JP2011188676A - Power supply - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a power supply which optimizes inverter capacities operated in parallel to be reduced in size when inverters different in capacity are operated in parallel to drive an RLC serial load. <P>SOLUTION: The power supply includes a first inverter and a second inverter different in power capacity connected in parallel to the output of a DC power supply and a first transformer and a second transformer connected to the outputs of each inverter. The ratio between leakage inductance of the first transformer and leakage inductance of the second transformer is set to equal to the ratio between the power capacity of the second inverter and the power capacity of the first inverter. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a switching power supply device for driving an RLC series load used for a power supply device of a carbon dioxide laser processing apparatus.

  2. Description of the Related Art Conventionally, a switching power supply device used for a CO2 laser oscillator using high frequency discharge excitation, for example, used when processing with laser light is configured as follows. It is composed of a converter circuit for controlling power by changing the three-phase alternating current to direct current, a high-frequency inverter circuit for converting the voltage into alternating current, a transformer for efficiently injecting electric power into the discharge load, and boosting the voltage. In such a switching power supply, in order to drive a large-capacity load, a plurality of inverter devices are connected in parallel and the power source power factor is adjusted to reduce the size of the device (for example, Patent Document 1). reference).

  Further, in another conventional switching power supply device, in the inverter device connected in parallel, when a synchronization shift occurs in the switching signal of each inverter, the current flowing through the simulated bus for parallel operation separated from the load is generated. The output voltage of the inverter is controlled so as to be detected and the lateral current flowing between the converters is suppressed (see, for example, Patent Document 2).

JP 2002-374624 A JP-A-5-260665

  When the same switching signal is applied to the switching elements attached to a plurality of inverters for the same RLC series load and the plurality of inverters are operated in parallel, the current flows equally to the plurality of inverters, so the same capacity In some cases, it was difficult to optimize the inverter capacity. For example, when only an inverter with a capacity of 20 kW and an inverter with a capacity of 10 kW are used, when driving an RLC series load with a power of 30 kW, the same switching signal is applied to the switching elements of the two inverters and connected in parallel. Since the same current flows through the inverter, two 20 kW inverters had to be used.

  In the load voltage adjusting device disclosed in Patent Document 1, the power source power factor is adjusted in order to reduce the size of the device. However, in order to adjust the power factor, a sensor such as phase detection is required. Further, a control circuit for controlling the signal from the sensor is required. For this reason, the installation location of the sensor and the installation location of the control circuit are required, which is disadvantageous for downsizing the apparatus.

  Also in Patent Document 2, a simulated bus for parallel operation is required to prevent lateral current in order to balance the shared current of inverters connected in parallel, and a control circuit for controlling this is also necessary. Therefore, when driving an RLC series load, it is disadvantageous for downsizing the device.

  The present invention has been made in order to solve such problems. The object of the present invention is to optimize the inverter capacity for parallel operation when the inverters having different capacities are operated in parallel to drive the RLC series load. It is to realize the miniaturization of.

  In the power supply device according to the present invention, when two inverters having different capacities are operated in parallel, the ratio of the leakage inductance of each transformer connected to each inverter is set to be an inverse ratio of the ratio of the capacity of each inverter. Is.

  In the present invention, the ratio of the capacity of the two inverters and the ratio of the leakage inductance of the transformer connected to each inverter are reversed, so that the ratio of the current flowing through each inverter matches the capacity ratio of each inverter. Each inverter can be used efficiently and optimally.

It is a block diagram of the power supply device which shows Embodiment 1 of this invention. It is a circuit diagram of the power supply device which shows Embodiment 1 of this invention. It is a detailed circuit diagram of the inverter part of the power supply device which shows Embodiment 1 of this invention. It is a circuit diagram at the time of attaching a high-speed diode to the switching element of the inverter part of the power supply device which shows Embodiment 1 of this invention.

