JPH0746036Y2 - Electronic circuit protection element - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a protective element for an electronic circuit, which is inserted into a power supply line of various electronic devices to remove noise voltage and surge voltage superimposed on the power supply voltage. .

[Prior Art] Today, various electronic devices have been highly functionalized by incorporating a microcomputer or the like, and have come to be used with high precision for various purposes.

However, in order to properly operate this electronic device, it is necessary to ensure that the built-in microcomputer does not malfunction, and noise voltage and surge voltage included in the power supply voltage have become a problem in recent years, and various noise Filters and surge absorbers are used.

As shown in FIG. 5A, this noise filter is a filter 50 in which a coil and a capacitor are combined so that a coil is normally inserted in the power supply line and a capacitor is inserted between the lines.
The high frequency noise is short-circuited by the inductance of the coil and the capacitance of the capacitor so that the high frequency noise is not input to the electronic device 45.

As the surge absorber, a varistor which is generally a non-linear resistance element, an arrester using a discharge gap, or a composite element of these elements is used, and the absorber is combined so as to insert the element between the lines as shown in FIG. 5B. By setting 55, when the line voltage or the ground voltage exceeds a predetermined value, that is, noise or surge is superimposed on the proper power supply voltage, and the power supply voltage including the peak value of the high voltage is applied to the electronic device. In this case, the peak value of the power supply voltage input to the electronic device 45 is limited by short-circuiting the high voltage component (for example, JP-A-62-287584).

Noise Filter Assignments devised to be Solved] It is possible to set up high-frequency of a few tens MH _Z relatively easily so as to cut also in the power supply line, inserting the coil to the electronic device in series Since the structure is adopted, the characteristics of the coil must be set in accordance with the current capacity of the electronic device, etc., and standardization and mass production have been difficult.

Further, a surge absorber using a varistor or an arrester prevents a high voltage from being input to an electronic device, and has the advantage that it is sufficient to limit only the voltage regardless of the current consumption of the electronic device. In response to a surge having a steep rise characteristic, however, a voltage higher than expected may be applied to an electronic device through a high voltage exceeding the limit voltage due to a delay in response time, and this delay in response time is a problem especially in arresters. Has become. In addition, even in a varistor with a relatively high response speed, there is a case in which the breakdown does not occur at the specified breakdown voltage and the breakdown occurs at a voltage higher than the specified voltage. Assuming that the voltage was superimposed on the voltage, as shown in Fig. 6, when a test was performed with a voltage of 500 V and an impulse with a width of 1 μs,
Although it is set to give a 200V peak value for 100V, it sometimes causes an overshoot of 400V or more at the start and causes a yield of 300V.

By the way, in recent years, high-speed processing has progressed in microcomputers incorporated in electronic devices, so that even higher speed responsiveness and appropriate voltage limitation are required when removing noise and surges contained in power supply voltage. Came.

[Means for Solving the Problem] The present invention inserts a transient avalanche diode having a predetermined breakdown voltage and a capacitor having a predetermined capacitance in parallel between power supply lines, and
A transient avalanche diode and a capacitor are inserted in parallel between the forward and backward paths of the power supply line and the ground.

Further, the three avalanche diodes and the capacitors provided between the wires and the ground are integrated by a molding resin, and the terminals or lead wires are led out to form an integrated structure element.

[Operation] According to the present invention, the line voltage and the ground voltage are set to a certain value or less by the transient avalanche diode, and the harmonics generated at the time of voltage cut can be eliminated and the rising and falling can be moderated by the capacitor.

In addition, the element integrally molded with the molding resin is extremely easy to handle.

[Embodiment] In the embodiment of the present invention, as shown in FIG. 1, a first avalanche diode 22 for transient and a predetermined diode 22 are provided between two terminals of a first terminal 12 and a second terminal 14 connected to a power supply line. A first capacitor 32 having a capacitance of is provided in parallel, and a transient second avalanche diode 24 and a third avalanche diode 26 are inserted in series between the first terminal 12 and the second terminal 14, and Second condenser 34
And a third capacitor 36 are inserted in series between the first terminal 12 and the second terminal 14 to form a second avalanche diode.
Second connection point between 24 and third avalanche diode 26 and second
The connection point between the capacitor 34 and the third capacitor 36 is both connected to the third terminal 16 for grounding, and all of these avalanche diodes and capacitors are sealed with a molding resin to form the integrated circuit protection element 10 for electronic circuits. It is a thing.

This electronic circuit protection device 10 is set for AC 100V, and the first avalanche diode 22 to the third avalanche diode 26 consider the fluctuation of the peak voltage of 141V ± 10% as shown in FIG. A silicon avalanche diode for transient having a bidirectional characteristic in which the breakdown voltage V _B is 220 V and the DC rated voltage V _S is 175 V is used. The first avalanche diode 22 removes the line noise voltage in the normal mode, and the second avalanche diode 24 and the third avalanche diode 26 remove the ground noise voltage in the common mode. A silicon avalanche diode is used to protect the electronic device 45 from a high voltage superimposed on the power supply voltage due to discharge, induced lightning, power line surge, and the like.

Further, the first capacitor 32 is 0.1 μF for normal mode noise countermeasures, and the second capacitor 34 and the third capacitor 36 are 2200PF for common mode noise countermeasures.
I used the one.

