Current-controlled ac-DC power supply

Abstract

To contribute to the miniaturization, weight reduction, and cost reduction of AC-DC power supplies that obtain DC power supplies with high power factor isolation and voltage controllability from AC power supplies.SOLUTION: A current-controlled AC-DC power supply includes a main circuit consisting of a diode rectifier circuit 200, a current pulse width controlled inverter 400, a high frequency transformer 500, and a diode rectifier circuit 600, and obtains a controllable DC output voltage under high power factor rectification operation simply by controlling the conduction ratio of an inverter used.SELECTED DRAWING: Figure 18

Description

Technical Field

[0001] The present invention is a technology that contributes to the miniaturization, weight reduction, and cost reduction of an AC-DC power supply for obtaining a voltage-controllable DC power supply that is insulated from an AC power supply with high power factor.

Background Art

[0002] In order to configure an AC-DC power supply that satisfies such specifications, generally is the AC power supply is rectified with high power factor by and then converted into AC by switching control, and a transformer by is used to control the voltage and current as required, resulting in a conversion circuit configuration so where the main circuit configuration and the control system become complicated.

[0003] Also, in order to increase the device capacity as an AC-DC power supply, it is generally necessary to design for each of various capacities. Therefore, it is desired to achieve standardization of the power supply device and multiplex according to the required capacity. However, in a voltage-type conversion device, direct parallel connection causes a cross current to flow between devices, the current between the multiplexing devices resulting in problems such as difficulty in balance control.

Prior Art Documents

Non-Patent Documents

[0004]

Non-Patent Document 1

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

[0006] Figure 1 shows a block diagram of the main circuit configuration for obtaining a DC power supply that is isolated and voltage controllable with a high power factor. therefore Previous configuration block diagram is 1B shows a block diagram of the system according to the present invention.

[0007] In Figure (a), each of the three converters 、 The control unit requires switching control with at least two converters, but in this invention, As shown in Fig. (b), These three converters are integrated into one switching control unit. by doing so, The aim is to make AC-DC power supplies smaller, lighter and cheaper.

[0008] First, in the process of rectifying an AC power source to obtain a DC voltage source, a rectifier circuit using a diode bridge circuit is used. However, rectifier circuits that directly connect a smoothing capacitor to obtain a smooth DC voltage source distort the inflow current waveform, so except for small-capacity rectifier circuits, a PFC converter that can improve the inflow current waveform is used.

[0009] A typical PFC converter uses a boost DC / DC converter with a relatively large inductor. the alternating current To make it a sine wave in phase with the AC power supply voltage, with the current feedback amount Instantaneous current comparison control is performed, and it is necessary to detect DC voltage and generate a sine wave reference current waveform, so it is implemented as an IC. even if using something The main circuit configuration and control system become more complex, as voltage and current sensors become necessary.

[0010] also A transformer is used for insulation between the AC power supply and the DC output. However, commercial frequency transformers are considered from the perspectives of size, weight, and cost. because there is a problem in The DC voltage obtained by the PFC converter once is converted to a high frequency by an inverter and insulated by a high frequency transformer. using There is a means of insulation by a high frequency transformer.

[0011] high frequency The degree of miniaturization and weight reduction of the transformer depends on the switching frequency of the inverter. With the increase in frequency, there is a concern about the increase in switching losses due to hard switching.

[0012] Therefore, it is also conceivable to reduce the switching losses by applying a soft switching control method to the switching operation of the high frequency inverter, but the circuit configuration becomes complicated.

[0013] Then, after converting to the required voltage level via a high frequency transformer, it is again rectified by a rectifier circuit and smoothed by a smoothing capacitor connecting to obtain a DC output. and further as needed To control the DC output voltage and current for a DC-DC converter is used.

[0014] As described above, to configure an AC-DC power supply that obtains a voltage controllable DC power supply with high power factor and insulation from the AC power supply, Generally a PFC converter that performs DC conversion with high power factor from the AC power supply, direct current a DC output insulated from the power supply to obtain a DC-DC converter using a high frequency transformer, and an output control DC-DC converter that controls the DC output converted to the required voltage level to the required voltage and current are required.

[0015] In addition, when the high frequency inverter can not only operate the high frequency transformer but also detect the DC output voltage and current and perform control such as conduction width control controlled by the third stage DC-DC converter can be rectified and smoothed only the filter works and can be made to perform such functions.

