JPS61240858A - Variable voltage power source - Google Patents

Abstract

PURPOSE:To obtain an output of the desired voltage by a small-sized and inexpensive power source by providing a plurality of DC power sources and providing switching elements at the output sides of the power sources. CONSTITUTION:The power line of commercial 3-phase 50Hz, 200V is connected with DC power sources D1-D10 connected in parallel. The power sources D1-D10 are respectively converted by transformers T1-T10 to suitable voltages, rectified by 3-phase full-wave rectifiers B1-B10, and smoothed by capacitors C1-C10 to DCs. Switching elements S1-S10 like GTOs are connected with the output sides of smoothing capacitors C1-C10, and diodes D1-D10 of reverse polarity are connected between the output sides of the elements S1-S10 and the side not connected with the elements of the power sources D1-D10. The DC power source of the desired voltage can be obtained by switching control of the elements S1-S10.

Description

[Detailed description of the invention]

[Technical Field of the Invention] The present invention relates to a variable voltage power supply device, and more particularly to a variable voltage power supply device advantageously used to obtain a pulse power supply for a laser processing machine. [Technical Background of the Invention and Problems Therewith] For example, considering an orthogonal CO2 laser oscillator with a laser output of IKW, a power source of about 2500 V DC and 10 A is generally required. Further, in cutting a metal plate using a laser beam, it is desired that the laser beam can be pulsed in a square waveform with a frequency of about 100 to 5KH2 and a duty ratio of about 10 to 50% between 0NII. In order to obtain such a pulse power supply, a pulse power supply device having a configuration as shown in FIG. 8 is used in the oscillator of a conventional laser processing machine. This conventional power supply is a three-phase 501-
1z, a commercial power supply of 200V is first applied to the thyristor AC voltage regulator 1. In this thyristor AC voltage regulator 1, the conduction angle is changed by phase control, and 50H2, O~2
It is given to the step-up transformer 3 as an AC output of 00V. On the secondary side of step-up transformer 3, AC 50H2, O ~ 2500■
get the output of This AC output is then rectified by a high voltage rectifier 5, and further passed through a smoothing circuit 7 to obtain a DC output of 0 to 2500V. As a continuous power source, it is sufficient to use this direct current output as it is, but if a pulse power source is also required depending on the needs of the laser processing machine, a high voltage switch circuit 9 is further connected to the smoothing circuit 7, and the direct current output is used. ~2500V is pulsed intermittently to obtain a DC pulse output. However, in such conventional variable voltage power supply devices, voltage adjustment is performed by phase control using the thyristor of the thyristor AC voltage regulator, so it is necessary to lower the output voltage at times other than the maximum output, and the commercial power supply is intermittent. Therefore, there is a problem in that the input current from the commercial line becomes a sharp pulse, which increases the loss in the commercial line. In addition, the output of the high-voltage rectifier becomes a pulse-like ripple current with a small duty ratio, and in order to convert this to direct current with less ripple, a smoothing circuit with high ripple removal ability is required, which increases the size of the components and costs. There was such a problem. Furthermore, it is difficult to construct a high-voltage switch circuit, and there is no low-cost switching element suitable for handling a current of 10 A with a withstand voltage of several thousand square meters, which increases the cost of this switch circuit. [Object of the Invention] The present invention has been made in view of such conventional problems, and includes a method for obtaining a desired voltage output by switching and connecting a plurality of DC power supplies using switching elements,
Also, the switching element is turned on. It is possible to obtain a pulse voltage power supply through OFF control, the power supply voltage is made variable without phase control of the commercial line current using a thyristor, etc., the loss in the commercial line is reduced, and a smoothing circuit is installed in the high voltage section. It is an object of the present invention to provide a variable voltage power supply device that does not need to be used, so its components can be made smaller and costs can be lowered. [Structure of the Invention] This invention includes a plurality of DC power supplies, a switching element is inserted in series on the output side of each DC power supply, and the output side of the switching element and the side to which the switching element of the DC power supply is not connected are connected. 1l1111 means for connecting a diode with a polarity opposite to the output voltage of the DC power supply between them, connecting these power supplies in series, and turning on and off the switching element of the power supply with a necessary voltage of DC according to the desired output voltage. A variable voltage power supply device comprising: a variable voltage power supply device, which is configured to change the combination of a plurality of DC*m to obtain a DC power supply of a desired voltage by controlling switching of switching elements by a control means; Switching element ON
By synchronizing , OF FJla with the desired output pulse frequency, it is possible to obtain a pulsed power supply of a desired voltage. [Embodiment of the Invention] FIG. 1 shows a main circuit section of an embodiment of the invention, and FIG. 2 shows an output voltage control section of the main circuit section. In the main circuit section shown in Figure 1, a commercial three-phase 50H
z, the 200V power supply line is connected to each of the DC power supplies D1 to D+o connected in parallel. Each DC power supply section D+
-D+o are respectively converted into appropriate voltages by transformers T1-Too, rectified by three-phase full-wave rectifiers 81-B+o, and smoothed by capacitors C+-Coo to become direct current. Further, switching elements S+-8to such as GTO are connected to the output side of each smoothing capacitor C1-Coo, and the output side of these switching elements 81-S+o and the switching element of each DC power supply section D1-D10 are connected. Diode D1 with reverse polarity between the unconnected side
