JPH067520B2 - X-ray high voltage device - Google Patents

Description

Detailed Description of the Invention [Industrial applications]

The present invention relates to an X-ray high voltage device, and more particularly to an improvement of a tube voltage output control system in an inverter type X-ray high voltage device.

[Prior art]

Inverter type X-ray high-voltage equipment rectifies and smoothes an AC power source and then switches at high speed to create AC, which is boosted by a transformer and rectified and smoothed again to obtain high-voltage DC. Is supplied to the X-ray tube. The control of the tube voltage to be supplied is conventionally performed by measuring the tube voltage,
The feedback control is performed by comparing the measured value with the set value and changing the switching frequency so that the error between them is minimized. However, by simply measuring the tube voltage and feeding it back to the switching frequency, the frequency becomes too high because the difference between the measured value and the set value of the tube voltage is large when the tube voltage is zero when the power is turned on. There is an inconvenience that overshoot occurs at the rise of the tube voltage. Therefore, conventionally, the reference value to be compared with the measured value is set not to be the set value at first, but to gradually approach the set value, thereby avoiding the overshoot at the rising edge. .

[Problems to be Solved by the Invention]

However, in the case of the conventional configuration in which the reference value is gradually increased, there is a problem that the rise of the tube voltage cannot be accelerated. According to the present invention, the rise of the tube voltage can be accelerated.
An object is to provide a line high voltage device.

[Means for Solving the Problems]

To achieve the above object, in an X-ray high voltage apparatus according to the present invention, a first rectifying means for converting an AC output from an AC power supply into a DC output, and this DC output is switched to convert into an AC output of a predetermined frequency. Switching means, means for boosting the voltage of this alternating current output, second rectifying means for converting the boosted alternating current output to direct current output and outputting it as tube voltage, means for detecting the tube voltage, and tube voltage And a means for setting the tube current, and a first storage means which is addressed by the set tube voltage and the set tube current and stores a steady-state value corresponding to the set voltage and the set tube current. And second storage means which is addressed by the set tube voltage and set tube current, and stores a rising value according to the set tube voltage and set tube current, and the detected tube voltage and setting. The comparing means for comparing the set tube voltage and the set tube current with each other when the comparing means determines that the detection tube voltage has not reached the set tube voltage at the rising time. The switching means controls to switch at a frequency corresponding to the value at the time of rising, which is called according to the above, and is set from the first storage means from the time when it is determined that the detection tube voltage has reached the set tube voltage. A control means for determining a reference switching frequency of the switching means corresponding to the steady-state value called according to the tube voltage and the set tube current, and switching the feedback control of the detection tube voltage to the switching frequency. It is characterized by being equipped.

[Work]

By comparing the detected tube voltage and the value of the set tube voltage,
At the time of rising, it is judged whether the detection tube voltage has reached the set tube voltage. When it is determined that the detection tube voltage has not reached the set tube voltage, the corresponding values at the rising time corresponding to the set tube voltage and the set tube current are called from the second storage means, and a predetermined value determined by this value is determined. The switching means is controlled to switch at a frequency. Then, when it is determined that the detection tube voltage has reached the set tube voltage, the steady-state values corresponding to the set tube voltage and the set tube current corresponding to the set tube voltage and the set tube current are called, and this value is used. A reference switching frequency is set and feedback control of the detection tube voltage to the switching frequency is performed. Therefore, before the tube voltage reaches the set tube voltage at the rising time, switching is performed at a certain fixed frequency.
The frequency can correspond to each combination of the set tube voltage and the set tube current such that the rising speed becomes faster. This is because the rising value is stored in the second storage means in accordance with the set tube voltage and the set tube current. As a result, by appropriately selecting the rising value that determines the frequency for each combination of the set tube voltage and set tube current, the rise time can be kept constant regardless of the tube voltage / tube current setting. You can also do it. After the detection tube voltage reaches the set tube voltage, feedback control is performed to feed back the detection tube voltage to the switching frequency. At that time, the reference switching frequency is a frequency determined by the steady-state value read from the first storage means in accordance with the set tube voltage and the set tube current. That is, the feedback control of the detection tube voltage to the switching frequency is performed with reference to the switching frequency according to the set tube voltage and the set tube current, and it is appropriate that the set tube voltage and the set tube current are actually obtained. Become.

