JP2953945B2 - Electrostatic discharge 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 relatively simple device which is portable and has no restriction on the installation place, and is capable of discharging an electrostatic discharge, which is presumed to be a cause of failure of electronic equipment, from other noises. The present invention relates to an electrostatic discharge detection device that can be easily identified and detected.

[0002]

2. Description of the Related Art Electronic devices such as information processing devices and communication devices may malfunction due to electromagnetic interference (EMI) such as electrostatic discharge, opening and closing of a power supply, and radio waves for broadcasting. In some cases, serious problems such as personal injury may occur. Therefore, it is necessary for the electronic device to take sufficient measures against such EMI. However, even though EMI countermeasures are uniform, the countermeasures are not always the same depending on the cause.
In addition, since each of them requires a considerable cost, when an electronic device is affected, it is necessary to detect and analyze what the EMI source is, and take measures accordingly. Among these EMIs, there is an apparatus disclosed in Japanese Patent Laid-Open No. 04-289462 as a device for detecting and recording an EMI caused by electrostatic discharge. In this electrostatic discharge detection device, an electrostatic discharge detection unit, a control and recording unit are disclosed. Are formed separately, and are connected by an interface cable, so that the interface cable may act as an antenna and malfunction when exposed to strong radiated noise. In addition, since the above-described conventional apparatus uses a commercial power supply as a power supply, conductive noise that enters from a power supply wiring and radiation noise that enters an electrostatic discharge detection apparatus as a wiring to an external power supply becomes an antenna. ,
The electrostatic discharge detection device may not operate normally.

[0003]

DISCLOSURE OF THE INVENTION The present invention satisfies the basic condition that it can operate normally even in various strong noise environments, and its generation is irregular and has low reproducibility. The occurrence of electrostatic discharge is selectively detected from various EMI sources, and the magnitude (level) of the discharge is recorded together with the time of occurrence, so that it can be widely used for countermeasures against malfunction of electronic devices caused by electrostatic discharge. An object of the present invention is to provide an electrostatic discharge detection device having the above configuration.

[0004]

In order to solve the above-mentioned problems, according to the present invention, a small antenna in which a voltage is induced in accordance with the electric field intensity of an electromagnetic wave generated by electrostatic discharge is attached to a housing, and the induced voltage is reduced. A pulse amplifier circuit for separately amplifying the positive and negative polarities, and a comparator for comparing the output of the pulse amplifying circuit with a reference level and outputting a pulse having a predetermined width if the output exceeds the reference level. A comparison circuit, an electrostatic discharge identification circuit that outputs only an input that satisfies the condition that the next input does not occur during a period from the input of the output of the comparison circuit until a specific time elapses, as the cause of the electrostatic discharge, Electrostatic discharge whose reference level has the highest absolute value among the pulses output from the comparison circuit according to the output of the comparison circuit and the output of the electrostatic discharge identification circuit. A display circuit that displays the time at which the electrostatic discharge occurred with the time indicated by the built-in clock when the electrostatic discharge identification circuit outputs a signal indicating that the electrostatic discharge was caused by the electrostatic discharge together with the level of the electrostatic discharge. A recording circuit for sequentially recording the occurrence time and
In order to suppress the noise from the commercial power supply and the effect of the external electromagnetic field on the wiring leading to the commercial power supply, the power supply circuit using the built-in battery is all integrated as small as possible, and various external sources, including those using electrostatic discharge The above circuits are housed in a well-shielded housing so that the circuits can operate normally even when exposed to the electromagnetic waves.

[0005]

As described above, current electronic devices, especially digital devices such as computers, are susceptible to EMI. However, even if EMI electromagnetic waves are present, the electric field strength thereof is weak. Since there is no problem unless a failure occurs, a comparison circuit is also provided in the present invention to target only electromagnetic waves having an electric field strength of a certain level or more. At this time, based on experiments and research conducted by the inventor, the electric field strength of the electromagnetic wave is converted into a voltage induced at the input terminal of the antenna, and a value of 2.5 mV or more is converted to a level +1, 25 mV
Above level +2, above 250 mV level +3, 25
Level +4 for 00mV or higher, level -1 for -2.5mV or lower, level -2, -250m for -25mV or lower
V or less is level-3, -2500 mV or less is level-4
So, I decided to output the level.

