JPH05175620A - Detector of abnormality of electronic component - Google Patents

Abstract

PURPOSE:To make it possible to cope with abnormality of a plurality of electronic components mounted on a wiring circuit board, by making an abnormality signal be outputted when a DC voltage level of a detecting pattern changes beyond a prescribed level. CONSTITUTION:A detection signal corresponding to a voltage impressed on a circuit pattern 34 is generated in detecting patterns 36a and 36b. This detection signal is given to a filter circuit 38. A high-frequency component contained in the detection signal is removed by the filter circuit 38 and the signal is amplified in an amplifier circuit 39 and then given to a hold circuit 40. In the hold circuit 40, the voltage level of the detection signal is compared with a reference voltage. When the voltage level of the detection signal comes to exceed the reference voltage, an abnormality signal is outputted from the hold circuit 40 to a control circuit 35. As the result, the control circuit 35 stops a switching operation. Therefore, the switching operation by a switching element 31 is stopped and induction heating by a magnetic field generating coil 29 is stopped.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an abnormality detecting apparatus for electronic components which is mounted on a printed circuit board and detects abnormality of electronic components connected to each other by a circuit pattern.

[0002]

2. Description of the Related Art Conventionally, for example, an electromagnetic cooker has a structure for heating a cooking utensil by electromagnetic induction of a magnetic field generating coil, so that a red heating part or a flame is not exposed to the outside and is used as a safe cooking device. It has been.

However, when the electronic component cooling fan provided in the electromagnetic cooker is handled improperly, such as when the exhaust passage is blocked by an obstacle, the temperature inside the main body becomes abnormal. And the life of electronic parts is significantly reduced. Moreover, when used in such an unsuitable state for a long period of time, the electronic components generate abnormal heat, and in the worst case,
Electronic components may be burnt and may emit smoke or ignite. In particular, an electromagnetic cooker is configured to generate a high frequency by using a switching element such as a high frequency generating transistor which theoretically operates only in direct current. Therefore, a commercial AC voltage is temporarily generated by using a rectifying circuit such as a smoothing capacitor. Since DC conversion is performed, a large current flows through the rectifier circuit and heat is easily generated. In addition to the switching element for generating high frequency, a large current also flows through the resonance capacitor, the magnetic field generation coil, etc., so that those electronic components are also likely to generate heat. Therefore, it is desirable to provide a heat protection device or an overcurrent protection device such as a current fuse as a safety device for electronic parts that easily generate heat. Was difficult from the perspective of.

Therefore, among the parts that easily generate heat, in particular, the heat protection device is attached only to the switching elements which are extremely weak against temperature and overcurrent and need protection in terms of the function of the product. Is.

FIG. 5 shows an example of an electric circuit of an electromagnetic cooker provided with a heating protection device. In FIG. 5, the commercial AC power supply 1 is connected to a power supply filter 4 and a fan motor 5 via a power supply fuse 2 and a power supply switch 3.
The power supply filter 4 outputs the AC voltage to the rectifier 6 with noise removed. The rectifier 6 converts alternating current into direct current (pulsating flow) and outputs it. The choke coil 7 and the smoothing capacitor 8 rectify the direct current from the rectifier 6 into a stabilized direct current. The switching element 9 energizes the resonance circuit of the magnetic field generating coil 10 and the smoothing capacitor 11 in the ON state. Control circuit 1
2 turns on / off the switching element 9 in a predetermined cycle. Therefore, a high-frequency current flows through the magnetic field generating coil 10 due to the switching operation of the control circuit 12, so that a magnetic field is generated from the magnetic field generating coil 10 to heat the cooking utensil. Incidentally, 13 is a diper diode. The electronic components are mounted on a wiring circuit board (not shown) and are connected to each other by a wiring pattern.

Here, a heating protection device 14 is attached to the switching element 9. The output terminal of the heating protection device 14 is interposed in the AC power supply line, and opens the AC power supply line when the temperature exceeds the set temperature. Therefore,
When the switching element 9 abnormally generates heat, the heating protection device 14 operates and power supply is stopped, so that it is possible to prevent the switching element 9 from abnormally generating heat and burning.

