Control method for current-source DC-DC converter

Abstract

A typical DC-DC converter converts a DC voltage source into high-frequency voltage, insulates it using a high-frequency transformer and converts it into the required voltage and current, then rectifies it using a diode bridge circuit and obtains a DC output through a filter circuit. However, since this is basically a voltage source output, balance control becomes complicated when the device is configured with multiple power supply units. [Solution] The present invention is a method in which an inductor current source connected to a DC power supply is converted into a high-frequency current, and then insulated and converted to the required voltage and current by a high-frequency transformer, and a smoothing capacitor is connected to the current source output that has been converted into DC by a diode bridge circuit to obtain a DC output.This method makes it easy to connect multiple power supply units in parallel, making it easy to increase the capacity of the device.

Description

[Technical field]

[0001] While conventional DC-DC converters have issues due to their basically voltage source output, the DC-DC converter of the present invention uses a current source output, and proposes new control technology and application technology intended to overcome previous issues. [Background technology]

[0002] A typical DC-DC converter converts a DC voltage source into high-frequency voltage, insulates it using a high-frequency transformer and converts it into the required voltage and current, 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, a flyback converter, a forward converter, or a flyback converter that drives a high-frequency transformer from a single power source to reduce size and weight. but It is used.

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

[0005] However, since the range of application of a transformer driven by a single power source is limited due to its 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 through an LC filter circuit is used, and this type of converter is widely used in fields with relatively large capacities.

[0006] Meanwhile, with the spread of electric vehicles (EVs), EV charging stations with higher capacities of around 50 kW are rapidly becoming more common, moving away from on-board chargers and home EV charging stations with capacities of around a few 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 controls the conversion of the resulting DC power into an insulated 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 source to DC, and those that convert from a three-phase power source 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. In order to reduce size and weight, the voltage source of the DC power source is generally made high-frequency by an inverter, and then converted to the required voltage and current level for insulation using a high-frequency transformer, and then converted back to DC by a rectifier circuit, as described above.

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

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

[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, providing many benefits in terms of malfunctions and inspections.

[0014] As a power supply unit for this purpose, it is possible to consider a power supply unit configuration that integrates a PFC converter and a DC-DC converter, or a power supply unit configuration that consists only of a 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] The present invention solves the fundamental problem of voltage source output in conventional DC-DC converters by configuring the DC-DC converter as 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, p158, p.112, 2000. [Patent documents]

[0018] [Patent Document 1] Patent No. 6328506: "Control device for ACDC converter" [Patent Document 2] Patent Publication 2021-141738: "Multiple power conversion control systems" [Patent Document 3] Patent application 2006-6042: “DC power supply device” [Patent Document 4] JP2024-54936: "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 the 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 back to DC using a rectifier circuit, and connected to a DC load via a filter circuit.

[0020] Here, if the output of the voltage conversion device is a voltage source, but The voltage source is the battery. directly There are issues that can't be connected.

[0021] Where: It is possible 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 constitutes a DC power supply section in addition to 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 small voltage difference too Because a large current flows, proper load current sharing control becomes an issue.

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

[0025] In addition, even the slightest DC component may occur in a voltage-type inverter that converts high-frequency waves, causing 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 issue.

[0026] FIG. 3 shows the basic configuration of an AC / DC converter configured 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. , change of flow 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 This allows the inverter to be switched on and off. 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 how power supply units (DC-DC UNIT A) are connected in parallel to increase the current capacity and then connected 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, an excessive current will not flow. Even if multiple power supply units are connected in parallel, each unit can operate with its own current output controlled by the power supply unit. Can The capacity of the device 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 、 Since the current source is connected to a high-frequency transformer, there is no problem with DC bias magnetism in the transformer, as opposed to general DC-DC converters.

[0033] (Non-Patent Document 1) shows combinations of a voltage source inverter connected to a voltage source and a current source inverter connected to a current source, as well as typical loads that are suitable for them. Voltage source inverters are generally used with an inductive load in which an inductor is connected in series to the load, while 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 source inverter Ta Hybrid Current Source Inverter of 2 shows a circuit configuration.

[0035] The figure (a) shows the circuit configuration of a general current-source inverter, which is used by connecting a capacitor to the AC load terminal. 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 inverse parallel 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, compared to the switch configuration used in normal voltage-source inverters, a switch circuit usually has a higher reverse voltage resistance. teeth Diodes are connected in series. To , the switch circuit becomes more complicated do but also Added The conduction loss through 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, so that the switch constituting the inverter element No reverse voltage is applied to

[0039] For this reason, 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 problem with voltage drop.

[0040] In addition, In a hybrid current source inverter circuit, Problems caused by leakage inductance in the high-frequency transformer connected to the inverter can be 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 relevance of the prior art cited here is now set forth.

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

[0043] In (Patent Document 2), the diode rectifier connected to the high-frequency transformer is configured as a PWM converter. death, To increase the capacity of the device, it is configured with multiple power supply units. bidirectional Power System In The intention is to improve reliability and redundancy in the event of a partial failure.

[0044] In (Patent Document 3), when controlling the DC load voltage and current by controlling the inductor current with a step-down chopper and performing diode rectification via a transformer in an inverter, 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 document, 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] For this reason, the current path due to the leakage inductance of the transformer when switching is not secured, 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 This concerns 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 is 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 By using pulse width control, it is possible to realize a sinusoidal current function proportional to the power supply voltage with a simple configuration without using the configuration of a general PFC converter. While It enables DC power supply control.

[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 equipment capacity increases, Discontinuous Pulse Current Therefore, There are concerns that this could lead to increased current loss in the circuit and generate noise, 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 at light loads, it operates with a constant current under normal load conditions. continuous It operates in pulse current mode. Flow Therefore, the operating efficiency is Improved, The effect of switching noise on peripheral devices can also be reduced. Because it is possible, It is suitable for configuration control 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. 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 in which a high frequency transformer for insulation and voltage / current conversion is added to the output of the hybrid current source inverter. This is the basic circuit configuration of a DC-DC converter, and it consists of a DC voltage source (100) and an inductor L b The AC output of the hybrid current-source inverter circuit (400), which is composed of a current source and a voltage-source inverter circuit, is connected to a high-frequency transformer (500), and the isolated secondary current is connected to a rectifier circuit and a capacitor C d The circuit is configured such that a DC output obtained by a rectifier circuit section (600) having the above-mentioned components connected thereto is connected to a DC load (800).

[0053] Figure 7 andFigure 8 shows the inductor L b 1 shows the operation 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 during discontinuous operation, and Figure 8 is the operating waveform during continuous operation.

[0055] The switching 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 periods, the inductor current i Lb is controlled.

[0056] 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 secondary AC current i t2 The output current i is rectified by a diode bridge circuit. ds By smoothing with a DC capacitor, the 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 it is continuous or discontinuous depends on the inductor L b value and switching frequency f s Not only depending on the load condition tooHowever, if the current becomes discontinuous, problems will occur with pulse currents, so If the device capacity is large, To be able to operate in as continuous a domain as possible Need to be designed .

[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 current width controlled, and the DC output current i ds The pulsation of the pressure can also be significantly reduced.

[0060] Also, high frequency transformers for , the 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 problem of 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] FIG. 9 shows an equivalent circuit that has been subjected to a linear transformation taking into account the effect of the leakage inductance of the high-frequency transformer in order to confirm the operation at this time.

[0063] Figure 10 shows this circuit. In This is the operating waveform when switching control of the hybrid current source inverter is applied, and the inverter changes from the short circuit mode of the inductor current to the power supply 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] In order to suppress the occurrence of this spike voltage, it is necessary to design the high frequency transformer so as to reduce the leakage inductance as much as possible. importantHowever, Leakage inductance Even if the inductor current is small, if the inductor current 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 dissipated 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. (a) uses a braking resistor, and (b) connects a step-down chopper circuit to prevent the snubber capacitor voltage from exceeding a set value. Both are configured by connecting to the DC voltage source side.

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

[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, but Essential The lossless step-down chopper of Figure 11(b) Regeneration using The circuit is selected.

[0069] In particular, when the device capacity is large and it is composed of multiple power supply units, the step-down chopper in Fig. 11(b) is used. 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 acts 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 load, the load terminal voltage ed is detected and compared with a certain reference voltage Edr to generate a current reference value Idr in a voltage regulator, and the DC load current id is adjusted to match this current by the inverter through a current regulator. Between switching signals to the circuit The system is configured to control the phase α of the

[0072] Next, in the case of a constant voltage battery load, the load terminal voltage is not taken into consideration, so that the DC load current id matches the current reference Idr. Through a current regulator Inverter Between switching signals to the circuit The system configuration is such that the phase α of the

[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 done Requires a power supply unit Number Only parallel connection Things to do in, A power supply device of any capacity can be easily constructed.

