JPS58121600A - High voltage power supply for x-ray equipment - Google Patents

Abstract

PURPOSE:To reduce to the utmost the difference between output voltage in time of no-load and that in time of load in a high-tension transformer, by making up this power unit to control the bias voltage of a high-tension switching element so as to cause the impressed voltage of an X-ray tube to be turned into the specified tube voltage. CONSTITUTION:When a switching circuit 2 is turned on, a three-phase AC power supply 3phiAC is fed to a high-tension transformer 3 via both a tube voltage adjusting transformer 1 and the switching circuit 2 and, after the pressure is raised up, full-wave rectification is carried out with a high-tension rectifier 4 whereby the rectified power is fed to a high-tension condenser 5. Accordingly, the high- tension condenser 5 starts charging but the charge voltage is divided in part, which is detected by charge-voltage detecting resistors R2 and R3 and inputted into a comparator 11 in consequence. On the other hand, as this comparator 11 is provided with the output of an adding signal made by an adder 10 summing each signal corresponding to those of setting tetrode share voltage and setting tube voltage, the comparator 11 turns off the switching circuit 2 when series- capacitor-charging voltage arrives at the sum voltage of these setting tetrode share voltage and the tube voltage.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a high-voltage power supply device for an X-ray apparatus that can completely reduce the dielectric strength of multi-voltage side circuit elements such as a high-voltage transformer, a high-voltage rectifier, a high-voltage capacitor, and a high-voltage switching element.

As shown in FIG. 1, a conventional high voltage power supply device for an X-ray apparatus is a 6-phase AC power supply 3ψAC that is controlled to control voltage etc. via a blue voltage adjustment transformer 1 and a switching circuit 2, and then The voltage is boosted by a transformer and full-wave rectified by a high-voltage rectifier 4 to charge a high-voltage capacitor 5, and the charging voltage is passed through a high-voltage switching element such as a high-voltage vacuum tube 6 such as a tetrode vacuum tube or a pentode vacuum tube. This is the force that is applied to the X-ray tube 7. In this case, the high-voltage vacuum tube 6 fully switches the voltage applied to the X-ray tube 7 (tube voltage) by controlling its electrode voltage, fully controls the voltage drop by controlling the internal resistance, and fully stabilizes the tube voltage. , which reduces pulsation. In addition, the switching circuit 2 includes a 6-phase AC power supply 3J
By switching on the primary side (low voltage side) of the high voltage transformer filter that boosts the ACffi, the entire secondary side (high voltage side) is switched, and the charging start and end of the high voltage capacitor 5 is controlled. During this period, a sequence is established such as the start of charging of the high voltage capacitor 5 → the end of charging → the high voltage vacuum tube 6 is turned on, and the charging voltage of the high voltage capacitor 5 is applied to the X-ray tube 7.

However, in such a conventional device, the switching circuit 2 is turned on before the high voltage vacuum tube 6 is turned on and high voltage is applied to the X-ray tube 7, and the output voltage of the tube voltage adjustment transformer 1 is changed to the high voltage transformer. Since the high voltage capacitor 5 is charged in the trench after the switching circuit 2 is turned on and charging is completed and the high voltage vacuum tube 6 is turned on, there is no load on the secondary side of the high voltage transformer B. Under load (high pressure vacuum tube 6
A significantly higher voltage is output than when the switch is on.

This difference in output voltage is generally particularly large in a power supply device that includes both the tube voltage adjustment transformer 1 and the high-voltage transformer 3, and a voltage several tens of kilovolts higher is output when there is no load than when there is a load.

This point will now be explained in more detail with reference to FIG. Figure 2 is a graph showing changes in the output voltage of the high-voltage capacitor 5 (secondary voltage of the high-voltage transformer 3) with respect to the primary voltage of the high-voltage transformer 6, where line A is at no load and line a is at load. Show characteristics. In this figure, if we look at the output voltage when the primary voltage is aV, we can see that when the load is on (in the case of a line), the output voltage is AV.
However, when there is no load (in the case of line A), A′■(A′〉A
), and it can be seen that even if the primary voltage is the same, the output voltage increases considerably when there is no load compared to when there is a load. As mentioned above, after charging the high voltage capacitor 5 in advance, the high voltage vacuum tube 6 is charged in accordance with the shooting timer signal.
In the case of a power supply device that switches the The no-load state is unavoidable during this period.

