JPH07298620A - Dc high-voltage power source - Google Patents

Abstract

PURPOSE:To detect an electric insulation state between positive and negative DC output terminals by comparing an electric insulation state discriminator with reference values of an output voltage detection signal and a current detection signal, and applying a stop signal for stopping an operation of an inverter according to a compared result with the reference values to a controller. CONSTITUTION:An output voltage detector 7 detects a DC high voltage generated from a first DC high voltage generator 5 and outputs an output voltage detection signal. A current detector 10 detects a current flowing between a second DC high voltage generator 6 and a grounded neutral point N, and outputs a current detection signal. The output voltage detection signal and the current detection signal are applied to a controller 11 and an electric insulation state discriminator 14, which compares the reference value of the output voltage detection signal with that of the current detection signal. When the output voltage detection signal is lowered as compared with the reference value, or when the current detection signal is higher than the reference value, a stop signal for stopping the operation of the inverter 2 is applied to the controller 11.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a DC high voltage power supply device used in a high voltage load device such as an X-ray generator.

[0002]

2. Description of the Related Art In recent years, miniaturization and high frequency operation of medical X-ray power supply devices have been partially promoted. In particular, the dental X-ray power supply is required to be downsized in order to effectively use the space in the medical field. To meet this demand for downsizing, an inverter is used, and the high voltage circuit and the X-ray tube are mounted in the same tank (hereinafter It is called one-tank).
With this one-tank and downsizing, the distance between the grounded metal tank and the printed circuit board, circuit parts, or connecting conductors that compose the DC high-voltage power supply becomes narrower, and these are the metal tanks. The number of accidents that cause a short circuit by contacting the Another cause of the accident is that the temperature of the insulating oil in the metal tank increases due to the heat generated by the X-ray tube and the deterioration of the insulating oil accelerates.

In such a conventional DC high voltage power supply device, there is one that employs a method of outputting a DC high voltage of either positive or negative polarity using a single Cockcroft-Walton circuit. In most cases, the overcurrent detection function is used to detect a phenomenon in which the current flowing through the circuit remarkably increases when a short circuit accident occurs, and when this phenomenon is detected, the operation of the inverter circuit is stopped.

[0004]

However, in a load device such as an X-ray device for industrial use or medical use, which requires a particularly high DC voltage, a pair of load devices is required in order to simplify the electrical insulation design. using different Cockcroft Walton circuit polarities, the output voltage + V _O equal voltage value of the reverse polarity relative to the ground point, the -V _O occurs, also applying a DC high voltage of 2V _O across the X-ray tube Is beginning to take place. In the DC high voltage power supply device having such a configuration,
Electrical insulation between positive DC output terminal and ground, electrical insulation between negative DC output terminal and ground, and electrical insulation between positive DC output terminal and negative DC output terminal Although it is necessary to detect the state, there is a problem that the electrical insulation state between the positive DC output terminal and the negative DC output terminal cannot be detected only by the overcurrent detection function. Also, when attempting all of these, both in the traditional view of the output voltage + V _O, a voltage detecting function of detecting the -V _O, the ability to detect both current and requires determination function to determine the respective detection signals Therefore, the circuit becomes complicated, the reliability is lowered, and it is difficult to reduce the cost.

The main object of the present invention is to solve the above problems of the conventional device and to provide a high voltage DC power supply device which is economical and reliable.

[0006]

In order to solve such a problem, in the first invention, an inverter circuit for converting DC power into a high frequency output, a control circuit for controlling the inverter circuit, and an AC circuit for the inverter circuit are provided. A transformer having a primary winding and a secondary winding connected to an output terminal, and a first winding connected to the secondary winding of the transformer to output a positive DC high voltage and a negative DC high voltage, respectively. In the DC high-voltage power supply device including a DC high-voltage generating circuit, a second DC high-voltage generating circuit, an output voltage detecting circuit, and a current detecting circuit, the output voltage detecting circuit includes: The DC high voltage generated by the first DC high voltage generation circuit is detected and an output voltage detection signal is output, and the current detection circuit connects the second DC high voltage generation circuit and the grounded neutral point. By detecting the current flowing between A current detection signal, and the output voltage detection signal and the current detection signal are given to the control circuit and also to an electrical insulation state determination circuit, and the electrical insulation state determination circuit outputs the output voltage detection signal and the current. When the output voltage detection signal is lower than the corresponding reference value or the current detection signal is higher than the corresponding reference value by comparing the detection signal with each reference value, the inverter circuit The present invention provides a DC high-voltage power supply device characterized in that a stop signal for stopping the operation of is supplied to a control circuit.

