JPS6355308B2 - - 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 has a large converted power, ranging from several kilowatts to several hundred kilowatts, and has a high frequency of power on/off, and the distance to the load is generally long, so long high-voltage cables are used to generate power. It has the special feature of supplying. 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 is a problem in that the reactive power increases and the power supplied to loads such as the X-ray tube decreases, 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 an energy transfer capacitor, and connect a plurality of multi-divided secondary windings of the transformer to the load of a step-up single-ended switch circuit. Connect a charging diode with the same polarity through a capacitor, and connect a voltage adding diode directly between these charging diodes with the same polarity, and connect these diodes in series. By taking power from both ends of the circuit,
The above-mentioned object is effectively achieved by enabling high-speed switching operation with high power and high voltage.

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 the input DC power supply 1 via a choke coil 2.
A step-up single-ended switch circuit is configured. The switch element 3 opens and closes at a switching frequency of, for example, several kilohertz. Note that it is also possible to use other elements such as a thyristor as the switch element 3. The switch circuit 3 is connected to the primary winding 5 of the transformer 5 via a capacitor 4 for power energy transfer.
₁ is connected and serves as a load for the single-ended switch circuit. Further, the secondary side of the transformer 5 has a plurality of multi-divided secondary windings 5 ₂₁ , 5 ₂₂ to 5 _2n
is provided. These secondary windings 5 ₂₁ , 5 ₂₂
5 _2n are set so that the windings thereof are equal to each other and the winding ratio is (1:-n) with respect to the primary winding 5 ₁ . Capacitors 6 ₁ , 6 2 - 6 _n for power transfer are connected to the terminal ends of these secondary windings 5 ₂₁ , 5 ₂₂ - 5 _{2 n} , respectively.
Charging diodes 7 ₁ , 7 ₂ to 7 _n are connected in parallel through these capacitors 6 ₁ , 6 ₂ to 6 _n , respectively, with their polarities aligned. In other words, the diodes 7 ₁ , 7 ₂ to 7 _n have their anodes connected to the secondary winding 5
₂₁ , ₅₂₂ to _52n are connected to the starting ends of each winding. And these charging diodes 7
These diodes 7 1 , 7 are connected between ₁ , _{7 2} and 7 _n .
Voltage adding diodes _{8 1} , 8 ₂ to 8 _n-1 are connected in series with the same polarity as 2 to 7 _n . In other words, each of the diodes 7 ₁ , 7 ₂ to 7
_n , ₈₁ , ₈₂ to _8n-1 have their polarities aligned in one direction and are alternately connected in series to form a series circuit. Both ends of this series circuit, that is, the cathode of the diode ₇₁ and the anode of the diode _7n , are used as high voltage output terminals, and an X-ray tube 10 as a load is connected thereto via the high voltage cable 9. Electricity is now being supplied. Note that the inductance L and capacitance C added to the high voltage cable 9 indicate a stray inductance component and a distributed capacitance component included in the high voltage cable 9, respectively.

Next, the basic operation of the apparatus configured as described above will be explained.

It is assumed that the switch element 3 is conductive with a constant pulse width Ton, opens and closes with a period T (T>Ton), and enters a steady state. In this steady state, a constant current Ii flows through the choke coil 2, a constant voltage Vc 1 flows through the capacitor 4, and a constant voltage Vc ₁ flows through the capacitor 6 ₁ .
It is assumed that a voltage Vc ₂ is stored in each of 6 ₂ to 6 _n . Also, switch element 3 and diode 7
₁ , 7 ₂ to 7 _n , 8 ₁ , 8 ₂ to 8 _n-1 have zero resistance when conducting,
It is assumed that the switch functions as an ideal switch with infinite resistance when shutting off. It is also assumed that the excitation inductance of the transformer 5 has a finite value, and the leakage inductance is negligible in terms of operation. It is also assumed that the apparent resistance value of the X-ray tube 10 is constant.

Now, in this steady state, when the switch element 3 is in the cutoff period T _OFF (=T-Ton), the present device is equivalently shown as shown in FIG. 2a. That is, transformer 5
The sum of the voltage E _L induced by the current Ii stored in the choke coil ₂ and the input voltage Ein of the power supply 1 is applied to the primary winding 5 1 via the power transfer capacitor 4 . This voltage causes the secondary winding 5 ₂₁ ,
A voltage corresponding to the winding polarity is induced in 5 ₂₂ to 5 _2n , and the diodes 7 ₁ and 7 ₂ to 7 _n are positively biased via the secondary side capacitors 6 ₁ and 6 ₂ to 6 _n ,
This makes it conductive. Also, secondary windings 5 ₂₁ , 5 ₂₂
5 _2n , a voltage is induced in a direction that reverse biases the diodes 8 ₁ , 8 ₂ to 8 _n-1 , so these diodes 8 ₁ , 8 ₂ to 8 _n-1 are in a cutoff state. However, now the transformer 5 has an excitation inductance 11 and a leakage inductance 12 ₁ , 12 ₂ to 12
If the boosting function is shown as a block, the equivalent circuit for the cut-off period of the switch element 3 will be as shown in FIG. 2a.

