JP2008263755A - Switching power supply - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To increase the size and capacity of a switching power supply. <P>SOLUTION: In the switching power supply, there are a diode D11, a switching element S51, and a decoupling capacitor C1 for composing a chopper circuit, and four switching elements S11, S21, S31, S41 for composing a high-frequency invertor circuit on the same multilayer printed board 1. A control signal by a control substrate 71 gives a signal to a chopper signal generation circuit 72 and an invertor signal generation circuit 73 to drive respective switching elements S11, S21, S31, S41, S51. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a switching power supply device used for a power supply device of a laser processing apparatus.

  2. Description of the Related Art Conventionally, for example, a configuration of a switching power supply device used in a CO2 laser oscillator by high frequency discharge excitation used when performing laser processing includes a chopper circuit for controlling electric power and a high frequency inverter circuit for converting voltage to high frequency. And a matching circuit or a step-up transformer for efficiently injecting power into the discharge load and boosting the voltage. (For example, see Patent Document 1)

  For the chopper circuit and the high-frequency inverter circuit of the switching power supply device having such a configuration, semiconductor elements that can be switched at a high frequency such as bipolar transistors, MOSFETs, or IGBTs are used, and in some cases, a large number of these semiconductor elements are used in parallel. There is a case. In order to realize a stable circuit operation by using a plurality of such semiconductor elements and to construct a small and inexpensive circuit, structural ingenuity is required.

  A conventional switching power supply device includes, for example, a bridge connection of four sets of semiconductor switching elements, a DC side wiring conductor connected to each of the semiconductor switching elements, an insulator interposed between the AC side wiring conductors, and a semiconductor Wiring is close to each other except for the switching element connecting portion. With this configuration, the stray inductance of the wiring is suppressed as much as possible to suppress the generation of a surge voltage, and a small and highly efficient power source without a snubber circuit is realized. (For example, see Patent Document 2)

  In another conventional switching power supply device, for example, a MOSFET and a decoupling capacitor are arranged on a multilayer printed board. As a result, the physical space of the main circuit can be reduced, and the area of the current loop can be reduced, so that the stray inductance is reduced, the occurrence of excessive voltage and abnormal oscillation due to the stray inductance is eliminated, and high-speed switching is enabled. In addition, each inverter in the main circuit is composed of a small number of power MOSFETs connected in parallel and is operated in synchronism, and the output transformer secondary sides of these inverters are connected in series. Output end. (For example, see Patent Document 3)

JP-A-9-232658 JP-A 63-157777 Japanese Patent Laid-Open No. 7-231669

  In the laser power supply device disclosed in Patent Document 1, a chopper circuit may be required before the inverter in order to adjust power. When a large-capacity power supply is simply configured with the power supply of this configuration, a large number of parallel switching elements are required. As the number of parallel switching elements increases, there arises a problem of switching variation due to a problem in arrangement of the switching elements.

  Further, in the configuration of the inverter device disclosed in Patent Document 2, two double-sided printed boards are used on the upper and lower sides to form one switching power supply, which is disadvantageous for circuit miniaturization.

  Further, the inverter device disclosed in Patent Document 3 is configured such that the wiring of the main circuit is configured using a multilayer printed wiring board. In this configuration, four switching elements for configuring one high-frequency inverter circuit are installed in the vicinity, so there is no occurrence of excessive voltage or abnormal oscillation due to stray inductance, and high-speed switching is stable. However, it is disadvantageous for downsizing the apparatus when the capacity of the power supply apparatus is increased.

  In addition, a number of high-frequency inverter circuits each consisting of a small number of power MOSFETs in each branch of the main circuit are connected in parallel and coupled on the output side, each using an output transformer and connected in series on the secondary side of the transformer. Therefore, it is disadvantageous for downsizing the apparatus when increasing the power output capacity.

  The techniques disclosed in Patent Document 2 and Patent Document 3 relate to the configuration of a high-frequency inverter circuit, and do not mention the configuration of a power supply device that requires a chopper circuit in the previous stage of the high-frequency inverter circuit.

  Therefore, the present invention has been made to solve the above-described problems, and an object of the present invention is to realize miniaturization of a switching power supply device.

  According to another aspect of the present invention, there is provided a switching power supply comprising a chopper circuit that adjusts a DC voltage to a desired DC output voltage, and an inverter circuit that converts the DC output voltage of the chopper circuit into a high-frequency voltage. And the inverter circuit are arranged on the same printed circuit board.

  A switching power supply according to another invention is a switching power supply comprising a chopper circuit that adjusts a DC voltage to a desired DC output voltage, and an inverter circuit that converts the DC output voltage of the chopper circuit into a high-frequency voltage. The step-up chopper circuit and the inverter circuit are arranged on the same printed circuit board, and each circuit element is collectively cooled by cooling fins.

  According to another aspect of the present invention, there is provided a switching power supply comprising an inverter circuit for converting a DC voltage into a high frequency voltage, wherein the inverter circuit includes a plurality of decoupling capacitors connected in parallel, and the decoupling The overcurrent of the inverter circuit is detected by detecting at least one current of the capacitor.

  According to the present invention, the chopper circuit that adjusts the DC voltage to a desired voltage and the inverter circuit that converts the DC output voltage of the chopper circuit to a high voltage are arranged on the same multilayer printed circuit board, thereby causing stray inductance. Occurrence of excessive voltage, abnormal oscillation, etc. is eliminated, high-speed switching is stabilized, and the power supply device can be reduced in size.

  Further, the power supply device can be downsized by collectively cooling each circuit element with the cooling fins.

  The inverter circuit for converting a DC voltage into a high-frequency voltage includes a plurality of decoupling capacitors connected in parallel, and an overcurrent of the inverter circuit is detected by detecting a current of at least one of the decoupling capacitors. Therefore, the overcurrent detection circuit can be downsized. Therefore, the power supply device can be reduced in size.

  Exemplary embodiments of a switching power supply according to the present invention will be described below with reference to the accompanying drawings.

Embodiment 1 FIG.
FIG. 1 shows the structure of a switching power supply device having a step-up chopper circuit and a high frequency inverter circuit according to Embodiment 1 of the present invention, and FIG. 2 shows a circuit diagram thereof. Although FIG. 2 particularly shows a boost chopper circuit that boosts the input voltage, 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 input voltage may be used.

  As shown in FIG. 1, in the switching power supply device, the diode D11, the switching element S51 and the decoupling capacitor C1 constituting the chopper circuit, and the four switching elements S11, S21, S31, S41 constituting the high frequency inverter circuit are the same. The structure is arranged on the multilayer printed circuit board 1. Further, as shown in FIG. 2, the control signal from the control circuit 71 gives a signal to the chopper signal generation circuit 72 and the inverter signal generation circuit 73, and the switching elements S11, S21, S31, S41 and S51 are driven. Note that the control circuit 71, the chopper signal generation circuit 72, and the inverter signal generation circuit 73 may be arranged on the multilayer printed circuit board 1, but may be configured by separate boards. In FIG. 2, an output feedback signal for output control, an overvoltage detection circuit for a chopper circuit, and the like are omitted, but these circuits are appropriately mounted.

  Input power supply lines LA1 and LB1 indicate connection lines connecting the positive side potential and the ground side potential, respectively, and lines LC1 and LD1 indicate output lines of the inverter circuit. For these connection lines, for example, cable lines or copper bus bars are used.

  As shown in FIG. 3, the multilayer printed circuit board 1 has a laminated structure in which an insulating member 20 is sandwiched between copper foil patterns 21 and 22, 22 and 23, and 23 and 24, and input power lines LA1 and LB1. The inverter power supply patterns X and Y and the inverter output wirings LC1 and LD1 are provided in the pattern of each layer. In particular, it is desirable that the inverter power supply patterns X and Y are patterned in the upper and lower layers, and the patterns are configured so that the currents of the inverter power supply patterns X and Y flow in the upper and lower layer folding. With such a structure, the area of the current loop of the main circuit can be reduced, so that surge voltage and abnormal oscillation to the switching element due to wiring inductance can be suppressed.

  The decoupling capacitor C1 is a capacitor for reducing a surge voltage generated at both ends of the bridge composed of the switching elements S11, S21, S31, and S41 due to the influence of the wiring inductance, and a film capacitor having a good frequency characteristic is used. Further, the decoupling capacitor C1 also functions as an output capacitor of the chopper circuit in terms of circuit configuration, and may be configured to connect a large number of capacitors in parallel in order to increase the capacitor capacity. In this case, it is desirable that the decoupling capacitors C1 are arranged in a distributed manner on the inverter power supply patterns X and Y. By arranging the decoupling capacitors C1 in a distributed manner, the effect of suppressing the surge voltage generated at both ends of the MOSFET bridge due to the wiring inductance is achieved. It becomes possible to obtain more.

  In addition, the inverter circuit overcurrent detection CT60 may be installed through the inverter power supply pattern X or Y, but the current flowing in any one of the decoupling capacitors C1 arranged in a distributed manner is measured and the detection target is detected. Alternatively, the signal of the decoupling capacitor C1 may be determined by the overcurrent detection circuit 70 and returned to the control circuit 71. When the inverter circuit arm is short-circuited or when an inverter overcurrent occurs due to load abnormality, the current of the decoupling capacitor C1 connected in parallel flows several times to several tens of times that during normal operation. The inverter overcurrent can be determined by detection.

  With such a detection method, since the patterned inverter power supply pattern X or Y is not pulled out once for passing through the overcurrent detection CT 60, surge voltage generated at both ends of the inverter bridge due to wiring inductance is suppressed. It is possible to obtain more effects. Further, since the current of one decoupling capacitor C1 is smaller than the current of the inverter power supply pattern X or Y, the overcurrent detection CT60 can be reduced in size, and the entire power supply apparatus can be reduced in size.

  As the switching elements S11, S21, S31, S41, and S51, a semiconductor element suitable for high-frequency switching, for example, a bipolar transistor, a MOSFET, or an IGBT is used. In particular, when switching at a frequency of 50 kHz or higher is required, it is desirable to use a MOSFET suitable for high-speed switching. As the chopper diode D11, it is desirable to use a fast recovery diode having excellent recovery characteristics or a Schottky barrier diode without diode recovery. By using such a high-speed switching element, it is possible to reduce element heat generation and avoid element breakage, and to provide a stable and compact power supply device despite high-speed switching.

  The reactor L1 used for the chopper circuit is not mounted on the multilayer printed circuit board 1 in FIG. 1, but may be mounted on the multilayer printed circuit board 1 when the reactor L1 is relatively small and light. If it carries out like this, the whole circuit will be integrated on the multilayer printed circuit board 1, and a power supply can be reduced more.

  In this embodiment, a snubber circuit, an external high-speed diode of an inverter, and the like are not used. However, these may be used in combination as necessary. By mounting any of the circuits on the same multilayer printed circuit board 1, it is possible to configure a power supply that operates stably and is downsized.

Embodiment 2. FIG.
4 (a) and 4 (b) show the structure of a switching power supply apparatus according to Embodiment 2 of the present invention, where (a) is a perspective view and (b) is a front view. In the present embodiment, the basic configuration is the same as that of the first embodiment, and the same reference numerals are used for the same parts.

  In the first embodiment, the case where each element constituting the chopper circuit and the high-frequency inverter circuit is one is shown. However, when the capacity of the power source is increased, a plurality of elements are connected in parallel. In particular, when the loss of the constituent elements is large and the heat generation is large, a configuration in which the elements are collectively cooled using a large cooling fin is desirable.

  In a semiconductor element, the on-resistance or on-voltage when the element is energized depends on the junction temperature of the element. For example, the on-resistance of a MOSFET often has a positive temperature coefficient, and the on-voltage of a diode often has a negative temperature coefficient. For this reason, in order to make the junction temperature of each element uniform and to make the on-resistance or on-voltage when energized substantially the same, it is more preferable to drive the same elements connected in parallel at the same temperature. Therefore, by cooling a large number of elements connected in parallel on the same cooling fin, the junction temperature of the elements is made substantially uniform between the same elements, and current variations flowing through the elements are suppressed. This prevents damage to the element and shortens the service life, and realizes a power supply that operates stably.

  4A and 4B, the diode D11, the switching element S51 and the decoupling capacitor C1 that constitute the chopper circuit, and the four switching elements S11, S21, S31, and S41 that constitute the high-frequency inverter circuit include the cooling fin 10 A screw 81 is attached through an insulating sheet 100. The legs of each element are bent upward, and the legs are soldered and connected to the same multilayer printed circuit board 1. The decoupling capacitor C1 is arranged in a distributed manner on the inverter power supply patterns X and Y as in the first embodiment, and obtains the effect of suppressing the surge voltage. With such a configuration, the area of the current loop formed by the inverter power supply patterns X and Y is reduced as in the first embodiment, so that the stray inductance is reduced and the occurrence of an overvoltage, an abnormality, etc. due to the stray inductance is eliminated. Further, since the current flowing through each element when the switching elements S11, S21, S31, and S41 are connected in parallel is equalized, it is possible to prevent abnormal heat generation and damage to the elements due to loss bias of the switching elements S11, S21, S31, and S41. This makes it possible to easily increase the capacity of the power supply.

  The cooling fin 10 may be of a natural air cooling type or a forced air cooling type, but a water cooling type cooling fin may be used in order to further enhance the cooling effect. If a water-cooling type cooling fin is used, it becomes possible to further reduce the size of the entire power supply as the cooling fin becomes smaller. In addition, it is desirable to select those cooling fins made of copper or aluminum having good heat conduction characteristics.

  In particular, in FIG. 4, the element is mounted using a single large cooling fin, but for example, as shown in FIGS. 5A and 5B, the perspective view and the front view thereof, S 11 and S 41 of the inverter arm. Each of the pair of cooling fins 11, 12 and 13 is used for the group of S21 and S31, and the group of the chopper switching element S51 and the diode D11. It is good also as a structure which stops with the screw 81 from a side part. In particular, the combination of inverter arms is not a problem, and if multiple elements connected in parallel are mounted on the same cooling fin, each element is driven at approximately the same temperature, so the current flowing through each element Variation is suppressed. Also, with such a configuration, the element mounting area is reduced, so that the multilayer printed board 1 can be used effectively, and the entire power supply can be further reduced in size. Furthermore, it is possible to replace parts for each element, which makes it easy to manufacture a circuit and improves productivity.

  Furthermore, as shown in FIGS. 6A and 6B, a perspective view and a front view thereof, the element and the cooling fins 11, 12 and 13 may be attached from the back surface of the multilayer printed board 1. With such a configuration, the same effects as in FIG. 5 can be obtained, and the surface of the multilayer printed circuit board 1 can be used more effectively. Therefore, the multilayer printed circuit board 1 can be made smaller, and the entire power supply Can be miniaturized.

  The cooling fins 11, 12 and 13 may have a horizontally long rectangular parallelepiped shape, but may have a horizontally long trapezoidal column shape or a triangular prism shape as shown in FIG. When a cooling fin having such a shape is used, it is possible to attach and detach elements from an oblique direction, so that the tool does not interfere with the cooling fin during manufacture, making circuit manufacture easier and cooling adjacent to each other. Since the space between the fins can be reduced to the maximum, the area of the multilayer printed circuit board 1 can be reduced, and the power supply can be further downsized.

  When attaching each element to the cooling fins 11, 12, and 13, the individual elements may be individually tightened by the screws 81, but the installation becomes complicated when the number of parallel elements increases. Therefore, as shown in FIG. 8, two elements arranged back to back via the cooling fins 11, 12, or 13 are fastened together with a long screw 82 penetrating the cooling fins 11, 12, and 13 and a nut 83. It is also good. In this case, as compared with the case where each element is fastened by the individual screw 81, the trouble of screwing is eliminated, so that the circuit can be easily manufactured when the power supply capacity is increased, and the productivity is improved. Further, as shown in FIG. 9, the cooling fin 11 is collectively attached so as to press down a plurality of elements by an arcuate plate 31 having elasticity and a cushion material 32 sandwiched between the elements and the arcuate plate 31. It is good also as a structure to attach.

