CN108988311B

CN108988311B - Power conversion device and power conversion circuit

Info

Publication number: CN108988311B
Application number: CN201810564750.XA
Authority: CN
Inventors: 田中秀和
Original assignee: Denso Corp
Current assignee: Denso Corp
Priority date: 2017-06-05
Filing date: 2018-06-04
Publication date: 2021-09-17
Anticipated expiration: 2038-06-04
Also published as: DE102018113216A1; JP6551464B2; CN108988311A; JP2018207680A

Abstract

The first circuit and the second circuit are connected in parallel between a positive terminal and a negative terminal to which a power supply is connected. The first circuit includes a plurality of first switching elements and a first freewheeling diode. The second circuit includes a plurality of second switching elements, a second flywheel diode, a protection switching element, and a protection diode. The first freewheeling diode has a higher current rating than the second freewheeling diode. The sum of forward voltages of the plurality of second freewheel diodes and the protection diode connected in series between the positive terminal and the negative terminal is larger than the sum of forward voltages of the plurality of first freewheel diodes connected in series between the positive terminal and the negative terminal.

Description

Power conversion device and power conversion circuit

Technical Field

The present disclosure relates to a power conversion device and a power conversion circuit.

Background

The following circuits are known. As described in japanese patent publication No. 4483751, when the secondary battery is reversely connected, the circuit prevents the flow of the battery to the control circuit, which is opposite to the direction when the secondary battery is normally connected. The circuit has two Field Effect Transistors (FETs) connected in series to a supply conductor connecting a supply terminal to the control circuit. When the two FETs are P-channel metal oxide semiconductor FETs (mosfets), the sources of the two FETs are connected together. The drain of the first of the two FETs is connected to the power supply terminal side. The drain of the second of the two FETs is connected to the control circuit side. Therefore, the anode of the parasitic diode of the first FET is located on the power supply terminal side. The cathode of the parasitic diode of the second FET is located on the first FET side.

In the circuit structure of the above-mentioned japanese patent publication No. 4483751, when the secondary battery is reversely connected, a reverse bias is applied to one parasitic diode of the two FETs. Thereby preventing current flow to the control circuit during reverse connection.

However, the circuit described in japanese patent publication No. 4483751 has two FETs. Therefore, the physical size may become large.

Disclosure of Invention

Therefore, it is desirable to provide a power conversion device and a power conversion circuit in which damage and an increase in physical size caused by energization during reverse connection are suppressed.

A first exemplary embodiment of the present disclosure provides a power conversion apparatus including a first circuit and a second circuit connected in parallel between a positive terminal and a negative terminal to which a power supply is connected.

The first circuit includes a plurality of first branches. Each first branch comprises: a plurality of first switching elements connected in series between the positive terminal and the negative terminal; and first flywheel diodes connected in parallel to the plurality of first switching elements, respectively.

The second circuit includes a plurality of second branches and a protection element. Each second branch comprises: a plurality of second switching elements connected in series between the positive terminal and the negative terminal; and second flywheel diodes connected in parallel to the plurality of second switching elements, respectively. A protection element protects the plurality of second branches from the power source energizing the positive and negative terminals during reverse connection.

The protection element includes a protection switch element connected in series to each of the plurality of second legs between the positive terminal and the negative terminal, and a protection diode connected in parallel to the protection switch element such that an anode is on the negative terminal side and a cathode is on the positive terminal side.

The first freewheeling diode has a higher current rating than the second freewheeling diode. The sum of forward voltages of the plurality of second freewheel diodes and the protection diode connected in series between the positive terminal and the negative terminal is larger than the sum of forward voltages of the plurality of first freewheel diodes connected in series between the positive terminal and the negative terminal.

A second exemplary embodiment of the present disclosure provides a power conversion circuit connected in parallel to a circuit between a positive terminal and a negative terminal to which a power source is connected. The circuit includes a plurality of first branches. Each first branch comprises: a plurality of first switching elements connected in series between the positive and negative terminals; and first flywheel diodes connected in parallel to the plurality of first switching elements, respectively.

The power conversion circuit includes a plurality of second branches and a protection element. Each second branch comprises: a plurality of second switching elements connected in series between the positive terminal and the negative terminal; and second flywheel diodes connected in parallel to the plurality of second switching elements, respectively. A protection element protects the plurality of second branches from the power source energizing the positive and negative terminals during reverse connection.

The protection element includes a protection switch element connected in series to each of the plurality of second legs between the positive terminal and the negative terminal, and a protection diode connected in parallel to the protection switch element such that the anode is on the negative terminal side and the cathode is on the positive terminal side.

