JP7267162B2 - DC power supply circuit - Google Patents

Description

The present invention relates to a DC power supply circuit.

For example, a plasma generation circuit uses a high-voltage DC power supply circuit to generate a high-voltage DC voltage. As an example, such a DC power supply circuit has a configuration in which a DC voltage is converted into AC of a predetermined voltage value by an inverter or a transformer, and then further rectified by a rectifier circuit to be converted into a DC voltage of a desired voltage value. have.

A rectifier circuit included in such a DC power supply circuit may include a current sensor for detecting a current flowing through the rectifier circuit. When a load short-circuit occurs, the short-circuit current may damage the current sensor or diode, and further damage the primary side circuit as secondary damage to the damage of the current sensor.

Japanese Unexamined Patent Application Publication No. 2011-115032

SUMMARY OF THE INVENTION It is an object of the present invention to provide a DC power supply circuit that can prevent damage to a current sensor and diodes due to a short-circuit current even when a load short-circuit occurs.

In order to solve the above problems, a DC power supply circuit according to the present invention is a DC power supply circuit that outputs a DC voltage from an output terminal, comprising an inverter circuit that converts a DC input voltage into a first AC voltage; a transformer that converts one AC voltage into a second AC voltage; a rectifier circuit that rectifies the second AC voltage and converts it into a DC voltage; short-circuit current suppressing means connected to an output terminal of the rectifier circuit; a current sensor connected to short-circuit current suppressing means; a determination circuit for determining whether or not a detection output of the current sensor exceeds a predetermined threshold; and a control circuit that controls to stop the output from the output terminal or to reduce the output from the output terminal when it is determined that the threshold is exceeded.

According to the present invention, it is possible to provide a DC power supply circuit that can prevent the current sensor and diode from being damaged by a short-circuit current.

1 is a circuit diagram illustrating a configuration of a DC power supply circuit according to a first embodiment of the invention; FIG. It is a circuit diagram explaining the structure of the DC power supply circuit which concerns on the 2nd Embodiment of this invention. It is a circuit diagram explaining the structure of the DC power supply circuit based on the 3rd Embodiment of this invention. It is a circuit diagram explaining the structure of the direct-current power supply circuit based on the 4th Embodiment of this invention. It is a circuit diagram explaining the structure of the DC power supply circuit based on the 5th Embodiment of this invention. It is a circuit diagram explaining the structure of the DC power supply circuit which concerns on the 6th Embodiment of this invention.

Hereinafter, this embodiment will be described with reference to the accompanying drawings. In the accompanying drawings, functionally identical elements may be labeled with the same numbers. It should be noted that although the attached drawings show embodiments and implementation examples in accordance with the principles of the present disclosure, they are for the purpose of understanding the present disclosure and are in no way used to interpret the present disclosure in a restrictive manner. isn't it. The description herein is merely exemplary and is not intended to limit the scope or application of this disclosure in any way.

Although the present embodiments are described in sufficient detail to enable those skilled in the art to practice the present disclosure, other implementations and configurations are possible without departing from the scope and spirit of the present disclosure. It is necessary to understand that it is possible to change the composition/structure and replace various elements. Therefore, the following description should not be construed as being limited to this.

[First embodiment]
A DC power supply circuit 1 according to a first embodiment of the present invention will be described with reference to FIG. This DC power supply circuit 1 includes an inverter circuit 10 , a transformer 20 , a rectifier circuit 30 , a current sensor 40 and a low-pass filter circuit 50 .

The inverter circuit 10 has a configuration in which two arm circuits 11 and 12 are connected in parallel, and has a function of converting a DC input voltage into an AC voltage. The arm circuit 11 has a structure in which semiconductor switching elements Q1 and Q2 are connected in series, and the arm circuit 12 has a structure in which semiconductor switching elements Q3 and Q4 are connected in series.

The semiconductor switching elements Q1 to Q4 are, for example, elements each formed by connecting a transistor and a diode in antiparallel. The diodes may be physically independent diodes or body diodes of the semiconductor switching elements Q1 to Q4, and are appropriately designed according to the inverter circuit 10. FIG. Gate signals VQ1-VQ4 are applied to the gates of semiconductor switching elements Q1-Q4, whereby semiconductor switching elements Q1-Q4 are switched between a conducting state and a non-conducting state. The gate signal VQ2 is an inverted signal of the gate signal VQ1, thereby controlling the semiconductor switching elements Q1 and Q2 so that only one of them is alternately turned on and not turned on at the same time. Similarly, the gate signal VQ4 is an inverted signal of the gate signal VQ3, thereby controlling the semiconductor switching elements Q3 and Q4 so that only one of them is alternately turned on and not turned on at the same time.