~D +o is connected. Here, for the DC power supply section D1, a pair of transformers T+
, T+, a pair of full-wave rectifiers B+, B+, and smoothing capacitors C+, C+ are connected in parallel, and a switching element S1 is connected to the output side of one smoothing capacitor C+,
The diode D1 connects the output side of the switching element S1 to the full-wave rectifier B which does not connect the switching element $1.
It is connected to the negative terminal side of 1. In this way, the series connection of the smoothing capacitors C+ and C+ generates 64
A DC voltage of 0V is obtained. Further, the DC power supply section D2 has the same configuration as the DC power supply section D1, and is designed to obtain the same DC voltage of <640V. Then, the DC power supply parts D+ and D2 simultaneously turn on and off the switching elements S+ and S2.
By controlling F, a voltage of 1280V can be obtained as a whole. Furthermore, the DC power supply section D3 has exactly the same configuration as the DC power supply sections D+ and D2, and includes a pair of transformers T3, T3, full-wave rectifiers B3, B3, and smoothing capacitors C3, C3.
The structure is such that a DC voltage of 320V on one side is connected in series to obtain a total DC voltage of 640V. DC power supply section D4 to D+. are 320■ and 1 by transformers T4 to TIO, respectively.
The structure is such that a DC voltage of 60V, 80V, . . . 5V can be obtained. The DC voltage of each DC power supply section D1 to D+o is 5×2n
is set as given by the equation. The principle of the combination of these DC power supply units D1 to D+o will be explained based on FIGS. 5 and 6. DC power supplies E+, E2, and E3 are 4V, 2V, respectively.
It gives a voltage of 1V, and each voltage ratio is in the form of 20. Further, switches St, 32, 83'' are connected in series to each DC power source EIE2; E3, and between the output side of these switches S+, 32, 83 and the negative side of the power source E+, E2, E3, Diodes D+, D2, and D3 are connected to the opposite polarities.When 5cm is required as the output voltage, switches S+ and 83 are turned on at the same time, and the current path is E3-83 as shown in Figure 6. -D2-ET-8+ -Load R-
It becomes E3. In other words, the voltages of the DC power supplies E1 to E3 are in the form of 2n, so if they are selectively turned on by an appropriate combination of switches $1 to S3, any DC voltage output can be obtained every 1V from 0 to 7V. It is possible. Note that the diodes D1 to D3 are connected to the corresponding switches 81 to S.
3 provides a path for the load current when it is OFF,
It also serves to prevent high voltage from being applied to the corresponding switch. For example, considering the case where diode D2 is not present in FIG. 6, 5V is applied to switch S2. This is because, although the S+ 82 should originally be capable of switching 2V, it becomes necessary to use one that can withstand 5V, which is disadvantageous. To obtain a pulse output in this basic circuit, each switch S1. All you have to do is turn on and off S2 and S3 in synchronization. For example, in FIG. 6, if the switch S+, 83 is turned ON and OFF at the timings shown in FIGS. 7(a) to 7(C), a pulse output as shown in FIG. 7(d) can be obtained. Similarly to the basic circuit configuration described above, in the main circuit section shown in FIG. 1, the switching elements 81 to S+o are appropriately combined to turn ON and OFF! If controlling II, o in 5V steps.
DC voltage output can be obtained in stages from V to 2555V. In addition, DC power supply parts D+, D2, D
Currently, the voltage resistance of aluminum electrolytic capacitors and the full wave rectifier are 320V in one channel.
This is because setting it to 0V is more advantageous in terms of cost. Therefore, if capacitor performance is improved and the cost of full-wave rectifiers becomes less of an issue, then 320V can be converted to 640V.
It is also possible to set it to V. Also, the DC power supply section D+, D
2, the switching elements S1 and S2 each have 64
The reason why both circuits control 1280V is that the maximum withstand voltage of the GTO switching elements that are currently available with a current of 10A or less is 1200V. Therefore, if the improvement and development of GTO progresses, 1
A circuit configuration may be used in which a direct current voltage of 1280 V is obtained directly in the channel. Returning to FIG. 2 and explaining the circuit configuration of the control section, this control section is for controlling ON/OFF of each of the switching elements 81 to Sho in the main circuit section shown in FIG. 1. In the control section shown in FIG. 2, the output voltage of the main circuit section shown in FIG. The low-pass filter 13 is a circuit that removes pulse waves and takes out the average value in the pulse mode. The output of the low-pass filter 13 passes through a characteristic compensation circuit 15 that performs proportional-integral processing, etc., and passes through an upper limit comparator 1.
7. Input to lower limit comparator 19. This upper limit comparator 17. As a comparison voltage value of the lower limit comparator 19, a dead band voltage Ed is superimposed on the output voltage command value Er and input. These upper limit comparators 17. The output of the lower limit comparator 19 is applied to a latch circuit 21, and is used as one input of AND gates 23 and 25, respectively. The outputs of these AND gates 23 and 25 are input to the down input terminal and up input terminal of the up/down counter 27, respectively. The up/down counter 27 is a 9-bit binary counter, and has switching elements 81 to S+o in the main circuit section.
This is to determine which of the following is to be turned on. Each of the outputs 01 to Q9 corresponds to the switching elements 81 to S+o in the digits 20 to 28, respectively. Each of these outputs 01~
Q9 serves as one input of AND gates A1 to A9. The outputs of the AND gates A1-A9 are adapted to control gate drivers G1-G9, respectively. Game
Each of the driver G1 to G9 is a switching element 81.
This is for turning on ~S+o. The control circuit section is provided with a mode changeover switch 29 for switching between continuous mode and pulse mode. And this mode changeover switch 29
is the latch circuit 21. It is connected so as to give a synchronizing signal to the AND gates 23 and 25, and also to each of the AND gates A1 to A9. The control operation of the control section having the above configuration will be explained next.

[Pulse mode]

The mode changeover switch 29 is connected to the pulse input, and the pulse signal is sent to the latch circuit 21 and the AND gate 23.2.
5, applied to AND gates A1-A9. The value of the up/down counter 27 is O1, that is, all outputs Q1 to Q9 are O.
In this case, even if a pulse signal is applied to the other input of AND gate AI-A9, no output is generated at that AND gate A+-Aq, and all gate drivers G1 to G9 are turned off.
The switching elements $1 to S+o are all turned OFF, and the power supply output voltage is set to O. Conversely, when the value of the up/down counter 27 is 511, that is, when the outputs Q1 to Q9 are all 1, when a pulse signal is given to the other input of the AND gates A1 to A9, all the AND gates A1 to A9 open and the pulse The signal is passed through and a pulse signal is given to the gate drivers G1 to G9. The gate drivers 01 to G9 turn on the switching elements 81 to S+o at the rising and falling edges of the pulse signal.
A drive signal for OFF is generated and applied to the switching elements, and each of the switching elements 81 to Sho is turned on for a period of the pulse signal width. As a result, the main circuit section provides a pulse output of 2555V, which is the maximum output voltage. When the output voltage of this power supply device is intermediate, the value of the up/down counter 27 is between 1 and 510, that is, the output Q+
AN corresponding to something that is 1 in Q9 (for example, Qi)
When a pulse signal is applied to the other input of the D gate Ai, the AND gate Ai opens to allow the pulse signal to pass, and the pulse signal is applied to the gate driver Gi to turn on the corresponding switching element for a period of the pulse signal width. It is. (Figure 3 (a)) Here, when the feedback value of the output voltage of the main circuit section becomes higher than the sum voltage of the output voltage command value Er and the dead band voltage Ed, it is determined that the output voltage is high, and the output voltage is determined to be high. Control to lower the output voltage is required. Therefore, Figure 3 (
b) As shown in (C), the upper limit comparator 17 generates an output when the feedback voltage becomes higher than Er + Ed, and provides the output to the AND gate 23 via the latch circuit 21. Therefore, as shown in FIG. 4(d), when the pulse signal is 1, the AND gate 23 applies a signal to the countdown input of the up/down/run counter 27 to cause the counter to count down. (
(h) in this figure) When the count state of the up/down counter 27 is incremented by -1, the combination of switching elements triggered accordingly also changes so that the output voltage decreases, thereby adjusting the output voltage. Similarly, when the feedback voltage becomes smaller than Er-Ed, the lower limit comparator 19 generates an output and the AND gate 2
Give to 5. (Figure 3(e), (f)) Therefore, A
The ND gate 25 issues a count-up input signal when the pulse signal is 1, increments the count state of the up-down counter 27 by 1, and changes the combination of switching elements that are triggered so that the output voltage increases. (Same figure (a)
)=(h)) In this way, the output voltage of the main circuit section is compared with the output voltage command value, and the up/down counter 27 performs feedback control so that the output voltage matches the output voltage command value Er. K continuous mode] When the mode selector switch 29 is continuously switched, an input of 1 is given to each of the latch circuit 21, AND gates 23.25, and AND gates A1 to A9. Therefore, AND according to the output value of up-down Karatan 27
Gates A1 to A9 conduct and gate drivers G1 to G9
is driven, and the corresponding switching element 81
~S +o is driven. Therefore, in the main circuit section shown in FIG. 1, the DC output voltage prescribed by the up/down counter 27 is continuously applied. Here, the feedback control operation when the output voltage value of the main circuit section is separated from the output voltage command value Er will be explained based on FIG. 4. When the output voltage from the main circuit section becomes higher than the sum voltage of the output voltage command value Er and the dead band voltage lad, the upper limit comparator 17 generates an output and drives the countdown AND gate 23 to A signal is applied to the countdown input of the counter 27 to cause the up/down counter 27 to count down by one. (Figures (a) and (c)) Therefore, the output value of the up/down counter 27 becomes -1 lower, and the gate drivers 01 to G9 corresponding to that output value are driven, and the switching elements in the combination that give a -1 lower voltage are driven. 81~S