As a result, during reverse connection of the power supply, current flows preferentially to the first freewheeling diode rather than to the second freewheeling diode and the protection diode. Therefore, the energization of the second circuit (power conversion circuit) during the reverse connection is suppressed. Thereby, even in the case of a single protection element, energization of the power conversion circuit during reverse connection is suppressed. Therefore, an increase in the physical size of the power conversion circuit is suppressed. As a result, an increase in the physical size of the power conversion apparatus is suppressed.

As described above, the first freewheel diode has a higher rated current than the second freewheel diode. Therefore, even if energization occurs during reverse connection, damage to the first circuit can be suppressed.

Reference signs placed between parentheses shall be construed as limiting the claim. The reference signs placed in parentheses are provided for simply indicating correspondence with the elements described according to the embodiments and do not necessarily indicate the elements described according to the embodiments themselves. The recitation of reference signs placed between parentheses shall not be construed as unnecessarily narrowing the claim.

Drawings

In the drawings:

fig. 1 is a block diagram of the overall structure of a motor control device according to a first embodiment;

fig. 2 is a plan view of the entire structure of the rotor inverter;

FIG. 3 is a block diagram of the current during reverse connection;

FIG. 4 is a graph of the amount of current during reverse connection;

fig. 5 is a schematic circuit diagram for explaining the amount of current during reverse connection.

Detailed Description

Hereinafter, an embodiment in which the power conversion apparatus of the present disclosure is applied to a motor control apparatus of a vehicle will be described with reference to the drawings.

(first embodiment)

The motor control device 100 according to the present embodiment will be described with reference to fig. 1 to 5. The motor control device 100 controls the motor 200 based on a request instruction from a high-order electronic control unit (ECU; not shown). The motor control device 100 and the motor 200 constitute a so-called Integrated Starter Generator (ISG).

The motor control device 100 is integrated with the motor 200. That is, the motor control device 100 and the motor 200 form a so-called electromechanical integrated structure.

The motor 200 is connected to the crankshaft of the internal combustion engine through a belt therebetween. The internal combustion engine is mounted on a vehicle. Thus, the motor 200 and the crankshaft rotate in synchronization. When the motor 200 is driven to rotate by the motor control device 100, the rotation is transmitted to the crankshaft. As a result, the crankshaft rotates. Conversely, when the crankshaft is driven to rotate, the rotation is transmitted to the motor 200. As a result, the motor 200 rotates. The motor 200 is driven by the motor control device 100 to rotate autonomously. As a result, the start of the internal combustion engine or the assist of the vehicle running is performed. Further, the motor 200 rotates based on the rotation of the crankshaft. As a result, the motor 200 generates electric power. Hereinafter, a brief description will be given of the motor 200, followed by a description of the motor control device 100.

As shown in fig. 1, the motor 200 includes a rotor 201 and a stator 202. In addition, the motor 200 includes a shaft and a pulley (not shown). The shaft is rotatably provided to the housing 300 of the motor control device 100. The tip of the shaft is exposed to the outside of the housing 300. The pulley is disposed at a top end of the shaft. The belt is coupled to a pulley. As a result, the rotation of the crankshaft is transmitted to the pulley via the belt. Conversely, rotation of the shaft is transmitted to the crankshaft via the belt. The motor 200 corresponds to a rotating electric machine.

The central portion of the shaft is received within the housing 300. The rotor 201 is disposed at a central portion of the shaft. In addition, the stator 202 is disposed at the periphery of the rotor 201.

The rotor 201 includes a rotor coil 203. The rotor 201 also includes a fixing portion (not shown) that fixes the rotor coil 203 to the shaft. The fixing portion has a cylindrical shape. The shaft is inserted into the hollow portion of the fixing portion and fixed. The rotor coil 203 is disposed in the fixed portion. The rotor coil 203 is electrically connected to a wire (not shown) provided in the shaft. The wires are electrically connected to slip rings on the shaft. The slip ring is annular about an axis of the shaft. The annular slip ring is in contact with the brush. The brushes are electrically connected to the motor control device 100. Current from the motor control device 100 is supplied to the brushes. Electric current is supplied to the rotor coil 203 via brushes, slip rings, and wires. As a result, a magnetic field is generated in rotor coil 203. The rotor 201 corresponds to a wound rotor.

The stator 202 includes stator coils 204. The stator 202 also includes a stator core (not shown) provided with the stator coil 204. The stator core has a cylindrical shape. The rotor 201 is provided in a hollow portion in the stator core together with the shaft. The stator coil 204 includes a U-phase stator coil 205, a V-phase stator coil 206, and a W-phase stator coil 207. The stator 202 corresponds to a wound stator.

