Charging system

Abstract

To provide a charging system capable of suppressing power loss.SOLUTION: A charging system according to the present disclosure includes: an ACDC converter; a DCDC converter; and a control circuit. The ACDC converter is connected between an input node and an intermediate node. The ACDC converter can be connected to a power supply via the input node. The DCDC converter is connected between the intermediate node and an output node. The DCDC converter can be connected to a battery via the output node. The control circuit controls a voltage of the intermediate node so that a sum of a loss of the ACDC converter and a loss of the DCDC converter becomes small in accordance with a first parameter, a second parameter, and a third parameter. The first parameter is a parameter related to an input power of the ACDC converter. The second parameter is a parameter related to an output power of the DCDC converter. The third parameter is a parameter related to an environmental temperature.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a charging system. [Background technology]

[0002] A charging system connected between an AC power source and a battery converts AC power received from the AC power source into DC power, and charges the battery with the DC power (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 6024209 Summary of the Invention [Problem to be solved by the invention]

[0004] In a charging system, power losses may occur when AC power is converted to DC power and / or when DC power is converted to other DC power.

[0005] The present disclosure provides a charging system that can reduce power loss. [Means for solving the problem]

[0006] A charging system according to the present disclosure includes an ACDC converter, a DCDC converter, and a control circuit. The ACDC converter is connected between an input node and an intermediate node. The ACDC converter is connectable to a power supply via the input node. The DCDC converter is connected between the intermediate node and an output node. The DCDC converter is connectable to a battery via the output node. The control circuit controls the voltage of the intermediate node in accordance with a first parameter, a second parameter, and a third parameter so as to reduce the sum of losses in the ACDC converter and the DCDC converter. The first parameter is a parameter related to the input power of the ACDC converter. The second parameter is a parameter related to the output power of the DCDC converter. The third parameter is a parameter related to the ambient temperature. The control circuit has correspondence information in which the sum of a first parameter, a second parameter, and a third parameter is associated with the voltage of the intermediate node for multiple voltage values ​​of the intermediate node. The control circuit acquires the first parameter, the second parameter, and the third parameter, and when there are multiple sums corresponding to the acquired first parameter, the acquired second parameter, and the acquired third parameter in the correspondence information, determines as a target value one of the multiple sums that minimizes the sum of the loss in the AC-DC converter and the loss in the DC-DC converter. The control circuit controls the switching elements in the AC-DC converter so that the voltage of the intermediate node becomes the target value. [Effects of the Invention]

[0007] According to the charging system according to the present disclosure, power loss can be reduced. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a circuit diagram showing a configuration of a charging system according to an embodiment; [Figure 2] FIG. 4 is a diagram showing the temperature dependence of the on-resistance of a switching element in the embodiment. [Figure 3] FIG. 2 is a diagram showing the functional configuration of a control circuit according to the embodiment. [Figure 4] FIG. 4 is a diagram showing a data structure of correspondence information according to the embodiment. [Figure 5] FIG. 4 is a diagram showing the temperature dependence of voltage-current characteristics of a rectifying element according to an embodiment. [Figure 6] FIG. 4 is a diagram showing the temperature dependence of core loss of an isolation transformer according to an embodiment. [Figure 7] FIG. 4 is a circuit diagram showing the configuration of a charging system according to a first modified example of the embodiment. [Figure 8] FIG. 10 is a circuit diagram showing the configuration of a charging system according to a second modified example of the embodiment. [Figure 9]FIG. 10 is a diagram showing the functional configuration of a control circuit in a second modified example of the embodiment. [Figure 10] FIG. 10 is a diagram showing the operation of a control circuit in a second modified example of the embodiment. [Figure 11] FIG. 10 is a diagram showing the functional configuration of a control circuit in a third modified example of the embodiment. [Figure 12] FIG. 10 is a diagram showing the operation of a control circuit in a third modified example of the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, an embodiment of a charging system according to the present disclosure will be described with reference to the drawings.

[0010] (Embodiment) A charging system according to an embodiment is connected between an AC power source and a battery, converts AC power from the AC power source into DC power, and then converts it into another DC power to charge the battery, and is designed to reduce power loss during these conversions. For example, a charging system 1 can be configured as shown in Fig. 1. Fig. 1 is a circuit diagram showing the configuration of the charging system 1.

[0011] The charging system 1 is connected between an AC power source PS and a battery BT. The charging system 1 includes an AC-DC converter 10, a DC-DC converter 20, and a control circuit 30. The DC-DC converter 20 may be an LLC converter. Under the control of the control circuit 30, the charging system 1 converts an AC voltage Vin from the AC power source PS into a DC voltage Vsub while boosting it using the AC-DC converter 10, and then converts the converted DC voltage Vsub into a charging DC voltage Vout while boosting and bucking it using the DC-DC converter 20, and charges the battery BT. For example, the charging system 1 may be an on-board charger installed in an electric vehicle or hybrid vehicle, the AC power source PS may be a power grid in a home or a charging station, and the battery BT may be an on-board battery. The level of the AC voltage Vin may vary depending on the destination of the charging system 1. The level of the DC voltage Vout may vary depending on the charging state of the battery BT.

[0012] In the charging system 1, an input node Nin1 is connected to one end of an AC power supply PS, and an input node Nin2 is connected to the other end of the AC power supply PS. In the charging system 1, an output node Nout1 is connected to the positive electrode of a battery BT, and an output node Nout2 is connected to the negative electrode of the battery BT.

[0013] The power loss of the charging system 1 can change depending on the temperature. For this reason, the control circuit 30 performs control based on the input power of the AC-CDC converter 10, the output power of the DC-CDC converter 20, and the ambient temperature so that the sum of the losses of the AC-CDC converter 10 and the DC-CDC converter 20 is smaller than the sum of the current losses. This allows the charging system 1 to suppress power loss and efficiently convert AC power to DC power and convert DC power to other DC power.