[0016] Here, as a method for constructing a high-frequency inverter, there are a voltage-source inverter and a current-source inverter, which are used appropriately according to the purpose of use. However, due to the development of switching elements that can perform high-speed switching control at any time, for a DC voltage source, a switch circuit composed of a switching element and a diode connected in anti-parallel is configured in a bridge configuration done The voltage-source inverter is generally widely used.

[0017] (Non-Patent Document 1) shows a voltage-source inverter connected to a voltage source, a current-source inverter connected to a current source, and a combination of typical loads compatible with them. The voltage-source inverter is generally used with an inductive load in which an inductor is connected in series to the load, and the current-source inverter is used with a capacitive load in which a capacitor is connected in parallel to the load.

[0018] In a voltage-source inverter, in order to secure a current path for the current flowing through the inductive load current when the switch is turned off, a switch circuit in which a diode is connected in anti-parallel to the switching element is used. In a current-source inverter, since the voltage of the capacitor is applied as a reverse voltage to the switch during switch switching, a switching element having a reverse voltage withstand or a switch circuit in which a diode is connected in series to the switching element is used.

[0019] Therefore, in a current-source inverter, generally, compared with the switch configuration used in a normal voltage-source inverter, not only does the switch circuit become complicated, but also the diode when necessary, conduction loss increases.

[0020] Figure 2 shows (a) the circuit configuration of a general current-source inverter and (b) the inductor using It also shows the circuit configuration of an inverter that can be configured with the switch circuit that constitutes a voltage-source inverter even in a current source.

[0021] Even in a current-source inverter, As shown in Fig. (a), the capacitor C is directly connected to the AC output ac when directly connected, and as shown in Fig. (b),A capacitor is connected as an AC load via a diode bridge rectifier circuit C dc when there is, and in the latter case, the switches forming the inverter circuit are not subjected to reverse voltage.

[0022] (Patent Document 1) is a DC power supply device aimed at controlling a DC load voltage and current by controlling an inductor current with a buck chopper and performing diode rectification via a transformer with an inverter, and controlling based on voltage detection so that the voltage does not destroy the elements with a sudden change in the load.

[0023] In this document, the inverter used has a capacitor connected to the DC output of the AC load as diode bridge rectifier circuit, so a switch circuit without reverse voltage withstand from the inductor current is used on the DC side.

[0024] However, since the inverter circuit does not have the switch circuit configuration as shown in Fig. 2(b), the diodes are connected in reverse parallel and a transformer is connected to the output of the inverter, a current path due to the leakage inductor of the transformer during switch switching is not ensured, so there is a concern that a spike voltage may be applied to the switch element.

[0025] Note that (Patent Document 1) in the rectifier circuit section from the AC power supply of the DC power supply device is composed only of a diode bridge circuit and a smoothing capacitor, and no measures for improving the high power factor are taken.

[0026] On the other hand, (Patent Document 2) is is composed of a PFC circuit, and its DC output voltage is AC-converted by a voltage-type inverter, transformed to an appropriate voltage via a transformer, and an LC smoothing circuit is connected to the output of the diode rectifier circuit to configure present a DC power supply with a general circuit configuration similar to Fig. 1(a) in intending to improve the control method of PFC done is what it is.

[0027] However, the main circuit configuration is the same as the conventional one similarly multiple becomes complicated and requires PFC control and inverter control. Therefore, miniaturization and weight reduction are issues to while being composed of multiple converters present for of the entire device a decrease in efficiency is also a concern.

[0028] (Patent Document 3) is a control technology for a DC-DC converter using soft switching with an LC resonance circuit, and is an effective control technology for reducing switching losses and switching noise caused by hard switching in a voltage source inverter

[0029] Also, (Patent Document 4) is a control technology for a DC-DC converter that enables insulation and voltage control by using the soft switching control DC-DC converter of (Patent Document 3) and a high-frequency transformer.

[0030] By using (Patent Document 3) or (Patent Document 4) in the voltage source inverter section of (Patent Document 2), improvement in efficiency and reduction in noise can be expected, but it leads to further complication of the main circuit configuration.

[0031] (Patent Document 5) is a control method for an AC-DC converter that can operate a DC power supply capable of controlling DC output while insulating from an AC power supply with high power factor, and is characterized by being controllable with one switching element.