At the start of this period, the current Ii is stored in the choke coil 2, so the voltage E _L proportional to the rate of decrease in the current Ii is the input power supply voltage Ein.
induced with the same polarity as. As a result, the voltage input terminal side of the capacitor 4 is as shown in Figure 3a (Ein+
E _L ) is generated. This voltage acts as a new power source, and a charging current flows through the capacitor 4, part of which flows through the magnetizing inductance 11.
, and the others have leakage inductances of 12 ₁ , 12 ₂ to 12
It flows into capacitors 6 ₁ , 6 ₂ to 6 _n via _n .
As a result, the primary side capacitor 4 and the secondary side capacitors 6 ₁ , 6 ₂ to 6 _n are charged to the illustrated polarity during this cutoff period.

Now, when the switch element 3 becomes conductive, one end of the capacitor 4 is connected to the negative side. As a result, the current flowing into the exciting inductance 11 of the transformer 5 decreases, and the current flowing into the exciting inductance 11 of the transformer 5 decreases.
The polarity of the negative line side terminal of the power supply 1 is reversed to positive. As a result, the voltage induced in the secondary windings 5 ₂₁ , 5 ₂₂ to 5 _2n is directed to positively bias the diodes 8 ₁ , 8 ₂ to 8 _n-1 , and these diodes 8
₁ , 8 ₂ to 8 _n-1 are conductive. At this time, the diodes 7 ₁ , 7 2 - 7 _n are reverse biased by the voltage induced in the secondary windings 5 ₂₁ , 5 ₂₂ - _{5 2 n} ,
As a result, these diodes 7 ₁ , 7 ₂ to 7 _n are cut off. Therefore, the equivalent circuit of the device in this case is as shown in FIG. 2b.

However, in this case, current flows into the choke coil 2 again from the power supply 1, and the current Ii is accumulated as shown in FIG. 3b. The electric charge and current stored in the power transfer capacitor 4 and the excitation inductance 11 are then transferred to the leakage inductance 1.
Secondary windings 5 ₂₁ , 5 ₂₂ via 2 ₁ , 12 ₂ to 12 _n
Voltages e ₁ ′, e ₂ ′ to e _n ′ are induced at ~5 _2n . These voltages e ₁ ′, e ₂ ′ to e _n ′ are combined and added to the charges stored in the respective capacitors 6 ₁ , 6 ₂ to 6 _n , as shown in FIG _. 8 ₂ to 8 _n , these are further superimposed and supplied as a high voltage to the load. Incidentally, FIG. 3d shows the current flowing into the capacitors 6 ₁ , 6 ₂ to 6 _n .

Such operations are alternately repeated at a predetermined period, and the high voltage power generated thereby is supplied to the X-ray tube 10, which is a load.

The basic operation of this device has been explained above.
By the way, the leakage inductance 12 ₁ of the transformer 5 is
When the values of 12 ₂ to 12 _n can no longer be ignored in terms of operation, the leakage inductance 12 ₁ , 12 ₂ to 12 _n increases due to the current flowing into the capacitors 6 ₁ and 6 ₂ to 6 _n.
A voltage drop occurs at capacitor 6, resulting in a voltage drop at
There is a concern that the charging voltage of ₁ , 6 ₂ to 6 _n may become low. This phenomenon is undesirable in this type of power supply device. However, with this device, 2
Since the secondary winding has a multi-divided configuration and is configured to be combined and functioned according to the operating state, the leakage inductances 12 ₁ , 12 ₂ to 12 _n can be made sufficiently small. By the way, compared to the case where the leakage inductance in a conventional step-up transformer with a winding ratio of 1:50 is taken as Leo, the total of the secondary windings 5 ₁ , 5 ₂ to 5 m divided into N as in this device is The leakage inductance L _eN can be reduced in inverse proportion to the former N ² . Therefore, the leakage inductance 1
The values of 2 ₁ , 12 ₂ to 12 _n can be kept as low as necessary and sufficient, and there is no risk of operational problems resulting from this.

