided to detect an overcurrent, and a connection failure detection for detecting a connection failure of a connector interposed in the connection circuit between the current transformer and the DC power supply and the comparator. In the circuit, the DC power supply and a terminal to which the reference voltage of the comparator is to be input, and the current transformer and the other input terminal of the comparator to which the output voltage of the current transformer is to be input are common. It is characterized in that it is configured to be connected by a connector.

A connection failure detection circuit according to a second aspect of the present invention is a connection failure detection circuit for detecting a connection failure of a connector to which a current transformer for detecting a circuit current is connected, wherein the output of the current transformer is output via the connector. A comparator for inputting a voltage, a direct current power supply for giving a reference voltage to be input to the comparator, and a resistor interposed between the output side of the comparator and the ground potential. It is characterized in that it is provided to the output side of the comparator through a connector.

In the connection failure detection circuit according to the third aspect of the present invention, a plurality of connection terminals are arranged in parallel in one direction on the connector, and one connection terminal located on the outermost side is located on the DC power source and the outermost position. Connect the other connection terminal to the terminal to input the reference voltage of the comparator, or the output terminal of the comparator, the one and the other connection terminals are connected in series, one connection terminal and the other The current transformer is connected to a connection terminal located inside the connection terminal.

In the connection failure detection circuit according to the fourth aspect of the present invention, the connector has a plurality of connection terminals arranged in parallel in one direction, and one connection terminal located outside two connection terminals to which the current transformer is connected. A terminal is connected to the DC power source, and the other connection terminal located outside is connected to a terminal for inputting a reference voltage to the comparator, or an output terminal of the comparator, and the one connection terminal and the other connection terminal. Are connected in series.

[0010]

According to the first aspect of the invention, the current transformer and the DC power source are connected through the common connector to the terminal to which the current transformer of the comparator is connected and the terminal to which the reference voltage is input. When the output voltage of the current transformer exceeds the reference voltage, the comparator outputs an overcurrent detection signal. When the connection failure occurs in the connector, the reference voltage is not input to the comparator, the output of the comparator is inverted, and the connection failure detection signal is output. Thereby, the overcurrent can be detected. In addition, the connection failure of the connector can be reliably detected.

In the second invention, the current transformer and the DC power source are separately connected to the input terminal and the output terminal of the comparator through the common connector. When the output voltage of the current transformer exceeds the reference voltage, the output of the comparator is inverted and the overcurrent detection signal is output. If the connector is not connected properly, the DC power supply and the output side of the comparator will be disconnected and the voltage on the output side of the comparator will be pulled down via a resistor, and the voltage on the output side of the comparator will change and detect a connection failure. Output a signal. Thereby, the overcurrent can be detected. In addition, the connection failure of the connector can be reliably detected.

In the third aspect of the invention, the output voltage of the current transformer and the reference voltage or the voltage of the DC power supply are connected to one terminal of the comparator and the other terminal through a common connector in which a plurality of connection terminals are arranged in parallel in one direction. Input to each terminal separately or give to the output terminal of the comparator. When the output voltage of the current transformer exceeds the reference voltage,
The output of the comparator is inverted and an overcurrent detection signal is output.
When the connector is poorly connected, the series circuit of the one outermost connection terminal and the other outermost connection terminal is cut off. Then, the reference voltage is no longer input to the comparator, the output of the comparator is inverted and a connection failure detection signal is output, or the DC power supply and the output side of the comparator are disconnected and the voltage on the output side of the comparator becomes It pulls down and outputs a connection failure detection signal. Thereby, the overcurrent can be detected. In addition, the connection failure of the connector can be detected more accurately.

According to the fourth aspect of the invention, the output voltage and the reference voltage of the current transformer or the DC power supply are connected to one terminal and the other terminal of the comparator through a common connector in which a plurality of connection terminals are arranged in parallel in one direction. To the output terminal of the comparator. When the output voltage of the current transformer exceeds the reference voltage, the output of the comparator is inverted and the overcurrent detection signal is output. If the common connector is not connected properly, one of the connection terminals located outside the connection terminal connecting the current transformer and the other connection terminal located outside the connection terminal connecting the current transformer The series circuit of is cut off. And the reference voltage is no longer input to the comparator, the voltage on the output side of the comparator changes and outputs a connection failure detection signal, or the DC power supply that gives the reference voltage and the output side of the comparator are disconnected, The voltage on the output side of the comparator is pulled down and a connection failure detection signal is output. Thereby, the overcurrent can be detected. In addition, the connection failure of the connector can be detected more accurately.