[0032] Fig. 3 shows a circuit configuration example as a single-phase AC-DC power supply using a flyback transformer configured and has an extremely simple circuit configuration. The DC output can be controlled by controlling the current flowing rate of the switching element.

[0033] However, since the transformer operates with a single power supply, it is likely to cause saturation of the transformer, and it is necessary to process the commutation energy due to the leakage inductance of the transformer with a snubber circuit, etc. The applicable field is relatively small-capacity devices is limited.

Means for Solving the Problems

[0034] In the present invention, as shown in FIG. 4, an AC power supply is connected to a diode bridge rectifier circuit including an LC filter circuit, the rectified output is connected to an inductor, and the current flowing through the inductor is configured by a switch circuit connected in anti-parallel with a diode and current control type The inverter performs switch control to current control type convert the AC current from the inverter to a required voltage via a high-frequency transformer, and then connect the rectified output to a smoothing capacitor by a diode bridge rectifier circuit again and connect it to a DC load by doing It constitutes a DC power supply, and with only the switch control unit of the inverter, it is possible to control the DC current source, perform AC conversion, and control the DC output voltage and current, and solve each of the above problems.

[0035] FIG. 5 shows a specific circuit configuration for obtaining an insulated and controllable DC output from a single-phase power supply according to the present invention as an AC power supply.

[0036] In the figure, an LC filter circuit (300) is connected to the DC side of the rectifier circuit (200) of the diode bridge circuit 1, and the DC voltage of the filter capacitor C a from inductor period through to the inverter circuit circuit is connected to the current control type By the switch control of the inverter, the magnitude of the current source the short-circuit energization period for controlling controls the energization period of the current flowing to the AC side, and the amount converted to an appropriate voltage and current by the turns ratio of the transformer (500) is rectified by the rectifier circuit (600) of the diode bridge circuit 2 circuit and smoothing capacitor period to constitutes a DC power supply together with the rectifier circuit (600) and is connected to a DC load (800).

[0037] FIG. 6 shows the AC-DC power supply circuit of the present invention when the LC filter circuit is connected to (a) the AC power supply line and (b) the AC power supply line with an inductor the DC output of the rectifier circuit and a capacitor connected to the line.

[0038] ​​ In any of the configurations of FIGS. 5 and 6, the AC power line of inductor is L C filter circuit including the inductance L of is handled can be obtained .

[0039] The above shows the main circuit configuration of the AC-DC power supply for a single-phase AC power supply. The main circuit configuration for a three-phase AC power supply is shown in FIG. 7. When a three-phase power supply is connected, the diode bridge circuit and the AC filter circuit become three-phase, but the rest can be configured in exactly the same way as the single-phase circuit configuration.

[0040] Now, FIG. 8 shows the current i of inductor Ld when switch signals shown in the figure are applied to switches S1 to S4 in the AC-DC power supply shown in FIG. 5 at a frequency sufficiently higher than the frequency of the AC power supply Ld and the primary-converted current i of the load current flowing through the transformer and the rectifier circuit d1 and its average current I d1 showing the basic operation waveforms.

[0041] When switches S1 and S3 or switches S2 and S4 are energized, the inverter is in a DC short-circuit state and current flows from zero, so the voltage applied to the inductor to the inverter is e ad and when that happens, the current i of the inductor Ld is a current that increases in a ramp-like waveform as shown by the following equation i Ld =(e ad / L d ) t ---------------(1) and a current with a waveform that increases in a ramp-like manner as shown flows, The current flow rate as a ratio of the DC short-circuit period of the inverter, the switching period T s Let t = αT s The current becomes maximum at this point in time

[0042] And When switches S1 and S4 or switches S2 and S3 are energized, the current path flows through the transformer to the DC load terminal, and the primary-converted value i of the load current to the DC capacitor C d tod1 is e d1 as the primary converted value of the DC load terminal voltage e d decreases as shown in the following equation. i d1 =(e ad / L d ) *αT s -[(e d1 -e ad ) / L d t---------------(2)

[0043] Figure 9 shows the relationship between the control operation waveforms of the AC-DC DC power supply between the AC power supply and the DC output with respect to this current control waveform.

[0044] Here, as the switching operation of the inverter , the power supply voltage the is sufficiently compared to the source period Ta short The switching period T s shows the operation waveform when constant current width control is applied.

[0045] Here, since the cut-off frequency of the LC filter that cuts the switching harmonic component is sufficiently high with respect to the power supply frequency, the influence on the AC power supply waveform is small. If the effective value of the AC power supply voltage is Ea and the power supply angular frequency is ω, it can be approximated by the following equation. ad e e ad =| / 2 E a sin ωt | ---------------(3)

[0046] Therefore, the current i Ld flowing through the inductor reaches its maximum value at t = αT, and the peak value is given by the following equation i Ld (αT s )= (e ad / L d )*αT s =(| / 2 E a sin ωt | / L d )*αTs ---------------(4) It becomes as shown, and the current waveform is proportional to the absolute value waveform of the AC power supply voltage e a and becomes a current waveform proportional to the absolute value waveform of the AC power supply voltage e

[0047] Therefore, alternating current power supply current i a the peak value i in units of the switching period ap is As shown in Fig. 9, the current i flowing through the inductor Ld has a waveform in which the positive and negative reverse every half cycle of the power supply, and becomes a sine waveform in phase with the AC power supply voltage as shown by the following equation, i ap =( / 2 E a αT s / L d ) sin ωt ---------------(5) the alternating current power supply current i excluding the switching harmonic components a also becomes a sine wave shown by the dotted line in Fig. 8

[0048] On the other hand, the current i of the transformer inv is the current i when the current i of the inductor Ld falls. The current i d1 is switched every half cycle of the power supply by the switching operation of the inverter and becomes the current waveform shown in Fig. 9. The current i ds which is absolute value converted by the diode bridge connected to the secondary side by current transformation in the transformer flows into the DC capacitor C dc .

[0049] Here, the DC current i ds is given by the quantity converted by the turns ratio of the transformer used in the current waveform i d1 shown by equation (2). i ds =(N1 / N2)*i d1 =(N1 / N2){(e ad / L d ) *αT s -(e d1 -e ad ) / Ld ) t}---------------(6) Here, t is in the range where (t <= (1-α)T s ) and becomes the current waveform until the current becomes zero.

[0050] The maximum value of this current waveform is the value obtained by secondarily converting the maximum value of the inductor current, and the waveform excluding the switching frequency component is shown in FIG. 8 of current i ds The average value of is represented by a dotted line shown by and becomes the absolute value waveform of a sine wave.

[0051] Therefore, the DC capacitor C d needs to be of a large value that can sufficiently smooth the large current pulsation waveform based on twice the power supply frequency.

[0052] At this time, the DC load voltage e d , current i d becomes almost a constant value by the large DC capacitor C d using .

[0053] When the AC power supply is three-phase as shown in FIG. 7, the pulsation of the output voltage waveform of the diode bridge rectifier circuit becomes small, so the value of the DC capacitor C d can be kept small.

[0054] Also, the inflow current waveform i a from the AC power supply in this case becomes a waveform with a conduction width of 120 degrees proportional to the rectified power supply voltage waveform as if a resistive load is connected to the rectifier circuit.

[0055] If the intermediate high-frequency transformer used in the AC-DC power supply of the present invention is almost an ideal transformer, it can operate without problems, but in an actual transformer, due to the influence of winding resistance and leakage inductance it is necessary to consider

[0056] When using a practical transformer, in particular, the leakage inductance causes overvoltage during the inverter's switch switching, which becomes an issue and countermeasures are essential.

[0057] This problem shown in Fig. 3 is the same for AC-DC power supplies using flyback transformers therefore, in this case, Since the capacity of the device is relatively small, countermeasures using an RC snubber circuit are taken.

[0058] In the case of the AC-DC power supply of the present invention, when the capacity is small, countermeasures using an RC snubber circuit can be considered. However, when the capacity becomes large, the snubber loss becomes a problem, so fundamental countermeasures are required.

[0059] Here, we will consider the influence of this leakage inductance on the inverter operation using the equivalent circuit shown in Fig. 10.

[0060] In this figure, current control type the inverter circuit and diode bridge rectifier between circuits the transformer inserted into to is shown only with the leakage inductance that has a large influence.

[0061] Fig. 11 shows the current paths in the four operating modes according to each switch signal of the inverter shown in Fig. 8, the current path at the commutation time shown , and the high pulse voltage e s1 applied to the switch element S1 leakage inductance l o the current i flowing through the inductor to Ld it can be seen that it is due to

[0062] As the current paths in the four operating modes, there are a DC short-circuit mode ((1), (3)) by the inverter and a power supply mode to the load ((2), (4)). The voltage e s1 applied to the switch element S1 is, at the commutation time from (1) to (2), the current i d flowing through the inductor L Ld is applied to the leakage inductance, so e s1 = e d1 + e l = (N1 / N2)E d + l o (di Ld / dt) ---------------(6) As shown, in addition to the primary - side converted voltage e of the DC load voltage, it can be seen that a large voltage e due to the leakage inductance of the transformer is applied. d1 In addition to the primary - side converted voltage e of the DC load voltage, it can be seen that a large voltage e due to the leakage inductance of the transformer is applied. l is applied.

[0063] When changing from this operation mode (2) to the DC short - circuit mode (3), even if the current flowing through the leakage inductance is not zero, different from the switch circuit constituting the current - type inverter, since the current path is ensured by the free - wheeling diode connected to the switching element, there is no problem of in the switch - over from operation mode (2) to operation mode (3).

[0064] Fig. 12 shows the operation waveforms at the time of switch - over considering the influence of the leakage inductance of the transformer. It can be seen that each time the operation mode changes from the DC short - circuit mode to the power - feeding mode to the load, a large voltage due to the leakage inductance is applied to the switching element.

[0065] Transformer of As a countermeasure for the commutation energy associated with the leakage inductance of the transformer, first of all, it goes without saying that it is necessary to manufacture the transformer by a winding method that suppresses the generation of leakage inductance as much as possible. Even if the leakage inductance can be reduced, countermeasures become indispensable when the current is large

[0066] As a countermeasure for the processing of the energy at the time of commutation, by adding a simple circuit that absorbs the energy into the snubber capacitor at the time of commutation, the generation of over - voltage to the switching element can be suppressed, but if it is consumed by the snubber resistor, it will cause large heat generation and a decrease in efficiency.

[0067] Therefore, as a fundamental countermeasure for the commutation energy associated with the transformer leakage inductance, it is conceivable to transfer the commutation energy to the power supply side or the DC load side.

[0068] In the case of the latter, it is conceivable to transfer it to the DC load side in an insulated manner using a flyback DCDC converter or the like, but the circuit configuration becomes complicated.

[0069] Figure 13 is Figure 4 of With respect to the basic control block of the present invention, the commutation energy associated with the leakage inductance is current control type inverter circuit to the DC power supply side of returning excessive a voltage protection circuit is added.

[0070] Figure 14 shows the main circuit configuration of an ACDC DC power supply with a protection circuit added to return the commutation energy associated with the leakage inductance to the DC power supply side of the inverter circuit by means of a buck chopper. current control type

[0071] Figure 15 shows the electrical control operation waveform during the switching control of the inverter when an overvoltage protection circuit is added. Focusing on the commutation when switching from the DC short - circuit mode to the power - feeding mode to the load, As shown in Fig. 14 the current i overvoltage protection flowing into the capacitor of the buck chopper circuit b shunts the current i to flowing through the inductor Ld so that the power - feeding current i by doing to the load does not rise suddenly, and it can be seen that the excessive voltage rise in the leakage inductance is suppressed. d1

[0072] Note that the voltage v z of the capacitor C z shunted to the buck chopper circuit can be controlled to a set maximum allowable voltage the following constant value by controlling the current - passing rate of the buck chopper circuit.

[0073] Next, as shown in FIG. 9, in the AC-DC power supply of the present invention, since the DC output current waveform is a sawtooth-like pulse current with an inverse direction, there is a concern about an increase in circuit loss due to a large amplitude of the pulse current with respect to the DC average current. Also, the DC-side current waveform of the inverter also becomes a triangular wave starting from zero current.

[0074] The AC-DC power supply of the present invention equipment When attempting to increase the capacitance, for the current source simply directly parallelize the configurations of the inverter, transformer, and rectifier circuit section, easily a multiplexed configuration can be achieved, the sawtooth wave and the problems associated with to pulsed current can be resolved.

[0075] The AC-DC power supply of the present invention source Multiplexed configuration constituting By doing so, the parallel redundancy increases, and an improvement in reliability can be expected, and the design of increasing the capacity of the device also becomes easier.

[0076] FIG. 16 is a block diagram of the main circuit configuration when the AC-DC power supply of the present invention is configured in a dual configuration. The buck chopper control section for overvoltage protection due to leakage inductance can be shared. can do and It can also serve as not only a dual configuration but also a multiplex configuration

[0077] FIG. 17 shows the current control operation waveforms during the dual configuration of the AC-DC power supply of the present invention. In order for the two inverters, transformers, and rectifier circuit sections to operate with a 90-degree phase difference, the DC current waveform i Ld rectified from the AC power supply has the peaks and valleys of the two currents canceled out compared to the triangular wave single operation, resulting in an almost constant current waveform, and the DC load current waveform i d also the reverse sawtooth wave-shaped has a pulse current that is twice as large so the amplitude value is suppressed as that in the single operation, and it can be seen that the current waveform has less pulsation.

[0078] Also, there is an advantage that the amplitude of the pulse current i d with respect to the magnitude of the DC output current I ds can be reduced in inverse proportion to the number of multiplexing.

[0079] Note that, for the current control type AC-DC power supply of the present invention the basic switch Since it operates as a boost operation, when the operating voltage on the AC side of the inverter is low moreover, the DC operating voltage of the inverter becomes low In the case, there is no boost operation can be achieved Therefore, it cannot operate normally.

[0080] For the present invention current control type The AC-DC power supply has an AC power supply voltage high DC output voltage even when low The operating voltage on the AC side of the inverter is the transformation ratio it can be made to work by increasing it by (N1 / N2) .

Advantages of the Invention

[0081] The advantages of the current control type AC-DC power supply of the present invention are listed below. 1) Current control type By only the switching control of the inverter, without configuring a special current control system The inflowing current can be made to work as a sine wave current proportional to the AC power supply voltage. 2) Current control type By operating the inverter at a high frequency, for voltage level conversion and insulation for Transformer can be miniaturized Device to It can be made smaller and lighter. 3) Current control type By only the switching control of the inverter, a DC power supply with a high power factor can be obtained, and the configuration of the control system is simple. 4) Current control type Since the switch circuit of the inverter constituting the inverter can be a switch circuit of a voltage type inverter configuration The voltage drop of the switch circuit can be made lower than that of the switch circuit of a general current type inverter, and a current path for the inductive load current can be ensured. 5) Current control type Since the current source is supplied to the load side by the inverter, it also operates as a current source against a load short circuit, so current protection is easier than that of a voltage type device. 6) Since a transformer is interposed, current controltype Although the basic operation of the inverter is a boost operation, by appropriately setting the transformation ratio, there is no limitation in setting the DC output voltage. 7) Since the DC output is a current source, current control type The inverter, transformer, and diode bridge rectifier circuit section can be connected in parallel, and a multiplexing configuration is extremely easy. 8) The parallel redundancy due to the multiplexing configuration increases, and an improvement in reliability can be expected, and the design of increasing the capacity of the device is also facilitated. 9) Due to the multiplexing configuration, current control type The amplitude of the pulsating current on the DC side of the inverter and the power supply pulsating current to the DC smoothing capacitor can be suppressed, and the pulsation of the switching component can be reduced. 10) The commutation energy due to the leakage inductance of the transformer is returned to the type DC power supply of the inverter side By doing so, overvoltage protection can be applied without significant losses. 11) When the AC power supply is a three-phase power supply, an AC-DC power supply that obtains a DC output from the three-phase power supply can be easily configured only by three-phasing the three-phase bridge rectifier circuit and the AC filter circuit section. 12) Even when the AC power supply is a three-phase power supply, the AC current waveform becomes the waveform when a resistive load is connected to the three-phase rectifier circuit, and it can operate at a high power factor without adding special control.

Brief Description of the Drawings

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[0083] FIG. 18 shows a control block diagram of an AC-DC power supply device of the present invention, in which control blocks for a control loop for controlling DC output voltage and current and an overvoltage protection control loop are added to the basic configuration block diagram of the AC-DC power supply shown in FIG.

