Power conversion device

Abstract

To provide a power conversion device capable of suppressing a surge voltage while improving responsiveness to a change in a load.SOLUTION: According to an embodiment of the present disclosure, there is provided a power conversion device including: a transformer including a first power terminal, a switching circuit connected to the first power terminal and including one or more switching elements, a first winding guided to the switching circuit, and a second winding; a capacitor provided in a path connecting the switching circuit and the first winding of the transformer; a current sensor capable of detecting a current flowing through one of the first winding and the second winding; a rectifier circuit connected to the second winding; a smoothing circuit connected to the rectifier circuit; a second power terminal guided to the smoothing circuit; and a control circuit capable of operating one or more switching elements at a predetermined switching period and capable of controlling a switching operation of the one or more switching elements based on a peak current of a current detected by the current sensor.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] Some power conversion devices have a transformer that converts DC power to DC power while isolating the input and output from each other. For example, Patent Document 1 discloses a power conversion device that performs phase shift control and controls the switching duty ratio of a switching element based on a peak current. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2013 / 114758 Summary of the Invention [Problem to be solved by the invention]

[0004] A power conversion device performs control in response to a change in load so that it can operate stably when the load changes. It is desirable for the power conversion device to respond quickly to such load changes. Furthermore, a surge voltage can occur in the power conversion device due to switching operations. Therefore, it is desirable for the power conversion device to suppress the surge voltage.

[0005] It is desirable to provide a power conversion device that can suppress surge voltages while improving responsiveness to changes in load. [Means for solving the problem]

[0006] The power conversion device of the present invention includes a first power terminal, a switching circuit, a transformer, a capacitor, a current sensor, a rectifier circuit, a smoothing circuit, a second power terminal, and a control circuit. The switching circuit is connected to the first power terminal and has one or more switching elements. The transformer has a first winding and a second winding led to the switching circuit. The capacitor is provided in a path connecting the switching circuit and the first winding of the transformer. The current sensor is capable of detecting a current flowing through one of the first winding and the second winding. The rectifier circuit is connected to the second winding and is capable of rectifying a signal supplied from the second winding. The smoothing circuit is connected to the rectifier circuit and is capable of smoothing the voltage rectified by the rectifier circuit. The second power terminal is led to the smoothing circuit. The control circuit is capable of operating one or more switching elements at a predetermined switching period, and is capable of controlling the switching operation of the one or more switching elements based on the peak current of the current detected by the current sensor. [Effects of the Invention]

[0007] According to the power conversion device of the present invention, it is possible to suppress surge voltage while improving responsiveness to changes in load. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a circuit diagram showing an example of the configuration of a power conversion device according to an embodiment of the present invention. [Figure 2] FIG. 2 is a block diagram showing a specific example of the control circuit shown in FIG. [Figure 3] FIG. 3 is a timing waveform diagram illustrating an example of the operation of the power conversion device shown in FIG. [Figure 4] FIG. 4 is a timing waveform diagram showing an example of an operation of peak current control in the power conversion device shown in FIG. [Figure 5] FIG. 5 is a timing waveform diagram illustrating another example of the operation of the power conversion device shown in FIG. [Figure 6] FIG. 6 is a circuit diagram illustrating an example of the configuration of a power conversion device according to a modified example. [Figure 7] FIG. 7 is a circuit diagram illustrating an example of the configuration of a power conversion device according to another modified example. [Figure 8] FIG. 8 is a circuit diagram illustrating an example of the configuration of a power conversion device according to another modified example. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[0010] [Configuration example] 1 shows an example of the configuration of a power conversion system 1 including a power conversion device according to an embodiment of the present invention. The power conversion system 1 includes a high-voltage battery BH, a power conversion device 10, and a low-voltage battery BL. The voltage of the high-voltage battery BH is, for example, 400 V, and the voltage of the low-voltage battery BL is, for example, 12 V. This power conversion system 1 is configured to convert power supplied from the high-voltage battery BH and supply the converted power to the low-voltage battery BL.

[0011] The power conversion device 10 is a resonant DC / DC converter configured to convert power by stepping down the voltage supplied from a high-voltage battery BH and supply the converted power to a low-voltage battery BL. The power conversion device 10 has terminals T11 and T12, a capacitor 11, a current sensor 20, a switching circuit 12, an inductor 13, a capacitor 14, a transformer 15, a rectifier circuit 16, a smoothing circuit 17, a voltage sensor 19, a filter circuit 30, a control circuit 40, and terminals T21 and T22. The high-voltage battery BH, the capacitor 11, the current sensor 20, the switching circuit 12, the inductor 13, and the capacitor 14 form a primary circuit of the power conversion system 1, and the rectifier circuit 16, the smoothing circuit 17, the voltage sensor 19, the filter circuit 30, and the low-voltage battery BL form a secondary circuit of the power conversion system 1.

[0012] Terminals T11 and T12 are configured to receive a voltage from a high-voltage battery BH. Terminal T11 is connected to the positive terminal of the high-voltage battery BH, and terminal T12 is connected to the negative terminal of the high-voltage battery BH. Furthermore, within the power conversion device 10, terminal T11 is connected to a voltage line L11A, and terminal T12 is connected to a reference voltage line L12.

[0013] One end of the capacitor 11 is connected to the voltage line L11A, and the other end is connected to the reference voltage line L12.