The transformer 20 includes inductors L1, L2, a primary coil L3, and a secondary coil L4. Inductor L1 is connected between output node O1 of inverter circuit 10 and primary coil L3, and inductor L2 is connected in parallel with primary coil L3. The transformer 20 transforms the input voltage with a transformation ratio according to the winding ratio of the primary coil L3 and the secondary coil L4, and outputs an output voltage.

As an example of the rectifier circuit 30, the Cockcroft-Walton circuit shown in FIG. 1 can be employed. A Cockcroft-Walton circuit is a circuit that receives an AC voltage and generates a high-voltage DC voltage corresponding to the number of stages.

Since the Cockcroft-Walton circuit of the example of FIG. 1 has a four-stage voltage amplifier circuit, a DC voltage having a value four times the peak value of the input voltage from the transformer 20 is output from the output terminal O3. be able to. Therefore, by grounding the output terminal O3, the output terminal O4 can function as a negative output terminal, and a negative DC voltage can be output from the output terminal O4. That is, the output terminal O3 and the output terminal O4 can be used as the output terminals of the DC power supply circuit 1 to supply a negative DC voltage to the load.

Note that the Cockcroft-Walton circuit is a circuit suitable for generating a high voltage, and by adjusting the number of stages of the voltage amplifier circuit, it is possible to generate a high voltage according to the characteristics of the load. Of course, as shown in FIG. 1, it is possible not only to output a negative DC voltage, but also to output a positive DC voltage from the output terminal O3 by changing the configuration of the Cockcroft-Walton circuit. In this case, the output terminal O4 is grounded. Therefore, the Cockcroft-Walton circuit can output any DC voltage in the range of -several kV to +several kV, for example. In some cases, a DC voltage in the range of -10 kV to +10 kV is output, so the circuit is designed according to the application.

The Cockcroft-Walton circuit as the rectifier circuit 30 includes a current sensor 40 between the output terminal N1 and the output terminal O4 of the first stage of the four-stage voltage amplifier circuit, for example. Current sensor 40 detects the current flowing through rectifier circuit 30 . The detection output of current sensor 40 is compared with threshold current Ith in determination circuit 200 , and the comparison result is fed back to control circuit 300 of inverter circuit 10 . Thereby, the output voltage of the DC power supply circuit 1 is adjusted.

When the determination circuit 200 determines that the detection output (detection current) of the current sensor 40 is greater than the threshold current Ith, the control circuit 300 either stops the output of the inverter circuit 10 or reduces the output of the inverter circuit 10. is controlled so as to reduce the switching of the semiconductor switching elements Q1 to Q4. Although omitted in FIG. 1, a voltage sensor for detecting the output voltage of the DC power supply circuit 1 (the voltage between the output terminal O3 and the output terminal O4 in the case of FIG. 1) is provided, and this voltage sensor The control circuit 300 may control the switching of the semiconductor switching elements Q1 to Q4 so that the detected voltage detected by is equal to the set voltage. With this configuration, when the determination circuit 200 determines that the detected output (detected current) of the current sensor 40 is larger than the threshold current Ith, the control circuit 300 stops the output of the inverter circuit 10, or Alternatively, the switching of the semiconductor switching elements Q1 to Q4 is controlled so that the output of the inverter circuit 10 is lowered. On the other hand, when the determination circuit 200 determines that the detected output (detected current) of the current sensor 40 is equal to or less than the threshold current Ith, the control circuit 300 performs semiconductor switching so that the detected voltage detected by the voltage sensor becomes the set voltage. It controls the switching of the elements Q1-Q4.

A low-pass filter circuit 50 is also connected to the current sensor 40 . The low-pass filter circuit 50 is configured by an inductor L21 and a capacitor C21, for example. An inductor L21 is connected between the output terminals N1 and O4, and a capacitor C21 is connected between the output terminals O3 and O4, ie in parallel with the load. As a result, inductor L21 and capacitor C21 function as a low-pass filter. As will be described later, the inductor L21 has the effect of suppressing a rapid increase in short-circuit current, but also functions as a filter together with the capacitor C21 and has the effect of suppressing ripples. In FIG. 1, the inductor L21→current sensor 40→output terminal O4 is connected in the order of the output terminal N1, but the order of connection of the inductor L21 and the current sensor 40 may be reversed.

When a load having a resistance value equal to or greater than a certain value is connected between the output terminals O3 and O4, the current detected by the current sensor 40 is normally less than the reference value. However, when a load short circuit occurs, the short circuit current flowing through the current sensor 40 may exceed the reference value.

