JPH0425664Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a pseudo static electricity generator used for quantitatively measuring malfunctions of electronic equipment, particularly digital equipment, caused by electrostatic discharge.

At present, this type of pseudo-static electricity generator is
Depending on the method used to obtain a capacitance equivalent to the capacitance assumed to be possessed by the human body, there are two main types: capacitive type and vane type. They are used differently depending on the difference in test voltage, etc.

Generally, the discharge voltage of the vane type is limited to several kV due to performance constraints of the parts used, whereas the capacitive type can generate a discharge voltage of up to several tens of kV.

The present invention relates to the above-mentioned capacitive pseudo-static electricity generator, and FIG. 1 shows a wiring diagram of the main parts of the system. In the figure, DCV is a DC high-voltage variable power supply whose negative pole is grounded and whose positive pole is connected to one end of the on-off switch _SW1 .
The other end of the open/close switch _SW1 is connected to one end of a charging resistor _R1 , and the other end of the charging resistor _R1 is connected to one end of a capacitance C for storing charge and one end of a discharging resistor _R2 . ing. The other end of the capacitor C is grounded, and the equipment under test EUT is provided at the other end (tip) side of the discharge resistor _R2 . Next, with reference to FIG. 1, the operating principle of the capacitive pseudo-static electricity generator,
I will explain how to use it.

First, the DC high voltage variable power supply DCV is set to an arbitrary value (E
When the switch _SW1 is closed, the capacitance C is charged with a time constant τ= _CR1 determined by the charging resistor _R1 and the capacitance C.

After fully charging, open the on/off switch SW ₁ and gradually bring the tip of the discharge resistor R ₂ closer to the equipment under test EUT, so that the charge Q = CE stored in the capacitance C is A discharge path is formed in the gap between the tip of the discharge resistor R ₂ and the equipment under test EUT, causing a spark phenomenon and electrostatic discharge.

In general, testing machines using this method are characterized by the ability to select the discharge location arbitrarily, so the other components except the DC high voltage variable power supply DCV built into the housing are the discharge probe with built-in discharge needles, etc. It is designed to have a separate structure from the casing (the casing and the discharge probe are connected and detached by a connector using a high-voltage insulated cable).

For this reason, the discharge probe must be operated by hand, and it is necessary to give sufficient consideration to the safety aspect of use, especially the capacitance C.
It is required to be able to accurately judge whether or not electric charge is stored in the battery. Also, the discharge voltage is several kV
If the value is relatively low, the discharge phenomenon will not be accompanied by a spark phenomenon, making it even more difficult to confirm the presence or absence of discharge, which may lead to unexpected problems.

The present invention has been devised in view of the above points, and its purpose is to provide a pseudo-static electricity generator that can confirm the presence or absence of a discharge phenomenon.

According to the present invention, a current transformer for detecting a generated pulse signal in a pseudo static electricity generator used for electrostatic resistance testing of electronic equipment;
A pseudo-static electricity generator is obtained, which is characterized in that it is equipped with a means for determining whether charging or discharging is occurring using this detection pulse.

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 2 is a main part wiring diagram showing the configuration of an embodiment of the pseudo-static electricity generator according to the present invention.

In the figure, CT is a current transformer, and the primary side passes through the center of the transformer to detect the discharge current.
1T coil, secondary side consists of appropriately wound toroidal magnetic core. On the secondary side of the current transformer CT, there are resistors R ₁₀ to R ₁₃ , a Zener diode ZD ₂ ,
A waveform shaping circuit 10 consisting of a diode D ₃ and inverters IC ₂ and IC ₂ is connected.

Monostable multivibrator IC ₁ connected to the output of waveform shaping circuit 10, resistor R ₇ , and capacitor
The circuit 20 consisting of C ₁ is a circuit that generates a constant pulse width determined by the resistor R ₇ and the capacitor C ₁ every time a pulse is input, regardless of the pulse width input to the monostable multivibrator IC ₁ . ,
This output pulse is amplified by an amplification circuit 30 constituted by resistors R ₈ and ₉ and a transistor Tr, and cuts off and on the excitation coil of a relay RL connected to the collector of the transistor Tr.

SW ₂ is the normally closed contact of relay RL, LED is a light emitting diode to check charging and discharging, and Th is a thyristor.