Embodiment 1 FIG.
FIG. 1 is a circuit block diagram of a power supply device according to Embodiment 1 for carrying out the present invention. In FIG. 1, the voltage is boosted by the power boost chopper circuit 21 from the DC power supply 2, the boosted power is branched, and the frequency is increased by the two inverters of the first inverter 18 and the second inverter 19. Further, the output of each inverter is boosted by two transformers, a first transformer 9 and a second transformer 10 connected to each inverter, and power is supplied to a load 22 such as a laser oscillator. Here, the first and second inverters 18 and 19 are connected in parallel to the RC load. Although FIG. 1 shows the step-up chopper circuit 21 that boosts the voltage at the input of the inverter circuit, a step-down chopper circuit that steps down the input voltage or a step-up / step-down chopper circuit that steps up or down the voltage may be used. If the input voltage can be used as it is, the chopper circuit may be omitted. Further, only the inverter circuits are connected in parallel, but the chopper circuits may be parallel if they are controlled so that the output voltages of the respective chopper circuits are equal.

  FIG. 2 is a circuit diagram illustrating the circuit block diagram of FIG. 1 in more detail. As shown in FIG. 2, the configuration of the present switching power supply is configured such that the output of the step-up chopper circuit 21 composed of the reactor 1, the diode 16, the smoothing capacitor 4, and the switching element 3 is branched into two, and each output is set to the first output. The inverter circuit 18 and the second inverter circuit 19 are connected. The first inverter circuit includes four switching elements 51, 52, 53, and 54. Switching elements 51 and 52 are turned on and switched by on / off signals S1, S2, S3, and S4 from the control circuit 17. The input power is increased in frequency by alternately switching between a state in which the elements 53 and 54 are turned off and a state in which the switching elements 51 and 52 are turned off and the switching elements 53 and 54 are turned on.

  On the other hand, the second inverter circuit 19 is composed of four switching elements 81, 82, 83, 84, and the switching elements 81, 82 are turned on by on / off signals S 1, S 2, S 3, S 4 from the control circuit 17. The input power is increased in frequency by alternately switching between a state in which the switching elements 83 and 84 are turned off and a state in which the switching elements 81 and 82 are turned off and the switching elements 83 and 84 are turned on. In FIG. 2, each of the switching elements 51 to 54 and 81 to 84 is described as a single switching element, but actually, each switching element is composed of a plurality of switching elements as will be described later.

  Furthermore, the outputs of the first inverter circuit 18 and the second inverter circuit 19 are connected to the first transformer 9 and the second transformer 10 having different leakage inductances, respectively, and the secondary side of each transformer is connected. Connected to the load. For example, when the load 22 is a carbon dioxide laser oscillator, the discharge part can be regarded as a resistance and the electrode part can be regarded as a capacitance. Therefore, the output of the inverter is regarded as an RLC series load in which a leakage inductance, a resistance 6 and a capacitance 7 are connected in series. The inverter is driving this RLC load.

  The output voltage of the step-up chopper circuit is divided by a resistor (not shown) and fed back to the control circuit 17 as a chopper output feedback signal 13 through an insulation amplifier (not shown). The switching signal 14 of the switching element 3 of the boosting chopper circuit is generated by taking the difference between the chopper command voltage, which is a set voltage of power supplied to the inverter circuit, and the chopper feedback signal 13. The switching signal 13 determines the time when the switching element 3 is turned on and the time when the switching element 3 is turned off. By performing PWM control, the output of the step-up chopper circuit is kept stable.

  On the other hand, the first and second inverter circuits 18 and 19 detect the current flowing in the load 22 after the first transformer 9 and the second transformer 10 are connected on the secondary side by the current sensor 11 and control the current thereby. Is done. The signal output as a voltage signal by the current sensor 11 is fed back to the control circuit 17 as a current feedback signal 12. Similar to the control method of the chopper circuit, by taking the difference between the current feedback signal 12 and the current command value that is the current value of the power applied to the load 22, the switching elements 51 to 54 and 81 to 84 are turned on. The time to turn off is decided. By such a control method, the control circuit 17 generates the switching signals S1 to S4 of the inverter circuits 18 and 19, and the first inverter circuit 18 switching elements 51 to 54 and the second inverter circuit 19 switching element 81. 84 are driven. As a result, the current flowing through the load 22 is controlled.