Here, consider the case where the low-pass filter circuit 50 is not present and the current sensor 40 is directly connected to the output terminal N1. That is, consider the case where only the current sensor 40 is connected between the output terminal N1 and the output terminal O4. In this case, a short-circuit current exceeding the reference value may flow through the current sensor 40 . For example, if the rectifier circuit 30 is the Cockcroft-Walton circuit shown in FIG. 1, the Cockcroft-Walton circuit includes only a capacitor and a diode, so it is difficult to suppress the short-circuit current in the internal configuration of the Cockcroft-Walton circuit. is. That is, in the Cockcroft-Walton circuit of FIG. 1, for example, a short-circuit current path including capacitors C12, C14, and current sensor 40 is formed as a first short-circuit current path, and a current sensor 40 and diode D11 are formed as a second short-circuit current path. . . , D14, capacitor C11, and secondary coil L4. A short-circuit current path including the capacitors C11 and C13 is formed as the third short-circuit current path.

More specifically, in the initial stage after the load short-circuit, among the capacitors C12 to C14, the capacitors C12 and C14 start discharging first, so the short-circuit current flows along the first short-circuit current path. When the discharge of the capacitors C12 and C14 causes the voltage across the diodes to drop to a voltage at which the diodes D11 to D14 can conduct, a short-circuit current also flows through the second short-circuit current path. Then, the capacitors C11 and C13 also start discharging, so that the short-circuit current also flows through the third short-circuit current path. Therefore, the short-circuit current can flow in the order of the first short-circuit current path, the second short-circuit current path, and the third short-circuit current path. Such a short-circuit current may cause destruction of the current sensor 40 . In particular, when the potential difference between the output terminals O3 and O4 is large, an excessive short-circuit current flows, and the current sensor 40 is easily damaged.

In order to suppress such a short-circuit current, the DC power supply circuit 1 of the first embodiment connects the low-pass filter circuit 50 in series with the current sensor 40 . According to this low-pass filter circuit 50, even when a load short circuit occurs, the action of the inductor L21 included in the low-pass filter circuit 50 can suppress a rapid increase in the short-circuit current. Diode damage can be prevented. Therefore, the inductor L21 functions as a short-circuit current suppression means.

If the voltage across the inductor L21 is VL and the magnetic path length of the inductor L21 is L, the slope di/dt of the short-circuit current can be expressed as di/dt=VL/L. That is, since the short-circuit current rises with a constant slope according to the magnetic path length L, a rapid increase in the short-circuit current can be suppressed.

It should be noted that when the short-circuit current increases to a predetermined value or more, the inductor L21 may be saturated, thereby making it impossible to suppress the increase in the short-circuit current. In order to prevent this, it is preferable to design the inductor L21 so that the magnetic flux density B generated in the inductor L21 when the short-circuit current Is flows is equal to or lower than the saturation magnetic flux density Bm.

For example, when the number of turns of the inductor L21 is N and the magnetic path length of the inductor L21 is L, the magnetic flux density B generated when the short-circuit current Is flows can be expressed by the following equation. It is required that B does not exceed the saturation magnetic flux density Bm.
B=μH=μN・Is/L (A/m)

By giving a predetermined air gap to the core material (ferrite core, dust core, etc.) of the inductor L21 or by adopting an air-core structure, the inductor is less likely to be saturated even when a large short-circuit current Is occurs. It is possible to

Note that the peak value Ismax of the short-circuit current Is is determined by limiting the output voltage of the inverter circuit 10 according to the detection result after the current sensor 40 detects the short-circuit current Is of a predetermined value or more, thereby reducing the short-circuit current Is. It changes depending on the time it takes to turn. It is preferable to obtain the peak value Ismax and set the number of windings N, the magnetic path length L, etc. so that the inductor L21 does not saturate even when the short-circuit current Is reaches the peak value Ismax. Moreover, it is preferable to design the control circuit so that the peak value Ismax does not exceed the rated current of the current sensor 40, the breakdown tolerance of the diode, and the like.

[Second embodiment]
Next, a DC power supply circuit 1 according to a second embodiment of the present invention will be described with reference to FIG. A DC power supply circuit 1 of the second embodiment includes an inverter circuit 10, a transformer 20, a rectifier circuit 30, a current sensor 40, and a low-pass filter circuit 50, as in the first embodiment. The configurations of the inverter circuit 10 and the transformer 20 are the same as those of the first embodiment.
In addition, in FIG. 2, the low-pass filter circuit 50 is configured by an inductor L21' and a capacitor C21'. Therefore, the inductor L21' functions as a short-circuit current suppression means.