In order to solve such a problem, in the second invention, the output voltage detection circuit detects the DC high voltage generated by the first DC high voltage generation circuit and outputs the output voltage detection signal as the output voltage detection signal. The current detection circuit outputs the same to the output voltage detection signal by detecting the DC current flowing between the second DC high voltage generation circuit and the grounded neutral point. A polar current detection signal is output to the electrical insulation state determination circuit, and the electrical insulation state determination circuit has a function of comparing the respective detection signals with a comparator having a single polarity power supply voltage. An object of the present invention is to provide a DC high voltage power supply device according to item 1.

In order to solve such a problem, in the third aspect of the invention, in the electrical insulation state determination circuit, the load connected between the DC high voltage output terminals is in the on state or in the off state. The DC high-voltage power supply device according to claim 1 or 2, wherein the electrical insulation state is determined when a load voltage is equal to or higher than a set value by receiving a signal indicating that. is there.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIG. FIG. 1 shows an embodiment of a DC high voltage power supply for an X-ray generator, 1 is an AC-DC converter for converting commercial AC power into DC power, and 2 is DC power from the AC-DC converter. Circuit for converting a high frequency AC power of approximately 80 kHz, 3 is an inductor for limiting current, 4 is a transformer having a primary winding 4P and a secondary winding 4S, and 5 is a Cockcroft-Walton circuit having a normal configuration. A first DC voltage generating circuit for outputting a positive DC high voltage, and 6 is a second DC voltage generating circuit for outputting a negative DC high voltage, which has the same configuration as the first DC voltage generating circuit 5. Reference numeral 7 is an output voltage detection circuit composed of a plurality of resistors and capacitors connected in series, which divides the output voltage of the first DC voltage generation circuit 5 and detects a proportional voltage to give an output voltage detection signal S _1. And 8 ' Zoresei, X-rays tube negative output terminal, 9 is connected between the output terminal 8 8 ', 10
Is a current detection circuit connected between the ground point, which is a neutral point, and one AC input point of the second DC voltage generation circuit,
In a simple configuration, it consists of a resistor and a capacitor that bypasses the high frequency current connected in parallel. Therefore, under normal conditions, the current detection circuit 10 gives a current detection signal S ₂ which is substantially proportional to the tube current flowing between the anode A and the cathode K of the X-ray tube 9.

[0010] 11 receives the output voltage detection signals S ₁ and the current detection signal S _2, the control circuit for controlling the inverter circuit 2, 12 receives the DC output of the AC over DC converter 1,
During normal operation, the current detection signal S that is almost proportional to the tube current
Filament power control circuit that outputs filament power controlled based on ₂ , 13 is an insulation transformer, and 14 is an electric insulation state determination that gives an inverter operation stop signal S ₃ to the control circuit 11 when a defect in the electric insulation state is detected. Circuit. The electrical insulation state determination circuit 14 includes a first comparator 14B that compares the output voltage detection signal S ₁ with a reference value of the first reference source 14A, a current detection signal S ₂ and a second comparator 14B.
A second comparator 14D for comparing with a reference value of the reference source 14C, a delay circuit 14 for delaying an ON / OFF signal of this power supply device for a predetermined time.
E, delayed on / off signal and first comparator 1
4B, the first and second NAND gate circuits 14F and 14G which perform NAND logic on the output signals from the second comparator 14D, and these NAND gate circuits 14F and 14F, respectively.
First and second flip-flop circuits 14H and 14 for latching respective signals from 14G for a certain period of time
It consists of I.

Next, the operation will be described. When the operator turns on a switch of an X-ray imaging apparatus (not shown), an ON signal is given to the control circuit 11 and the control circuit 11
Gives a start signal to the inverter circuit 2 to start it,
Control. As a result, the inverter circuit 2 is approximately 80k.
High frequency AC power of Hz is supplied to the first DC voltage generating circuit 5 and the second DC voltage generating circuit 6 through the transformer 4,
These first, second DC voltage generation circuit 5 and 6 each predetermined DC output voltage + V _O, the -V _O, the output terminal 8,
The voltage is applied between the anode A and the cathode K of the X-ray tube 9 connected to 8 '. At this time, the ON signal is also applied to the electrical insulation state determination circuit 14, but the delay circuit 14E causes the output terminal 8
Since the ON signal is not passed through the NAND gate circuits 14F and 14G for a predetermined delay time until the DC output voltage of rises to a predetermined value, the electrical insulation state determination circuit 14 outputs the output voltage detection signal S ₁ and the current detection signal. Inverter operation stop signal S regardless of signal S ₂
Do not give ₃ . When a predetermined time has passed, the ON signal passes through the delay circuit 14E and the NAND gate circuits 14F and 14G.
Entered in. In a normal state, the output voltage detection signal S ₁
Is higher than the reference value of the reference source 14A, and the current detection signal S ₂
Is approximately proportional to the tube current flowing between the anode A and the cathode K of the X-ray tube 9 and is lower than the reference value of the reference source 14C. Therefore, the output signals of the comparators 14B and 14D are at low level, and the first and second flip-flop circuits 14
The inverter operation stop signal S ₃ is latched at a low level by H and 14I and does not affect the control circuit 11.

