JP7459778B2 - Power Conversion Equipment - Google Patents

Description

The present invention relates to a circuit technology that simulates nonlinear output by combining fixed resistance and variable resistance.

Some emitters (electron sources) utilize field electron emission, and examples of applications include cold cathode X-ray tubes. Figure 8 shows the IV characteristics (output characteristics) of the cold cathode X-ray tube.

Further, FIG. 1 shows a typical configuration diagram of a cold cathode X-ray generator that applies a desired high voltage to a cold cathode X-ray tube that is a load. As a prior art of this configuration, Patent Document 1 is disclosed.

JP 2019-57364 A

The emitter's I-V characteristics are nonlinear, and ingenuity is required to improve controllability. If you try to control the output current by manually operating a potentiometer or other device inside the cold cathode X-ray generator, you end up adjusting the nonlinear output with a linear element, making it difficult to achieve a uniform amount of change across the entire range.

Specifically, as shown in Figure 8, the higher the voltage applied to the cold cathode X-ray tube, the greater the change in output current relative to the amount of operation of a potentiometer, etc. Controllability can be improved by creating a program, but this is costly.

From the above, it is possible to adjust the output with a uniform amount of current change over the entire section for loads with nonlinear IV characteristics, and it also simplifies the design and reduces costs. The challenge is to provide a power conversion device that is

The present invention has been devised in view of the above-mentioned conventional problems, and one aspect thereof includes a capacitor bank, a DC voltage variable circuit connected to the capacitor bank, and a converter converting DC power of the capacitor bank into AC power. A power conversion device comprising: an inverter to perform conversion; and a load having nonlinear IV characteristics, which is connected to the AC side of the inverter or connected to the AC side of the inverter via another device. The DC voltage variable circuit includes: a fourth resistor having a resistance value variable adjustment function; a second resistor, one end of which is connected to one end of the fourth resistor, and the second resistor is connected in series with the fourth resistor; a third resistor, one end of which is connected to the other end of the fourth resistor, the other end of which is connected to the other end of the second resistor, and the third resistor is connected in parallel to a series circuit of the second resistor and the fourth resistor; a first resistor, one end of which is connected to a series-parallel circuit of a second resistor, the third resistor, and the fourth resistor; the other end of the first resistor is connected to the positive electrode of a DC power supply; A connection point between a series-parallel circuit of a resistor, the third resistor, and the fourth resistor and the first resistor is connected to one end of the capacitor bank as an output voltage command, and the other end of the second resistor and the third resistor are connected to each other as an output voltage command. The other end of the resistor and the other end of the capacitor bank are connected to the negative electrode of the DC power supply, and the output voltage of the variable DC voltage circuit is adjusted by adjusting the resistance value of the fourth resistor. Features.

Further, as another aspect, a capacitor bank, a DC voltage generation circuit connected to the capacitor bank, an inverter that converts DC power of the capacitor bank into AC power, and an output voltage of the DC voltage generation circuit or the inverter. an output voltage control circuit that controls the output voltage of the inverter; and a load that is connected to the AC side of the inverter or connected to the AC side of the inverter via another device and has nonlinear IV characteristics. The output voltage control circuit includes a fourth resistor having a resistance value variable adjustment function, a second resistor connected in series to the fourth resistor, and the second resistor and the fourth resistor. a third resistor connected in parallel to a series circuit of four resistors; a first resistor having one end connected to a series-parallel circuit of the second resistor, the third resistor, and the fourth resistor; The other end of the resistor is connected to the power supply voltage, the connection point between the series-parallel circuit of the second resistor, the third resistor, and the fourth resistor and the first resistor is set as an output voltage command, and the resistance of the fourth resistor is The output voltage command is adjusted by adjusting a value, and the output voltage of the DC voltage generation circuit or the output voltage of the inverter is controlled based on the adjusted output voltage command.

Moreover, as one aspect thereof, the third resistor is characterized in that it has a resistance value variable adjustment function.

The present invention makes it possible to provide a power conversion device that can adjust the output with a uniform current change amount over the entire range for a load with a nonlinear I-V characteristic, while also achieving simplified design and low cost.