However, unlike the first embodiment, the rectifier circuit 30 is configured by a voltage doubler rectifier circuit. As shown in FIG. 2, the voltage doubler rectifier circuit includes a series circuit of diodes D31 and D32 and capacitors C31 and C32 connected in parallel therewith. The output terminal of the transformer 20 is connected to a connection node N11 between the two diodes D31 and D32 and a connection node N12 between the capacitors C31 and C32.

With this configuration, the voltage doubler rectifier circuit can output a DC voltage that is twice the peak value of the AC voltage output from the transformer 20 . Other configurations are the same as those of the first embodiment. Also in the configuration of the second embodiment, the short-circuit current is suppressed by the low-pass filter 50, thereby preventing the current sensor and diode from being damaged by the short-circuit current.

[Third embodiment]
Next, a DC power supply circuit 1 according to a third embodiment of the present invention will be described with reference to FIG. A DC power supply circuit 1 of the third embodiment includes an inverter circuit 10, a transformer 20, a rectifier circuit 30, and a current sensor 40, as in the first embodiment. The configurations of the inverter circuit 10, the transformer 20, and the rectifier circuit 30 are the same as in the first embodiment. However, in this third embodiment, instead of the low-pass filter circuit 50, a resistance element R21 is connected in series with the current sensor 40. FIG.

By connecting the resistance element R21, even when a load short circuit occurs, the voltage drop across the resistance element R21 causes a sudden short-circuit current, similar to the low-pass filter circuit 50 in the first embodiment. It is possible to suppress the increase, thereby preventing damage to the current sensor and the diode due to the short-circuit current. Therefore, the resistance element R21 functions as a short-circuit current suppressing means.

When the voltage across the resistance element R21 is VL and the magnetic path length of the resistance element R21 is L, the slope di/dt of the short-circuit current can be expressed as di/dt=VL/L. That is, since the short-circuit current rises with a constant slope according to the magnetic path length L, a rapid increase in the short-circuit current can be suppressed.

[Fourth embodiment]
Next, a DC power supply circuit 1 according to a fourth embodiment of the present invention will be described with reference to FIG. A DC power supply circuit 1 of the fourth embodiment includes an inverter circuit 10, a transformer 20, a rectifier circuit 30, a current sensor 40, and a low-pass filter circuit 50, as in the first embodiment. The configurations of the inverter circuit 10, the transformer 20, and the rectifier circuit 30 are the same as in the first embodiment. However, in the fourth embodiment, the low-pass filter circuit 50 includes a resistive element R21'' in addition to the inductor L21'' and capacitor C21'. In the current sensor 40, not only the inductor L21'' but also the resistance element R21'' are connected in series. Therefore, the combination of the inductor L21'' and the resistance element R21'' functions as a short-circuit current suppressing means.

According to the low-pass filter circuit 50, even when a load short-circuit occurs, the action of the inductor L21'' and the resistance element R21'' included in the low-pass filter 50 can suppress a rapid increase in short-circuit current. . When a short-circuit current occurs, the short-circuit current rises with a constant slope according to the impedance of the inductor L21'' and the resistance element R21'', so a rapid increase in the short-circuit current can be suppressed.

[Fifth embodiment]
Next, a DC power supply circuit 1 according to a fifth embodiment of the present invention will be described with reference to FIG. A DC power supply circuit 1 of the fifth embodiment includes an inverter circuit 10, a transformer 20, a rectifier circuit 30, a current sensor 40, and a low-pass filter circuit 50, as in the first embodiment. The configurations of the inverter circuit 10, the transformer 20, and the rectifier circuit 30 are the same as in the first embodiment. However, in this fifth embodiment, the low-pass filter circuit 50 includes a resistance element R21a in addition to the inductor L21a and the capacitor C21a. This resistance element R21a is connected between the output terminals O3 and O4, unlike the fourth embodiment.

According to the low-pass filter circuit 50, even when a load short-circuit occurs, the action of the inductor L21a included in the low-pass filter circuit 50 can suppress a rapid increase in short-circuit current. Therefore, the inductor L21a functions as a short-circuit current suppression means.

[Sixth embodiment]
Next, a DC power supply circuit 1 according to a sixth embodiment of the present invention will be described with reference to FIG. FIG. 6 is a partial circuit diagram illustrating the current path of the current sensor 40, which is different from the first embodiment.