【Example】

Next, an embodiment of the present invention will be described with reference to the drawings. In FIG. 1, AC power from an AC power supply 1 is rectified by a rectifier 2, smoothed by a smoothing capacitor 3, and converted into a DC output. Then, this DC output is switched by the switch elements 4a to 4d (the switch elements 4a and 4d and the switch elements 4b and 4c are alternately turned on,
It is converted to an AC output (turned off) and sent to the primary side of the high-voltage transformer 7 via the resonance capacitor 5 and the resonance inductance 6. A high-voltage AC output appears on the secondary side of the high-voltage transformer 7, which is rectified by the rectifier 8 and the smoothing capacitor 1
It is smoothed at 0, converted into high-voltage DC, and applied to the X-ray tube 11. The switching operation of the switch elements 4a to 4d is controlled by the inverter control device 12. That is, X
The high DC voltage applied to the wire tube 11 is detected by the high voltage detecting resistors 9a to 9d and the adder 13, and this is fed back to the switching frequency via the inverter control device 12. Here, description will be given with reference to the timing chart of FIG. First of all, the shooting conditions such as shooting time, tube current,
The tube voltage is the shooting time setting device 22 and the tube current setting device 2 respectively.
3, set by the tube voltage setting device 24. Then, according to the set tube current value and the set tube voltage value, the memories 20, 21 are set.
To Vs and Vn are read. Next, when an X-ray exposure button (not shown) is pressed, as shown in FIG. 2A, an X-ray exposure signal that is High for the time set by the imaging time setting device 22 is sent to the V / F converter 18. Given. As a result, the V / F converter 1
8 starts oscillating at the frequency corresponding to the input voltage Vin (see FIGS. 2B and 2C). The output Fo of the V / F converter 18 is sent to the drive circuit 19, and the drive circuit 19 drives the switching elements 4a to 4d for switching at a frequency according to the output Fo. Then, the current I1 as shown in FIG. 2D begins to flow in the primary side of the high voltage transformer 7, and the tube voltage gradually rises as shown in FIG. 2E. In the process of the rise of the tube voltage, the tube voltage obtained from the adder 13 is lower than the set tube voltage sent from the tube voltage setting unit 24, so the output of the comparator 14 becomes Low. Therefore, the switch S1 is turned on, the integrator 16 including the OP amplifier, the resistor R1, and the capacitor C1 is turned off, and the Q output of the latch circuit 25 is also kept low. Latch circuit 25
The switch S2 is off and the switch S3 is on when the Q output of is kept low. At this time, the output Δ of the integrator 16
V is zero and the other input of the adder 17 is the memory 20
It is Vs read from. Therefore, adder 1
7 output, that is, the input voltage Vin of the V / F converter 18
Becomes a constant value corresponding to Vs (see FIG. 2B),
The output Fo of the V / F converter 18 becomes a pulse having a constant frequency (see FIG. 2C) corresponding to the Vs, and the switching of the switch elements 4a to 4d is repeated at the constant frequency. When the tube voltage reaches the set value, the output of the comparator 14 becomes High.
h. Then, the switch S1 is turned off, the Q output of the latch circuit 25 becomes High, the switch S2 is turned on, and the switch S3 is turned off. for that reason,
One input of the adder 17 is switched from Vs to Vn, and the other input is supplied with the output ΔV of the integrator 16 which has started its operation when the switch S1 is turned off. This Vn and ΔV are added by the adder 17 to obtain V
It becomes the input Vin of the / F converter 18. The output ΔV of the integrator 16 is obtained by integrating the output of the error amplifier 15, that is, the error between the tube voltage from the adder 13 and the set tube voltage value from the tube voltage setter 24, and the tube voltage becomes the set value. Immediately after reaching, the difference between the two is zero, so the output of the error amplifier 15 is also zero, and the output of the integrator 16 is also zero, so Vin becomes Vn (see FIG. 2B). Therefore, as long as the power supply voltage is constant, switching should be performed at the frequency determined by the value of Vn, and the tube voltage should be kept at the set value. However, in reality, since the power supply voltage drops due to the impedance of the power supply circuit and the wiring, the tube voltage tends to decrease, and an error occurs between it and the set value. As a result, the output ΔV of the integrator 16 gradually increases,
This ΔV is added to Vn by the adder 17, the switching frequency is increased, and the tube voltage is increased. When the tube voltage reaches the set value, the output of the error amplifier 15 becomes zero and the input of the integrator 16 becomes zero, so that the integration operation is stopped. In this way, feedback control is performed so that the tube voltage becomes equal to the set value. That is, Vn defines a switching frequency that serves as a reference, and the switching frequency is changed with this frequency as a reference by feedback control. Values of Vs and Vn are stored in advance in the memories 20 and 21 according to the tube voltage and the tube current as shown in FIGS. The value of Vn is a value corresponding to the switching frequency required to obtain the set tube voltage / tube current, and is uniquely determined by the combination of the tube voltage and the tube current. FIG. 3B shows V depending on the combination of the tube voltage and the tube current.
An example of the value of n is shown. On the other hand, the value of Vs is set to be larger than the above Vn as shown in FIG. 3A. This is because if the value of Vs that determines the switching frequency is made the same as Vn when the set value has not yet been reached during the rise process of the tube voltage, not only the rise until the set value is reached but also the set load is reached. This is because the time until the tube voltage reaches the set value varies depending on the conditions (tube voltage, tube current). For example, when the tube voltage is set to the same value and the tube voltage is changed, the rising waveform of the tube voltage becomes as shown in FIG. 4A. Therefore, the switching frequency at the rise of the tube voltage is not set to Vn, but is set to Vs shown in FIG. As a result, the lower the tube current becomes, the higher the frequency becomes, and the faster the rise can be made until the tube voltage reaches the set value at the time of rise, and the time until the tube voltage reaches the set value can be obtained even under different load conditions. Can be almost the same.
In other words, the value of Vs is obtained in advance and stored in the memory 20 as a value such that the time required to reach the set value of the tube voltage is the same under each load condition. These Vn and Vs data are obtained by measuring data at several points using the tube current or tube voltage as a parameter in an actual device, and other data by interpolation or the like. It should be noted that, in addition to the configuration in which the data obtained in advance is stored in the two memories 20 and 21 and is read out with the set values of the tube voltage and the tube current as described above, only the measurement data of several points and the calculation program are stored. Then, when the tube voltage and the tube current are set, a microcomputer is used to calculate Vn and Vs corresponding to the set values of the tube voltage and the tube current from an arithmetic program from several points of data. It can also be taken.

