JPS5934080Y2 - X-ray tube filament heating circuit - Google Patents

Description

[Detailed description of the invention] This invention relates to a filament heating circuit for an X-ray tube with dual focal points.
This is an attempt to eliminate the obstacles to miniaturization of line high voltage generators.

Generally, in both photography and fluoroscopy, it is better to have a small focal point; however, when performing short-term photography, a large focal point is often used because the instantaneous human effort is large.

Therefore, a bifocal X-ray tube having both a small focus filament and a large focus filament is usually used in an X-ray fluoroscopic imaging apparatus.

However, in a conventional bifocal X-ray tube, a number of heating transformers corresponding to each filament are provided, and which filament is to be heated is selected on the primary side of the transformer.

Since this heating transformer requires high insulation, its installation volume is large, which is an obstacle to downsizing the X-ray high voltage generator.

This idea solves the above problems, and the heating transformer 1
Two filaments can be heated on the stand simply by operating a changeover switch, without using a high-insulation switch.

The drawings will be explained below.

1 and 2 are control rectifiers, 3 and 4 are heating rectifiers, 5 is a large focus current limiting resistor short circuit switch (hereinafter referred to as the large focus switch), and 6 is a small focus current limiting resistor short circuit switch (hereinafter referred to as the small focus switch). ), 7 is a large focus current limiting resistor, 8 is a small focus current limiting resistor, 9 is a filament heating transformer, 10 is a bifocal X-ray tube, 11 is an AC power supply,
12 is a DC power supply, 13.14 is a control transistor, 1
5 is a current limiting resistor, 16 is a changeover switch, 17 and 18 are heating transformers, 19 is a small focus filament, and 20 is a large focus filament.

FIG. 1 is a circuit diagram of an X-ray tube filament heating circuit according to a first embodiment, in which heating rectifiers 3 and 4 are connected in series to each filament of a bifocal X-ray tube 10, and these heating rectifiers 3 and 4 are connected to the secondary side of the filament heating transformer 9 so that the rectifying directions are opposite to each other, and on the primary side of the heating transformer 9, antiparallel control rectifiers 1 and 2 are connected. A parallel circuit of a large focus current limiting resistor 7 and a large focus switch 5 connected in series to the control rectifier 1, and a small focus current limiting resistor 8 connected in series to the control rectifier 2.
A control circuit consisting of a parallel circuit of the small focal point switch 6 and the small focus switch 6 is connected to an AC power source 11.

FIG. 3 is a circuit diagram of the second embodiment, in which large focus and small focus current limiting resistors 7 and 8 and a large focus and small focus switch 5 are provided on the primary winding side of the filament heating transformer 9. and 6, and the control transistors 13 and 1 connected in series to this parallel circuit.
4 and the primary winding of the heating transformer 9 connected in antiparallel with respect to transistors, and a DC power supply 12 that commonly supplies power to each of the control circuits.

Note that an oscillation circuit that alternately turns on and off the transistors 13 and 14 is omitted.

FIG. 4 is a circuit diagram of a third embodiment, in which a filament heating transformer 9 is provided with a tertiary winding, a current limiting resistor 15 is connected in series with this tertiary winding, and a current limiting resistor 15 is connected in series with this resistor 15. , and a control circuit consisting of control rectifiers 1 and 2 connected in antiparallel to each other and a changeover switch 16 is connected to the tertiary winding.

The primary winding of the filament heating transformer 9 is connected to the AC power supply 11.
It is connected to the.

The effects of this device will be explained when heating the filament of an X-ray tube.

FIG. 1 shows the circuit state when heating the small focus filament. In this case, the small focus switch 6 is opened at the bottom,
Current limiting resistor 8 is short-circuited.

Figure 2 shows the power supply voltage waveform and filament heating current waveform in the circuit state of Figure 1, where a is the power supply voltage waveform, b is the current waveform supplied to the small focus filament, and C is the current waveform supplied to the small focus filament.
is the current waveform supplied to the large focus filament.

