JP2006191766A - Direct-current power supply device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rectifying circuit capable of automatically switching a normal full-wave rectification circuit and a voltage doubler rectification circuit according to the magnitude of a load current. <P>SOLUTION: A direct-current power supply device 100 is constructed as follows: at least two sets of rectification arms A1 each having a pair of rectifying devices connected in series with each other are connected in bridge formation to form a bridge rectifying circuit; and capacitors C1 and C2 are connected in parallel with both or either of the rectifying devices in either rectification arm A1 of the bridge rectifying circuit. The capacitors have such capacitance that the following operation is performed when a load supplied with power from the direct-current power supply device 100 is in a high-impedance state, the capacitors substantially supply power to the load. At the same time, the bridge rectifying circuit and the capacitors operate as a voltage doubler rectification circuit. When the load is brought into a low-impedance state, the load is supplied with power through the rectifying devices in the bridge rectifying circuit. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a bridge rectifier circuit, and more particularly to a DC power supply device suitable for supplying constant power to a load device that exhibits a high impedance state and a low impedance state.

  As a discharge load using discharge energy, various laser devices, discharge lamp lighting devices, strobe devices, electric discharge machining devices, fusion splicing devices for optical fibers, devices for forming metal thin films on the surface of various substances by discharge, etc. There are discharge loads in very wide fields. Many of these discharge loads require constant power. The discharge is generated in a specific gas such as an inert gas, or in the atmosphere. When discharge occurs, a high voltage is used as a trigger or strike voltage (hereinafter referred to as trigger voltage), and the discharge electrode of the discharge load. It is necessary to apply between them. At this time, if the ability to supply trigger power is insufficient, the voltage between the discharge electrodes does not increase due to the leakage current of the discharge load, and the discharge state may not be reached. However, when the trigger power is too large, there is a problem that it is easy to shift to arc discharge. For this reason, in the conventional power supply device, in order to give a suitable trigger power to the discharge load, ignition (trigger) for starting plasma discharge is separately provided separately from the power supply portion that supplies constant power during steady discharge. For example, there are those provided with a power source portion (for example, see Patent Documents 1 and 2).

  However, such a discharge load power supply device has the following problems. In the case of a power supply device for a discharge load as described above, the output voltage needs to be variable within a certain range, and since constant power is required, for example, the output is 20 kW, the rated output voltage is 1000 V, Sometimes the output current that can be supplied is 20A. When the output voltage is 300 V, it is required to supply an output current of 67 A to the discharge load. However, in a normal discharge load power supply device, if the power supply is designed at 1000V-20A, the maximum current at 300V is about 30A at most, depending on the circuit system, and in any case, the rated output voltage is 1000V or higher. An output of 20 kW cannot be satisfied both with a significantly lower output voltage of 300V.

In such a power supply device, there is an apparatus in which an intermediate voltage tap is provided in the secondary winding of the transformer, and when switching to the intermediate voltage tap, a low voltage and large current is generated, and 300V-67A power can be output. . However, switching the tap requires opening the housing of the power supply device to perform the switching operation, which is cumbersome and requires troublesome confirmation of the discharge of residual charges at the time of switching. . In order to avoid this, it is necessary to design a large-capacity power supply that can supply the maximum current. For example, in the above example, a large-capacity power supply apparatus that can output a power capacity of 1000 V-67 A, that is, 67 kW, is used. Must be made. In that case, since the size of the transformer is roughly proportional to the product of the maximum voltage and the maximum current, a transformer having a power capacity of 67 kW is required, which is more than three times the transmission power 20 kW. This clearly increases the overall size of the power supply device including the transformer, increases the weight, and increases the cost, which is uneconomical.
Japanese Patent Application Laid-Open No. 2004-040962 US Pat. No. 5,717,293

  In order to solve such problems, the present invention operates to automatically switch between a normal full-wave rectifier circuit and a voltage doubler rectifier circuit according to the magnitude of the load current, so that a substantially constant power is obtained. An object is to realize a rectifier circuit that can be supplied. This automatic switching in the present invention is characterized in that it is performed electronically without requiring any physical switching such as mechanical switches and semiconductor switches as well as switching of the intermediate voltage tap of the transformer. is there. Moreover, for example, when the load is a discharge load, the AC input voltage necessary to generate discharge is almost twice as much as a simple pulse width control method of an inverter circuit with a very simple circuit configuration. When the discharge load is in a discharge state and becomes low impedance, the DC constant power required to maintain a steady discharge state is lower than the initial high voltage. It aims to be able to supply.

  In order to solve the above-mentioned problem, the first invention is to rectify only one of the rectifying arms in a bridge rectifying circuit in which a rectifying arm including a pair of rectifying elements connected in series to each other is connected in a bridge configuration. In a DC power supply device in which a capacitor is connected in parallel to both or one of the elements, when the load fed from the DC power supply device is in a high impedance state, the capacitor substantially supplies current to the load. In addition, the bridge rectifier circuit and the capacitor operate as a voltage doubler rectifier circuit, and have a capacitance that supplies current to the load through the rectifier element of the bridge rectifier circuit when the load exhibits a low impedance state. And providing a DC power supply device characterized in that the capacitor has

  In order to solve the above-mentioned problem, the second invention is a single-phase first, second, and third bridge rectification formed by connecting a rectification arm having a pair of rectification elements connected in series to each other in a two-bridge configuration. A DC power supply device comprising a three-phase bridge rectifier circuit formed by connecting a circuit in a three-phase bridge configuration, converting a three-phase AC input to DC and outputting DC power, wherein the first, second and third A capacitor is connected in parallel to both or one of the rectifying elements of only one of the rectifying arms in each of the bridge rectifying circuits, and is connected in series to both or one of the positive, negative and negative sides of the first, second and third bridge rectifying circuits. When the load fed from the DC power supply device is in a high impedance state, the capacitor substantially supplies current to the load, and The rectifier circuit and the capacitor operate as a voltage doubler rectifier circuit, and when the load exhibits a low impedance state, the capacitor has a capacitance that supplies current to the load through the rectifier element of the bridge rectifier circuit. The present invention provides a direct-current power supply device characterized by comprising:

  According to a third aspect of the present invention, a capacitor is provided to both or one of the rectifying elements of only one of the rectifying arms in a bridge rectifying circuit in which at least two sets of rectifying arms each having a pair of rectifying elements connected in series are connected in a bridge configuration. A DC power supply device that is connected in parallel and converts an AC input to a DC output, the DC output current of the DC power supply device is Io, the output voltage is Vo, the frequency of the AC input of the bridge rectifier circuit is f, When the capacitance of the capacitor is C and the constant is k and the constant k is in the range of 1.5 to 12, the capacitance C is a small value not more than k × Io / Vo × f (C ≦ k × Io / Vo × f). The DC power supply device is provided.

  According to a fourth aspect of the present invention, a single-phase first, second, and third bridge rectifier circuit formed by connecting two rectifying arms each having a pair of rectifying elements connected in series to each other in a bridge configuration has a three-phase bridge configuration. In a DC power supply device comprising a connected three-phase bridge rectifier circuit and converting a three-phase AC input to DC and outputting DC power, one of each of the first, second and third bridge rectifier circuits A capacitor is connected in parallel to both or one of the rectifying elements of the rectifying arm only, and a wraparound prevention element is connected in series to both or one of the positive side and the negative side of the first, second, and third bridge rectifier circuits. The constant k is in the range of 0.5 to 4, where the DC output current of the DC power supply is Io, the output voltage is Vo, the frequency of the AC input voltage is f, the capacitance of each capacitor is C, and the constant is k. In When the capacitance C provides a DC power supply apparatus characterized by being selected to k × Io / Vo × f following small value (C ≦ k × Io / Vo × f).

  A fifth invention provides a DC power supply device according to the second invention or the fourth invention, wherein the wraparound prevention element is a diode.

  According to a sixth invention, in any one of the first to fifth inventions, the load is a discharge load in a high impedance state before the start of discharge and in a low impedance state in the discharge state. DC power supply device characterized by

  According to the first aspect of the present invention, the normal full-wave rectifier circuit and the voltage doubler are changed depending on the magnitude of the load current without requiring any physical switching such as switching of the intermediate voltage tap of the transformer, mechanical switch, or semiconductor switch. It is possible to automatically electronically switch between the rectifier circuit. In addition, with a simple circuit configuration that combines a bridge rectifier circuit of a general configuration and a capacitor having an appropriate value of capacitance, when the load impedance is high, an almost constant power of a high voltage is supplied, and the load is When a low impedance state is reached, a substantially constant power can be supplied at a low voltage suitable for that state. In other words, even if the impedance of the load changes significantly, constant power can be supplied to the load without requiring any physical switching such as switching of the intermediate voltage tap of the transformer, mechanical switch, or semiconductor switch. The characteristics can be improved.

  According to the second invention, in addition to the effects of the first invention, a DC power supply device suitable for supplying power to a load having a relatively large power can be provided.

  According to the third aspect of the invention, in addition to the effects of the first aspect of the invention, the electronic switching between the normal full-wave rectifier circuit and the voltage doubler rectifier circuit can be automatically and electronically more reliably depending on the magnitude of the load current. It can be carried out.

  According to the fourth aspect of the invention, in addition to the effect of the second aspect, the electronic switching between the normal three-phase full-wave rectifier circuit and the three-phase voltage doubler rectifier circuit can be made more reliably by the magnitude of the load current. It can be performed.

  According to the fifth invention, in addition to the effects of the second invention or the fourth invention, the capacitor voltage can be secured, so that the normal full-wave rectifier circuit and the voltage doubler rectifier circuit can be more reliably determined by the magnitude of the load current. Can be electronically switched between.

  According to the sixth aspect of the invention, in addition to the effects of the first and second aspects, the laser device, the discharge lamp lighting device, the strobe device, the electric discharge machining device, the optical fiber fusion splicing device, the metal by discharge The present invention can be applied to a discharge load such as an apparatus for forming a thin film on the surface of various substances.

[Embodiment 1]
First, a first embodiment for carrying out the present invention will be described with reference to FIGS. 1 and 2. 1A shows a DC power supply device 100 according to the first embodiment of the present invention, FIG. 1B shows an equivalent circuit of a rectifier circuit when a load exhibits high impedance, and FIG. ) Shows an equivalent circuit of the rectifier circuit when the load exhibits low impedance, and FIG. 2 is a diagram showing power characteristics of the load. In FIG. 1, an input-side rectifier circuit 1 has a general three-phase full bridge configuration that rectifies a three-phase AC voltage and converts it into DC power. When the AC input is single-phase, the input-side rectifier circuit 1 is of course a single-phase full bridge configuration. The inverter circuit 2 converts the DC voltage into a high-frequency AC voltage of several kHz to several tens kHz. The inverter circuit 2 is a switching semiconductor element such as a MOSFET or IGBT having a well-known full-bridge configuration or a half-bridge configuration. The inverter circuit 2 is subjected to pulse width control (on-time ratio control) to convert DC power into a single phase. Convert to high frequency power. It is preferable that a diode is connected in parallel with the reverse polarity to the switching element. The transformer 3 has an AC voltage obtained by boosting a high-frequency resonance voltage applied from the inverter circuit 2 through the resonance inductor 4 and the resonance capacitor 5 to the primary winding 3a with a predetermined transformation ratio. Appears in 3b. These members constitute an AC source 6. The present invention is not limited by the AC source 6, and the object of the present invention can be achieved with AC power from any AC source.

  The secondary winding 3b of the transformer 3 includes a first rectifying arm A1 including rectifying elements 7A and 7B connected in series with each other, and a second rectifying arm including rectifying elements 7C and 7D connected in series with each other. A single-phase bridge rectifier circuit 7 composed of A2 is connected. The capacitors C1 and C2 are connected in parallel only to the rectifying elements 7C and 7D of the second rectifying arm A2. These capacitors C1 and C2 have a capacitance equal to or less than a predetermined value for the reason described later. A major feature of the present invention is that the capacitors C1 and C2 having such a capacitance are connected in parallel to the rectifying element of any rectifying arm of the bridge rectifying circuit 7. The capacitors C1 and C2 may be connected in series with each other, and the resonance capacitor 5 may be connected to the secondary winding 3b side of the transformer 3.

  A voltage detection circuit 8 is connected between the positive DC terminal T1 and the negative DC terminal T2 of the bridge rectifier circuit 7. A current detector 9 for detecting the load current is connected in series with the load 10. The load 10 is a discharge load typified by various laser devices, discharge lamp lighting devices, strobe devices, electric discharge machining devices, optical fiber fusion splicing devices, devices that form metal thin films on the surface of various substances by discharge, and the like. In many cases. This is because many discharge loads require constant power. The voltage detection signal detected by the voltage detection circuit 8 and the current detection signal detected by the current detector 9 are input to the control circuit 11. The control circuit 11 performs normal pulse width control on the switching semiconductor element of the inverter circuit 2 based on the voltage detection signal and the current detection signal, controls the voltage between the positive DC terminal T1 and the negative DC terminal T2, and has constant power or Perform current control.

  Capacitors C1 and C2 have substantially the same capacitance and are assumed to be C. If the capacitance C of the capacitors C1 and C2 is less than a certain value and sufficient for the initial small load current, the bridge rectifier circuit 6 becomes an equivalent circuit as shown in FIG. That is, the rectifying elements 7A and 7B of the first rectifying arm A1 and the capacitor C1 or C2 constitute a voltage doubler rectifier circuit, and output a voltage 2E that is almost twice the AC output voltage E of the AC source 6. I understood. This point will be described in more detail. Charges of the capacitors C1 and C2 charged through the rectifying element 7A and the rectifying element 7B of the first rectifying arm A1 are in each cycle of the AC output of the AC source 6 when the load current is small. The electric charges that are not completely discharged and remain in the capacitors C1 and C2 hold the rectifying elements 7C and 7D connected in parallel to each other in a reverse bias state, and do not conduct the rectifying elements 7C and 7D.

  As a result, the bridge rectifier circuit 6 is equivalent to a voltage doubler rectifier circuit as shown in FIG. The load characteristic of the voltage doubler rectifier circuit is a characteristic in which the voltage drops rapidly as the load current increases, as shown by the curve (B) in FIG. This voltage drop characteristic depends on the capacitances of the capacitors C1 and C2, and the drop is smaller as the capacitance is larger. The no-load output voltage of the bridge rectifier circuit 6 is a voltage 2E that is almost twice the AC output voltage E of the AC source 6. When the load is short-circuited, that is, when the load voltage is zero volts, the AC output voltage E of the AC source 6 is a rectified waveform of the short-circuit current Is short-circuited by the capacitors C1 and C2, and the short-circuit current Is is the electrostatic capacitance of the capacitors C1 and C2. When the capacity is C, it can be approximated to a value Is proportional to I = E / 2πf · 2C.

  When the load current is large, the capacitors C1 and C2 have insufficient capacitance and do not function as capacitors constituting the voltage doubler rectifier circuit, and the rectifier elements 7A to 7D are as shown in FIG. A general full-wave rectifier circuit is configured. That is, the charge of the capacitors C1 and C2 charged through the rectifying element 7A and the rectifying element 7B of the first rectifying arm A1 in each cycle of the AC output of the AC source 6 has a large load current. In the first half of each cycle of AC output, it is rapidly discharged and does not remain, and as a result, the reverse bias time of the rectifying elements 7C and 7D connected in parallel to the capacitors C1 and C2 is shortened. In each cycle of AC input, the rectifier elements 7C and 7D are turned on. As a result, the output voltage of the bridge rectifier circuit 7 becomes a voltage E that is substantially equal to the AC output voltage E of the AC source 6. At this time, if the capacitance C of the capacitors C1 and C2 is sufficiently large, the output voltage of the bridge rectifier circuit 7 can be increased to about 2E even when the load current is sufficiently large. The rectifying elements 7A and 7B of the rectifying arm A1 and the capacitor C1 or C2 set the capacitance C of the capacitors C1 and C2 to be small enough to form a voltage doubler rectifier circuit, so that the load current is sufficiently large. In this case, the output voltage of the bridge rectifier circuit 7 becomes a voltage E substantially equal to the AC output voltage E of the AC source 6.

  The load characteristic of the bridge rectifier circuit 7 is a curve (C) in FIG. 1, and the output voltage of the bridge rectifier circuit 7 at the rated load is a voltage E that is substantially equal to the AC output voltage E of the AC source 6. The output current at the time of short circuit is limited by the internal impedance of the AC source 6, but in practice, the inverter circuit 2 is controlled by detecting the current, and constant current control of any value that the inverter circuit 2 can withstand is performed. Is called. Here, a case in which the short-circuit current Is during double voltage operation is controlled to 2 times and 2 Is is shown. Therefore, the load characteristic of the bridge rectifier circuit 7 includes the characteristic (B) of FIG. 2 showing the load characteristic of the voltage doubler rectifier circuit shown in FIG. 1 (B) and the full-wave rectifier circuit shown in FIG. 1 (C). A characteristic (A) obtained by combining the characteristic (C) of FIG.

  Obtaining such knowledge, in the present invention, the capacitances C and C2 of the capacitors C1 and C2 capable of realizing the aforementioned knowledge were quantitatively obtained. The DC output current of this DC power supply device is Io, the output voltage of the bridge rectifier circuit 7, that is, the rectified voltage is Vo, the frequency of the output voltage of the AC source 6, that is, the frequency of the AC input voltage of the bridge rectifier circuit 7, and the constant It was found that the capacitance C of the capacitors C1 and C2 should be selected to be a small value not more than k × Io / Vo × f, that is, C ≦ k × Io / Vo × f. However, this equation holds when the constant k is 1.5 in the case of a single phase, as a result of experiment with various changes in the capacitance C, current Io, rectified voltage Vo, frequency f, and constant k of the capacitors C1 and C2. It is confirmed that it is only in the range of 12 to 12 (in the case of 3 phases, it is 1/3 of the range). When the capacitors C1 and C2 have a capacitance C satisfying the equation C ≦ k (1.5 to 12) × Io / Vo × f, the bridge rectifier circuit 6 is configured as shown in FIG. When the load current is large, a general full-wave rectifier circuit as shown in FIG. 1C is formed.

Next, the operation of the DC power supply circuit 100 shown in FIG. 1 will be described. First, a preferred example of the AC source 6 will be described. It is desired that a substantially constant power can be supplied with a simple circuit configuration and a normal pulse width control method when the load 10 is a discharge load as described above. An inverter circuit 2 that is a bridge inverter formed by connecting a switching element such as an IGBT in a bridge configuration, a resonance inductor 4 and a resonance capacitor 5 that are connected in series to the AC output, and a resonance capacitor 5 that are connected in parallel. The transformer 3 having the primary winding 3a and the bridge rectifier circuit 6 connected to the secondary winding 3b constitute a parallel resonance converter, which is disclosed in Japanese Patent Publication No. 6-48904. Is disclosed. Although details are disclosed in Japanese Examined Patent Publication No. 6-48904, the output power of the parallel-type resonance converter is Lr as the inductance value of the resonance inductor 4 and the resonance capacitance of the resonance capacitor 5. When the value is Cr, the resonance frequency Fr = ^1/2 (Lr · Cr) ^1/2 that is inversely proportional to the resonance impedance Z = (Lr / Cr) ^1/2 and related to the switching frequency Fs of the inverter circuit 2 It is determined by a combination of a satisfactory inductance value Lr and capacitance value Cr. Normally, the resonance frequency Fr is 1.5 times the switching frequency Fs (Fr = 1.5 Fs), and the current flowing through the switching element has a substantially resonant current waveform. A voltage that is 1.2 to 1.8 times the AC input voltage of the inverter circuit is obtained in the primary winding 3a of the transformer 3 by resonance.

  The sinusoidal AC voltage is boosted to a predetermined voltage by the transformer 3 and becomes an AC input voltage of the bridge rectifier circuit 6. When the load 10 is a discharge load, the load 10 may have a high impedance or a low impedance due to a change in load conditions due to a change in electrical characteristics of a gas in the load or a different discharge system. is there. Alternatively, the impedance of the load 10 may change during the operation. For example, a discharge load of 10 kW may change from a high impedance load of 1000 V and 10 A to a low impedance load of 500 V and 20 A. Therefore, first, a description will be given by taking as an example a discharge load with a high impedance of 1000 V and 10 A, in which a current flowing with 10 kW of power is small. In a half cycle in which the voltage of the secondary winding 3b of the transformer 3 is positive with respect to the terminal B and the terminal A is positive, a current flows from the terminal A to the terminal B through the rectifier element 7A and the capacitor C1. Charge with polarity shown. Next, in a half cycle when terminal B is positive with respect to terminal A, current flows from terminal B to terminal A through rectifier 7B and capacitor C2, and capacitor C2 having a small capacitance C is charged with the polarity shown. At this time, if the load current is large, a current path that flows from the terminal B to the terminal A through the rectifying element 7C, the capacitors C1 and C2, and the rectifying element 7D is formed, but since the load current is small as described above, Since the capacitor C1 is not discharged so much and the voltage having the polarity shown in the figure remains, the voltage rectifier 7C is reverse-biased by the residual voltage of the capacitor C1 and does not conduct. The voltage of the secondary winding 3b of the transformer 3 is the same even when the terminal A is a positive half cycle with respect to the terminal B, and the rectifier element 7D is reverse-biased by the residual voltage of the capacitor C2 and thus does not conduct. The bridge rectifier circuit 6 is a voltage doubler rectifier circuit as shown in FIG. 1B, and its load characteristics are as shown in FIG. 2B.

  When the voltage of each of the capacitors C1 and C2 reaches a voltage approximately equal to the voltage E between the terminals A and B of the secondary winding 3b of the transformer 3, the load 10 is approximately equal to twice the voltage E. -2E is applied. With this voltage, a predetermined power can be supplied to the high-impedance discharge load. Next, when the load conditions change or when the impedance of the load 10 decreases due to a different discharge system, for example, in the case of a low impedance discharge load of 500 V and 20 A even with the same power of 10 kW, the load current flowing through the load 10 Will increase. Even in this discharge state, the charging operation of the capacitor C1 and the capacitor C is the same as the period when the load current before the discharge is small, but the discharge of the capacitor C1 and the capacitor C is the secondary of the transformer 3 because the load current is large. Since the load 10 is discharged in the first half of each cycle of the AC voltage of the winding 3b, the rectifier 7C and the rectifier 7D start to conduct at least in the middle of each cycle. That is, after discharging, the bridge rectifier circuit 7 functions as a full-wave rectifier circuit composed of rectifier elements 7A to 7D, and supplies a load current required by the load 10. The load characteristic is as shown by characteristic (C) in FIG. Therefore, the overall load characteristic of the bridge rectifier circuit 7 is the characteristic curve (A) of FIG. 2, which shows a substantially constant power characteristic. In the above description, an example has been described in which the impedance of the load 10 varies greatly depending on the load conditions. However, if a power supply device having this constant power characteristic is used, for example, a 10 kW constant power source can provide a high impedance of 1000 V and 10 A. In addition to supplying power to the load, it can also supply another low impedance load of 500V, 20A. That is, this power supply apparatus can be applied to both loads having different output voltages and output currents.

  In particular, if the capacitance C of the capacitors C1 and C2 is selected to be a small value not more than k × Io / Vo × f, that is, C ≦ k (1.5 to 12) × Io / Vo × f, the load is surely ensured. The bridge rectifier circuit 7 functions as a voltage doubler rectifier circuit composed of rectifier elements 7A and 7B and capacitors C1 and C2 in a range where the current is small, and is composed of rectifier elements 7A to 7D in a range where the load current is large. It functions as a full-wave rectifier circuit. Therefore, in this embodiment, the voltage doubler rectification operation and the full wave rectification operation can be automatically and electronically switched without switching the intermediate voltage tap of the transformer or switching by the switching element, and the rectifying element 7A. It can be realized with a simple circuit configuration in which capacitors having a capacitance equal to or less than a value in one of the rectifying elements 7A and 7B or the rectifying elements 7C and 7D of one of the rectifying arms of the full-wave rectifying circuit composed of ˜7D are connected in parallel. The DC power supply device 100 is characterized in that it can automatically switch between a normal full-wave rectifier circuit and a voltage doubler rectifier circuit according to the magnitude of the load current as described above.

[Embodiment 2]
Next, a DC power supply device 200 according to the second embodiment will be described. The same symbols as those used in FIG. 1 indicate members having the same names. The AC source 6 of the DC power supply apparatus 200 is a general three-phase full-wave rectifier circuit formed by connecting a diode in a full bridge configuration, and converts DC power generated by the three-phase full-wave rectifier circuit into high-frequency three-phase AC power. It comprises a three-phase high-frequency inverter circuit having a general configuration, a predetermined connection, for example, a three-phase transformer having a primary winding and a secondary winding that are star-connected (Y-Y connected). The three-phase high-frequency inverter circuit is obtained by connecting switching elements such as MOSFETs or IGBTs in a three-phase bridge configuration. The AC power of the inverter circuit 2 is converted into a desired voltage by the three-phase transformer 3. The transformer 3 has a general configuration, for example, in which a primary winding and a secondary winding are star-connected (Y-Y connection). A three-phase bridge rectifier circuit 7 is connected to the three-phase AC input terminals A, B, and C connected to the three-phase output terminal of the AC source 6. The second embodiment is characterized by a three-phase bridge rectifier circuit 7.

  The three-phase bridge rectifier circuit 7 includes three sets of bridge rectifier circuits 7 (1), 7 (2), and 7 (3) having the same configuration. The bridge rectifier circuit 7 (1) bridges a first rectifier arm A1 including rectifier elements 7A and 7B connected in series with each other and a second rectifier arm A2 including rectifier elements 7C and 7D connected in series with each other. A single-phase bridge rectifier circuit having a general configuration configured, capacitors C1 and C2 connected in parallel to the rectifier elements 7C and 7D, respectively, and connected in series to the cathode side and the anode side of the rectifier circuit, respectively. The wraparound prevention elements D1 and D2 are provided. Usually, a diode is used for the wraparound prevention elements D1 and D2. The alternating current side of the first rectifying arm A1 is connected to the three-phase alternating current input terminal A, and the alternating current side of the second rectifying arm A2 is connected to the three-phase alternating current input terminal B. It is connected to the positive output line L1 and the negative output line L2 through D1 and D2, respectively.

  The bridge rectifier circuit 7 (2) bridges a third rectifier arm A3 including rectifier elements 7E and 7F connected in series with each other and a fourth rectifier arm A4 including rectifier elements 7G and 7H connected in series with each other. A rectifier circuit having a general configuration, capacitors C3 and C4 connected in parallel to the rectifier elements 7G and 7H, and a wraparound prevention connected in series to the cathode side and the anode side of the rectifier circuit, respectively. And elements D3 and D4. The AC side of the third rectifying arm A3 is connected to the three-phase AC input terminal B, and the AC side of the fourth rectifying arm A4 is connected to the three-phase AC input terminal C. This rectifier circuit is connected to the positive output line L1 and the negative output line L2 through the wraparound prevention elements D3 and D4, respectively. Similarly, the bridge rectifier circuit 7 (3) is also formed by a bridge configuration of a fifth rectifier arm A5 including rectifier elements 7I and 7J and a sixth rectifier arm A6 including rectifier elements 7K and 7L. Rectifier circuit having the above configuration, capacitors C5 and C6 connected in parallel to the rectifier elements 7K and 7L, and wraparound prevention elements D5 and D6 connected in series to the cathode side and the anode side of the rectifier circuit, respectively. Consists of. The AC side of the fifth rectifying arm A5 is connected to the three-phase AC input terminal C, and the AC side of the sixth rectifying arm A6 is connected to the three-phase AC input terminal A. The rectifier circuit is connected to the positive output line L1 and the negative output line L2 through the wraparound prevention elements D5 and D6, respectively.

  What is important here is that, as described above, the capacitors C1 to C6 all have substantially the same capacitance C, and when the load current is small, the capacitance C is not sufficiently discharged in each cycle, and a charge remains, and the residual voltage. Therefore, the rectifying elements 7C, 7D, 7G, 7H, 7K, and 7L connected in parallel to the capacitors C1 to C6 are reversely biased and do not conduct. As a result, the bridge rectifier circuit 7 (1) forms a voltage doubler rectifier circuit formed by bridge-connecting the rectifier elements 7A and 7B and the capacitors C1 and C2. The bridge rectifier circuit 7 (2) constitutes a voltage doubler rectifier circuit formed by bridge-connecting rectifier elements 7E and 7F and capacitors C3 and C4. The bridge rectifier circuit 7 (3) includes rectifier elements 7I and 7J. And a capacitor C5 and C6 are bridge-connected to form a voltage doubler rectifier circuit. Preferably, the DC output current of this DC power supply device is Io, the output voltage of the bridge rectifier circuit 7, that is, the rectified voltage is Vo, the frequency of the output voltage of the AC source 6, that is, the frequency of the AC input voltage of the bridge rectifier circuit 7 is f. When the constant is k, the capacitors C1 to C6 are selected so as to have a capacitance C that satisfies a small value (C ≦ k × Io / Vo × f) of k × Io / Vo × f or less. . Here, the constant k may be about one third of the value of the first embodiment of FIG. 1, 1.5 to 12, that is, about 0.5 to 4. The reason is that since three bridge rectifier circuits are used for three phases, the current sharing of each rectifier circuit is also one third.

  When the capacitance C of the capacitors C1 to C6 is selected to satisfy C ≦ k (0.5 to 4) × Io / Vo × f, the load current becomes the rated current value or a current value in the vicinity thereof. In some cases, the capacitors C1 to C6 do not have enough capacitance to form a voltage doubler rectifier circuit, and do not function as capacitors connected in parallel to the capacitors C1 to C6, respectively, and bridge rectifier circuits 7 (1), 7 (2) and 7 (3) are full-wave rectifier circuits including rectifier elements 7A to 7D, rectifier elements 7E to 7H, and rectifier elements 7I to 7L. Since these reasons have already been described in detail in the description of the first embodiment, a description thereof will be omitted.

  Since the operation is basically the same as the operation of the DC power supply device 100, it will be briefly described. During the period in which the AC input terminal A is positive with respect to B, the capacitor C1 is charged to the voltage E between the AC input terminals A and B through the rectifying element 7A, and the AC input terminal A is with respect to C. During the period when the positive voltage is generated, the capacitor C6 is charged through the rectifying element 7J. Further, during the period in which the AC input terminal B is positive with respect to A, the capacitor C2 is charged to the voltage E between the AC input terminals B and A through the rectifying element 7B, and the AC input terminal B is set to C. On the other hand, during a period in which a positive voltage is generated, the capacitor C3 is charged to the voltage E between the AC input terminals B-C through the rectifying element 7E. Further, during the period in which the AC input terminal C is generating a positive voltage with respect to A, the capacitor C5 is charged to the voltage E between the AC input terminals CA through the rectifying element 7I, and the AC input terminal C is set to B. On the other hand, during a period in which a positive voltage is generated, the capacitor C4 is charged to the voltage E between the AC input terminals C-B through the rectifying element 7F. The wraparound prevention element D1 prevents the charges of the capacitors C3 and C5 from being discharged to the capacitor C1, and the wraparound prevention element D3 prevents the charges of the capacitors C1 and C5 from being discharged to the capacitor C3. Further, the wraparound prevention element D5 functions to prevent the charges of the capacitors C1 and C3 from wrapping around the capacitor C5.

  It is assumed that the load 10 is a discharge load and is in a high impedance state before entering a discharge state. Therefore, since the load 10 has a high impedance in the initial stage, as described above, since the load current is small, the capacitors C1 to C6 cannot be discharged in any cycle, and the electric charge remains. The rectifying elements 7C, 7D, 7G, 7H, 7K, and 7L connected in parallel to the capacitors C1 to C6 are reverse-biased and do not conduct. At this time, the bridge rectifier circuits 7 (1), 7 (2), and 7 (3) are voltage doubler rectifier circuits including rectifier elements 7A, 7B, 7E, 7F, 7I, and 7J and capacitors C1 to C6. The load 10 is applied with −2E, which is twice the AC input voltage E. When a discharge occurs in the discharge load due to this voltage, the load impedance decreases, and the load current increases. As described above due to the increase in the load current, all of the rectifier elements 7A to 7L of the bridge rectifier circuit 7 perform rectification and operate as a three-phase full-wave rectifier circuit. Therefore, the bridge rectifier circuit 7 can flow a load current required by the load 10 and can supply a voltage E substantially equal to the AC input voltage E. In this embodiment, when the bridge rectifier circuit 7 operates as a full-wave rectifier circuit, the rectifier elements 7A to 7L share the load current with the pair of rectifier elements, so that a rectifier element having a small current capacity can be used. .

  The rectifying element according to the present invention is composed of a single diode, a required number of diodes connected in parallel or in series, and a plurality of diodes connected in series (parallel connection). In addition, the determination formula for the capacitance of the capacitor (C ≦ k × Io / Vo × f) varies somewhat depending on various design conditions, and the numerical value calculated by the formula may deviate from the actual value. However, unless it deviates from the spirit of the present invention, it is included in the present invention and does not limit the present invention.

  In the DC power supply device 100, the capacitors C1 and C2 are connected in parallel to the rectifier elements 7C and 7D in consideration of the positive / negative balance, but the object of the present invention can be achieved even if one of the capacitors C1 and C2 is deleted. . Similarly, in the DC power supply device 200, either the capacitors C1, C3, C5 or the capacitors C2, C4, C6 may be deleted. In this case, for example, when the capacitors C2, C4, and C6 are deleted, the wraparound prevention elements D2, D4, and D6 can be deleted.

Further, the DC power supply devices 100 and 200 include an additional capacitor having a capacitance substantially equal to that of the capacitors C1 and C2 or the capacitors C1 to C6 in parallel between the DC output terminals of the bridge rectifier circuit 7, that is, in parallel with both ends of the load. Also good. Since the capacitance of the additional capacitor is small, when the load current is small, the additional capacitor is charged to a voltage 2E that is almost twice the AC input voltage E and acts as a trigger capacitor, and the load is a discharge load. Is effective.

It is a figure which shows the power supply device 100 for discharge which is one Embodiment of this invention. It is a figure which shows the output characteristic of the bridge rectifier circuit in this invention. It is a figure which shows the power supply device 200 for discharge which is other one Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Input side rectification circuit 2 ... Inverter circuit 3 ... Transformer 4 ... Resonance inductor 5 ... Resonance capacitor 6 ... AC source 7 ... Bridge rectification circuit 7A-7L ..Rectifying element 8 ... Voltage detection circuit 9 ... Current detection circuit 10 ... Load 11 ... Control circuit D1-D6 for inverter circuit 2 ... Circuit prevention elements C1-C6 ... Capacitor

Claims (6)

DC formed by connecting capacitors in parallel to both or one of the rectifiers of only one of the rectifier arms in a bridge rectifier circuit in which at least two rectifier arms each having a pair of rectifier elements connected in series are connected in a bridge configuration. In the power supply,
When the load fed from the DC power supply device is in a high impedance state, the capacitor substantially supplies current to the load, and the bridge rectifier circuit and the capacitor operate as a voltage doubler rectifier circuit, and The capacitor has a capacitance that supplies a current to the load through the rectifying element of the bridge rectifier circuit when the load is in a low impedance state. Three-phase formed by connecting a single-phase first, second, and third bridge rectifier circuit in a three-phase bridge configuration in which two rectifying arms each having a pair of rectifying elements connected in series are connected in a two-bridge configuration In a DC power supply device that includes the bridge rectifier circuit and converts the three-phase AC input to DC and outputs DC power,
Capacitors are connected in parallel to both or one of the rectifying elements of only the one rectifying arm in each of the first, second, and third bridge rectifier circuits,
A wraparound prevention element is connected in series to both or one of the positive side and the negative side of the first, second and third bridge rectifier circuits,
When the load fed from the DC power supply device is in a high impedance state, the capacitor substantially supplies current to the load, and the bridge rectifier circuit and the capacitor operate as a voltage doubler rectifier circuit. The capacitor has a capacitance that supplies a current to the load through the rectifying element of the bridge rectifier circuit when the load is in a low impedance state. A capacitor is connected in parallel to both or one of the rectifying elements of only one of the rectifying arms in a bridge rectifying circuit in which at least two sets of rectifying arms having a pair of rectifying elements connected in series with each other are connected in a bridge configuration, There is a DC power supply that converts AC input to DC output,
The constant k is in the range of 1.5 to 12, where the direct current output current of the direct current power supply device is Io, the output voltage is Vo, the frequency of the alternating current input of the bridge rectifier circuit is f, the capacitance of each capacitor is C, the constant is k. The capacitance C is selected to be a small value (C ≦ k × Io / Vo × f) of k × Io / Vo × f or less. Three-phase formed by connecting a single-phase first, second, and third bridge rectifier circuit in a three-phase bridge configuration in which two rectifying arms each having a pair of rectifying elements connected in series are connected in a two-bridge configuration In the DC power supply device that includes the bridge rectifier circuit and converts the three-phase AC input to DC and outputs DC power,
A capacitor is connected in parallel to both or one of the rectifying elements of only the one rectifying arm in each of the first, second, and third bridge rectifying circuits,
A wraparound prevention element is connected in series to both or one of the positive side and the negative side of the first, second, and third bridge rectifier circuits,
The DC power supply device has a DC output current Io, an output voltage Vo, a frequency of AC input voltage f, a capacitance of each capacitor C, a constant k, and a constant k in the range of 2/3 to 10/3. The capacitance C is selected to be a small value (C ≦ k × Io / Vo × f) of k × Io / Vo × f or less. In claim 2 or claim 4,
The direct current power supply device, wherein the wraparound preventing element is a diode. In any one of Claims 1 thru | or 5,
The DC power supply device according to claim 1, wherein the load is a discharge load in a high impedance state before the start of discharge and in a low impedance state in the discharge state.

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