Power conversion device

Abstract

To reduce the influence of a dead zone.SOLUTION: The power conversion device 10 includes a primary full-bridge circuit 30 including a plurality of primary switching elements Q1 to Q4, a secondary full-bridge circuit 40 including a plurality of secondary switching elements Q5 to Q8, and a controller 50. The control unit 50 performs phase shift control. The controller 50 derives the first phase shift amount Φ 1 from the current deviation Δ Iout between the target current Itgt and the output current Iout. When the first phase shift amount Φ 1 is included in the range of the dead zone D derived based on the input voltage Vin to the power conversion device 10 and the output voltage Vout of the power conversion device 10, the control part 50 sets the second phase shift amount Φ 2 outside the range of the dead zone as the phase shift amount Φ.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] A DAB converter (dual active bridge DC / DC converter) includes a transformer, a primary full-bridge circuit, a secondary full-bridge circuit, and a control unit. The transformer includes a primary winding and a secondary winding. The primary full-bridge circuit includes multiple primary switching elements. The secondary full-bridge circuit includes multiple secondary switching elements.

[0003] A phase-shift control method is used for DAB converters. In this method, the on-times of multiple primary-side switching elements and multiple secondary-side switching elements are constant. In this method, power is transmitted by creating a phase difference between the on-off switching of the primary-side switching elements and the on-off switching of the secondary-side switching elements.

[0004] In the phase shift method, there is a dead zone where the output does not change with respect to the amount of change in the phase shift. The power conversion device disclosed in Patent Document 1 reduces the influence of the dead zone by using a PWM (Pulse Width Modulation) method. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2023-84037 Summary of the Invention [Problem to be solved by the invention]

[0006] The PWM method requires controlling the on-time of multiple primary-side switching elements and multiple secondary-side switching elements, which complicates the control. For this reason, it is necessary to use a phase shift method to reduce the effects of the dead band. [Means for solving the problem]

[0007] A power conversion device that solves the above problem includes: a transformer unit having a primary winding, a secondary winding, and a reactor connected to at least one of the primary winding or the secondary winding; a primary full bridge circuit connected to the primary winding and having a plurality of primary switching elements; a secondary full bridge circuit connected to the secondary winding and having a plurality of secondary switching elements; and a control unit that performs phase shift control to transfer power between the primary full bridge circuit and the secondary full bridge circuit by controlling the phase shift amount between the plurality of primary switching elements and the plurality of secondary switching elements, wherein the control unit derives a first phase shift amount from the deviation between a target output value and an actual output value, and when the first phase shift amount is within a dead band derived based on an input voltage to the power conversion device and an output voltage of the power conversion device, sets a second phase shift amount outside the dead band as the phase shift amount.

[0008] When the first phase shift amount falls within the dead band, the control unit sets the second phase shift amount outside the dead band as the phase shift amount. Because the second phase shift amount is outside the dead band, the actual value of the output can be made to track the target value. Therefore, the influence of the dead band can be reduced.

[0009] In the power conversion device, the first phase shift amount may be derived using a first feedback gain, and the second phase shift amount may be derived from the deviation using a second feedback gain greater than the first feedback gain.

[0010] In the power conversion device, the control unit may derive the second phase shift amount by adding or subtracting a correction value to or from the first phase shift amount. [Effects of the Invention]

[0011] According to the present invention, the influence of the dead zone can be reduced. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a circuit diagram of a power conversion device. [Figure 2] FIG. 2 is a time chart showing the relationship between the on / off state of the switching element and the transformer current. [Figure 3] FIG. 3 is a time chart showing the relationship between the amount of phase shift and the output current. [Figure 4] FIG. 4 is a diagram showing the output current, target current, phase shift amount, and input voltage of the power conversion device of the comparative example. [Figure 5] FIG. 5 is a diagram showing the output current, target current, phase shift amount, and input voltage of the power conversion device of the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0013] As shown in Fig. 1, the power supply system 100 includes a DC power supply 110, a load 120, and a power conversion device 10. The DC power supply 110 inputs DC power to the power conversion device 10. The DC power supply 110 is, for example, a battery or a power supply circuit. The power supply circuit is, for example, an AC / DC converter that converts AC power into DC power and outputs it. The load 120 is, for example, a secondary battery that can charge and discharge DC power. The secondary battery is, for example, a lithium-ion battery or a lead-acid battery.