  FIG. 3 is a circuit diagram showing the details of the first inverter circuit 18 and the second inverter circuit 19 in FIG. Each switch 51 to 54 of the first inverter circuit 18 has six switching elements connected in parallel, and each switch 81 to 84 of the second inverter circuit 19 has three switching elements connected in parallel. Inverters with different capacities are connected in parallel so that the number of switching elements is 2: 1. The reactor 15 is a cross-current preventing reactor that is attached to prevent current from being biased to one inverter when a synchronization shift occurs in the switches of the switching elements of the inverters 18 and 19 connected in parallel.

  Here, when the capacity of each switching element is the same, the capacity of the inverter is determined by the number of switching elements connected in parallel. That is, the capacity of the first inverter is twice that of the second inverter. A first transformer 9 and a second transformer 10 having a leakage inductance of 1: 2 are connected to the outputs of the inverters 18 and 19, respectively. That is, they are connected so as to be opposite to the capacity ratio. As a result, the shunt balance of the current flowing through the first inverter circuit 18 and the second inverter circuit 19 is determined to be 2: 1 by the leakage inductance of the two transformers 9 and 10. That is, the ratio of currents flowing through the first inverter circuit 18 and the second inverter circuit 19 matches the capacity ratio of each inverter circuit, and each inverter circuit can be used efficiently and optimally.

  In addition, the leakage inductance in this invention shows the value of the inductance measured from the side which does not short-circuit when the primary winding or secondary winding of a high frequency transformer is short-circuited. In this case, the measured value on the primary side is different from the measured value on the secondary side, but it may be measured on the primary side or the secondary side, and the ratio of the leakage inductance of the two transformers may be calculated. When making comparisons, you should match either one. The capacity of the inverter in the present invention indicates power capacity. For example, when the input voltage of the inverters connected in parallel is the same, the capacity of the inverter is determined by the magnitude of the current. Therefore, when switching elements having the same capacity are used in parallel connection, it is proportional to the number of switching elements. Inverter capacity changes.

  In the above embodiment, since the switching elements 51 to 54 for the first inverter 18 and the switching elements 81 to 84 for the second inverter 19 use the same switching element, the use of the switching element of the inverter is used. The ratio of the numbers has been described as the ratio of the capacity of the inverter as it is, but of course, switching elements having different power capacities may be used. In this case, the ratio of the leakage inductance of the transformer may be determined by the ratio of the entire capacity regardless of the number of switching elements used.

  Moreover, although the case where the inverter capacity is 1: 2 has been described, the present invention can be applied to inverter parallel operation with any capacity as long as the leakage inductance is appropriately set. For example, if the capacity ratio of the first inverter 18 and the second inverter 19 is M: N, it is connected to the first transformer 9 and the second inverter 19 connected to the first inverter 18. If the ratio of the leakage inductance of the second transformer 10 is N: M, the current ratio flowing through each inverter becomes M: N, and the current ratio matches the capacity ratio of each inverter circuit, so that each inverter circuit is efficiently optimized. Can be used for

  In this embodiment, the external high-speed diode 20 is not used for each switch of the inverter. However, as shown in FIG. 4, the number of elements is changed when the high-speed diode 20 is used together as necessary. This embodiment is not necessary, and this embodiment can be applied as it is. The high-speed diode 20 is provided to flow a reflux current and a regenerative current in order to prevent a problem that the current flow path is interrupted and the voltage jumps when all the switches are turned off by an inductance load or the like. Yes.

  The present invention can arbitrarily determine the power capacity of inverters connected in parallel when the inverters are operated in parallel according to the present embodiment. Furthermore, when the number of switching elements used determines the capacity of the inverter as in this embodiment, the greater the number of switching elements used, the larger the inverter capacity and the larger the outer shape. Conversely, the smaller the number of switching elements used, the smaller the inverter capacity and the smaller the outer shape. Therefore, when the inverters are operated in parallel and the size of the power panel on which the inverter is installed is determined, the inverter capacity can be determined from the outer size, so that the installation space can be used effectively. Further, since a control circuit or the like for diverting currents flowing through inverters having different capacities is unnecessary, the apparatus can be reduced in size.