[0007]

However, in the case of the above-mentioned conventional structure, although the abnormal heat generation of the switching element 9 can be dealt with, a resonance capacitor 11 and a smoothing capacitor through which a large current flows like the switching element 9 can be dealt with. The problem that abnormal heat generation of other high-voltage electronic parts such as No. 8 cannot be detected and the parts are burnt out remains as an unsolved problem.

The present invention has been made in view of the above circumstances, and an object thereof is to provide an abnormality detecting device for electronic parts capable of dealing with abnormalities of a plurality of electronic parts mounted on a printed circuit board. It is in.

[0009]

SUMMARY OF THE INVENTION The present invention provides an abnormality detecting apparatus for electronic components, which detects abnormality of electronic components mounted on a printed circuit board and connected to each other by a circuit pattern.
When a detection pattern which is formed on the printed circuit board and is opposed to the circuit pattern with a predetermined gap is provided, and the DC voltage level of the detection pattern fluctuates by a predetermined level or more from the DC voltage level when the electronic component is normal. Is provided with an abnormality detecting means for outputting an abnormality signal.

[0010]

The circuit pattern is coupled to the detection pattern with a predetermined capacitance, and a predetermined insulation resistance is generated between them. Therefore, when the electronic circuit is normal, the DC voltage level of the detection pattern is maintained at the voltage level determined by the capacitance and the insulation resistance.

When an abnormality occurs in one of the electronic parts connected by the circuit pattern, the capacitance and insulation resistance between the detection pattern and the circuit pattern fluctuate. As a result, the DC voltage level of the circuit pattern changes from the normal level, and therefore the abnormality detecting means outputs the abnormality signal when the DC voltage level of the detection pattern changes by a predetermined level or more. Therefore, when an abnormality signal is output from the abnormality detecting means, it is possible to prevent the electronic component from being burned by cutting off the power supply to the printed circuit board.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to a printed circuit board of an electromagnetic cooker will be described below with reference to FIGS.
FIG. 1 schematically shows the whole electric circuit. This Figure 1
In, the commercial AC power supply 21 is connected to the power supply filter 24 and the fan motor 25 via the temperature fuse 22 and the power supply switch 23. The power filter 24 is the rectifier 2
It is connected to the input terminal 6 and outputs a direct current (pulsating current) to the rectifier 26. The output terminal of the rectifier 26 is connected to the choke coil 27 and the smoothing capacitor 28. The common connection point between the choke coil 27 and the smoothing capacitor 28 is the magnetic field generating coil 29 and the resonance capacitor 30.
It is connected to the earth line via the parallel circuit and the switching element 31. A diper diode 32 is connected in parallel to the switching element 31.

In this case, the various electronic components are mounted on the front surface of the printed circuit board 33 and are connected to each other by the circuit pattern 34 formed on the back surface.

The control circuit 35 is composed of an oscillation circuit, a PWM circuit, a load detection circuit, an output setting circuit, a transistor drive circuit (all not shown), etc., and sends a switching signal of a set cycle to the switching element 31. Output.

On the other hand, on the surface of the printed circuit board 33, detection patterns 36a and 36b are formed along the circuit pattern 34. Here, as shown in FIG. 1, the detection pattern 36a is formed along the circuit pattern 34 that connects the electronic components for the power supply circuit to each other, and the detection pattern 36b.
Are formed along the circuit pattern 34 that connects the high-frequency generating electronic components to each other. That is, in FIG. 3 showing the longitudinal section of the printed circuit board 33, the circuit pattern 3 for connecting the electronic components to each other is provided on the back surface of the printed circuit board 33.
4 is formed, and the detection patterns 36a, 3 that face the circuit pattern 34 with a gap of a predetermined size.
6b is formed on the surface of the printed circuit board 33.

As shown in FIG. 1, the circuit patterns 36a and 36b are connected to the abnormality detecting means 37, and the output from the abnormality detecting means 37 is given to the control circuit 35.