When operating in such a state, if a short circuit accident occurs between the output terminal 8 of the first DC voltage generating circuit 5 side and the ground, the DC output voltage of the output terminal 8 will drop significantly. Becomes almost zero, and the output voltage detection signal S ₁ becomes lower than the reference value of the reference source 14A. Therefore, the output signal of the comparator 14B changes from the low level to the high level, the output signal of the NAND gate circuit 14F also changes from the low level to the high level, and the flip-flop circuit 14H
Trigger. Along with this, the flip-flop circuit 14H
The output signal of 1 transitions to a high level, the electrical insulation state determination circuit 14 gives an inverter operation stop signal S ₃ to the control circuit 11, and the inverter circuit 2 stops its operation. Therefore,
It is possible to prevent an accident in which an excessive current flows to the first DC voltage generating circuit 5 side and damages circuit components and the like. At this time, the tube current flowing through the X-ray tube 9 naturally decreases, so the current detection signal S ₂
Remains lower than the reference value of the reference source 14C, and the output state of the second flip-flop circuit 14I does not change.

If an electrical insulation defect occurs between the output terminal 8'on the side of the second DC voltage generating circuit 6 and the ground, for example, if the output terminal 8'is short-circuited to the ground point, the transformer 4's 2
When the black dot side of the secondary winding 4S has a positive polarity, current flows from the black dot side to the non-black dot side of the secondary winding 4S of the transformer 4 through the neutral point N, the output terminal 8'and the second DC voltage generating circuit 6. Since it flows in, in this half cycle, the current detection circuit 10
No current flows. Next, when the black dot side of the secondary winding 4S of the transformer 4 has a negative polarity, current flows from the non-black dot side of the secondary winding 4S of the transformer 4 to the first-stage capacitor 6C1 of the second DC voltage generating circuit 6. Secondary winding 4S of transformer 4 through diode 6D1, current detection circuit 10 and neutral point N
Flows into the sunspot side. Therefore, the DC current flowing in the arrow direction through the current detection circuit 10 increases, the current detection signal S ₂ becomes higher than the reference value of the reference source 14C, the output signal of the comparator 14D changes from the low level to the high level, and the NAND The output signal of the gate circuit 14G also changes from low level to high level to trigger the flip-flop circuit 14I. Along with this, the output signal of the flip-flop circuit 14I transits to a high level, and the electrical insulation state determination circuit 1
4 supplies the inverter operation stop signal S ₃ to the control circuit 11, and the inverter circuit 2 stops its operation.

Next, when an electrical insulation failure occurs between the output terminals 8 and 8 ', the first DC voltage generating circuit 5, the output terminal 8 and the first DC voltage generating circuit 5 from one terminal side of the secondary winding 4S of the transformer 4.
8 ', the second DC voltage generating circuit 6, the current detecting circuit 10 and the neutral point N, the current flowing to the other terminal side of the secondary winding 4S of the transformer 4, that is, the DC flowing in the arrow direction through the current detecting circuit 10. The current increases and the current detection signal S ₂
Becomes higher than the reference value of the reference source 14C. Therefore,
The output signal of the comparator 14D changes from the low level to the high level, and the output signal of the NAND gate circuit 14G also changes from the low level to the high level.
4I trigger. Along with this, the flip-flop circuit 1
The 4I output signal transits to a high level, and the electrical insulation state determination circuit 14 outputs the inverter operation stop signal S ₃ to the control circuit 11
The inverter circuit 2 stops operating.

As can be seen from the above description, according to the present invention, a pair of direct currents can be provided without increasing the number of voltage detecting circuits and current detecting circuits which are generally required even in the case of a single direct current voltage generating circuit. Electrical breakdown in three places in a DC voltage power supply device provided with a voltage generating circuit, that is, an output terminal 8 on the first DC voltage generating circuit 5 side, an output terminal 8'on the second DC voltage generating circuit 6 side, and an output Defective electrical insulation can be detected between terminals 8 and 8 '. Moreover, since both the voltage detection signal S ₁ and the current detection signal S ₂ are positive in both normal and abnormal states, the comparator 1 of the electrical insulation state determination circuit 14
Both 4B and 14D need only have a power source that supplies a voltage of positive polarity, and need not be a high-priced comparator that has a power source that supplies a voltage of both polarities, which is economically superior.

