JPH0451499A - X-ray high voltage device - Google Patents

Abstract

PURPOSE:To automatically adjust the switching frequency of an inverter circuit always to the optimum value thereof regardless of changes in the power of a load by monitoring the output voltage waveform of the inverter circuit to detect the optimum switching point thereof so as to generate a pulse signal relevant to the detected switching point, and then switching on the inverter circuit in synchronization with this pulse signal. CONSTITUTION:A resonance voltage waveform given during the switching action of an inverter circuit 3 is monitored at the output terminals T1, T2, thereof by a waveform detector circuit 10 which detects the optimum switching point of the inverter circuit to output a zero cross pulse. This zero cross pulse is outputted to a clock generator circuit 11 which generates a switching clock to be outputted to an oscillator circuit 9 in response to the input pulse. Whereby the oscillator circuit 9 switches on each of paired transistors Q1, Q2 in the inverter circuit 3 via a driver 8 in synchronization with the switching clock.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to an X-ray high-voltage device that is applied as a high-voltage power supply device for an X-ray CT device or the like.

(Prior art) In medical equipment such as X-ray CT equipment and
A high voltage power supply is required to generate the line, and a switching DC stabilized power supply is generally used as this power supply. This switching type power supply is a commercial AC power supply (100V).

50H2 or 60H2), this DC input is switched by a switching element such as a transistor to convert it into high frequency AC (15KH2 to 20KH,), and then rectified to obtain a high voltage, resulting in a stable output voltage. It has the advantage of being easy to obtain. In other words, this switching type power supply constitutes a so-called inverter circuit, and the switching operation of this inverter circuit intermittents the time during which direct current is transmitted from input to output, and is controlled in such a way that the desired output is obtained. .

Figure 5 shows the conventional configuration of an X-ray high voltage device using such an inverter circuit, in which 1 is an AC input power source;
2 is a rectifier circuit, 3 is an inverter circuit that switches DC input and converts it into high-frequency AC, and 4 is a high-voltage transformer that boosts the high-frequency AC.

5 is a rectifier circuit that rectifies the boosted alternating current. 6 is a load such as an X-ray tube, to which the high voltage output from the rectifier circuit 5 is applied.

The inverter circuit 3 includes a pair of transistors Q.

It is a push-pull type with Q2, and is composed of a voltage resonant circuit. Q, , Q2 are driven by a driver 8 based on a switching signal generated by an oscillation circuit 9 to perform a switching operation.

In this case, the frequency of the switching signal that controls the transistors Q, . . . Q2 is fixed at a value that provides the most efficient switching operation.

Typically, this switching frequency is adjusted for maximum efficiency when the maximum load is connected. Note that the inverter circuit 3 and the driver 8 are insulated via an isolation transformer 7, thereby separating the high-voltage inverter circuit 3 side from the low-voltage driver 8 side.

That is, while the inverter circuit 3 side operates with a relatively high voltage, the driver 8 side operates with a relatively low voltage, so mutual interference between the two is prevented. C is a capacitor.

(Problems to be Solved by the Invention) However, in the conventional X-ray high voltage apparatus, the resonant frequency of the resonant circuit changes depending on the load, so there is a problem in that the deviation of the switching frequency of the resonant frequency changes. Therefore, switching distortion increases due to electromagnetic noise and the like. In this case, even if adjustment is attempted to suppress the influence, it is impossible to adjust to the optimum frequency with a fixed switching frequency.

The present invention has been made in response to the above-mentioned problems.
It is an object of the present invention to provide an X-ray high voltage device in which the switching frequency is always automatically adjusted to an optimum value regardless of load fluctuations.

[Structure of the Invention] (Means for Solving the Problems) In order to achieve the above objects, the present invention provides (1) an X-ray high voltage that converts DC input into AC by switching it with an inverter circuit, and then rectifies it to obtain a high voltage; The apparatus includes means for monitoring an output voltage waveform of an inverter circuit, detecting an optimal switching point, and generating a pulse signal corresponding to the optimum switching point, and a driving means for switching the inverter circuit in synchronization with the pulse signal. It is characterized by this.

(Function) By monitoring the output voltage waveform of the inverter circuit, the optimum switching point is always detected from this output waveform and a pulse signal such as a zero-cross pulse is generated in accordance with this point.

Subsequently, the oscillation circuit is controlled in synchronization with this pulse signal to drive the inverter circuit. As a result, the optimum switching timing can always be obtained, so that the switching frequency can be automatically adjusted to the optimum value that allows the most efficient switching operation to be performed regardless of load fluctuations.

(Example) The present invention will be described in detail below with reference to the drawings.

FIG. 1 shows a first embodiment of the X-ray high-voltage apparatus of the present invention, in which reference numeral 1 denotes an AC input power source consisting of a commercial power source, and a rectifier circuit that rectifies and outputs this AC input.

3 is an inverter circuit consisting of a pair of push-pull transistors Ql and Q2 that switches DC input, converts it to high-frequency AC, and outputs it; 4 is a high-voltage transformer that boosts the high-frequency AC; 5 rectifies the boosted AC and outputs it. 6 is a load consisting of an X-ray tube to which a rectified high voltage is applied. Further, 7 is an isolation transformer, 8 is a driver, and 9 is an oscillation circuit, which are the same as the conventional configuration.

10 is a waveform detection circuit and the output terminal T1 of the inverter circuit 3
．． This monitors the resonant voltage waveform obtained from T2. The waveform detection circuit 10 detects a waveform as shown in FIG. 3(a), and based on this, the waveform detection circuit 10
generates a zero-cross pulse as shown in FIG. 3(b).