[0014] The current sensor 20 is configured to detect the current Iin flowing from the terminal T11 to the transformer 15 via the switching circuit 12. The current sensor 20 has a current transformer 21. The current transformer 21 has windings 21A and 21B. One end of the winding 21A is connected to the voltage line L11A, and the other end is connected to the voltage line L11B. The winding 21B is connected to a circuit subsequent to the current transformer 21 in the current sensor 20. The current sensor 20 generates a detection signal SIin corresponding to the current Iin based on the current flowing through the winding 21B, for example by performing filtering to remove noise.

[0015] The switching circuit 12 is configured to convert a DC voltage supplied from the high-voltage battery BH into an AC voltage by performing a switching operation. The switching circuit 12 is a full-bridge circuit and includes transistors SA, SB, SC, and SD. The transistors SA to SD are switching elements that perform switching operations based on control signals GA to GD, respectively. The transistors SA to SD are configured using, for example, N-type field effect transistors (FETs). Each of the transistors SA to SD has a body diode. For example, the anode of the body diode of the transistor SA is connected to the source of the body of the transistor SA, and the cathode is connected to the drain of the body of the transistor SA. The same is true for the transistors SB to SD. Note that, although an N-type field effect transistor is used in this example, any switching element may be used.

[0016] The transistor SA is provided in a path connecting the voltage line L11B and the node N1, and is configured to connect the node N1 to the voltage line L11B when it is turned on. The drain of the transistor SA is connected to the voltage line L11B, the gate is supplied with a control signal GA, and the source is connected to the node N1. The transistor SB is provided in a path connecting the node N1 and the reference voltage line L12, and is configured to connect the node N1 to the reference voltage line L12 when it is turned on. The drain of the transistor SB is connected to the node N1, the gate is supplied with a control signal GB, and the source is connected to the reference voltage line L12.

[0017] The transistor SC is provided in a path connecting the voltage line L11B and the node N2, and is configured to connect the node N2 to the voltage line L11B when it is turned on. The drain of the transistor SC is connected to the voltage line L11B, the gate is supplied with a control signal GC, and the source is connected to the node N2. The transistor SD is provided in a path connecting the node N2 and the reference voltage line L12, and is configured to connect the node N2 to the reference voltage line L12 when it is turned on. The drain of the transistor SD is connected to the node N2, the gate is supplied with a control signal GD, and the source is connected to the reference voltage line L12.

[0018] One end of inductor 13 is connected to node N2, and the other end is connected to winding 15A of transformer 15. One end of capacitor 14 is connected to node N1, and the other end is connected to winding 15A of transformer 15. Inductor 13 and capacitor 14 form a resonant circuit.

[0019] Transformer 15 is configured to insulate the primary circuit from the secondary circuit in terms of DC current and connect them in terms of AC current, convert the AC voltage supplied from the primary circuit at a transformation ratio of transformer 15, and supply the converted AC voltage to the secondary circuit. Transformer 15 has windings 15A and 15B. Winding 15A is a primary winding, and one end is connected to the other end of inductor 13 and the other end is connected to the other end of capacitor 14. Winding 15B is a secondary winding, and one end is connected to a node N3 (described later) in rectifier circuit 16 and the other end is connected to a node N4 (described later) in rectifier circuit 16.

[0020] Rectifier circuit 16 is configured to rectify the AC voltage output from winding 15B of transformer 15. Rectifier circuit 16 is a full-bridge circuit and includes diodes DA, DB, DC, and DD. The anode of diode DA is connected to node N3, and the cathode is connected to voltage line L21A. The anode of diode DB is connected to reference voltage line L22, and the cathode is connected to node N3. The anode of diode DC is connected to node N4, and the cathode is connected to voltage line L21A. The anode of diode DD is connected to reference voltage line L22, and the cathode is connected to node N4.

[0021] The smoothing circuit 17 is configured to smooth the voltage rectified by the rectifier circuit 16. The smoothing circuit 17 has a capacitor 18. One end of the capacitor 18 is connected to the voltage line L21A, and the other end is connected to the reference voltage line L22.

[0022] The voltage sensor 19 is configured to detect a voltage VL on the voltage line L21A. One end of the voltage sensor 19 is connected to the voltage line L21A, and the other end is connected to a reference voltage line L22. The voltage VL is the voltage on the voltage line L21A relative to the voltage on the reference voltage line L22. The voltage sensor 19 detects this voltage VL and generates a detection signal SVL corresponding to this voltage VL.

[0023] The filter circuit 30 is configured to remove high-frequency components contained in the output voltage of the power conversion device 10. The filter circuit 30 has an inductor 31 and a capacitor 32. One end of the inductor 31 is connected to the voltage line L21A, and the other end is connected to the voltage line L21B. One end of the capacitor 32 is connected to the voltage line L21B, and the other end is connected to the reference voltage line L22.

[0024] The control circuit 40 is configured to control the operation of the power conversion device 10 by controlling the switching operation of the switching circuit 12 based on the detection signal SIin supplied from the current sensor 20 and the detection signal SVL supplied from the voltage sensor 19. The control circuit 40 is configured using, for example, a microcontroller.

[0025] 2 shows an example of the configuration of the control circuit 40. The control circuit 40 includes an AD (Analog to Digital) conversion unit 41, a target voltage value setting unit 42, a subtraction unit 43, a PI (Proportional Integral) control unit 44, a slope compensation unit 45, a DA (Digital to Analog) conversion unit 46, a comparator 47, and a control signal generation unit 48.

[0026] The AD conversion unit 41 is configured to perform AD conversion at a predetermined sampling period based on the detection signal SVL supplied from the voltage sensor 19, thereby generating a signal S41 which is a digital signal.

[0027] The target voltage value setting unit 42 is configured to generate a signal S42 indicating the target value of the voltage VL.