The U-phase stator coil 205, the V-phase stator coil 206, and the W-phase stator coil 207 are each integrally coupled to the motor control device 100 with a bus bar therebetween. Three-phase ac current is supplied from motor control device 100 to U-phase stator coil 205, V-phase stator coil 206, and W-phase stator coil 207. Ac power whose phases are shifted by 120 degrees in electrical angle from each other is supplied to the U-phase stator coil 205, the V-phase stator coil 206, and the W-phase stator coil 207. As a result, a three-phase rotating magnetic field for rotating the rotor 201 is generated by the U-phase stator coil 205, the V-phase stator coil 206, and the W-phase stator coil 207. The three-phase rotating magnetic field intersects with the rotor coil 203.

When a current flows to each of the rotor coils 203 and the stator coils 204, each coil generates a magnetic field. As a result, a rotational torque is generated in the rotor coil 203. When three-phase alternating current is supplied from the motor control device 100 to the stator coil 204 as described above, the direction in which the rotational torque is generated is continuously changed. Thus, the shaft starts to rotate. The pulley also rotates with the shaft. The rotation is transmitted to the crankshaft via a belt. As a result, the crankshaft also rotates.

Conversely, when the internal combustion engine is combustion-driven and the crankshaft rotates autonomously, the rotation is transmitted to the pulley via the belt. In addition, when the crankshaft is rotated together by rotation of the wheels, the rotation is transmitted to the pulley via the belt. As a result, the shaft rotates together with the pulley. As a result, the rotor coil 203 also rotates. The magnetic field emitted from the rotor coil 203 intersects the stator coil 204. As a result, an induced voltage is generated in the stator coil 204. Therefore, a current flows to the stator coil 204. The current is supplied to the battery 400 of the vehicle via the motor control device 100. Battery 400 corresponds to a power source.

Next, the motor control device 100 will be described. As shown in fig. 1, the motor control apparatus 100 includes a positive terminal 100a and a negative terminal 100b for electrical connection with a battery 400. Positive terminal 100a is connected to the positive electrode of battery 400. The negative terminal 100b is connected to the negative electrode of the battery 400. The smoothing capacitor 100c is disposed between the positive terminal 100a and the negative terminal 100 b.

As shown in fig. 1, the motor control device 100 includes a stator inverter 30 and a rotor inverter 50. The stator inverter 30 and the rotor inverter 50 are connected in parallel between the positive terminal 100a and the negative terminal 100 b. Further, the motor control device 100 includes an ISGECU 10 and a current sensor 70. ISGECU 10 controls stator inverter 30 and rotor inverter 50. The current sensor 70 detects the current flowing through the stator inverter 30 and the rotor inverter 50. The stator inverter 30 corresponds to a first circuit and a second circuit. The rotor inverter 50 corresponds to a second circuit and a power conversion circuit.

ISGECU 10 is electrically connected to each stator inverter 30 and rotor inverter 50. The ISGECU 10 can communicate with a high-order ECU mounted in the vehicle via a bus bar or the like. A request command from the higher-order ECU is input to the ISGECU 10. The ISGECU 10 generates control signals to control the stator inverter 30 and the rotor inverter 50 based on the input request command, the detection signal from the current sensor 70, and the like. ISGECU 10 outputs control signals to stator inverter 30 and rotor inverter 50. Thus, the driving of the stator inverter 30 and the rotor inverter 50 is controlled.

Stator inverter 30 includes a U-phase leg 31, a V-phase leg 32, and a W-phase leg 33. The U-phase leg 31, the V-phase leg 32, and the W-phase leg 33 are connected in parallel between the positive terminal 100a and the negative terminal 100 b. The U-phase arm 31, the V-phase arm 32, and the W-phase arm 33 correspond to a first arm.

The U-phase leg 31, the V-phase leg 32, and the W-phase leg 33 each have a high-side switching element and a low-side switching element. The high-side switching element and the low-side switching element are connected in series in this order from the positive terminal 100a to the negative terminal 100 b. Specifically, the U-phase leg 31 has a U-phase high-side switching element 34 and a U-phase low-side switching element 35. The V-phase branch 32 has a V-phase high-side switching element 36 and a V-phase low-side switching element 37. W-phase leg 33 has a W-phase high-side switching element 38 and a W-phase low-side switching element 39. The switching element corresponds to the first switching element.