A circuit 40 consisting of a resistor R ₃ and a Zener diode ZD ₁ is a circuit for detecting a signal during charging.
It is connected to the gate of thyristor Th along with resistors R ₄ and R ₅ .

In addition, diode _D1 was inserted to prevent reverse discharge from capacitance C and ensure normal operation.
Diode _D2 is inserted to protect transistor Tr from reverse voltage induced in the excitation coil of relay RL.

The pseudo-static electricity generator configured as described above can clearly know whether it is charging or discharging through the following operations.

Now, assuming that the capacitance C has no charge at all, if the on-off switch _SW1 is closed in this state, the capacitance C will be charged through the charging path of the diode _D1 and the resistor _R1 . At this time, a divided voltage is also applied to the Zener diode ZD ₁ , a signal is sent to the gate of the thyristor Th via the resistor R ₅ , and the thyristor Th becomes conductive. As a result, the resistance R ₆ from the external power supply +V
Current flows through the normally closed contact SW ₂ of the relay RL to the light emitting diode LED, which lights up to indicate that the capacitance C is charged.

Here, since the thyristor Th has a self-holding function, the light emitting diode LED continues to light up even if the on/off switch SW ₁ is in the open state, indicating that charge is stored in the capacitance C. .

On the other hand, during discharge, the charge Q stored in the capacitance C
= CE starts discharging in the discharge path consisting of the discharge resistor R ₂ , the air gap, and the equipment under test EUT as described above, and a pulse voltage determined by the discharge current is generated in the secondary winding of the current transformer CT. This pulse voltage is waveform-shaped by resistors _R10 to _R13 , inverters _IC2 , _IC2 , Zener diode _ZD2 , and diode _D3 , and is input to monostable multivibrator _IC1 .

Monostable multivibrator IC ₁ resistor R ₇ and capacitor regardless of the pulse width of the input pulse
It has the function of generating a pulse waveform with a constant pulse width determined by C ₁ every time an input is received, but since this output pulse cannot directly activate the excitation coil of relay RL, the resistor R ₈ , _R9 and a transistor Tr.

As a result, the normally closed contact SW ₂ of the relay RL becomes open, the light emitting diode LED goes out, the thyristor Th becomes non-conductive, and the light emitting diode
You can tell when a discharge has occurred using the LED,
The presence or absence of charge stored in the capacitance C can be sensed.

As described above, according to the present invention, by adding an electronic circuit consisting of a current transformer CT for detecting discharge current and some electronic components to the basic circuit shown in FIG. It becomes possible to indirectly know the presence or absence of charge stored in the .
Moreover, the presence or absence of a discharge phenomenon can be easily confirmed even during a test at a relatively low voltage, making it possible to provide the intended pseudo-static electricity generator. Also, for practical application,
It goes without saying that the safety in use is doubled by attaching the light emitting diode LED to a position where it can be easily checked on the discharge probe.

[Brief explanation of drawings]

FIG. 1 is a wiring diagram of essential parts forming the basis of a capacitive pseudo-electrostatic generator, and FIG. 2 is a wiring diagram of essential parts showing an embodiment of the present invention. DCV: DC high voltage variable power supply, SW ₁ : Open/close switch, R ₁ : Charging resistor, C: Capacitance equivalent to human body equivalent capacity, R ₂ : Discharging resistor, EUT
...Equipment under test, CT...Current transformer,
ZD ₁ , ZD ₂ ... Constant voltage diode, D ₁ - D ₃ ... Diode, R ₃ - _{R 13} ... Resistor, Th ... Thyristor, LED ... Light emitting diode, IC ₁ ... Monostable multivibrator, IC ₂ ...Inverter, Tr...
Transistor, RL...Relay, SW ₂ ...Relay
RL contact, C ₁ ...Capacitor, +V...External power supply.

Claims (1)

[Scope of utility model registration request] A pseudo-static electricity generator used for electrostatic resistance testing of electronic equipment includes a high-voltage power supply that generates a high voltage for charging, a capacitor for charging and discharging, and a high-voltage generator to which a high voltage is applied from the high-voltage power supply to the capacitor. A charging time detection means for detecting a signal during charging of the capacitor, an indicator for displaying the presence or absence of electric charge stored in the capacitor, and a charging time of the capacitor being detected by the charging time detection means. a current transformer for detecting a pulse signal generated when the capacitor is discharged; and a means for turning off the indicator using the detection pulse. A pseudo-static electricity generator characterized by: