JPH0454360B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a rotary anode drive device for an X-ray tube that switches between two types of power sources by zero-cross switching.

(Prior Art) An anode of a rotating type is known as an anode of an X-ray tube used in an X-ray diagnostic apparatus. There are three steps to drive this rotating anode: (1) startup, (2) constant speed rotation, and (3) braking.
Two control steps are required. Step (1) is performed to start the stopped anode, and (2)
Step (3) is performed to stably rotate the activated anode, and step (3) is performed to stop the rotation of the anode after a predetermined operation has been completed.

FIG. 6 shows the configuration of a rotary anode drive device for an X-ray tube (Japanese Patent Application No. 61-277100) proposed earlier by the present applicant. An SSR that has a zero cross switching function (a function that turns on when the load applied AC voltage is approximately zero) for two types of in-phase AC power supply voltages: 220V) and a low voltage power supply for constant speed rotation (e.g. 60V). (solid state relay)
is supplied to the drive unit 2 of the rotary anode ₁ of the X-ray tube XT by switching by the switching means 4 used as switches SW 1 and SW ₂ . Fig. 7 is a timing chart showing the control operation. When the rotation request signal is applied from the outside for the period t ₁ - _{t 3} , SW ₁ is turned on for the period T ₁ (t ₁ - _{t 2} ), and 220V is generated. Since the signal is supplied to the drive section 2 from between terminals C and M, startup control is performed. Next, when SW ₁ is turned off, SW ₂ is turned on for T ₃ (t ₂ - _{t 3} ), and 60V is supplied to the drive section 2 from between terminals C and M, so that constant speed rotation is controlled. continue
At the same time as SW ₂ turns off, SW ₁ repeats on-off for T ₂ (t ₃ - _{t 4} ), and a half-wave rectified output of 220V is supplied to the drive unit 2 from between terminals C and M, so that braking is possible. Control takes place.

In this way, at t ₂ , SW ₁ is turned off and at the same time
By turning on SW ₂ , the voltage supplied to the drive section 2 is smoothly switched from 220V to 60V as shown in FIG. 8 by zero-cross switching.
This makes it possible to avoid surges during voltage switching and prevent the generation of noise.

(Problems to be solved by the invention) However, in such a rotating anode drive device, two
If the switching timing of the two switches SW ₁ and SW ₂ comes close to zero cross, there is a problem that the two types of power supplies will be short-circuited. i.e. switch
If there are variations in the characteristics of the SSRs used as SW ₁ and SW ₂ , when the switching timing of switches SW ₁ and SW ₂ comes close to zero cross, one switch may turn on before the other switch does not turn off. There will be a period where the transformer's 220V and 60V power supplies will be shorted as shown in Figure 9.

Specifically, for example, when SW ₁ is at the off timing near the zero cross, there are cases where this SSR turns off normally, and cases where it does not turn off at this timing and turns off after half a cycle, while SW ₂ turns off at that timing. There are cases where this SSR turns on normally when it should be turned on, and cases where it does not turn on at this timing and turns on after half a cycle. Accordingly
A situation occurs where the SSRs of SW ₁ and SW ₂ turn on at the same time.

The present invention has been made in response to the above-mentioned circumstances, and it is an object of the present invention to provide a rotary anode drive device for an X-ray tube that prevents short circuits between two types of power sources.

[Structure of the Invention] (Means for Solving the Problems) In order to achieve the above object, the present invention provides a phase detection means for detecting the phases of two types of power supplies, and a phase detection means for detecting the phase of two types of power supplies, and a solubilization system using the output of the phase detection means. The present invention is characterized by comprising a switching control means for controlling the switching timing of the two-state relay.

(Function) For example, if the phases (voltage or current) of two types of power supplies with the same phase, 220V and 60V, are detected, and the switching timing of the two switches SW ₁ and SW ₂ that switch each power supply comes close to zero cross, The switching timing is controlled by the phase detection output so as to avoid the vicinity of zero crossing. This results in 220V
This prevents short-circuiting of both the and 60V power supplies.

(Embodiment) FIG. 1 is a block diagram showing an embodiment of the rotary anode drive device for an X-ray tube according to the present invention, in which 1 is the rotary anode of the X-ray tube XT, 2 is the drive section of the rotary anode 1, and 3 is, for example,
A power transformer generates 220V (high voltage) and 60V (low voltage), and 4 is switching means composed of SSRs as switches SW ₁ and SW ₂ .

