Power conversion device

Abstract

To provide a power conversion device with reduced loss.SOLUTION: A power conversion device comprising an input-side bridge circuit, an output-side bridge circuit, a transformer, and a control unit, wherein the control unit sets a specific region in a case where m1 in a Hi period of an input voltage of the transformer, m2 in a Hi period of an output voltage of the transformer, and m12 which is a difference between a center of m1 and a center of m2 are respectively set to (m1-m2) / 2 as a horizontal axis and (m1 + m2) / 2 as a vertical axis, to a region A, a region B, and a region C, and sets a number of turns of a primary winding of the transformer to Nin, in a case where the number of turns of the secondary winding is Nout, the voltage angle product difference Δ X is set as Δ X = Vin * m1-Vout * (Nin / Nout) * m2 with respect to the input voltage Vin to the input side bridge circuit and the output voltage Vout to the output side bridge circuit, and the control unit controls m1 and m2 so that the voltage angle product difference Δ X becomes a predetermined value while switching between the region A, the region B, and the region C.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present invention relates to a power conversion device. [Background technology]

[0002] As an example of a power conversion device, a power conversion device using a DC / DC converter as a main part or a part thereof is known. As an example, Patent Document 1 discloses a technology for performing soft switching in a DC / DC converter. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] U.S. Patent No. 5,027,264 Summary of the Invention [Problem to be solved by the invention]

[0004] The DC-DC converter described in Patent Document 1 includes, for example, a switching circuit, a transformer, an inductance element, a capacitor, and a control unit. The DC-DC converter 1 performs power conversion by utilizing electrical energy flowing through the inductance element.

[0005] In the DC / DC converter described in Patent Document 1, soft switching operation is possible in the input-side bridge circuit and the output-side bridge circuit by control of the control circuit. However, there exists an operating range in which soft switching operation does not occur, depending on the phase difference between the input-side bridge circuit and the output-side bridge circuit (i.e., the output command value from the control circuit) and the voltage ratio between the input and output voltages. This poses a problem of increased loss.

[0006] Furthermore, depending on the phase difference conditions, the magnitude of losses due to iron loss and copper loss in the transformer may become significant, resulting in a decrease in power conversion efficiency.

[0007] An object of the present invention is to provide a power conversion device that achieves reduced loss. [Means for solving the problem]

[0008] an input-side bridge circuit and an output-side bridge circuit; a transformer disposed between the input-side bridge circuit and the output-side bridge circuit; A power conversion device including a control unit that controls the input side bridge circuit and the output side bridge circuit, The control unit m1 is a Hi period of the input voltage input from the input-side bridge circuit to the transformer; m2 is a Hi period of the output voltage output from the transformer to the output-side bridge circuit; For m12, which is the difference between the center of the m1 period and the center of the m2 period, If the horizontal axis is (m1-m2) / 2 and the vertical axis is (m1+m2) / 2, (A) The range surrounded by the position where the horizontal axis is 90 and the vertical axis is 90, the position where the horizontal axis is the absolute value m12 and the vertical axis is the absolute value m12, and the position where the horizontal axis is the absolute value m12 and the vertical axis is 180-absolute value m12 is defined as region A. (B) The range surrounded by the horizontal axis range between -absolute value m12 and absolute value m12 and the vertical axis range between absolute value m12 and (180-absolute value m12) is defined as region B. (C) The range surrounded by the position where the horizontal axis is -90 and the vertical axis is 90, the position where the horizontal axis is -absolute value m12 and the vertical axis is absolute value m12, and the position where the horizontal axis is -absolute value m12 and the vertical axis is 180-absolute value m12 is defined as region C. When the number of turns of the primary winding of the transformer is Nin and the number of turns of the secondary winding is Nout, the voltage angle product difference ΔX is expressed as follows, where Vin is the input voltage to the input side bridge circuit and Vout is the output voltage to the output side bridge circuit: Set △X=Vin×m1-Vout×(Nin / Nout)×m2, The power conversion device in which the control unit controls m1 and m2 while switching between the region A, region B, and region C so that the voltage-angle product difference ΔX becomes a predetermined value. [Effects of the Invention]

[0009] According to the present invention, it is possible to provide a power conversion device that achieves reduced loss. Further means and effects of the present invention will become apparent throughout the entire specification below. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a circuit diagram of a DC / DC converter according to an embodiment. [Figure 2] 10 is an example of input and output waveforms in one embodiment. [Figure 3] FIG. 10 is a diagram illustrating an input / output voltage ratio and an output DC current region division in an embodiment. [Figure 4] FIG. 10 is a diagram showing another example of region division of input / output voltage ratio and output DC current in one embodiment. [Figure 5] FIG. 10 is a diagram illustrating a method for setting area divisions in one embodiment. [Figure 6] FIG. 4 is a diagram showing an example of control on line (1) in FIG. [Figure 7] FIG. 4 is a diagram showing an example of control on line (2) in FIG. [Figure 8] FIG. 4 is a diagram showing an example of control on line (3) in FIG. [Figure 9] FIG. 4 is a diagram showing an example of control on line (4) in FIG. [Figure 10] FIG. 10 is a diagram showing the loss conditions of the present embodiment and a comparative example. [Figure 11] 4A to 4C are diagrams showing regions for explaining waveforms at various points in FIG. 3. [Figure 12] FIG. 12 is a waveform diagram at part A in FIG. [Figure 13] FIG. 12 is a waveform diagram at part B1 of FIG. [Figure 14] FIG. 12 is a waveform diagram at part B2 in FIG. [Figure 15] FIG. 12 is a waveform diagram at part C in FIG. [Figure 16] FIG. 12 is a waveform diagram at part D1 in FIG. [Figure 17]FIG. 12 is a waveform diagram at part D2 in FIG. [Figure 18A] This is a re-presentation of Figure 12. [Figure 18B] FIG. 18B is an enlarged waveform diagram of a portion of FIG. 18A. [Figure 19A] 18B is a waveform of a comparative example to FIG. 18A. [Figure 19B] FIG. 19B is an enlarged waveform diagram of a portion of FIG. 19A. [Figure 20A] This is a re-presentation of Figure 13. [Figure 20B] FIG. 20B is an enlarged waveform diagram of a portion of FIG. 20A. [Figure 21A] 20B is a waveform of a comparative example to FIG. 20A. [Figure 21B] FIG. 21B is an enlarged waveform diagram of a portion of FIG. 21A. [Figure 22A] This is a re-presentation of Figure 15. [Figure 22B] FIG. 22B is an enlarged waveform diagram of a portion of FIG. 22A. [Figure 23A] 22B is a waveform of a comparative example to FIG. 22A. [Figure 23B] FIG. 23B is an enlarged waveform diagram of a portion of FIG. 23A. [Figure 24] This is an explanation of the definition of the direction of current. [Figure 25] FIG. 1 is an explanatory diagram of an operation during ZVS. [Figure 26] FIG. 10 is an explanatory diagram of the operation during ZCS. [Figure 27] FIG. 10 is an explanatory diagram of the operation during hard switching. [Figure 28A] FIG. 1 is an explanatory diagram of an example of a power conversion device. [Figure 28B] FIG. 1 is an explanatory diagram of an example of a power conversion device. [Figure 29A] FIG. 1 is an explanatory diagram of an example of a charging device. [Figure 29B] FIG. 1 is an explanatory diagram of an example of a charging device. [Figure 29C] FIG. 1 is an explanatory diagram of an example of a charging device. [Figure 29D] FIG. 1 is an explanatory diagram of an example of a charging device. [Figure 29E] FIG. 1 is an explanatory diagram of an example of a charging device. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, embodiments of the present invention will be described with reference to the drawings as needed. [Example]

[0012] FIG. 1 shows a circuit diagram of an example of a single-phase isolated DC / DC converter. This single-phase isolated DC / DC converter can be used bidirectionally by inverting the input and output, and includes a capacitor 10 that smooths the DC input voltage Vin. A first bridge circuit (e.g., a primary-side bridge circuit 20) is connected to both ends of the capacitor 10. This can also be called an input-side bridge circuit. A primary winding 41 of a transformer for input-output isolation is connected to output-side nodes N1 and N2 of the primary-side bridge circuit via an inductance element. Input-side nodes N11 and N12 of a second bridge circuit (e.g., a secondary-side bridge circuit 50) are connected to a secondary winding 42 of the transformer. The secondary-side bridge can also be called an output-side bridge circuit.