[0006] Generally, electrostatic discharge is an impulse, and electromagnetic waves generated by the electrostatic discharge cover a wide band from DC to gigahertz. Therefore, if an antenna tuned to the gigahertz band is used, electromagnetic waves of electrostatic discharge can be detected, but broadcast waves from radio and television and radio waves below the megahertz band can be ignored.
In the case of electrostatic discharge, the capacitance of the discharge matrix is usually 20
It is 0 pF or less, and the next discharge does not occur for a while after one discharge occurs. On the other hand, in the electromagnetic waves generated when the power supply is opened and closed, the number of times of discharge generally occurs a plurality of times continuously. Therefore, in the present invention, the EMI electromagnetic wave caused by the electrostatic discharge is identified based on the principle that the electrostatic discharge causes a sudden change in the electric field strength and that the pulse due to the electrostatic discharge output from the comparison circuit is single-shot. As a result of experimental research, the inventor has found that in the electrostatic discharge identification circuit according to the present invention, after the first discharge has occurred, the next discharge does not occur for a while (specific time), that is, 1 ms. Only cases were identified as being due to electrostatic discharge. However, in the electrostatic discharge detection device of the present invention, since the output from the antenna is processed by several types of circuits from the antenna to the electrostatic discharge identification circuit, the above numerical values are identified by the electrostatic discharge identification circuit according to the present invention. It is merely a matter of adoption as a reference and good results in practice have been obtained, but does not claim that electrostatic discharges actually occur that way.

The electrostatic discharge includes a case where a positive pulse is induced in the antenna and a case where a negative pulse is induced in the antenna. The present invention has a pulse amplifier circuit for positive polarity and a pulse amplifier circuit for negative polarity and a comparison circuit so that all electrostatic discharges can be detected.

Further, the device of the present invention needs to operate normally even when exposed to a noise environment that may cause a failure in electronic devices, particularly computers and the like. The noise to which electronic devices, especially computers are exposed, includes conductive noise, electrostatic noise, and radiated electromagnetic noise. In the present invention, the electromagnetic wave shielding of the housing is strengthened, a built-in battery power supply is used in place of the commercial power supply, and the wiring other than the antenna for receiving the electrostatic discharge is configured not to go out of the housing. Prevents the effects of noise.

[0009]

FIG. 1 is a block diagram showing an embodiment of the present invention.
When an electromagnetic wave is generated by electrostatic discharge in the vicinity of the electrostatic discharge detection device of the present embodiment, the length of the electrostatic discharge detection unit is 25 mm
A voltage proportional to the electric field strength of the electromagnetic wave is induced in the monopole antenna. The induced voltage is separately input to a positive polarity detection circuit and a negative polarity detection circuit, passes through a pulse amplifier circuit, and outputs a pulse having a voltage proportional to the induced voltage. The pulse output from the pulse amplification circuit is amplified by the comparison circuit and is amplified at each level (level + 1: 2.5 mV, level + 2: 25 mV, level + 3: 250 mV, level +
4: 2500 mV, level-1: -2.5 mV,
Level-2: -25 mV, Level-3: -250 mV,
When level-4: -2500 mV) is reached, the level signal (8
Is output only for 1 μs. The level signal output from the comparison circuit is input to the electrostatic discharge detection unit interface, and is input as a detect signal to the electrostatic discharge identification circuit. The electrostatic discharge identification circuit is detect
It is checked whether the signal satisfies the above-described condition when the signal is caused by electrostatic discharge. If the signal is satisfied, the input signal is caused by the electrostatic discharge. Output as false. The electrostatic discharge detection unit interface transmits information indicating that the electrostatic discharge has been detected and the level of the detection to the microprocessor through the status signal based on whether the level signal and the burst signal output from the comparison circuit are true or false. Assuming that the microprocessor has detected the electrostatic discharge, the microprocessor records the level identified from the time of the real-time clock and the pattern of the status signal on the IC memory card, and displays the recorded content on the liquid crystal display. Also, since the measurement is started, the total number of occurrences of the electrostatic discharge of each level is also displayed. When the microprocessor detects the electrostatic discharge, it sounds a buzzer for a certain time to notify the detection of the electrostatic discharge. This buzzer has a changeover switch so that the buzzer sound can be turned off. After the recording is completed, a reset signal is output from the microprocessor to reset each part of the electrostatic discharge detecting device, such as a flip-flop, to prepare for the detection of the next electrostatic discharge.

A program for operating the microprocessor is stored in a read only memory of the microprocessor, and a random access memory is used as a stack and a work area of the microprocessor.

The system monitoring circuit performs runaway recovery control of the microprocessor, control for power saving, and switching control of the power supply to the real-time clock. In the microprocessor runaway recovery control, the microprocessor changes the WDT toggle signal, which is an input of a runaway monitoring timer (commonly called a watchdog timer) inside the system monitoring circuit, from high to low or low to high within 1.6 seconds. Otherwise, the microprocessor runs out of control and outputs a reset signal RES. However, when the microprocessor is in the low power consumption mode to save power, the standby signal is output from the microprocessor, and RES is not output even if the WDT toggle signal does not change.

[0012] Switching control of the power supply to the real-time clock is performed by stopping the voltage output of the real-time clock backup battery while +5 V is supplied to the real-time clock from the DC / DC converter.
When +5 V is no longer supplied from the DC / DC converter, the voltage of the real-time clock backup battery is output as the real-time clock from + Vbkup, and the real-time clock is continuously operated.