Therefore, it is possible to adjust the primary voltage between no-load and load conditions, but since the tube voltage adjustment transformer 1 is usually made of a slider, this adjusts the primary voltage. This involves a mechanical delay in operation, and it is impossible to follow the electronic switching of high-voltage vacuum tubes. 1, the tube voltage adjustment transformer 1 is a tap switching system, 1
Another option is to insert a resistor (not shown) on the next side, and when there is no load, a portion of the primary voltage is shared by the voltage drop caused by the resistor, and when X-ray radiation (load) occurs, the resistor is short-circuited. However, since the tap position or the shared voltage of the resistor differs depending on the load current, and the switching circuit for the tap and resistor becomes complicated, these methods are often used to make the output voltage the same between no-load and load conditions. It was impossible to do so.

Therefore, the solution was to set the withstand voltage of the high-voltage side circuit elements such as the high-voltage transformer 6, high-voltage rectifier 4, high-voltage capacitor 5, and high-voltage vacuum tube 6 according to the output voltage at no-load. The high-voltage side circuit element is required to have a dielectric strength far greater than the rated voltage of the device, making the device large and expensive.

In addition, on the secondary side of the high-voltage transformer filter, it is possible to fully control the voltage (tube voltage) applied to the X-ray tube 7 by adjusting the internal resistance of the high-voltage vacuum tube B. In the method in which Part B is made to share part or all of the output voltage, the shared voltage will be consumed as thermal energy within the high-voltage vacuum tube 6.

On the other hand, in order to make the total pulsation of the tube voltage waveform small and flat, that is, to reduce the difference in output voltage between no load and load, the differential voltage must be shared by high voltage vacuum tube A. The larger the value, the greater the energy consumed by the high-pressure vacuum tube 6.

However, there is a limit to the energy stored in the high-voltage vacuum tube O, and if this limit is exceeded, there is a risk of serious accidents such as damage to the high-pressure vacuum tube O. In order to make full use of the performance of B, the voltage difference had to be made as small as possible.

The present invention was made in view of the above-mentioned circumstances, and is designed to calculate the difference between the output voltage of a high-voltage transformer at no-load (the no-load charging voltage of the high-voltage capacitor) and the output voltage at load (tube voltage). It is an object of the present invention to provide an entire high voltage power supply device for an X-ray apparatus that can be made as small as possible and can reduce the dielectric strength of high voltage side circuit elements.

The present invention will be described in detail below with reference to FIGS. 6 and 4.

FIG. 6 is a block diagram showing an embodiment of the high voltage power supply device for an X-ray apparatus according to the present invention, and 1.3 to 7 in the figure are the same as in FIG. 1, respectively. Further, 2 also represents a switching circuit as in FIG. 1, but in the device of the present invention, this switching circuit 2 is configured to be capable of switching control by a switching control circuit to be described later.

R+ and R4 are bleeder resistors, R2 and R3 are resistors for detecting the charging voltage of the high voltage capacitor 5, and these resistors R1, R2 and R3+ R4 are connected in series to form a voltage divider, and are connected in parallel to each high voltage capacitor 5. ing.

In addition, R5 and R8 are bleeder resistors, R6 and R7 are tube voltage detection resistors, and these resistors Rs, R6 and R7
, R8 are connected in series so that there is no voltage division benefit, and these voltage dividers are also connected in series. And its resistance R
The end on the 5 side is connected to the cathode of one high-pressure vacuum tube B connected to the anode of the X-ray tube 7, and the end on the resistor R8 side is connected to the anode of the other high-pressure vacuum tube 6 connected to the cathode (filament) of the X-ray tube 70. and the resistors R6 and R
The connection point with 7 is grounded. In addition, in this example,
A tetrode is used as the high-pressure vacuum tube 6.

