JP3450048B2 - Static eliminator balance adjustment circuit - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a balance adjusting circuit for adjusting the amount of ions generated by a static eliminator for eliminating static electricity from an object. 2. Description of the Related Art Since semiconductor devices are easily damaged by static electricity, it is necessary to remove the static electricity during storage and manufacturing processes. For this reason, conventionally, a static eliminator based on the principle as shown in FIG. 4 has been used in the semiconductor device manufacturing process and the like. In FIG. 4, reference numeral 1 denotes a commercial AC power supply (100
V), 2 is a power switch, 3 is a step-up transformer, and 4 is a high-voltage cable. Reference numeral 5 denotes a neutralizing electrode composed of a ground electrode 6 and a discharge electrode 7. The discharge electrode 7 is connected to one end of the step-up transformer 3 via a conductor of the high-voltage cable 4. The ground electrode 6 is connected to the other end of the step-up transformer 3 via the ground wire of the high-voltage cable 4 and is grounded.
Reference numeral 8 denotes a charged object such as a semiconductor device which is opposed to the charge removing electrode 5 in a non-contact state. In the above configuration, when the power switch 2 is turned on, the output voltage from the power source 1 (AC 1
00V) is boosted through the boosting transformer 3, and a positive or negative high voltage (for example, 7 kV) is alternately applied to the discharge electrode 7. Then, a corona discharge is generated between the discharge electrode 7 and the ground electrode 6, and the air around the charge removing electrode 5 is alternately ionized into positive and negative ions. And the charged object 8
Depending on the polarity of the charged charge, ions of any polarity are attracted to the charged object 8 and recombine with the charged charge of the charged object 8 to neutralize the charged charge. Since the polarity of the output voltage of the power supply 1 changes alternately in a sinusoidal manner, the discharge electrode 7 should generate ions of the same amount in principle in positive and negative directions. However, it is known that negative ions are actually generated slightly more. Such an imbalance of positive and negative ions may cause a new charge on the charged object 8,
Adjustments are required. FIG. 5 is a diagram illustrating a configuration of a static eliminator in which an ion balance adjustment unit 30 that performs the adjustment is added to the configuration of FIG. In the configuration shown in FIG. 5, when the current of the power supply 1 is positive, the current passes through the diode 31 and the high voltage boosted through the boosting transformer 3 is applied to the discharge electrode 7. On the other hand, if the current of the power supply 1 is negative,
Is supplied to the primary side coil of the step-up transformer 3 via the
Therefore, by adjusting the resistance value of the variable resistor 32, only the voltage value of the negative component applied to the primary coil of the step-up transformer can be reduced to a desired level, and the negative voltage generated from the discharge electrode 7 can be reduced. The amount of ions can be reduced, and the balance between positive and negative ions can be equalized. FIG. 6 is a diagram showing an AC voltage waveform in the static eliminator, and the shaded portion indicates a reduced negative voltage amount. [0007] By the way, a coaxial cable may be used as the high-voltage cable 4 in order to avoid the risk of electric shock to the human body. In such a case, the load on the secondary side of the step-up transformer 3 becomes capacitive, and the phase of the current on the secondary side is advanced from the phase of the voltage. In this case, even if the resistance value of the variable resistor 32 is changed, the level of the secondary voltage does not change much. As a safety measure for preventing an overcurrent from flowing to the secondary side, a leakage transformer may be used as the boosting transformer 3 in some cases. Since this leakage transformer has a large leakage reactance, the leakage side has a large load.