The DC power supply circuit 1 of the sixth embodiment is not shown in FIG. , and a filter circuit 50 . The configurations of the inverter circuit 10, the transformer 20, the rectifier circuit 30, and the low-pass filter circuit 50 are the same as those of the first embodiment. However, in this sixth embodiment, a switching circuit Q5 is connected in series with the current sensor 40. FIG. A control circuit 60 is provided as a circuit for controlling switching of the switching circuit Q5 between the conducting state and the non-conducting state. A control circuit (not shown) similar to the control circuit 300 (see FIG. 1) of the first embodiment is also provided. This control circuit (not shown) controls the semiconductor switching elements Q1 to Q4 so that the detected voltage detected by an unillustrated voltage sensor (a sensor that detects the voltage between the output terminal O3 and the output terminal O4) becomes the set voltage. control the switching of However, unlike the control circuit 300 of the first embodiment, it does not have the function of controlling the switching of the semiconductor switching elements Q1 to Q4 based on the determination result of the determination circuit 200. FIG.

When a load short-circuit occurs, the short-circuit current flowing through the current sensor 40 increases. However, when the short-circuit current increases and the magnetic flux density B of the inductor L21 in the low-pass filter circuit 50 exceeds the saturation magnetic flux density Bm, the inductance of the inductor L21 decreases, thereby accelerating the increase of the short-circuit current. obtain.

Therefore, in the sixth embodiment, the determination circuit 200 compares the output signal of the current sensor 40 with the threshold current Ith, and cuts off the switching circuit Q5 when an output signal exceeding the threshold current Ith is observed. . Thereby, the short-circuit current is interrupted, and the current sensor 40 can be protected.

The present invention is not limited to the above-described embodiments, and includes various modifications. For example, the above-described embodiments have been described in detail in order to explain the present invention in an easy-to-understand manner, and are not necessarily limited to those having all the configurations described. Also, part of the configuration of one embodiment can be replaced with the configuration of another embodiment, and the configuration of another embodiment can be added to the configuration of one embodiment. Moreover, it is possible to add, delete, or replace part of the configuration of each embodiment with another configuration.

Reference Signs List 1 DC power supply circuit 10 Inverter circuit 11, 12 Arm circuit 20 Transformer 30 Rectifier circuit 40 Current sensor 50 Low-pass filter circuit 60 Control circuit 200 Determination circuit 300 .

Claims (5)

A DC power supply circuit that outputs a DC voltage from an output terminal,
an inverter circuit that converts a DC input voltage into a first AC voltage;
a transformer that converts the first alternating voltage to a second alternating voltage;
a rectifier circuit that rectifies the second AC voltage and converts it to a DC voltage; and short-circuit current suppressing means connected to an output terminal of the rectifier circuit;
a current sensor connected to the short-circuit current suppressing means;
a determination circuit for determining whether or not the detection output of the current sensor exceeds a predetermined threshold;
A control circuit that controls the output from the output terminal to stop or decrease the output from the output terminal when the determination circuit determines that the detection output from the current sensor exceeds a predetermined threshold. and
a switching circuit connected in series with the current sensor;
prepared,
The control circuit stops the output from the output terminal by switching the switching circuit to a non-conducting state when the determination circuit determines that the detection output of the current sensor exceeds a predetermined threshold. to control
A DC power supply circuit characterized by: The control circuit stops the output of the inverter circuit or reduces the output of the inverter circuit when the determination circuit determines that the detection output of the current sensor exceeds a predetermined threshold value, 2. The DC power supply circuit according to claim 1, wherein control is performed such that the output from the output terminal is stopped or the output from the output terminal is reduced. 3. The DC power supply circuit according to claim 1 , wherein said short-circuit current suppressing means is an inductor, a resistive element, or a combination of an inductor and a resistive element. 4. The DC power supply circuit according to claim 1, wherein said rectifier circuit is a Cockcroft-Walton circuit or a voltage doubler rectifier circuit. A DC power supply circuit that outputs a DC voltage from an output terminal,
an inverter circuit that converts a DC input voltage into a first AC voltage;
a transformer that converts the first alternating voltage to a second alternating voltage;
a rectifier circuit that rectifies the second AC voltage and converts it to a DC voltage;
short-circuit current suppression means connected to the output terminal of the rectifier circuit;
a current sensor connected to the short-circuit current suppressing means;
a determination circuit for determining whether or not the detection output of the current sensor exceeds a predetermined threshold;
A control circuit that controls the output from the output terminal to stop or decrease the output from the output terminal when the determination circuit determines that the detection output from the current sensor exceeds a predetermined threshold. and
with
The short-circuit current suppressing means is an inductor, a resistive element, or a combination of an inductor and a resistive element,
The DC power supply circuit, wherein the inductor includes a core with an air gap or has an air core structure.

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