JPH114582A - Dc high-voltage generation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To switch the polarity quickly, by providing a rectification element branch that can be used as a path for discharging an electric charge stored in a capacitor branch and a load, breaking the power supply of a charge transformer when a polarity is inverted, and switching a polarity selection switch while the electric charge remains. SOLUTION: When a positive polarity is outputted, a capacitor branch 1 is charged to (+) and (-) (a). After the power supply of a transformer 2 for charging is broken by a switch 7 (b), a polarity selection switch 3 is switched (b). At this time, currents i1 and i2 are fed from the capacitor branch 1 to a rectification element branch 4 and current i3 is fed from the load to the branch 4 for discharging. In this case, the current element branch 4 has a sufficient capacity for (i1 +i2 +i3 ). An electric charge stored in the capacitor branch/load is discharged through the rectification branch 4 instead of a leakage resistor, thus reducing a discharge constant, eliminating the need for a long discharge time, discharging remained electric charge quickly, and switching polarity quickly.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a Cockcroft-Walton DC high voltage generator for use in withstand voltage tests and the like, and more particularly to a high voltage generator capable of switching the polarity of an output voltage.

[0002]

2. Description of the Related Art Generally, in a Cockcroft-Walton type high voltage generator, the polarity of an output voltage is determined by the direction of a rectifying element. FIG. 11 shows a Cockcroft circuit having three stages of positive output. Here, the charging transformer (2) is composed of a capacitor branch (1) and a rectifying element branch (4). The left capacitor branch group is a "push-up column" (101) The right capacitor branch group is a "smoothing column" ( Call it 100). When AC power is applied to the charging transformer, the tip (5) of the smoothing column becomes an output terminal, and generates a DC output of about 2N times (N: the number of stages) the peak value of the output voltage of the charging transformer. This terminal (5) is connected to a load (8) such as a withstand voltage test device.

When the direction of the rectifying element branch (4) is operated as shown in FIG. 12, a negative high voltage is generated at the output terminal (5). As shown in FIG. 13, the polarity selection switch (3)
The circuit can be switched between the same as in FIG. 11 and the same as in FIG.

[0004]

However, in order to reduce the loss and achieve high efficiency, such a high-voltage generator is designed to have high insulation of each branch. Even if the power of the transformer is cut off, the electric charge of the capacitor branch is not easily discharged.
Therefore, it is necessary to turn on the power to the transformer after switching the polarity selection switch for a long time after the power is cut off. Although it was sufficiently effective when conducting either a positive or negative polarity test, a power supply that reverses its polarity in a short time to verify its withstand voltage, although the polarity reverses in a short time like DC power transmission, was used. Where needed, it could not be applied. SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to provide a DC high voltage generator capable of inverting output polarity in a short time.

[0005]

The invention according to claim 1 comprises a capacitor branch and a rectifying element branch having the ability to be used as a path for discharging charges stored in a load.
Therefore, when reversing the polarity, it is possible to switch the polarity selection switch in a state where the charge remains after the power supply of the charging transformer is cut off, and the polarity can be switched in a short time.

According to a second aspect of the present invention, a discharge of a capacitor branch is performed by utilizing a series impedance such as an inductance or a resistance inserted between a load and a power supply for the purpose of current limiting protection when a load is short-circuited. The current is temporally separated from the discharge of the load, and the capacity of the rectifying element branch can be reduced.

According to a third aspect of the present invention, since the polarity switching operation is performed intentionally, a switch for changing the series impedance between the switching time and the normal time is provided, so that the current limiting performance at the time of load short circuit is provided. Can be maintained.

According to a fourth aspect of the present invention, the capacity of the rectifying element can be reduced by inserting impedance such as inductance or resistance in order to limit the peak value of the discharge current in series with the rectifying element.

According to a fifth aspect of the present invention, since the polarity inversion is intentionally performed similarly to the third aspect, the circuit according to the fourth aspect does not include the series impedance except at the time of switching. In addition, the efficiency of the high voltage generator can be maintained.

In the invention corresponding to claim 6, since the changeover switch of claim 5 operates at the same time as the polarity selection switch, the same function as in claim 5 is provided by one four-point selection switch. Obtainable.

[0011]

Embodiments of the present invention will be described below. FIG. 1 is a diagram showing a first embodiment of the present invention,
An example of a three-stage Cockcroft-Walton circuit is shown.