[0014] In addition to the AC-DC converter 10, the DC-DC converter 20, and the control circuit 30, the charging system 1 includes an AC filter 2, a capacitance element C1, a DC filter 3, voltage sensors VS1 to VS3, current sensors CS1 and CS2, and a temperature sensor TS1.

[0015] The AC filter 2 is connected between the input nodes Nin1, Nin2 and the AC-CDC converter 10. One end of the AC filter 2 is connected between the input node Nin1 and the input node 10a of the AC-CDC converter 10, and the other end is connected between the input node Nin2 and the input node 10b of the AC-CDC converter 10. When noise components flow out from the AC-CDC converter 10 side, the AC filter 2 performs filtering on the noise components to attenuate them. This allows the AC filter 2 to prevent noise components from flowing out from the AC-CDC converter 10 side to the AC power supply PS.

[0016] The AC-CDC converter 10 is connected between input nodes Nin1, Nin2 and intermediate nodes Nmid1, Nmid2. The AC-CDC converter 10 can be connected to an AC power supply PS via the input nodes Nin1, Nin2. The AC-CDC converter 10 is connected between the AC filter 2 and intermediate nodes Nmid1, Nmid2. The AC-CDC converter 10 uses a PFC (Power Factor Correction) circuit to convert AC power into DC power while correcting the power factor of the AC power.

[0017] The AC-DC converter 10 includes, for example, a PFC circuit, including multiple rectifier elements D1-D6, multiple inductive elements L1 and L2, and multiple switching elements SW1 and SW2. The rectifier elements D1-D4 are bridge-connected to form a bridge circuit. In this configuration, the bridge circuit full-wave rectifies the AC voltage, and then the switching operations of the switching elements SW1 and SW2 repeatedly store and release energy in the inductive elements L1 and L2. Accordingly, the current flow to the capacitive element C1 via the rectifier elements D5 and D6 is repeatedly stopped and injected. This allows the AC-DC converter 10 to generate a DC output voltage Vsub while approximating the phase of the AC current to the phase of the AC voltage, thereby improving the power factor.

[0018] Rectifying element D1 rectifies in the direction from input node 10a to output node 10c. Rectifying element D1 is, for example, a diode, and has an anode connected to input node 10a and a cathode connected to output node 10c via inductive element L1 and rectifying element D5.

[0019] Rectifying element D2 rectifies in the direction from input node 10b to output node 10c. Rectifying element D2 is, for example, a diode, and has an anode connected to input node 10b and a cathode connected to output node 10c via inductive element L1 and rectifying element D5.

[0020] Rectifying element D3 rectifies in the direction from input node 10a to output node 10d. Rectifying element D3 is, for example, a diode, with an anode connected to input node 10a and a cathode connected to output node 10d.

[0021] Rectifying element D4 rectifies in the direction from input node 10b to output node 10d. Rectifying element D4 is, for example, a diode, with an anode connected to input node 10b and a cathode connected to output node 10d.

[0022] A series connection of inductive element L1 and rectifying element D5 and a series connection of inductive element L2 and rectifying element D6 are connected in parallel between rectifying elements D1, D2 and output node 10c. A switching element SW1 is connected between a node 10e between inductive element L1 and rectifying element D5 and output node 10d. A switching element SW2 is connected between a node 10f between inductive element L2 and rectifying element D6 and output node 10d.

[0023] The inductive element L1 is connected between the rectifying elements D1 and D2 and the node 10e. The inductive element L1 is, for example, a coil, and has one end connected to the rectifying elements D1 and D2 and the other end connected to the node 10e. The inductive element L1 can contribute to improving the power factor of the AC / DC converter 10 by storing and releasing electromagnetic energy.

[0024] Rectifying element D5 rectifies in the direction from node 10e to output node 10c. Rectifying element D5 is, for example, a diode, with an anode connected to node 10e and a cathode connected to output node 10c.

[0025] The inductive element L2 is connected between the rectifying elements D1 and D2 and the node 10e. The inductive element L2 is, for example, a coil, and has one end connected to the rectifying elements D1 and D2 and the other end connected to the node 10f. The inductive element L2 can contribute to improving the power factor of the AC / DC converter 10 by storing and releasing electromagnetic energy.

[0026] Rectifying element D6 rectifies in the direction from node 10f to output node 10c. Rectifying element D6 is, for example, a diode, with an anode connected to node 10f and a cathode connected to output node 10c.

[0027] The switching element SW1 is connected between the node 10e and the rectifying elements D3 and D4. The switching element SW1 electrically connects or disconnects the node 10e and the rectifying elements D3 and D4 in response to a control signal from the control circuit 30. The switching element SW1 is, for example, an N-channel MOSFET transistor, and has a source connected to the rectifying elements D3 and D4, a drain connected to the node 10e, and a gate connected to the control circuit 30.

[0028] The switching element SW1 is turned on when it receives an active level control signal at its gate from the control circuit 30, thereby electrically connecting the node 10e to the rectifying elements D3 and D4. The switching element SW1 is turned off when it receives a non-active level control signal at its gate from the control circuit 30, thereby electrically disconnecting the node 10e from the rectifying elements D3 and D4.

[0029] The switching element SW2 is connected between the node 10f and the rectifying elements D3 and D4. The switching element SW2 electrically connects or disconnects the node 10f and the rectifying elements D3 and D4 in response to a control signal from the control circuit 30. The switching element SW2 is, for example, an N-channel MOSFET transistor, and has a source connected to the rectifying elements D3 and D4, a drain connected to the node 10f, and a gate connected to the control circuit 30.

[0030] The switching element SW2 is turned on when it receives an active-level control signal at its gate from the control circuit 30, thereby electrically connecting the node 10f with the rectifying elements D3 and D4. The switching element SW2 is turned off when it receives a non-active-level control signal at its gate from the control circuit 30, thereby electrically disconnecting the node 10f from the rectifying elements D3 and D4.

[0031] The capacitive element C1 is connected between the AC-DC converter 10 and the DC-DC converter 20. The capacitive element C1 is a smoothing capacitor such as an aluminum electrolytic capacitor, a film capacitor, or a ceramic capacitor, and has one end connected to the intermediate node Nmid1 and the other end connected to the intermediate node Nmid2. The capacitive element C1 can contribute to improving the power factor of the AC-DC converter 10 by charging and discharging an electric charge, and can generate a DC voltage Vsub.