Here, the abnormality detecting means 37 comprises a filter circuit 38, an amplifier circuit 39, and a hold circuit 40. FIG. 2 shows an electric circuit of each of these circuits 38, 39 and 40. That is, in the input portion 38a of the filter circuit 38, the detection pattern 36b is connected to the ground line via the series circuit of the resistors 41 and 42, and the detection pattern 36a is connected to the common connection point of the resistors 41 and 42. The non-inverting input terminal of the operational amplifier 43 is connected to the detection pattern 36b via the series circuit of the resistors 44 and 45, and is also connected to the ground line via the capacitor 46. The inverting input terminal of the operational amplifier 43 is a capacitor 47
Is connected to the common connection point of the resistors 44 and 45 via, and is also connected to the output terminal of the operational amplifier 43.
The output terminal of the operational amplifier 43 is a diode 4 of the polarity shown.
8 and a resistor 49 are connected to the earth line through a series circuit. The common connection point of the diode 48 and the resistor 49 is connected to the ground line via the capacitor 50, and the common connection point becomes the output point of the filter circuit 38.

In the amplifier circuit 39, the non-inverting input terminal of the operational amplifier 51 is connected to the output point of the filter circuit 38. The inverting input terminal of the operational amplifier 51 has resistors 52 and 53 connected in series between the power supply line and the ground line.
Of the amplifier circuit 39, and the output terminal of the operational amplifier 51 is connected to the output terminal of the operational amplifier 51 via the resistor 54.

In the hold circuit 40, the operational amplifier 5
The non-inverting input terminal of No. 5 is connected to the output point of the amplifier circuit 39 via the diode 56 of the illustrated polarity, and is connected to the output terminal of the operational amplifier 55 via the resistor 57. The inverting input terminal of the operational amplifier 55 is connected to the common connection point of the resistors 58 and 59 connected between the power supply line and the ground line. The output terminal of the operational amplifier 55 is the output point of the hold circuit 40, and the output point is connected to the control circuit 35.

Here, the control circuit 35 uses the abnormality detecting means 3
When an abnormal signal is input from 7, the switching element 3
The output of the switching signal for 1 is stopped.

Next, the operation of the above configuration will be described. As shown in FIG. 3, the circuit pattern 34 formed on the back surface of the printed circuit board 33 and the detection pattern 36 formed on the front surface thereof.
a and 36b are coupled with a predetermined capacitance,
A predetermined insulation resistance is generated between them. As a result, the voltages of the detection patterns 36a and 36b depend on the voltage level of the circuit pattern 34.

Now, when the electromagnetic cooker is powered on,
AC is rectified by the power supply circuit into DC, and the switching element 31 is turned on / off according to the switching signal from the control circuit 35, so that a high-frequency current flows through the magnetic field generation coil 29. As a result, a magnetic field is generated from the magnetic field generation coil 29 and linked to the cooking pot, so that the cooking pot generates heat and the food inside is heated.

By the way, in the induction heating state as described above, the commercial AC voltage is applied to the circuit pattern 34 on the power supply circuit side, and the circuit pattern 3 on the high frequency generating circuit side.
A high frequency voltage is applied to 4. This allows
A detection signal corresponding to the voltage applied to the circuit pattern 34 is generated in the detection patterns 36a and 36b. That is, a low frequency voltage of 50 or 60 Hz, which is the frequency of the power supply voltage, is generated from the detection pattern 36a, and the detection pattern 3
From 6b, the switching signal frequency is 20 KHz
The above high frequency voltage is generated. Therefore, the filter circuit 3
A detection signal including a high frequency component of 20 KHz or higher is generated from the input unit 38a of 8 (see FIG. 4A).

The detection signal from the input section 38a is given to the filter circuit 38. At this time, since the filter circuit 38 forms a low-pass filter, the high-frequency component of 20 KHz or higher contained in the detection signal is removed by the filter circuit 38. In the experiment by the inventor, when the heating output is set to 1200 W, the detection pattern 36a,
Although a detection signal of about 22V including a high frequency component is generated at 36b, the voltage level of the detection signal could be suppressed to about 1V by removing the high frequency component of the detection signal (FIG. 4 (b)). reference).