FIG. 1 is an overall configuration diagram of a cold cathode X-ray generator. 1 is a circuit configuration diagram showing a DC voltage variable circuit of Embodiment 1. FIG. The figure which shows the relationship between 4th resistance R4 and output voltage command Vref. FIG. 13 is a graph showing R4-V characteristics when the first resistor R1 is adjusted. FIG. 13 is a graph showing the R4-V characteristics when the second resistor R2 is adjusted. FIG. 13 is a graph showing the R4-V characteristics when the third resistor R3 is adjusted. FIG. 3 is a circuit configuration diagram showing a DC voltage variable circuit according to a second embodiment. FIG. 3 is a diagram showing IV characteristics (output characteristics) of a cold cathode X-ray tube.

Embodiments 1 to 3 of the power converter according to the present invention will be described in detail below based on FIGS. 1 to 7.

[Embodiment 1]
Figure 1 shows an overview of the cold cathode X-ray generator (power converter). The cold cathode X-ray generator includes a capacitor bank 1, an inverter (for example, a high frequency inverter) 2, a step-up transformer 3, a Cockcroft circuit 4, a cold cathode X-ray tube 5, and voltage dividing resistors R5 and R6. Be prepared.

Although not shown in FIG. 1, a DC voltage variable circuit is connected to the left side of the capacitor bank 1 and is connected to one end (positive pole) and the other end (negative pole) of the capacitor bank 1.

Inverter 2 converts the DC power of capacitor bank 1 into AC power. Step-up transformer 3 steps up the AC output of inverter 2 . The Cockcroft circuit 4 generates a DC voltage from the AC voltage output from the step-up transformer 3 and outputs it to the cold cathode X-ray tube 5 . Further, a series circuit of voltage dividing resistors R5 and R6 is connected in parallel to the capacitor bank 1. The connection point between the voltage dividing resistors R5 and R6 becomes the detection voltage Vc.

By adjusting the voltage charged to the capacitor bank 1, the output voltage of the Cockcroft circuit 4 can be changed, thereby adjusting the output of the cold cathode X-ray tube 5. The charging voltage of the capacitor bank 1 and the output voltage of the Cockcroft circuit 4 are determined by the turns ratio of the step-up transformer 3 and the number of stages of the Cockcroft circuit 4, and are in a proportional relationship.

FIG. 2 shows the configuration of the variable DC voltage circuit according to the first embodiment. FIG. 2 shows a circuit that generates the output voltage command Vref of the variable DC voltage circuit. Other examples of variable DC voltage circuits include choppers, PWM converters, and thyristor rectifiers.

As shown in FIG. 2, the first to fourth resistors R1 to R4 are connected in series and parallel to the terminal VCC. One end of the second resistor R2 is connected to one end of the fourth resistor, and the second resistor R2 is connected in series to the fourth resistor R4. One end of the third resistor R3 is connected to the other end of the fourth resistor R4, and the other end of the third resistor R3 is connected to the other end of the second resistor R2, and the third resistor R3 is connected in parallel to the series circuit of the second resistor R2 and the fourth resistor R4. One end of the first resistor R1 is connected to the series-parallel circuit of the second resistor R2, the third resistor R3, and the fourth resistor R4. The terminal VCC is also connected to the positive pole of an external DC power supply (not shown).

The other end of the first resistor R1 is connected to the terminal VCC. The connection point between the first resistor R1 and the series-parallel circuit of the second resistor R2, the third resistor R3, and the fourth resistor R4 is connected to one end of the capacitor bank 1 as the output voltage command Vref. In addition, the other end (negative pole) of the capacitor bank 1, the other end of the second resistor R2, and the other end of the third resistor R3 are connected to the negative pole of an external DC power source (not shown).

In the first embodiment, the first to third resistors R1 to R3 are fixed resistors, and the fourth resistor R4 has a resistance value variable adjustment function. The fourth resistor R4 is preferably a digital potentiometer, but an analog variable resistor is also applicable. In the first embodiment, by configuring the DC voltage variable circuit as shown in FIG. 2, when the fourth resistor R4 is manually operated using a potentiometer or the like, the I-V characteristics of the cold cathode X-ray tube are completely affected. It is possible to adjust the output with a uniform amount of current change in the section.

