JPS642553Y2 - - Google Patents

Description

[Detailed description of the invention] [Field of industrial application] The present invention consists of a high voltage generator that outputs a DC high voltage using a multi-stage booster circuit, a high voltage electrode charged by the high voltage generator, and a high voltage electrode that is charged by the high voltage generator. The present invention relates to a high voltage generator that includes at least a high voltage line between a generator and a high voltage electrode, and a switch consisting of a plurality of switch elements connected in series between low voltage terminals.

[Conventional technology]

FIG. 1 shows, for example, an electrostatic coating device as a conventional high voltage generator. In the figure, 1 is an AC power source such as a high frequency inverter, 2 is a step-up transformer, and 3 is a DC high voltage generating circuit, for example, a Kotscroft-Walton circuit. 4 is the negative output terminal of the circuit, 5 is a current limiting resistor, 6 is a discharge diode, 7 is a high voltage electrode shown as a painting gun, 8 is a grounded object to be painted, and 9 is a current detection circuit. , 10 is a spark discharge occurrence prediction circuit that predicts the occurrence of spark discharge based on the state of change of the detected current detection signal, 11 is a pulse generation circuit that generates a pulse when receiving an output signal from the circuit, and 12 is a A pulse transformer 13 includes thyristors S ₁ to _{S 5} which are switch elements connected in series, and the thyristor S ₁
Distributed capacitance CS ₁ ~ CS 5 between ~S ₅ and ground Capacitor C ₁ to correct imbalance in voltage sharing of thyristors _{S 1} ~ _{S 5} and prevent malfunction of thyristors S ₁ ~ _{S 5}
~ _C5 and resistors _R1 ~ _R5 .

In the electrostatic coating device with such a configuration, under normal operating conditions, a negative number +KV is applied to output terminal 4.
DC high voltages of around -100KV have appeared,
The load current is determined by the current detection circuit 9, grounding, the object to be painted 8,
It flows to the output terminal 4 via the high voltage electrode 7 and the current limiting resistor 5.

If the object to be coated 8 abnormally approaches the high voltage electrode 7 in such a state, the state of the current flowing through the current detection circuit 9 changes. The spark discharge occurrence prediction circuit 10 outputs a spark discharge occurrence prediction signal when it is determined that the change state of the current detection signal from the current detection circuit 9 is a precursor phenomenon of spark discharge occurrence. Based on this signal, the pulse generator 11 generates a pulse signal, which is transmitted to the thyristor S ₁ via the pulse transformer 12.
~ Turn on S ₅ at the same time. Accordingly, a discharge current flows from the ground to the ground via the switch 13, the discharge diode 6, the high voltage electrode 7, and the object to be painted 8, and the output terminal 4 is brought to a high potential in a short period of several tens of microseconds to 100 microseconds. to a lower potential. Therefore, the occurrence of spark discharge can be almost certainly prevented.

[The problem that the idea aims to solve]

However, in this circuit, unless capacitors C ₁ to _{C 5} have a considerably large capacitance,
There was a drawback that the distributed capacitances CS ₁ to CS ₅ caused imbalance in voltage sharing among the thyristors S ₁ to _{S 5} . Second
The figure shows the above relationship with the number of thyristor S on the horizontal axis and the voltage sharing ratio on the vertical axis, with the ratio of the voltage equal sharing capacitor C and the distributed capacitance CS as a parameter k. Here, the voltage sharing ratio is the voltage actually shared by each thyristor S based on the voltage that each thyristor S would share if it were assumed that each thyristor S shared the voltage equally. It is a percentage. Figure 2a shows the case where a switch consisting of five switch elements is used.
FIG. 2b shows the case where a switch consisting of 25 switch elements is used. It can be seen from FIGS. 2a and 2b that the larger the number of switch elements, the greater the influence of distributed capacitance. For practical use, when the number of switch elements is 5, the capacitances of capacitors C ₁ to _{C 5} should be changed to the distributed capacitances of CS ₁ to CS ₅ according to Figure 2 a.
It is necessary to increase the number of switch elements from 100 to 300 times or more, and if the number of switch elements is 25, the capacitor
The capacitance of C ₁ to _{C 5} is converted to the distributed capacitance of CS ₁ to _{CS 5} .
It is necessary to increase the magnification by about 3,000 to 10,000 times or more.
In any case, a high voltage generator equipped with a switch consisting of a large number of switch elements connected in series has the drawback of requiring a fairly large capacitance as a voltage sharing capacitor.

The present invention provides a novel high voltage generator that eliminates all of the above drawbacks.

