JP3862264B2 - Multi-stage voltage doubler rectifier - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to a multistage voltage doubler rectifier such as a Cockcroft-Walton circuit, and more particularly to a multistage voltage doubler rectifier suitable for a power source used in a dental X-ray apparatus.
[0002]
In general, output stabilization is required regardless of whether the power source is a low-voltage power supply or a high-voltage power supply. In particular, in an X-ray apparatus or the like, as shown in FIG. 3, an X-ray tube (not shown) connected to an output terminal 2 of a multistage voltage doubler rectifier circuit 1 such as a well-known Cockcroft-Walton circuit. ) Is detected by the high voltage dividing resistor R1 and the voltage detecting resistor R2, and the detected voltage is fed back to the primary power control device 3 such as an inverter circuit or a chopper circuit. The power control device 3 includes a main circuit unit 3A such as an inverter circuit or a chopper circuit, and a control unit 3B. The control unit 3B is represented by a control drive circuit 3a, an error amplifier 3b, and a reference power source 3c. Reference numeral 4 denotes a high voltage transformer. In this conventional circuit, since the high voltage output voltage is directly detected by the high voltage dividing resistor R1 and the voltage detection resistor R2, the output detection voltage is proportional to the high voltage output voltage, and therefore the reference power supply 3c. Is selected to be a fixed value according to the rated value of the output voltage, and eventually the power control device 3 operates so that the output detection voltage becomes the reference value.
[0003]
In the case of such a normal circuit, a high-voltage voltage detection circuit including the high-voltage dividing resistor R1 is necessary. When the power supply housing is at the ground potential, a distance that does not cause a problem in electrical insulation is maintained. Therefore, there is a problem that the casing of the DC high-voltage generator itself is enlarged and the cost is increased. As a conventional example for solving this problem, there is a DC high voltage generator described in the following publication. One specific example includes an input current measuring device that measures an input current, a voltage measuring device that detects a DC voltage at the nth stage of the Cockcroft-Walton circuit, and an arithmetic processing device. And the n-th stage DC voltage are processed by a predetermined calculation formula to calculate the output voltage. In this example, since the DC voltage at the nth stage of the Cockcroft Walton circuit is detected, there is an advantage that the voltage measurement is lower than the output voltage.
[Patent Document 1]
Japanese Patent Laid-Open No. 9-182437 ((0032) to (0037) of the specification, FIG. 2, FIG. 3, FIG. 5)
[0004]
[Problems to be solved by the invention]
However, in such a conventional device, the output voltage can be detected by detecting a voltage lower than the output voltage. However, if the input current is also detected and the detected voltage and the detected current are not calculated, the output voltage can be accurately detected. There was a problem that it was not possible to detect. Also, the calculation formula must be obtained, and the calculation formula varies depending on the conditions. Therefore, it may be difficult to obtain the correct calculation formula. In such a case, an accurate output voltage detection value cannot be obtained. There is no problem. When the input current changes drastically due to noise or the like, it may be kicked that an accurate output voltage detection signal cannot be obtained due to the influence.
Therefore, in the present invention, the reference voltage value for the output condition of the output voltage value and the output current value is obtained in advance and stored in the reference voltage applying means such as CPU, and the reference voltage value corresponding to the set output condition is set as the reference voltage. It is characterized in that it is automatically taken out from the applying means and compared with the output voltage detection signal.