[0014]

The present invention will be described in detail below with reference to the drawings showing the embodiments thereof. FIG. 1 is a block diagram showing the configuration of an electromagnetic cooker provided with a connection failure detection circuit according to the present invention. The three-phase AC power supply 1 is connected to the AC input terminals 2au, 2av, 2aw of the rectifier bridge 2, and the smoothing capacitor 3 is interposed between the output terminals 2b and 2c. In the smoothing capacitor 3, a series circuit of a switching element 4 and a switching element 5,
A series circuit of the resonance capacitor 6 and the resonance capacitor 7 is connected in parallel. A heating coil 8 is interposed between the connection between the switching elements 4 and 5 and the connection between the resonance capacitors 6 and 7. In the middle of the circuit connecting the heating coil 8, a current transformer 10 for detecting the current flowing through the heating coil 8.
Is provided.

In the middle of the circuit connecting the three-phase AC power supply 1 and the AC input terminal 2aw of the rectifying bridge 2, the rectifying bridge 2 is provided.
A current transformer 9 for detecting the input current of Current transformer 9
Is output to the connection failure detection circuit 15 having an input overcurrent detection function, and is input to one terminal of the error comparator 12 via the connection failure detection circuit 15. The detection output of the connection failure detection circuit 15 is input to the drive circuit 14 and the abnormality display circuit 17.
The output current of the current transformer 10 is input to the connection failure detection circuit 16 having a coil overcurrent detection function, and the detection output thereof is input to the drive circuit 14 and the abnormality display circuit 17. Input current setting device
The output of 11 is input to the other terminal of the error comparator 12, and the comparison output of the error comparator 12 is input to the voltage controlled oscillator 13. The oscillation output of the voltage controlled oscillator 13 is input to the drive circuit 14, and the output of the drive circuit 14 is input to the gates of the switching elements 4 and 5.

Next, the operation of this electromagnetic cooker will be described. A three-phase input current flows from the three-phase AC power supply 1 to the rectification bridge 2 for full-wave rectification. The current transformer 9 detects this input current and inputs the output current to the connection failure detection circuit 15. Then, the smoothing capacitor 3 is charged with the rectified DC voltage. Here, when a predetermined input current value is set in the input current setter 11, the error comparator 12 sets the set input current value,
The input current detected by the current transformer 9 is compared in magnitude, and the comparison result is input to the voltage controlled oscillator 13. Thereby,
The voltage controlled oscillator 13 oscillates the detected input current at an oscillation frequency corresponding to the set input current value according to the error between the set input current value and the detected input current, and The oscillation output is input to the drive circuit 14, and the drive signal output from the drive circuit 14 causes the switching elements 4 and 5 to alternately turn on and off according to the oscillation frequency. As a result, a resonance current alternately flows in the resonance circuit formed by the heating coil 8 and the resonance capacitor 6 and the resonance circuit formed by the heating coil 8 and the resonance capacitor 7, so that a heating output is obtained in the heating coil 8 and mounted on the heating coil 8. The pan, not shown, will be heated at high frequency. The current transformer 10 detects the high frequency current flowing through the heating coil 8 and inputs it to the connection failure detection circuit 16.

On the other hand, the output current detected by the current transformer 9 is input to the connection failure detection circuit 15. Then, the heating output is obtained from the heating coil 8 according to the set input current value. By the way, when the input current of the rectifying bridge 2 becomes an overcurrent, an overcurrent detection signal is input from the connection failure detection circuit 15 to the drive circuit 14, the drive signal of the drive circuit 14 is cut off, and the switching element 4 , 5 are both turned off, the currents flowing through the switching elements 4, 5 are cut off, damages due to the overcurrents of the switching elements 4, 5 are prevented in advance, and the abnormality display circuit 17 indicates that the input current has become an overcurrent. To display.
If the current flowing through the heating coil 8 becomes an overcurrent, the connection failure detection circuit 16 outputs an overcurrent detection signal to the drive circuit.
It is input to 14, and the switching elements 4 and
No damage caused by overcurrent of No. 5 is prevented, and it is indicated that the current of the heating coil 8 has become overcurrent. In this way, the switching element is protected from overcurrent. In addition, current transformer 9,10
When a connection failure of the connector (not shown) connected to is detected, a connection failure detection signal is input to the drive circuit 14, both switching elements 4 and 5 are turned off, and the damage due to the overcurrent described above is prevented in advance. Prevents generation of high voltage generated in the current transformer.