  Further, as shown in FIGS. 10 (a) and 10 (b), a perspective view and a front view thereof, each element is pressed by an elastic spring-shaped metal fitting 41, and a plurality of elements are screwed together by a screw 42. It is good also as composition to do. In either case, the trouble of screwing individual elements is eliminated, so that the circuit can be easily manufactured when the power supply capacity is increased, and the productivity is improved.

  Although FIGS. 5 to 8 show three cooling fins 11, 12, and 13 as an example, the number of cooling fins is arbitrarily selected according to the circuit scale and the cooling capacity of the cooling fins.

  Further, in this embodiment, an external high-speed diode or the like of the inverter is not used, but it may be configured so that it is used on the same cooling fin as needed. By using the same multilayer printed circuit board and cooling the elements at once with cooling fins, it is possible to configure a power supply that operates stably and is downsized.

Embodiment 3 FIG.
FIG. 11 shows a circuit diagram of a switching power supply device according to Embodiment 3 of the present invention. The basic configuration and structure are the same as those of the second embodiment, and the same reference numerals are used for the same parts.

  In the second embodiment, the example in which the capacity of the power source is increased by using the cooling fins is shown. However, if you want to further increase the capacity of the power supply and increase the number of parallel elements, the drive circuit of the switching element becomes more complex, and a difference occurs in the current flowing through the switching element. May occur.

  Therefore, in this embodiment, the switching elements of the main circuit are configured with a small number, a plurality of main circuits having the same configuration in which each switching element operates in synchronization are connected in parallel, and both ends 51 and 52 are used as output terminals. is there. With such a configuration, the output voltage is the same in each inverter circuit, but the output current is the sum of the inverter circuits, and the required power can be obtained.

In FIG. 11, reactors L21 and L22 are reactors for correcting current bias due to switching variations of the switching elements S51 and S52 of the chopper circuit in parallel connection.
For example, when the control signal of the switching elements S51 and S52 is out of synchronization, and the switching start of the switching element S51 is earlier than the switching element S52, the synchronization deviation time of the switching elements S51 and S52 is t, the chopper circuit output is V, and the reactor L21. When the value of L22 is L and the switch current value when equally divided is io (= I / 2, I is the reactor L1 current), the current i (≦ I) that flows through the switching element S51 when the synchronization shift occurs is ,
i = Vt / L + io
It is represented by Without the reactors L21 and L22, all the current of the reactor L1 flows through the switching element S51. Therefore, the switching elements S51 and S52 require switching elements corresponding to the current capacity compensated for the synchronization shift, This is disadvantageous for circuit miniaturization and cost reduction.

By attaching the reactors L21 and L22, it is possible to reduce the current bias when the synchronization shift occurs, and the circuit can be reduced in size and cost. The greater the current and reactor L21, L22 values, the greater the effect of bias suppression. For this reason, it is desirable that the reactor value is large, but if the reactor value is large, the volume and weight increase. Therefore, the values of reactors L21 and L22 are selected from the current capacities and losses of switching elements S51 and S52 and diodes D11 and D12.
Reactors L21 and L22 are necessary when the synchronization deviation between switching elements S51 and S52 of each substrate is large, but are not necessary when there is almost no synchronization deviation and current deviation is allowed in each element. It is selected depending on the current flowing through the element and the loss.

  FIG. 12 shows a structural example of the switching power supply device. As in the second embodiment, it is desirable that the elements are collectively cooled using the large cooling fins 11, 12, and 13, and a plurality of elements connected in parallel are cooled on the same cooling fin, thereby the same element. The case temperature of the elements is made almost uniform, and variations in the current flowing through each element are suppressed. This prevents damage to the element and shortens the service life, and realizes a power supply that operates stably. For example, cable lines or copper bus bars are used for the output wirings LC1, LD1 and LC2, LD2 of the respective inverter circuits.