Embodiment 2. FIG.
By the way, the shunt balance to the inverters connected in parallel is determined by the ratio of the leakage inductance. However, since the RC load is connected to the secondary side of the transformer, the LLC load L has changed as viewed from the inverter output. It becomes. Therefore, when the transformers having different leakage inductances are connected in parallel as compared to a circuit in which the same leakage inductances are connected in parallel, the current peak flowing through the load changes. When the load is a laser oscillator, the laser output changes when the current peak flowing through the laser oscillator changes. Therefore, it is necessary to adjust the current peak flowing through the load in order to obtain a desired laser output. In other loads, it may be necessary to adjust the current peak.

In the present embodiment, a method for adjusting the current peak flowing through the load by changing the switching frequency of the inverter will be described. For example, when the inverters having the same number of switching elements are operated in parallel, if the leakage inductance of each transformer is L, the combined inductance is L / 2. On the other hand, when the inverter having the number of switching elements doubled by one inverter is operated in parallel, the transformer doubles one leakage inductance based on the first embodiment, so that the combined inductance of the transformer is L and It becomes 2L parallel and becomes 2L / 3. That is, the inductance viewed from the load is (2L / 3) / (L / 2), which is 4/3 times. If an attempt is made to obtain the same current peak as when the number of switching elements of the RLC series resonance circuit is 1: 1, the resonance frequency of the RLC series resonance circuit is ω ² LC = 1 (ω = 2πf). What is necessary is just to make it 3/4) times. The switching frequency is set by the control circuit 17, and can be changed to an arbitrary frequency by changing the resistance value with a variable resistor, for example.

  In the above description, the case where the inverter capacity is 1: 2 has been described. Of course, the inverter capacity can be applied to any capacity in parallel operation by appropriately changing the switching frequency. For example, when a high-frequency transformer having a leakage inductance of N times is connected in parallel, the capacity of an inverter connected to the transformer having a leakage inductance of N times may be 1 / N compared to the other inverter. At this time, in order to make the inverter current peak the same as when the inverters of the same capacity are connected in parallel, the switching frequency of the inverter may be √ ((1 + N) / 2N). As another example, when the ratio of the capacities of the two inverters is M: N, the leakage inductance of one transformer is multiplied by N to make the ratio of the leakage inductance of the transformer connected to each inverter N: M, and the other When the transformer has a leakage inductance of M times, the leakage inductance is 2NM / M + N times that of a transformer having the same leakage inductance connected in parallel. At this time, in order to make the current peak of the inverter the same as when an inverter of the same capacity is connected in parallel, the switching frequency of the inverter may be multiplied by √ ((M + N) / 2MN).

  According to the present embodiment, even if the ratio of the leakage inductance of the two transformers is changed as in the first embodiment, it is possible to easily prevent the current peak from changing by appropriately setting the switching frequency of the inverter. be able to.

2 DC power supply 9 1st transformer 10 2nd transformer 17 Control circuit 18 1st inverter 19 2nd inverter 22 Load 51-54 1st inverter switching element 81-84 2nd inverter switching element S1 S4 Switching signal for inverter

Claims (3)

DC power supply,
A first inverter and a second inverter having different power capacities connected in parallel to the output of the DC power supply;
A first transformer connected to the output of the first inverter;
A second transformer connected to the output of the second inverter;
A power supply device for driving an RC load by the outputs of the first and second transformers,
The power supply apparatus according to claim 1, wherein a ratio of a leakage inductance of the first transformer to the second leakage inductance is equal to a ratio of a power capacity of the second inverter to a power capacity of the first inverter. 2. The control circuit according to claim 1, further comprising a control circuit that adjusts a switching frequency of the first and second inverters in order to adjust a peak current value in outputs of the first and second transformers. Power supply. The control circuit includes:
Compared to the leakage inductance of the transformer when the power capacities of the first and second inverters are equal, the ratio of the power capacities of the first inverter and the second inverter is M: N, and this When the leakage inductance of the first transformer is N times and the leakage inductance of the second transformer is M times according to the ratio, the switching frequency of the first and second inverters is changed to the original switching frequency. 3. The power supply device according to claim 2, wherein the switching frequency is adjusted so as to be √ ((M + N) / 2MN) times.

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