JPS5814560Y2 - High voltage power supply circuit for X-ray automatic blackening degree adjustment device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a high-voltage power supply circuit for an X-ray automatic darkening degree adjustment device for supplying a high voltage to an X-ray detector in the X-ray automatic darkening degree adjustment device.

Conventionally, as shown in FIG. 1, a high voltage power supply circuit for this type of automatic X-ray darkening degree adjustment device uses an AC high voltage boosted to a high voltage of 650V by a power transformer (not shown), for example, through a diode. Directly rectified by bridge DB and stabilized using Zener diodes ZD1 to ZD6, variable resistor VR.

It is common to have a configuration in which high voltages appropriately set by ~VR3 are switched by relay contacts RY and ~RY2 to obtain a required negative high voltage.

With this kind of circuit configuration, a high voltage of about -800V is directly switched and controlled, so special components with high withstand voltage are required, and signals are exchanged with the X-ray controller and low voltage control signals are required. It was not easy to switch high voltages due to

Furthermore, it has been difficult to form a compact and lightweight unit.

The present invention was developed based on these circumstances, and it uses a so-called high-frequency DC-DC converter system and has a simple configuration to stabilize the operation and continuously variable control of the output high voltage supplied to the X-ray detector. It is an object of the present invention to provide a high-voltage power supply circuit for an X-ray automatic darkening degree adjustment device, which can be easily and reliably performed using a low voltage signal, and also allows the device to be made smaller and lighter.

Embodiments of the present invention will be described below with reference to the drawings.

In Fig. 2, 1 first creates a pulse train with a frequency of 40 kHz, and then converts this into J -K 7 'J ''77'7
An oscillation circuit that outputs a positive and negative pulse train with a frequency of 20 kHz and a duty ratio of 50% by dividing the frequency by 1/2 using a 0-tube, etc. 2 delays only the leading edge of the pulse train of the output pulse train of the oscillation circuit 1 by about 8 μs, for example. A delay circuit 3 is a low voltage circuit that variably controls and outputs a DC low voltage in the range of, for example, +5V to +15V; 4 is a low voltage circuit that alternately controls the DC low voltage supplied from the low voltage circuit 3 by a pulse train given from the delay circuit 2; A switching circuit 5 performs switching to apply voltage to a converter transformer, boost the voltage, and output the voltage. 5 is a rectifier circuit that rectifies and smoothes the output of the switching circuit 4 to obtain a high voltage DC output.

Specifically, the delay circuit 2 and the switching circuit 4 described above are configured as shown in FIG. 3, for example.

In FIG. 3, it is assumed that the oscillation circuit 1 outputs positive and negative pulse trains separately, that is, as a set of pulse trains with mutually opposite phases.

The delay circuit 2 includes a diode D1, a resistor R1, a capacitor C1, and an inverter 1, as shown in the figure, in order to delay only the leading edge of each pulse for each of the sets of pulse trains.
1 to I3, diode D2, resistor R2, capacitor C
2. It is configured using inverters I4 to I6.

The switching circuit 4 also includes a pair of transistors Ql and Q2 that alternately switch the DC voltage supplied across the capacitor C3 from the low voltage circuit 3 by positive and negative pulse trains from the delay circuit 2, and the transistors Q1 and Q2. It is constructed using a converter transformer TR which is supplied with a high frequency voltage switched by the converter and boosts the voltage to a value corresponding to the required high voltage.

In this configuration, a set of pulse trains with a frequency of 20 kHz, a duty ratio of 50%, and mutually opposite phases as shown in g and b of Fig. 4 are output from the oscillation circuit 1 at points A and B shown in Fig. 3. , in the delay circuit 2, only the leading edge of the pulse of each pulse train is delayed by about 8 μS in this case.
Waveforms as shown in FIG. Q2 is switched.

Then, the output DC voltage of the low voltage circuit 3 is alternately switched, and a signal as shown in FIG.
It is rectified by

By doing this, the output of the low voltage circuit 3 is increased by +5
If the voltage is varied in the range of V to +15V, the high voltage DC output of the rectifier circuit 5 can be continuously varied in the range of, for example, -300V to -900V.