[0013] An isolated DC / DC converter is an example of a power conversion device that uses a transformer (hereinafter referred to as "transformer") to isolate the input side from the output side, converts an input direct current (DC) voltage to a DC voltage of a predetermined level, and outputs it. This DC / DC converter is of the DAB (Dual Active Bridge) type. It includes a transformer with a primary winding and a secondary winding, an input bridge circuit connected to the primary winding side and composed of switching elements, an output bridge circuit connected to the secondary winding side and composed of switching elements, and a control circuit that operates the switching elements of the input bridge circuit and output bridge circuit to perform constant voltage or constant current operation.

[0014] For example, when a DC voltage of a predetermined voltage is input, this DC input voltage is switched by the switching elements in the input bridge circuit and converted into an AC (alternating current) voltage. The converted AC voltage is then converted into an AC voltage that depends on the turns ratio of the transformer's primary and secondary windings and its leakage inductance. The converted AC voltage is then switched by the switching elements in the output bridge circuit and converted into a predetermined DC voltage, resulting in a constant DC output voltage.

[0015] In the input-side bridge circuit and the output-side bridge circuit, the transformer current charges and discharges the parasitic capacitance of the switching elements. At this time, by performing switching when the voltage of the parasitic capacitance is zero after the charging and discharging operation (i.e., zero-voltage switching), it is possible to suppress switching losses in the switching elements and further reduce surge voltages and noise caused by switching. In addition, by performing switching when the transformer current is zero (i.e., zero-current switching), it is possible to suppress switching losses in the switching elements and further reduce surge voltages and noise caused by switching.

[0016] Although not shown in FIG. 1, an input voltage detection unit detects a DC input voltage Vin. Also, although not shown, an output voltage detection unit detects a DC output voltage Vout. A load ZL is connected to the output side of the secondary-side bridge circuit 50 via a smoothing capacitor 60. Furthermore, a control circuit 70 is provided that outputs four first control signals G1, G2, G3, and G4 and four second control signals G11, G12, G13, and G14 for controlling the switching of the primary-side bridge circuit 20 and the secondary-side bridge circuit 50.

[0017] The control circuit 70 (control unit) includes, for example, a microcomputer having a CPU (Central Processing Unit), ROM (Read Only Memory), RAM (Random Access Memory), input / output ports, and various other circuits. The CPU of this microcomputer reads and executes programs stored in the ROM to control the operation of the first bridge circuit and the second bridge circuit. Specifically, it has a function of adjusting the switching timing of the switching elements in the first bridge circuit and the second bridge circuit.

[0018] The control circuit 70 calculates an input / output voltage ratio d (d = Vout / Vin) between the input voltage Vin and the output voltage Vout in the first bridge circuit and the second bridge circuit. Then, based on the input / output voltage ratio d and the target value of the output current flowing through the load ZL, the control circuit 70 determines a high-level period m1 [deg] of the input voltage Vin_ac on the first bridge circuit side, a high-level period m2 [deg] of the output voltage Vout_ac on the second bridge circuit side, and a phase difference m12 [deg] between the output voltages of the first bridge circuit and the second bridge circuit. For example, the control circuit 70 may be configured to calculate the high-level period m1 [deg] of the input voltage Vin_ac on the first bridge circuit side, the high-level period m2 [deg] of the output voltage Vout_ac on the second bridge circuit side, and the phase difference m12 [deg] between the output voltages of the first bridge circuit and the second bridge circuit, corresponding to the calculated input / output voltage ratio d and the target value of the output current flowing through the load ZL, based on a relational expression or the like.

[0019] Alternatively, in another example, the control circuit 70 may be configured to include a table that stores, for the calculated input-output voltage ratio d and the target value of the output current flowing through the load ZL, the Hi period m1 [deg] of the input voltage Vin_ac on the first bridge circuit side, the Hi period m2 [deg] of the output voltage Vout_ac on the second bridge circuit side, and the phase difference m12 [deg] between the output voltages of the first bridge circuit and the second bridge circuit. The domains of m1 and m2 are 0 to 180 deg, and the domain of m12 is -90 to 90 deg. When m12 is positive, power flows from the input side to the output side, and when m12 is negative, power flows from the output side to the input side.

[0020] The primary-side bridge circuit 20 has four first switching elements 201, 202, 203, and 204 connected in a bridge configuration, which are turned on / off by four first control signals G1 to G4, respectively. The first switching elements 201, 202, 203, and 204 are turned on / off by the control signals G1 to G4 input to their gates.

[0021] A first inductance element (not shown) and a primary winding 41 of a transformer 40 are connected in series between output nodes N1 and N2 of the primary bridge circuit 20. Furthermore, a capacitor (not shown) is connected in parallel to each of the first switching elements 201, 202, 203, and 204.

[0022] The first inductance element, together with four capacitors connected in parallel to the first switching element, constitutes an LC resonant circuit, but in Figure 1, this inductance element is omitted and instead the primary side leakage inductance inherent in the transformer 40 is configured to have the same function.

[0023] The primary-side bridge circuit 20 converts the DC input voltage Vin into an AC voltage by turning on / off the first switching elements 201-204, and supplies the AC voltage to the primary winding 41. Furthermore, current also flows through the first anti-parallel diodes 211-214 depending on the states of the first switching elements 201-204. The first anti-parallel diodes 211-214 may be integrated with or built into the first switching elements 201-204, respectively, or may be externally attached in anti-parallel to the first switching elements 201-204.

[0024] Furthermore, as an example, first capacitors (not shown) that are first capacitance elements for resonance are connected in parallel to each of the switching elements 201 to 204. The four first capacitors form an LC resonance circuit together with the inductance of the primary winding 41, but these first capacitors may also be formed by the parasitic capacitance of each of the switching elements 201 to 204.

[0025] A second inductance element (not shown) and the secondary winding 42 of the transformer 40 are connected in series between input nodes N11 and N12 of the secondary bridge circuit 50. In addition, capacitors (not shown) are connected in parallel to each of the second switching elements 501, 502, 503, and 504.

[0026] The second inductance element, together with four capacitors connected in parallel to the second switching element, constitutes an LC resonant circuit; however, in FIG. 1, this inductance element is omitted and instead the secondary leakage inductance inherent in the transformer 40 is configured as having an equivalent function. In the configuration shown in FIG. 1, the secondary bridge circuit 50 converts the DC output voltage Vout into an AC voltage by the on / off operation of the second switching elements 501-504 and supplies the AC voltage to the secondary winding 42. Furthermore, current also flows through the second anti-parallel diodes 511-514 depending on the states of the second switching elements 501-504. The second anti-parallel diodes 511-514 may be integrated with or built into the second switching elements 501-504, respectively, or may be externally attached in anti-parallel to the second switching elements 501-504.

[0027] Furthermore, second capacitors (not shown) that are second capacitance elements for resonance are connected in parallel to the switching elements 501 to 504. The four second capacitors form an LC resonance circuit together with the inductance of the secondary winding 42, but these second capacitors may also be formed by the parasitic capacitance of the switching elements 501 to 504.

[0028] The DC voltage output from the secondary bridge circuit 50 is smoothed by a smoothing capacitor 60 to become a DC output voltage Vout, and this output voltage Vout is supplied to a load ZL.

[0029] The secondary-side bridge circuit 50 rectifies the AC voltage supplied from the secondary winding 42 side by the second anti-parallel diodes 511 to 514 and outputs a DC voltage. Alternatively, the secondary-side bridge circuit 50 has a function of converting the DC input voltage into an AC voltage and supplying it to the secondary winding 42 side by the on / off operation of the switching elements 501 to 504.