The detection signal from which the high frequency component has been removed as described above is amplified by the amplifier circuit 39 and then given to the hold circuit 40 (see FIG. 4C). Then, in the hold circuit 40, the voltage level of the detection signal is compared with the reference voltage, and when the voltage level of the detection signal is lower than the reference voltage, the hold circuit 40 does not output an abnormal signal, As a result, the control circuit 35 continues the switching operation.

When the ambient temperature of the electronic components mounted on the printed circuit board 33 rises excessively or the electronic components abnormally generate heat, the circuit pattern 34 and the detection patterns 36a and 36b are affected by the influence. The capacitance or insulation resistance between them changes. Then, the DC components of the detection signals from the circuit patterns 36a and 36b change according to these changes, so that the voltage level of the detection signal in the hold circuit 40 exceeds the reference voltage. As a result, the output level from the operational amplifier 55 becomes a high level and is input to its own non-inverting input terminal, so that the output level of the operational amplifier 55 is maintained at a high level, and the hold circuit 40 causes the control circuit 35 to malfunction accordingly. A signal is output (see FIG. 4 (d)). As a result,
Since the control circuit 35 stops the switching operation, the switching operation by the switching element 31 is stopped and the induction heating by the magnetic field generating coil 29 is stopped.

As described above, according to the above embodiment, the detection patterns 36a and 36b are formed on the front surface of the printed circuit board 33 corresponding to the circuit patterns 34 formed on the back surface of the printed circuit board 33. The detection patterns 36a, 3
Since the power supply is stopped when the DC voltage level of the detection signal from 6b fluctuates by a predetermined level from the DC voltage level in the normal state, it is possible to cope with abnormalities of a plurality of electronic components mounted on the printed circuit board 33. can do. Therefore, unlike the conventional example in which only the abnormality of the specific electronic component can be dealt with, it is possible to prevent the plurality of electronic components other than the specific electronic component from being burnt out.

In the above embodiment, the detection patterns 36a, 3 are associated with the power circuit side and the high frequency generation circuit side, respectively.
6b is formed and the control circuit 35 is stopped by the abnormality detection means 37 based on the detection signals from the detection patterns 36a and 36b.
The abnormality detection means may be provided corresponding to 6a and 36b, and the control circuit 35 may be stopped based on the abnormality signal from each abnormality detection means. In this case, it can be realized by outputting the logical sum of the abnormal signals from the respective abnormality detecting means to the control circuit 35 as an abnormal signal.

In the above embodiment, the printed circuit board 34 is used.
Although the double-sided wiring circuit board is targeted as the above, a multi-layered wiring circuit board may be targeted. in this case,
A detection pattern is formed on one surface of the multilayer printed circuit board.

[0030]

As is apparent from the above description, according to the abnormality detecting apparatus for electronic parts of the present invention, the detection patterns formed on the printed circuit board and facing each other with a predetermined gap along the circuit pattern are provided. A plurality of electronic components mounted on the printed circuit board are provided because the abnormality detection means for outputting an abnormality signal is provided when the DC voltage level of the detection pattern fluctuates by a predetermined level or more from the DC voltage level when the electronic component is normal. It has an excellent effect that it is possible to cope with the abnormal condition.

[Brief description of drawings]

FIG. 1 is an electric circuit diagram showing an embodiment of the present invention.

FIG. 2 is an electric circuit diagram showing an abnormality detecting means.

FIG. 3 is a vertical sectional view of a printed circuit board.

FIG. 4 is a signal waveform diagram of each signal

FIG. 5 is a view corresponding to FIG. 1 showing a conventional example.

[Explanation of symbols]

31 is a switching element (electronic component), 33 is a printed circuit board, 34 is a circuit pattern, 35 is a control circuit, 36a,
36b is a detection pattern, and 37 is an abnormality detection means.

Claims (1)

[Claims] 1. A method for detecting an abnormality in electronic components mounted on a printed circuit board and connected to each other by a circuit pattern, wherein the electronic parts are formed on the printed circuit board and face each other with a predetermined gap along the circuit pattern. An electronic component comprising a detection pattern and an abnormality detection unit that outputs an abnormality signal when the DC voltage level of the detection pattern fluctuates by a predetermined level or more from the DC voltage level of the electronic component when the electronic component is normal. Anomaly detection device.