In the embodiment described above, a high-frequency alternating current flows through the current detection circuit 10, but as shown in FIG. 2, the cathode of the diode 6D1 of the second DC voltage generation circuit 6 and the capacitor 6C2 are connected. Disconnect, capacitor 6C
By grounding the separated one end of 2, only the direct current in the direction of the arrow flows. Regarding this point, when the voltage induced in the secondary winding 4S of the transformer 4 in FIG. 1 is positive on the non-black dot side with respect to the black dot side, the current is the capacitor 6C1 and the diode 6D1 of the DC voltage generating circuit 6. , The current detection circuit 10 and the neutral point N flow in the direction of the arrow, but when the voltage induced in the secondary winding 4S of the transformer 4 is positive on the black dot side with respect to the non-black dot side, the current is at the neutral point. It flows through the N, ground and DC voltage generation circuit 6, and the current detection circuit 10 is bypassed. Therefore, in both normal and abnormal cases, only the direct current in the direction of the arrow in the drawing flows through the current detection circuit 10, and the load current can be accurately detected. Further, in the above embodiment, the first and second DC voltage generating circuits 5 and 6 are shown as Cockcroft-Walton circuits, but other boosting / rectifying type circuits such as a voltage doubler circuit may be used. Furthermore, although the X-ray generator has been described in the embodiment, it can be similarly applied to other high voltage loads, and the conversion frequency of the inverter circuit may be arbitrary.

[0017]

As described above, according to the present invention, it is possible to detect the electrical insulation failure at each location without increasing the number of voltage detection circuits and current detection circuits. Therefore, it is economical and reliable. Also, since the electric insulation state determination circuit can be made inexpensive, the practical effect is very large.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of the present invention.

FIG. 2 is a diagram showing another example of current detection in one embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... AC-DC converter 2 ... Inverter circuit 3 ... Inductor 4 ... Transformer 5 ... 1st DC voltage generation circuit 6 ... 2nd DC voltage generation circuit 7 ... Output voltage detection circuit 8, 8 '... Output terminal 9 ... X-ray tube 10 ... Current detection circuit 11 ... Control circuit 12 ... Filament power control circuit 13 ... Insulation transformer 14 ... Circuits 14A, 14C ... Reference sources 14B, 14D
..Comparator 14E ... Delay circuit 14F, 14G ... NAND gate circuit 14H, 14I ... Flip-flop circuit

Claims (3)

[Claims] 1. A transformer comprising an inverter circuit for converting DC power into a high frequency output, a control circuit for controlling the inverter circuit, and a primary winding and a secondary winding connected to an AC output terminal of the inverter circuit. A first direct current high voltage generation circuit, a second direct current high voltage generation circuit, and an output voltage detection circuit which are connected between the secondary windings of the transformer and output a positive direct current high voltage and a negative direct current high voltage, respectively. , And a current detection circuit, wherein the output voltage detection circuit detects a DC high voltage generated by the first DC high voltage generation circuit, and outputs the output voltage. Outputting a detection signal, the current detection circuit detects a current flowing between the second DC high voltage generation circuit and the grounded neutral point, and outputs a current detection signal; And the current detection signal is The electrical insulation state determination circuit is provided to the control circuit and the electrical isolation state determination circuit, and the electrical isolation state determination circuit compares the output voltage detection signal and the current detection signal with respective reference values, and the output voltage detection signal is If it falls below the corresponding reference value,
Alternatively, when the current detection signal becomes higher than the corresponding reference value, a stop signal for stopping the operation of the inverter circuit is given to the control circuit, and the DC high voltage power supply device is characterized. 2. The output voltage detection circuit detects a DC high voltage generated by the first DC high voltage generation circuit and outputs an output voltage detection signal to the electrical insulation state determination circuit, and the current detection circuit. Detects a DC current flowing between the second DC high voltage generating circuit and the grounded neutral point, and outputs a current detection signal having the same polarity as the output voltage detection signal to the electrical insulation state determination circuit. The DC high voltage power supply device according to claim 1, wherein the electrical insulation state determination circuit has a function of comparing the respective detection signals with a comparator having a single polarity power supply voltage. 3. The electrical insulation state determination circuit receives a signal indicating whether a load connected between the DC high voltage output terminals is in an ON state or an OFF state, and the load voltage is equal to or higher than a set value. The DC high-voltage power supply device according to claim 1 or 2, wherein the electrical insulation state is determined at a certain time.