8 is the tetrode sharing voltage setting signal source, no load □
Between time and load time, high voltage capacitor 5 at load time
Assuming a slight voltage difference that occurs due to voltage pulsations in the This signal is called the tetrode sharing voltage setting signal)
Full output. Note that this differential voltage can be reduced by increasing the capacity of the high-voltage capacitor 5 to reduce the pulsation component, and it is better to minimize the tetrode sharing voltage due to this differential voltage to reduce the amount consumed by the tetrode. energy(
This is similar to the case of the difference voltage between the output voltages generated between the no-load state and the loaded state by turning on all of the switching circuits 2 before turning on the tetrodrome. Ru.

Reference numeral 9 indicates a predetermined tube voltage; here, a tube voltage setting signal source that outputs a voltage signal corresponding to the rated tube voltage (this signal is referred to as a brass tube voltage setting signal); 10 indicates the tetrode shared voltage setting signal, the tube voltage setting signal, and the An adder 11 adds the sum of the voltage signals (voltage divider output signals) proportional to the charging voltage of each high-voltage capacitor 5 detected by the charging voltage detection resistors R2 and R3, the addition signal of the adder 10, and the total sum. These are a comparator that compares and outputs a signal if they match, and a timer that sets the 12-digit X-ray irradiation time.

15 is a switching control circuit which turns on the switching circuit 2 when there is a timer signal from the timer 12 and there is no matching signal from the comparator 11, turning on the entire primary side of the high voltage transformer 3; When the timer signal from the comparator 11 disappears, or when there is a match signal from the comparator 11, the switching circuit 2 is turned off to completely turn off the primary side of the high voltage transformer 3, thereby changing the charging voltage of each high voltage capacitor 5. The total voltage (hereinafter referred to as series capacitor charging voltage) is always constant regardless of whether the tetrometer is on or off.
That is, the voltage is maintained at the set tube voltage plus the tetrode shared voltage.

14 is a comparator that compares the tube voltage signal proportional to the tube voltage applied to the X-ray tube detected by the tube voltage detection resistors R6 and R7 with the tube voltage setting signal; 15 is a comparator of the comparator 14; This is a bias control circuit that fully operates each bias circuit 16 in accordance with the output signal and controls the internal voltage drop of each tetrode so that the tube voltage signal and the tube voltage setting signal are the same.

Next, the operation of the above-mentioned device of the present invention will be explained.

First, when the switching circuit 2 is turned on by a control signal from the switching control circuit 15, the filter phase 9 is supplied with a power supply of 3ψA.
C is supplied to the high-voltage transformer B through the tube voltage adjustment transformer 1 and the switching circuit 2, and after being boosted, is full-wave rectified by the high-voltage rectifier 4 and supplied to the high-voltage capacitor 5. Therefore, the high voltage capacitor 5 starts to be fully charged, but the charging voltage is divided, detected by the charging voltage detection resistors R2 and R3, and input to the comparator 11. On the other hand, this comparator 11 is inputted with an addition signal obtained by adding each signal in the full adder 10 according to the set tetrode sharing voltage and the set tube voltage. The signal is compared with the signal proportional to the series capacitor charging voltage, and when the two match, that is, the series capacitor charging voltage becomes the sum voltage of the set tetrode sharing voltage and tube voltage (hereinafter referred to as set voltage). When the threshold is reached, the switching circuit 2 is completely turned off. Therefore, the primary side of the high voltage transformer 3 is turned off, and the high voltage capacitor 5 stops charging.

At this time, the series capacitor charging voltage has reached the set voltage, but in this state, the high voltage capacitor 5
Since the battery is discharged by the resistors R1, R2 and R3, R4, the charging voltage gradually drops. However, when the charging voltage drops below the set voltage, the comparison circuit 11r (
Then, the switching circuit 2 is turned on again, charging the high-voltage capacitor 5 and increasing its voltage to the set voltage. Therefore, the series capacitor charging voltage is always maintained at the set voltage until the tetrometer is turned on and applied to the X-ray tube 7.

On the other hand, when the tetrometer is turned on and tube voltage is applied to the X-ray tube 7, the voltage is divided and the tube voltage detection resistor R6
, R7 and input to the comparator 14. On the other hand, the comparator 14 is inputted with a tube voltage setting signal, and the comparator 14 compares the tube voltage setting signal with the tube voltage signal and sends the difference signal to the bias control circuit 15. Output. The bias control circuit 15 operates each bias circuit 16 according to the difference signal and controls the internal voltage drop of each tetrode so that the tube voltage setting signal and the tube voltage signal become the same, As a result, a tube voltage with small pulsations and a flat waveform is applied to the X-ray tube 7.