[0005]
[Means and Actions for Solving the Problems]
The invention according to claim 1 includes a first capacitor column connected in series from the initial stage capacitor to the final stage capacitor, and a second capacitor column connected in series from the initial stage capacitor to the final stage capacitor. A plurality of rectifying diodes for sequentially connecting the capacitors of the first capacitor column and the second capacitor column, a main circuit unit for controlling load power, and a primary winding connected to the main circuit unit; , A transformer having a secondary winding connected between the first stage capacitor of the first capacitor column and the first stage capacitor of the second capacitor column, and voltage detection for detecting a voltage corresponding to a DC output voltage Means, a reference voltage applying means, and controlling a difference voltage between a detected voltage from the voltage detecting means and a reference voltage from the reference voltage applying means to control the main circuit unit. In the multistage voltage doubler rectifier having an error amplifier applied to the moving part, the voltage detecting means is connected between a capacitor in the middle of the first capacitor column before the final stage and a fixed voltage point. The reference voltage applying means sets a value corresponding to an output detection signal when a plurality of the DC high voltage output voltages are directly detected between an upper limit value and a lower limit value of the load power as a set output voltage of the load in advance. When the DC high voltage output voltage is detected, the stored reference value is taken out according to the set output condition and given to the error amplifier as a reference voltage. A multi-stage voltage doubler rectifier characterized by the above is provided.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment of a multistage voltage doubler rectifier according to the present invention will be described with reference to FIG. The same symbols as those shown in FIG. 3 indicate corresponding members. In this embodiment, a reference voltage is supplied to the error amplifier 3b from a CPU 3d functioning as a reference voltage applying means, which will be described in detail later, and a voltage dividing resistor R1 and a voltage detection resistor R2 are connected in series as an output voltage detection circuit. This is characterized in that this is connected between a connection point J1 between the first-stage capacitor C1 and the second-stage capacitor C2 on the smoothing column side and a fixed potential such as a ground potential. For example, when the output voltage is 80 kV and the multistage voltage doubler rectifier circuit 1 has four stages, the conventional example requires a resistor having a withstand voltage of approximately 80 kV. In this embodiment, the voltage dividing resistor R1 having a withstand voltage of 20 kV The voltage detection resistor R2 having the same low voltage as the conventional one may be provided. In the drawing, one voltage dividing resistor R1 is shown, but in actuality, the voltage dividing resistor R1 is composed of a plurality of resistors connected in series and must be arranged in consideration of the electrical insulation distance between them. Therefore, the occupied space becomes larger and the cost becomes higher. However, in this embodiment, the number of resistors and the occupied space are only ¼ even if they are simply compared. The capacitors C1 to C4 constitute a first capacitor column and perform a smoothing action.
[0009]
However, since the output voltage is detected at the connection point J1 between the first-stage capacitor C1 and the second-stage capacitor C2 on the smoothing column side, the voltage detection accuracy is lower than when the high-voltage output voltage itself is directly detected. To do. Therefore, in the present invention, the output condition is changed in advance and the high voltage output voltage itself is directly detected, and a preferred reference voltage at that time is obtained and input to the CPU as reference voltage data. This point will be specifically described. In the case of a dental X-ray power source or the like, since the load condition is in a limited range, the present invention can be easily applied.
[0010]
For example, first, assuming that the lower limit value of the load range is 50 kV, the output voltage is set to 50 kV, and the operation is performed in the output current range, first 2 mA. The output voltage of 50 kV is directly detected, the voltage detection signal is compared with the reference voltage, the operation is performed, the reference voltage Va1 that can be operated while the output voltage is maintained at the set 50 kV is obtained, and the reference voltage Va1 is supplied to the CPU. Input as reference voltage data. Next, the output voltage is set to 50 kV, the output current is set to 5 mA, the reference voltage Va2 that can be operated while the output voltage is maintained at 50 kV is obtained, and the reference voltage Va1 is input to the CPU as reference data. In this way, the output current is sequentially changed to the maximum current value in the load range to obtain a preferred reference voltage at that time and input to the CPU as reference voltage data. Furthermore, the output voltage is set to 60 kV, the operation is performed with the output current changed as described above, the reference voltages Vb1, Vb2,... Vbn that can be operated with the output voltage maintained at 60 kV are obtained, and the reference data is obtained from the CPU. Enter as. In this way, assuming that the upper limit value of the load range is 100 kV, the output voltage is increased to 100 kV and the above operation is repeated, and the preferred reference voltages Vm1, Vm2,. As reference voltage data.
