JPS634422B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a high voltage generator suitable for supplying high voltage power to an X-ray generator, a laser generator, etc.

Drives X-ray generators, laser generators, etc.
High-voltage power of 100KV to 400KV is conventionally generated by boosting alternating current of several hundred hertz from the commercial frequency using a transformer having a silicon steel plate as a magnetic core. This type of high-voltage generator converts a large amount of power, from several kilowatts to several hundred kilowatts, and requires high frequency of power on/off. Moreover, the distance to the load is generally long, so long high-voltage cables are used to supply power. It has the special characteristic of doing so. Considering these special characteristics, the operating frequency for stably and economically generating high voltage has conventionally been suppressed to about several hundred hertz. This operating frequency is an important design element that determines the limits of the shape of the transformer and the rapid response of the high pressure generator. Therefore, in order to make the conventional transformer more compact and to increase the adaptability of the device, it is desired to increase the operating frequency by more than an order of magnitude compared to the conventional transformer.

However, in the past, alternating current is often simply boosted using a transformer, and in this case, as the operating frequency increases, the reactance due to the leakage inductance and distributed capacitance of the transformer increases, and as a result, the transformer A problem occurred in which the reactance component of the impedance seen from the primary winding side was larger than the actual resistance component of the load. In other words, there was a problem in that the reactive power increased and the power supplied to loads such as an X-ray tube decreased, making it unsuitable for large power conversion. Further, according to such a conventional device, even when the input power is turned on, power is supplied to the load while supplying power to the reactance component, so there is a problem that the quick response is poor. Furthermore, when the input power supply is cut off, the energy remaining in the reactance component is transferred to the load after the cutoff, and the power supply is not immediately stopped, resulting in a delay in system operation.

The present invention has been made in consideration of these circumstances, and its purpose is to increase the operating frequency of the transformer to efficiently boost a predetermined high voltage, thereby delivering a predetermined amount of power to the load. It is an object of the present invention to provide a high voltage generating device that is quick-responsive, simple, and highly practical, capable of stably transmitting.

That is, the present invention obtains a predetermined high voltage boosted through a miniaturized transformer using alternating current or pulse waves of several kilohertz or more with a reduced reactance component, and supplies this to a load with high efficiency. The purpose of the present invention is to provide a high voltage generator with quick response that makes it possible to do this.

The outline of the present invention is to connect the primary winding of a step-up transformer to the load of a step-up single-ended switch circuit via a diode as a polarity reversal switch circuit, and to Connect charging diodes with the same polarity to the next winding via a capacitor, and connect voltage summing diodes in series with the same polarity between these charging diodes. By taking out power from both ends of the series circuit, high-power, high-voltage, high-speed switching operation is possible, thereby effectively achieving the above-mentioned purpose.

Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a schematic configuration diagram of an embodiment of the apparatus. A switch element 3 consisting of a transistor is connected to an input DC power source 1 via a choke coil 2, forming a step-up single-ended switch circuit. The switch element 3 opens and closes at an operating frequency of several kilohertz, for example. still,
It is also possible to use other elements as the switch element 3, such as a thyristor. The primary winding ₅₁ of the transformer 5 is connected to this switch element 3 via a diode 4 serving as a polarity inversion switch circuit, and serves as a load for the single-ended switch circuit. Further, the secondary side of the transformer 5 is provided with a plurality of multi-divided secondary windings 5 ₂₁ , 5 ₂₂ to 5 _2n . These secondary windings 5 ₂₁ , 5 ₂₂ to 5 _2n are
The number of turns is set to be equal, and the number of turns is set to be (1:-n) with respect to the primary winding ₅₁ .
And these secondary windings 5 ₂₁ , 5 ₂₂ to 5 _2n have
Capacitors 6 ₁ , 6 ₂ to 6 _n for power transfer are connected to the terminal ends of the respective windings, and charging diodes 7 ₁ , 7 ₂ to 7 _n are connected via these capacitors 6 ₁ , 6 ₂ to 6 _n separately. are connected in parallel with their polar directions aligned. In other words, the diodes 7 ₁ , 7 ₂ to 7 _n are
The anode is connected to the starting end of each secondary winding 5 ₂₁ , 5 ₂₂ to 5 _2n , and the cathode is connected to the capacitor 6 ₁ , 6 ₂
~ _6n to the terminal ends of the secondary windings ₅₂₁ , ₅₂₂ ~ _52n . Between these charging diodes 7 ₁ , 7 ₂ - 7 _n , voltage adding diodes 8 ₁ , 8 ₂ - 8 _n- are connected with the same polarity direction as these diodes 7 ₁ , 7 ₂ - 7 _n . ₁ are connected in series. As a result, each of the diodes 7 ₁ , 7 ₂ to 7 _n , 8 ₁ , 8 ₂ to 8 _n-1
are alternately connected in series with their polarities aligned to form a series circuit. Both ends of this series circuit, that is, the cathode of diode 7 ₁ and diode 7 _n
The anode of is used as a high voltage output terminal, and an X-ray tube 10 as a load is connected to this via a high voltage cable 9. Note that the inductance L and capacitance C added to the high-voltage cable 9 indicate the inductance component and distributed capacitance component of the load included in the high-voltage cable 9, respectively.

Now, in this device configured in this way,
Switch element 3 conducts with a constant pulse width Ton,
It is assumed that the opening/closing operation is performed at a period T (T>Ton) and a steady state is entered. At this time, a constant current Ii flows through the chain 2, and constant voltages _e1 ', _e2 - _{en '} are present in the capacitors ₆₁ , _62-6n , respectively. still,
It is assumed that the switch element 3 functions as an ideal switch with a resistance value of zero when conductive and an infinite resistance value when disconnected, the excitation inductance L of the transformer 5 having a finite value, and its leakage inductance being negligible in terms of operation. It is also assumed that the apparent resistance value of the X-ray tube 10 is constant.

The operation of the present apparatus in this steady state will be explained with reference to the equivalent circuits shown in FIGS. 2a and 2b and the operation waveform diagrams shown in FIGS. 3a to 3c.

Now, when the switch element 3 is conducting, that is, during the period Ton, the switch coil 2 is connected to the negative side of the power supply 1, and the current stored in the excitation inductance of the transformer 5 is transmitted to the load 10. Since the current stored in the excitation inductance is decreasing, the diode 4 is reverse biased and in a cutoff state. Therefore, in this case, the equivalent circuit of the device is shown as shown in FIG. 2a. Then, as shown in Figure 3a, the current i _L2 flowing through the chi-yoke coil 2 rises from the current Ii in the steady state with a slope equal to the value obtained by dividing the input power supply voltage Ein by the inductance _L2 of the chi-yoke coil 2. do. On the other hand, the excitation inductance 1 of the transformer 5
The current i _L11 stored in the transformer 5 is passed through the leakage inductances 12 ₁ , 12 ₂ to 12 _n to the secondary terminal of the transformer 5 via the step-up function 13 indicated by the block.
Capacitors 6 ₁ , 6 ₂ to 6 _n , diodes 8 ₁ , 8 ₂
~8n _-1 to the load 10. During this time, voltages e ₁ ′, e ₂ ′ to e _M ′ are induced in one direction at the secondary terminals (each secondary winding) of the transformer 5, respectively, as shown by the arrows. Then, the induced voltages e ₁ ′, e ₂ ′ to e _M ′ and the capacitors 6 ₁ , 6 ₂ to 6 _n
The charging diodes 7 1 , 7 2 - 7 _n are respectively reverse biased by the voltages e ₁ , e ₂ -e _M stored in the diodes 7 ₁ , 7 ₂ -7 n. In other words, charging diodes 7 ₁ , 7 ₂
~7 _n is the voltage (e ₁ +e ₁ '), as shown in Figure 3c.
(e ₂ +e ₂ ′) to (e _M +e _M ′) are respectively reverse biased and turned off. Furthermore, the induced voltages e ₁ ′, e ₂ ′ to e _M are connected to the capacitors 6 ₁ ,
It is added to the voltages e ₁ , e ₂ -e _M stored in 6 ₂ - 6 _n , and added to the adding diodes 8 ₁ , 8 ₂ - 8 _n-1.
will be added to the series.