[0014] <Power conversion device> The power conversion device 10 is a dual active-bridge DC / DC converter. The power conversion device 10 is provided between a DC power supply 110 and a load 120. The power conversion device 10 is capable of converting DC power input from the DC power supply 110 and outputting the converted power to the load 120. The power conversion device 10 is capable of converting DC power input from the load 120 and outputting the converted power to the DC power supply 110. In other words, the power conversion device 10 is a bidirectional converter that can output power input to its primary side from its secondary side and can also output power input to its secondary side from its primary side. In the following description, the primary side is treated as the input and the secondary side as the output. In other words, the power conversion device 10 converts a DC voltage input from the DC power supply 110 and outputs the converted power to the load 120.

[0015] The power conversion device 10 includes two primary terminals 11 and 12 and two secondary terminals 13 and 14. A DC power supply 110 is electrically connected to the primary terminals 11 and 12. A load 120 is electrically connected to the secondary terminals 13 and 14.

[0016] The power conversion device 10 includes a transformer unit TS. The transformer unit TS includes a transformer 20 and reactors L1 and L2. The transformer 20 is an insulated type. The transformer 20 includes a magnetic core 21, a primary winding 22, and a secondary winding 23. The primary winding 22 and the secondary winding 23 are wound around the core 21. The transformer 20 is connected to reactors L1 and L2. The reactors L1 and L2 may be elements such as choke coils, or may be leakage inductances of the primary winding 22 and the secondary winding 23. The reactor L1 is connected to the primary winding 22. The reactor L2 is connected to the secondary winding 23. The transformer unit TS may include only one of the two reactors L1 and L2.

[0017] The power conversion device 10 includes a primary-side full-bridge circuit 30. The primary-side full-bridge circuit 30 includes a first leg 31 and a second leg 32. The first leg 31 and the second leg 32 are connected to primary-side terminals 11 and 12 so as to be connected in parallel with each other. As a result, the primary-side full-bridge circuit 30 is electrically connected to a DC power supply 110 via the primary-side terminals 11 and 12. The first leg 31 includes a first switching element Q1, a second switching element Q2, and capacitors C1 and C2. The first switching element Q1 and the second switching element Q2 are connected in series with each other. The second leg 32 includes a third switching element Q3, a fourth switching element Q4, and capacitors C3 and C4. The third switching element Q3 and the fourth switching element Q4 are connected in series with each other. The first switching element Q1 and the third switching element Q3 form an upper arm. The second switching element Q2 and the fourth switching element Q4 form a lower arm.

[0018] The first switching element Q1, the second switching element Q2, the third switching element Q3, and the fourth switching element Q4 are a plurality of primary-side switching elements Q1 to Q4. The primary-side switching elements Q1 to Q4 are, for example, n-type metal oxide semiconductor field effect transistors (MOSFETs). The primary-side switching elements Q1 to Q4 may also be p-type MOSFETs, IGBTs (insulated gate bipolar transistors), or GaN-HEMTs.

[0019] The capacitors C1 to C4 are connected in parallel to the primary side switching elements Q1 to Q4, respectively. The capacitors C1 to C4 may be parasitic capacitances, elements, or a combination of parasitic capacitances and elements.

[0020] The connection point between the first switching element Q1 and the second switching element Q2 is connected to one end of the primary winding 22 via the reactor L1, and the connection point between the third switching element Q3 and the fourth switching element Q4 is directly connected to the other end of the primary winding 22. In other words, the primary full-bridge circuit 30 is connected to the primary winding 22.

[0021] The power conversion device 10 includes a primary-side capacitor 15. The primary-side capacitor 15 is provided between the primary-side terminals 11 and 12 and the primary-side full-bridge circuit 30. The power conversion device 10 includes a primary voltage sensor 37. The primary voltage sensor 37 is connected to the primary terminals 11 and 12. The primary voltage sensor 37 detects an input voltage Vin input from the DC power supply 110 to the power conversion device 10.