Further, 5 is a phase detection circuit that detects the phases of two types of power supplies (220V and 60V), and 6 is a switch switching control circuit that controls the switching timing of SW ₁ and SW ₂ based on the output of this phase detection circuit 5. . The phase detection circuit 5 detects the phase of the voltage or current signal S of 220V and 60V as shown in FIG. A detection signal Sc of W is output. This detection signal Sc is output as a signal shifted by td from the zero crossing point. The switch changeover control circuit 6 is, for example, D- as shown in FIG.
It is composed of a latch circuit 7. A trigger signal S _D for controlling the switches SW ₁ and SW ₂ is input from the outside to the D terminal of the D-latch circuit 7, and a detection signal C _C from the phase detection circuit 5 is input to the C _K terminal. Therefore, the D-latch circuit 7 outputs the detection signal S _C as shown in FIG.
At the timing when is input, the trigger signal S _D is outputted from the Q terminal as S _Q , and a control signal based on this is applied to the switches SW ₁ and SW ₂ .

Next, the operation of this embodiment will be explained.

220V always generated from power transformer 3 or
The phase of the 60V power supply is detected by the phase detection circuit 5, and a detection signal S _C as shown in FIG. 3 is applied to the switch switching control circuit 6. This detection signal S _C is shifted by td from the zero-crossing point of the power supply (220V or 60V), so a detection signal that avoids the vicinity of zero-crossing is output. The detection signal S _C is input to the C _K terminal of the D-latch circuit 7 forming the switch switching control circuit 6 . As a result, the D-latch circuit 7 outputs the trigger signal S _D input to the D terminal as the S _Q signal as shown in FIG. 4 at the timing of the detection signal S _C. This output signal S _Q is output at the timing of the detection signal S _C obtained from the phase detection circuit 5, and as described above, this detection signal S _C is shifted by td from the zero cross point of the power supply signal S and output. As a result, the output signal S _Q is output at a timing that avoids the vicinity of zero cross. The switch switching control circuit 6 uses this signal S _Q as a control signal.
Controls the switching timing of SW ₁ and SW ₂ .

According to such control operation, the switches SW ₁ ,
Since the switching timing of SW ₂ is selected and controlled so as to avoid the vicinity of zero cross, the switching between the two power supplies can be smoothly switched from, for example, 220V to 60V as shown in FIG. This eliminates the period in which both power supplies are turned on at the same time, thereby preventing short circuits between the two power supplies.

The two types of power supplies detected by the phase detection circuit 5 may detect voltages or may detect power supplies.
When detecting current, for example, Japanese Patent Application Laid-Open No. 58-120170
It is possible to use a detection means that is a part of the interlock circuit that checks whether or not current is flowing through the X-ray tube as shown in the above publication.

Further, the phase detection circuit 5 can also be used during braking operation.

[Effects of the Invention] As is clear from the above description, according to the present invention, when the phase of the power supply approaches the zero cross, the switching timing of the switch is controlled so as to avoid the vicinity, thereby preventing short circuits of the power supply. I can do it.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the rotary anode drive device for an X-ray tube of the present invention, FIG. 2 is a block diagram showing the main parts of the device of this embodiment, and FIGS. 3 and 4 are this embodiment. 5 is a power supply waveform diagram switched according to this embodiment, FIG. 6 is a block diagram of the conventional example, FIG. 7 is a timing chart of the conventional example, and FIGS. 8 and 9. The figure is a power supply waveform diagram obtained in a conventional example. DESCRIPTION OF SYMBOLS 1... Rotating anode, 2... Drive unit, 3... Power transformer, 5... Phase detection circuit, 6... Switch switching control circuit, 7... D-latch circuit.

Claims (1)

[Claims] 1. Phase detection for detecting the phases of two types of power sources in a rotary anode drive device for an X-ray tube that switches two types of power sources with the same phase using a solid state relay having a zero-cross switching function. 1. A rotary anode drive device for an X-ray tube, comprising: a means for driving an X-ray tube; and a switching control means for controlling the switching timing of a solid state relay based on the output of the phase detection means. 2. The rotary anode drive device for an X-ray tube according to claim 1, wherein the switching control means controls the switching timing of the solid state relay so as to avoid the vicinity of zero cross.