[0075] In addition, the standard 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 The above configuration is to connect the 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 it is used as a storage battery charging circuit, a small join Inductance L d of Insert as needed Or, use a small vibration damping resistor in series with the capacitor. as needed Need to connect.

[0077] In addition, to prevent the generation of surge voltages due to leakage inductance of a high-frequency transformer, it becomes 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 the case of a single-phase PFC converter circuit but, Three-phase PFC converter circuit for large capacity devices such as EV charging stations but It will be used. Effect of the Invention

[0080] The characteristics and effects of the current-fed DC-DC converter of the present invention are listed below. 1) A high-frequency transformer can be used to obtain DC output that is isolated from a DC power source. 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 is The 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 current continuity region. 7) The present invention current type Since 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 The transformer is driven by a current source, so 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 larger capacity devices. 11) The present invention current type When duplicating DC-DC converters, the switching phase of the two high-frequency inverters is 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 commutation energy due to this is not a problem because a current path is secured by the voltage source inverter. 13) In a voltage-type inverter, the generation of an overvoltage due to the leakage inductance of the transformer when the inductor current circuit is switched can be prevented by using a snubber circuit between the DC terminals of the inverter or Step-down By Choppa To DC power supply Regeneration This can be sufficiently suppressed by adding a circuit to As mentioned above, the present invention has the following advantages over the general DC-DC converter: current type Since the DC-DC converter has a current source output, It is also easy to connect to a storage battery and to connect the outputs of multiple DC-DC converters in parallel, making it easy to create a parallel multiplexed configuration. For this reason, 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 Equipment Configuration Extremely useful for standardization The present invention The following effects can be expected. [Brief description of the drawings]

[0081] [Figure 1] Typical DC-DC converter circuits and DC-DC and AC-DC power supply units [Diagram 2] Configuration of a battery charging device using multiple general DC-DC power supply units [Diagram 3] Current-type DC-DC-DC converter circuit and DC-DC and AC-DC power supply unit according to 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 [Diagram 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-type DC-DC converter of the present invention [Figure 7] Switching operation waveforms of the current-source DC-DC converter circuit of the present invention during current discontinuity [Figure 8] Switching operation waveforms 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-type DC-DC converter circuit of the present invention [Figure 10] Switching operation waveform during continuous current, taking into account transformer leakage inductance [Figure 11] Example of a circuit to suppress surge voltage between DC terminals of an inverter due to leakage inductance of a transformer (a) Circuit with snubber circuit added (b) Circuit with overvoltage suppression circuit added [Figure 12] Switching operation waveforms 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] Example of a circuit configuration for a large-capacity power supply using multiple current-source DC-DC converter power supply units [Figure 15] A practical circuit configuration example of a storage battery charging circuit using the current-source DC-DC converter of the present invention [Figure 16] Example of 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-type 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) [Diagram 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 equipment capacity increase 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 PREFERRED EMBODIMENTS

[0082] In order to verify an embodiment of a DC power supply device configured with a DC-DC converter circuit of the present invention, In Figure 17 Power supply unit main circuit configuration and control system The simulation circuit of The figures are 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 DC voltage E b The voltage is set according to the relationship between the leakage inductance of the transformer and the step-down chopper circuit is used to suppress the surge voltage caused by the leakage inductance of the transformer. Overvoltage Add a suppression circuit, Permissible voltage applied to switching elements Voltage V z (V z = 600V).

[0084] In addition, 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 from the viewpoint of DC output voltage ripple. d =10uF.

[0085] Under the above operating conditions, the DC load is a resistive load, and the DC output constant control loop is operated to set the current reference I dr is the output value of the voltage regulator, and b) a battery load is connected. In case, Charging current reference value I dr The 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 waveform when the load resistance value is changed at =400V.

[0087] In the figure (a), the load resistance is R d = 50 ohms, (b) is R d = 500ohms. The present invention DC-DC converters are not able to withstand large load changes. too Reference voltage E dr DC output voltage E d =400V Maintain The DC reference current I dr The current i d 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 high frequency inverter i t1 , the rectified current of the transformer secondary current i ds The waveform is the law of nature, In Figure 2(a), the inductor current is continuous, so the current waveform has a nearly constant amplitude. Nearby In Figure (b), it can be seen that the inductor current becomes a discontinuous triangular wave, and the current waveforms of each part change accordingly.

[0089] Figure 19 shows the DC reference voltage E dr = 400V, load resistance is R d = 50 ohms, the operating waveform confirming the occurrence of surge voltage due to leakage inductance is shown. There is no significant change in Voltage applied to the inverter switch element S1 e s There are differences in the peak values.

[0090] The figure (a) shows the snubber capacitor C z = 10uF, resistor R z When a 5kohm RC snubber circuit is added, the suppression voltage is reduced by a step-down chopper (V z = 500V) is added to the overvoltage suppression circuit.

[0091] In the case of the RC snubber circuit shown in Fig. 1(a), it can be constructed only with 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 z To suppress It is confirmed that this can be done.

[0093] Figure 20 shows the DC load resistance R d = 50 ohms, the reference value of the DC output voltage E dr =500V and E dr = 200V, the operating waveforms are based on a 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] The figure (a) shows the DC power supply voltage E b = 300V, DC output voltage reference value E dr When the output voltage is set to 500V, the DC output voltage e d indicates that the output is controlled to the reference value.

[0096] In contrast, in Fig. 1(b), the reference value of the DC output voltage is 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 we can see that it is operating normally.

[0097] However, the DC load resistance R d = 50 ohms constant, DC output voltage E d Because the inductor L b It can be seen that the current becomes smaller and 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 at 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 for voltages of 400V and 200V are shown.

[0099] Figure 21 shows the voltage of the storage battery E B = 300V, 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] FIG. 22 shows the battery voltage E B The operating waveforms for voltages of 400V and 200V are shown.

[0101] Figure 21 (a) and (b) show the voltage E of the storage battery. B is the DC power supply voltage E b The value of E is the same as 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. B Since is 400V and is higher than the DC power supply voltage Eb, 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. 20 As in (b), the battery voltage is low ( E B = 200V), the results are shown when the transformation ratio a is set to (a = 2), and the primary-side converted voltage E B ' is E B Since '=400V, it can be seen that the operating waveform has almost the same conduction rate as in the case of Figure 2(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 power supply units of two DC-DC converters are connected in series and parallel.

[0105] Figure 2(a) shows that the output of two power supply units with a reference current Idr = 20A can be charged into a storage battery at a voltage of EB0A.

[0106] The figure (b) shows the reference current I dr = Two 20A power supply units are connected 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 controlled load (general DC load) 800-2...Current control load (battery load) 900 ... Control system

Claims

1. In a DC-AC-DC conversion circuit, a DC power supply is connected via an inductor to an inverter circuit configured with a switch circuit configured with a switch element and an anti-parallel connected diode, the AC output of the inverter circuit is connected to a high-frequency transformer, and the secondary AC output of the high-frequency transformer, which is insulated and converted into a voltage and current, is converted into a DC output terminal by a rectifier circuit, and a DC load is connected in parallel with a smoothing capacitor. A control method for a current-source DC-DC converter characterized in that the current of the DC load can be controlled regardless of whether the current flowing through the inductor is discontinuous or continuous by controlling the phase between switching signals to the inverter circuit every half cycle of a high-frequency control cycle via a current regulator so that the current to the DC load coincides with a constant current reference value, thereby changing the ratio of a DC short-circuit operation period of the current flowing through the inductor and a power supply operation period in which current to the high-frequency transformer is alternately made positive and negative, relative to the control cycle.

2. In the control method for a current-type DC-DC converter according to claim 1, when the terminal voltage of the DC load is controlled to be constant, the current reference value is generated by a voltage regulator so that the terminal voltage of the DC load coincides with a constant reference voltage; a feedback control operation that changes a ratio of a DC short circuit operation period of a current flowing through the inductor and a power supply operation period in which current to the high-frequency transformer is alternately made positive and negative, to the control period every half cycle of the control period, via a current regulator, so that the current to the DC load coincides with the current reference value, thereby controlling the voltage of the DC load by controlling the current of the DC load regardless of whether the current flowing through the inductor is discontinuous or continuous.

Images