Now, the high voltage power taken out from this device is supplied to the X-ray tube 10 via the high voltage cable 9.
Conventionally, the inductance L and distributed capacitance C included in this high-voltage cable 9 have adversely affected the operation of the device. However, in this device, the inductance L and distributed capacitance C have a useful effect on the device and the load. That is, switch element 3
The current flowing through the load during the period when is conducting is
Even if the switch element 3 is shut off, the flow continues into the X-ray tube 10 while its inertia continues. This continuous current flows from the X-ray tube 10 to the inductance L of the cable 9, the diodes 7 ₁ , 7 ₂ to 7 _n , 8 ₁ ,
Reflux through 8 ₂ to 8 _n . Therefore, cable 9
Rather, the inductance L serves to smooth the power supplied to the X-ray tube 10. Furthermore, this return current flows through the series circuit of diodes without acting on the transformer 5 and the capacitors 6 ₁ , 6 ₂ to 6 _n , so that it does not interfere with the operation of the apparatus. Furthermore, the distributed capacitance C of the high voltage cable 9 is equivalent to being inserted in parallel to the capacitors 6 ₁ , 6 ₂ to 6 _n and in parallel to the load of the X-ray tube 10. This also functions to smooth the supplied power. Therefore, although the high voltage cable 9 may act effectively on the device and the load, it does not have any negative effect on the operation of the device. Therefore, as shown in FIG. 4, it is also useful to proactively provide a smoothing circuit consisting of an inductance 13 and a capacitor 14 at the output end of the device.

Furthermore, the excitation inductance 11 of the transformer 5
Also functions usefully for this device. When the switch element 3 is cut off, the current energy stored in the excitation inductance 11 of the transformer 5 decreases, so when the switch element 3 becomes conductive, the induced voltage in the excitation inductance 11 has the same polarity as the charging voltage of the capacitor 4. become. Therefore, the current stored in the excitation coil 11 mainly flows through the closed circuit including the X-ray tube 9. Therefore, there is no need to use a conventional snubber circuit, and the device configuration can be simplified.

As described above through the embodiments, the device of the present invention actively utilizes the inductance that enters the system in series, such as the leakage inductance of the transformer 5 and the inductance of the high-voltage cable, for current smoothing. At the same time, distributed capacitance can also be actively used for smoothing and power transfer. Therefore, power transmission from the input power source to the load can be performed extremely smoothly. Also, regarding the rapid response of the system,
Since the capacitor 4 for power transfer is provided in the middle, it is unavoidable that a delay of one cycle will occur, but the switching frequency is not limited by leakage inductance etc. as in the conventional case, so the operating frequency is set to be sufficiently high. Therefore, it can be sufficiently improved compared to the conventional method. In addition, since high power can be boosted by stable high-frequency switching, changes in the magnetic flux density of the transformer 5 can be reduced.As a result, the shape and dimensions of the iron core can be reduced, and ultimately By downsizing the transformer, it is possible to significantly reduce the cost of the device.
Moreover, since the switching frequency can be increased, the sampling interval of the device can be narrowed,
It is also possible to significantly shorten the rise time. In addition, the basic operation of the device is not hindered by the distributed capacity of the high-voltage cable, etc.
As mentioned above, it does not require a snubber circuit, can be manufactured at low cost, and has great effects such as being very practical.

Note that the present invention is not limited to the above embodiments. For example, the number of divisions and winding ratio of the secondary winding in the transformer 5 may be determined according to specifications. Also, depending on the specifications, diodes 7 ₁ , 7 ₂ to 7
It is also possible to reverse the polarities of _n , 8 ₁ , 8 ₂ to 8 _n-1 or to reverse the winding direction of the winder. Also, equivalently, capacitor 4 and capacitor 6
₁ , 6 ₂ to 6 _n can be made the same, so it is also possible to provide them intensively on one side and omit the other on the actual 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. -d are operational waveform diagrams of the embodiment device, and FIG. 4 is a configuration diagram showing a modification of the present invention. 1...Input DC power supply, 2...Chiyoke coil, 3...
Switch element, 4... Power transfer capacitor, 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, 1
2 ₁ , 12 ₂ ~ 12 _n ... Leakage inductance, 13
...Inductance, 14...Capacitor.

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 has a primary winding connected in parallel to this switch element via a power transfer capacitor, and a plurality of chargers are connected in parallel to a plurality of secondary windings of this transformer with their polarities aligned through capacitors. A load is placed between both ends of the series circuit consisting of the charging diode, the voltage adding diode connected in series with the polarity aligned between these charging diodes, and the charging diode and the voltage adding diode. 1. A high-voltage generator characterized by comprising: means for connecting.