[0022] The power conversion device 10 includes a secondary-side full-bridge circuit 40. The secondary-side full-bridge circuit 40 includes a third leg 41 and a fourth leg 42. The third leg 41 and the fourth leg 42 are connected to secondary-side terminals 13 and 14 so as to be connected in parallel with each other. As a result, the secondary-side full-bridge circuit 40 is electrically connected to a load 120. The third leg 41 includes a fifth switching element Q5, a sixth switching element Q6, and capacitors C5 and C6. The fifth switching element Q5 and the sixth switching element Q6 are connected in series with each other. The fourth leg 42 includes a seventh switching element Q7, an eighth switching element Q8, and capacitors C7 and C8. The seventh switching element Q7 and the eighth switching element Q8 are connected in series with each other. The fifth switching element Q5 and the seventh switching element Q7 form an upper arm. The sixth switching element Q6 and the eighth switching element Q8 form a lower arm.

[0023] The fifth switching element Q5, the sixth switching element Q6, the seventh switching element Q7, and the eighth switching element Q8 are a plurality of secondary-side switching elements Q5 to Q8. The secondary-side switching elements Q5 to Q8 are, for example, n-type MOSFETs. The secondary-side switching elements Q5 to Q8 may also be p-type MOSFETs, IGBTs, or GaN-HEMTs.

[0024] The capacitors C5 to C8 are connected in parallel to the secondary side switching elements Q5 to Q8, respectively. The capacitors C5 to C8 may be parasitic capacitances, elements, or a combination of parasitic capacitances and elements.

[0025] The connection point between the fifth switching element Q5 and the sixth switching element Q6 is connected to one end of the secondary winding 23 via the reactor L2, and the connection point between the seventh switching element Q7 and the eighth switching element Q8 is directly connected to the other end of the secondary winding 23. In other words, the secondary full-bridge circuit 40 is connected to the secondary winding 23.

[0026] The power conversion device 10 includes a secondary-side capacitor 16. The secondary-side capacitor 16 is provided between the secondary-side terminals 13, 14 and the secondary-side full-bridge circuit 40. The output power of the secondary side full bridge circuit 40 is supplied to a load 120 .

[0027] The power conversion device 10 includes a secondary voltage sensor 47. The secondary voltage sensor 47 is connected to the secondary terminals 13 and 14. The secondary voltage sensor 47 detects the output voltage Vout of the power conversion device 10.

[0028] The power conversion device 10 includes a current sensor 48. The current sensor 48 is connected to the secondary side terminal 13. The current sensor 48 detects the output current Iout of the power conversion device 10. The power conversion device 10 includes a control unit 50. The control unit 50 controls a plurality of primary side switching elements Q1 to Q4 and a plurality of secondary side switching elements Q5 to Q8 to convert an input voltage Vin into an output voltage Vout.

[0029] The control unit 50 switches the switching patterns of the primary-side switching elements Q1 to Q4 so that the voltage applied to the series connection 24 of the primary-side winding 22 and the reactor L1 switches between two levels: positive and negative. The switching patterns of the primary-side switching elements Q1 to Q4 include a first pattern and a second pattern. The first pattern is a switching pattern in which the first switching element Q1 is turned on, the second switching element Q2 is turned off, the third switching element Q3 is turned off, and the fourth switching element Q4 is turned on. The second pattern is a switching pattern in which the first switching element Q1 is turned off, the second switching element Q2 is turned on, the third switching element Q3 is turned on, and the fourth switching element Q4 is turned off.

[0030] The control unit 50 switches the switching patterns of the secondary-side switching elements Q5 to Q8 so that the voltage applied to the series connection 25 of the secondary-side winding 23 and the reactor L2 switches between two levels: positive and negative. The switching patterns of the secondary-side switching elements Q5 to Q8 include a third pattern and a fourth pattern. The third pattern is a switching pattern in which the fifth switching element Q5 is turned on, the sixth switching element Q6 is turned off, the seventh switching element Q7 is turned off, and the eighth switching element Q8 is turned on. The fourth pattern is a switching pattern in which the fifth switching element Q5 is turned off, the sixth switching element Q6 is turned on, the seventh switching element Q7 is turned on, and the eighth switching element Q8 is turned off.

[0031] 2, the control unit 50 performs phase shift control. Phase shift control is a control method for varying the transformer current I1 by controlling the phase shift amount Φ [rad] between the primary-side switching elements Q1 to Q4 and the secondary-side switching elements Q5 to Q8, thereby transmitting power between the primary-side full-bridge circuit 30 and the secondary-side full-bridge circuit 40. The transformer current I1 is a current that flows through the transformer 20. In this embodiment, the current that flows through the primary-side winding 22 is the transformer current I1.

[0032] In phase shift control, the on-times of the primary-side switching elements Q1 to Q4 and the secondary-side switching elements Q5 to Q8 are kept constant. For example, the on-times of the primary-side switching elements Q1 to Q4 and the secondary-side switching elements Q5 to Q8 are kept in a 1:1 ratio to their off-times. That is, the duty ratio of the primary-side switching elements Q1 to Q4 and the secondary-side switching elements Q5 to Q8 is 50%.

[0033] The phase shift amount Φ is the phase difference between the on-off switching of the primary-side switching elements Q1 to Q4 and the on-off switching of the secondary-side switching elements Q5 to Q8. In the example shown in Fig. 2, the phase shift amount Φ is the phase difference between the off switching of the primary-side switching elements Q1, Q4 and the off switching of the secondary-side switching elements Q5, Q8. Because the on-off switching frequency of the primary-side switching elements Q1 to Q4 and the on-off switching frequency of the secondary-side switching elements Q5 to Q8 are the same, the phase difference between the on-off switching of the primary-side switching elements Q1, Q4 and the on-off switching of the secondary-side switching elements Q5, Q8 is also the phase shift amount Φ. Similarly, the phase difference between the turning on of the primary side switching elements Q2, Q3 and the turning on of the secondary side switching elements Q6, Q7 is also a phase shift amount Φ, and the phase difference between the turning off of the primary side switching elements Q2, Q3 and the turning off of the secondary side switching elements Q6, Q7 is also a phase shift amount Φ.

[0034] In the phase shift control, the first pattern of the primary-side switching elements Q1 to Q4 corresponds to the third pattern of the secondary-side switching elements Q5 to Q8. When the control unit 50 switches the second pattern of the primary-side switching elements Q1 to Q4 to the first pattern, it switches the fourth pattern of the secondary-side switching elements Q5 to Q8 to the third pattern. The second pattern of the primary-side switching elements Q1 to Q4 corresponds to the fourth pattern of the secondary-side switching elements Q5 to Q8. When the control unit 50 switches the first pattern of the primary-side switching elements Q1 to Q4 to the second pattern, it switches the third pattern of the secondary-side switching elements Q5 to Q8 to the fourth pattern. The phase difference between the switching of the switching pattern of the primary-side switching elements Q1 to Q4 and the switching of the switching pattern of the secondary-side switching elements Q5 to Q8 at this time is the phase shift amount Φ.

[0035] When the switching pattern of the primary-side switching elements Q1 to Q4 changes faster than the switching pattern of the secondary-side switching elements Q5 to Q8, power is transmitted from the primary-side full-bridge circuit 30 to the secondary-side full-bridge circuit 40. When the switching pattern of the primary-side switching elements Q1 to Q4 changes slower than the switching pattern of the secondary-side switching elements Q5 to Q8, power is transmitted from the secondary-side full-bridge circuit 40 to the primary-side full-bridge circuit 30.

[0036] As shown in Figure 3, as the phase shift amount Φ increases, the output current Iout increases. Within the range in which the phase shift amount Φ can be changed, there is a dead zone D [rad] where the output current Iout does not change even when the phase shift amount Φ is changed. If the number of turns in the primary winding 22 of the transformer 20 is N1 and the number of turns in the secondary winding 23 is N2, the equivalent voltage ratio when the turns ratio is converted to 1:1 is the equivalent voltage ratio (Vout × N1) / (Vin × N2). The dead zone D occurs when the equivalent voltage ratio is lower than 1.