As a power source, a battery was used to prevent noise from entering from the wiring of a commercial power source. When performing repeated measurements, the battery is advantageously a secondary battery such as a nickel-cadmium battery that can be used many times by charging. However, a secondary battery is suitable for a power source of a device that can extract a relatively large amount of power (for example, several hundred mA) and can be charged for several days or constantly, but can reduce a small amount of power (several tens mA) for a long time (for more than 10 days) A) Primary batteries were employed because they are not suitable for removal. Among primary batteries, lithium batteries are superior in terms of power capacity, but alkaline dry batteries are used in consideration of the condition that they are easily available.

The DC / DC converter converts the output voltage of the dry battery to +5 V and supplies it to each circuit. Since the voltage of the dry battery (+12 V: 8 batteries) gradually decreases with the passage of time, it is necessary to stabilize the battery for use in an electronic circuit. There are a series power supply and a switching power supply as a stabilized power supply, but a series power supply always flows a constant current, so much energy is consumed as heat.
It is not suitable for stabilizing the battery voltage for a long time. On the other hand, a switching power supply temporarily stores energy in a coil, extracts the energy from the coil, and stabilizes the energy.The current flowing from the battery is only for charging the coil, and the energy consumed as heat is consumed. Therefore, a switching power supply was used for the DC / DC converter of the present invention.

The battery voltage monitor converts the output voltage of the dry cell into a voltage that can be monitored by a microprocessor, and
Output from Tlife. Microprocessor is B
The voltage of ATlife is monitored for a drop in battery voltage using an A / D converter built in the microprocessor.

In the present invention, in order to enable the battery to operate for 30 days or more, power is saved by using a low power consumption mode which is one of the functions of the microprocessor. The low power consumption mode of the microprocessor is a mode in which the power supply voltage is not supplied to the crystal oscillator which generates the operation timing of the microprocessor, while the microprocessor is in the energized state. Since the microprocessor is CMOS, it is consumed in the low power consumption mode. The only current flowing is the leakage current. The microprocessor automatically shifts to the low power consumption mode if an event such as electrostatic discharge does not occur within one minute after starting the measurement of the electrostatic discharge. The microprocessor recovers from the low power consumption mode in three ways: detection of electrostatic discharge, input from a keyboard, and real-time clock every hour. When an electrostatic discharge is detected, an ESDdetect signal is output from the interface of the electrostatic discharge detection unit, a keypress signal is output from the keyboard interface when there is an input from the keyboard, and a onehour signal is output when the real-time clock becomes every hour. Is output. These signals are input to the system monitoring circuit, which outputs a wakeup signal to the microprocessor, and the microprocessor releases the low power consumption mode.

An IC memory card was used as a recording medium for detecting electrostatic discharge. Like a floppy disk, an IC memory card is small and lightweight, is convenient to carry, and can analyze data recorded by a personal computer or the like. In addition, recording is simpler than that of a floppy disk, and since there is no rotating mechanism, power consumption during recording can be reduced, which is effective for power saving.

The keyboard is composed of six switches and is used for inputting information for controlling the microprocessor. The keyboard interface transmits the codes representing the states of the six keyboards to the microprocessor by a keycode signal.

In the present invention, the recorded data can be analyzed with a personal computer or the like, and the data can be viewed with the electrostatic discharge detection device itself.

FIG. 2 is an external view of the above embodiment. As shown in the figure, it is small with a width of 253 mm, a depth of 163 mm, and a height of 91 mm, and half of the volume of this housing is occupied by a built-in power supply battery. In order to enhance the shielding against electromagnetic waves, the housing was made of an iron plate with high magnetic permeability and nickel plating. A copper foil tape was used for the joint between the iron plate and the iron plate of the housing, and a glass mesh-attached glass was used on the surface of the liquid crystal display to enhance the shielding effect. Generally, the electrostatic discharge withstand voltage of computer equipment is based on the electrostatic discharge withstand voltage standard (IECpub.801) of the International Electrotechnical Commission.
-22 ed. 1991), it is 8 kV or more for air discharge and 3 kV or more for contact discharge. The electrostatic discharge withstand voltage of the electrostatic discharge detection device of the present invention is 1 kV for air discharge in the same test method.
5 kV or more, and 8 kV or more in contact discharge.

FIG. 3 is a circuit diagram of the electrostatic discharge identification circuit of the device of the present invention. In the figure, the input of the electrostatic discharge identification circuit is a signal PL1-N which is an output of the positive polarity detection circuit or a signal NL1-N which is an output of the negative polarity detection circuit, corresponding to the level ± 1 (± 2.5 mV), respectively. This is a pulse having a pulse width of 1 μs. The electrostatic discharge discrimination circuit detects the leading edge of the above signal (for a sudden change in electric field strength due to electrostatic discharge or the like).
Times PL1-N or NL1
It is checked whether or not 1 ms or more has passed by the leading edge of -N to meet the identification condition of electrostatic discharge. The passage of 1 ms or more is a condition that the electrostatic discharge should not occur repeatedly (one time).