[0030] 1 has been described as an example in which no inductance element is disposed between the primary bridge circuit 20 or the secondary bridge circuit 50 and the transformer 40. However, the present invention is not limited to such a configuration, and an inductance element may be disposed between the AC side of one of the primary bridge circuit 20 or the secondary bridge circuit 50 and the transformer 40. Alternatively, an inductance element may be disposed between the AC side of both the primary bridge circuit 20 and the secondary bridge circuit 50 and the transformer 40.

[0031] 2 is a diagram showing voltage waveforms in the isolated DC / DC converter of this embodiment, which will be explained with reference to the numbers in the circuit diagram of FIG.

[0032] 2, the first to fourth rows from the top show the drain-source voltage waveforms of switching elements 201 to 204. In the fifth row, the vertical axis represents the input voltage Vin_ac, which is the voltage between nodes N1 and N2, and the horizontal axis represents time or phase [deg].

[0033] 2, the sixth to ninth rows from the top show the drain-source voltage waveforms of the switching elements 501 to 504. In the tenth row, the vertical axis represents the output voltage Vout_ac, which is the voltage between nodes N11 and N12, and the horizontal axis represents time or phase [deg].

[0034] The phase can also be expressed as an angle, because it is common to generate control waveforms and control timing with one pulse period being 360 degrees.

[0035] As shown in the fifth row of Figure 2, the input voltage Vin_ac has a pulsed voltage waveform. The input voltage Vin_ac has an Hi period 22 due to amplitude 221, and its phase difference or angle is m1 [deg]. This is equal to the phase difference between the rising or falling edges of the left leg voltage and right leg voltage on the primary bridge circuit side. The amplitude 221 of the input voltage Vin_ac is also equal to Vin.

[0036] As shown in the tenth row of FIG. 2, the output voltage Vout_ac has a pulsed voltage waveform. The output voltage Vout_ac has an amplitude 251 with a Hi period 25, and its phase difference or angle is m2 [deg]. This is equal to the phase difference between the rising and falling edges of the left leg voltage and the right leg voltage on the secondary bridge circuit side. The amplitude 251 of the output voltage Vout_ac is also equal to Vout.

[0037] m12 is the phase difference, or angle difference, between the center of m1 and the center of m2.

[0038] 3 shows the switching modes at each operating point of the isolated DC / DC converter of this embodiment. The horizontal axis represents the input / output voltage ratio d, and the vertical axis represents the output side (secondary side) DC current.

[0039] The input / output voltage ratio d is defined as d=output voltage / input voltage, where Vout and Vin are Vout and Vin in FIG.

[0040] The left end of the horizontal axis in Figure 3 is d=0. The center of the vertical axis represents 0 amperes. Above the center, i.e., the area where the current is positive, is when power flows from the input side to the output side. Below the center, i.e., the area where the current is negative, is when power flows from the output side to the input side. Symbols A to D in Figure 3 represent switching modes. Note that B can be further subdivided into B1 and B2. Similarly, D can also be further subdivided into D1 and D2.

[0041] In this embodiment, loss reduction is achieved by finely switching the control method according to the input / output voltage ratio and the state of the output side DC current. Switching control at least in the three switching mode regions A, B, and C in Fig. 3 is essential for loss reduction in this embodiment.

[0042] The shape of Figure 3 varies depending on the various constants of the circuit to be controlled. It is also affected to some extent by the controlled object or load. Therefore, as shown in Figure 4, the shape may differ slightly from that of Figure 3.

[0043] For this reason, these switching characteristics are set in advance at the circuit design and power conversion device design stage, or before shipping, or at the stage of test operation at the customer's facility, and are recorded in a storage device as a control table or control information in the control circuit 70 in Fig. 1. Note that AI technology can also be used to automatically perform this state detection.

[0044] The definition of the switching mode will be explained using Figure 5. This definition of the switching mode itself is one of the features of the control in this embodiment. In the following, for ease of explanation, the switching mode and the region in which the switching mode is performed will be represented by the same alphabet, such as the range controlled as switching mode A being referred to as region A.

[0045] The regions of each switching mode can be defined as follows using m1, m2, and m12 explained in Figure 2. If the horizontal axis of Figure 5 is (m1-m2) / 2 and the vertical axis is (m1+m2) / 2, (A) The range surrounded by the position where the horizontal axis is 90 and the vertical axis is 90, the position where the horizontal axis is the absolute value m12 and the vertical axis is the absolute value m12, and the position where the horizontal axis is the absolute value m12 and the vertical axis is 180-absolute value m12 is defined as region A. (B) The range surrounded by the horizontal axis range between -absolute value m12 and absolute value m12 and the vertical axis range between absolute value m12 and (180-absolute value m12) is defined as region B. (C) The range surrounded by the position where the horizontal axis is -90 and the vertical axis is 90, the position where the horizontal axis is -absolute value m12 and the vertical axis is absolute value m12, and the position where the horizontal axis is -absolute value m12 and the vertical axis is 180-absolute value m12 is defined as region C.

[0046] The control circuit 70 controls the primary bridge circuit 20 and the secondary bridge circuit 50 while switching between the regions A, B, and C.

[0047] Furthermore, region B can be further subdivided, and region B1 and region B2 can be set so that (B1) the range on the horizontal axis between 0 and absolute value m12 is region B1, and (B2) the range on the horizontal axis between -absolute value m12 and 0 is region B2.

[0048] Region D is determined as the range surrounded by (D) the position where the horizontal axis is - absolute value m12 and the vertical axis is 180 - absolute value m12, the position where the horizontal axis is absolute value m12 and the vertical axis is 180 - absolute value m12, and the position where the horizontal axis is 0 and the vertical axis is 180.

[0049] Region D can be further subdivided, and (D1) the region surrounded by the position where the horizontal axis is -absolute value m12 and the vertical axis is 180-absolute value m12, the position where the horizontal axis is 0 and the vertical axis is 180, and the position where the horizontal axis is 0 and the vertical axis is 180-absolute value m12 can be set as D1. Also, (D2) the region surrounded by the position where the horizontal axis is absolute value m12 and the vertical axis is 180-absolute value m12, the position where the horizontal axis is 0 and the vertical axis is 180, and the position where the horizontal axis is 0 and the vertical axis is 180-absolute value m12 can be set as D2.

[0050] The operating conditions of the switching mode in FIG. 3 are such that as the input / output voltage ratio d increases from 0, the state transitions according to the state of the output side DC current.

[0051] The switching modes in FIG. 3 are as follows, for example, when the output side DC current is in the conditions (1) to (4), as explained along the broken lines in FIG.

[0052] Under the condition of output DC current (1), the region switches from D2 to C to B2 to B1 to A.

[0053] Under the condition of output DC current (2), the region switches as follows: D2 → C → B2 → D2 → D1 → B1 → A.

[0054] Under the condition of output DC current (3), the region switches from D2 to C to D2 to D1 to B1 to A.

[0055] Under the condition of output DC current (4), the region switches from D2 to D1.

[0056] The above is the transition in the case of constant current drive, where the output DC current is constant and the output voltage is increased. Similarly, in the case of drive where both the output DC current and the output voltage are changed, the output current and voltage requirements are set using one or more diagonal lines or curves instead of the dashed lines (1) to (4) in Figure 3, and the region transition in Figure 3 follows the diagonal lines or curves.

[0057] Using Figures 6 to 9, we will explain how to control m1 and m2 in Figure 2 when the region transitions from (1) to (4) in Figure 3 occur. In each figure, TP is the case when the input / output voltage ratio d is equal to the value obtained by dividing the number of turns of the secondary winding 42 of the transformer 40 by the number of turns of the primary winding 41 of the transformer 40. If the number of turns of the secondary winding 42 is Nout and the number of turns of the primary winding 41 is Nin, then TP = Nout / Nin. This can also be referred to as the turns ratio.

[0058] When this input / output voltage ratio d is TP, the relationship is output voltage detection value (Vout) = input voltage detection value (Vin) × transformer turns ratio (Nout / Nin).

[0059] 6 to 9, an example of control of the voltage angle product difference ΔX relative to the input / output voltage ratio d will be described. The horizontal axis represents the input / output voltage ratio d.

[0060] The voltage angle product difference ΔX is defined as ΔX=Vin×m1−Vout×(Nin / Nout)×m2.

[0061] First, let us consider the case shown in Figure 6. This is the case when control is performed along line (1) in Figure 3. In region D2, the voltage-angle product difference ΔX decreases as the input / output voltage ratio d increases. In region D2, ΔX is generally positive. In region C, as the input / output voltage ratio d increases, the voltage-angle product difference ΔX gradually decreases, for example, but transitions to a negative value. When transitioning from region C to region B, ΔX increases sharply. In regions B1 and B2, ΔX is zero. When transitioning from region B to region A, ΔX increases sharply. After that, in region A, ΔX continues to be a positive value. As another example, ΔX is generally constant.

[0062] In this way, even when the control according to (1) in Figure 3 is explained, the control or switching mode is switched, for example, in area C, area B, and area A. The reason for switching the control in this way is to further reduce losses.

[0063] There are various factors that cause losses in DC / DC converters. Examples include transformer iron loss, transformer copper loss, secondary-side conduction loss, secondary-side switching loss, primary-side conduction loss, and primary-side switching loss. Conventionally, these loss factors have been controlled without accurately analyzing their degree of influence. However, to further reduce losses, the inventors have clarified in detail how an increase in the secondary-side DC voltage affects the influence of each of the above factors on losses. Note that an increase in the secondary-side DC voltage is also related to the input / output voltage ratio d in Figures 6 to 9.

[0064] As a result, we found that the proportion of the impact of each of the above-mentioned elements on loss changes as the secondary-side DC voltage increases. Details are limited in this specification because they would involve disclosing know-how, but we found that, for example, in region C, as the secondary-side DC voltage increases, the transformer's iron loss gradually increases from an initial small proportion, and increases sharply, especially in regions close to region B. Furthermore, while primary-side switching loss in region C represents the largest proportion, it is not significantly affected by increases in secondary-side DC voltage. Meanwhile, secondary-side switching loss in region C increases as the secondary-side DC voltage increases. Thus, even within region C, each loss factor exhibits complex behavior as the secondary-side DC voltage increases.

[0065] If control continues in region C as the secondary DC voltage increases, the impact of transformer iron loss will increase rapidly, causing the total loss to increase sharply. Therefore, control will be shifted to region B.

[0066] In this way, the inventors have conducted a detailed study of the loss factors of DC / DC converters, examining the contribution of each loss factor to the total loss in response to an increase in secondary-side DC voltage, and as a result have discovered a methodology for reducing losses over a wide range of secondary-side DC voltages by dividing the loss factors into multiple regions and performing detailed control.

[0067] In particular, the focus is on reducing the primary-side switching loss and the secondary-side switching loss.

[0068] Next, we will explain the case shown in Figure 7. This is the case when control is performed along line (2) in Figure 3. In region D2, as the input / output voltage ratio d increases, the voltage-angle product difference ΔX decreases. In region D2, ΔX is generally positive. In region C, as the input / output voltage ratio d increases, the voltage-angle product difference ΔX gradually decreases, but transitions to a negative value. When transitioning from region C to region B, ΔX increases sharply. In region B2, ΔX is zero. When transitioning from region B2 to region D, ΔX increases sharply. When transitioning from region D2 to region D1, ΔX remains positive. When transitioning from region D1 to region B1, ΔX decreases sharply and becomes zero. When transitioning from region B1 to region A1, ΔX increases sharply and then remains positive. As another example, ΔX is generally constant.

[0069] Next, we will explain the case of Figure 8. This is the case when control is performed along line (3) in Figure 3. In region D2, as the input / output voltage ratio d increases, the voltage-angle product difference ΔX decreases. In region D2, ΔX is generally positive. In region C, as the input / output voltage ratio d increases, the voltage-angle product difference ΔX, for example, gradually decreases, but transitions to a negative value. When transitioning from region C to region D2, ΔX increases sharply. From region D2 to region D1, ΔX, for example, gradually decreases while remaining positive. When transitioning from region D1 to region B1, ΔX decreases sharply and becomes zero. When transitioning from region B1 to region A1, ΔX increases sharply and then remains positive. Also, for example, ΔX is generally constant.

[0070] Next, we will explain the case shown in Figure 9. This is the case when control is performed along line (4) in Figure 3. In region D2, the voltage angle product difference ΔX decreases as the input / output voltage ratio d increases. In region D2, ΔX is generally positive. Near the transition from region D2 to region D1, or near TP, the sign of ΔX reverses. After that, in region D1, it maintains a negative value and continues to decrease.

[0071] 6 to 9, ΔX is positive in region A, zero in regions B1 and B2, negative in region C, positive or negative in region D1, and generally positive in region D2.

[0072] In addition, ΔX is zero in regions B1 and B2. As will be explained later, this is the condition for realizing zero current switching (ZCS), a type of soft switching, and one of the purposes is to reduce switching losses.

[0073] The loss reduction effect achieved by carrying out the above control is explained in Figure 10. In Figure 10, the horizontal axis represents the input / output voltage ratio d, and the vertical axis represents the loss. The vertical axis is set as a numerical value to make the effect easier to understand.

[0074] In the comparative example, losses are high even when the input / output voltage ratio d is 0, but they decrease as the input / output voltage ratio d increases. Then, the input / output voltage ratio d reaches its minimum value near TP. After that, losses increase again sharply as the input / output voltage ratio d increases.

[0075] On the other hand, in the example of control described in this embodiment, the input / output voltage ratio d is suppressed even near 0, and losses are suppressed compared to the comparative example even in the region where the input / output voltage ratio d is low. After that, losses increase as the input / output voltage ratio d increases, but even beyond the vicinity of TP, the sudden increase in losses seen in the comparative example is avoided. As a result, loss suppression is achieved over a wide range of the input / output voltage ratio d.

[0076] In this way, the control of this embodiment and the DC / DC converter using it can suppress losses. In addition, the control circuit 70 issues pulse commands to the primary bridge circuit 20 and the secondary bridge circuit 50 to control the voltage-angle product difference ΔX.

[0077] According to this embodiment, the power conversion efficiency of the power conversion device can be increased compared to the conventional case. Furthermore, even when the output current fluctuates in addition to the input voltage and output voltage fluctuates, the power conversion efficiency can be increased overall in the control of the power conversion device. [Example]

[0078] This embodiment describes an example of the control in the first embodiment from the viewpoint of control waveforms.

[0079] Fig. 11 is a diagram corresponding to Fig. 3. It shows the correspondence between the waveforms described in Fig. 3 and each region in Fig. 12 to Fig. 17. In Fig. 12 to Fig. 17, examples of drive waveforms will be described for each of the white circles A, B1, B2, C, D1, and D2 in Fig. 11.

[0080] In Figures 12 to 17, the horizontal axis represents the phase or angle, with one cycle being 360 degrees. The vertical axis represents the waveform value. For the sake of explanation, current and voltage are mixed together, so they are shown as waveform values. Also, even for Vin_ac and Vout_ac, which are the same voltage, Vout_ac is significantly amplified compared to Vin_ac, so it is difficult to simultaneously display them on the same scale. Therefore, these figures are merely for the purpose of explaining the waveforms.

[0081] Figure 12 shows the drive waveform at point A in Figure 11. Compared to Vin_ac, Vout_ac rises slowly and falls quickly. Iin_ac has a triangular waveform. Note that Iin_ac is generally positive between 90 and 180 degrees and generally negative between 270 and 360 degrees. A more detailed characteristic is that the sign of Iin_ac is either positive or negative near 0, 90, 180, and 270 degrees.

