JP2507430Y2 - High voltage generator for X-ray CT - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a high voltage generator for X-ray CT, and more particularly to a high voltage generator for X-ray CT in which a switching element of an inverter is prevented from being destroyed by overvoltage. Regarding the device.

[Prior Art] An example of this type of high voltage generator for X-ray CT is shown in FIG.

In the high voltage generator 50 for X-ray CT, the three-phase AC of the commercial power source is converted into a DC voltage by the rectifying circuit 11 and the smoothing circuit 12.

This DC voltage is inversely converted into an AC having a sufficiently high frequency by the inverter 51, and is supplied to the rectifying / boosting circuit 14 via the high voltage transformer T.

The rectifying / boosting circuit 14 converts the AC voltage on the secondary side of the high-voltage transformer T into a DC high voltage and outputs it to the X-ray tube 15.

The high DC voltage output from the rectifying / boosting circuit 14 is fed back to the PWM control circuit 16, and the PWM control circuit 16 controls the inverter 51 based on this.

FIG. 4 is a circuit diagram showing the configuration of the conventional inverter 51.

This inverter 51 has a bridge formed by switching elements S1 to S4, and has a current limiting inductance.
It is connected to the high voltage transformer T via La and Lb.

To protect the switching elements S1 to S4, absorbers A1 to A4 are connected to the switching elements S1 to S4, respectively.

[Problems to be solved by the invention] Abnormal discharge may occur on the X-ray tube 15 side, and at this time, a steep high voltage is transmitted to the primary side of the high-voltage transformer T through the stray capacitance of the high-voltage transformer T. .

This steep high voltage cannot be sufficiently absorbed by the diodes and the absorbers A1 to A4 due to the high frequency band, and the switching elements S1 to S4 may be destroyed.

Therefore, the purpose of this invention is to prevent the switching element of the inverter from being destroyed by the steep high voltage transmitted from the high voltage transformer T due to the abnormal discharge generated on the X-ray tube 15 side. To provide a high voltage generator for use.

[Means for Solving the Problems] The high voltage generator for X-ray CT according to the present invention reverse-converts a DC voltage obtained by rectifying an AC current with an inverter, and then converts the DC voltage into a rectifying / boosting circuit via a high-voltage transformer. A high-voltage generator for X-ray CT that supplies and outputs to the X-ray tube side as a DC high voltage is characterized in that a common mode filter is provided between the inverter and the high-voltage transformer. Is.

[Operation] The steep high voltage generated by the abnormal discharge generated on the X-ray tube side and transmitted through the high voltage transformer is common mode noise when viewed from the inverter side.

However, a common
Since the mode filter is installed, the common mode noise is absorbed.

That is, destruction of the switching element of the inverter can be prevented.

[Embodiment] Hereinafter, the present invention will be described in more detail based on an embodiment shown in the drawings. The invention is not limited to this.

The overall structure of the high voltage generator 10 for X-ray CT of one embodiment of the present invention is as shown in the block diagram of FIG. As can be understood by comparing with FIG. 3, the conventional device 10 is different from the conventional device 10 in that the conventional inverter 51 is used instead.

FIG. 1 shows the inverter 1. The inverter 1 has switching elements S1 to S4 formed in a bridge, and is connected to a high voltage transformer T via inductances L1 and L2.

At the connection point between the inductances L1 and L2 and the inverter 1,
Capacitors C1 and C2 are connected.

These inductances L1 and L2, capacitors C1 and C2,
A common mode filter is formed by the capacitor C3.

When an abnormal discharge occurs on the X-ray tube 15 side and a steep high voltage flows into the inverter 1 side via the stray capacitance of the high voltage transformer T, the inductances L1 and L2 and the capacitors C1 and C
The common mode filter formed by 2 and C3 absorbs (misses) the steep high voltage that has flowed in.

Therefore, a steep high voltage is not applied to the switching elements S1 to S4 of the inverter 1, and the switching elements S1 to S4 are prevented from being destroyed.

The inductances L1 and L2 are preferably selected so as to also function as the current limiting inductance in the normal mode.

[Effect of the Invention] According to the high voltage generator for X-ray CT of the present invention, the switching element is destroyed by the steep high voltage transmitted to the inverter side due to the abnormal discharge generated on the X-ray tube side. Will be prevented.

[Brief description of drawings]

FIG. 1 is a circuit diagram of an inverter and a high voltage transformer of an X-ray CT high voltage generator according to an embodiment of the present invention, and FIG. 2 is an overall configuration of an X-ray CT high voltage generator according to an embodiment of the present invention. FIG. 3 is a block diagram showing the overall configuration of an example of a conventional high voltage generator for X-ray CT, and FIG. 4 is a conventional X-ray CT high voltage generator.
It is a circuit diagram of an example of an inverter and a high voltage transformer of a high voltage generator for line CT. (Explanation of symbols) 1 …… Inverter 10 …… High voltage generator for X-ray CT T …… High voltage transformer L1, L2 …… Inductance C1 to C3 …… Capacitor S1 to S4 …… Switching element.

Claims (1)

(57) [Scope of utility model registration request] Claim: What is claimed is: 1. A DC voltage obtained by rectifying an AC current is inversely converted by an inverter, and then supplied to a rectifying / boosting circuit via a high-voltage transformer and output as a DC high voltage to the X-ray tube side.
A high voltage generator for X-ray CT, characterized in that a common mode filter is provided between the inverter and the high voltage transformer.