Next, when the switch element 3 is cut off, the diode 4 is positively biased, so that the current from the input power source 1 and the current stored in the choke coil 2 flow into the excitation inductance 11 of the transformer 5. As a result, the charging diodes 7 ₁ , 7 ₂ -
7 _n are all positively biased and conductive, and the equivalent circuit becomes as shown in Figure 2b. At this time, if the terminal voltage of the exciting inductance 11 is E′out, then
As shown in Figure 3a, the current flowing through the choke coil 2 varies from the current peak value Ipk to (E'out-
It decreases linearly with a slope of Ein)/L ₂ . At this time, a part of the current i _L2 of the chiyoke coil 2 is shunted to the exciting inductance ₁₁ as shown in FIG _.
~12 _n , charging capacitors 6 ₁ , 6 ₂ ~
6 _n and charges the capacitors 6 ₁ , 6 ₂ to 6 _n to the opposite polarity to that when they are conductive. Therefore, the voltages e ₁ , e ₂ -e _M are stored in the capacitors 6 ₁ , 6 ₂ -6 _n , respectively. After this state, the diodes 7 ₁ , 7 ₂ to 7 _n or 8 ₁ , 8 ₂ to 8 _n are connected to the on/off operation of the switch element 3.
_-1 conducts alternately and the voltage stored in the capacitors 6 ₁ , 6 ₂ to 6 _n and the induced voltage are added, and the load 1
It will be supplied to 0.

The basic operation of this device has been explained above, but when the leakage inductances 12 ₁ , 12 ₂ to 12 _n reach a level that cannot be ignored in terms of operation, the capacitor 6
The current flowing into the leakage inductances ₁₂ 1 , ₁₂ 2 - 12 _n causes a voltage drop in the leakage inductances 12 ₁ , 12 ₂ - 12 _n . This voltage drop causes capacitor 6 ₁ ,
The charging voltage of 6 ₂ to 6 _n decreases. This is an unfavorable phenomenon for the boosting function of this device. Incidentally, when the turns ratio of the transformer 5, which is constructed of general opposed flat wires, is 50 times or more, the values of the leakage inductances 12 ₁ , 12 ₂ to 12 _n are smaller than the excitation inductance 11. It reaches 20-30%. However, in this device, as mentioned above, the secondary windings 5 ₂₁ , 5 ₂₂ to 5 _2n are divided into a plurality of parts, and the summing diodes 8 ₁ , 8 ₂ to 8 _n-1 are connected between them.
Since the structure is such that the leakage inductances 12 ₁ , 12 ₂ to 12
_n can be kept as low as necessary and sufficient, and there is no risk of this causing any problems.

By the way, the diodes 7 ₁ , 7 ₂ to 7 _n and 8 ₁ , 8
A high-voltage cable 9 connects this apparatus, which has output ends at both ends of a series circuit of ₂ to 8 _n-1 , to a load consisting of an X-ray tube 10. This high-voltage cable 9 has an inductance component L and a distributed capacitance C, and as the cable 9 becomes longer, the values thereof generally cannot be ignored.