The I-V characteristic of the cold cathode X-ray tube 5 is nonlinear, as shown in Figure 8. Therefore, if the charging voltage of the capacitor bank 1 is changed linearly, the amount of change in current increases as the voltage increases, resulting in poor controllability.

When the circuit is configured as in the first embodiment and the potentiometer or the like (fourth resistor R4) is operated, a divided voltage (output voltage command) Vref as shown in FIG. 3 can be obtained. This divided voltage (output voltage command) Vref changes non-linearly with respect to the resistance value of the fourth resistor R4, as shown in FIG.

Since the AC output of the inverter 2 outputs an AC voltage proportional to the divided voltage (output voltage command) Vref, it is possible to adjust the current of the cold cathode X-ray tube 5 with a uniform current variation over the entire section. The voltage dividing resistance (output voltage command) Vref is expressed by the following equation (1).

By adjusting the first resistor R1, the R4-V characteristic can be adjusted as shown in FIG. 4, so it is possible to shift the IV characteristic.

Also, by adjusting the second resistor R2, the R4-V characteristic can be adjusted as shown in Figure 5, making it possible to select the emission start point of the I-V characteristic. Furthermore, by adjusting the third resistor R3, the R4-V characteristic can be adjusted as shown in Figure 6, making it possible to select the slope of the I-V characteristic.

The IV characteristic of the emitter is nonlinear, and when adjusted with a potentiometer or the like, the amount of current change varies depending on the section. By adopting the configuration as in the first embodiment, it is possible to adjust the output with a uniform amount of current change over the entire section. Furthermore, it is possible to simplify the design and reduce costs.

In the first embodiment, a nonlinear output can be simulated by changing the linear variable resistor. Also, by changing each resistor, it is possible to cover a wide range of I-V characteristics.

[Embodiment 2]
7 shows a DC voltage variable circuit according to the second embodiment. The DC voltage variable circuit has the same circuit configuration as that of the first embodiment, but the third resistor R3 has a resistance value variably adjusting function. The third resistor R3 is, for example, an analog variable resistor or a digital potentiometer.

By adopting a configuration like that of the second embodiment, it is possible to accommodate the life characteristics of the cold cathode X-ray tube 5.

It is known that emitters have a lifespan characteristic, and that the output current gradually decreases with respect to the applied voltage. Therefore, by feeding back the output voltage and current of the Cockcroft circuit 4 and comparing them with the set values, and controlling the digital potentiometer of the third resistor R3 (i.e. the resistance value of the third resistor R3), it is possible to grasp the lifespan characteristic. This allows the output value to be compared with the set value for operation.

If an analog variable resistor is used for the third resistor R3, if the life characteristics change during periodic inspection, the resistance value of the third resistor R3 can be manually changed to eliminate the discrepancy between the set value and the output value.

According to the second embodiment, similarly to the first embodiment, the output can be adjusted with a uniform amount of current change over the entire section.

Furthermore, in the second embodiment, the operation can be performed taking into consideration the life characteristics, so that an accurate output can always be obtained.
[Embodiment 3]
In the first and second embodiments, the divided voltage (output voltage command) Vref generated by the circuits in Fig. 2 and Fig. 7 is used as the output voltage of the DC voltage variable circuit . The DC voltage variable circuit of this configuration may be replaced with a DC voltage generating device such as a chopper, a PWM converter, or a thyristor rectifier, and the divided voltage (output voltage command) Vref generated by the circuits (output voltage control circuits) in Fig. 2 and Fig. 7 may be used as the output voltage command of the DC voltage generating device. In this case, the divided voltage (output voltage command) Vref and the detection voltage Vc obtained by dividing the capacitor bank voltage are compared and controlled, and the output voltage of the DC voltage generating device is controlled by the on/off operation of a switching element in the DC voltage generating device.

Furthermore, by replacing the DC voltage generation device with a device that generates a constant DC voltage (DC voltage generation device) such as a diode rectifier, the output voltage command Vref generated by the circuits (output voltage control circuit) in FIGS. 2 and 7 The configuration may be such that the output voltage command of the inverter 2 is set as the output voltage command of the inverter 2. In this case, the output voltage of the inverter 2 is controlled by the on/off operation of the switching elements within the inverter 2.