[0032] The DC-DC converter 20 is, for example, an LLC converter. The DC-DC converter 20 is connected between intermediate nodes Nmid1, Nmid2 and output nodes Nout1, Nout2. The DC-DC converter 20 can be connected to a battery BT via the output nodes Nout1, Nout2. The DC-DC converter 20 is connected between the intermediate nodes Nmid1, Nmid2 and a DC filter 3. The DC-DC converter 20 uses an isolation transformer TR to convert DC power into DC power for charging while insulating and separating the input side (primary side) and the output side (secondary side).

[0033] The DC-DC converter 20 includes, for example, a primary circuit 21, an insulating transformer TR, and a secondary circuit 22. The primary circuit 21 includes a plurality of switching elements SW11 to SW14 and a capacitance element C11. The insulating transformer TR includes a primary winding L11, a secondary winding L12, and a core CR1. The secondary circuit 22 includes a plurality of rectifying elements D11 to D14.

[0034] The switching element SW11 is connected between the input node 20a and the node 20e. The switching element SW11 electrically connects or disconnects the input node 20a and the node 20e in response to a control signal from the control circuit 30. The switching element SW11 is, for example, an N-channel MOSFET transistor, and has a source connected to the node 20e, a drain connected to the input node 20a, and a gate connected to the control circuit 30.

[0035] The switching element SW11 is turned on when it receives an active level control signal at its gate from the control circuit 30, thereby electrically connecting the input node 20a and the node 20e. The switching element SW11 is turned off when it receives a non-active level control signal at its gate from the control circuit 30, thereby electrically disconnecting the input node 20a and the node 20e.

[0036] The switching element SW12 is connected between the input node 20a and a node 20f. The switching element SW12 electrically connects or disconnects the input node 20a and the node 20f in response to a control signal from the control circuit 30. The switching element SW12 is, for example, an N-channel MOSFET transistor, and has a source connected to the node 20f, a drain connected to the input node 20a, and a gate connected to the control circuit 30.

[0037] The switching element SW12 is turned on when it receives an active level control signal at its gate from the control circuit 30, thereby electrically connecting the input node 20a and the node 20f. The switching element SW12 is turned off when it receives a non-active level control signal at its gate from the control circuit 30, thereby electrically disconnecting the input node 20a and the node 20f.

[0038] The switching element SW13 is connected between the node 20e and the input node 20b. The switching element SW13 electrically connects or disconnects the node 20e and the input node 20b in response to a control signal from the control circuit 30. The switching element SW13 is, for example, an N-channel MOSFET transistor, and has a source connected to the input node 20b, a drain connected to the node 20e, and a gate connected to the control circuit 30.

[0039] The switching element SW13 is turned on when it receives an active level control signal at its gate from the control circuit 30, thereby electrically connecting the node 20e and the input node 20b. The switching element SW13 is turned off when it receives a non-active level control signal at its gate from the control circuit 30, thereby electrically disconnecting the node 20e and the input node 20b.

[0040] The switching element SW14 is connected between the node 20f and the input node 20b. The switching element SW14 electrically connects or disconnects the node 20f and the input node 20b in response to a control signal from the control circuit 30. The switching element SW14 is, for example, an N-channel MOSFET transistor, and has a source connected to the input node 20b, a drain connected to the node 20f, and a gate connected to the control circuit 30.

[0041] Switching element SW14 is turned on when it receives an active-level control signal at its gate from control circuit 30, thereby electrically connecting node 20f and input node 20b. Switching element SW14 is turned off when it receives a non-active-level control signal at its gate from control circuit 30, thereby electrically disconnecting node 20f and input node 20b.

[0042] Note that the transistor electrodes are described as drain, gate, and source on the assumption that each of the switching elements SW1, SW2, SW11 to SW14 is an N-channel MOSFET, but if each of the switching elements SW1, SW2, SW11 to SW14 is an IGBT (insulated gate bipolar transistor), the drain can be read as collector and the source as emitter.

[0043] The capacitance element C11 is connected between the node 20e and the primary winding L11. One end of the capacitance element C11 is connected to the node 20e, and the other end is connected to one end of the primary winding L11. The capacitance element C11 performs a resonant operation together with the primary winding L11, thereby reducing switching loss caused by the switching elements SW11 to SW14.

[0044] In the isolation transformer TR, the primary winding L11 is electrically isolated from the secondary winding L12 and is magnetically coupled to the secondary winding L12 via the core CR1. The isolation transformer TR may be configured as a flyback type. As shown by the black circles in Figure 1, the primary winding L11 and the secondary winding L12 are wound in opposite directions relative to the path of the magnetic field lines in the core CR1. The isolation transformer TR may be configured without the core CR1, as long as the primary winding L11 and the secondary winding L12 are magnetically coupled to each other.

[0045] The primary winding L11 has one end connected to a node 20e via a capacitive element C11 and the other end connected to a node 20f. The secondary winding L12 has one end connected to a node 20g and the other end connected to a node 20h.

[0046] The rectifying element D11 rectifies in the direction from the node 20g toward the output node 20c. The rectifying element D11 is, for example, a diode, and has an anode connected to the node 20g and a cathode connected to the output node 20c.

[0047] The rectifying element D12 rectifies in the direction from the node 20f toward the output node 20c. The rectifying element D12 is, for example, a diode, and has an anode connected to the node 20f and a cathode connected to the output node 20c.

[0048] Rectifying element D13 rectifies in the direction from output node 20d to node 20g. Rectifying element D13 is, for example, a diode, with an anode connected to output node 10d and a cathode connected to node 20g.

[0049] Rectifying element D14 rectifies in the direction from output node 20d to node 20h. Rectifying element D14 is, for example, a diode, with an anode connected to output node 20d and a cathode connected to node 20h.