Note that FIG. 4 is a block diagram showing a specific example of a circuit that drives the switching control circuit 13 in FIG.
7 is an oscillator, 18 is a high voltage capacitor charging start signal source, 1
9 is a NAND circuit, and 20 is an inverter. In addition, in FIG. 4, the same parts as in FIG. 6 are all designated by the same reference numerals. That is, the switching control circuit 13
The output signal of the oscillator 17 and the charging start signal source 1
It operates by inputting the output signal of the NAND circuit 19, which receives the signal from the inverter 8, through the inverter 20.

For example, if the power is turned on from hibernation mode,
At this point, the comparator 11 is not outputting a coincidence signal (assuming that a positive signal is being output at this time), while the oscillator 17 is always outputting a pulse, here a positive pulse. Therefore, even though the charge start signal source 18 outputs a positive charge start signal, the NAND circuit 19 outputs a negative signal. This signal is converted into a positive signal via the inverter 20, and the switching control circuit 13
This drives the switching control circuit 13 to turn on all of the switching circuits 2, thereby starting to fully charge the high voltage capacitor 5 shown in FIG.

Note that since the subsequent operations are the same as those described above, the explanation thereof will be omitted here.

FIG. 5 is a circuit diagram showing a specific example of the switching circuit 2 in FIG. 6. In this example, the high-voltage transformer 5 has negative windings connected in large numbers, and its neutral point can be completely separated, and the switching circuit 2 is configured as a switch circuit that short-circuits and opens the neutral point. ing. That is, the current at the neutral point is subjected to six-phase full-wave rectification by the rectifiers Dl to D6. When the charging start signal from the switching control circuit 15 is input to the SCR gate GA, 5CRA becomes conductive, the neutral point is shorted, high voltage is output to the secondary winding of the high voltage transformer B, and charging starts completely. do. Next, when a charge stop signal is input to the gate GB of 5CRB, 5CRB becomes conductive and 5CRA'(r) is extinguished due to the vibration of the capacitor C and reactor L, and the neutral point is opened, thereby charging is to stop.

FIG. 6 is a diagram showing a specific example in which all tetrodes are used for the high-pressure vacuum tube B in FIG. That is, in this example, the timer signal from the timer 12 is W-modulated in the AM modulator 15b by the output of the oscillator 15a, voltage amplified by the voltage amplification Amp 15c, and then sent to the gate transformer GT+'f! The signal is inputted to the bias circuit 16 via C. The modulated signal is demodulated and Tetro-Dro 'k
0N-OFF control game) Output to Gt and Tetro
Convert from OFF state to conductive state. The similarly modulated signal is simultaneously input to the tetrode bias circuits 16 on the anode side and cathode side of the X-ray tube 7, so both are in a conductive state at the same time.The charging voltage of the capacitor 5 is applied to the X-ray tube 7. be done.

Further, the signal from the tube voltage setting signal source 9 is compared with the output of the anode side voltage divider (R5, R6) by the comparator 14a, and an error signal is output. This error signal is AM-modulated by the AM modulator 15d by the output of the oscillator 15a, and the voltage amplification signal is
After voltage amplification by p15e, gate transformer G
It is input to the bias circuit 16 via T2k. The modulated signal is demodulated and output to G2, which controls the entire internal voltage drop of the tetrode.

On the other hand, the voltage divider (Ry, Rs) output on the cathode side is output from the comparator 14.
b. Since the polarities are different, the tube voltage setting signals are compared after having their signs inverted by a sign inverter 15c.

The error signal is sent to the AM modulator 15 as well as the output of the comparator 14a.
f, after being modulated and amplified by the voltage amplification Amp 15g, it is input to the bias circuit 16 via the gate transformer GT2k and output to the gate G2. In this case, comparator 14a.

The output of 14b is the voltage divider Rs, R6: When the outputs of R7 and R8 are higher than the tube voltage setting signal voltage, a negative error output is output, and when it is lower, a positive error output is output.

