Auxiliary circuit, power conversion device, and motor unit

Abstract

The auxiliary circuit is used in a power conversion device that has a conversion unit, a drive power supply unit, and a resonance unit, and that converts an input voltage applied between a positive line and a negative line into an output voltage. The auxiliary circuit includes an auxiliary switch unit, an auxiliary drive unit, and an auxiliary power supply unit. The conversion unit has a branch including a high-side switching element and a low-side switching element connected in series between a positive line and a negative line, and converts an input voltage to an output voltage by switching on and off of the high-side switching element and the low-side switching element. The drive power supply unit generates a drive voltage for controlling the ON / OFF of the high-side switching element and the low-side switching element on the basis of an input voltage. The resonance unit has a resonance inductor and a resonance capacitor connected to a main connection point, which is a connection point between the high-side switching element and the low-side switching element. The auxiliary switching unit has an auxiliary switching element provided between the main connection point and the resonant inductor, and is configured such that, when the auxiliary switching element is turned on, a current flows between the main connection point and the resonant inductor. The auxiliary drive unit has an auxiliary driver that controls the ON / OFF of the auxiliary switching element. The auxiliary power supply unit has an auxiliary power supply capacitor for generating an operating voltage of the auxiliary driver, and the auxiliary power supply unit is configured such that, when the auxiliary switching element is turned off and the high-side switching element is turned off, a current flows from the driving power supply unit to the main connection point via the auxiliary power supply capacitor when the low-side switching element is turned on.

Description

Auxiliary circuits, power conversion devices, motor units Technical Field

[0001] The technology disclosed herein relates to an auxiliary circuit for a power conversion device, a power conversion device, and a motor unit. Background Technology

[0002] Patent Document 1 discloses a resonant inverter device. This resonant inverter device includes an inverter circuit, a resonant circuit connected to the output terminal of the inverter circuit, and a control circuit for controlling the inverter circuit and the resonant circuit.

[0003] The inverter circuit includes main circuits for each phase and capacitors. In each main circuit, a main switching element connected to the positive terminal of the power supply and a main switching element connected to the negative terminal of the power supply are connected together. Diodes are connected in parallel to each of these main switching elements. Capacitors are connected in parallel with the main switching elements in each main circuit. The resonant circuit includes multiple auxiliary switching elements and an inductor for resonance.

[0004] In this resonant inverter device, the capacitor is appropriately charged and discharged by switching multiple auxiliary switching elements on and off, utilizing the resonant current of the inductor and capacitor. This enables zero-voltage switching. Furthermore, it reduces losses incurred when the main switching elements are turned on or off.

[0005] Patent Document 1 does not disclose or provide any guidance on how to generate the operating voltage of the auxiliary driver (not disclosed in Patent Document 1) for controlling the on / off switching of the auxiliary switching element used to switch the connection between the inductor and capacitor for resonant switching.

[0006] For example, to generate the operating voltage of the auxiliary driver, it is conceivable to set up another power source (e.g., a floating power source with an insulated transformer) independently of the drive power source. In this case, the drive power source generates the operating voltage of the drive driver (the driver that controls the on / off switching of the main switching element) based on the input voltage to the power conversion device, while the other power source independently generates the operating voltage of the auxiliary driver based on the input voltage to the power conversion device. However, with such a separate power source, circuit miniaturization and cost reduction become difficult.

[0007] Existing technical documents

[0008] Patent documents

[0009] Patent Document 1: Japanese Patent Application Publication No. 2003-18876 Summary of the Invention

[0010] The purpose of the technology disclosed herein is to provide an auxiliary circuit that can generate the operating voltage of the auxiliary driver without the need for a separate power source such as a floating power supply.