[0050] The DC filter 3 is connected between the DC-DC converter 20 and the output nodes Nout1 and Nout2. One end of the DC filter 3 is connected between the DC-DC converter 20 and the output node Nout1, and the other end is connected between the DC-DC converter 20 and the output node Nout2. The DC filter 32 filters the DC power supplied from the DC filter 3 and supplies it to the battery BT. This allows the DC filter 3 to reduce noise contained in the DC power before supplying it to the battery BT.

[0051] The voltage sensor VS1 detects the input voltage Vin of the charging system 1. The voltage sensor VS1 detects the voltage between the input node 10a and the input node 10b as the input voltage Vin. The voltage sensor VS1 supplies the detected input voltage Vin to the control circuit 30.

[0052] The voltage sensor VS2 detects the output voltage Vout of the charging system 1. The voltage sensor VS2 detects the voltage between the output node 20c and the output node 20d as the output voltage Vout. The voltage sensor VS2 supplies the detected output voltage Vout to the control circuit 30.

[0053] The voltage sensor VS3 detects an intermediate voltage Vsub of the charging system 1. The voltage sensor VS3 detects the voltage between the intermediate nodes Nmid1 and Nmid2 as the intermediate voltage Vsub. The voltage sensor VS3 supplies the detected intermediate voltage Vsub to the control circuit 30.

[0054] The current sensor CS1 detects the input current Iin of the charging system 1. The current sensor CS1 detects the current flowing between the input node Nin1 and the input node 10a as the input current Iin. The current sensor CS1 supplies the detected input current Iin to the control circuit 30.

[0055] The current sensor CS2 detects the output current Iout of the charging system 1. The current sensor CS2 detects the current flowing between the output node 20c and the output node Nout1 as the output current Iout. The current sensor CS2 supplies the detected output current Iout to the control circuit 30.

[0056] Here, the characteristics of each of the switching elements SW11 to SW14 related to power loss have temperature dependency. For example, the on-resistance of each of the switching elements SW11 to SW14 can change depending on the ambient temperature, as shown in Fig. 2. Fig. 2 is a diagram showing the temperature dependency of the on-resistance of each of the switching elements SW11 to SW14. Fig. 2 illustrates the tendency that the higher the ambient temperature, the higher the on-resistance becomes as the temperature dependency of the on-resistance of each of the switching elements SW11 to SW14.

[0057] Therefore, the temperature sensor TS1 detects the environmental temperature of the charging system 1. The temperature sensor TS1 may detect the temperature near the switching elements SW11-SW14 as the environmental temperature of the charging system 1. For example, the temperature sensor TS1 may be mounted on a substrate on which the switching elements SW11-SW14 are mounted, or may be attached to the surface of a package in the case where the switching elements SW11-SW14 are sealed in a package.

[0058] The temperature sensor TS1 may be one or more. For example, one temperature sensor TS1 may be mounted on a substrate on which the switching elements SW11-SW14 are mounted, or may be attached to the surface of the package of one of the switching elements SW11-SW14. Multiple temperature sensors TS1 may be distributed at multiple locations on the substrate on which the switching elements SW11-SW14 are mounted, or may be attached to the surface of each of the multiple switching elements SW11-SW14.

[0059] The control circuit 30 acquires a first parameter related to the input power of the AC-CDC converter 10, a second parameter related to the output power of the DC-DC converter 20, and a third parameter related to the ambient temperature. The charging system 1 controls the voltage Vsub of the intermediate nodes Nmid1 and Nmid2 based on the first, second, and third parameters so that the sum of the losses of the AC-CDC converter 10 and the DC-CDC converter 20 is smaller than the sum of the current losses. That is, the control circuit 30 determines a target value for the voltage Vsub of the intermediate nodes Nmid1 and Nmid2. The charging system 1 controls the switching elements in the AC-CDC converter 10 so that the voltage Vsub of the intermediate nodes Nmid1 and Nmid2 becomes the determined target value. This allows the charging system 1 to suppress power loss and efficiently convert AC power to DC power and convert DC power to other DC power.

[0060] For example, the control circuit 30 may be configured as shown in Fig. 3. Fig. 3 is a diagram showing the functional configuration of the control circuit 30. Each functional configuration shown in Fig. 3 may be implemented in software, in hardware, or in part in software and the rest in hardware.

[0061] The control circuit 30 includes a first parameter acquisition unit 31 , a second parameter acquisition unit 32 , a third parameter acquisition unit 33 , a target voltage determination unit 35 , a first control unit 36 ​​, and a second control unit 37 .

[0062] The first parameter acquisition unit 31 acquires a first parameter. The first parameter is a parameter related to the input power of the AC / DC converter 10. The first parameter may be the input voltage Vin of the AC / DC converter 10, the input current Iin of the AC / DC converter 10, or the input power of the AC / DC converter 10 (=effective value of Vin×effective value of Iin).

[0063] The second parameter acquisition unit 32 acquires a second parameter. The second parameter is a parameter related to the output power of the DC-DC converter 20. The second parameter may be the output voltage Vout of the DC-DC converter 20, the output current Iout of the DC-DC converter 20, or the output power of the DC-DC converter 20 (=effective value of Vout×effective value of Iout).

[0064] The third parameter acquisition unit 33 acquires a third parameter. The third parameter is a parameter related to the environmental temperature. The third parameter may be the temperature in the vicinity of the switching elements SW11 to SW14.

[0065] The storage unit 34 stores correspondence information 341. The correspondence information 341 associates the first parameter, the second parameter, the third parameter, the sum of losses, and the voltage Vsub of the intermediate node for a plurality of voltage values ​​of the intermediate node. The correspondence information 341 may be implemented in the form of a table or a formula.

[0066] For example, the storage unit 34 may have correspondence information 341 as shown in FIG. 4. FIG. 4 is a diagram showing the data structure of the correspondence information 341. FIG. 4 illustrates an example in which a first parameter is the input voltage Vin of the AC-DC converter 10, a second parameter is the output voltage Vout of the DC-DC converter 20, and a third parameter is the temperature T near the switching elements SW11 to SW14. FIG. 4 illustrates the correspondence information 341 as information having a hierarchical structure. That is, information for the same temperature T is arranged in the row direction, and information for multiple different temperatures T is arranged in the column direction. Information for the voltage value of the same voltage Vsub is arranged in the column direction, and information for multiple different voltage values ​​is arranged in the row direction. In a rectangular area specified by a combination of temperature T and voltage Vsub, information for power losses corresponding to the same input voltage Vin is arranged in the row direction, and information for multiple different input voltages Vin is arranged in the column direction. Information for power losses corresponding to the same output voltage Vout is arranged in the column direction, and information for multiple different output voltages Vout is arranged in the row direction. The information on power loss is the sum of the power loss of the AC-DC converter 10 and the power loss of the DC-DC converter 20, which is experimentally determined and recorded in advance for each condition.

[0067] The data structure of the correspondence information 341 is not limited to the structure shown in FIG. 4, and may be any other data structure as long as the first parameter, the second parameter, the third parameter, the sum of the loss, and the voltage Vsub of the intermediate node are associated with each other for multiple voltage values ​​of the intermediate node.

[0068] The target voltage determination unit 35 receives the first parameter from the first parameter acquisition unit 31, the second parameter from the second parameter acquisition unit 32, and the third parameter from the third parameter acquisition unit 33. The target voltage determination unit 35 determines the target value of the voltage Vsub of the intermediate nodes Nmid1, Nmid2 according to the first parameter, the second parameter, and the third parameter so that the sum of the loss in the AC-DC converter 10 and the loss in the DC-DC converter 20 becomes smaller than (for example, minimized) the sum of the current losses.

[0069] The target voltage determination unit 35 accesses the storage unit 34 and refers to the correspondence information 341 to determine the sum of the current losses of the AC-DC converter 10 and the DC-DC converter 20 (the current sum of losses). The target voltage determination unit 35 may determine the target values ​​of the voltages Vsub of the intermediate nodes Nmid1 and Nmid2 so that the sum of the losses of the AC-DC converter 10 and the DC-DC converter 20 is smaller (for example, minimum) than the current sum of losses. When there are multiple sums of losses corresponding to the acquired first parameter, the acquired second parameter, and the acquired third parameter in the correspondence information 341, the target voltage determination unit 35 identifies a sum of losses that is smaller (for example, minimum) than the current sum of losses from among the multiple sums of losses. The target voltage determination unit 35 determines the voltage value of the intermediate node corresponding to the identified sum of losses as the target value of the voltage Vsub.

[0070] For example, when the input voltage Vin=200V, the output voltage Vout=300V, and the temperature T=80°C, the loss sums PL1, PL2, and PL3 corresponding to the voltages Vsub=400V, 410V, and 420V are identified by referring to the correspondence information 341 shown in FIG. 4. At this time, the target voltage determination unit 35 compares the magnitudes of the loss sums PL1, PL2, and PL3. The target voltage determination unit 35 determines whether the comparison result is PL1 <PL2<PL3 If the current voltage Vsub=410V, the current sum of losses is PL2. In this case, PL1 is smaller than PL2, so the target value of voltage Vsub is determined to be 400V, which corresponds to the sum of losses PL1. Alternatively, if the current voltage Vsub=420V, the current sum of losses is PL3. In this case, PL1 and PL2 are smaller than PL3, so the target value of voltage Vsub may be determined to be 400V, which corresponds to the sum of losses PL1, or 410V, which corresponds to the sum of losses PL2.

[0071] Returning to FIG. 3, the target voltage determination unit 35 supplies the target value of the voltage Vsub to the first control unit 36 ​​and the second control unit 37, respectively.

[0072] The first control unit 36 ​​receives a target value (e.g., 400 V) of the voltage Vsub from the target voltage determination unit 35. The first control unit 36 ​​controls the switching elements SW1 and SW2 of the AC / DC converter 10 according to the target value of the voltage Vsub. The first control unit 36 ​​causes the switching elements SW1 and SW2 to perform switching operations using gate signals adjusted by modulating the frequency and / or pulse width according to the target value of the voltage Vsub. This allows the control circuit 30 to control the AC / DC converter 10 to receive the AC voltage Vin and output a DC voltage Vsub at a level according to the target value.

[0073] The second control unit 37 receives a target value (e.g., 400 V) of the voltage Vsub from the target voltage determination unit 35. The second control unit 37 controls the switching elements SW11 to SW14 of the DC-DC converter 20 according to the target value of the voltage Vsub. The second control unit 37 causes the switching elements SW11 to SW14 to perform switching operations using gate signals adjusted by modulating the frequency and / or pulse width according to the target value of the voltage Vsub. This allows the control circuit 30 to control the DC-DC converter 20 so that it receives the DC voltage Vsub at a level according to the target value and outputs the DC voltage Vout for charging.

[0074] As described above, in the charging system 1, the control circuit 30 controls the voltage Vsub of the intermediate node in accordance with the first parameter related to the input power Vin, the second parameter related to the output power Vout, and the third parameter related to the ambient temperature T so that the sum of the losses in the AC-DC converter 10 and the DC-DC converter 20 is smaller (e.g., minimized) than the sum of the current losses. That is, the control circuit 30 determines a target value for the voltage Vsub of the intermediate node. The control circuit 30 controls the switching elements SW1 and SW2 in the AC-DC converter 10 so that the voltage Vsub of the intermediate node becomes the target value. This allows the charging system 1 to suppress power loss and efficiently convert AC power to DC power and DC power to other DC power. This allows for fewer heat-dissipating components in the charging system 1, thereby reducing the cost and size of the charging system 1.

[0075] Considering that the more parameters there are, the higher the accuracy becomes, the control circuit 30 may acquire two or more of the input power, input voltage, and input current of the AC-DC converter 10 as the first parameters. The control circuit 30 may acquire two or more of the output power, output voltage, and output current of the DC-DC converter 20 as the second parameters. Accordingly, the correspondence information 341 may be further hierarchical. Alternatively, if an increase in the number of parameters results in a larger table and insufficient capacity for the control circuit 30, an approximation formula using these data may be provided to the control circuit 30, and the voltage Vbus may be derived by calculation using observed values.

[0076] Furthermore, the temperature sensor TS1 may detect the temperature near the switching elements SW1 and SW2 as the environmental temperature of the charging system 1 instead of or in addition to the temperature near the switching elements SW11 to SW14.

[0077] Alternatively, the temperature near other elements whose characteristics related to power loss have temperature dependency may be further taken into consideration as the environmental temperature of the charging system 1i.

[0078] For example, the voltage-current characteristics of rectifier elements D5 and D6 can change depending on the ambient temperature, as shown in FIG. 5. FIG. 5 is a diagram showing the temperature dependence of the voltage-current characteristics of rectifier elements D1 to D4. FIG. 5 illustrates the tendency for the forward voltage-forward current characteristics of rectifier elements D1 to D4 to shift to the upper left as the temperature increases from T1 to T2 to T3 to T4. In other words, as the temperature increases from T1 to T2 to T3 to T4, the "on-resistance" = "forward voltage" / "forward current" of rectifier elements D1 to D4 decreases, and the forward voltage also decreases.

[0079] The loss in the core CR1 of the isolation transformer TR varies with ambient temperature, as shown in Figure 6. Figure 6 shows the temperature dependence of core loss in the isolation transformer TR. The isolation transformer TR converts electrical energy into magnetic energy in the primary winding L11, transmits the magnetic energy to the secondary winding L12 via the core CR1, and then converts the magnetic energy back into electrical energy in the secondary winding L12. Energy loss occurs as the magnetic energy is transmitted through the core CR1. Figure 6 shows the temperature dependence for several different core materials. The core material indicated by the large-pitch dotted line shows a tendency for core loss to decrease with increasing temperature. The core materials indicated by the small-pitch dotted line, dashed line, and double-dashed line show a tendency for core loss to initially decrease but then increase with increasing temperature. The temperatures at which core loss is minimized differ between the various core materials. Note that the loss of each core material can be reduced by reducing the voltage applied to the primary winding L11.

[0080] As a first modified example of the embodiment, in consideration of the temperature dependence shown in Fig. 2, Fig. 5, and Fig. 6, the charging system 1i may further include temperature sensors TS2 and TS3 as shown in Fig. 7. Fig. 7 is a circuit diagram showing the configuration of the charging system 1i according to the first modified example of the embodiment. The temperature sensor TS2 may detect the temperature near the rectifying elements D5 and D6 as the environmental temperature of the charging system 1i. The temperature sensor TS3 may detect the temperature near the core CR1 of the isolation transformer TR as the environmental temperature of the charging system 1i.

[0081] In this case, the third parameter acquiring unit 33 in the control circuit 30i may obtain the environmental temperature by weighting the temperatures detected by the temperature sensors TS1, TS2, and TS3. For example, the influence of the temperature near the switching elements SW11 to SW14 on power loss may be W1, the influence of the temperature near the rectifying elements D1 to D4 on power loss may be W2, and the influence of the temperature near the core CR1 of the isolation transformer TR on power loss may be W3. If the temperatures detected by the temperature sensors TS1, TS2, and TS3 are TS1, TS2, and TS3, respectively, the third parameter acquiring unit 33 can obtain the environmental temperature T as the third parameter using the following equation 1. T = (W1 × TS1 + W2 × TS2 + W3 × TS3) / (W1 + W2 + W3) Formula 1

[0082] In this way, the control circuit 30i can control the voltage Vsub of the intermediate nodes Nmid1 and Nmid2 so that the sum of the losses in the AC-DC converter 10 and the DC-DC converter 20 becomes smaller (for example, minimized) than the sum of the current losses, taking into account the temperatures near multiple elements. This makes it possible to more accurately control the voltage Vsub so that the sum of the losses in the AC-DC converter 10 and the DC-DC converter 20 becomes smaller (for example, minimized) than the sum of the current losses.

[0083] Temperature sensor TS1 may detect the temperature near switching elements SW1 and SW2 as the environmental temperature of charging system 1i, instead of or in addition to the temperature near switching elements SW11 to SW14. Temperature sensor TS2 may detect the temperature near rectifying elements D1 to D4 and D11 to D14 as the environmental temperature of charging system 1i, instead of or in addition to the temperature near rectifying elements D5 and D6.

[0084] Alternatively, as a second modified example of the embodiment, the charging system 1j may monitor the first parameter and the second parameter to calculate the system efficiency and dynamically control the voltage Vbus to maximize the efficiency. That is, the voltage Vbus may be controlled by adjusting the operation (mainly duty ratio control) of the AC / DC converter 10 depending on the circuit state.

[0085] For example, the operating conditions (frequency or duty ratio) of the DC / DC converter 20 downstream of the AC / DC converter 10 are uniquely determined by the voltage of the Vbus and the output storage battery BT, and the output current (load condition) to be charged. For this reason, like a hill-climbing method, the efficiency immediately before and the efficiency at the next timing may be compared, and based on the magnitude relationship, it may be determined whether or not the maximum efficiency is being approached, and the operating conditions (for example, frequency or duty ratio) of the switching elements SW1 and SW2 may be adjusted to increase the efficiency.

[0086] As shown in FIG. 8, the charging system 1j does not include the temperature sensor TS1 in the charging system 1 (see FIG. 1). FIG. 8 is a circuit diagram showing the configuration of a charging system 1j according to a second modification of the embodiment. The control circuit 30j calculates power efficiency based on a first parameter and a second parameter, and controls the operation of the AC-DC converter 10 so as to increase the calculated power efficiency. The control circuit 30j compares the power efficiency calculated at the first timing with the power efficiency calculated at the second timing. The control circuit 30j determines the direction in which the power efficiency increases based on the comparison result. The control circuit 30j controls the voltage Vbus in the determined direction. That is, the control circuit 30j controls the operating conditions (e.g., frequency or pulse width) of the switching elements SW1 and SW2 in the AC-DC converter 10 so as to increase the calculated power efficiency.