So now, inductance component L is added to cable 9.
If this exists, the current supplied to the load 10 during the conduction period of the switch element 3 will continue to flow by the inertia even if the switch element 3 is cut off. This inertial current flows from the load 10 to the diodes 7 ₁ , 7 ₂ to 7 _n , 8 ₁ , 8 ₂ to
Since it will flow through 8 _n-1 , Fig. 2b
The potentials of nodes G ₁ , G ₂ to _GM become equal to each other. However, during this inertial current period, each of the above nodes G ₁ ,
Even if the potentials of G ₂ to G _M are equal, the capacitor 6
₁ , 6 ₂ to 6 _n does not have any influence on charging. Rather, it has the effect of smoothing the current flowing through the load 9, which is advantageous for the load 9. In other words, the inductance component L of the cable 9 effectively acts on this device. On the other hand, the distributed capacitance C of the cable 9 is connected in parallel to the diodes 7 ₁ , 7 ₂ to 7 _n , 8 ₁ , 8 ₂ to 8 _n-1 . Therefore, this distributed capacitance C is always charged with voltage in the same direction. This means that the load 1
This means that the high voltage applied to the voltage is smoothed, and therefore it effectively acts on the present device and the load 10.

Thus, according to the present device, the leakage inductances 12 ₁ , 12 ₂ to 12 _n in the transformer 5 are substantially reduced.
can be made negligibly small, and since it is not affected by the distributed capacitance C of the high-voltage cable 9, etc., the switching operation frequency of the switch element 3 can be made sufficiently high to several kilohertz or more. Therefore, high power can be boosted by stable high frequency switching,
It becomes possible to obtain the desired high pressure. In addition, by increasing the operating frequency, the change in magnetic flux density in the transformer 5 can be reduced by the above-mentioned increase in frequency, and the size and shape of the iron core of the transformer 5 can be made more compact. It becomes possible to achieve this goal. This makes it possible to downsize the transformer 5 and significantly reduce costs compared to the conventional technology. Furthermore, by increasing the switching frequency, the sampling interval of the device can be narrowed, and the system startup time can be significantly shortened, which is a great effect. Furthermore, the excitation inductance 11 of the transformer 5
Since the excitation current accumulated in the motor is actively utilized and supplied to the load, it also has the advantage of eliminating the need for an expensive snubber circuit, which has been commonly used in the past. It exhibits the characteristic of stable operation regardless of the inductance or distributed capacitance of the high voltage cable 9.

Note that the present invention is not limited to the above embodiments. For example, the number of divisions of the secondary winding in the transformer 5 and the winding ratio may be determined according to specifications. Also, depending on the specifications, diodes 7 ₁ , 7 ₂ to 7
The polarities of _n , ₈₁ , ₈₂ to 8n _-1 may be reversed, and the winding direction of the primary winding ₅₁ may be reversed. Moreover, it goes without saying that the load is not limited to the X-ray tube 10, and a high voltage may be supplied to the load via an appropriate smoothing circuit. In short, the present invention can be implemented with various modifications without departing from the gist thereof.

[Brief explanation of the drawing]

The figures show one embodiment of the present invention, and FIG. 1 is a schematic configuration diagram of the embodiment device, FIGS. 2 a and b are equivalent circuit configuration diagrams according to the operating state of the embodiment device, and FIG. -c are current and voltage waveform diagrams showing the operation of the example device. 1...Input DC power supply, 2...Chiyoke coil, 3...
Switch element, 4... Diode, 5... Transformer, 6
₁ , 6 ₂ - 6 _n ... Capacitor, 7 ₁ , 7 ₂ - 7 _n ... Charging diode, 8 ₁ , 8 _{2 -} 8 _n-1 ... Voltage addition diode, 9 ... High voltage cable, 10 ... X-ray tube ( load), 11...excitation inductance, 12 ₁ , 12 ₂
~12 _n ...Leakage inductance.

Claims (1)

[Claims] 1. A switch element that opens and closes at a predetermined period, connected to an input DC power source via a chain coil,
A transformer having a primary winding connected to the switch element via a diode, and a plurality of charging diodes connected in parallel to the plurality of secondary windings of the transformer with their polarities aligned through capacitors, respectively; A voltage summing diode connected in series with the polarity aligned between these charging diodes, and means for connecting a load between both ends of a series circuit consisting of these charging diodes and the voltage summing diode. A high voltage generator characterized by comprising: