Method of controlling current type DC-DC converter

Abstract

A general DC-DC converter performs high-frequency voltage conversion of a DC voltage source, performs insulation and conversion into a required voltage and current by a high-frequency transformer, then performs rectification by a diode bridge circuit, and obtains a DC output via a filter circuit, but since it is basically a voltage source output, balance control when the device is configured with a plurality of power supply units becomes complicated.SOLUTION: The present invention is a system in which an inductor current source connected to a DC power supply is subjected to high-frequency current conversion, insulation and conversion into a required voltage and current are performed by a high-frequency transformer, and then a smoothing capacitor is connected to a current source output subjected to DC conversion by a diode bridge circuit to obtain a DC output, and a plurality of power supply units can be easily connected in parallel, and the capacity of the device can be easily increased.SELECTED DRAWING: Figure 13

Description

[Technical Field]

[0001] While conventional DC-DC converters have problems due to their basic voltage source output, the DC-DC converter of the present invention uses a current source output, thereby proposing and applying new control technology intended to overcome previous problems. [Background technology]

[0002] A typical DC-DC converter converts a DC voltage source into a high-frequency voltage, then uses a high-frequency transformer to convert it into the required voltage and current with insulation, then rectifies it using a diode bridge circuit and obtains a DC output through a filter circuit.Because they are small, lightweight, and highly efficient, they are used as DC power sources in a wide range of fields.

[0003] For small capacity applications, a flyback converter or a forward converter or a flyback converter is used, which drives a high frequency transformer from one power source to reduce size and weight. but It is used.

[0004] In addition, it reduces switching control loss and switching noise. of For this purpose, various soft switching control techniques have been introduced and are being put to practical use.

[0005] However, since the range of application of a transformer driven by a single power source is limited in terms of capacity, when the capacity becomes large, a DC-DC converter with a circuit type that generally performs high-frequency conversion using a voltage-type inverter circuit, then converts the secondary voltage to the required voltage and current using a high-frequency transformer, rectifies the secondary voltage using a diode bridge circuit, and obtains a DC output voltage via an LC filter circuit is generally used, and this is widely used in fields with relatively large capacities.

[0006] Meanwhile, with the spread of electric vehicles (EVs), the number of kW onboard chargers and home EV charging stations has rapidly increased to EV charging stations with even higher capacities of around 50 kW.

[0007] These EV charging devices generally consist of an AC-DC converter that converts AC power into DC, and a DC-DC converter that converts the resulting DC power into isolated DC voltage and current.

[0008] First, in the AC-DC conversion section, since the power supply capacity is large, a PFC (Power Factor Correction) converter is used to improve the characteristics of the current flowing into the device and to improve the power factor.

[0009] There are two types of PFC converters: those that convert from a single-phase power supply to DC and those that convert from a three-phase power supply to DC. The former are used in home EV charging devices, while the latter are used in general EV charging stations.

[0010] Next, in the DC-DC conversion section, a transformer is used to provide insulation from the DC power source, but in order to reduce size and weight, the DC power source voltage is made high-frequency by an inverter, and then converted to the required voltage and current level using a high-frequency transformer for insulation, and then converted back to DC by a rectifier circuit, using the DC-DC converter mentioned above.

[0011] As mentioned above, charging equipment for large-capacity EVs and other devices requires an AC power source. to PFC Converter and the resulting DC output Using a high frequency transformer It is configured to obtain the required DC output by isolating it with a DC-DC converter.

[0012] If the capacity of the charging device is not very large, the PFC converter and DC-DC converter circuit are manufactured as an integrated unit, but designing and manufacturing a device of the same capacity as an EV charging station according to specifications not only requires a lot of design effort but also poses problems in procuring materials.

[0013] Therefore, instead of designing and manufacturing according to the specifications of each EV charging station, a method to increase capacity by combining multiple standard 10kW charging power supply units is 、 This leads to reduced production costs and shorter production times, and also increases redundancy, which has many benefits in terms of failures and inspections.

[0014] To achieve this, it is possible to use a power supply unit that integrates a PFC converter and a DC-DC converter, or a power supply unit that consists of only the DC-DC converter.

[0015] The DC-DC converters that make up such power supply units are generally configured to output an isolated DC voltage source via a high-frequency transformer from a DC voltage source, which means that it is not possible to directly connect the voltage source output to a storage battery, and it is not possible to directly connect power supply units with voltage source outputs in parallel. from A current control system is required, which makes the control system more complicated.

[0016] This invention solves the essential problem of voltage source output in conventional DC-DC converters by configuring the DC-DC converter with a current source. Solved It is something that we try to do. [Prior art documents] [Non-patent literature]

[0017] [Non-Patent Document 1] Matsuse and Saito, "Power Electronics", Institute of Electrical Engineers of Japan, pp.35-36, p.158, p.112, 2000. [Patent documents]

[0018] [Patent Document 1] Patent No. 6328506: "Control device for AC / DC converter" [Patent Document 2] Patent Publication No. 2021-141738: "Multiple power conversion control systems" [Patent Document 3] Patent application 2006-6042: “DC power supply device” [Patent Document 4] JP 2024-54936: "DC-DC converter and charging device" [Patent Document 5] Patent No. 7452920: "Current-controlled AC-DC power supply" Summary of the Invention [Problem to be solved by the invention]

[0019] Figure 1 shows the basic configuration of a typical AC-DC converter, in which an AC power source is converted to DC using a PFC converter, the DC voltage source is converted to high frequency using a voltage-type inverter, and then insulated using a high-frequency transformer. The output converted to the required voltage is then converted to DC using a rectifier circuit and connected to a DC load via a filter circuit.

[0020] Here, if the output of the voltage converter is a voltage source, but The voltage source is the battery. directly There are some issues that cannot be connected.

[0021] where: It is possible to consider whether to use only a DC-DC converter as a power supply unit (DC-DC UNIT C), or to use a power supply unit (AC-DC UNIT C) that includes a PFC converter that forms the DC power supply section of the DC-DC converter.

[0022] Figure 2 shows how multiple power supply units (DC-DC UNIT C) are connected in parallel to increase the current capacity. Let, The circuit configuration for connection to a storage battery is shown.

[0023] When multiple voltage source output power supply units are connected in parallel, even a slight voltage difference too Because a large current flows, proper load current sharing control becomes an issue.

[0024] This is an issue that arises when connecting a general DC-DC converter to a storage battery or when connecting multiple power supply units (DC-DC UNIT C) in parallel because the DC-DC converter outputs a voltage source, and generally requires a circuit that includes an appropriate inductor at the output of the power supply unit and appropriate current control.

[0025] In addition, even a small DC component generated by a voltage inverter converting high frequency may cause the high frequency transformer to become biased, resulting in a large DC current flowing through the transformer. Therefore, when connecting a voltage source inverter to a high frequency transformer, DC blocking capacitor in series Place etc. Measures are needed to This is also a major challenge.

[0026] FIG. 3 shows the basic configuration of an AC-DC converter constructed by connecting a PFC circuit to a DC-DC converter according to the present invention.

[0027] The DC-DC converter of the present invention converts the DC power source obtained by the PFC converter into a current source at a high frequency using a hybrid current-source inverter (described later), and insulates it using a high-frequency transformer. , changing current The secondary current is rectified to produce a DC current source output. as It is configured to be connected to a DC load.

[0028] and , the output of the rectifier circuit Connect a capacitor to By doing so, the inverter switch control Due to the inductive component of the AC circuit In addition to suppressing overvoltage, it can provide a smooth DC output as an independent voltage power supply.

[0029] Here, the power supply unit containing only the DC-DC converter in this case will be called (DC-DC UNIT A), and the power supply unit including the PFC converter, which is the DC power supply section, will be called (AC-DC UNIT A).

[0030] Figure 4 shows Multiple units The circuit configuration shows power supply units (DC-DC UNIT A) connected in parallel to increase the current capacity and connect to a storage battery.

[0031] This new DC power supply unit has a current source output, so even if a storage battery is directly connected, excessive current will not flow. Also, even if multiple power supply units are connected in parallel, they can be operated with the current output controlled by each power supply unit. Can The device capacity can be increased without balancing between the power supply units. easily It can be increased.

[0032] Furthermore, the DC-DC converter of the present invention 、 Because the current source is connected to a high-frequency transformer, there is no problem of DC bias magnetism in the transformer, unlike in general DC-DC converters.

[0033] (Non-Patent Document 1) shows combinations of voltage-source inverters connected to voltage sources and current-source inverters connected to current sources, as well as typical loads that are compatible with them. Voltage-source inverters are generally used with an inductive load in which an inductor is connected in series to the load, and current-source inverters are used with a capacitive load in which a capacitor is connected in parallel to the load.

[0034] Figure 5 shows the general current-source inverter circuit configuration. and Combining a current source using an inductor and a voltage-type inverter Ta Hybrid Current Source Inverter of 1 shows a circuit configuration.

[0035] Figure (a) shows the circuit configuration of a general current-source inverter, which is used by connecting a capacitor to the AC load end, while Figure (b) shows This is the circuit configuration of a hybrid current-source inverter. , Adjustment A voltage-type inverter circuit is connected to a current source using an inductor, assuming that a capacitor is connected to the load end of the current circuit. It is composed of:

[0036] In a voltage-type inverter, a switch circuit in which a diode is connected in antiparallel to the switch element is used to ensure a current path for the inductive load current when the switch is turned off. However, In a current-source inverter, the voltage of the capacitor is applied to the switch as a reverse voltage when the switch is switched. Therefore, a switch element with reverse voltage resistance is required. or A switch circuit is used in which a diode is connected in series to a switch element.

[0037] For this reason, in general, current-source inverters generally have a switch configuration that provides reverse voltage resistance to the switch circuit, compared to the switch configuration used in normal voltage-source inverters. teeth Diodes are connected in series. To , the switch circuit becomes more complex do but also Added The conduction loss due to the diode increases.

[0038] but 、 In the hybrid current source inverter according to the present invention, a capacitor is connected as an AC load via a diode bridge rectifier circuit. element No reverse voltage is applied to

[0039] Therefore, in a hybrid current-source inverter circuit consisting of a reverse-conducting diode and a switching element, For prevention Diode switching element in There is no voltage drop problem.

[0040] In addition, In a hybrid current-source inverter circuit, Problems caused by leakage inductance in the high-frequency transformer connected to the inverter are an issue, but can be resolved by adding a simple snubber circuit or overvoltage suppression circuit as described below.

[0041] FIG. 6 shows the main circuit configuration of the DC-DC converter of the present invention. 、 The following is a description of the prior art cited here.

[0042] (Patent Document 1) is a general It is an AC-DC conversion power supply The output from the AC power supply is converted to DC by a PFC converter, and then converted to high frequency by a voltage inverter, and the required DC output voltage is obtained by isolating it using a high frequency transformer. circuit This configuration is intended to improve the PFC control method.

[0043] (Patent Document 2) configures a diode rectifier connected to a high-frequency transformer using a PWM converter. death, It consists of multiple power supply units to increase the capacity of the device. bidirectional Power System In This is intended to improve reliability and redundancy in the event of a partial failure.

[0044] In (Patent Document 3), when DC load voltage and current are controlled by controlling the inductor current with a step-down chopper and diode rectifying it via a transformer in an inverter, the stomach Based on voltage detection to prevent damage to the element current It is a DC power supply device intended for control.

[0045] In this paper, the AC load of the inverter used as A capacitor is connected to the DC output of the diode bridge rectifier circuit. but Connected The inverter circuit is A switch circuit that does not have reverse voltage resistance is used.

[0046] Therefore, the current path due to the leakage inductance of the transformer is not secured when switching. Inverter circuit There is a concern that a spike voltage may be applied to the switch element.

[0047] (Patent Document 4) is a charging device High efficiency, Higher output with the aim of This is related to the development of a resonant three-phase LLC DC-DC converter, but there is concern that the circuit configuration will become complicated due to the capacitor and inductor circuits being connected to the output of the high-frequency inverter.

[0048] (Patent Document 5) describes the configuration of an AC-DC converter. In The output waveform that has been full-wave rectified by a diode bridge circuit is converted to high frequency and a capacitor is connected to the output of the rectifier circuit to obtain a DC output. of Pulse width control allows for a simple configuration that does not require the configuration of a typical PFC converter, and provides a sinusoidal current function proportional to the power supply voltage. While DC power supply control is possible.

[0049] The high frequency conversion section is the same as the DC-DC converter of the present invention. character Although the circuit configuration is similar, (Patent Document 5) achieves the above-mentioned excellent characteristics under discontinuous current control. And, As the device capacity increases, discontinuous Pulse Current Therefore, There are concerns that this will increase current loss in the circuit and cause noise issues, so stand It is not suitable for large capacity conversion devices such as I'm do not have.

[0050] In the DC-DC converter of the present invention, 、 Although it may operate with discontinuous current when under light load, it operates with current continuous It operates in pulse current mode. flows Therefore, the operating efficiency is low. improved, The impact of switching noise on peripheral devices can also be reduced. Because it is possible, It is suitable for controlling the configuration of large-capacity EV battery charging equipment, etc. [Means for solving the problem]

[0051] Conventional DC-DC converters output voltage, so they are used to connect voltage sources together, such as with storage batteries or in parallel. When The problems that arise, such as DC bias magnetism in high frequency transformers, are caused by conversion control using a voltage source, and the present invention can solve these essential problems by controlling the conversion of a DC-DC converter using a current source.

[0052] Figure 6 shows The current source inverter of the present invention is a hybrid current source inverter that adds a high frequency transformer for isolation and voltage / current conversion to the output of the hybrid current source inverter. This is the basic circuit configuration of a DC-DC converter, and it is connected from a DC voltage source (100) to an inductor L b The AC output of the hybrid current-source inverter circuit (400) is connected to the high-frequency transformer (500), and the isolated secondary current is connected to the rectifier circuit and the capacitor C d The circuit is configured such that a DC output obtained by a rectifier circuit section (600) connected to the DC load (800) is connected to the DC load (800).

[0053] Figure 7 andFigure 8 shows the inductor L b 1 shows the operating waveforms of the DC-DC converter in response to the switching signals of the hybrid current-source inverter when the current is discontinuous and continuous.

[0054] Figure 7 shows the inductor current i Lb is the operating waveform when discontinuous, and Figure 8 is the operating waveform when continuous.

[0055] The switch operation includes DC short circuit operation by switches S1 and S3 or switches S2 and S4, and power supply operation to the high frequency transformer by switches S1 and S4 and switches S2 and S3. By controlling the ratio of the DC short circuit operation and power supply operation period, the inductor current i Lb is controlled.

[0056] Then, by alternately operating the switches S1, S4 and the switches S2, S3, a high frequency AC current i t1 is sent to the secondary side by a high frequency transformer, and the AC current i on the secondary side is transformed by the transformation ratio. t2 is rectified by a diode bridge circuit and the output current i ds is smoothed by a DC capacitor to produce a DC output voltage e d The operation is to obtain the following.

[0057] As a switching control signal for the inverter, unlike the switching control operation of a normal voltage-type inverter, a high-frequency ON signal is given to the switches S1 and S2 every half cycle, and the switches S3 and S4 are turned ON every half cycle with a phase difference α with respect to the signals of the switches S1 and S2. ,off Give a signal By doing so, Inductor current control and DC output current control can be applied.

[0058] The inductor current i Lb Whether the inductor L b value and switching frequency f s Not only depending on the load condition tooHowever, if the current becomes discontinuous, problems associated with pulse current will occur, so If the device capacity is large, To be able to operate in as continuous a region as possible Need to design .

[0059] Inductor current i Lb Compared to the discontinuous operation region, by operating in the continuous region, the current pulsation from the DC power supply is suppressed, and the waveform of the DC output current pulse becomes a current waveform with a nearly constant amplitude and a controlled conduction width, and the DC output current i ds The pulsation of the pressure can also be significantly reduced.

[0060] Also, high frequency transformers for , inverter-controlled current i t1 When a voltage is applied to operate a transformer so that may occur in There are also other advantages, such as essentially no problems with biased magnetism, and no need to use a DC blocking capacitor.

[0061] On the other hand, in the hybrid current source inverter of the DC-DC converter of the present invention, if there is leakage inductance in the high frequency transformer, there is a risk that an excessive voltage will be generated in the switching elements of the inverter.

[0062] To confirm this operation, FIG. 9 shows a linearly transformed equivalent circuit that takes into account the influence of the leakage inductance of the high-frequency transformer.

[0063] Figure 10 shows this circuit In This is the operating waveform when switching control of the hybrid current source inverter is applied, and shows the operation mode from the short circuit mode of the inductor current by the inverter to the power supply operation mode to the high frequency transformer. When migrating , the inductance current suddenly increases to the leakage inductance. Because it tries to flow Exceeding the withstand voltage of the switch element El There is a concern that excessive spike voltages may occur.

[0064] To suppress the occurrence of this spike voltage, it is necessary to design the high frequency transformer so that its leakage inductance is reduced as much as possible. importantHowever, Leakage inductance Even if the inductor current is small, if it becomes large, the occurrence of a spike voltage is unavoidable.

[0065] This spike voltage appears in the voltage between the DC terminals of the inverter, so a snubber capacitor that absorbs the overvoltage is connected between the DC terminals of the inverter, and the energy stored in the snubber capacitor is consumed by a resistor, or the DC power supply is Regeneration This can be considered as a countermeasure.

[0066] Figure 11 teeth, These are examples of overvoltage suppression circuits caused by leakage inductance in a high-frequency transformer. Figure (a) uses a braking resistor, while Figure (b) connects a step-down chopper circuit to prevent the voltage of the snubber capacitor from exceeding a set value. Both are connected to the DC voltage source side.

[0067] Figure 12 shows the operating waveforms when the step-down chopper circuit of Figure 11(b) is used to suppress the occurrence of spike voltages to a constant set voltage Vz. Although the circuit configuration is more complex than when consumption is via a resistor as in Figure 11(a), it is possible to regenerate power to the DC power supply, thereby suppressing the occurrence of overvoltage without incurring any essential loss.

[0068] If the circuit loss is small enough that the spike voltage can be dissipated by a resistor, the circuit configuration shown in Figure 11(a) is simple and sufficient. However, as the device capacity increases, the loss also increases, so the circuit configuration becomes a little more complicated. essential Lossless step-down chopper in Figure 11(b) Regeneration using The circuit will be selected.

[0069] In particular, when the device capacity is large and it is composed of multiple power supply units, the step-down chopper shown in Figure 11(b) is Regeneration using circuit Department shared By doing so, Suppression of overvoltage The circuit can be simplified.

[0070] FIG. 13 shows the present invention byThis is a control system that functions as a DC-DC converter power supply unit, and the control system is selectively controlled for a) general power supply loads that require constant, stabilized voltage control, and b) constant voltage battery loads.

[0071] First, in the case of a general power supply load, the load terminal voltage e d is detected and a constant reference voltage E dr Compared with the current reference value I dr generates a DC load current i d The system is configured to control the phase α of the inverter via a current regulator so that the phase α coincides with this current.

[0072] Next, in the case of a constant voltage battery load, the load terminal voltage is It depends on the battery voltage , without paying attention to the load terminal voltage, the current reference I dr DC load current i d The inverter phase α is controlled so that This controls the power supply rate to the high frequency transformer. By doing so current This is the system configuration that controls it.

[0073] Next, FIG. 14 shows a DC-DC converter according to the present invention. Using By connecting multiple power supply units in parallel, of This shows a circuit configuration with increased capacity.

[0074] The power supply unit of the DC-DC converter according to the present invention has a current source output, so it can be standardized without performing special balance control between power supply units. was Requires a power supply unit Number Only parallel connection To do in, A power supply device of any capacity can be easily configured.

[0075] In addition, the standardized power supply unit as , The DC-DC converter of the present invention PFC Converter Department Including composition Or The standardized parallel capacitance of the DC-DC converter of the present invention is equal to or greater than the standardized PFC converter section The configuration should be such that It is possible that:

[0076] FIG. 15 shows the circuit configuration when the DC-DC converter of the present invention is used as an actual device. When used as a storage battery charging circuit, a small join Inductance L d of Insert as needed or by connecting a small vibration suppression resistor in series with the capacitor. as needed You need to connect.

[0077] Furthermore, to prevent the occurrence of surge voltages due to leakage inductance of the high frequency transformer, it is necessary to connect a snubber circuit or an overvoltage suppression circuit as shown between the DC terminals of the inverter.

[0078] FIG. 16 shows an example of the circuit configuration of a storage battery charging device configured by connecting a PFC converter from an AC power supply to the DC power supply of this DC-DC converter circuit.

[0079] Generally, the DC power supply for the DC-DC converter circuit of the present invention is The charging device is for home use Scale In this case, a single-phase PFC converter circuit but, For large capacity devices such as EV charging stations, a three-phase PFC converter circuit is required. but It will be used. [Effects of the Invention]

[0080] The characteristic effects of the current-source DC-DC converter of the present invention are listed below. 1) A high-frequency transformer can be used to obtain a DC output that is isolated from the DC power supply. 2) Because the transformer is operated by a high-frequency inverter, the DC-DC converter including the high-frequency transformer can be made smaller and lighter. 3) The present invention current type The DC-DC converter operates as a step-up converter, but the transformation ratio of the high-frequency transformer determines the of The voltage control operating range can be widened. 4) Compared to the circuit configuration of a general current-source inverter, The hybrid current source inverter isThe voltage drop in the switch circuit can be kept low. 5) The present invention current type DC-DC converter teeth, By making the inductor current operate in the current continuity region, Pulse current loss that occurs during discontinuous current operation can also be reduced. 6) The present invention current type The DC-DC converter can also significantly reduce DC input current pulsation and output current pulsation by operating the inductor current in the continuous current region. 7) The present invention current type Because the DC-DC converter has a current source output, it is easier to protect against load short circuits than general DC-DC converters. 8) The present invention current type DC-DC converters are high-frequency inverters by Since the transformer is driven by a current source, when driven by a voltage source to This also eliminates the problem of DC bias magnetism that may occur. 9) The present invention current type Since the DC-DC converter has a current source output, the DC outputs of the DC-DC converters that make up the power supply unit can be easily connected in parallel. 10) Multiplexing configuration It is easy Parallel redundancy By increasing This is expected to improve reliability and make it easier to design devices with larger capacities. 11) The present invention current type When using dual DC-DC converters, the switching phase of the two high-frequency inverters can be shifted by 90 degrees to reduce the difference in input and output current. Pulsating current The frequency can be doubled. 12) Current flowing through the leakage inductance of a transformer Switching the switch The commutation energy due to this is not a problem because the voltage source inverter ensures a current path. 13) In a voltage-type inverter, the generation of an overvoltage due to the leakage inductance of the transformer when switching the inductor current circuit can be prevented by using a snubber circuit or Blood Pressure Drop By Choppa DC power supply RegenerationThis can be sufficiently suppressed by adding a circuit that As mentioned above, compared to general DC-DC converters, current type Since the DC-DC converter has a current source output, It is possible to connect to a storage battery and connect the outputs of multiple DC-DC converters in parallel, making it easy to create a parallel multiplexed configuration. For this reason, the present invention current type DDC-DC converter teeth, Single DC-DC conversion As a DC power supply unit or in combination with a PFC converter from an AC power supply AC-DC conversion As a power supply unit, power supply of the equipment Configuration Extremely useful for standardization The present invention The following effects can be expected. [Brief explanation of the drawings]

[0081] [Figure 1] Typical DC-DC converter circuits and DC-DC and AC-DC power supply units [Figure 2] Configuration of a battery charging device using multiple general DC-DC power supply units [Figure 3] Current-source DC-DC-DC converter circuit and DC-DC and AC-DC power supply unit of the present invention [Figure 4] Configuration of a storage battery charging device using multiple current-source DC-DC power supply units of the present invention [Figure 5] Configuration of current-source inverter circuit (a) General current-source inverter circuit and AC filter (b) Hybrid current-source inverter circuit and DC filter [Figure 6] Main circuit configuration of the current-source DC-DC converter of the present invention [Figure 7] Switching operation waveforms of the current-source DC-DC converter circuit of the present invention when the current is discontinuous [Figure 8] Switching operation waveform of the current-source DC-DC converter circuit of the present invention when the current is continuous [Figure 9] A linear equivalent circuit of the current-source DC-DC converter circuit of the present invention [Figure 10] Switching operation waveform during continuous current, taking into account transformer leakage inductance [Figure 11] Examples of surge voltage suppression circuits between DC terminals of an inverter due to transformer leakage inductance (a) Circuit with snubber circuit added (b) Circuit with overvoltage suppression circuit added [Figure 12] Switching operation waveform of the DC-DC converter circuit of this invention when a snubber circuit is added [Figure 13] Main circuit configuration and control system of the current-source DC-DC converter power supply unit of the present invention [Figure 14] Circuit configuration example of a large-capacity power supply using multiple current-source DC-DC converter power supply units [Figure 15] Practical circuit configuration example of a storage battery charging circuit using the current-source DC-DC converter of this invention [Figure 16] Example of a battery charging circuit configuration when using a single-phase PFC power supply as a DC power supply [Figure 17] Simulation circuit and operating conditions of the current-source DC-DC converter of the present invention [Figure 18] Load change characteristics of output voltage and current control system (Edr=400 V) (a) Rd=50 ohm (b) Rd=500 ohm [Figure 19] Overvoltage suppression characteristics due to transformer leakage inductance (a) Characteristics with RC snubber circuit added (R z =5kohm) (b) Characteristics with overvoltage suppression circuit added (V z =500V) [Figure 20] Voltage control characteristics of output voltage and current control system (R d =50 ohm) (a) E dr =500V (b) E dr =200V (a=2) [Figure 21] Charge control characteristics of the battery charge current control system (EB=300V) (a) Idr =20 A (b) Idr=0.2 A [Figure 22] Charge control characteristics of the battery charge current control system (Idr=20A) (a) EB=400 V (b) EB=200 V (a=2) [Figure 23]Equipment capacity expansion circuit using two current-source DC-DC converter power supply units (a) Parallel connection circuit, (b) Series connection circuit [Figure 24] Operating characteristics of increased device capacity using two current-source DC-DC converter power supply units (a) Parallel connection (EB=300V) (b) Series connection circuit (EB=600V) DETAILED DESCRIPTION OF THE INVENTION

[0082] In order to verify an embodiment of a DC power supply device configured with a DC-DC converter circuit of the present invention, Figure 17 Power supply unit main circuit configuration and control system The simulation circuit of The graph is shown together with the operating conditions.

[0083] DC power supply voltage E b = 300V, and the transformation ratio of the high frequency transformer (a = N1 / N2) is the output voltage E d is the DC voltage E b The voltage is set according to the relationship between the voltage and the leakage inductance of the transformer. Overvoltage Adding a suppression circuit Allowable voltage applied to the switching element Voltage V z (V z = 600V).

[0084] Also, the inverter switching frequency is f s = 40 kHz, DC inductor L b Inductance of L from the viewpoint of DC current pulsation b = 500uH, the capacitance of the DC output capacitor Cd is C d =10uF.

[0085] Under the above operating conditions, the DC load is: a) In the case of a resistive load, the DC output constant control loop is activated and the current reference I dr is the output value of the voltage regulator, and b) connect the battery load. In the case of Charging current reference value I drThe inverter switching signal was generated by a current control loop to confirm its operation. (1) DC output voltage constant voltage control operation

[0086] Figure 18 shows the DC power supply voltage E b =300V year, DC output voltage reference value E dr This shows the operating waveforms when the load resistance value is changed under the condition of =400V.

[0087] In the figure (a), the load resistance is R d = 50 ohms, and Figure (b) shows R d = 500 ohms, The present invention DC-DC converters are susceptible to large load changes. too Reference voltage E dr DC output voltage E d =400V Maintain DC reference current I dr The current i d is flowing And, For large load changes too You can confirm that it is working properly.

[0088] Also, Hybrid current source inverter Inductor L b Current waveform i Lb The current during the power supply operation period is Current to the high frequency inverter i t1 , the rectified current of the transformer secondary current i ds The waveform is the law of nature, In Figure 1(a), the inductor current is continuous, resulting in a current waveform with a nearly constant amplitude. Close In Figure (b), the inductor current becomes a discontinuous triangular wave, and the current waveforms in each part change accordingly.

[0089] Figure 19 shows the DC reference voltage E dr = 400V, load resistance is R d = 50 ohms, the operating waveforms are shown to confirm the occurrence of surge voltage due to leakage inductance. There is no significant change in Voltage applied to inverter switch element S1e s There are differences in the peak values.

[0090] Figure (a) shows the snubber capacitor C z = 10uF, resistance R z When a 5kohm RC snubber circuit is added, the suppression voltage is reduced to (V z This shows the operating waveforms when an overvoltage suppression circuit set to 500V is added.

[0091] In the case of the RC snubber circuit shown in Figure 1(a), it can be configured with only a passive circuit, but Voltage applied to the switch element e s of Surge voltage V z is suppressed to about 700V, but this involves power loss (about 40W) in the snubber resistor section, and the surge voltage Vz can be further reduced by lowering the snubber resistance.

[0092] On the other hand, when the overvoltage suppression circuit shown in Fig. 1(b) is added, the snubber capacitor C z The energy stored in is returned to the DC power supply, so basically there is no loss and the set voltage V is higher than the DC power supply voltage. z Keep it to It is confirmed that this can be done.

[0093] Figure 20 shows the DC load resistance R d = 50 ohm, the reference value of the DC output voltage E dr =500V and E dr = 200V, the operating waveforms are obtained by simulation analysis.

[0094] In the DC-DC converter using the hybrid current-source inverter of the present invention, when the transformation ratio of the high-frequency transformer is a, the primary conversion value E of the DC output voltage Ed is d ' (aE d ) can operate when it is higher than the DC power supply voltage Eb, but cannot operate when it is lower.

[0095] Figure (a) shows the DC power supply voltage E b = 300V, DC output voltage reference value E dr The operating waveform when set to 500V is the DC output voltage e d indicates that the temperature is controlled to the reference value.

[0096] In contrast, in Figure 1(b), the reference value of the DC output voltage is set to E dr = 200V, but by setting the transformation ratio a of the high frequency transformer to (a = 2), the primary conversion value Ed' of the DC output voltage Ed becomes (E d '=400V), so it can be seen that the device is operating normally.

[0097] However, the DC load resistance R d = 50 ohm constant, DC output voltage E d is low, the inductor L b It can be seen that the current becomes smaller and the device operates in a state close to discontinuous. (2) Battery charging current control operation

[0098] Figures 21 and 22 show the operating waveforms when a storage battery is connected as a DC load. Figure 21 shows the voltage of the storage battery when E B = 300V, and the current control reference value is changed. Figure 21 shows the results when the battery charging current reference value is I dr = 20A, the battery voltage E B The operating waveforms are shown for 400V and 200V.

[0099] Figure 21 shows the voltage of the storage battery as E B = 300V, the current control reference value I dr I dr =20A to I dr = 0.2A, the current I matched the set DC reference current value Idr in both cases. d It can be confirmed that the charging current can be controlled.

[0100] Figure 22 shows the battery voltage E B The operating waveforms are shown for 400V and 200V.

[0101] Figure 21 (a) and (b) show the voltage E of the storage battery. B is the DC power supply voltage E b The same value as E B =E b = 300V, the duty factor of the inductor current by the inverter is almost 1, and a square wave current flows in the high frequency transformer. Bis 400V, which is higher than the DC power supply voltage Eb, so the duty factor of the inductor current is low and a square wave current including a zero current period flows in the high frequency transformer.

[0102] On the other hand, Fig. 22(b) shows 20 As in (b), the battery voltage is low ( E B = 200V), the result when the transformation ratio a is set to (a = 2) is shown, and the primary side converted voltage E B ' is E B Since '=400V, it can be seen that the operating waveform of the conduction rate is almost the same as in the case of Figure 1(a). (3) Multiple unit series / parallel connection control operation

[0103] FIG. 23 shows the simulation analysis circuit configuration when two power supply units are connected in (a) parallel and (b) series.

[0104] FIG. 24 shows the results of a simulation analysis when two DC-DC converter power supply units are connected in series and parallel.

[0105] Figure 1(a) shows that the output of two power supply units with a reference current Idr = 20 A can be charged to a storage battery at a voltage of EB0 A.

[0106] Figure (b) shows the reference current I dr = Connect the outputs of two 20A power supply units in series to double the voltage, E B This is the operating waveform when charging a 600V storage battery, and it can be seen that the DC current matches the reference value. [Explanation of symbols]

[0107] 100…DC power supply 150…AC power supply 200...Diode bridge circuit 300...PFC circuit 400...Hybrid current controlled inverter 500...High frequency transformer 600...Rectification filter circuit 700...Overvoltage protection circuit 800…DC load 800-1...Voltage control load (general DC load) 800-2...Current control load (battery load) 900...Control system

Claims

1. a DC-AC-DC converter comprising: a DC power supply connected via a DC source inductor to an inverter circuit constituted by a switch circuit constituted by switch elements and diodes connected in anti-parallel; the AC output of the inverter connected to a high frequency transformer; the secondary AC output of the high frequency transformer, which has been insulated and converted into voltage and current, connected to a diode bridge circuit; a circuit in which a smoothing capacitor and, as necessary, a braking resistor connected in series, connected to the DC output terminals of the diode bridge circuit; and a DC load connected from the diode bridge circuit via an output inductor as necessary, comprising: a DC-AC-DC conversion circuit; the inverter controls the current of the DC source inductor by alternately passing positive and negative current to the high frequency transformer at a sufficiently high frequency every half cycle, at a ratio of DC short-circuit operation by the inverter circuit to power supply operation to the high frequency transformer; and the output voltage and current to the DC load are controlled by a current source obtained by DC converting the current of the high frequency transformer using the diode bridge circuit.

2. 2. The current-source DC-DC converter according to claim 1, wherein in order to reduce voltage spikes applied to the inverter during commutation due to leakage inductance of the transformer, a snubber capacitor is connected between the DC terminals of the inverter via a diode, and a circuit is added in which the charge of the snubber capacitor is consumed by a resistor or a step-down chopper circuit consisting of a switch, a free-foiling diode, and a smoothing inductor is used to recover the charge to the DC power supply, thereby suppressing the occurrence of excessive voltage applied to the switch circuit constituting the inverter.

3. 3. A current-source DC-DC converter according to claim 1, wherein the DC inputs of a plurality of said DC-AC-DC conversion circuits are connected to said DC power supply, and the DC outputs of a plurality of said DC-AC-DC conversion circuits are connected in parallel or in series to said DC load, thereby increasing the output current capacity of the device and increasing the output voltage.

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