The switching elements constituting the stator inverter 30 are MOSFETs. Therefore, the switching elements each have a parasitic diode. That is, the U-phase high-side switching element 34 has a U-phase high-side diode 34 a. The U-phase low-side switching device 35 has a U-phase low-side diode 35 a. The V-phase high-side switching element 36 has a V-phase high-side diode 36 a. The V-phase low-side switching device 37 has a V-phase low-side diode 37 a. The W-phase high-side switching element 38 has a W-phase high-side diode 38 a. The W-phase low-side switching element 39 has a W-phase low-side diode 39 a. The cathode of each parasitic diode is located on the positive terminal 100a side. The anode of each parasitic diode is located on the negative terminal 100b side. The parasitic diode corresponds to the first freewheeling diode.

As shown in fig. 1, the first end of the U-phase stator coil 205, the first end of the V-phase stator coil 206, and the first end of the W-phase stator coil 207 are connected to each other. As a result, the U-phase stator coil 205, the V-phase stator coil 206, and the W-phase stator coil 208 are connected in a star connection. A second end of the U-phase stator coil 205 is connected to a center point between the U-phase high-side switching element 34 and the U-phase low-side switching element 35. A second end of the V-phase stator coil 206 is connected to a center point between the V-phase high-side switching element 36 and the V-phase low-side switching element 37. A second end of the W-phase stator coil 207 is connected to a center point between the W-phase high-side switching element 38 and the W-phase low-side switching element 39.

As a result of the above-described electrical connection structure, for example, when the U-phase high-side switching element 34, the V-phase low-side switching element 37, and the W-phase low-side switching element 39 are kept in a closed state by a control signal from the ISGECU 10, a current flows to the stator coil 204. Specifically, a current flows from the positive terminal 100a to the negative terminal 100b via the U-phase high-side switching element 34, the U-phase stator coil 205, the V-phase stator coil 206, and the V-phase low-side switching element 37. Current flows from the positive terminal 100a to the negative terminal 100b via the U-phase high-side switching element 34, the U-phase stator coil 205, the W-phase stator coil 207, and the W-phase low-side switching element 39.

When all the switching elements of the stator inverter 30 are in the off state, a reverse bias is applied to the parasitic diodes. Therefore, the current does not flow to the stator inverter 30. However, when the battery 400 is reversely connected to the motor control apparatus 100, that is, when the anode of the battery 400 is connected to the negative terminal 100b and the cathode is connected to the positive terminal 100a as shown in fig. 3, a forward bias is applied to the parasitic diode. Therefore, as indicated by the solid-line arrows, current flows to the stator inverter 30 even if the switching elements are in the off state. Specifically, a current flows from the negative terminal 100b to the positive terminal 100a via the U-phase low-side diode 35a and the U-phase high-side diode 34 a. Current flows from the negative terminal 100b to the positive terminal 100a via the V-phase low-side diode 37a and the V-phase high-side diode 36 a. Current flows from the negative terminal 100b to the positive terminal 100a via the W-phase low-side diode 39a and the W-phase high-side diode 38 a. The constituent elements are appropriately omitted in fig. 3 to clearly show the current.

Thereby, when the battery 400 is reversely connected to the motor control device 100, the current flowing from the negative terminal 100b to the positive terminal 100a flows to the parasitic diode of the stator inverter 30. According to the present embodiment, the module type power MOSFET is used as a switching element constituting the stator inverter 30. Therefore, the rated current of the switching element and the parasitic diode is high. The switching element and the parasitic diode are designed to be able to withstand even the current flowing during the reverse connection of the secondary battery 200. A so-called single-sided cooling system is used for the switching elements constituting the stator inverter 30.

The switching elements constituting the stator inverter 30 are made of silicon. Therefore, the forward voltage Vf of the parasitic diode of the switching element is about 0.6V. As shown in fig. 4, when a voltage equal to or greater than 0.6V is applied to the parasitic diode, the amount of current rapidly increases.

The rotor inverter 50 includes an E-phase leg 51 and an F-phase leg 52. The E-phase leg 51 and the F-phase leg 52 are connected in parallel between the positive terminal 100a and the negative terminal 100 b. The branch corresponds to the second branch. The rotor inverter 50 constitutes a full bridge circuit. The rotor inverter 50 includes a protection element 53. The protection element 53 is connected in series to the E-phase leg 51 and the F-phase leg 52 between the positive terminal 100a and the negative terminal 100 b. As shown in fig. 2, the E-phase leg 51, the F-phase leg 52, and the protection element 53 are mounted on the printed circuit board 50 a. ISGECU 10 is also mounted on printed circuit board 50 a.