[0037] The dead zone D is caused by the influence of the dead time DT. When switching the switching pattern of the primary-side switching elements Q1 to Q4, the dead time DT is set so that all four primary-side switching elements Q1 to Q4 are not turned on simultaneously. The same applies to the secondary-side switching elements Q5 to Q8. The dead time DT causes the dead zone D, in which an increase in the phase shift amount Φ is not reflected in the output current Iout. If the phase shift amount Φ is within the range of the dead zone D, changing the phase shift amount Φ does not change the output. Therefore, if a ripple is included in the input voltage Vin, it is difficult to reduce this ripple, and there is a risk that a large ripple will be included in the output current Iout. In this embodiment, the power conversion device 10 is controlled so as to reduce the influence of the dead zone D. A detailed description will be given below.

[0038] <Control unit> 1, the control unit 50 includes an AD converter 51 corresponding to the current sensor 48, an AD converter 52 corresponding to the primary-side voltage sensor 37, and an AD converter 53 corresponding to the secondary-side voltage sensor 47. The AD converter 51 converts the analog value acquired from the current sensor 48 into a digital value and outputs it as an output current Iout. The AD converter 52 converts the analog value acquired from the primary-side voltage sensor 37 into a digital value and outputs it as an input voltage Vin. The AD converter 53 converts the analog value acquired from the secondary-side voltage sensor 47 into a digital value and outputs it as an output voltage Vout.

[0039] The control unit 50 includes a subtractor 54. The subtractor 54 receives the target value and actual value of the output of the power conversion device 10. The subtractor 54 outputs a value obtained by subtracting the actual value of the output from the target value of the output as a deviation. In this embodiment, feedback control is performed to make the output current Iout follow the target current Itgt, so the target value of the output is the target current Itgt. The actual value of the output is the output current Iout detected by the current sensor 48. The deviation is a current deviation ΔIout obtained by subtracting the output current Iout from the target current Itgt. The target current Itgt is input to the control unit 50 from, for example, a higher-level control device.

[0040] The control unit 50 includes a dead zone deriving unit 55. The dead zone deriving unit 55 receives the input voltage Vin output from the AD converter 52 and the output voltage Vout output from the AD converter 53. The dead zone deriving unit 55 derives a dead zone D, which is a range of the amount of phase shift corresponding to the dead zone, based on the input voltage Vin and the output voltage Vout. For example, the dead zone deriving unit 55 derives a maximum value DZ, which is the amount of phase shift corresponding to the maximum value of the dead zone D, from the input voltage Vin, the output voltage Vout, and the turns ratio of the transformer 20. MAX The dead zone deriving unit 55 derives a minimum value DZ, which is a phase shift amount corresponding to the minimum value of the dead zone D, from the input voltage Vin, the output voltage Vout, the dead time DT, the switching period, and the turns ratio of the transformer 20. MIN The maximum value of the dead zone D is DZ. MAX , and the minimum value DZ of the dead zone D MIN The dead zone deriving unit 55 may derive the maximum value DZ MAX and the minimum value DZ MIN Output.

[0041] The control unit 50 includes a feedback control unit 60. The feedback control unit 60 performs feedback control using the current deviation ΔIout. The feedback control unit 60 includes a first phase shift amount derivation unit 61, a second phase shift amount derivation unit 62, and a comparison unit 63. The feedback control may be at least one of proportional control, integral control, and differential control. For example, the feedback control unit 60 may be a proportional-integral control.

[0042] The subtractor 54, the dead zone derivation unit 55, and the feedback control unit 60 may be functional units that function by a computer performing predetermined processing, for example. The computer includes a processor and a storage unit. The processor is, for example, a central processing unit (CPU), a graphics processing unit (GPU), or a digital signal processor (DSP). The storage unit includes random access memory (RAM) and read-only memory (ROM). The storage unit stores program code or instructions configured to cause the processor to execute processing. The storage unit, i.e., computer-readable medium, includes any available medium accessible by a general-purpose or special-purpose computer. The computer may be configured with hardware circuits such as an application-specific integrated circuit (ASIC) or a field-programmable gate array (FPGA). The computer, which is a processing circuit, may include one or more processors operating according to a computer program, one or more hardware circuits such as ASICs or FPGAs, or a combination thereof.

[0043] The current deviation ΔIout is input to the first phase shift amount derivation unit 61. The first phase shift amount derivation unit 61 derives the first phase shift amount Φ1 by feedback control. The first phase shift amount derivation unit 61 derives the first phase shift amount Φ1 using the current deviation ΔIout and a first feedback gain. The first feedback gain is a feedback gain that does not take into account the dead zone D. In other words, the first feedback gain is a feedback gain for deriving the phase shift amount Φ when the dead zone D does not exist in the phase shift amount Φ. The first phase shift amount derivation unit 61 outputs the derived first phase shift amount Φ1.

[0044] The current deviation ΔIout is input to the second phase shift amount derivation unit 62. The second phase shift amount derivation unit 62 derives the second phase shift amount Φ2 by feedback control. The second phase shift amount derivation unit 62 derives the second phase shift amount Φ2 using the current deviation ΔIout and a second feedback gain. The second feedback gain is a feedback gain that takes into account the dead band D. In other words, the second feedback gain is set so that when the dead band D exists in the phase shift amount Φ, the derived second phase shift amount Φ2 is outside the range of the dead band D.

[0045] The second feedback gain is greater than the first feedback gain. It is sufficient that the second feedback gain is greater than the first feedback gain with respect to at least one of the proportional gain, integral gain, and differential gain included in the feedback gain. For example, when proportional-integral control is performed as the feedback control, the second feedback gain and the first feedback gain each include a proportional gain and an integral gain. In this case, the proportional gain of the second feedback gain may be greater than the proportional gain of the first feedback gain, or the integral gain of the second feedback gain may be greater than the integral gain of the first feedback gain. Furthermore, the second feedback gain may be greater than the first feedback gain with respect to both the proportional gain and the integral gain. The second phase shift amount derivation unit 62 outputs the derived second phase shift amount Φ2.

[0046] The comparator 63 receives the first phase shift amount Φ1 output from the first phase shift amount deriving unit 61, the second phase shift amount Φ2 output from the second phase shift amount deriving unit 62, and the maximum value DZ MAX and the minimum value DZ MIN The comparator 63 outputs the first phase shift amount Φ1 or the second phase shift amount Φ2 as the phase shift amount Φ. The comparator 63 compares the first phase shift amount Φ1 with the maximum value DZ MAX and minimum value DZ MIN The comparator 63 compares the first phase shift amount Φ1 with the minimum value DZ MIN Greater than or equal to the maximum value DZ MAXIn the following case, that is, when the first phase shift amount Φ1 is within the range of the dead zone D, the second phase shift amount Φ2 is output as the phase shift amount Φ. MIN Less than or maximum value DZ MAX If it is larger, that is, if the first phase shift amount Φ1 is outside the range of the dead zone D, the first phase shift amount Φ1 is output as the phase shift amount Φ.

[0047] The control unit 50 includes a drive circuit 70. The drive circuit 70 receives the phase shift amount Φ from the comparison unit 63. The drive circuit 70 generates a drive signal according to the phase shift amount Φ. This drive signal is a signal that switches the switching elements Q1 to Q8 on and off so as to realize the phase shift amount Φ. The drive circuit 70 controls the switching elements Q1 to Q8 by outputting a drive signal to the switching elements Q1 to Q8.

[0048] [Operation of this embodiment] When the first phase shift amount Φ1 is within the range of a dead zone D derived based on the input voltage Vin to the power conversion device 10 and the output voltage Vout of the power conversion device 10, the control unit 50 sets the phase shift amount Φ to a second phase shift amount Φ2 outside the range of the dead zone D. This prevents changes in the phase shift amount Φ from being reflected in the output. This will be explained in detail below.

[0049] As shown in FIG. 4, a comparative example is a power conversion device that sets the phase shift amount Φ without considering the dead zone D. That is, the power conversion device of the comparative example always sets the phase shift amount Φ to the first phase shift amount Φ1. In the comparative example, during the period when the phase shift amount Φ is set within the dead zone D, it is difficult to make the output current Iout follow the target current Itgt. Therefore, when an input voltage Vin containing ripple is input to the power conversion device, it is difficult to reduce this ripple, and the minimum value I of the output current Iout MIN and maximum value I MAX The difference between these two becomes large, and the output current Iout contains a large ripple.

[0050] As shown in FIG. 5, in the power conversion device 10 of this embodiment, when the first phase shift amount Φ1 is within the dead zone D, the second phase shift amount Φ2 becomes the phase shift amount Φ. Therefore, the phase shift amount Φ changes so as to avoid the dead zone D. Therefore, there is no period during which the output current Iout cannot follow the target current Itgt, and the output current Iout can easily follow the target current Itgt. As a result, even if the input voltage Vin contains ripples, the ripples can be easily reduced by making the output current Iout follow the target current Itgt. As can be seen from a comparison between FIG. 4 and FIG. 5, when an input voltage Vin containing ripples is input, the minimum value I of the output current Iout becomes 0.01. MIN and maximum value I MAX The difference between the values ​​is smaller in the power conversion device 10 of this embodiment than in the power conversion device of the comparative example. Therefore, it is clear that the ripple can be reduced.

[0051] [Effects of the embodiment] (1) The control unit 50 derives the first phase shift amount Φ1 from the current deviation ΔIout. When the first phase shift amount Φ1 is included within the range of the dead band D, the control unit 50 sets the second phase shift amount Φ2, which is outside the range of the dead band D, as the phase shift amount Φ. The second phase shift amount Φ2 is a value outside the range of the dead band D. By setting the phase shift amount Φ so as to avoid the dead band D, it is possible to make the output current Iout follow the target current Itgt. Therefore, it is possible to reduce the influence of the dead band D and reduce the ripple contained in the output current Iout.

[0052] By reducing the influence of the dead zone D using the phase shift method, there is no need to use the PWM method to reduce the influence of the dead zone D. With the PWM method, it is necessary to control the on-time of multiple switching elements Q1 to Q8, which makes the control more complicated. In contrast, with the phase shift method, it is only necessary to control the phase shift amount Φ while maintaining the on-time of the switching elements Q1 to Q8 constant, which makes the control simpler than with the PWM method.

[0053] (2) The control unit 50 derives the first phase shift amount Φ1 using the first feedback gain, and derives the second phase shift amount Φ2 using a second feedback gain that is greater than the first feedback gain. By setting the second feedback gain in consideration of the dead zone D, it is possible to derive the second phase shift amount Φ2 that is outside the range of the dead zone D.

[0054] (3) By reducing the effect of the dead zone D, the ripple contained in the output current Iout can be reduced. By reducing the ripple contained in the output current Iout, the current flowing through the secondary-side capacitor 16 can be reduced. This allows for improved power transmission efficiency.

[0055] (4) By reducing the ripple contained in the output current Iout, the ripple contained in the output voltage Vout can be reduced. Depending on the load 120, it may be preferable to reduce the ripple contained in the output voltage Vout. For example, if the load 120 is a secondary battery, the accuracy of determining the state of charge may decrease if the output voltage Vout contains ripple. In contrast, by reducing the ripple contained in the output voltage Vout, it is possible to prevent a decrease in the accuracy of determining the state of charge of the secondary battery.

[0056] (5) The second phase shift amount Φ2 is set as the phase shift amount Φ only when the first phase shift amount Φ1 is within the dead zone D. That is, when the first phase shift amount Φ1 is outside the dead zone D, the power conversion device 10 can be controlled by the existing phase shift control. Therefore, it is only necessary to newly develop local control when the first phase shift amount Φ1 is within the dead zone D, which can shorten the development period and evaluation period.

[0057] [Example of change] The embodiment can be modified as follows: The embodiment and the following modifications can be combined with each other to the extent that they are not technically inconsistent.

[0058] The control unit 50 may derive the second phase shift amount Φ2 by adding or subtracting a correction value to the first phase shift amount Φ1. That is, the second phase shift amount Φ2 may be a value obtained by shifting the first phase shift amount Φ1 by the correction value. The correction value may be, for example, within the range of the dead zone D, that is, the maximum value DZ. MAX and the minimum value DZ MIN The correction value is, for example, a positive value.

