JPS5990400A - Heating circuit for x-ray device - Google Patents

Abstract

PURPOSE:To obtain a heating circuit which provides a wide range of control and in which circuit loss is decreased through prevention of any generation and application of excessively large voltage by interdependently operating switching circuits in order to regulate excessively large voltage generated during the turning on or off of a switching element. CONSTITUTION:An error signal between the set value of heating voltage and the output signal of a voltage detector 9, obtained by comparing them before the difference is amplified through a voltage controller 10, is applied to a signal-generating circuit 12. The circuit 12, after receiving a signal (S1) applied from an oscillator 11 having a frequency higher than the frequency of commercial power supply, generates a signal (S2) having an amplitude corresponding to the magnitude of a signal applied from a controller 10, and applies the signal (S2) to a distribution circuit 13. The distribution circuit 13 generates a signal (S3) equal to the signal (S2) to turn on and off a transistor 4 through an amplifier 14. At the same time, it generates a signal (S4) for turning on a thyristor 5 or 6 when the transistor 4 is turned off, and applies the signal (S4) to the thyristor 5 or 6 through an amplifier 15. By thus interdependently turning on and off the transistor 4 and the thyristor 5 or 6, the wave form of voltage applied to a heating transformer 2 is varied within the voltage range of a power source transformer 8.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a filament heating circuit for an X-ray apparatus, and particularly to a filament heating circuit for an X-ray apparatus, and in particular, to increase the control response speed of tube current, improve accuracy, and
The present invention relates to a stabilized heating circuit for an X-ray device.

A heating circuit of a conventional X-ray apparatus is shown in FIG. In the figure, 1 is a commercial AC power supply, 2 is a heating transformer, 3a, 3b,
3c and 3d are diodes, and 4 is a transistor. In order to change the heating state of the filament, the operation of the transistor 4 is controlled to control the voltage applied to the heating transformer 2 to be ey1 as shown in FIG. Since the transistor 4 bears the difference voltage between the power supply voltage e and eTO, the control range is widened.

However, if eTe is made significantly smaller than that, the loss of the transistor 4 increases, which has the drawback of requiring a large-capacitance element. In addition, in order to reduce the total loss, the AC at source]
The drawback is that it is necessary to use a voltage regulating transformer to adjust the voltage according to the heating conditions of the filament to reduce the voltage borne by the transistor 4.

An object of the present invention is to provide a heating circuit that has a wide control range and reduces circuit loss. .

The main points of the present invention are to control the entire range of heating voltage through the operation of the switching circuit, and to reduce circuit loss.
The heating voltage is controlled by changing the on-duty by performing all on and off operations of the switching elements of the switching circuit. In order to control excessive voltage that occurs when the switching element turns on and off, a second switching circuit is provided,
By operating in a complementary manner, generation and application of excessive voltage was prevented.

An embodiment of the present invention will be described below with reference to FIG. In the figure, 5.6 is a thyristor, 7 is a capacitor, 8 is a power transformer, 9 is a voltage detector, 10 is a voltage controller, 11
is an oscillator, 12 is a signal forming circuit, 13 is a distribution circuit, 14
．． ．． 15 is an amplifier.

The operation shown in FIG. 3 will be explained.

Heating voltage setting value determined by heating conditions and voltage detector 9
The output signals of the two are compared, and both amplified error signals are applied to the signal forming circuit 12 via the voltage controller 10. 12 receives the signal S applied from the oscillator 11 with a frequency higher than the commercial frequency, and forms a signal S2e having a width corresponding to the magnitude of the signal applied from 10 and applies it to the distribution circuit 13.

13 forms a signal S3 equal to the signal S2 to turn on and off the transistor 4 via the amplifier 14, and also turns on the thyristor 5 or 61 when the transistor 4 is off.
A signal S4 for turning on is formed and applied to 5 or 6 via an amplifier 15.

When the transistor 4 and the thyristor 5 or 6 are turned on and off in a complementary manner, the voltage e7 applied to the heating transformer 2 is equal to the voltage e of the power transformer 8 and e, as shown in FIG. The waveform changes between . eT is changed by the on-period T6 of transistor 4. This is done by changing l and e.

It can be controlled arbitrarily from to et. All switching elements perform on and off operations, so loss is small and
eT to perform complementary operations.

An excessive voltage exceeding the value determined by e is not applied to the switching element.

In the explanation, the oscillator 11 is asynchronous with the commercial AC power supply, but it can also be synchronous.

Further, as shown in FIG. 5, the transistor 4 may be operated in synchronization with the AC power supply.

A variable resistor may be connected in series to a switching circuit in which the thyristors 5 and 6 are connected in parallel to control the lowest voltage serving as a reference for eT.

According to the present invention, it is possible to prevent the application of excessive voltages associated with switching operations, thereby reducing circuit loss and providing a heating circuit with a wide control range.

[Brief explanation of the drawing]

Fig. 1 is a conventional heating circuit diagram, Fig. 2 is an explanatory diagram of the operation of Fig. 1, Fig. 3 is a heating circuit diagram of the present invention, and Figs. 4 and 5 are explanatory diagrams of the circuit operation of Fig. 3. be. 3a to 3d...diode, 4...transistor,
5゜6...Thyristor, 8...Power transformer, 9...
- Voltage detector, 10... Voltage controller, 11... Oscillator, 12... Signal forming circuit, 13... Distribution circuit. Figure 3 Figure 4- Mouth Figure 5

Claims (1)

[Claims] 1. A heating circuit that heats a filament of an X-ray tube using an AC power source is provided with a voltage controller that changes the magnitude of the input voltage in at least two stages, and the potential of the voltage controller is a first switch circuit connected to a first terminal with a high
A second switch circuit connected to a second terminal having a lower potential than the terminal of , a heating transformer is connected between the power points of the first and second switch circuits, and a terminal of the reference potential of the voltage controller. 1. A heating circuit for an X-ray device, characterized in that a heating circuit is connected to an X-ray device. 2. The first switch circuit and the second switch circuit described in claim 1 are bidirectional switch circuits, and at least the first switch circuit has an opening function, and the first switch circuit and the second switch circuit are bidirectional switch circuits. A heating circuit for an X-ray apparatus, wherein the second switch circuit operates in a complementary manner. 3. A heating circuit for an X-ray apparatus according to claim 1, characterized in that a capacitor is connected in parallel between the terminals of the heating transformer. 4. Heating of an X-ray apparatus, characterized in that, in the switch circuit according to claim 2, the voltage applied to the heating transformer is controlled by opening and closing at a frequency higher than the commercial frequency. circuit.