+o will be selectively ovend. When the output voltage of the main circuit section is lower than the dead band voltage Ed with respect to the output voltage command value Er, it is necessary to increase the output voltage. The feedback control operation for this purpose is as follows. That is, when the feedback voltage of the output voltage becomes Er-1:d, the lower limit comparator 19 generates an output, turns on the AND gate 25 for count-up, and provides a signal to the count-up input. Therefore, the combination of outputs 01 to Q9 is changed so that the up/down counter 27 counts up by +1, and the combination of triggering gate drivers G1 to G9 is also changed accordingly, and the switching elements are newly added. is switched in the direction of +1. (Figure (b),
(C)) As described above, in both the pulse mode and the continuous mode, the up/down counter 27 automatically increases or decreases its output until it corresponds to the output voltage command value Er, and the output voltage reaches the specified output voltage value. Feedback control is performed so that Er is within the dead band ±Ed. Note that the output voltage command value Er is set by an appropriate input means. Further, the mode changeover switch 29 can also be changed over by an operator's operation. Further, it is assumed that the pulse input signal is appropriately provided by a pulse generating means. [Effects of the Invention] The present invention includes a plurality of DC power supplies, a switching element is provided in series on the output side of each DC power supply, and a desired output voltage is obtained by switching the switching elements. . Therefore, the pulse degree of the commercial line input current is low, and the loss in the commercial line is reduced, so the capacity of the transformer used can be small, and costs can be reduced. Additionally, since there is no need to use a high-performance smoothing circuit in the high-voltage section, there is also the advantage of miniaturization. Furthermore, the output voltage can be changed digitally by changing the combination of a plurality of switching elements. Another advantage is that it can be easily linked with the C device.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram of the main circuit section of one embodiment of the present invention;
The figure is a circuit diagram of the voltage switching control section of the above embodiment, FIG. 3 is a timing chart explaining the operation of the above embodiment in pulse mode, and FIG. 4 is a timing chart explaining the operation of the above embodiment in continuous mode. 5 and 6 are circuit diagrams for explaining the basic operation of the above embodiment, FIG. 7 is a timing chart for explaining the operation of the basic circuit, and FIG. 8 is a conventional circuit diagram. FIG. 3 is an example circuit diagram. D+~D to...DC power supply section T1~TIO...Transformer 81~Boo...Three-phase full wave rectifier 01~C+o...Smoothing capacitor S+~S to...Switching element D1~D10...
...Diode 11...Voltage divider 13...Low pass filter 15...Characteristic compensation circuit 17...Upper limit comparator 19...
...lower limit comparator 21...latch circuit 23.25.
...AND gate 27...Up/down counter A1-A9...AND gate G1-G9 gate driver

Claims (2)

[Claims] (1) Equipped with multiple DC power supplies, inserting a switching element in series on the output side of each DC power supply, and connecting the DC power supply between the output side of the switching element and the side of the DC power supply to which the switching element is not connected. A variable voltage power supply consisting of a diode connected to the opposite polarity to the output voltage of the power supply, these power supplies connected in series, and a control means for turning on and off the switching element of the DC power supply of the required voltage according to the desired output voltage. Device. (2) The variable voltage power supply device according to claim 1, wherein the ON/OFF operation timing of each switching element is synchronized with a desired output pulse frequency and duty ratio.