Fig. 2 shows a structure in which the ISGECU 10 is mounted on the front surface of the printed circuit board 50a together with the E-phase branch 51, the F-phase branch 52, and the protection element 53. However, for example, the E-phase leg 51, the F-phase leg 52, and the protection element 53 may be mounted on the front surface of the printed circuit board 50a, and the ISGECU 10 may be mounted on the rear surface of the printed circuit board 50 a.

The E-phase branch 51 has an E-phase high-side switching element 54 and an E-phase low-side switching element 55. The E-phase high-side switching element 54 and the E-phase low-side switching element 55 are connected in series in this order from the positive terminal 100a to the negative terminal 100 b. The F-phase leg 52 has an F-phase high-side switching element 56 and an F-phase low-side switching element 57. The F-phase high-side switching element 56 and the F-phase low-side switching element 57 are connected in series in this order from the positive terminal 100a to the negative terminal 100 b. The switching element corresponds to a second switching element.

The protection element 53 has a protection switch element 58 provided between the positive terminal 100a and the E-phase high-side switch element 54. The protection switching element 58 is also positioned between the positive terminal 100a and the F-phase high-side switching element 56. Thereby, the protection switching element 58 is provided in common between the E-phase arm 51 and the F-phase arm 52.

When current flows to the rotor coil 203, the protection switching element 58 is controlled to be in a closed state by the ISGECU 10. When the ignition switch is turned on, ISGECU 10 determines whether battery 400 is normally connected to positive terminal 100a and negative terminal 100 b. When it is determined that the secondary battery 400 is normally connected to the positive terminal 100a and the negative terminal 100b, the ISGECU 10 controls the protection switching element 58 to be always in the closed state.

The switching elements constituting the rotor inverter 50 are MOSFETs. Therefore, each switching element has a parasitic diode. That is, the E-phase high-side switching element 54 has an E-phase high-side diode 54 a. The E-phase low-side switching device 55 has an E-phase low-side diode 55 a. The F-phase high-side switching element 56 has an F-phase high-side diode 56 a. The F-phase low-side switching element 57 has an F-phase low-side diode 57 a. The protection switching element 58 has a protection diode 58 a. The cathode of each parasitic diode is located on the positive terminal 100a side. The anode is located on the negative terminal 100b side. The parasitic diodes of the E-phase branch 51 and the F-phase branch 52 correspond to second freewheeling diodes.

The brushes are connected to a center point between the E-phase high-side switching element 54 and the E-phase low-side switching element 55 and a center point between the F-phase high-side switching element 56 and the F-phase low-side switching element 57. The brushes are in contact with slip rings of the shaft. The slip ring is electrically connected to the rotor coil 203 through a wire. Thereby, the center point between the E-phase high-side switching element 54 and the E-phase low-side switching element 55 and the center point between the F-phase high-side switching element 56 and the F-phase low-side switching element 57 are each electrically connected to the rotor coil 203. Specifically, as shown in fig. 1, the center point between the E-phase high-side switching element 54 and the E-phase low-side switching element 55 is electrically connected to the first end of the rotor coil 203. A center point between the F-phase high-side switching element 56 and the F-phase low-side switching element 57 is electrically connected to a second end of the rotor coil 203.

As a result of the above-described connection structure, for example, when the protection switching element 58, the E-phase high-side switching element 54, and the F-phase low-side switching element 57 are held in a closed state by a control signal from the ISGECU 10, a current flows from the first end of the rotor coil 203 to the second end of the rotor coil 203. That is, a current flows from the positive terminal 100a to the negative terminal 100b via the protection switching element 58, the E-phase high-side switching element 54, the rotor coil 203, and the F-phase low-side switching element 57. For example, when the protection switching element 58, the F-phase high-side switching element 56, and the E-phase low-side switching element 55 are held in the closed state, a current flows from the second end of the rotor coil 203 to the first end of the rotor coil 203. That is, a current flows from the positive terminal 100a to the negative terminal 100b via the protection switching element 58, the F-phase high-side switching element 56, the rotor coil 203, and the E-phase low-side switching element 55.

When all the switching elements of the rotor inverter 50 are in the off state, a reverse bias is applied to the parasitic diodes. Therefore, the current does not flow to the rotor inverter 50. However, when the secondary battery 400 is reversely connected to the motor control device 100, a forward bias is applied to the parasitic diode. Therefore, the current flows to the rotor inverter 50. However, the energization of the rotor inverter 50 is suppressed for the reason described below. The switching elements constituting the rotor inverter 50 have a lower rated current than the switching elements constituting the stator inverter 30. The rotor inverter 50 has a smaller physical size than the stator inverter 30. The difference in rated current between the rotor inverter 50 and the stator inverter 30 is generated due to the difference in forming material, chip size, heat dissipation structure, and the like.