[0087] The control circuit 30j can be configured as shown in Fig. 9. Fig. 9 is a diagram showing the functional configuration of the control circuit 30j in a second modified example of the embodiment. The control circuit 30j has a system efficiency calculation unit 41j, a storage unit 42j, and a determination unit 43j instead of the storage unit 34 and the target voltage determination unit 35 (see Fig. 3), and the third parameter acquisition unit 33 is omitted.

[0088] The first parameter acquiring unit 31 acquires the input current Iin from the current sensor CS1 and acquires the input voltage Vin from the voltage sensor VS1. The first parameter acquiring unit 31 can obtain the input power PWin as the first parameter using the following Equation 2. PWin = Iin × Vin Formula 2

[0089] The second parameter acquiring unit 32 acquires the output current Iout from the current sensor CS2 and acquires the output voltage Vout from the voltage sensor VS2. The second parameter acquiring unit 32 can obtain the output power PWout as the second parameter using the following Equation 3. PWout = Iout × Vout Equation 3

[0090] When the first parameter and the second parameter are calculated using Equation 2 and Equation 3, respectively, the system efficiency calculation unit 41j can calculate the power efficiency R of the charging system 1j using Equation 4 below. R=(PWout) / (PWin)...Formula 4

[0091] The storage unit 42j stores the calculated power efficiency R in association with the timing. The determination unit 43j compares the power efficiency calculated at the first timing with the power efficiency calculated at the second timing. Based on the comparison result, the determination unit 43j determines the direction in which the power efficiency increases for each of the operating conditions (e.g., frequency or pulse width) of the switching elements SW1 and SW2 and the operating conditions (e.g., frequency or pulse width) of the switching elements SW11 to SW14. The determination unit 43j supplies the determination results to the first control unit 36 ​​and the second control unit 37. In response to this, the first control unit 36 ​​adjusts the operating conditions to increase the power efficiency and causes the switching elements SW1 and SW2 to perform switching operations. The second control unit 37 adjusts the operating conditions to increase the power efficiency and causes the switching elements SW11 to SW14 to perform switching operations.

[0092] For example, the control circuit 30j may search for the maximum point of the power efficiency R by a hill-climbing method, as shown in Fig. 10. Fig. 10 is a diagram showing the operation of the control circuit 30j in the second modified example of the embodiment.

[0093] At timing t1, the system efficiency calculation unit 41j calculates the power efficiency R1 while the switching elements SW1, SW2, SW11 to SW14 are operating under the operating condition C1, and the combination P1(C1, R1) is stored in the storage unit 42j. In order to search for the maximum point of the power efficiency R, the first control unit 36 ​​and the second control unit 37 increase the operating condition (for example, the frequency Fsw) of the switching elements SW1, SW2, SW11 to SW14 from C1 to C2.

[0094] At timing t2, the system efficiency calculation unit 41j calculates the power efficiency R2 while the switching element is operating under the operating condition C2, and the combination P2 (C2, R2) is stored in the storage unit 42j. The determination unit 43j compares the power efficiencies R1 and R2. R1 <R2 If so, the determining unit 43j determines that the change in the increasing direction of the operating conditions from C1 to C2 is a change in the direction that increases power efficiency. In response to this, the first control unit 36 ​​and the second control unit 37 increase the operating conditions of the switching elements SW1, SW2, SW11 to SW14 from C2 to C3.

[0095] At timing t3, the system efficiency calculation unit 41j calculates the power efficiency R3 while the switching element is operating under the operating condition C3, and the combination P3 (C3, R3) is stored in the storage unit 42j. The determination unit 43j compares the power efficiencies R2 and R3. If the comparison result is R2 <R3 If so, the determining unit 43j determines that the change in the increasing direction of the operating conditions from C2 to C3 is a change in the direction that increases power efficiency. In response to this, the first control unit 36 ​​and the second control unit 37 increase the operating conditions of the switching elements SW1, SW2, SW11 to SW14 from C3 to C4.

[0096] At timing t4, the system efficiency calculation unit 41j calculates the power efficiency R4 while the switching element is operating under the operating condition C4, and the combination P4 (C4, R4) is stored in the storage unit 42j. The determination unit 43j compares the power efficiencies R3 and R4. If the comparison result is R3>R4 If so, the determination unit 43j determines that the change in the operating condition from C3 to C4 in the increasing direction is a change in the direction of decreasing power efficiency. In response to this, the first control unit 36 ​​and the second control unit 37 change the operating conditions of the switching elements SW1, SW2, SW11 to SW14 back from C4 to C3. In response to this, the first control unit 36 ​​and the second control unit 37 change the operating conditions of the switching elements SW1, SW2, SW11 to SW14 back from C4 to C3. As a result, the control circuit 30j determines that the operating condition C3 is an operating condition near the maximum power efficiency, and ends the search.

[0097] In this way, the control circuit 30j sequentially obtains the power efficiency according to the first parameter and the second parameter, and controls the voltage Vbus while searching for the power efficiency to be increased (for example, maximized). This makes it possible to respond to dynamic changes and improve the power efficiency in real time.

[0098] The control circuit 30j may also calculate and search for power efficiency sequentially (for example, at predetermined intervals) even during circuit operation.

[0099] Furthermore, the range in which the power efficiency is increased (for example, maximized) is not limited to the entire charging system 1j. For example, the control circuit 30j may perform a search using a hill-climbing method or the like to increase (for example, maximize) the efficiency of the DC-DC converter 20.

[0100] Alternatively, as a third modified example of the embodiment, the charging system 1k may monitor the first parameter and the second parameter to calculate the system efficiency, and dynamically control the voltage Vbus to increase (e.g., maximize) the efficiency while taking into account the third parameter. In this case, the control circuit 30k may be configured as shown in FIG. 11. FIG. 11 is a diagram showing the functional configuration of the control circuit 30k in the third modified example of the embodiment. The control circuit 30k has a system efficiency calculation unit 41j, a storage unit 42j, and a determination unit 43j instead of the storage unit 34 and the target voltage determination unit 35 (see FIG. 3).