Thus, the G2 bias voltage decreases in level when the tube voltage is high, and increases in level when the tube voltage is low. By controlling the G2 bias voltage in this way, the internal voltage drop of the tetrode can be controlled (
goods) and can adjust the tube voltage. Therefore timer 1
Voltage divider Rs + Rs during timer signal output from 2:
R? , Rs, the tube voltage can always be adjusted to a constant voltage corresponding to the tube voltage setting signal, and a flat tube voltage waveform can be obtained.

As described above, the present invention combines the output signal of the first voltage divider connected in parallel with the high-voltage capacitor and the setting voltage, which is at least a predetermined tube voltage to be applied to the X-ray tube, and in the above-described embodiment, the tube voltage. and a set signal set according to the sum voltage of the voltage and the tetrode shared voltage, the output signal of the first voltage divider is made to match the set signal, and the charging voltage of the high voltage capacitor is maintained at the set voltage. In addition to switching the switching circuit as shown in FIG. The bias voltage of the high-voltage switching element is adjusted so that the output signal of the second voltage divider matches the tube voltage setting signal, and the voltage applied to the X-ray tube becomes the predetermined tube voltage. Since it is fully controlled, it is possible to minimize the difference between the output voltage of the high voltage transformer at no load (the charging voltage of the high voltage capacitor at no load) and the output voltage at load (tube voltage). The advantageous effect is that the dielectric strength of high-voltage side circuit elements such as transformers, high-voltage rectifiers, high-voltage capacitors, and high-voltage switching elements can be completely reduced.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of the conventional device, Fig. 2 is a graph showing all the changes in the output voltage of the high voltage capacitor with respect to the primary voltage of the high voltage transformer in the conventional device, and Fig. 6 is the X
A block diagram showing an example of a high voltage power supply device for line equipment,
4 is a block diagram showing a specific example of a circuit that drives the switching control circuit in FIG. 3, FIG. 5 is a circuit diagram showing all specific examples of the switching circuit in FIG. 6, and FIG. It is a diagram showing a specific example when all tetrodes are used in the high-pressure vacuum tube inside. 2... Switching circuit, 3... High voltage transformer, 4...
...High voltage rectifier, 5...High voltage capacitor, 6...High voltage vacuum tube (tetrode), 7...X-ray tube, 8...Tetrode sharing voltage setting signal source, 9...Tube voltage setting signal source , 10... Adder, 11.14... Comparator, 15
...Bias control circuit, 16...Bias circuit, 5
aAC...6-phase 'ZK power supply, R1-R4, R5-R8
...Resistance (voltage divider). Patent applicant Hitachi Medico Co., Ltd.

Claims (1)

[Claims] 1. AC power is supplied to a high-voltage transformer via a switching circuit, is boosted by the high-voltage transformer, and is then rectified to charge a high-voltage capacitor, increasing the charging voltage of the high-voltage capacitor to a high voltage. In a high-voltage power supply for an X-ray apparatus that applies voltage to an X-ray tube with all switching elements, a first voltage divider connected in parallel with the high-voltage capacitor, and an output signal of the first voltage divider and at least the A first comparator that compares a set signal set according to a set voltage equal to or higher than a predetermined tube voltage applied to the X-ray tube; and an output signal of this first comparator is inputted; a switching control circuit that switches all of the switching circuits so that the output signal of the voltage divider No. 1 all matches the setting signal and the charging voltage of the high voltage capacitor is maintained at the setting voltage; a second voltage divider connected in parallel with the X-ray tube, and an output signal of the second voltage divider and the X-ray tube;
A second comparator that compares the tube voltage setting signal set according to a predetermined tube voltage applied to the line tube, and the output signal of this second comparator is inputted, and the output signal of the second voltage divider is inputted. and a bias control circuit that controls the bias voltage of the high-voltage switching element so that the output signal matches the tube voltage setting signal and the voltage applied to the X-ray tube becomes the predetermined tube voltage. High voltage power supply for X-ray equipment. 2. The high voltage power supply device for an X-ray apparatus according to claim 1, wherein the high voltage switching element is a tetrode.