FIG. 2 is a block diagram showing the configuration of the connection failure detection circuit 15.
It is a lock figure. The secondary side terminals 9a and 9b of the current transformer 9 are connected to each other.
Connection terminals 20a, 20b, 20c, which are arranged in parallel in one direction on the connector 20.
Separately connect to the connection terminals 20b and 20c located inside 20d.
Continued. Connection terminals 20a and 20d located on the outermost side
Are short-circuited by the short-circuit line 21. Connection terminal 20a has resistance R ₁
Is connected to the DC power source E via. Connection terminal 20d is compared
Connected to the positive input terminal + of the instrument 22 and the positive input terminal + is a resistor R
₂Grounded through. Connection terminal 20b is diode D₁
Anode and diode D₂Connected to the cathode of
It Connection terminal 20c is diode D₃The anode and the die
Aether D_FourConnected to the cathode of. diode
D₁, D₃Each cathode of is connected in common, diode
D₂, D_FourThe anodes of are commonly connected. diode
D₁, D₃The cathode common connection of the resistor R₃, Conde
Connected to each terminal of sensor C and the negative input terminal of comparator 22.
Be done. Diode D₂, D_FourThe common anode connection of
Resistance R₃, The other end of the capacitor C, and the resistor R
_FourConnected to the DC power source E via a resistor R_FiveConnect through
Ground. The negative input terminal − of the comparator 22 is one terminal of the error comparator 11.
The output terminal of the comparator 22 is connected to the drive circuit 14 (Fig.
1)).

In FIG. 2, the DC power source E is connected to the positive input terminal + of the comparator 22 via the resistor R ₁ without providing the connection terminals 20a and 20d of the connector 21 in the prior art, and the current transformer is connected. The electromagnetic cooker is provided with a circuit configured to detect the overcurrent of the input current of the rectifying bridge 2 by the output current of 9.
The present invention uses the circuit to configure a connection failure detection circuit that prevents damage to the switching element due to connection failure of the connector 20 and high voltage generated in the current transformer.

Next, the operation of the connection failure detection circuit will be described with reference to FIGS. 3 and 4 showing timing charts of the voltage related to the output current of the current transformer, the overcurrent detection signal and the voltage of each part. The voltage of the DC power source E is divided by the resistors R ₁ and R _2, and the divided reference voltage V _ref is the comparator 22.
Input to the positive input terminal + of. On the other hand, the voltage of the DC power source E is divided by the resistors R ₄ and R _5, and the offset voltage V _{OFS, which} is the _divided voltage, becomes the diodes D ₁ , D ₂ , D ₃ , D.
The charging voltage V _C of the capacitor C is superimposed on the voltage rectified by ₄ , and the charging voltage V _C is input to the negative input terminal − of the comparator 22. Then, the reference voltage V _ref and the offset voltage V _OFS become the voltage levels shown in FIG.

On the other hand, the current transformer 9 detects the input current of the rectifying bridge 2 (see FIG. 1), and the output current thereof is full-wave rectified by the diodes D ₁ , D ₂ , D ₃ and D ₄ , and the whole current is rectified. The capacitor C is charged by the wave-rectified DC current, and the charging voltage V _C is input to the negative input terminal − of the comparator 22. As a result, the comparator 22 compares the charging voltage V _C with the reference voltage V _ref . When the charging voltage V _C is equal to or lower than the reference voltage V _ref , the comparison output of the comparator 22 becomes H level as shown in FIG. 3 (b), and the overcurrent is not detected.

By the way, when the output current of the current transformer 9 increases and the charging voltage V _C of the capacitor C rises as shown in FIG. 3 (a), when the charging voltage V _C exceeds the reference voltage V _ref. As shown in FIG. 3 (b), the comparison output of the comparator 22 is inverted to the L level, and the L level is maintained while the charging voltage V _C is equal to or higher than the reference voltage V _ref. The detection signal #OC will be output.

By the way, when the connection of the connector 20 is not perfect and a connection failure occurs, that is, when the connector 20 is not connected, the voltage of the DC power source E is supplied to the comparator 22 via the connector 20. Input to the positive input terminal + is stopped and the reference voltage V _ref becomes zero. On the other hand, the negative input terminal-of the comparator 22 has an offset voltage V _OF as shown in FIG.
Only _S is entered. Therefore, the charging voltage V _C becomes equal to or higher than the reference voltage, the comparison output of the comparator 22 remains inverted to the L level, and the comparator 22 outputs the connection failure detection signal # of the L level as shown in FIG. 4 (b). NG is output, and the poor connection of the connector 20 is detected.