Furthermore, the load of the present invention is not limited to a cold cathode X-ray tube. The invention can be applied to any load that has a nonlinear I-V characteristic as shown in Figure 8.

Furthermore, this technology can be applied to devices that do not have the step-up transformer 3 or Cockcroft circuit 4 shown in FIG. 1. That is, a load with a nonlinear I-V characteristic (e.g., a cold cathode X-ray tube 5) is connected to the AC side of the inverter 2, or to the AC side of the inverter 2 via another device (e.g., the step-up transformer 3 or the Cockcroft circuit 4).

Although the present invention has been described in detail above only with respect to the specific examples, it will be clear to those skilled in the art that various modifications and alterations are possible within the scope of the technical concept of the present invention, and it goes without saying that such modifications and alterations fall within the scope of the claims.

1... Capacitor bank 2... Inverter 3... Step-up transformer 4... Cockcroft circuit 5... Cold cathode X-ray tube R1... First resistor R2... Second resistor R3... Third resistor R4... Fourth resistor R5, R6... Voltage dividing resistors Vref... Output voltage command (voltage dividing voltage)
VCC: Power supply voltage Vc: Detection voltage

Claims (3)

capacitor bank,
a DC voltage variable circuit connected to the capacitor bank;
an inverter that converts the DC power of the capacitor bank into AC power;
A power conversion device comprising: a load connected to the alternating current side of the inverter, or connected to the alternating current side of the inverter via another device, and having nonlinear IV characteristics,
The DC voltage variable circuit is
a fourth resistor having a resistance value variable adjustment function;
a second resistor having one end connected to one end of the fourth resistor and connected in series with the fourth resistor;
a third resistor, one end of which is connected to the other end of the fourth resistor, the other end of which is connected to the other end of the second resistor, and the third resistor is connected in parallel to a series circuit of the second resistor and the fourth resistor;
a first resistor whose one end is connected to a series-parallel circuit of the second resistor, the third resistor, and the fourth resistor;
The other end of the first resistor is connected to the positive electrode of a DC power supply, and the connection point between the series-parallel circuit of the second resistor, the third resistor, and the fourth resistor and the first resistor is an output voltage . connected to one end of the capacitor bank;
The other end of the second resistor, the other end of the third resistor, and the other end of the capacitor bank are connected to the negative electrode of the DC power supply,
A power conversion device characterized in that the output voltage of the variable DC voltage circuit is adjusted by adjusting the resistance value of the fourth resistor. capacitor bank,
a DC voltage generator connected to the capacitor bank;
an inverter that converts the DC power of the capacitor bank into AC power;
an output voltage control circuit that controls the output voltage of the DC voltage generation device or the output voltage of the inverter;
A power conversion device comprising: a load connected to the alternating current side of the inverter, or connected to the alternating current side of the inverter via another device, and having nonlinear IV characteristics,
The output voltage control circuit includes:
a fourth resistor having a resistance value variable adjustment function;
a second resistor having one end connected to one end of the fourth resistor and connected in series with the fourth resistor;
a third resistor, one end of which is connected to the other end of the fourth resistor, the other end of which is connected to the other end of the second resistor, and the third resistor is connected in parallel to a series circuit of the second resistor and the fourth resistor;
a first resistor whose one end is connected to a series-parallel circuit of the second resistor, the third resistor, and the fourth resistor;
The other end of the first resistor is connected to the positive electrode of a DC power supply , and the connection point between the series-parallel circuit of the second resistor, the third resistor, and the fourth resistor and the first resistor is set as an output voltage command. year,
The other end of the second resistor and the other end of the third resistor are connected to the negative electrode of the DC power supply,
The output voltage command is adjusted by adjusting the resistance value of the fourth resistor, and the output voltage of the DC voltage generation device or the output voltage of the inverter is controlled based on the adjusted output voltage command. power converter. The power conversion device according to claim 1 or 2, characterized in that the third resistor has a variable resistance adjustment function.

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