[0028] The subtraction unit 43 is configured to generate a signal S43 by subtracting the signal S41 supplied from the AD conversion unit 41 from the signal S42 supplied from the target voltage value setting unit 42. In the control by the power conversion device 10, negative feedback control is performed so that the signal value of the signal S43, which is the subtraction result of the subtraction unit 43, becomes sufficiently small.

[0029] The PI control unit 44 is configured to perform PI control based on the signal S43 supplied from the subtraction unit 43, thereby generating a signal S44 indicating a target value of the peak current for the current Iin.

[0030] The slope compensator 45 is configured to generate a signal S45 whose signal value gradually decreases from the target value of the peak current indicated by the signal S44 based on the signal S44 supplied from the PI controller 44. The slope of the signal S45 as the signal value gradually decreases may be a fixed value or a variable value. When the slope is a variable value, the slope is set based on, for example, the input voltage of the power converter 10 or the output voltage of the power converter 10.

[0031] The DA conversion unit 46 is configured to perform DA conversion based on the signal S45 supplied from the slope compensation unit 45, thereby generating the slope signal SLP, which is an analog signal.

[0032] The comparator 47 is configured to compare the detection signal SIin and the slope signal SLP supplied from the current sensor 20. The detection signal SIin is supplied to a positive input terminal of the comparator 47, and the slope signal SLP is supplied to a negative input terminal of the comparator 47. The comparator 47 compares these signals and generates a signal S47 indicating the comparison result.

[0033] The control signal generating unit 48 is configured to generate the control signals GA to GD based on the signal S47 supplied from the comparator 47. The duty ratio of the four control signals GA to GD is approximately 50%, and the frequency is a fixed predetermined frequency. The control signal generating unit 48 performs phase shift control based on the signal S47 to generate the control signals GA to GD.

[0034] With this configuration, the control circuit 40 controls the switching operation of the switching circuit 12 based on the detection signal SVL so that the voltage value of the voltage VL becomes the same as the target value set by the target voltage value setting unit 42. Furthermore, the control circuit 40 can improve responsiveness to changes in the load based on, for example, the detection signal SIin. That is, for example, when the load current of the power conversion device 10 increases and the peak current becomes large, the control circuit 40 controls the switching operation of the switching circuit 12 so as to reduce the amount of power that the transformer 15 transmits from the primary side circuit to the secondary side circuit.

[0035] Terminals T21 and T22 (FIG. 1) are configured to supply the voltage generated by the power conversion device 10 to the low-voltage battery BL. Within the power conversion device 10, terminal T21 is connected to the voltage line L21B, and terminal T22 is connected to the reference voltage line L22. Furthermore, terminal T21 is connected to the positive terminal of the low-voltage battery BL, and terminal T22 is connected to the negative terminal of the low-voltage battery BL.

[0036] Here, terminals T11 and T12 correspond to a specific example of a "first power terminal" in an embodiment of the present disclosure. Switching circuit 12 corresponds to a specific example of a "switching circuit" in an embodiment of the present disclosure. Transistors SA to SD correspond to a specific example of "one or more switching elements" in an embodiment of the present disclosure. For example, transistor SA corresponds to a specific example of a "first switching element" in an embodiment of the present disclosure. For example, transistor SD corresponds to a specific example of a "second switching element" in an embodiment of the present disclosure. Transformer 15 corresponds to a specific example of a "transformer" in an embodiment of the present disclosure. Winding 15A corresponds to a specific example of a "first winding" in an embodiment of the present disclosure. Winding 15B corresponds to a specific example of a "second winding" in an embodiment of the present disclosure. Inductor 13 corresponds to a specific example of an "inductor" in an embodiment of the present disclosure. Capacitor 14 corresponds to a specific example of a "capacitor" in an embodiment of the present disclosure. Current sensor 20 corresponds to a specific example of a "current sensor" in an embodiment of the present disclosure. The rectifier circuit 16 corresponds to a specific example of a "rectifier circuit" in an embodiment of the present disclosure. The smoothing circuit 17 corresponds to a specific example of a "smoothing circuit" in an embodiment of the present disclosure. The terminals T21 and T22 correspond to a specific example of a "second power terminal" in an embodiment of the present disclosure. The control circuit 40 corresponds to a specific example of a "control circuit" in an embodiment of the present disclosure.

[0037] [Actions and Actions] Next, the operation and function of the power conversion device 10 of this embodiment will be described.

[0038] (Overview of overall operation) First, referring to FIG. 1, an overview of the overall operation of the power conversion device 10 will be described. The current sensor 20 generates a detection signal SIin by detecting a current Iin flowing from the terminal T11 to the transformer 15 via the switching circuit 12. The switching circuit 12 performs a switching operation to convert a DC voltage supplied from the high-voltage battery BH into an AC voltage. The transformer 15 insulates the primary side circuit from the secondary side circuit in DC and connects them in AC. It converts the AC voltage supplied from the primary side circuit using the transformation ratio of the transformer 15 and supplies the converted AC voltage to the secondary side circuit. The rectifier circuit 16 rectifies the AC voltage output from the winding 15B of the transformer 15. The smoothing circuit 17 smoothes the voltage rectified by the rectifier circuit 16. The filter circuit 30 removes high-frequency components from the output voltage of the power conversion device 10. The voltage sensor 19 detects a voltage VL on the voltage line L21A and generates a detection signal SVL corresponding to this voltage VL. The control circuit 40 controls the operation of the power conversion device 10 by controlling the switching operation of the switching circuit 12 based on the detection signal SIin supplied from the current sensor 20 and the detection signal SVL supplied from the voltage sensor 19.

[0039] (Detailed operation) FIG. 3 shows an example of operation of power conversion device 10, with (A) to (D) showing the waveforms of control signals GA to GD, respectively, (E) showing the waveform of the voltage (transformer voltage Vtr) applied to winding 15A of transformer 15, and (F) showing the waveform of the current (transformer current Itr) flowing through winding 15A of transformer 15. Control signal GA is the waveform of the gate voltage relative to the source voltage of transistor SA. The same is true for control signals GB to GD. Transformer voltage Vtr is the voltage at node N1 relative to node N2. Transformer current Itr is depicted as a positive current flowing through winding 15A from node N1 to node N2.

[0040] In this example, the frequency of the four control signals GA to GD is 200 kHz. The duty ratio of the control signals GA to GD is approximately 50%. While the control signal GA is at a high level, the control signal GB is maintained at a low level, and while the control signal GB is at a high level, the control signal GA is maintained at a low level. The control signals GA and GB are provided with a period during which both signals are at a low level (so-called dead time Td). Similarly, while the control signal GC is at a high level, the control signal GD is maintained at a low level, and while the control signal GD is at a high level, the control signal GC is maintained at a low level. The control signals GC and GD are provided with a period during which both signals are at a low level (dead time Td).

[0041] As shown in FIGS. 3A and 3D, the control circuit 40 sets the control signal GD to a high level during the period from timing t11 to t13. This causes the transistor SD to be turned on during this period from timing t11 to t13. The control circuit 40 also sets the control signal GA to a high level during the period from timing t12 to t15. This causes the transistor SA to be turned on during this period from timing t12 to t15. As a result, as shown in FIG. 3E, during the period from timing t12 to t13 when both the control signals GA and GD are at a high level, the transformer voltage Vtr becomes a positive voltage (400 V in this example). Specifically, the transformer voltage Vtr changes from 0 V to a positive voltage at timing t12, and then changes from the positive voltage to 0 V at timing t13. During this period from timing t12 to t13, the transformer 15 transmits power from the primary circuit to the secondary circuit.

[0042] Similarly, as shown in FIGS. 3B and 3C, the control circuit 40 sets the control signal GC to a high level during the period from timing t14 to t17. As a result, the transistor SC is turned on during this period from timing t14 to t17. The control circuit 40 also sets the control signal GB to a high level during the period from timing t16 to t19. As a result, the transistor SB is turned on during this period from timing t16 to t19. As a result, as shown in FIG. 3E, during the period from timing t16 to t17 when the control signals GB and GC are both at a high level, the transformer voltage Vtr becomes a negative voltage (−400 V in this example). Specifically, the transformer voltage Vtr changes from 0 V to a negative voltage at timing t16, and then changes from the negative voltage to 0 V at timing t17. During this period from timing t16 to t17, the transformer 15 transmits power from the primary side circuit to the secondary side circuit.

[0043] As shown in FIG. 3(E), the transformer voltage Vtr changes in the order 0V, a positive voltage, 0V, a negative voltage, and again 0V. In response, the transformer current Itr flows through the winding 15A of the transformer 15 as shown in FIG. 3(F). Specifically, the transformer current Itr changes from a negative current to a positive current during the period from timing t10 ​​to t13, and reaches a positive peak at timing t13. The transformer current Itr also changes from a positive current to a negative current during the period from timing t13 to t17, and reaches a negative peak at timing t17. Since the power conversion device 10 includes a resonant circuit formed by the inductor 13 and the capacitor 14, the transformer current Itr has a slightly rounded waveform.

[0044] The current Iin varies in accordance with the transformer current Itr. The current sensor 20 detects the current Iin and generates a detection signal SIin. The control circuit 40 performs peak current control based on the detection signal SIin.

[0045] FIG. 4 shows an example of the operation of peak current control, where (A) shows the waveform of the transformer current Itr, and (B) shows the waveform of the slope signal SLP and the waveform of the detection signal SIin.

[0046] As shown in FIG. 4A, the transformer current Itr changes from negative to positive during the period from timing t20 to t21, reaching a positive peak at timing t21. The transformer current Itr also changes from positive to negative during the period from timing t21 to t22, reaching a negative peak at timing t22. In response to this transformer current Itr, the detection signal SIin drops once during the period from timing t20 to t21 and then gradually rises, reaching a peak at timing t21. The detection signal SIin also drops once during the period from timing t21 to t22 and then gradually rises, reaching a peak at timing t22. The peak of the detection signal SIin at timing t21 corresponds to the positive peak of the transformer current Itr at this timing t21, and the peak of the detection signal SIin at timing t22 corresponds to the negative peak of the transformer current Itr at this timing t22.

[0047] That is, when transistors SA and SD are on, current flows in the primary circuit in the following order: voltage line L11A, current sensor 20, voltage line L11B, transistor SA, capacitor 14, winding 15A of transformer 15, inductor 13, transistor SD, and reference voltage line L12. As a result, the transformer current Itr changes from negative to positive. When transistors SB and SC are on, current flows in the primary circuit in the following order: voltage line L11A, current sensor 20, voltage line L11B, transistor SC, inductor 13, winding 15A of transformer 15, capacitor 14, transistor SB, and reference voltage line L12. As a result, the transformer current Itr changes from positive to negative. Thus, regardless of the polarity of the transformer current Itr, current Iin flows in the current sensor 20 from voltage line L11A to voltage line L11B. Therefore, the waveform of the detection signal SIin becomes a waveform as shown in FIG. 4(B), which corresponds to the waveform of the transformer current Itr (FIG. 4(A)).