FIG. 5 is a block diagram showing the configuration of the connection failure detection circuit 16. The secondary side terminals 10a, 10b of the current transformer 10 are the connection terminals 20a, 20b, 20 arranged side by side in the connector 20 in one direction.
It is separately connected to the connection terminals 20b and 20c located inside c and 20d. Connection terminals 20a and 20d located on the outermost side
And are short-circuited by the short-circuit line 21. Connection terminal 20a has resistance R
It is connected to the DC power source E via ₁₁ . The connection terminal 20d is connected to the positive input terminal + of the first comparator 23. Connection terminal 20
A resistor R ₁₂ is interposed between b and 20c, and the connection terminal 20c is grounded. The connection terminal 20b is connected to the negative input terminal − of the comparator 23 and the positive input terminal + of the second comparator 24. Negative DC power source -E through a series circuit of a connection point between the positive input terminal + of the comparator 23 and the connecting terminal 20d is a resistor R ₁₃ and the resistor R ₁₄
Connected to Further, the connection midpoint between the resistors R ₁₃ and R ₁₄ is connected to the negative input terminal − of the comparator 24. Comparator 23, 24
Output terminals are commonly connected and connected to the drive circuit 14 (see FIG. 1).

Next, the operation of the connection failure detection circuit configured as described above will be described with reference to FIGS. 6 and 7 showing timing charts of the voltage related to the output current of the current transformer, the overcurrent detection signal, and the voltage of each part. DC power supply E and negative DC power supply −
And voltage resistance R ₁₁ between the E, and the resistor R _13, is divided by the resistors R _14, the voltage serving as the reference voltage + V _ref connection point between the resistor R ₁₁ and R ₁₃ is a comparator 23 The reference voltage −V _{ref, which} is the voltage at the connection intermediate point between the resistor R ₁₃ and the resistor R ₁₄ , is input to the positive input terminal +, and is input to the negative input terminal − of the comparator 24.

On the other hand, the current transformer 10 is detects a current flowing through the heating coil 8 (see FIG. 1), flows an output current to the resistor R _12, the terminal voltage V _T is a comparator that occurs in the resistor R ₁₂
It is input to the negative input terminal − of 23 and the positive input terminal + of the comparator 24. As a result, the comparator 23 has the positive reference voltage + V _ref
Is compared with the terminal voltage V _T, and the comparator 24 compares the negative reference voltage −V _ref with the terminal voltage V _T. Then, as shown in FIG. 6A, when the positive and negative voltage levels of the terminal voltage V _T are within the positive and negative reference voltages + V _ref and −V _ref , respectively, the comparators 23 and 24 are operated. Each comparison output is shown in Fig. 6 (b).
As shown in FIG. 5, both become H level, and overcurrent is not detected.

By the way, the output current of the current transformer 10 increases
Resistance R₁₂Terminal voltage V_TAs shown in Fig. 6 (a)
Rise, terminal voltage V_TThe voltage level on the positive side of
Pressure + V _refAfter that, the comparison output of the comparator 23 is as shown in FIG.
As shown in (b), it is inverted to L level and the terminal voltage V_TIs positive
Side reference voltage + V_refContinue L level for a certain period
Then, the comparator 23 outputs the L level overcurrent detection signal #OC.
Will be done. Also, the terminal voltage V_TNegative voltage level of
Is the negative reference voltage -V_refIf the following occurs, compare
The comparison output of the device 24 is inverted to L level,
The L level overcurrent detection signal #OC is output.

By the way, when the connector 20 is not in the connected state, the positive input terminal + of the comparator 23 and the comparator
The voltage of the negative DC power supply −E is input to the negative input terminal − of 24. Further, the terminal voltage V _T is not generated in the resistor R ₁₂ and becomes 0V. As a result, the terminal voltage V _T and the reference voltage + V _ref change as shown in FIG. 7 (a). As a result, the comparison output of the comparator 23 is inverted to the L level and the comparison output of the comparator 24 is inverted to the H level, and the comparison output of the comparator 23 causes the connection failure detection signal #NG of the L level shown in FIG. It is output and the poor connection of the connector 20 is detected.