In FIG. 1, from the AC power supply 11 to the small focus switch 6,
A positive half-wave as shown in FIG. 2 is applied to the filament heating transformer 9 through the control rectifier 2, and a half-wave of the same polarity as shown in FIG. The focusing filament 19 is heated.

The next negative half wave is a large focus current limiting resistor 7, a control rectifier 1
In the circuit of the filament heating transformer 9, the negative half wave shown in FIG.
Flows through 0.

Therefore, by appropriately selecting the resistance value of the large focus current limiting resistor 7, the large focus filament 20 can be prevented from being heated.

When heating the large focus filament 20, the large focus and small focus switches 5 and 6 may be simultaneously switched in the opposite direction to that shown in FIG.

Considering that the circuit of FIG. 3 is the case where the AC power supply 11 in the circuit of FIG. 1 is replaced with a DC power supply 12, and the control rectifiers 1 and 2 are replaced with control transistors 13 and 14,
The functions can be understood in the same manner as in FIG.

In this case, since it is possible to arbitrarily adjust the ON-OFF period of the transistors 13 and 14, the first
The filament can be heated more efficiently than the embodiment shown in the figure.

In addition, in FIGS. 1 and 3, the switches 5 and 6 are interlocked with each other in a phase-shifting manner so that the filaments 19 and 20 can be selectively heated.

In FIG. 4, to explain the effect of the control circuit provided in the tertiary winding of the heating transformer 9, the positive half wave passes through the heating rectifier 3 and flows to the small focus filament 19. 4 and does not flow to the large focus filament 20.

When a positive half-wave is applied to the tertiary winding, current is allowed to pass through the control rectifier 1 but is blocked in the control rectifier 2.

When the full changeover switch 16 is switched to the control rectifier 2 side as shown in the figure, no current flows to the tertiary winding during the positive half wave, so the small focus filament 19 has the waveform shown in Figure 2. A large current flows through it, heating it up.

During the next negative half wave, current flows through the control rectifier 2 to the tertiary winding, and as a result, a portion of the current in the secondary winding flows, so the waveform shown in FIG. 2C is reduced by the current control resistor 15. current flows through the large focus filament 20.

Therefore, by appropriately selecting the resistance value of the current limiting resistor 15, the large focus filament 20 can be hardly heated.

Further, when heating the large focus filament 20, the switch 16 may be switched to the control rectifier 1 side.

With this invention, there is no need to use two heating transformers for each filament, and there is no need to use a highly insulated switch, and it is possible to arbitrarily switch and heat any one of the two filaments.

Furthermore, since the number of components in the high voltage section is small and the components such as a rectifier are small, the device can be made smaller and lighter.

Further, if the configuration is as shown in the embodiment shown in FIG. 4, electric power having the same positive and negative waveforms is supplied to the transformer, so that there is an advantage that biased magnetization does not occur.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing an embodiment of the present invention, FIG. 2 is a waveform diagram for explaining the operation of FIG. 1, and FIGS. 3 and 4 are circuit diagrams showing other embodiments of the present invention. Explanation of symbols, 1: Control rectifier, 2: Control rectifier, 3
: Rectifier for heating, 4: Rectifier for heating, ゛9: Filament heating transformer, 13 and 14: Control transistor, 1
9: small focus filament, 20: large focus filament.

Claims (2)

[Scope of utility model registration request] (1) In a circuit that selectively heats two filaments of a bifocal X-ray tube, a single filament heating transformer is provided, and the two filaments are connected to the secondary winding of this transformer. are connected in parallel to each other via rectifiers with opposite polarities, and a control circuit is provided on the primary side of the transformer that can limit the AC power supplied to it into positive and negative polarities. An X-ray tube filament heating circuit characterized in that the filaments are selectively heated with electricity. (2) In the control circuit, rectifiers each having a current limiting resistor are connected in antiparallel between the primary wire of the transformer and the AC power source, and each of the current limiting resistors is short-circuited and interlocks in antiphase with each other. 2. The X-ray tube filament heating circuit according to claim 1, characterized in that the X-ray tube filament heating circuit has a switch.