That is, the waveform detection circuit 10 has each output terminal T1. T
Each time the resonant voltage waveform of FIG. 3(a) detected from 2 crosses the zero level, a zero-cross pulse whose output level changes positive or negative is generated. That is, the optimum switching point is detected and a zero-crossing pulse is generated as a pulse signal corresponding to the optimum switching point. 11. is a clock generation circuit that is controlled according to the rising or falling edge of the zero-cross pulse to generate a switching clock that controls the oscillation circuit 9. This clock generation circuit 11. A switching clock as shown in FIG. 3(C) is generated by 1. compared to the zero-cross pulse. ．． The switching clock is configured to be able to generate the switching clock with a timing shift of 12. VR is a volume for adjusting timing tI+j2. Timing 1. ．． Although it is desirable that 12 be small from the purpose of the present invention, it is desirable that it be somewhat large in consideration of improvement in output characteristics, which is contrary to improvement in switching efficiency. The oscillation circuit 9 is controlled in synchronization with a switching clock, and is connected to a pair of transistors Q, , Q, of the inverter circuit 3 via a driver 8.

The switching operation is performed.

Next, the operation of this embodiment will be explained.

The resonant voltage waveform during switching operation of the inverter circuit 3 is generated at its output terminal T1. At T2, it is monitored by the waveform detection circuit 10, and the waveform detection circuit 10 detects the optimum switching point and outputs a zero-crossing pulse as shown in FIG. 3(b).

This zero-cross pulse is output to the clock generation circuit 11, and the clock generation circuit 11 responds to the clock generation circuit 11 as shown in FIG. 3(C).
A switching clock is generated and output to the oscillation circuit 9. As a result, the oscillation circuit 9 switches the pair of transistors Q, Q2 of the inverter circuit 3 via the driver 8 in synchronization with the switching clock.

According to this embodiment, the switching clock that controls the oscillation circuit 9 is always generated in response to the zero-cross pulse generated by detecting the optimal switching point, so that the optimal switching timing is determined by the oscillation circuit 9.
This is fed back to the inverter circuit 3 and the inverter circuit 3 is switched. This allows the switching operation of the inverter circuit 3 to be controlled by always obtaining the optimum switching timing, so the switching frequency is automatically set to the optimum value that allows the most efficient switching operation regardless of load fluctuations. Can be adjusted. That is, it becomes possible to always operate the inverter circuit 3 with maximum efficiency. Therefore, an increase in electromagnetic noise, etc. is prevented, and switching distortion is reduced. Furthermore, since the switching frequency is automatically adjusted to the optimum value, complicated adjustment work is no longer necessary, and the burden on the operator can be reduced.

FIG. 2 shows a second embodiment of the present invention, in which a pair of transistors Q, , Q2 forming an inverter circuit 3 is shown.
A first waveform detection circuit 10a and a second waveform detection circuit 10b monitor the voltage waveforms output between each output terminal E+C1 and from E2-C2. These first and second waveform detection circuits 10a,
10b detects a waveform as shown in FIG. 4(a), and based on this, these waveform detection circuits 10a and 10b generate detection pulses as shown in FIG. 4(b).

This detection pulse is output to the clock generation circuit 11, and the clock generation circuit 11 responds to the clock generation circuit 11 as shown in FIG. 4(C).
A switching clock is generated and output to the oscillation circuit 9. C is a capacitor.

In the second embodiment as well, the first and second waveform detection circuits 10a and 10b detect the optimum switching point and generate detection pulses accordingly, so that the optimum switch timing is determined by the oscillation circuit. 9 will be fed back. Therefore, as in the first embodiment, the inverter circuit 3 is controlled to always perform the most efficient switching operation regardless of load fluctuations, so that the same effects as in the first embodiment can be obtained. can.

In each embodiment, by adjusting the generation timing of the switching clock by the clock generation circuit, it is possible to improve the output to the load at the cost of slightly reducing the efficiency of the switching operation as necessary.

According to the present invention, high voltage can be stably provided to medical devices that particularly require a high voltage power supply, such as X-ray CT devices and X-ray diagnostic devices, and other similar devices can be provided as necessary. It is also possible to apply it to

[Effects of the Invention] As described above, according to the present invention, the optimal switching timing is detected by monitoring the output waveform of the inverter circuit, so that the inverter circuit can always switch efficiently regardless of load fluctuations. Its switching frequency can be automatically adjusted to

[Brief explanation of drawings]

FIG. 1 is a block diagram showing a first embodiment of the X-ray high voltage apparatus of the present invention, FIG. 2 is a block diagram showing a second embodiment of the present invention, and FIGS. 3(a) to (C) 4(a) to 4(a) are waveform time charts explaining the operation of the first embodiment.
C) is a waveform time chart explaining the operation of the second embodiment, and FIG. 5 is a block diagram showing a conventional device. 3... Inverter circuit, 6... X-ray tube (load), 8
...Driver, 9...Oscillation circuit, 10.10a, 1
．． Ob... Waveform detection circuit, 1-1... Clock generation circuit, Ql, Q2... Transistor.

Claims (2)

[Claims] (1) In an X-ray high-voltage device that converts DC input into AC using an inverter circuit and then rectifies it to obtain a high voltage, the output voltage waveform of the inverter circuit is monitored to detect the optimal switching point and respond accordingly. 1. An X-ray high voltage apparatus comprising: means for generating a pulse signal; and driving means for switching the inverter circuit in synchronization with the pulse signal. (2) The X-ray high voltage device according to claim 1, wherein the inverter circuit is comprised of push-pull switching elements.