Further, when a pair of connectors are connected in a non-parallel state and only the outermost connection terminal 20a or 20d has a poor connection, the reference voltages + V _ref , -V are provided.
_ref changes to the voltage of the negative DC power supply −E, and the terminal voltage V _T
Is input to the comparators 23 and 24, and in this case also, the comparison output of the comparator 23 is inverted to the L level and the connection failure detection signal #NG of the L level is output.

FIG. 8 is a block diagram showing the configuration of another embodiment of the connection failure detection circuit according to the present invention. Current transformer CT 2
The secondary terminals CTa, CTb are connected to the connection terminals 20a, 20b, 20c, 20d of the connection terminals 20a, 20b, 20c, 20d arranged side by side in the connector 20. The connection terminals 20a and 20d are connected by the short-circuit line 21, and the connection terminal 20a is connected to the DC power supply V _CC . A resistor R _L is interposed between the connection terminals 20b and 20c, and the connection terminal 20b is connected to the negative input terminal − of the comparator CMP. The connection terminal 20c is connected to the DC power supply V _CC via the resistor R ₂₁ ,
Connection point between the connecting terminal 20c and the resistor R ₂₁ is grounded through a resistor R _22. The resistors R ₂₁ and R ₂₂ are selected so that R ₂₁ ≈R ₂₂ , and the offset voltage V _{OFS, which} is a _divided voltage by the resistors R ₂₁ and R ₂₂ , is approximately half the voltage of the DC power supply V _CC . DC power supply V _CC is grounded through a series circuit of a resistor R ₂₃ and the resistor R _24, the connection portion of the resistor R ₂₃ and R ₂₄ comparator
Connected to positive input terminal + of CMP. The connection terminal 20d of the connector 20 is grounded via the resistor R _G , and the non-grounded side terminal of the resistor R _G is connected via the resistor R _P to the output terminal CMP _{0 of the} comparator CMP _0.
Connected to The overcurrent detection signal #OC and the connection failure detection signal #NG are output from the output terminal CMP ₀ of the comparator CMP.

Next, the operation of the connection failure detection circuit configured as described above will be described with reference to FIG. 9 showing a timing chart of the voltage and overcurrent detection signal related to the output current of the current transformer. The voltage of the DC power supply V _CC passes through the resistor R _P to the comparator CM
It is given to the output terminal CMP _{0 of} P, and the output terminal CMP ₀ becomes H
Become a level. On the other hand, when the current transformer CT detects the current, the output current of the current transformer CT is flowing through the resistor R _L, the terminal voltage V _T of the resistor R _L to be varied in accordance with the output current of the current transformer CT Become. The terminal voltage V _T is an offset voltage V _OFS which is a voltage obtained by dividing the voltage of the DC power supply V _CC by resistors R ₂₁ and R _22.
Is superimposed and the terminal voltage V _T to which the offset voltage V _OFS is applied is input to the negative input terminal − of the comparator CMP, and the voltage of the DC power supply V _CC is applied to the positive input terminal + of the resistors R ₂₃ and R _24. The reference voltage V _{ref divided by} is input. Further, the offset voltage V _{OFS obtained by} dividing the voltage of the DC power supply V _CC by the resistors R ₂₁ and R ₂₂ is applied to one terminal of the resistor R _L , and the offset voltage V _OFS is applied to the terminal voltage V _T. 9 (a)
As shown in, the terminal voltage V _T changes based on the offset voltage V _OFS .

The comparator CMP receives the input terminal voltage V
_When the terminal voltage V _T is less than or equal to the reference voltage V _ref by comparing _T with the reference voltage V _ref , the comparison output of the comparator CMP becomes the H level as shown in FIG. Not detected. By the way, the output current of the current transformer CT increases, and
As shown in FIG. 9, when the terminal voltage V _T becomes equal to or higher than the reference voltage V _ref , the comparison output of the comparator CMP is inverted and becomes L level as shown in FIG. 9 (b). And the terminal voltage V _T is the reference voltage V
_The L level is continued for a certain period of _ref or more, and the overcurrent detection signal #OC is output from the comparator CMP.

When the connector 20 is not connected, the terminal voltage V _T is not input to the negative input terminal-of the comparator CMP, and the voltage of the DC power supply V _CC is cut off by the connector 20. Output terminal CMP of comparator CMP
₀ becomes the ground voltage via the series circuit of the resistors R _P and R _G. As a result, the voltage of the output terminal CMP ₀ of the comparator CMP changes to the L level, and the L level connection failure detection signal #NG.
Will continue to be output.