FIG. 2 shows the switching operation from the positive polarity to the negative polarity according to the present invention. In the case of the positive output, the capacitor branch (1) has the (+) (-) charge as shown in FIG. Is charged. Here, the power supply of the charging transformer (2) is cut off by the switch (7) (FIG. 2 (b)). Thereafter, the polarity selection switch (3) is switched as shown in FIG. At this time, a current i ₁ flows from the capacitor branch (1) and a current i ₃ flows from the i ₂ load to the rectifying element branch (4), and discharges.

Here, the rectifying element branch (4) is (i ₁ + i ₂
+ I ₃ ). In this way, the electric charge stored in the capacitor branch / load is discharged not through the leakage resistance but through the rectifying element branch (4), so that the discharge time constant is short and a long discharge time is not required.

Thereafter, as shown in FIG. 2D, the power is turned on to the charging transformer to output a negative polarity. As described above, according to the present embodiment, the remaining charges can be discharged in a short time, so that it is possible to obtain a DC voltage generator capable of switching the polarity in a short time.

FIG. 3 shows a second embodiment of the present invention. A series impedance (9) is inserted between the output terminal (5) and the load (8). With this impedance, the waveform Z _S of the discharge current i ₃ of the load can be changed. Here by the time constant of the i ₃ of waveform selecting the impedance to more than three times the time constant of the i _1, i ₂ of the waveform, i _1, i 1/20 or less ₂ waveform peak [ exp (-3) = 0.05] is i ₃ when they are flowing. For this reason, as shown in FIG. 4A, the wave having the peaks of i ₁ and i ₂ and the wave having the peak of i ₃ are separated in time, and as compared with the case where the peaks overlap as shown in FIG. 4B. The peak value of the total current flowing through the rectifying element branch can be reduced.

As described above, according to this embodiment, the peak value of each discharge can be reduced, so that the capacity of the rectifying element can be reduced and the device can be downsized. Next, FIG. 5 shows a third embodiment of the present invention.

The series impedance Z ₃ shown in FIG.
(9) is shown, and the sum of the series impedance Z _A (10) and the series impedance Z _B (11) is shown in FIG.
(Z _S = Z _A + Z
_B ). The series impedance Z _A (10) has a current limiting series impedance value necessary to prevent an excessive current from flowing from the DC power supply when a short circuit fault occurs in the test load. Switch (13) during normal operation impedance between PQ becomes short-circuited state is equal to the Z _A.

After the charging transformer is shut off during the polarity switching, the switch (13) is opened, the impedance between the PQs is set to (Z _A + Z _B ), and the polarity selection switch (3) is switched. perform the discharge, the impedance between PQ and Z _a again closing the switch (13).

Here, when the method of Z _A is larger than the series impedance (9) shown in FIG. 3 and Z _B must be minus, a configuration as shown in FIG. 6 is obtained. That is, the switch (16) that divides Z _A into Z _S and (Z _A −Z _S ) and connects the switch (16) in parallel with the impedance of (Z _A −Z _S ) is generally opposite to the switch (13). It becomes an open state at the time and short circuit occurs during the polarity switching.

As described above, according to the present embodiment, the value of the series impedance can be changed only during the polarity switching, so that it functions as the optimum series impedance for both the polarity switching and the load short circuit, and the impedance ( Since the loss due to the resistance component in Z _B ) is eliminated, the efficiency of the high voltage generator is also improved.

Next, FIG. 7 shows a fourth embodiment of the present invention. An impedance Z _C (18) is inserted into the rectifying element branch (4) in series with the rectifying element (17). This impedance makes it possible to change the waveforms of the discharge currents i ₁ and i ₂ of the capacitor branch (1) and the discharge current i ₃ of the load (8) to lower the peak value. Thus, the peak value of the total current flowing through the rectifier can be reduced.

As described above, according to the present embodiment, the peak value of each discharge can be reduced, so that the capacity of the rectifying element can be reduced and the device can be downsized. Next, FIG. 8 shows a fifth embodiment of the present invention.

FIG. 7 shows a portion of the rectifying element branch (4) shown in FIG. 7 (rectifying element (17) + impedance Z _C (18)), and the impedance Z _C (18) and the switch (19) are shown.
Are connected in parallel, and are connected in series with the rectifying element (17). The switch (19) is in a short-circuit state during normal operation, and is equivalent to connecting only the rectifying element (17) between the RSs. After the charging voltage is shut off during the polarity switching, the switch (19) is opened and the rectifying element (17) and the impedance Z _C (18) are connected in series between the RSs. (3) is switched to discharge the residual charge, and the switch (19) is closed again to make only the rectifying element (17) between the RSs.