[0101] The operation of the system efficiency calculation unit 41j is the same as that of the system efficiency calculation unit 41j of the control circuit 30k. The storage unit 42j stores the power efficiency R and the environmental temperature T in association with their timing. The determination unit 43j compares the power efficiency calculated at the first timing with the power efficiency calculated at the second timing. The determination unit 43j determines the direction in which the power efficiency increases for each of the operating conditions (e.g., frequency or pulse width) of the switching elements SW1 and SW2 and the operating conditions (e.g., frequency or pulse width) of the switching elements SW11 to SW14, based on the comparison result and the third parameter. The determination unit 43j supplies the determination result to the first control unit 36 ​​and the second control unit 37, respectively. In response to this, the first control unit 36 ​​adjusts the operating conditions to increase the power efficiency and causes the switching elements SW1 and SW2 to perform switching operations. The second control unit 37 adjusts the operating conditions to increase the power efficiency and causes the switching elements SW11 to SW14 to perform switching operations.

[0102] For example, the control circuit 30k may search for the maximum point of the power efficiency R by a hill-climbing method, as shown in Fig. 12. Fig. 12 is a diagram showing the operation of the control circuit 30k in the third modified example of the embodiment.

[0103] At timing t11, under the condition that the switching elements SW1, SW2, SW11 to SW14 are operating under the operating condition C11 at the environmental temperature T11, the system efficiency calculation unit 41j calculates the power efficiency R11, and the combination P11 (T11, C11, R11) is stored in the storage unit 42j. In order to search for the maximum point of the power efficiency R, the first control unit 36 ​​and the second control unit 37 increase the operating condition (for example, the frequency Fsw) of the switching elements SW1, SW2, SW11 to SW14 from C11 to C12.

[0104] At timing t12, the system efficiency calculation unit 41j calculates the power efficiency R12 while the switching element is operating under the operating condition C12, and the combination P12 (T12, C12, R12) is stored in the storage unit 42j. The determination unit 43j compares the power efficiencies R11 and R12. If the comparison result is R11 <R12 If so, the determination unit 43j determines that the change in the increasing direction of the operating conditions from C11 to C12 is a change in the direction that increases power efficiency, taking into account the environmental temperature T11. In response to this, the first control unit 36 ​​and the second control unit 37 increase the operating conditions of the switching elements SW1, SW2, SW11 to SW14 from C12 to C13.

[0105] At timing t13, the system efficiency calculation unit 41j calculates the power efficiency R13 while the switching element is operating under the operating condition C13, and the combination P13 (T13, C13, R13) is stored in the storage unit 42j. The determination unit 43j compares the power efficiencies R12 and R13. If the comparison result is R12 <R13 If so, the determination unit 43j determines that the change in the increasing direction of the operating conditions from C12 to C13 is a change in the direction that increases power efficiency, taking into account the environmental temperature T11. In response to this, the first control unit 36 ​​and the second control unit 37 increase the operating conditions of the switching elements SW1, SW2, SW11 to SW14 from C13 to C14.

[0106] At timing t14, the system efficiency calculation unit 41j calculates the power efficiency R14 while the switching element is operating under the operating condition C14, and the combination P14 (T14, C14, R14) is stored in the storage unit 42j. The determination unit 43j compares the power efficiencies R13 and R14. If the comparison result is R13>R14 If so, the determination unit 43j determines that the change in the operating condition from C13 to C14 in the increasing direction is a change in the direction of decreasing power efficiency. In response to this, the first control unit 36 ​​and the second control unit 37 return the operating conditions of the switching elements SW1, SW2, SW11 to SW14 from C14 to C13. In response to this, the first control unit 36 ​​and the second control unit 37 return the operating conditions of the switching elements SW1, SW2, SW11 to SW14 from C14 to C13. As a result, the control circuit 30k determines that the operating condition C13 is an operating condition near the maximum power efficiency, and ends the search.

[0107] In this way, the control circuit 30k sequentially calculates the power efficiency according to the third parameter in addition to the first and second parameters, and controls the voltage Vbus while searching for a power efficiency that is large (e.g., maximized). This makes it possible to more appropriately respond to dynamic changes and further improve power efficiency in real time.

[0108] Although several embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included within the scope and spirit of the invention, as well as within the scope of the invention described in the claims and their equivalents. [Explanation of symbols]

[0109] 1,1i,1j,1k charging system 10 AC / DC converter 20 DC-DC converter 30, 30i, 30j, 30k control circuit

Claims

1. an AC-DC converter connected between an input node and an intermediate node, the AC-DC converter being connectable to a power source via the input node; a DC-DC converter connected between the intermediate node and an output node, the DC-DC converter being connectable to a battery via the output node; a control circuit that controls the voltage of the intermediate node in accordance with a first parameter related to input power of the AC-DC converter, a second parameter related to output power of the DC-DC converter, and a third parameter related to an environmental temperature so that a sum of a loss of the AC-DC converter and a loss of the DC-DC converter is reduced; Equipped with the control circuit has correspondence information in which the first parameter, the second parameter, the third parameter, the sum, and the voltage of the intermediate node are associated with each other for a plurality of voltage values ​​of the intermediate node; the control circuit acquires the first parameter, the second parameter, and the third parameter, and when there are a plurality of sums corresponding to the acquired first parameter, the acquired second parameter, and the acquired third parameter in the correspondence information, determines, as a target value, a sum among the plurality of sums that minimizes the sum of the loss of the AC-DC converter and the loss of the DC-DC converter; The control circuit controls a switching element in the AC-DC converter so that the voltage of the intermediate node becomes the target value. Charging system.

2. The control circuit determines a target value of the voltage of the intermediate node so that the sum of the loss of the AC-DC converter and the loss of the DC-DC converter is small, and controls operating conditions of switching elements in the AC-DC converter so that the voltage of the intermediate node reaches the target value. The charging system of claim 1 .

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