[0084] As an embodiment of the current-controlled AC-DC power supply of the present invention, a voltage Control System not limited to Control can be achieved using only the current control loop, and furthermore, it is also possible to implement control using only the inverter conduction width control.

[0085] Also, if the leakage inductance of the transformer is small enough to be ignored, it can be implemented by adding an RC snubber circuit without using a special overvoltage protection circuit.

[0086] The control operation of the current-controlled AC-DC power supply of the present invention is under the following conditions This will be confirmed through simulation analysis.

[0087] The circuit constants for the simulation analysis of the current-controlled AC-DC power supply of the present invention are the LC filter constants of the rectifier circuit section connected to the AC power supply is , La = 1 mH, Ca = 1 uF. The inductor constituting the current-type inverter is Ld = 100 uH. The primary and secondary leakage inductances of the high-frequency transformer are l o1 = 5 uH, l o2 = 5 uH. The turns ratio (N1 / N2) is 1 when the DC reference voltage E dr is 500 V or more set as, E dr is and 2 when it is as low as 300 V. The smoothing capacitor connected to the diode bridge rectifier circuit is Cd = 4000 uF, and the DC load resistance is Rd = 250 ohm.

[0088] Also, as the operating conditions for the simulation analysis of the current-controlled AC-DC power supply of the present invention, the operating frequency of the inverter is set to fs = 40 kHz, the single-phase power supply voltage is Ea = 200 V, also the three-phase power supply voltage (line-to-line) is Ea = 200 V, alternating current power supply the frequency is fa = 60 Hz, and the DC reference value Edr = 500 V as The control operation was confirmed. (1) Basic control operation of the AC-DC power supply

[0089] Fig. 19 shows the switching operation waveforms of each part when a single-phase AC voltage Ea = 200 V is applied and the DC reference voltage Edr = 500 V. Fig. (a) in the figure shows the operation waveforms of each part in units of the AC power supply cycle, and Fig. (b) in the figure shows the enlarged operation waveform of the switching control near the maximum value of the AC power supply voltage.

[0090] It is confirmed that by the switching control of the current-controlled inverter, the reverse sawtooth-shaped pulse current waveform is subjected to a current conversion operation by the high-frequency transformer, the secondary output is rectified by the diode bridge circuit, and is smoothed by the DC capacitor to obtain a constant DC voltage and current. (2) Control operation by the DC reference voltage

[0091] Figure 20 shows the results when the DC reference voltage Edr = 300V, set low and Fig. (a) of this figure shows the results when the turns ratio N1 / N2 = 1. The DC output voltage e converted to the primary side of the transformer d1 is lower than the rectifier circuit voltage e of the AC power supply ad in the operating range, resulting in a boost control operation failure and waveform distortion.

[0092] In contrast, Fig. (b) of this figure shows that by setting the turns ratio to N1 / N2 = 2, the DC output voltage e converted to the primary side of the transformer d1 is doubled to , indicating that it can operate normally. (3) Overvoltage protection Circuit operation

[0093] Next, Fig. 21 shows a comparison of the presence or absence of overvoltage protection circuit operation when the high-frequency transformer has leakage inductances of l o1 = 5uH and l o2 = 5uH under the same operating conditions as in Fig. 19.

[0094] Focusing on the voltage e applied to the switch S1 that constitutes the inverter, Fig. (a) of this figure shows the operating waveform when the overvoltage protection circuit is not operating s1 , and it is confirmed that a voltage as high as several kV is applied to the switch element S1, while the voltage applied to the switch S1 in Fig. (b) of this figure when the overvoltage protection circuit is operating is maintained at the set reference voltage V is z = 800V, indicating that the overvoltage protection circuit using a buck chopper functions effectively.

[0095] Fig. 22 shows an enlarged view of the switching control operation waveform to confirm the overvoltage protection control operation. An overvoltage is applied to the switch element S1 when switching from the DC short-circuit mode by the inverter to the power supply mode to the load, but the operating waveforms in other intervals of are almost confirmed to be the same.

[0096] ​In Fig. (a), a spike-like extremely high voltage waveform is confirmed at the moment of commutation. However, in Fig. (b) where the overvoltage protection control operation is activated, the overvoltage does not occur due to the current i b flowing through the overvoltage protection circuit, set as the reference value and it can be confirmed that it can be controlled to a constant value. (4) Operating waveforms due to the arrangement of the LC filter

[0097] Fig. 23 shows the arrangement of the LC filter which is the return destination of the commutation energy of the overvoltage protection circuit. Fig. (a) shows the LC filter on the AC side, and Fig. (b) shows the switching control operation when the inductor L a is on the AC side and the capacitor C a is on the DC side. waveform This is the case.