[0011] The disclosed technology relates to an auxiliary circuit for a power conversion device, which includes a conversion section, a drive power supply section, and a resonant section, converting an input voltage applied between a positive and a negative line into an output voltage. The auxiliary circuit includes an auxiliary switching section, an auxiliary drive section, and an auxiliary power supply section. The conversion section includes a branch comprising a high-side switching element and a low-side switching element connected in series between the positive and negative lines, converting the input voltage into the output voltage by switching the high-side and low-side switching elements on and off. The drive power supply section generates a drive voltage based on the input voltage for controlling the on and off of the high-side and low-side switching elements. The resonant section includes a resonant inductor and a resonant capacitor, the resonant capacitor being connected to the connection point between the high-side and low-side switching elements, i.e., the main connection point. The auxiliary switching section includes an auxiliary switching element disposed between the main connection point and the resonant inductor, configured such that when the auxiliary switching element is on, current flows between the main connection point and the resonant inductor. The auxiliary drive unit has an auxiliary driver that controls the on / off state of the auxiliary switching element. The auxiliary power supply unit has an auxiliary power capacitor for generating the operating voltage of the auxiliary driver. The auxiliary power supply unit is configured such that, when the low-side switching element becomes on while the auxiliary switching element is off and the high-side switching element is off, current flows from the drive power supply unit through the auxiliary power capacitor to the main connection point.

[0012] According to the technology disclosed herein, the auxiliary power supply capacitor can be charged using the drive voltage generated by the drive power supply unit. Therefore, the operating voltage of the auxiliary driver can be generated in the auxiliary power supply capacitor. Thus, according to the technology disclosed herein, the operating voltage of the auxiliary driver can be generated without the need for a separate power supply such as a floating power supply (a power supply with an insulated transformer). Attached Figure Description

[0013] Figure 1 is a block diagram showing the structure of the motor unit according to Embodiment 1.

[0014] Figure 2 is a circuit diagram showing the structure of the auxiliary circuit in Embodiment 1.

[0015] Figure 3 is a waveform diagram illustrating the first operation of the power conversion device (the operation of turning on the high-side switching element after turning off the low-side switching element).

[0016] Figure 4 is a waveform diagram illustrating the second operation of the power conversion device (the operation of turning on the low-side switching element after turning off the high-side switching element).

[0017] Figure 5 is a circuit diagram showing the structure of a power conversion device according to a variation of Embodiment 1.

[0018] Figure 6 is a circuit diagram showing the structure of a power conversion device according to a variation of Embodiment 1, Example 2.

[0019] Figure 7 is a circuit diagram showing the structure of a power conversion device according to a variation of Embodiment 1, Example 3.

[0020] Figure 8 is a circuit diagram showing the structure of a power conversion device according to a variation 4 of Embodiment 1.

[0021] Figure 9 is a circuit diagram showing the structure of the power conversion device according to Embodiment 2.

[0022] Figure 10 is a circuit diagram showing the structure of the power conversion device according to Embodiment 3. Detailed Implementation

[0023] The embodiments will now be described in detail with reference to the accompanying drawings. The embodiments described below represent specific examples of this disclosure. Therefore, the numerical values, constituent elements, arrangement and connection methods of constituent elements, and processes and their order shown in the following embodiments are examples and are not intended to limit this disclosure. Therefore, constituent elements in the following embodiments that are not described in the independent claims representing the highest-level concept of this disclosure are described as arbitrary constituent elements. The figures are schematic diagrams and are not necessarily strictly illustrated. The same or equivalent parts in the figures are labeled with the same reference numerals and their descriptions are cited.

[0024] (Implementation Method 1)

[0025] Figure 1 is a block diagram showing the structure of the motor unit 1 according to Embodiment 1. The motor unit 1 is connected to a power supply 11 and includes a motor 12 and a power conversion device 10. The power supply 11 is a DC power supply. The power supply 11 is, for example, a battery such as a lithium-ion battery or a nickel-metal hydride battery. The motor 12 is a three-phase AC brushless motor.