〔Example〕

FIG. 3 is a diagram showing an embodiment of the present invention. In the same figure, 3 is a capacitor CW ₁ ~CW ₅ , C′W ₁ ~
This is a Kotscroft-Walton circuit consisting of C'W ₅ and diodes D ₁ to D ₁₀ , and each capacitor CW ₁ to
CW ₅ is connected in parallel with each thyristor S ₁ to S ₅ , respectively. In the same figure, the distributed capacitance CS ₁ to _{CS 5}
is directly charged by the DC side capacitors CW ₁ to CW ₅ of the Kotsukucroft-Walton circuit,
In addition, since the terminal voltage of each capacitor CW ₁ to _{CW 5} does not exceed twice the peak value of the secondary side voltage of the step-up transformer 2, it is possible to achieve better equal voltage sharing than in the past. At the same time, the capacitors C ₁ to _{C 5} for equal voltage sharing become unnecessary. Therefore, it greatly contributes to improving performance, downsizing the entire device, and reducing manufacturing costs.

FIG. 4 is a diagram showing another embodiment of the present invention. In the same figure, 3 is a capacitor CW ₁ to CW ₁₀ ,
This is a Kotsukucroft-Walton circuit consisting of C′W ₁ to C′W ₁₀ and diodes D ₁ to D ₁₀ .
Two thyristors CW ₁ to CW ₁₀ are connected to each thyristor S ₁ to
Connected in parallel with S ₅ . Also in the same figure, substantially the same effect as explained in FIG. 3 can be obtained.
In this embodiment, the case has been described in which the number of rectification stages of the Kotsukucroft-Walton circuit 3 is twice the number of thyristors S, but the same applies if the number of rectification stages of the Kotsukucroft-Walton circuit 3 is an integral multiple of the number of thyristors. can be carried out, and almost the same effect can be obtained.

Next, FIG. 5 is a diagram showing another embodiment of the present invention. In the same figure, 3 is a capacitor CW ₁ ~
This is a Kotscroft-Walton circuit consisting of CW ₅ , C'W ₁ to C'W ₅ and diodes D ₁ to _{D 10} , and each capacitor CW ₁ to _{CW 5} on the DC side of the Kotscroft-Walton circuit is pcs thyristor S ₁ ~
It is connected in parallel with switch 13 consisting of _S5 . Here, assuming that the values of the distributed capacitances CS ₁ to CS ₅ are all equal and the capacitances of the capacitors C ₁ to _{C 5} for equal voltage sharing are all equal, the potentials V ₁ to _{V 5} of the Kotsukucroft-Walton circuit 3 are Since the voltage is shared by the DC side capacitors CW ₁ to _{CW 5} , the capacitance required for the capacitors C ₁ to C ₅ can be 100 to 300 times the distributed capacitance CS ₁ to CS ₅ , as shown in FIG. 2a.
On the other hand, if this circuit were constructed using the conventional circuit described in Figure 1, the capacitance required for the voltage equalization capacitor would be 3000 to 10000 times the distributed capacitance, as shown in Figure 2b. Therefore, a capacitor with a capacitance approximately 30 times larger than that of this embodiment must be used. In the above embodiment, a Kotscroft-Walton circuit was used as the DC high voltage generator 3, but a Schenkel circuit, a cascade transformer type multi-stage boost rectifier circuit, a multi-stage boost rectifier circuit formed by a combination thereof, etc. may also be used. Good too.

[Effect of idea]

As described above, the present invention includes a high voltage generator that outputs a DC high voltage using a multi-stage booster circuit, a high voltage electrode charged by the high voltage generator, and a gap between the high voltage generator and the high voltage electrode. In a high voltage generator comprising at least a switch consisting of a plurality of switch elements connected in series between a high voltage line and a low voltage terminal, a switch is connected between one or more of the capacitors constituting the multistage boost circuit. This is a high voltage generator characterized by connecting the above switch elements. Since the present invention has such features, it is possible to easily equalize the voltage shared by each switch element, and there is no need for a capacitor for voltage equalization, or even if it is necessary, it is far fewer than before. A capacitor is sufficient. Therefore, improved performance,
This greatly contributes to downsizing the entire device and reducing manufacturing costs.

[Brief explanation of the drawing]

Figure 1 shows a conventional high voltage generator, Figure 2 shows a conventional high voltage generator.
The figure shows the voltage sharing ratio of each switch element using the ratio of the voltage equalization capacitor to the distributed capacitance as a parameter, and a and b are for switches consisting of 5 and 25 switch elements, respectively. This is the case when using . FIGS. 3 to 5 are diagrams each showing an embodiment of the present invention. 1... AC power supply, 2... Step-up transformer, 3...
...DC high voltage generation circuit, 5...Current limiting resistor, 6...
Discharge diode, 7... High voltage electrode, 8... Object to be painted, 9... Current detection circuit, 10... Spark discharge occurrence prediction circuit, 11... Pulse generation circuit, 12...
...Pulse transformer, 13...Switch, S ₁ ~ S ₅ ...
...Switch element.

Claims (1)

[Scope of utility model registration request] A high voltage generator that outputs DC high voltage using a multi-stage booster circuit, a high voltage electrode charged by the high voltage generator, and a high voltage line between the high voltage generator and the high voltage electrode and a low voltage terminal. A high voltage generator comprising at least a switch consisting of a plurality of switches connected in series, characterized in that one or more switch elements are connected to both ends of a capacitor constituting the multi-stage booster circuit.