According to this embodiment as described above, it is possible to give the impedance Z _C only the rectifying element in series between the polarity switching, eliminates the loss due to the resistance component in the impedance Z _C of the high voltage generator Efficiency is also improved.

Next, FIG. 9 shows a sixth embodiment of the present invention.
The polarity switching selection switch (20) is a four-point selection switch, and the impedance Z _C (1
8) is not a rectifier element branch, but a polarity switch (2)
It is inserted between (0) and the smooth column (100). FIG. 10 shows the operation of the present invention when switching the polarity from the positive polarity to the negative polarity.

At the time of the positive polarity output, the rectifying element (17) is connected to the U end of the capacitor branch by the polarity switching selection switch (20). (FIG. 10a). When switching the polarity, the power supply (6) of the charging transformer (2) is cut off by the switch (7) (FIG. 10b). Next, the impedance Z connected to the rectifying element branch and the U-end by the polarity switching selection switch (20).
After connecting the U 'end of _C (18) (FIG. 10c), the rectifying element (17) is connected to the V' end of the impedance Z _C (18) connected to the V end (FIG. 10d). Thereby residual charge flows to the rectifier element via an impedance Z _C. Finally, after the polarity switch is connected to the V terminal (FIG. 10E), the power is turned on.

As described above, according to the present embodiment, it is possible to discharge the electric charge in a short time by a series of selection switching, so that it is possible to switch the polarity in a short time, and to obtain a DC voltage generator which is easy to operate. it can.

[0028]

As described above, according to the present invention,
It is possible to provide a DC high voltage generator capable of switching the polarity within a short time.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of a first embodiment of the present invention.

FIG. 2 is a view showing the operation of the first embodiment of the present invention.

FIG. 3 is a circuit diagram according to a second embodiment of the present invention.

FIG. 4 is a diagram showing the operation of the second embodiment of the present invention.

FIG. 5 is a circuit diagram according to a third embodiment of the present invention.

FIG. 6 is a diagram showing the operation of the third embodiment of the present invention.

FIG. 7 is a circuit diagram according to a fourth embodiment of the present invention.

FIG. 8 is a circuit diagram according to a fifth embodiment of the present invention.

FIG. 9 is a circuit diagram according to a sixth embodiment of the present invention.

FIG. 10 is a diagram illustrating the operation of the sixth embodiment of the present invention.

FIG. 11 is a conventional positive polarity output circuit diagram.

FIG. 12 is a conventional negative output circuit diagram.

FIG. 13 is a conventional polarity output circuit diagram provided with a polarity selection switch.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Capacitor branch 2 Charging transformer 3 Polarity selection switch 4 Rectifier element branch 100 Smooth running column 101 Push-up column

Claims (6)

[Claims] A capacitor branch stacked in series;
A polarity-switching Cockcroft-Walton DC high voltage generator having a charging transformer, a rectifying element branch, and a switch capable of switching the connection of the rectifying element branch to select either positive or negative output DC voltage. At the time when the input of the charging transformer becomes 0 while the capacitor branch and the load of each stage leave the charge to be charged during the rated operation, the capacitor flowing when the direction of the rectifying element branch is switched by the switch. A polarity switching type DC high voltage generator, characterized by using a rectifying element branch having a capacity to withstand a discharge flow of a branch and a load. 2. The high-voltage generator according to claim 1, wherein the value of the series impedance inserted between the high-voltage generator and the load is three times the discharge time constant of the load than the discharge time constant of the capacitor branch. A high-voltage generator selected as described above. 3. The high-voltage generator according to claim 2, wherein the series impedance to be inserted is divided into a series impedance necessary for current-limiting protection in the event of a short-circuit fault of a load and a difference between the two. A high-voltage generator having a switch that is short-circuited and opened only when the polarity is switched. 4. The high-voltage generator according to claim 1, wherein an impedance for limiting a peak value of the discharge current is inserted in series with the rectifier element in the rectifier element branch. 5. The high-voltage generator according to claim 4, wherein a switch that normally short-circuits and opens only when switching the polarity is inserted in parallel with the peak value limiting impedance. 6. The high-voltage generator according to claim 1, wherein the polarity changeover switch is a four-point selection type, and a connection destination of the rectifying element branch is a first peak value limiter connected to one end of the capacitor branch. A high voltage, wherein the impedance is switched in the order of the other end of the second peak value limiting impedance connected to the other end of the capacitor branch, the other end of the capacitor branch, and in reverse order. Generator.