When the current flowing to the secondary side increases, the voltage on the secondary side decreases. When this leakage transformer is used in addition to the use of the coaxial cable, the above-mentioned tendency that the level of the secondary voltage is hard to change even when the resistance value of the variable resistor 32 is changed is further strengthened. The present invention has been made in view of the above circumstances, and has as its object to provide a balance adjustment circuit for a static eliminator that can adjust the amount of positive and negative ions generated to an optimal state. [0008] In order to solve the above-mentioned problems, the present invention relates to a step-up transformer having a primary side connected to an AC power supply, and a secondary side end of the step-up transformer coupled to the step-up transformer. In a static eliminator comprising: a discharge electrode; and a ground electrode disposed so as to face the discharge electrode and connected to the other end on the secondary side of the step-up transformer. A first diode inserted between the power supply and a power supply, a second diode connected in parallel with the first diode so that the polarity is reversed, and a diode connected to at least one of the diodes. the voltage level adjusting resistor connected in series, the booster Trang
And a phase adjusting coil for adjusting the phase of the primary current of the source. According to the above arrangement, the resistance value of the voltage level adjusting resistor is adjusted so that either the positive or negative primary voltage applied to the step-up transformer or both primary voltages are applied. Since each voltage can be reduced to a desired level, it is possible to adjust the amount of positive or negative ions generated from the discharge electrode so as to be an appropriate amount. Also, since the phase of the primary side current of the step-up transformer can be adjusted by the phase adjusting coil, for example, the secondary side of the step-up transformer and the discharge electrode and the ground electrode are connected by a coaxial cable to reduce the capacitance reactance. Even when this occurs, the inductive reactance of the phase adjusting coil can be adjusted to match the phases of the current and the voltage on the secondary side. Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing a configuration of a static eliminator according to one embodiment of the present invention. The same reference numerals are given to the same parts as those in FIG. 4 and the description thereof will be omitted. In FIG. 1, reference numeral 10 denotes a power supply device, 12 denotes a neutralizing electrode, and both are connected by a coaxial cable 11. As the step-up transformer 3, a leakage transformer is used. Next, the configuration of the charge removing electrode 12 will be described with reference to FIG. 2 showing a specific structure thereof. 2, (A) is a front view, and (B) is a cross-sectional view in the XX ′ direction of the front view (A). As shown in FIGS. 1 and 2, a predetermined length at the end of the central conductor of the coaxial cable 11 is used as the high-voltage electrode 13. Next, a reference numeral 17 in FIG. 2 denotes a coupling ring formed of an insulating material into a hollow cylindrical shape, the surface of which is covered with a conductor such as brass. A needle-like discharge electrode 14 protrudes from the conductor. A plurality of the coupling rings 17 are provided at predetermined intervals, and a high-voltage electrode 13 whose hollow portion is covered with an insulating coating 16 penetrates. That is, the high-voltage electrode 13 and each discharge electrode 14 are capacitively coupled via the above-described insulating portion. Reference numeral 18 denotes a mold portion that covers each coupling ring 17 from which the high-voltage electrode 13 and the discharge electrode 14 protrude. Reference numeral 19 denotes another mold portion provided so as to cover the mold portion 18, and the ground electrode 15 is fixed in the form shown in FIG.
It plays the role of integrating and protecting the two. Next, in the power supply device 10 shown in FIG.
Reference numeral 20 denotes an ion balance adjustment unit. In the adjustment unit 20, the same type of diodes 21 and 22 are connected in parallel so as to have opposite polarities, and a variable resistor 23 is connected in series with the diode 22. 24 is a variable reactance coil. Next, the operation of this embodiment will be described with reference to FIG. FIG. 3 is an equivalent circuit of FIG. 1, and it is assumed that the high-voltage power supply V is directly supplied without including the booster transformer 3 for convenience. In FIG. 3, the impedance Z of the circuit is shown.
Is XL for the inductive reactance of the variable reactance coil 24, XC for the capacitive reactance of the capacitor C (capacitive part of the secondary side circuit by the coaxial cable 11 etc.), and R
Assuming that the resistance value of (the load connected to the secondary side) is r, Z ≒ (r ² + (XL−XC) ² ) (1) Here, if the inductive reactance XL of the variable reactance coil 24 is adjusted so that XL ≒ XC (2), Z ≒ r (3), and the effect on the circuit of the capacitive reactance XC, that is, The phase lead of the current with respect to the voltage due to the use of the coaxial cable 11 is compensated. Further, by changing the resistance value of the variable resistor 23, only the negative voltage of the high voltage power supply V can be reduced to an appropriate level. Now, the variable reactance coil 24 and the variable resistor 23 are adjusted so as to satisfy the above conditions, and a charged object is placed below the neutralization electrode 12 shown in FIG. It is assumed that the switch 2 is turned on. As a result, the output voltage of the power supply 1 is boosted to, for example, 7 kV via the boost transformer 3, and a low-frequency high voltage is applied to the high-voltage electrode 13 via the coaxial cable 11. Here, in the primary circuit of the step-up transformer 3, the phase of the current lags behind the phase of the voltage due to the above adjustment. As a result, the phases of the current and the voltage substantially match. Also, one of the step-up transformers 3