[0059] When the derived first phase shift amount Φ1 is within the dead zone D and the output current Iout is smaller than the target current Itgt, the feedback control unit 60 may set the value obtained by adding a correction value to the first phase shift amount Φ1 as the second phase shift amount Φ2. When the derived first phase shift amount Φ1 is within the dead zone D and the output current Iout is larger than the target current Itgt, the feedback control unit 60 may set the value obtained by subtracting the correction value from the first phase shift amount Φ1 as the second phase shift amount Φ2. By adding or subtracting the correction value to the first phase shift amount Φ1, it is sufficient that the second phase shift amount Φ2 falls outside the dead zone D, and an upper limit may be set for the shift amount of the first phase shift amount Φ1.

[0060] When the control unit 50 adds or subtracts a correction value to the first phase shift amount Φ1, it outputs the second phase shift amount Φ2 obtained by adding or subtracting the correction value as the phase shift amount Φ. When the first phase shift amount Φ1 is outside the range of the dead zone D, the control unit 50 outputs the first phase shift amount Φ1 as the phase shift amount Φ.

[0061] According to this, by calculating the correction value in advance, the second phase shift amount Φ2 can be easily calculated. ○When the derived first phase shift amount Φ1 is within the dead zone D and the output current Iout is smaller than the target current Itgt, the maximum value DZ MAX may be set as the second phase shift amount Φ2, and when the output current Iout is greater than the target current Itgt, the minimum value DZ MIN may be set as the second phase shift amount Φ2.

[0062] The primary side may be the output and the secondary side may be the input. In this case, power is transmitted from the secondary side full bridge circuit 40 to the primary side full bridge circuit 30. In this case, the voltage detected by the primary side voltage sensor 37 is the output voltage Vout. The voltage detected by the secondary side voltage sensor 47 is the input voltage Vin. By providing a current sensor connected to the primary side terminals 11 and 12, the output current Iout can be detected by this current sensor. Even in this case, the same control as in the embodiment can be performed.

[0063] The feedback control unit 60 may perform feedback control using a voltage deviation. In this case, the target value of the output is a target voltage, which is a target value of the output voltage Vout. The actual value of the output is the output voltage Vout. The deviation between the target value of the output and the actual value of the output is a voltage deviation, which is the difference between the output voltage Vout and the target voltage. The feedback control unit 60 controls the phase shift amount Φ in accordance with the voltage deviation, thereby causing the output voltage Vout to follow the target voltage.

[0064] The feedback control unit 60 may perform feedback control using the power deviation. In this case, the target value of the output is the target power, which is the target value of the output power. The actual value of the output is the output power. The deviation between the target value of the output and the actual value of the output is the power deviation, which is the difference between the output power and the target power. The feedback control unit 60 controls the phase shift amount Φ in accordance with the power deviation, so that the output power follows the target power. [Explanation of symbols]

[0065] L1, L2...reactor, Q1 to Q4...primary side switching elements, Q5 to Q8...secondary side switching elements, TS...transformer section, 10...power conversion device, 22...primary side winding, 23...secondary side winding, 30...primary side full bridge circuit, 40...secondary side full bridge circuit, 50...control section.

Claims

1. a transformer unit having a primary winding, a secondary winding, and a reactor connected to at least one of the primary winding and the secondary winding; a primary side full bridge circuit connected to the primary side winding and having a plurality of primary side switching elements; a secondary full bridge circuit connected to the secondary winding and having a plurality of secondary switching elements; a control unit that performs phase shift control to transmit power between the primary-side full bridge circuit and the secondary-side full bridge circuit by controlling a phase shift amount between the plurality of primary-side switching elements and the plurality of secondary-side switching elements, The control unit deriving a first phase shift amount from a deviation between a target value of the output and an actual value of the output; a power conversion device in which, when the first phase shift amount is included within a dead zone derived based on an input voltage to the power conversion device and an output voltage of the power conversion device, a second phase shift amount outside the dead zone is set as the phase shift amount.

2. The control unit deriving the first phase shift amount using a first feedback gain; The power conversion device according to claim 1 , wherein the second phase shift amount is derived from the deviation using a second feedback gain that is greater than the first feedback gain.

3. The power conversion device according to claim 1 , wherein the control unit derives the second phase shift amount by adding or subtracting a correction value to or from the first phase shift amount.

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