The first capacitor 32 to the third capacitor 36 cancel the harmonics when the surge voltage is cut by the avalanche diode and prevent a sharp change. This is because, for example, the electronic circuit protection element 10 is inserted into the power line of the electronic device 45 so that the first terminal 12 and the second terminal 14 are connected to the power source 40 as shown in FIG. As the surge, when an impulse having a voltage value of 2000 V is applied with a time width of 1 μsec as shown in FIG. 4A, the surge applied to the electronic device 45 is removed without inserting the first capacitor 32. As shown in FIG. 4B, the voltage can be cut at about 260 V, but ultra-high frequency vibration occurs after the voltage rises and after the voltage rises.

In this way, the avalanche diode operates without a time delay like an arrester, but vibration is generated to forcibly make a sharp change.Therefore, by inserting capacitors in parallel and absorbing super high frequency, In the present embodiment, as shown in FIG. 4C, it was possible to obtain a waveform having a gentle rise and fall and having a peak value of about 250 V and a small vibration component.

As described above, the protection device 10 according to the present embodiment limits the peak value of the voltage input to the electronic device 45 by the first avalanche diode 22 without a time delay with respect to the normal mode surge voltage, Since the second avalanche diode 24 and the third avalanche diode 26 limit the peak value of the voltage input to the electronic device 45 without having a time delay with respect to the surge voltage of the common mode, it is incorporated in the electronic device 45. It is possible to reliably prevent the microcomputer or the like that is present from being destroyed, eliminate the risk of causing malfunction, and eliminate the abrupt change with respect to the normal mode surge by the first capacitor 32.
In addition, since the second capacitor 34 and the third capacitor 36 eliminate a sharp change with respect to the surge of the common mode, the elements of the microcomputer incorporated in the electronic device 45 perform the edge trigger operation and the level trigger operation. In this case, malfunction can be prevented.

Further, in this embodiment, since the current load is dispersed by inserting the capacitor in parallel with the avalanche diode, the life of the protection element 10 for the electronic circuit is extended, and the severe condition such as the noise margin test is maintained for a long time. Even if it is done, it can be sufficiently adapted.

When used in an electronic device 45 that uses an AC 200V power source, the first avalanche diode 22, the second avalanche diode 24, and the third avalanche diode 26 have a breakdown voltage V _B of 400V and a DC rated voltage V _S of 324V. By using the bidirectional type, the peak value of power supply voltage is about 280V ± 10
When the surge voltage is supplied to the power supply voltage by allowing the fluctuation of about%, the power supply voltage is prevented from being input to the electronic device 45 by a value equal to or higher than a predetermined voltage. The surge can be removed.

Further, the electronic circuit protection element 10 should be molded so that lead wires can be drawn out from the respective terminals of the first terminal 12 to the third terminal 16 so that it can be easily connected to the power supply line or the like. You can also

[Effects of the Invention] Since the electronic circuit protection device according to the present invention uses the transient avalanche diode and the capacitor,
The avalanche diode enables the surge voltage to function without a time delay, the power supply voltage can be reliably regulated to the specified voltage or lower, and the capacitor can prevent sharp voltage fluctuations. It is a protective element for an electronic circuit, which can prevent malfunction of the electronic device.

Furthermore, by incorporating it into an electronic device such as an electronic device for 100V or an electronic device for 200V by forming an element having an integral structure with a molding resin, and connecting a terminal or a lead wire of the protective element to a power line of the electronic device, the device Can easily and surely protect the electronic circuit from noise and surge,
It is a protective element for electronic circuits that can be mass-produced because it can be easily incorporated into various electronic devices.

[Brief description of drawings]

FIG. 1 is a diagram showing a circuit configuration example of a protection device according to the present invention, FIG. 2 is a graph showing characteristics of a transient avalanche diode used in the present invention, and FIG. 3 is a graph showing a protection device according to the present invention. FIG. 4 is a diagram showing a state of use, FIG. 4 is a diagram showing a surge waveform, FIG. 5 is a diagram showing a conventional protective element, and FIG. 6 is a diagram showing a conventional surge waveform. 10 …… Protective element, 12,14,16 …… Terminal, 22,24,26 …… Avalanche diode, 32,34,36 …… Capacitor, 40 ……
Power supply, 45 ... Electronic device, 50 ... Noise filter, 55 ...
… Surge absorber.

Claims (2)

[Scope of utility model registration request] 1. A capacitor having one capacitor inserted between power supply lines and having both ends connected to each power supply line and one transient avalanche diode in parallel, and having the same capacitance between the power supply lines. Two capacitors in series and two transient avalanche diodes having the same voltage drop are also connected in series between the power supply lines, and the middle point of the two capacitors and the two capacitors in series A protection element for electronic circuits, characterized in that the midpoint of the transient avalanche diode is connected to the ground terminal. 2. A capacitor and a transient avalanche diode are connected in parallel between two terminals,
Further, two capacitors are connected in series between the terminals, and two transient avalanche diodes are also connected in series between the terminals. The midpoint of the two capacitors in series and the two avalanches in series A protection element for an electronic circuit, characterized in that a middle point of a diode is connected to a third terminal and all avalanche diodes and capacitors are encapsulated in a molding resin to be integrated.