The current sensor 70 detects the amount of current flowing through the stator coil 204 and the rotor coil 203. More specifically, the current sensor 70 includes a shunt resistor provided to the stator inverter 30 and the rotor inverter 50. Current sensor 70 includes U-phase shunt resistor 71, V-phase shunt resistor 72, W-phase shunt resistor 73, E-phase shunt resistor 74, and F-phase shunt resistor 75.

The U-phase shunt resistance 71 is provided between the U-phase low-side switching element 35 and the negative terminal 100 b. The V-phase shunt resistor 72 is provided between the V-phase low-side switching element 37 and the negative terminal 100 b. The W-phase shunt resistor 73 is provided between the W-phase low-side switching element 39 and the negative terminal 100 b. The E-phase shunt resistor 74 is provided between the E-phase low-side switching element 55 and the negative terminal 100 b. The F-phase shunt resistor 75 is provided between the F-phase low-side switching element 57 and the negative terminal 100 b.

The ISGECU 10 stores the resistance value of the shunt resistance. The amount of current flowing to each low-side switching element of each branch is detected based on the resistance value and the voltage across the shunt resistance. Thereby estimating the amount of current flowing through the stator coil 204 and the rotor coil 203. The current sensor 70 is not limited to the above example. For example, a configuration may be used in which the amount of current is detected based on a magnetic field generated by the flow of current.

Next, the flow of current during the reverse connection of battery 400 will be described. The switching elements constituting the rotor inverter 50 are made of silicon, similarly to the switching elements constituting the stator inverter 30. Therefore, as shown in fig. 4, the forward voltage Vf of the parasitic diode constituting the switching element of the rotor inverter 50 is also about 0.6V.

Fig. 5 shows a U-phase leg 31 as a representative constituent element of the stator inverter 30. The characteristics of the V-phase arm 32 and the W-phase arm 33 are the same as those of the U-phase arm 31. Therefore, the description thereof is omitted. Fig. 5 shows in a similar manner a protection element 53 and an E-phase branch 51 as representative constituent elements of the rotor inverter 50. The characteristics of the F-phase arm 52 are the same as those of the E-phase arm 51. Therefore, the description thereof is omitted.

As shown in fig. 5, in the U-phase leg 31, a U-phase low-side diode 35a is connected in series with a U-phase high-side diode 34 a. Therefore, the sum of the forward voltages of the U-phase legs 31 is about 1.2V. In view of this, in the E-phase arm 51, an E-phase low-side diode 55a, an E-phase high-side diode 54a, and a protection diode 58a are connected in series. Therefore, the sum of the forward voltages of the E-phase branch 51 is about 1.8V. Thereby, the number of diodes connected in series in the E-phase arm 51 is larger than the number of diodes connected in series in the U-phase arm 31. Therefore, the sum of the forward voltages of the E-phase legs 51 is larger. This similarly applies to the other legs, i.e., the F-phase leg 52, the V-phase leg 32, and the W-phase leg 33. Therefore, each leg of the rotor inverter 50 has a larger sum of forward voltages than each leg of the stator inverter 30.

As shown in fig. 5, when the battery 400 is reversely connected to the positive terminal 100a and the negative terminal 100b, the negative terminal 100b is on the high potential side and the positive terminal 100a is on the low potential side. In fig. 5, symbol T represents the potential of the negative terminal 100 b.

During such reverse connection, for example, when the current IU shown in fig. 4 flows to the U-phase leg 31, a voltage of about 0.9V is applied to each of the U-phase low-side diode 35a and the U-phase high-side diode 34a of the U-phase leg 31. Therefore, as shown in fig. 5, the voltage between the negative terminal 100b and the positive terminal 100a is about 1.8V. A voltage of 1.8V is also applied to the protection diode 58a, the E-phase low-side diode 55a, and the E-phase high-side diode 54 a. In this case, a voltage of about 0.6V is applied to each of the protection diode 58a, the E-phase low-side diode 55a, and the E-phase high-side diode 54 a. As described above, the forward voltage Vf of the parasitic diode constituting the switching element of the rotor inverter is about 0.6V. Therefore, as shown in fig. 4, the current IE flowing through the E-phase branch 51 at this time is substantially zero.