[0048] The slope compensation unit 45 of the control circuit 40 generates a signal S45 whose signal value gradually decreases from a target value of the peak current for the current Iin. The DA conversion unit 46 then generates a slope signal SLP by converting a digital signal to an analog signal based on the signal S45 supplied from the slope compensation unit 45. As shown in FIG. 4(B), the slope signal SLP has a waveform whose signal level gradually decreases from the target value PEAK of the peak current for the current Iin. This slope signal SLP is a signal synchronized with the control signals GA and GB.

[0049] The comparator 47 compares the detection signal SIin with the slope signal SLP.

[0050] For example, during a period including timing t21, the slope signal SLP gradually decreases (FIG. 4B). During the period from timing t20 to t21, the detection signal SIin decreases and then gradually increases. At timing t21, the detection signal SIin reaches the same signal level as the slope signal SLP. The comparator 47 outputs the comparison result, and the control signal generator 48 transitions the control signals GC and GD based on the comparison result of the comparator 47. Specifically, as shown in FIGS. 3C and 3D, the control signal generator 48 transitions the control signal GD from a high level to a low level at timing t13, and transitions the control signal GC from a low level to a high level at timing t14. With this transition of the control signal GD, the transistor SD is turned off, and therefore, at timing t13, the transformer current Itr begins to change toward a negative current (FIG. 3F). In response to this, the detection signal SIin begins to decrease, as shown in FIG. 4.

[0051] For example, during a period including timing t22, the slope signal SLP gradually decreases (FIG. 4B). During the period from timing t21 to t22, the detection signal SIin decreases once and then gradually increases. At timing t22, the detection signal SIin reaches the same signal level as the slope signal SLP. The comparator 47 outputs the comparison result, and the control signal generator 48 transitions the control signals GC and GD based on the comparison result of the comparator 47. Specifically, as shown in FIGS. 3C and 3D, the control signal generator 48 transitions the control signal GC from a high level to a low level at timing t17, and transitions the control signal GD from a low level to a high level at timing t18. With this transition of the control signal GC, the transistor SC enters an off state, and the transformer current Itr begins to change toward a positive current at timing t17 (FIG. 3F). In response to this, the detection signal SIin begins to decrease, as shown in FIG. 4.

[0052] In this way, in the power conversion device 10, phase shift control is performed based on the peak current of the current Iin, and the change timings of the control signals GC and GD are set. As shown in Fig. 3, the phase of the control signal GD leads the phase of the control signal GA by a time Tsft.

[0053] 5 shows another example of the operation of the power conversion device 10. In this example, the peak current of the current Iin is larger than that in the case of FIG.

[0054] As shown in FIGS. 5A and 5D, the control circuit 40 sets the control signal GD to a high level during the period from timing t31 to t33. As a result, the transistor SD is turned on during this period from timing t31 to t33. The control circuit 40 also sets the control signal GA to a high level during the period from timing t32 to t35. As a result, the transistor SA is turned on during this period from timing t32 to t35. As a result, as shown in FIG. 5E, the transformer voltage Vtr becomes a positive voltage (400 V in this example) during the period from timing t32 to t33 when the control signals GA and GD are both at a high level.

[0055] Similarly, as shown in FIGS. 5B and 5C, the control circuit 40 sets the control signal GC to a high level during the period from timing t34 to t37. As a result, the transistor SC is turned on during this period from timing t34 to t37. The control circuit 40 also sets the control signal GB to a high level during the period from timing t36 to t39. As a result, the transistor SB is turned on during this period from timing t36 to t39. As a result, as shown in FIG. 5E, the transformer voltage Vtr becomes a negative voltage (−400 V in this example) during the period from timing t36 to t37 when the control signals GB and GC are both at a high level.

[0056] In response to this transformer voltage Vtr, a transformer current Itr flows through winding 15A of transformer 15, as shown in Fig. 5(F). Specifically, transformer current Itr changes from negative to positive during the period from timing t30 to t33, reaching a positive peak at timing t33. Then, transformer current Itr changes from positive to negative during the period from timing t33 ​​to t37, reaching a negative peak at timing t37.

[0057] The current Iin varies in accordance with the transformer current Itr. The current sensor 20 detects the current Iin and generates a detection signal SIin. The control circuit 40 performs peak current control based on the detection signal SIin.

[0058] In this example, the peak current of the current Iin is larger than in the case of FIG. 3. In this case, the detection signal SIin reaches the same signal level as the slope signal SLP at an earlier timing than the timing shown in FIG. 4. Therefore, the control signals GC and GD transition at an earlier timing than the timing shown in FIG. 3, as shown in FIG. 5. In this case, the phase of the control signal GD advances further than in the case of FIG. 3. In this way, the power conversion device 10 performs phase shift control.

[0059] Thus, the power conversion device 10 includes a first power terminal (terminals T11, T12), a switching circuit 12 connected to the first power terminal and having a plurality of switching elements (transistors SA to SD), a transformer 15 having a first winding (winding 15A) and a second winding (winding 15B) led to the switching circuit 12, a capacitor 14 provided in a path connecting the switching circuit 12 and the first winding (winding 15A) of the transformer 15, a current sensor 20 capable of detecting a current flowing through the first winding (winding 15A), and a second winding (winding 15B) connected to the second winding (winding 15B). The power supply is provided with a rectifier circuit 16 capable of rectifying a signal supplied from the second winding (winding 15B), a smoothing circuit 17 connected to the rectifier circuit 16 and capable of smoothing the voltage rectified by the rectifier circuit, second power terminals (terminals T21, T22) connected to the smoothing circuit 17, and a control circuit 40 capable of operating a plurality of switching elements (transistors SA to SD) at a predetermined switching period and capable of controlling the switching operation of the plurality of switching elements (transistors SA to SD) based on the peak current detected by the current sensor 20. In this example, an inductor 13 is provided in a path connecting the switching circuit 12 and the first winding of the transformer 15.

[0060] In this way, the power conversion device 10 is provided with a resonant circuit including the inductor 13 and the capacitor 14, which allows signals to change more smoothly. As a result, the power conversion device 10 can suppress surge voltages in the primary and secondary circuits. That is, for example, diodes DA to DD in the secondary circuits often have low forward voltages in order to reduce losses. However, such diodes have low withstand voltages and may be damaged by surge voltages. The power conversion device 10 is provided with a resonant circuit, which allows surge voltages to be suppressed.

[0061] Furthermore, in the power conversion device 10, the switching operations of the multiple switching elements (transistors SA to SD) are controlled based on the peak current of the current detected by the current sensor 20. This allows the phase of the control signals GC and GD to be shifted based on the magnitude of the peak current, for example, as shown in FIGS. 3 and 5. In this case, the responsiveness to changes in the load can be improved. That is, for example, when the switching operations are controlled based on the average voltage or average current, the response to changes in the load is slow. On the other hand, in the power conversion device 10, the switching operations are controlled based on the peak current, and therefore the average value is not used, thereby improving the responsiveness to changes in the load.

[0062] In particular, the power conversion device 10 includes a resonant circuit including the inductor 13 and the capacitor 14, and controls the switching operation of multiple switching elements (transistors SA to SD) based on the peak current detected by the current sensor 20. This allows for improved responsiveness to load changes while suppressing surge voltages. Generally, when a power conversion device includes a resonant circuit, the transformer current Itr has a smooth waveform, similar to a sine wave. In such a power conversion device, it is difficult to control the switching operation based on the peak current. On the other hand, the power conversion device 10 sets the circuit parameters of the resonant circuit to cause weak resonance. This prevents the waveform from becoming smooth, as in the case of the transformer current Itr shown in FIG. 3. Therefore, the power conversion device 10, even with a resonant circuit, can control the switching operation based on the peak current. As a result, the power conversion device 10 can suppress surge voltages while improving responsiveness to load changes.

[0063] Furthermore, in the power conversion device 10, the multiple switching elements (transistors SA to SD) include a first switching element (transistor SA) and a second switching element (transistor SD). The control circuit 40 is able to control the switching operation by controlling the time difference between the switching timing of the first switching element (transistor SA) and the switching timing of the second switching element (transistor SD). In the power conversion device 10, the switching operation of the switching circuit 12 can be controlled using such phase shift control.

[0064] [effect] As described above, this embodiment includes a first power terminal, a switching circuit connected to the first power terminal and having multiple switching elements, a transformer having a first winding and a second winding connected to the switching circuit, a capacitor provided in a path connecting the switching circuit and the first winding of the transformer, a current sensor capable of detecting the current flowing through the first winding, a rectifier circuit connected to the second winding and capable of rectifying a signal supplied from the second winding, a smoothing circuit connected to the rectifier circuit and capable of smoothing the voltage rectified by the rectifier circuit, a second power terminal connected to the smoothing circuit, and a control circuit capable of operating the multiple switching elements at a predetermined switching cycle and controlling the switching operation of the multiple switching elements based on the peak current detected by the current sensor. Also, an inductor is provided in the path connecting the switching circuit and the first winding of the transformer. This allows for improved responsiveness to load changes while suppressing surge voltages.

[0065] [Variation 1] In the above embodiment, the power conversion device 10 includes the inductor 13 as a component, but this is not limiting. Alternatively, for example, a loosely coupled transformer may be used as the transformer 15 without including the inductor 13 as a component, and the leakage inductance of the transformer 15 may be used as the inductance of the inductor 13. In this case, it is desirable to use the transformer 15 having a coupling coefficient of, for example, 0.92 or more and 0.97 or less. Alternatively, both the transformer 15, which is a loosely coupled transformer, and the inductor 13 as a component may be provided.

[0066] [Variation 2] In the above embodiment, the switching operation of the switching circuit 12 is controlled using phase shift control, but this is not limiting. Instead, the switching operation of the switching circuit 12 may be controlled using, for example, PWM (Pulse Width Modulation) control. In this case, the control circuit 40 controls the switching operation by controlling the switching duty ratio of the transistors SA to SD.

[0067] [Variation 3] In the above embodiment, the current sensor 20 is provided in the stage preceding the switching circuit 12, but this is not limitative and the current sensor may be provided at any position as long as it can detect the current flowing through the transformer 15. Below, this modified example will be described with some examples.

[0068] 6 shows an example of the configuration of a power conversion system 1A according to this modification. The power conversion system 1A includes a power conversion device 10A. The power conversion device 10A includes a current sensor 50 and a control circuit 40A.

[0069] The current sensor 50 is configured to detect a current I1 flowing from a node N2 of the switching circuit 12 to a transformer 15. The current sensor 50 includes a current transformer 51. The current transformer 51 includes windings 51A and 51B. One end of the winding 51A is connected to a node N2 of the switching circuit 12, and the other end is connected to one end of the inductor 13. The winding 51B is connected to a circuit in the current sensor 50 subsequent to the current transformer 51. The current sensor 50 generates a detection signal SI1 corresponding to the current I1 by, for example, performing full-wave rectification and filtering to remove noise based on the current flowing through the winding 51B. By performing full-wave rectification, the current sensor 50 can generate a detection signal SI1 having a waveform similar to that of the detection signal SIin shown in FIG. 4.

[0070] Similar to the control circuit 40 (FIG. 1) according to the above embodiment, the control circuit 40A is configured to control the operation of the power conversion device 10A by controlling the switching operation of the switching circuit 12 based on the detection signal SI1 supplied from the current sensor 50 and the detection signal SVL supplied from the voltage sensor 19.

[0071] 7 shows an example of the configuration of a power conversion system 1B according to this modification. The power conversion system 1B includes a power conversion device 10B. The power conversion device 10B includes a current sensor 60 and a control circuit 40B.

[0072] Current sensor 60 is configured to detect current I2 flowing from transformer 15 via rectifier circuit 16 toward smoothing circuit 17. Current sensor 60 has a current transformer 61. Current transformer 61 has windings 61A and 61B. One end of winding 61A is connected to voltage line L21A, and the other end is connected to voltage line L21A1. Winding 61B is connected to a circuit subsequent to current transformer 61 in current sensor 60. Current sensor 60 generates a detection signal SI2 corresponding to current I2 based on the current flowing through winding 61B, for example by performing filtering to remove noise.

[0073] One end of capacitor 18 is connected to voltage line L21A1. One end of voltage sensor 19 is connected to voltage line L21A1. One end of inductor 31 is connected to voltage line L21A1.

[0074] Similar to the control circuit 40 (FIG. 1) according to the above embodiment, the control circuit 40B is configured to control the operation of the power conversion device 10B by controlling the switching operation of the switching circuit 12 based on the detection signal SI2 supplied from the current sensor 60 and the detection signal SVL supplied from the voltage sensor 19.

[0075] [Variation 4] Although the above embodiment uses the circuit configuration shown in Fig. 1, the present invention is not limited to this and other circuit configurations may be used. A power conversion system 1C according to this modification will be described in detail below.

[0076] 8 shows an example of the configuration of a power conversion system 1C. The power conversion system 1C includes a power conversion device 10C. The power conversion device 10C includes terminals T11 and T12, a capacitor 11, a switching circuit 72, a current sensor 80, an inductor 13, a capacitor 14, a transformer 75, a rectifier circuit 76, a smoothing circuit 17, a voltage sensor 19, a filter circuit 30, a control circuit 40C, and terminals T21 and T22.

[0077] The switching circuit 72 is a half-bridge circuit and includes capacitors C1 and C2 and transistors S1 and S2. One end of the capacitor C1 is connected to the voltage line L11, and the other end is connected to a node N5. One end of the capacitor C2 is connected to the node N5, and the other end is connected to a reference voltage line L12. The drain of the transistor S1 is connected to the voltage line L11, the gate is supplied with a control signal G1, and the source is connected to a node N6. The drain of the transistor S2 is connected to the node N6, the gate is supplied with a control signal G2, and the source is connected to the reference voltage line L12.

[0078] The current sensor 80 is configured to detect a current I3 flowing from a node N6 of the switching circuit 72 to a transformer 75. The current sensor 80 includes a current transformer 81. The current transformer 81 includes windings 81A and 81B. One end of the winding 81A is connected to a node N6 of the switching circuit 72, and the other end is connected to one end of the inductor 13. The winding 81B is connected to a circuit in the current sensor 80 subsequent to the current transformer 81. The current sensor 80 generates a detection signal SI3 corresponding to the current I3 based on the current flowing through the winding 81B by, for example, performing full-wave rectification and filtering to remove noise. By performing full-wave rectification, the current sensor 80 can generate a detection signal SI3 having a waveform similar to that of the detection signal SIin shown in FIG. 4.

[0079] Transformer 75 has windings 75A, 75B, and 75C. Winding 75A is a primary winding, and one end is connected to the other end of inductor 13 and the other end is connected to the other end of capacitor 14. Windings 75B and 75C are secondary windings. One end of winding 75B is connected to the cathode of diode D2 (described later) in rectifier circuit 76, and the other end is connected to voltage line L21A. One end of winding 75C is connected to voltage line L21A, and the other end is connected to the cathode of diode D1 (described later) in rectifier circuit 76.

[0080] The rectifier circuit 76 has diodes D1 and D2. The anode of the diode D1 is connected to the reference voltage line L22, and the cathode is connected to the other end of the winding 75C of the transformer 75. The anode of the diode D2 is connected to the reference voltage line L22, and the cathode is connected to one end of the winding 75B of the transformer 75.

[0081] Similar to the control circuit 40 (FIG. 1) according to the above embodiment, the control circuit 40C is configured to control the operation of the power conversion device 10C by controlling the switching operation of the switching circuit 72 based on the detection signal SI3 supplied from the current sensor 80 and the detection signal SVL supplied from the voltage sensor 19.

[0082] [Other variations] Two or more of these variations may also be combined.

[0083] Although the present invention has been described above by way of embodiments and modifications, the present invention is not limited to these embodiments and can be modified in various ways.

[0084] For example, in the above embodiment, the switching operation of the switching circuit 12 is controlled based on the detection signal SIin supplied from the current sensor 20 and the detection signal SVL supplied from the voltage sensor 19. That is, the power conversion device 10 controls the switching operation of the switching circuit 12 based on the peak current and the output voltage of the power conversion device 10. However, the present technology is not limited to this. For example, the power conversion device 10 may control the switching operation of the switching circuit 12 based on the peak current and one or more of the input voltage of the power conversion device 10, the input current of the power conversion device 10, the output voltage of the power conversion device 10, and the output current of the power conversion device 10. When the input voltage of the power conversion device 10 is used, the circuit upstream of the power conversion device 10 is, for example, a constant current circuit. For example, when the power conversion device 10 controls the switching operation based on the peak current, the output voltage of the power conversion device 10, and the output current of the power conversion device 10, the output power of the power conversion device 10 can be controlled.