[0026] The power conversion device 10 is connected to the power supply 11 and the motor 12. The power conversion device 10 converts the power supply voltage supplied from the power supply 11 into a desired output voltage, and uses the output voltage to drive the motor 12. The power conversion device 10 includes a conversion unit 20, a drive power supply unit 25, a control power supply unit 26, n (n is an integer greater than or equal to 1) drive units 30, a resonant unit 40, n auxiliary circuits 50, and a control unit 55.

[0027] The input voltage to the power conversion device 10 is a DC power supply voltage supplied from the power source 11, which is a DC power source. The output voltage from the power conversion device 10 is a three-phase AC voltage. n is 3. The positive line L1 is connected to the positive terminal of the power source 11. The negative line L2 is connected to the negative terminal of the power source 11. The negative line L2 is grounded.

[0028] A smoothing capacitor C1 is connected between the positive line L1 and the negative line L2. The smoothing capacitor C1 smooths the power supply voltage (DC power supply voltage) applied between the positive line L1 and the negative line L2. Specifically, the smoothing capacitor C1 reduces power supply ripple and absorbs surge voltage. For example, the smoothing capacitor C1 is made of an electrolytic capacitor.

[0029] [Transformation Section]

[0030] The conversion unit 20 has n branches 21. The n branches 21 have the same structure as each other. Each branch 21 includes a high-side switching element SWH, a low-side switching element SWL, a high-side freewheeling diode DH, and a low-side freewheeling diode DL. The conversion unit 20 converts the input voltage into an output voltage by switching the high-side switching element SWH and the low-side switching element SWL included in the branch 21 on and off.

[0031] <Switching Components>

[0032] A high-side switching element SWH and a low-side switching element SWL are connected in series between the positive line L1 and the negative line L2. One end (collector or drain) of the high-side switching element SWH is connected to the positive line L1. The other end (emitter or source) of the high-side switching element SWH is connected to one end (collector or drain) of the low-side switching element SWL. The other end (emitter or source) of the low-side switching element SWL is connected to the negative line L2. Hereinafter, the high-side switching element SWH and the low-side switching element SWL will be collectively referred to as "switching element SW".

[0033] The switching element SW is switched on and off in accordance with the drive signal (voltage) supplied to its control terminal (gate). Specifically, when the voltage at the control terminal of the switching element SW exceeds a threshold voltage, the switching element SW switches from off to on. When the voltage at the control terminal of the switching element SW is lower than the threshold voltage, the switching element SW switches from on to off. Examples of switching elements SW include field-effect transistors (FETs) such as metal-oxide-semiconductor field-effect transistors (MOSFETs) and insulated-gate bipolar transistors (IGBTs).

[0034] <Freewheeling diode>

[0035] The high-side freewheeling diode DH is connected in parallel with the high-side switching element SWH. The high-side freewheeling diode DH is positive in the direction from the main connection point P2 towards the positive line L1. The low-side freewheeling diode DL is connected in parallel with the low-side switching element SWL. The low-side freewheeling diode DL is positive in the direction from the negative line L2 towards the main connection point P2. Hereinafter, the high-side freewheeling diode DH and the low-side freewheeling diode DL will be collectively referred to as "freewheeling diode DF". The freewheeling diode DF can be a parasitic diode parasitic on the switching element SW, or it can be a diode element separately formed from the switching element SW.

[0036] <Main Connector>

[0037] In branch 21, output line L3 is connected to the connection point P2, which is the connection point between the high-side switching element SWH and the low-side switching element SWL. "The connection point between the high-side switching element SWH and the low-side switching element SWL" refers to the point on the connecting line that electrically connects the high-side switching element SWH and the low-side switching element SWL. The same applies to subsequent "connection points".