The Q output of the monostable multivibrator is set to 1 by the leading edge of PL1-N or NL1-N.
True for ms. PL1-N or NL1-N becomes false 1 μs after the leading edge. In the case of electrostatic discharge, the next discharge does not occur while the Q output of the monostable multivibrator is true. Therefore, a BURST-N signal that informs the microprocessor that the induced voltage input to the antenna is not due to electrostatic discharge is a false output. The microprocessor determines that the detected discharge is due to electrostatic discharge, records and displays the electrostatic discharge level and the time at which the electrostatic discharge occurred, and outputs a reset signal DETRST-N to each circuit to prepare for the detection of the next electrostatic discharge. On the other hand, in the discharges other than the electrostatic discharge, the number of discharges is continuously a plurality of times, so that the next discharge occurs during 1 ms when the Q output of the monostable multivibrator is true, and PL1-N or NL1-N becomes true. PL1-N or NL1-N is the clock input of the JK flip-flop, the Q output of the monostable multivibrator is the J input of the JK flipflop, and the Q output of the monostable multivibrator is JK when the clock input reaches the leading edge in the true state
The logical NOT output signal of Q of the type flip-flop becomes true, and the BURST-N signal becomes true output. The microprocessor determines that the sudden change in the detected electric field strength is due to something other than electrostatic discharge, and sends a reset signal DETRST-N to each circuit.
Is output to prepare for the detection of the next electrostatic discharge. BURST
The -N signal returns to a false output when DETRST-N is output.

[0023]

As described above, according to the present invention, electromagnetic waves due to electrostatic discharge can be distinguished from electromagnetic waves due to other EMI sources at a desired place very easily without worrying about the presence or absence of a commercial power supply. It is possible to record the time of occurrence of discharge, its degree, etc., so that it was difficult to take a firm countermeasure in the past while it was suspected that it was caused by electrostatic discharge. By collating a failure that has occurred in an electronic device such as a computer with a record recorded by the apparatus of the present invention against a failure record on the electronic device side, it is useful to efficiently and effectively take measures against the failure of the electronic device.

[Brief description of the drawings]

FIG. 1 is a block diagram of one embodiment of the present invention.

FIG. 2 is an external view of an embodiment of the present invention.

FIG. 3 (a) is a circuit diagram of an electrostatic discharge identification circuit according to the present invention, and FIG. 3 (b) is a signal PL1-N or NL1-N.
The figure which shows the state of each signal when it does not reach the leading edge again for 1 ms from the leading edge of FIG.
FIG. 3 (c) is a diagram showing the state of each signal when the leading edge of the signal PL1-N or NL1-N reaches the leading edge again within 1 ms from the leading edge.

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-4-289462 (JP, A) JP-A-58-42977 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) G01R 29/08 G01R 29/24 G01R 31/00

Claims (1)

(57) [Claims] 1. An electrostatic discharge for detecting an electrostatic discharge.
In the detection device, an antenna in which a voltage corresponding to the electric field intensity of the electromagnetic wave generated by the electrostatic discharge is tuned in the gigahertz band, and a positive polarity that amplifies the positive voltage induced by the antenna
Pulse amplifier circuit and negative polarity induced by the antenna
And the negative pulse amplifier circuit for amplifying the voltage, the positive polarity
If the output of the use pulse amplification circuit is compared with a reference level has exceeded the reference level and outputs a pulse of a predetermined width
Compare the output of the comparator circuit for positive polarity and the output of the pulse amplifier circuit for negative polarity with the reference level
If it exceeds the reference level, a pulse with a predetermined width
A comparison circuit for negative polarity, an output of the comparison circuit for positive electrode, and a comparison for negative polarity.
For each output of the circuit, the output pulse is
The next output pulse before the specified time elapses after the input
Induced power in the case of vinegar input is consistent with the condition that does not occur
And electrostatic discharge identifying circuit for outputting a signal pressure as due to electrostatic discharge, a clock for outputting information indicating the time, the detection result display for displaying positive and negative sensed at the comparator circuit
Level of electrostatic discharge for each, and the when the electrostatic discharge detection circuit has output a signal as being caused by electrostatic discharge, the ESD generation time in which the time when the clock indicates the time of occurrence of that discharge the Display
Electrostatic discharge detection apparatus characterized by comprising: a display circuit for displaying in Lee, and a recording circuit for successively recording the level and the electrostatic discharge occurrence time of the electrostatic discharge.