  FIG. 13 shows a structure in which the respective substrates are connected to each other on the back side, and outputs are taken out from the central portion by output wirings LC1, LD1 and LC2, LD2 made of cable wires or copper bus bars. With such a structure, the installation area of the power supply can be reduced. For example, the height direction is allowed, but even when it is desired to make the installation area as small as possible, the power supply can be easily reduced in size and capacity. be able to. Note that it is possible to further increase the capacity by using, for example, four substrates by combining the structures shown in FIGS.

  The switching power supply device according to the present invention can be used for a laser power supply device of a CO2 laser oscillator by high frequency discharge excitation used when performing laser processing.

It is a block diagram of the power supply device by Embodiment 1 of this invention. It is a circuit diagram of the power supply device by Embodiment 1 of this invention. It is explanatory drawing of the multilayer substrate of the power supply device by Embodiment 1 of this invention. It is a block diagram of the power supply device by Embodiment 2 of this invention. It is a block diagram of the power supply device by Embodiment 2 of this invention. It is a block diagram of the power supply device by Embodiment 2 of this invention. It is a structural diagram of the cooling fin of the power supply device by Embodiment 2 of this invention. It is a structural diagram of the cooling fin of the power supply device by Embodiment 2 of this invention. It is an element attachment figure of the power supply device by Embodiment 2 of this invention. It is an element attachment figure of the power supply device by Embodiment 2 of this invention. It is a circuit diagram of the power supply device by Embodiment 3 of this invention. It is a block diagram of the power supply device by Embodiment 3 of this invention. It is a block diagram of the power supply device by Embodiment 3 of this invention.

Explanation of symbols

1, 2 Multi-layer printed circuit board 10-13 Cooling fin 20 Insulating member 21-23 Copper foil pattern 31 Arched plate 32 Cushion material 33, 42, 81 Screw 41 Metal fitting 51, 52 Output terminal 60 CT
70 Overcurrent detection circuit 71 Control circuit 72 Chopper signal generation circuit 73 Inverter signal generation circuit 82 Long screw 83 Nut 100 Insulation sheet E1 Input voltage LA1, LA2, LB1, LB2 Power supply input wiring LC1, LC2, LD1, LD2 Inverter output wiring X , Y Inverter power supply patterns S11 to S51, S12 to S52 Switching elements D11, D12 Diodes C1, C11 to C13 Decoupling capacitors L1, L21, L22 Reactor

Claims (8)

  A switching power supply comprising a chopper circuit that adjusts a DC voltage to a desired DC output voltage and an inverter circuit that converts a DC output voltage of the chopper circuit into a high-frequency voltage, wherein the chopper circuit and the inverter circuit are the same printed circuit board A switching power supply device characterized by being arranged above.   2. The switching power supply device according to claim 1, wherein circuit elements of the chopper circuit and the inverter circuit are collectively cooled by cooling fins.   The switching power supply device according to claim 2, wherein the shape of the cooling fin is a trapezoidal prism shape or a triangular prism shape.   4. The switching according to claim 2, wherein a through hole is provided in the cooling fin, and circuit elements of the chopper circuit and the inverter circuit are attached to both surfaces of the cooling fin by screwing together. Power supply.   3. The switching power supply device according to claim 2, wherein each circuit element of the chopper circuit and the inverter circuit is collectively attached to the cooling fin by a spring retainer.   The switching power supply device according to any one of claims 1 to 5, wherein a plurality of substrates each having the chopper circuit and the inverter circuit arranged on the same printed circuit board are connected in parallel.   7. The switching power supply device according to claim 6, wherein a reactor is connected to each of the substrate inputs configured by connecting the plurality in parallel.   In a switching power supply device configured by an inverter circuit that converts a DC voltage into a high-frequency voltage, the inverter circuit includes a plurality of decoupling capacitors connected in parallel, and by detecting at least one current of the decoupling capacitor, A switching power supply that detects an overcurrent of an inverter circuit.

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