[0038] The conversion unit 20 has three branches 21 corresponding to the three phases of the motor 12. The main connection point P2 in the branch 21 corresponding to the U phase of the motor 12 is connected to the output line L3 connected to the input terminal of the U phase of the motor 12. The main connection point P2 in the branch 21 corresponding to the V phase of the motor 12 is connected to the output line L3 connected to the input terminal of the V phase of the motor 12. The main connection point P2 in the branch 21 corresponding to the W phase of the motor 12 is connected to the output line L3 connected to the input terminal of the W phase of the motor 12.

[0039] [Drive Power Supply Section]

[0040] The drive power supply unit 25 generates a drive voltage based on the input voltage. The drive voltage is the voltage used to control the switching on and off of the high-side switching element SWH and the low-side switching element SWL. The drive voltage (DC voltage) generated by the drive power supply unit 25 is supplied to the drive line L25.

[0041] For example, the drive power supply unit 25 consists of a voltage regulator, an input smoothing capacitor that smooths the input voltage of the voltage regulator, and an output smoothing capacitor that smooths the output voltage of the voltage regulator. The voltage regulator can be a series voltage regulator or a switching voltage regulator. For example, the input voltage is 280V and the drive voltage is 15V.

[0042] [Power Supply Control Section]

[0043] The control power supply unit 26 generates the operating voltage of the control unit 55 based on the drive voltage generated by the drive power supply unit 25. The structure of the control power supply unit 26 is the same as that of the drive power supply unit 25. For example, the operating voltage (DC voltage) of the control unit 55 is 3.3V.

[0044] [Driver Section]

[0045] n drive units 30 correspond to n branches 21. Each of the n drive units 30 operates based on a drive voltage generated by the drive power supply unit 25, controlling the switching on and off of the high-side switching element SWH and the low-side switching element SWL included in the branch 21 corresponding to that drive unit 30. Each of the n drive units 30 has the same structure as the others. Figure 2 is a circuit diagram showing the structure of the auxiliary circuit 50 in Embodiment 1. As shown in Figure 2, the drive unit 30 has a high-side drive unit 31 and a low-side drive unit 35.

[0046] <High-side drive unit>

[0047] The high-side drive unit 31 controls the switching on and off of the high-side switching element SWH. The high-side drive unit 31 includes a high-side driver 32, a high-side power supply unit 33, and a high-side output resistor element 34.

[0048] High-side driver

[0049] The high-side driver 32 has a positive terminal and a negative terminal. A voltage (operating voltage of the high-side driver 32) is applied to the positive terminal of the high-side driver 32 to turn on the high-side switching element SWH. A voltage (a voltage serving as a reference potential) is applied to the negative terminal of the high-side driver 32 to turn off the high-side switching element SWH.

[0050] In response to the control of the control unit 55, the high-side driver 32 connects one of the positive and negative terminals to the control terminal of the high-side switching element SWH, thereby supplying one of the voltages of the positive and negative terminals to the control terminal of the high-side switching element SWH. Through this operation, the signal level (voltage) of the drive signal supplied from the high-side driver 32 to the control terminal of the high-side switching element SWH is switched, thus switching the high-side switching element SWH on and off.

[0051] One end of the high-side power supply capacitor C33 (described later) is connected to the positive terminal of the high-side driver 32. The voltage generated in the high-side power supply capacitor C33 (the operating voltage of the high-side driver 32) is applied to the positive terminal of the high-side driver 32. The negative terminal of the high-side driver 32 is connected to the main connection point P2, and the voltage at the main connection point P2 is applied to it.

[0052] High-side power supply section

[0053] The high-side power supply unit 33 includes a high-side power supply capacitor C33. The high-side power supply capacitor C33 is a capacitor used to generate the operating voltage of the high-side driver 32. The high-side power supply unit 33 is configured such that when the high-side switching element SWH is off and the low-side switching element SWL is on, current flows from the drive power supply unit 25 through the high-side power supply capacitor C33 to the main connection point P2.

[0054] In addition to the high-side power supply capacitor C33, the high-side power supply section 33 also includes a high-side power supply diode D33 and a high-side power supply resistor R33. The high-side power supply section 33 constitutes a bootstrap circuit.

[0055] The high-side power supply capacitor C33 is connected between the drive power supply unit 25 and the main connection point P2. Specifically, one end of the high-side power supply capacitor C33 is connected to the drive line L25 via the high-side power supply diode D33 and the high-side power supply resistor R33. The other end of the high-side power supply capacitor C33 is connected to the main connection point P2.

[0056] A high-side power supply diode D33 is connected between the drive power supply unit 25 and the high-side power supply capacitor C33. The high-side power supply diode D33 is positively oriented from the drive power supply unit 25 toward the high-side power supply capacitor C33. A high-side power supply resistor R33 is connected in series with the high-side power supply diode D33 between the drive power supply unit 25 and the high-side power supply capacitor C33. Specifically, the anode of the high-side power supply diode D33 is connected to the drive line L25 via the high-side power supply resistor R33. The cathode of the high-side power supply diode D33 is connected to one end of the high-side power supply capacitor C33.

[0057] High-side output resistor element

[0058] The high-side output resistor element 34 is connected between the output terminal of the high-side driver 32 and the control terminal (gate) of the high-side switching element SWH.

[0059] <Low-side drive unit>

[0060] The low-side drive unit 35 controls the switching on and off of the low-side switching element SWL. The low-side drive unit 35 includes a low-side driver 36 and a low-side output resistor element 37.

[0061] Low-side driver

[0062] The structure of the low-side driver 36 is the same as that of the high-side driver 32. A voltage (operating voltage of the low-side driver 36) is applied to the positive terminal of the low-side driver 36 to turn on the low-side switching element SWL. A voltage (a voltage serving as a reference potential) is applied to the negative terminal of the low-side driver 36 to turn off the low-side switching element SWL.

[0063] In response to the control of the control unit 55, the low-side driver 36 connects one of its positive and negative terminals to the control terminal of the low-side switching element SWL, thereby supplying one of the voltages of the positive and negative terminals to the control terminal of the low-side switching element SWL. This operation switches the signal level (voltage) of the drive signal supplied from the low-side driver 36 to the control terminal of the low-side switching element SWL, thus switching the low-side switching element SWL on and off.

[0064] One end of the high-side power supply capacitor C33 is connected to the positive terminal of the low-side driver 36. A voltage generated in the high-side power supply capacitor C33 is applied to the positive terminal of the low-side driver 36. A negative line L2 is connected to the negative terminal of the low-side driver 36. A voltage in the negative line L2 is applied to the negative terminal of the low-side driver 36. Thus, the voltage generated in the high-side power supply capacitor C33 is supplied not only to the positive terminal of the high-side driver 32 but also to the positive terminal of the low-side driver 36. The high-side power supply capacitor C33 is a capacitor used to generate the operating voltage of both the high-side driver 32 and the low-side driver 36.

[0065] Low-side output resistance element

[0066] The low-side output resistor 37 is connected between the output terminal of the low-side driver 36 and the control terminal (gate) of the low-side switching element SWL.

[0067] [Resonance Section]

[0068] The resonant section 40 includes a resonant inductor 41, a resonant power supply capacitor 42, a first resonant diode 43, a second resonant diode 44, and n resonant capacitors 45.

[0069] <Resonant Inductors and Resonant Power Supply Capacitors>

[0070] The resonant power supply capacitor 42 is connected to the resonant inductor 41. Specifically, one end of the resonant inductor 41 is connected to n auxiliary circuits 50. The other end of the resonant inductor 41 is connected to one end of the resonant power supply capacitor 42. The other end of the resonant power supply capacitor 42 is connected to the negative line L2. The resonant power supply capacitor 42 is connected between the resonant inductor 41 and the negative line L2.