[0085] The effects described in this specification are merely examples, and the effects of the present disclosure are not limited to the effects described in this specification. Therefore, other effects may be obtained with respect to the present disclosure.

[0086] Furthermore, the present disclosure may take the following aspects.

[0087] (1) a first power terminal; a switching circuit connected to the first power terminal and having one or more switching elements; a transformer having a first winding and a second winding connected to the switching circuit; a capacitor provided in a path connecting the switching circuit and the first winding of the transformer; a current sensor capable of detecting a current flowing through one of the first winding and the second winding; a rectifier circuit connected to the second winding and capable of rectifying a signal supplied from the second winding; a smoothing circuit connected to the rectifier circuit and capable of smoothing the voltage rectified by the rectifier circuit; a second power terminal connected to the smoothing circuit; a control circuit capable of operating the one or more switching elements at a predetermined switching period and capable of controlling the switching operation of the one or more switching elements based on a peak current detected by the current sensor; A power conversion device comprising: (2) The inverter further includes an inductor provided in a path connecting the switching circuit and the first winding of the transformer. The power conversion device according to (1) above. (3) The transformer is a loosely coupled transformer The power conversion device according to (1) above. (4) The coupling coefficient of the transformer is 0.92 or more and 0.97 or less. The power conversion device according to (3) above. (5) the one or more switching elements include a first switching element and a second switching element; The control circuit is capable of controlling the switching operation by controlling a time difference between a switching timing of the first switching element and a switching timing of the second switching element. The power conversion device according to any one of (1) to (4) above. (6) The control circuit is capable of controlling the switching operation by controlling a switching duty ratio of the one or more switching elements. The power conversion device according to any one of (1) to (4) above. (7) The control circuit is capable of controlling the switching operation based on the peak current and at least one of a voltage at the smoothing circuit, a current at the second power terminal, a voltage at the first power terminal, and a current at the first power terminal. The power conversion device according to any one of (1) to (6) above. [Explanation of symbols]

[0088] 1, 1A, 1B, 1C... Power conversion system, 10, 10A, 10B, 10C... Power conversion device, 11... Capacitor, 12... Switching circuit, 13... Inductor, 14... Capacitor, 15... Transformer, 15A, 15B... Winding, 16... Rectifier circuit, 17... Smoothing circuit, 18... Capacitor, 19... Voltage sensor, 20... Current sensor, 21... Current transformer, 21A, 21B... Winding, 30... Filter circuit, 31... Inductor, 32... Capacitor, 40... Control circuit, 40A, 40B, 40C... Control circuit, 41... AD conversion unit, 42... Target voltage value setting unit, 43... Subtraction unit, 44... PI control unit, 45... Slope compensation unit, 46... DA conversion unit, 47... Comparator, 48... Control signal generation unit, 50... Current sensor, 51... Current transformer, 51A, 51B... Winding, 60... Current sensor, 61...current transformer, 61A, 61B...winding, 72...switching circuit, 75...transformer, 75A, 75B, 75C...winding, 76...rectifier circuit, 80...current sensor, 81...current transformer, 81A, 81B...winding, BH...high voltage battery, BL...low voltage battery, C1, C2...capacitor, D1, D2...diode, DA, DB, DC, DD...diode, G1, G2...control signal signal, GA, GB, GC, GD... control signal, L11, L11A, L11B... voltage line, L12... reference voltage line, L21A, L21A1, L21B... voltage line, L22... reference voltage line, S1, S2... transistor, SA, SB, SC, SD... transistor, SI1, SI2, SI3, SIin... detection signal, SLP... slope signal, SVL... detection signal, T11, T12, T21, T22... terminal.

Claims

1. a first power terminal; a switching circuit connected to the first power terminal and having one or more switching elements; a transformer having a first winding and a second winding connected to the switching circuit; a capacitor provided in a path connecting the switching circuit and the first winding of the transformer; a current sensor capable of detecting a current flowing through one of the first winding and the second winding; a rectifier circuit connected to the second winding and capable of rectifying a signal supplied from the second winding; a smoothing circuit connected to the rectifier circuit and capable of smoothing the voltage rectified by the rectifier circuit; a second power terminal connected to the smoothing circuit; a control circuit capable of operating the one or more switching elements at a predetermined switching period and capable of controlling the switching operation of the one or more switching elements based on a peak current detected by the current sensor; A power conversion device comprising:

2. The inverter further includes an inductor provided in a path connecting the switching circuit and the first winding of the transformer. The power conversion device according to claim 1 .

3. The transformer is a loosely coupled transformer The power conversion device according to claim 1 .

4. The coupling coefficient of the transformer is 0.92 or more and 0.97 or less. The power conversion device according to claim 3 .

5. the one or more switching elements include a first switching element and a second switching element; The control circuit is capable of controlling the switching operation by controlling a time difference between a switching timing of the first switching element and a switching timing of the second switching element. The power conversion device according to claim 1 .

6. The control circuit is capable of controlling the switching operation by controlling a switching duty ratio of the one or more switching elements. The power conversion device according to claim 1 .

7. The control circuit is capable of controlling the switching operation based on the peak current and at least one of a voltage at the smoothing circuit, a current at the second power terminal, a voltage at the first power terminal, and a current at the first power terminal. The power conversion device according to claim 1 .

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