The negative voltage applied to the high voltage electrode 13 decreases as the negative voltage applied to the secondary coil decreases. Therefore, by adjusting the variable resistor 23, the amounts of positive ions and negative ions generated by the corona discharge generated between the discharge electrode 14 and the ground electrode 15 that are capacitively coupled to the high-voltage electrode 13 can be substantially equalized. Thus, the charged charges of the opposed charged objects are reliably neutralized. If the balance between the positive and negative ions is lost due to a change in the state of the surrounding atmosphere or the like during use of the static eliminator, the variable resistor 23 may be adjusted again to equalize the amount of positive and negative ions generated. . The reason why the diode 22 is provided in the configuration shown in FIG. 1 is as follows. In FIG. 1, the forward voltage drop of the diodes 21 and 22 is represented by V
d, the resistance value of the variable resistor 23 is vr, and when the current of the power supply 1 is positive, the current flowing from the terminal ta to the terminal tb is i1
On the other hand, if the current flowing from the terminal tb to the terminal ta is i2 when the current of the power supply 1 is negative, the voltage drop V1_ab between the terminals ta and tb with respect to the current i1 is as follows: V1_ab = Vd (4) , The voltage drop V2_ba between the terminals tb and ta with respect to the current i2 is as follows: V2_ba = Vd + vr · i2 (5) Next, assuming that the diode 22 is not provided in the circuit, the terminal tb-t with respect to the current i2 is
The voltage drop amount V2_ba 'between “a” is as follows: V2_ba ′ = vr · i2 (6) Here, as described above, in order to reduce the negative side of the primary side voltage of the step-up transformer, the voltage drop amount V2_ba
Alternatively, it is necessary to make V2_ba 'larger than the voltage drop V1_ab. That is, the difference Δ in the following equations (7) and (8)
V1 and ΔV2 must both be positive. ΔV1 = V2_ba−V1_ab = vr · i2 (7) ΔV2 = V2_ba′−V1_ab = vr · i2−Vd (8) The above equation (8), that is, the difference ΔV2 when the diode 22 is not provided. To the same level as the equation (7), that is, the difference ΔV1 when the diode 22 is provided, it is necessary to increase the resistance value vr of the variable resistor 23. Here, since the difference ΔV1 required for the balance adjustment is only a few volts, the voltage drop amount Vd of the diode cannot be ignored in the equation (8). Actually, in both cases, the resistance value vr required to balance the positive and negative ions was measured. When the resistance value vr was less than 5 ohms when the diode 22 was provided,
Was 15 ohms. Thus, by providing the diodes 21 and 22 together, the resistance value vr of the variable resistor 23 necessary for balance adjustment can be reduced. Although the variable resistor 23 is connected in series only to the diode 22 in the above-described embodiment, a variable resistor is also connected in series to the other diode 21 so that a positive voltage and a negative voltage are connected. Both voltages may be adjustable, and the level of the voltage on the side that is easier to adjust may be adjusted as the case may be. When it is not necessary to adjust the phase, for example, when a coaxial cable is not used as the high-voltage cable, or when a leakage transformer is not used as the step-up transformer, the variable reactance coil 24 need not be provided. As described above, according to the present invention, the balance between the phase of the primary current of the step-up transformer and the level of the positive / negative voltage can be adjusted. Can be adjusted to an optimal state.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing a configuration of a static eliminator having a balance adjusting circuit according to an embodiment of the present invention. FIG. 2 is a diagram showing a specific structure of a charge removing electrode 12 in FIG. FIG. 3 is a diagram showing an equivalent circuit of the configuration of FIG. 1; FIG. 4 is a block diagram showing a configuration of a conventional static eliminator. FIG. 5 is a block diagram showing a configuration of a static eliminator having an ion balance adjusting unit of a conventional example. FIG. 6 is a diagram showing an AC waveform of the static eliminator of FIG. 5; [Description of Signs] 1 AC power supply 3 Step-up transformer 14 Discharge electrode 15 Ground electrode 21, 22 Diode 23 Variable resistor (voltage level adjusting resistor) 24 Variable reactance coil (phase adjusting coil)

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-59-33800 (JP, A) JP-A-52-30440 (JP, A) JP-A 2-64199 (JP, U) JP-A 7-33 27097 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) H05F 3/04 H01T 19/04 H01T 23/00

Claims (1)

(57) Claims 1. A step-up transformer having a primary side connected to an AC power supply, a discharge electrode coupled to one end of a secondary side of the step-up transformer, and facing the discharge electrode. And a ground electrode connected to the other end on the secondary side of the step-up transformer and a grounding electrode connected to the AC power supply. A first diode inserted, a second diode connected in parallel with the first diode so that the polarity is reversed, and a voltage connected in series to at least one of the diodes. phase adjustment to adjust the level adjusting resistor, the phase of the primary current of the step-up transformer
A balance adjusting circuit for a static eliminator, comprising: a regulating coil .