[0098] Although there are some differences in the control operation waveforms depending on the arrangement of the LC filter circuit, it can be confirmed that the basic operation as an AC-DC power supply remains unchanged, no overvoltage occurs, and it can be stably controlled. (5) Operating waveforms during dual configuration control

[0099] Next, Fig. 24 shows the switching control operation waveforms when the inverter, high-frequency transformer, and rectifier circuit section of the AC-DC power supply of the present invention are in a dual configuration. The waveform shown in Fig. (a) is an enlarged view of the switching waveform near the maximum value of the AC power supply voltage, and Fig. (b) shows that the pulsations of the current waveform i Ld flowing through the LC filter and the DC output current waveform i d1 after primary conversion are reduced. (6) Operating waveforms for a three-phase power supply

[0100] Fig. 25 shows the operating waveforms of the AC-DC power supply of the present invention for a three-phase power supply. It can be confirmed that the three-phase alternating current waveform i a has a waveform with a 120-degree conduction width and a substantially constant amplitude proportional to the rectified voltage waveform e ad of the three-phase power supply. in This can be confirmed.

Description of symbols

[0101] 100…AC power supply 100 -1...Single-phase AC power supply 100 -2…Three-phase AC power supply 200...Diode bridge circuit 1 200 -1...Single-phase rectifier circuit 200 -2…Three-phase rectifier circuit 300...LC filter circuit 300 -1...AC filter inductor 300 -2...DC filter capacitor 400...Current controlled voltage inverter 400-1...Current source inductor 400-2...Voltage type inverter 500...Transformer 600...Diode bridge circuit 2 700...Overvoltage protection circuit 800…DC load 900...Control circuit 900-1...Output control section 900-2...Overvoltage protection control unit

Claims

1. A rectifier circuit with an LC filter circuit connected to the AC side or DC side or both sides of a diode bridge circuit 1 is connected to an AC power supply, and the DC output of the rectifier circuit is configured with a switch circuit composed of switch elements connected in antiparallel with diodes to form a bridge configuration. An inductor is connected to the DC side of the inverter circuit via an inductor, and the AC output of the current-controlled inverter circuit is connected to a transformer for voltage and current conversion. The secondary-side output of the transformer is connected to the AC side of a diode bridge circuit 2, and a smoothing capacitor is connected to the DC-AC-DC conversion circuit to which a DC load is connected. A power supply configuration is provided, and by controlling the energization ratio of the DC short-circuit operation of the inverter and the power supply operation to the transformer at a frequency sufficiently higher than the frequency of the AC power supply, the voltage and current of the DC load are DC-converted and controlled with high power factor from the AC power supply by current source control. A current-controlled AC-DC power supply characterized by this.

2. In the current-controlled AC-DC power supply according to Claim 1, in order to reduce the voltage spike applied to the inverter during commutation due to the leakage inductance of the transformer, an overvoltage protection capacitor is connected to the DC terminal of the inverter via a diode, and the voltage charged in the overvoltage protection capacitor is stepped down by a buck chopper circuit. The output of the stepped-down control is connected to the DC input side terminal of the inductor of the current-controlled inverter circuit, and the commutation energy due to the leakage inductance is transferred to the DC input side of the current-controlled inverter circuit. By controlling the current conduction ratio of the buck chopper circuit, a current-controlled AC-DC power supply characterized by overvoltage protection control with high efficiency.

3. In the current-controlled AC-DC power supply according to Claims 1 and 2, a plurality of sets of the DC-AC-DC conversion circuits are connected to the rectifier circuit, and their DC outputs are connected in parallel to the DC load in a multiplexed configuration. By multiplexing control in which switching control signals to the plurality of sets of DC-AC-DC conversion circuits act on each other with a phase difference corresponding to the number of the plurality of sets, the operating control characteristics such as an increase in device capacity, an improvement in reliability due to high redundancy, and a reduction in current ripple are improved. A current-controlled AC-DC power supply characterized by this.

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