【The invention's effect】

According to the X-ray high-voltage device of the present invention, since the switching frequency at the time of rising can be determined according to the load condition (the set tube voltage and the set tube current), the tube voltage is set as an appropriate switching frequency for each load condition. It is possible to speed up the rise and make the rise time of the tube voltage the same regardless of the load conditions. Further, from this, the accuracy of the exposure time can be improved. Furthermore, in a steady state, the detected tube voltage is fed back to the switching frequency to control the tube voltage. At this time, the reference switching frequency is set as load conditions (set tube voltage and set tube current).
Therefore, appropriate feedback control can be performed to actually obtain the set tube voltage and the set tube current.

[Brief description of drawings]

FIG. 1 is a block diagram of an embodiment of the present invention, FIG. 2 is a timing chart for explaining the operation of FIG. 1, FIGS. 3A and 3B are diagrams showing memory storage examples, and FIG. 4A. ，
B is a waveform diagram showing the rise of the tube voltage. DESCRIPTION OF SYMBOLS 1 ... AC power supply, 2, 8 ... Rectifier, 3, 10 ... Smoothing capacitor, 4a-4d ... Switch element, 5 ... Resonance capacitor, 6 ... Resonance inductance, 7 ... High voltage transformer, 9a ...
9d ... Resistance for high voltage detection, 11 ... X-ray tube, 12 ... Inverter control device, 13, 17 ... Adder, 14 ... Comparator, 15
... error amplifier, 16 ... integrator, 18 ... V / F converter, 19 ... drive circuit, 20, 21 ... memory, 22 ... shooting time setting device, 23 ... tube current setting device, 24 ... tube voltage setting device, 25 ... Latch circuit.

Claims (1)

[Claims] 1. A first rectifying means for converting an AC output from an AC power supply into a DC output, a switching means for switching the DC output to convert it into an AC output having a predetermined frequency, and boosting the voltage of the AC output. Means, second rectifying means for converting the boosted AC output to DC output and outputting as a tube voltage, means for detecting the tube voltage, means for setting the tube voltage, and means for setting the tube current. And a first storage means which is addressed by the set tube voltage and the set tube current, and stores a steady-state value corresponding to the set voltage and the set tube current, and an address by the set tube voltage and the set tube current. The second storage means for storing the rising value corresponding to the set voltage and the set tube current, the comparing means for comparing the detected tube voltage with the set tube voltage, and the comparing means. Further, when it is determined that the detection tube voltage does not reach the set tube voltage at the rising time, the frequency corresponding to the value at the rising time called according to the set tube voltage and the set tube current from the second storage means is used. From the time when it is determined that the detection tube voltage has reached the set tube voltage by controlling the switching means to perform switching, and in the steady state which is called from the first storage means according to the set tube voltage and the set tube current. An X-ray high voltage apparatus comprising: a control unit that determines a reference switching frequency of the switching unit in accordance with the value and switches the feedback control of the detection tube voltage to the switching frequency.