By the way, when using a high frequency DC-DC converter circuit, the switching transistor Q1. Since there is a difference in the switching response time characteristics of Q2, the pulse train with a frequency of 20k)lz, which is obtained by dividing the pulse train with a frequency of 40kHz by 1/2, becomes T1=T2 (duty ratio 50%) as shown in Figure 4a and b.
), if the switching transistors Ql and Q2 are directly switched by this, the difference in response time characteristics will cause the transistors Ql and Q2 to switch directly.
There is a danger that both may be turned on at the same time.

If they are turned on at the same time, there is a risk that the primary side current of the converter transformer TR will flow excessively and destroy components.

Therefore, in the above embodiment, as shown in FIG. 4e and f, the leading edge of the pulse is delayed by time t (approximately 8 μs in this case) so as to narrow the on-time width of transistors Q1 and Q2, and (Q1 base signal pulse width )””rt t・・・・・・
・ (1) (Q2 base signal pulse m) = T2-t...
... (2).

Therefore, as shown in FIG. 4g, a pause period of time t is inserted during alternate switching, so that it is possible to prevent the primary current of the converter transformer from flowing excessively.

Furthermore, if the stray capacitance between the windings of the converter transformer TR itself is approximately 209 F, if switching is performed at a high frequency of 20 kHz, an excessive primary current will flow due to the stray capacitance. This can also be prevented.

Further, by creating a pause period between switching in this way, there is an advantage that spike voltages during switching can be removed.

Therefore, by employing the above-mentioned high frequency DC-DC converter, when two or more X-ray detectors are switched and used, the output high voltage can be increased by simply controlling the output voltage of the low voltage circuit 3 within a narrow range. Continuous control over a wide range, any
Optimal high voltage can also be supplied to line detectors.

In addition, when combined with a semiconductor or IC X-ray controller, it becomes possible to transfer low-voltage digital signals.
Another advantage is that components such as transformers can be made smaller, and the circuit can be constructed in a manner similar to that used for processing printed circuit boards used in low-voltage circuits.

Note that the low voltage circuit 3 described above may have a configuration in which the output voltage of the X-ray controller itself changes, or may have a configuration in which the output voltage of the low voltage circuit 3 is changed depending on the output of the X-ray controller.

In addition, the present invention is not limited to the embodiments described above and shown in the drawings, but can be implemented with various modifications without changing the gist thereof.

As mentioned above, the present invention allows the so-called high frequency DC-
Using a DC converter system and a simple configuration, the operation is stabilized, and the continuous variable control of the output high voltage supplied to the X-ray detector can be performed easily and reliably using a low voltage signal, and the device is also smaller and lighter. It is possible to provide a high-voltage power supply circuit for an automatic X-ray darkening degree control device.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing an example of a conventional device, FIG. 2 is a block diagram showing the configuration of an embodiment of the present invention, and FIG. 3 is a circuit diagram showing a specific example of the configuration of main parts in the same embodiment. Figure 4 a~
g is a waveform diagram showing waveforms of various parts in the above configuration example. 1...Oscillation circuit, 2...Delay circuit, 3
...Low voltage circuit, 4 ... Switching circuit, 5 ... Rectifier circuit.

Claims (1)

[Scope of utility model registration request] In a high-voltage power supply circuit for an X-ray automatic darkening degree adjustment device for supplying high voltage to an X-ray detector used in the X-ray automatic darkening degree adjustment device, an oscillation circuit that generates a high-frequency alternating switching pulse train; A delay circuit that delays the leading edge of the pulse of the output pulse train of this oscillation circuit by an appropriate time, a low voltage output circuit that outputs a DC low voltage and continuously variable control of this output voltage, and a pulse train obtained through the delay circuit. High frequency DC-DC consisting of a switching circuit that alternately switches the output from the low voltage output circuit and supplies it to the transformer to boost the voltage, and a rectifier circuit that rectifies and smoothes this switching output.
A high-voltage power supply circuit for an automatic X-ray darkening degree adjustment device, characterized in that it is configured using a converter.