[0011]
The reference values (Va1, Va2,... Van), (Vb1, Vb2,... Vbn),... (Vm1, Vm2,. Is entered as Alternatively, reference voltage data as shown in FIG. 2 in which such a reference value is graphed is input. For example, if the values of the output voltage and output current are set to 80 kV and 10 mA, respectively, depending on the imaging conditions during X-ray imaging, the set output conditions are sent to the CPU 3c. A corresponding reference value is taken out and given to the error amplifier 3b as a reference signal. In the case of FIG. 2, when the values of the output voltage and the output current are set to V3 and I4, respectively, 5.3V that is the intersection of V3 and I4 is taken out as a reference voltage and given to the error amplifier 3b as a reference signal. It is done. The error amplifier 3b compares the output voltage detection signal given to the inverting terminal with the reference signal given from the CPU 3c to the non-inverting terminal, and gives an error signal proportional to the difference to the control drive circuit 3a. The control drive circuit 3a is driven by applying a drive signal having a pulse width such that the output voltage detection signal becomes equal to the reference signal to a switching semiconductor element (not shown) of the main circuit unit 3A such as an inverter circuit or a chopper circuit. Note that the control and driving of the switching semiconductor element (not shown) of the main circuit unit 3A is the same as the conventional one, and the description thereof is omitted.
[0012]
In the above embodiment, the output voltage detection circuit is connected between the connection point J1 between the first-stage capacitor C1 and the second-stage capacitor C2 on the smoothing column side having the lowest voltage, and a fixed potential such as the ground potential. The connection point J2 between the second-stage capacitor C2 and the third-stage capacitor C3, or the connection point J3 between the third-stage capacitor C3 and the fourth-stage capacitor C4, and a fixed potential such as a ground potential, Even if it connects between these, it is good that a measurement voltage can be made lower than before. The setting range of the output voltage and the output current is not limited to the above-described range, and is arbitrary.
[0013]
【The invention's effect】
As described above, according to the present invention, the reference value corresponding to the output detection signal when the DC high voltage output voltage of the multistage voltage doubler rectifier circuit is directly detected is stored in the reference voltage applying means in advance, When detecting the DC high voltage output voltage in the middle of the voltage doubler rectifier circuit, the stored reference value is taken out as the reference signal according to the set output condition, so the voltage in the middle of the DC high voltage output voltage is Even if it is detected, the DC high-voltage output voltage can be stably maintained at the set value, the output voltage detection circuit can be made with a low withstand voltage, and the overall size and price of the device can be reduced. be able to.
[Brief description of the drawings]
FIG. 1 is a drawing for explaining an embodiment of the present invention.
FIG. 2 is a drawing for explaining another embodiment of the present invention.
FIG. 3 is a drawing for explaining an example of a conventional multi-stage voltage doubler rectifier circuit;
[Explanation of symbols]
1-multi-stage voltage doubler rectifier circuit 2-DC high voltage output terminal 3-power control device 3A-main circuit unit 3B-control unit 3a-control drive circuit 3b-error amplifier 3c-CPU (reference voltage applying means)

Claims (1)

A first capacitor column connected in series from the first capacitor to the last capacitor;
A second capacitor column connected in series from the first capacitor to the last capacitor;
A plurality of rectifying diodes for sequentially connecting capacitors of the first capacitor column and the second capacitor column;
A main circuit section for controlling load power;
A transformer having a primary winding connected to the main circuit section, and a secondary winding connected between the first stage capacitor of the first capacitor column and the first stage capacitor of the second capacitor column; ,
Voltage detecting means for detecting a voltage corresponding to the DC output voltage;
A reference voltage applying means;
An error amplifier that provides a difference voltage between a detection voltage from the voltage detection unit and a reference voltage from the reference voltage application unit to the control drive unit of the main circuit unit;
In the multistage voltage doubler rectifier with
The voltage detection means is connected between a capacitor on the way from the first stage to the last stage of the first capacitor column and a fixed voltage point,
The reference voltage applying means sets a value corresponding to an output detection signal when directly detecting a plurality of the DC high voltage output voltages between an upper limit value and a lower limit value of the load power in advance as a set output voltage and a set current of the load. Stored as a reference value determined by the value of
When detecting a DC high voltage output voltage, the stored reference value is taken out according to a set output condition and given to the error amplifier as a reference voltage.

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