As another example, for example, when a current approximately twice the above-described current IU flows, a voltage of about 1.0V is applied to each of the U-phase low-side diode 35a and the U-phase high-side diode 34 a. Therefore, the voltage between the negative terminal 100b and the positive terminal 100a is about 2.0V. In this case, a voltage of about 0.67V is applied to the protection diode 58, the E-phase low-side diode 55a, and the E-phase high-side diode 54 a. Therefore, the current IE flowing through the E-phase branch 51 at this time is again a value close to zero. As described above, the current flow in the rotor inverter 50 is suppressed during the reverse connection of the battery 400 due to the difference in the I-V characteristic of the diode and the sum of the forward voltages.

Next, the operational effects of the motor control device 100 and the rotor inverter 50 according to the present embodiment will be described. As described above, the sum of the forward voltages of each branch of the rotor inverter 50 is larger than the sum of the forward voltages of each branch of the stator inverter 30 due to the protection element 53. Therefore, during the reverse connection of the battery 400, the current actively flows to the diode of each branch of the stator inverter 30, not to the diode of each branch of the rotor inverter 50. As a result, energization to each branch of the rotor inverter 50 during reverse connection is suppressed. Thereby, even in the case of a single protection element 53, the energization of the rotor inverter 50 during the reverse connection is suppressed. Therefore, an increase in the physical size of the rotor inverter 50 is suppressed as compared with a structure having two protection elements. Therefore, an increase in the physical size of the motor control device 100 is suppressed.

As described above, the rated current of the switching elements and the parasitic diodes constituting the stator inverter 30 is high. The switching element and the parasitic diode are designed to withstand even the current during the reverse connection of the secondary battery 400. Therefore, even if energization occurs during reverse connection, damage to the stator inverter 30 is suppressed.

Protection element 53 is connected in series so as to be shared between phase E branch 51 and phase F branch 52. As a result, an increase in the number of components is suppressed as compared with a structure in which the E-phase arm 51 and the F-phase arm 52 each have the protective element 53. In addition, an increase in the physical size of the rotor inverter 50 is suppressed. Therefore, an increase in the physical size of the motor control device 100 is suppressed.

The switching elements constituting the stator inverter 30 are mounted on the heat radiation unit 30 a. As a result, for example, a temperature increase in the stator inverter 30 caused by energization during reverse connection is suppressed. Therefore, occurrence of damage to the stator inverter 30 is suppressed.

The foregoing describes preferred embodiments of the present disclosure. However, the present disclosure is not limited to the above-described embodiments. Various modifications may be made without departing from the spirit of the disclosure.

(other embodiments)

According to the present embodiment, an example is given in which the motor 200 is coupled to a crankshaft of an internal combustion engine mounted to a vehicle through a belt. However, a structure in which the motor 200 is coupled to the crankshaft through a transmission mechanism may also be used.

According to the present embodiment, an example is given in which the protection switch element 58 is positioned between the positive terminal 100a and the E-phase high-side switch element 54, and is also positioned between the positive terminal 100a and the F-phase high-side switch element 56. However, a configuration may also be employed in which the protection switching element 58 is positioned between the negative terminal 100b and the E-phase low-side switching element 55, and is also positioned between the negative terminal 100a and the F-phase low-side switching element 57.

According to the present embodiment, an example is given in which the rotor inverter 50 is a full bridge circuit. However, the rotor inverter 50 may constitute a half-bridge circuit.

According to the present embodiment, an example is given in which the switching elements constituting the stator inverter 30 and the rotor inverter 50 are MOSFETs. However, the switching elements constituting the stator inverter 30 and the rotor inverter 50 are not limited to the above example. For example, an Insulated Gate Bipolar Transistor (IGBT) may be used. In this case, an additional freewheeling diode is connected in anti-parallel to the switching element.

According to the present embodiment, an example is given in which a single-sided cooling system is used in the switching elements constituting the stator inverter 30. However, the system for cooling the switching elements constituting the stator inverter 30 is not limited to the above example. For example, a two-sided cooling system may be used. In addition, a cooling system utilizing a fluid coolant may also be used.

According to the present embodiment, an example is given in which the stator inverter 30 and the rotor inverter 50 are made of silicon. However, for example, silicon carbide having a wider band gap than silicon may be used as the forming material of the stator inverter 30 and the rotor inverter 50. As a result, the operation at high temperature can be stabilized.

In addition, the formation materials of the rotor inverter 50 and the stator inverter 30 may be different as long as the sum of the forward voltages of each branch of the rotor inverter 50 is greater than the sum of the forward voltages of each branch of the stator inverter 30. For example, the rotor inverter 50 may be made of silicon carbide, and the stator inverter 30 may be made of silicon.

In the rotor inverter 50, the material for forming the E-phase arm 51 and the F-phase arm 52 may be different from the material for forming the protective element 53. For example, the E-phase leg 51 and the F-phase leg 52 may be made of silicon. The protective element 53 may be made of silicon carbide.