[0082] Figure 13 shows the drive waveform at point B1 in Figure 11. Vout_ac rises and falls slowly relative to Vin_ac. Iin_ac has a deformed trapezoidal waveform with a lower tail. It rises as Vin_ac rises, and reaches its maximum absolute value as Vout_ac rises. It then decreases as an absolute value, begins to decrease as Vin_ac falls, and reaches 0 as Vout_ac falls.

[0083] Figure 14 shows the drive waveform at point B2 in Figure 11. Vout_ac rises and falls slowly relative to Vin_ac. Iin_ac has a deformed trapezoidal waveform with a higher peak at the rear. It rises as Vin_ac rises, reaches an inflection point at the rise of Vout_ac, then increases in absolute value, begins to decrease as Vin_ac falls, and reaches 0 as Vout_ac falls.

[0084] 13 and 14, the inclination of the trapezoid of Iin_ac is reversed. At the boundary between B1 and B2, Iin_ac becomes a trapezoid with no inclination.

[0085] Figure 15 shows the drive waveform at point C in Figure 11. Vout_ac rises quickly and falls slowly relative to Vin_ac. Iin_ac has a triangular waveform, reaching an absolute maximum at the falling edge of Vin_ac. Iin_ac is generally positive when Vout_ac is positive, and generally negative when Vout_ac is negative. A more detailed characteristic is that the sign of Iin_ac is positive or negative near the angles 0°, 90°, 180°, and 270°.

[0086] Figure 16 shows the drive waveform at point D1 in Figure 11. There is an interval between Vin_ac and Vout_ac on both the rising and falling edges. Iin_ac is based on a triangular wave, but its absolute value peaks at the rising or falling edge of Vout_ac. The waveform has two inflection points, one at the falling edge of Vin_ac and one at the falling edge of Vout_ac.

[0087] Figure 17 shows the drive waveform at point D2 in Figure 11. There is an interval between Vin_ac and Vout_ac on both the rising and falling edges. Iin_ac is based on a triangular wave, but its absolute value peaks at the falling edge of Vin_ac as an absolute value. The waveform has two inflection points: the rising edge of Vin_ac as an absolute value and the falling edge of Vout_ac as an absolute value.

[0088] As described above, by controlling the waveform for each region, it is possible to reduce losses in the DC / DC converter and improve conversion efficiency. [Example]

[0089] This embodiment is the same as the second embodiment, but will be described in more detail from the viewpoint of waveform control and soft switching.

[0090] Figure 18A is a re-presentation of Figure 12. The waveform in Figure 18A satisfies the voltage angle product difference condition for soft switching (ZVS), and switching loss can be suppressed. Note that ZVS stands for zero voltage switching, and is an abbreviation of ZERO_VOLTAGE_SWITCHING in English.

[0091] 18A shows the case where the voltage-angle product difference ΔX is positive in region A. Region A can also be called switching mode A.

[0092] FIG. 18B is an enlarged view of the waveform in the 0° to 180° portion of FIG. 18A for detailed explanation.

[0093] In 701, when Vin_ac rises, the current Iin_ac<0, so zero voltage switching (ZVS), which is a type of soft switching, occurs.

[0094] In 702, when Vout_ac rises, the current Iout_ac>0 (equivalent to Iin_ac>0) and thus zero voltage switching (ZVS), which is a type of soft switching, occurs.

[0095] In 703, at the falling edge of Vout_ac, the current Iout_ac<0 (equivalent to Iin_ac<0) and therefore zero voltage switching (ZVS), which is a type of soft switching, occurs.

[0096] In 704, at the falling edge of Vin_ac, the current Iin_ac>0, so zero voltage switching (ZVS), which is a type of soft switching, occurs.

[0097] In 705, at the falling edge of Vin_ac, the current Iin_ac>0, so zero voltage switching (ZVS), which is a type of soft switching, occurs.

[0098] As described above, ZVS switching is performed at each change point, and soft switching can be achieved, thereby suppressing switching loss.

[0099] Next, as a comparative example, an example in which the conditions for soft switching are not satisfied and hard switching occurs will be shown.

[0100] 19A shows an example of waveforms in the case of hard switching, as opposed to the soft switching shown in FIG. 18A, where the voltage-angle product difference ΔX is negative in region A.

[0101] FIG. 19B is an enlarged view of the waveform in the 0° to 180° portion of FIG. 19A for detailed explanation.

[0102] At 711, when Vin_ac rises, the current Iin_ac>0, so hard switching (HS) occurs.

[0103] At 712, when Vout_ac rises, the current Iout_ac>0 (equivalent to Iin_ac>0) and thus zero voltage switching (ZVS) occurs, which is soft switching.

[0104] In 713, at the falling edge of Vout_ac, the current Iout_ac<0 (equivalent to Iin_ac<0) and therefore zero voltage switching (ZVS) which is soft switching occurs.

[0105] At 714, when Vin_ac falls, the current Iin_ac<0, so hard switching (HS) occurs.

[0106] At 715, when Vin_ac falls, current Iin_ac<0, so hard switching (HS) occurs.

[0107] As described above, the waveform in FIG. 19B causes a lot of hard switching, resulting in large switching losses.

[0108] Figure 20A is a re-presentation of Figure 13. The waveform in Figure 20A satisfies the voltage angle product difference condition for soft switching (ZVS or ZCS), and switching loss can be suppressed. ZCS stands for zero current switching, and is an abbreviation for ZERO_CURRENT_SWITCHING in English.

[0109] 20A shows the case where the voltage-angle product difference ΔX is zero in region B1. Region B1 can also be called switching mode B1.

[0110] FIG. 20B is an enlarged view of the waveform in the 0° to 180° portion of FIG. 20A for detailed explanation.

[0111] At 721, when Vin_ac rises, the current Iin_ac=0, so that zero current switching (ZCS) which is soft switching occurs.

[0112] At 722, when Vout_ac rises, the current Iout_ac>0 (equivalent to Iin_ac>0) and thus zero voltage switching (ZVS) which is soft switching occurs.

[0113] In 723, at the falling edge of Vin_ac, the current Iin_ac>0, so that zero voltage switching (ZVS) which is soft switching occurs.

[0114] In 724, at the falling edge of Vout_ac, the current Iout_ac=0 (equivalent to Iin_ac=0), so zero current switching (ZCS) which is soft switching occurs.

[0115] At 725, when Vin_ac falls, the current Iin_ac=0, so that zero current switching (ZCS) occurs, which is soft switching.

[0116] As described above, at each change point, switching is performed using either ZVS or ZCS, realizing soft switching and suppressing switching loss.

[0117] Next, as a comparative example, an example in which the conditions for soft switching are not satisfied and hard switching occurs will be shown.

[0118] 21A shows an example of waveforms in the case of hard switching, as opposed to the soft switching shown in FIG. 20A, where the voltage angle product difference ΔX is positive in region B1.

[0119] FIG. 21B is an enlarged view of the waveform in the 0° to 180° portion of FIG. 21A for detailed explanation.

[0120] At 731, when Vin_ac rises, the current Iin_ac<0, so that zero voltage switching (ZVS) which is soft switching occurs.

[0121] At 732, when Vout_ac rises, the current Iout_ac>0 (equivalent to Iin_ac>0) and thus zero voltage switching (ZVS) occurs, which is soft switching.

[0122] In 733, at the falling edge of Vin_ac, the current Iin_ac>0, so that zero voltage switching (ZVS) which is soft switching occurs.

[0123] At 734, when Vout_ac falls, the current Iout_ac>0 (equivalent to Iin_ac>0) and therefore hard switching (HS) occurs.

[0124] At 735, when Vin_ac falls, the current Iin_ac>0, so that zero voltage switching (ZVS) which is soft switching occurs.

[0125] As described above, the waveform in FIG. 21B causes hard switching, resulting in large switching losses.

[0126] Fig. 22A is a re-presentation of Fig. 15. The waveform in Fig. 22A satisfies the voltage angle product difference condition for soft switching (ZVS), and switching loss can be suppressed.

[0127] 22A shows the case where the voltage-angle product difference ΔX is negative in region C. Region C can also be referred to as switching mode C.

[0128] FIG. 22B is an enlarged view of the waveform in the 0° to 180° portion of FIG. 22A for detailed explanation.

[0129] At 741, when Vin_ac rises, the current Iin_ac<0, so that zero voltage switching (ZVS) which is soft switching occurs.

[0130] In 742, at the falling edge of Vin_ac, the current Iin_ac>0, so that zero voltage switching (ZVS) which is soft switching occurs.

[0131] In 743, when Vout_ac falls, the current Iout_ac<0 (equivalent to Iin_ac<0), so it becomes zero voltage switching (ZVS), which is soft switching. In 744, at the falling edge of Vout_ac, the current Iout_ac<0 (equivalent to Iin_ac<0) and therefore zero voltage switching (ZVS) which is soft switching occurs.

[0132] In 745, at the falling edge of Vin_ac, the current Iin_ac>0, so that zero voltage switching (ZVS) which is soft switching occurs.

[0133] As described above, ZVS switching is performed at each change point, and soft switching can be achieved, thereby suppressing switching loss.

[0134] Next, as a comparative example, an example in which the conditions for soft switching are not satisfied and hard switching occurs will be shown.

[0135] 23A shows an example of waveforms in the case of hard switching, as opposed to the soft switching shown in FIG. 22A, where the voltage angle product difference ΔX is positive in region C.

[0136] FIG. 23B is an enlarged view of the waveform in the 0° to 180° portion of FIG. 23A for detailed explanation.

[0137] At 751, when Vin_ac rises, the current Iin_ac<0, so that zero voltage switching (ZVS) which is soft switching occurs.

[0138] In 752, at the falling edge of Vin_ac, the current Iin_ac>0, so that zero voltage switching (ZVS) which is soft switching occurs.

[0139] In 753, when Vout_ac falls, the current Iout_ac>0 (equivalent to Iin_ac>0) and therefore hard switching (HS) occurs.

[0140] At 754, when Vout_ac falls, the current Iout_ac>0 (equivalent to Iin_ac>0) and therefore hard switching (HS) occurs.

[0141] At 755, when Vin_ac falls, the current Iin_ac>0, so that zero voltage switching (ZVS) which is soft switching occurs.

[0142] As described above, the waveform in FIG. 23B causes hard switching, resulting in large switching losses.

[0143] Next, soft switching and hard switching will be described in more detail with reference to FIGS.

[0144] 24 to 27 focus on one leg circuit and show the operation of soft switching and hard switching. A one leg circuit is a circuit composed of two switching elements, one above the other. Specifically, in the circuit shown in FIG. 1 as an example, on the primary side, 201, 202, 211, and 212 constitute one leg circuit. 203, 204, 213, and 214 constitute another one leg circuit. Similarly, on the secondary side, 501, 502, 511, and 512 constitute one leg circuit. 503, 504, 513, and 514 constitute another one leg circuit.

[0145] Figure 24 shows the definitions of current and voltage in one leg circuit for explaining switching operation. One leg circuit is composed of Tr1, Tr2, D1, and D2. The current and voltage of each element are defined with the direction shown in the figure as positive. 780 is the positive direction of Tr1 current, 781 is the positive direction of D1 current, 782 is the positive direction of Tr2 current, 783 is the positive direction of D2 current, and 785 is the positive direction of the transformer current.

[0146] Based on this definition, soft switching (ZVS or ZCS) and hard switching will be explained in Figures 25 to 27. Figures 25 to 27 show the difference in behavior of the commutation phenomenon due to the transformer current in the center of the arm when commutating from the lower arm to the upper arm in a one-leg circuit.

[0147] Figure 25 shows the case where the transformer current in the center of the arm is negative and the current is commutated from the lower arm to the upper arm. The commutation state is soft switching, which corresponds to the case of ZVS in particular.

[0148] Circuit diagrams 801 to 804 in Fig. 25 are diagrams for explaining the state transitions of commutation, and the periods corresponding to the double-headed arrows at the bottom of the diagrams correspond to the states of each circuit diagram. For example, TM1 to TM2 are in state 801, TM2 to TM3 are in state 802, TM3 to TM4 are in state 803, and TM4 and above are in state 804.

[0149] In the waveform diagram at the bottom of the drawing, the horizontal axis represents, for example, time or angle, and the vertical axis represents current or voltage values. Note that the vertical axis is not an absolute value, but is written to focus on positive / negative values ​​and crossovers.

[0150] In the state of 801, Tr1 is OFF, Tr2 is ON, and a transformer current flows through Tr2.

[0151] In the state 802, both Tr1 and Tr2 transition to the OFF state, the capacitance of Tr1 and Tr2 (which may be the parasitic capacitance of Tr1 and Tr2 or the external capacitance) is charged and discharged, the voltage of Vds1 decreases, and Vds2 increases.

[0152] In the state of 803, Tr1 and Tr2 remain in the OFF state as in the state of 802, but the voltage of Vds1 becomes zero or less (negative), and a transformer current begins to flow in the forward direction of diode D1.

[0153] In the state of 804, Tr1 is ON and Tr2 is OFF, and a transformer current begins to flow through Tr1.

[0154] In FIG. 25, 810 is the Tr1 voltage and also Vds1. 811 is the Tr1 current. 812 is the D1 voltage and also Vds1. 813 is the D1 current. 814 is the Tr2 voltage and also Vds2. 815 is the Tr2 current. 816 is the D2 voltage and also Vds2. 817 is the D2 current.

[0155] 25, switching is performed when the voltage is near zero. That is, due to zero voltage switching (ZVS), switching loss is small.

[0156] Figure 26 shows the case when the transformer current in the center of the arm is zero. The commutation state is soft switching, which corresponds to the case of ZCS in particular.

[0157] Circuit diagrams 821 to 824 in Fig. 26 are diagrams for explaining the state transitions of commutation, and the periods corresponding to the double-headed arrows at the bottom of the diagrams correspond to the states of each circuit diagram. For example, TM5 to TM6 are in state 821, TM6 to TM7 are in state 822, TM7 to TM8 are in state 823, and TM8 and above are in state 824.

[0158] In the waveform diagram at the bottom of the drawing, the horizontal axis represents, for example, time or angle, and the vertical axis represents current or voltage values. Note that the vertical axis is not an absolute value, but is written to focus on positive / negative values ​​and crossovers.

[0159] In the state of 821, Tr1 is OFF and Tr2 is ON, but the current through Tr2 is zero.

[0160] In the state of 822, both Tr1 and Tr2 transition to the OFF state, and Vds1 and Vds2 do not change.

[0161] In the state of 823, Tr1 is ON and Tr2 is OFF, and the charge accumulated in the capacitance component of Tr1 is discharged by turning Tr1 ON. Then, commutation occurs in the state of 823.

[0162] In the state of 824, neither Vds1 nor Vds2 changes.

[0163] In FIG. 26, 830 is the Tr1 voltage and also Vds1. 831 is the Tr1 current. 832 is the D1 voltage and also Vds1. 833 is the D1 current. 834 is the Tr2 voltage and also Vds2. 835 is the Tr2 current. 836 is the D2 voltage and also ds2. 837 is the D2 current.

[0164] At 840, when the Tr1 voltage 830 falls, a momentary pulse occurs in the Tr1 current 831. This causes switching loss when the capacitive charge of Tr1 is discharged.

[0165] In the state transitions from 821 to 824 in FIG. 26, although a switching loss occurs in Tr1 at 840, the loss is small.

[0166] Figure 27 shows the case when the transformer current in the center arm is positive. The commutation state is hard switching.