As a result, the overcurrent detection signal #OC and the connection failure detection signal #NG can be output, the switching elements 4 and 5 are damaged due to the connection failure of the current transformer CT, and the high current generated in the current transformer CT. Voltage can be prevented in advance. In addition, although the case where the present invention is applied to the electromagnetic cooker has been described in the present embodiment, it is an example, and the same effect can be obtained even when applied to other than the electromagnetic cooker.

[0035]

As described above in detail, according to the first aspect of the invention, the circuit for detecting the overcurrent which is already provided is utilized,
The connection failure of the connector can be reliably detected at low cost.

According to the second aspect of the present invention, the connection failure of the connector connecting the current transformer can be reliably and inexpensively detected by directly changing the output side of the comparator.

According to the third aspect of the present invention, when one of the connection terminals located on the outermost side of the plurality of connection terminals arranged in parallel in one direction or the other connection terminal has a connection failure, the connection failure detection signal is output. Can be output, and the connection failure state can be detected even if connection failure occurs at one end of the connector.

According to the fourth invention, either one or the other of the connecting terminals located outside the connecting terminal connecting the current transformers of the plurality of connecting terminals arranged in parallel in one direction. In case of poor connection, a poor connection detection signal can be output,
The connection failure detection circuit according to the present invention has excellent effects such as being able to detect a connection failure state even if a connection failure occurs at one end of the connector.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of an electromagnetic cooker to which a connection failure detection circuit according to the present invention is applied.

FIG. 2 is a block diagram showing a configuration of a first embodiment of a connection failure detection circuit.

FIG. 3 is a timing chart of a voltage and an overcurrent detection signal related to an output current of a current transformer.

FIG. 4 is a state diagram of an offset voltage and a connection failure detection signal.

FIG. 5 is a block diagram showing a configuration of a second embodiment of the connection failure detection circuit.

FIG. 6 is a timing chart of a voltage and an overcurrent detection signal related to an output current of a current transformer.

FIG. 7 is a state diagram of a voltage and a connection failure detection signal related to an output current of a current transformer.

FIG. 8 is a block diagram showing a configuration of a third embodiment of the connection failure detection circuit according to the present invention.

FIG. 9 is a timing chart of a voltage and an overcurrent detection signal related to an output current of a current transformer.

[Explanation of symbols]

 9, 10 Current transformer 20 Connector 20a, 20b, 20c, 20d Connection terminal 21 Short circuit wire 22 Comparator E DC power supply −E Negative power supply CT Current transformer CMP Comparator

Claims (4)

[Claims] 1. A current transformer for detecting a circuit current, and a comparator for comparing the output voltage of the current transformer and a reference voltage given by a DC power source to detect overcurrent. Yes, in a connection failure detection circuit that detects a connection failure of a connector interposed in the connection circuit between the current transformer and the DC power supply and the comparator, input the reference voltage of the DC power supply and the comparator And a terminal to be connected, and the current transformer and the other input terminal of the comparator to which the output voltage of the current transformer is to be input are configured to be connected by a common connector. Defect detection circuit. 2. A connection failure detection circuit for detecting a connection failure of a connector to which a current transformer for detecting a circuit current is to be connected, comprising: a comparator to which the output voltage of the current transformer is input via the connector; The comparator is provided with a direct current power source for giving a reference voltage to be input to the comparator, and a resistor interposed between the output side of the comparator and the ground potential, and the voltage of the direct current power source is supplied to the comparator through a connector. A connection failure detection circuit characterized by being provided to the output side. 3. A plurality of connection terminals are arranged side by side in one direction on the connector, one connection terminal located on the outermost side is the DC power supply, and the other connection terminal located on the outermost side is the comparator. Connected to the terminal to which the reference voltage of, or the output terminal of the comparator is connected, the one and the other connecting terminals are connected in series, and the connecting terminal located inside the one connecting terminal and the other connecting terminal The connection failure detection circuit according to claim 1 or 2, wherein the current transformer is connected to the current transformer. 4. A plurality of connection terminals are arranged side by side in one direction on the connector, and one connection terminal located outside the two connection terminals connected to the current transformer is connected to the DC power source and outside. The other connecting terminal located is connected to a terminal for inputting a reference voltage to the comparator, or an output terminal of the comparator, and the one connecting terminal and the other connecting terminal are connected in series. The connection failure detection circuit according to claim 1 or 2.