According to the present embodiment, an example is given in which the switching elements constituting the rotor inverter 50 have a lower rated current than the switching elements constituting the stator inverter 30. However, for example, in the switching elements of the rotor inverter 50, the rated current of the protection switching elements 58 may be set equal to the rated current of the switching elements constituting the stator inverter 30. In this case, similar to the switching elements of the stator inverter 30, the module type power MOSFET may be used as the protection switching element 58.

Claims

1. A power conversion apparatus, characterized by comprising:

a first circuit (30) and a second circuit (50), the first circuit (30) and the second circuit (50) being connected in parallel between a positive terminal (100a) and a negative terminal (100b) to which a power supply (400) is connected, wherein,

the first circuit comprises a plurality of first branches (31, 32, 33), each first branch comprising: a plurality of first switch elements (34, 35, 36, 37, 38, 39) connected in series between the positive terminal and the negative terminal; and first freewheel diodes (34a, 35a, 36a, 37a, 38a, 39a) connected in parallel with the plurality of first switching elements, respectively,

the second circuit includes:

a plurality of second branches (51, 52), each second branch including a plurality of second switching elements (54, 55, 56, 57) connected in series between the positive terminal and the negative terminal and a second freewheel diode (54a, 55a, 56a, 57a) connected in parallel to the plurality of second switching elements, respectively; and

a protection element (53) that protects the plurality of second branches from power supply energizing the positive terminal and the negative terminal during reverse connection,

the protection element includes a protection switch element (58) connected in series to each of the plurality of second legs between the positive terminal and the negative terminal, and a protection diode (58a) connected in parallel to the protection switch element such that an anode is on the negative terminal side and a cathode is on the positive terminal side,

the first freewheeling diode has a higher current rating than the second freewheeling diode, and

the sum of forward voltages of the plurality of second flywheel diodes and the protection diode connected in series between the positive terminal and the negative terminal is larger than the sum of forward voltages of the plurality of first flywheel diodes connected in series between the positive terminal and the negative terminal.

2. The power conversion apparatus according to claim 1,

the protection switch element is shared among a plurality of the second branches, and is provided on either one of a positive terminal side and a negative terminal side.

3. The power conversion apparatus according to claim 1, further comprising:

a printed circuit board (50a) on which the second circuit is mounted; and

a heat dissipating unit (30a) to which the first circuit is mounted.

4. The power conversion apparatus according to claim 2, characterized by further comprising:

a printed circuit board (50a) on which the second circuit is mounted; and

a heat dissipating unit (30a) to which the first circuit is mounted.

5. The power conversion apparatus according to claim 3,

the first circuit is electrically connected to a wound stator (202) of a rotating electrical machine (200); and is

The second circuit is electrically connected to a wound rotor (201) of the rotating electrical machine.

6. The power conversion apparatus according to claim 4,

7. The power conversion apparatus according to claim 5,

the rotating electrical machine is integrally coupled to the first circuit and the second circuit.

8. The power conversion apparatus according to claim 6,

9. The power conversion apparatus according to claim 7,

the power conversion device is mounted on a vehicle.

10. The power conversion apparatus according to claim 8,

the power conversion device is mounted on a vehicle.

11. The power conversion apparatus according to any one of claims 1 to 10,

the first switching element has a higher current rating than the second switching element and the protection switching element.

12. The power conversion apparatus according to any one of claims 1 to 10,

the first switching element and the protection switching element have a higher rated current than the second switching element.

13. The power conversion apparatus according to any one of claims 1 to 10,

the first switching element is a MOSFET and the first freewheeling diode is a parasitic diode of the first switching element;

the second switching element is a MOSFET and the second freewheeling diode is a parasitic diode of the second switching element; and is

The protection switching element is a MOSFET and the protection diode is a parasitic diode of the protection switching element.

14. A power conversion circuit connected in parallel to a circuit (30) between positive and negative terminals (100a, 100b) to which a power source (400) is connected, characterized in that the circuit comprises a plurality of first branches (31, 32, 33), each first branch comprising: a plurality of first switch elements (34, 35, 36, 37, 38, 39) connected in series between the positive terminal and the negative terminal; and first flywheel diodes (34a, 35a, 36a, 37a, 38a, 39a) connected in parallel to the plurality of first switching elements, respectively, the power conversion circuit including:

the protection element includes:

a protection switch element (58) connected in series to each of the plurality of second legs between the positive terminal and the negative terminal; and

a protection diode (58a) connected in parallel to the protection switching element such that an anode is on a negative terminal side and a cathode is on a positive terminal side,