[0167] Circuit diagrams 851 to 854 in Figure 27 are diagrams for explaining the state transitions of commutation, and the periods corresponding to the double-sided arrows at the bottom of the diagrams correspond to the states of each circuit diagram. For example, TM9 to TM10 are in state 851, TM10 to TM11 are in state 852, TM11 to TM12 are in state 853, and TM12 and above are in state 854.

[0168] In the waveform diagram at the bottom of the drawing, the horizontal axis represents, for example, time or angle, and the vertical axis represents current or voltage values. Note that the vertical axis is not an absolute value, but is written to focus on positive / negative values ​​and crossovers.

[0169] In the state of 851, Tr1 is OFF, Tr2 is ON, and a transformer current flows through Tr2.

[0170] In the state of 852, when both Tr1 and Tr2 transition to the OFF state, a transformer current flows through D2.

[0171] In the 853 state, when Tr1 changes from OFF to ON, a reverse bias voltage is applied to D2, causing a so-called recovery current to flow in D2. This causes a large switching loss known as recovery loss in D2. Meanwhile, a recovery current due to D2 also flows in Tr1, and the total current flowing through Tr1 is the transformer current and the discharge current of the charge accumulated in the capacitance component of Tr1, causing a large switching loss in Tr1. The situation in which these switching losses occur is called hard switching.

[0172] After the transient phenomenon of state 853 ends, state 854 is reached and the commutation ends.

[0173] In FIG. 27, 860 is the Tr1 voltage and also Vds1. 861 is the Tr1 current. 862 is the D1 voltage and also Vds1. 863 is the D1 current. 864 is the Tr2 voltage and also Vds2. 865 is the Tr2 current. 866 is the D2 voltage and also Vds2. 867 is the D2 current.

[0174] 27, 870 and 871 are particularly large switching losses. Switching occurs when the voltage and current are large, resulting in large switching losses.

[0175] As described above, in the state transitions 851 to 854, hard switching results in large switching losses.

[0176] To avoid the occurrence of such hard switching, the control is switched depending on the region, and as a result, the switching waveform is switched, thereby avoiding the occurrence of hard switching and realizing the application of soft switching over a wide voltage region. [Example]

[0177] This embodiment is an example in which Embodiments 1 to 3 are applied singly or in combination to a DC / DC converter, and the DC / DC converter is then applied to a power conversion device. Although the DC / DC converter itself also falls under the category of a power conversion device, in this embodiment the term power conversion device is used to refer to a larger device that has a built-in DC / DC converter.

[0178] FIG. 28A is a schematic external view of an example of a power conversion device, and FIG. 28B is a schematic internal configuration diagram of the example of the power conversion device.

[0179] The power conversion device 900 incorporates one or more DC / DC converters 904. As an example, it has a control device 902, as an example, an exhaust port or exhaust fan 903, and as an example, an air intake 905. Power is supplied to the power conversion device 900 via a power line 910, and power is supplied directly or indirectly from the power conversion device 900 to an output destination device via a power supply line 920.

[0180] Power conversion devices can be used in a variety of applications, including, for example, power controllers for solar power generation, battery controllers for power storage devices, and quick chargers for charging electric vehicles.

[0181] As described above, the power conversion device of this embodiment applies either or both of the first and second embodiments to a DC / DC converter, and the DC / DC converter itself or a power conversion device incorporating the DC / DC converter can suppress losses and provide a power conversion device with high conversion efficiency. [Example]

[0182] This embodiment is an example in which the first to third embodiments are applied alone or in combination to a DC / DC converter, and the DC / DC converter is used in a rapid charger. Alternatively, this embodiment is an example in which the power conversion device of the fourth embodiment is applied to a rapid charger.

[0183] Various types of quick chargers will be described as examples using Figures 29A to 29E. Note that quick chargers are sometimes called EV-Chargers when used to supply power to electric vehicles.

[0184] FIG. 29A is an example of a conceptual diagram of the exterior shape of a standalone quick charger. Power is supplied to quick charger main body 950 via power line 910. One example includes a display device 951 that allows the user to perform charging operations, and this displays charging time, charging status, billing information, etc. 952 is a payment terminal for paying the bill. A connector 961 connects to the object to be charged, such as an electric vehicle. 960 is a power supply cable. The connector 961 and power supply cable 960 are constructed in accordance with the corresponding standards.

[0185] Fig. 29B is an example of a schematic internal configuration diagram of Fig. 29A. It has a built-in DC / DC converter or power conversion device 904. Power supplied from a power line 910 passes through a control device 902 and is then supplied to the DC / DC converter or power conversion device 904. The control device 902 determines whether to shut off the circuit or power in the event of an abnormality, whether to allow power supply in relation to billing processing, and controls the operation of the DC / DC converter or power conversion device 904. Note that the control device 902 may be configured with multiple functional units integrated together or distributed.

[0186] Fig. 29C is another example of a schematic internal configuration diagram of a quick charger. The difference from Fig. 29B is that it has multiple built-in DC / DC converters or power conversion devices 904, each connected directly or indirectly to a power supply cable 960 and a connector 961. In this way, by allowing one quick charger to charge multiple devices, it is possible to reduce the installation space for the quick charger main body 950, reduce overall costs, and simplify management.

[0187] 29D shows that the quick charger is separated into two parts: a power converter side unit 981 and a charge target side unit 982, which together form a quick charger main body 950. The power converter side unit 981 and the charge target side unit 982 are connected by a high-voltage supply cable 970. An air intake 905 may be provided in all parts including those shown in FIGS. 29A to 29D.

[0188] In this way, by separating the power converter side unit 981 and the charge target side unit 982, the power converter side units 981 can be centrally arranged, particularly in large-scale charging spots where many quick charger main bodies 950 are installed, making management easier. In addition, by arranging the charge target side units 982 close to the object to be charged, for example close to each parking space in a parking lot, convenience for users can be improved.

[0189] FIG. 29E is an example combining FIG. 29D and FIG. 29C. Note that this also includes a case where multiple charge target units 982 are provided for one power converter side unit 981. Also, throughout FIG. 29A to FIG. 29E, it includes both cases where charging is performed directly and indirectly along the path from the rapid charger to the target to be charged. Also, the connection from the DC / DC converter or power conversion device 904 to the connector 961 includes both direct and indirect connections. One example of the intention of this description is to realize, for example, a large current by bundling outputs from multiple DC / DC converters or power conversion devices 904 using a switch or the like and supplying them to a single power feed cable 960.

[0190] 29A to 29E have been described primarily with the intention of supplying power from a rapid charging device to an external device, such as an electric vehicle. However, the present invention also includes cases where the rapid charging device receives power from an external device, such as an electric vehicle, and operates as a so-called external power feeder. This can also be called a rapid power receiving device.

[0191] The DC / DC converters or power conversion devices described in Examples 1 to 5 have low loss and excellent conversion efficiency. Therefore, their application to rapid chargers, which will be installed in large numbers as part of the social infrastructure in the future, is an effective technology for reducing power loss throughout society. Furthermore, as shown in FIG. 10, the DC / DC converters or power conversion devices described in Examples 1 to 5 can operate with reduced loss over a wide output voltage range. Therefore, they are suitable technologies for rapid chargers, which are expected to increasingly use higher charging voltages in the future to reduce charging times. This is evident from the fact that the difference in loss between the comparative example and Examples in FIG. 10 increases as the input / output voltage ratio d increases, i.e., as the output voltage increases. As such, the performance of rapid chargers incorporating the various technologies described above is an important technology whose usefulness will increase in the future.

[0192] The above examples illustrate the ideas and concepts of the present invention. Of course, examples realized by combining the examples are also included within the scope of the present invention. Furthermore, as long as the disclosed ideas and concepts are used, modifications and similar examples are also included within the scope of the present invention.

[0193] Furthermore, one example of the present invention described using the above embodiments can also be expressed as follows.

[0194] <Part 1> an input-side bridge circuit and an output-side bridge circuit; a transformer disposed between the input-side bridge circuit and the output-side bridge circuit; A power conversion device including a control unit that controls the input side bridge circuit and the output side bridge circuit, The control unit m1 is a Hi period of the input voltage input from the input-side bridge circuit to the transformer; m2 is a Hi period of the output voltage output from the transformer to the output-side bridge circuit; For m12, which is the difference between the center of the m1 period and the center of the m2 period, If the horizontal axis is (m1-m2) / 2 and the vertical axis is (m1+m2) / 2, (A) The range surrounded by the position where the horizontal axis is 90 and the vertical axis is 90, the position where the horizontal axis is the absolute value m12 and the vertical axis is the absolute value m12, and the position where the horizontal axis is the absolute value m12 and the vertical axis is 180-absolute value m12 is defined as region A. (B) The range surrounded by the horizontal axis range between -absolute value m12 and absolute value m12 and the vertical axis range between absolute value m12 and (180-absolute value m12) is defined as region B. (C) The range surrounded by the position where the horizontal axis is -90 and the vertical axis is 90, the position where the horizontal axis is -absolute value m12 and the vertical axis is absolute value m12, and the position where the horizontal axis is -absolute value m12 and the vertical axis is 180-absolute value m12 is defined as region C. When the number of turns of the primary winding of the transformer is Nin and the number of turns of the secondary winding is Nout, the voltage angle product difference ΔX is expressed as follows, where Vin is the input voltage to the input side bridge circuit and Vout is the output voltage to the output side bridge circuit: Set △X=Vin×m1-Vout×(Nin / Nout)×m2, The power conversion device in which the control unit controls m1 and m2 while switching between the region A, region B, and region C so that the voltage-angle product difference ΔX becomes a predetermined value. <Part 2> The region B further comprises: (B1) The range of the horizontal axis between 0 and absolute value m12 is defined as region B1, (B2) The power conversion device according to <Item 1>, wherein the range of the horizontal axis between −absolute value m12 and 0 is region B2. <Part 3> In the power conversion device according to <Item 2>, when controlling m1 and m2, the control unit controls the voltage angle product difference ΔX while switching between the region A, region B, and region C with respect to an input / output voltage ratio, which is a value obtained by dividing the output voltage output from the transformer to the output-side bridge circuit by the input voltage input to the transformer from the input-side bridge circuit. <Part 4> The power conversion device according to <Item 3>, wherein in the region C, the voltage angle product difference ΔX is controlled to monotonically decrease as the input / output voltage ratio increases. <Part 5> The power conversion device according to <Item 3>, wherein the voltage angle product difference ΔX is controlled to change rapidly when transitioning between the region B and another region as the input / output voltage ratio increases. <Part 6> The power conversion device according to <Item 5>, wherein the voltage angle product difference ΔX is controlled to increase sharply at the time of transition from the region C to the region B as the input / output voltage ratio increases. <Part 7> The power conversion device according to <No. 6>, wherein the voltage angle product difference ΔX is controlled to increase sharply at the time of transition from the region B to the region A as the input / output voltage ratio increases. <Part 8> (D) The power conversion device described in <No. 7> is controlled to have a region D surrounded by the position where the horizontal axis is -absolute value m12 and the vertical axis is 180-absolute value m12, the position where the horizontal axis is absolute value m12 and the vertical axis is 180-absolute value m12, and the position where the horizontal axis is 0 and the vertical axis is 180. <No. 9> The power conversion device according to <Item 8>, wherein the voltage angle product difference ΔX is controlled to be substantially constant in the region B as the input / output voltage ratio increases. <Part 10> The power conversion device according to <Item 9>, wherein the voltage angle product difference ΔX is controlled to be substantially constant in the region A as the input / output voltage ratio increases. <Part 11> The power conversion device according to <Item 9>, wherein the voltage angle product difference ΔX is controlled to monotonically decrease in the region C and the region D as the input / output voltage ratio increases. <Part 12> A power conversion device that performs soft switching by the control described in any one of <Item 1> to <Item 11>. <Part 13> A rapid charging device including the power conversion device according to any one of <Item 1> to <Item 11>. <Part 14> The quick charging device according to <Item 13>, further comprising a connector for connection to an automobile, and a connection cable for connecting the quick charging device to the connector. <Part 15> The quick charging device according to <Item 14>, wherein power is supplied directly or indirectly from the power conversion device to the connection connector. <Part 16> The quick charging device described in <No. 15>, wherein the power conversion device supports bidirectional power supply and has a power supply mode in which the power conversion device supplies power to the automobile and a power receiving mode in which the power conversion device receives power from the automobile, and in the power receiving mode, the roles of the input side bridge circuit and the output side bridge circuit of the power conversion device are controlled to be reversed. <Part 17> A rapid charging device having the power conversion device described in <Item 12>. <Part 18> The quick charging device according to <Item 17>, comprising a connector for connection to an automobile and a connection cable for connecting the quick charging device to the connector for connection. <Part 19> The quick charging device according to <Item 18>, wherein power is supplied directly or indirectly from the power conversion device to the connection connector. <Part 20> The power conversion device supports bidirectional power supply and has a power supply mode in which power is supplied from the power conversion device to the automobile and a power receiving mode in which power is supplied from the automobile to the power conversion device, and in the power receiving mode, the roles of the input side bridge circuit and the output side bridge circuit of the power conversion device are controlled to be reversed. [Explanation of symbols]

[0195] 20: Primary bridge circuit 40: Trance 10, 60: Capacitor 50: Secondary bridge circuit 70: Control circuit 201, 202, 203, 204: Primary side transistors 211, 212, 213, 214: Primary diodes 501, 502, 503, 504: Secondary transistors 511, 512, 513, 514: Secondary diodes d: Input / output voltage ratio m1: Hi period of the input voltage Vin_ac on the first bridge circuit side m2: Hi period of the output voltage Vout_ac on the second bridge circuit side m12: Phase difference or angle difference between the output voltages of the first bridge circuit and the second bridge circuit ΔX: Voltage angle product difference 900: Power conversion device main body 902: Control device 904: DC / DC converter 910: Power lines 950: Rapid charging device 960: Connection cable 961: Connector 970: High voltage supply cable 981: Power converter unit 982: Unit to be charged

Claims

1. An input bridge circuit and an output bridge circuit, A transformer is positioned between the input bridge circuit and the output bridge circuit. A power conversion device comprising the input bridge circuit and the output bridge circuit, A first mode in which the input voltage pulse width and the output voltage pulse width are individually controlled such that the difference between the voltage angle product of the input side and the voltage angle product of the output side falls within a first range, The system includes a second mode in which the input voltage pulse width and the output voltage pulse width are individually controlled such that the difference between the voltage angle product of the input side and the voltage angle product of the output side falls within a second range. The power conversion device is characterized in that the control unit selects either the first mode or the second mode based on the input / output voltage ratio and the output current.

2. A power conversion device according to Claim 1, In the first mode, the voltage-angle product on the input side is controlled to be greater than the voltage-angle product on the output side. In the second mode, the power converter is characterized by controlling the input voltage angle product to be smaller than the output voltage angle product.

3. A power conversion device according to Claim 1, The system further includes a third mode in which the input voltage pulse width and the output voltage pulse width are individually controlled such that the difference between the voltage angle product of the input side and the voltage angle product of the output side falls within a third range. The power conversion device is characterized in that the control unit selects one of the first mode, the second mode, or the third mode based on the input / output voltage ratio and the output current.

4. A power conversion device according to claim 3, A power converter characterized in that the absolute value of the third value belonging to the third range in the third mode is smaller than the absolute value of the first value belonging to the first range in the first mode and the absolute value of the second value belonging to the second range in the second mode.

5. A power conversion device according to claim 3, The power conversion device is characterized in that, in the third mode, the control unit controls the voltage angle product on the input side and the voltage angle product on the output side to be equal.

6. A power conversion device according to claim 3, The control unit determines the difference between the voltage angle product on the input side and the voltage angle product on the output side based on the input / output voltage ratio and the output current. A power conversion device characterized by selecting at least one of the first mode, the second mode, and the third mode according to the determined difference value.

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