[0071] <Resonant Diode>

[0072] A first resonant diode 43 and a second resonant diode 44 are connected in series between the positive line L1 and the negative line L2. The first resonant diode 43 is connected to the positive line L1. The second resonant diode 44 is connected to the negative line L2. A resonant inductor 41 and n auxiliary circuits 50 are connected at the resonant connection point P4, i.e., the connection point between the first resonant diode 43 and the second resonant diode 44. The first resonant diode 43 is positive in the direction from the resonant connection point P4 toward the positive line L1. The second resonant diode 44 is positive in the direction from the negative line L2 toward the resonant connection point P4.

[0073] <Resonant Capacitor>

[0074] n resonant capacitors 45 correspond to n branches 21. Each of the n resonant capacitors 45 is connected to the main connection point P2 (the connection point between the high-side switching element SWH and the low-side switching element SWL) in the branch 21 corresponding to that capacitor 45. Specifically, one end of the resonant capacitor 45 is connected to the main connection point P2. The other end of the resonant capacitor 45 is connected to the negative line L2. The resonant capacitor 45 and the low-side switching element SWL are connected in parallel between the main connection point P2 and the negative line L2.

[0075] [Auxiliary Circuit]

[0076] As shown in Figure 1, n auxiliary circuits 50 correspond to n branches 21. Each of the n auxiliary circuits 50 has the same structure. As shown in Figure 2, each auxiliary circuit 50 includes an auxiliary switch section 60, an auxiliary drive section 70, and an auxiliary power supply section 80.

[0077] Auxiliary Switch Section

[0078] The auxiliary switching unit 60 includes an auxiliary switching element 61. The auxiliary switching element 61 is disposed between the main connection point P2 and the resonant inductor 41. The auxiliary switching unit 60 is configured such that when the auxiliary switching element 61 is turned on, current flows between the main connection point P2 and the resonant inductor 41.

[0079] The auxiliary switching unit 60 includes a first auxiliary switching element 61a and a second auxiliary switching element 61b. The first auxiliary switching element 61a and the second auxiliary switching element 61b are disposed between the main connection point P2 and the resonant inductor 41. The auxiliary switching unit 60 is configured such that, when the first auxiliary switching element 61a is turned on and the second auxiliary switching element 61b is turned off, current flows from the main connection point P2 to the resonant inductor 41, and when the first auxiliary switching element 61a is turned off and the second auxiliary switching element 61b is turned on, current flows from the resonant inductor 41 to the main connection point P2. The first auxiliary switching element 61a corresponds to the aforementioned auxiliary switching element 61.

[0080] Specifically, in addition to the first auxiliary switching element 61a and the second auxiliary switching element 61b, the auxiliary switching unit 60 also has a first auxiliary diode 62a, a second auxiliary diode 62b, a third auxiliary diode 62c, and a fourth auxiliary diode 62d.

[0081] The first auxiliary switching element 61a and the second auxiliary switching element 61b are connected in parallel between the main connection point P2 and the resonant inductor 41.

[0082] A first auxiliary diode 62a is connected between the first auxiliary switching element 61a and the resonant inductor 41. The first auxiliary diode 62a is positive in the direction from the first auxiliary switching element 61a toward the resonant inductor 41. A second auxiliary diode 62b is connected in parallel with the first auxiliary switching element 61a between the main connection point P2 and the first auxiliary diode 62a. The second auxiliary diode 62b is positive in the direction from the first auxiliary diode 62a toward the main connection point P2.

[0083] The third auxiliary diode 62c is connected between the second auxiliary switching element 61b and the resonant inductor 41. The third auxiliary diode 62c is positively oriented from the resonant inductor 41 toward the second auxiliary switching element 61b. The fourth auxiliary diode 62d is connected in parallel with the second auxiliary switching element 61b between the main connection point P2 and the third auxiliary diode 62c. The fourth auxiliary diode 62d is positively oriented from the main connection point P2 toward the third auxiliary diode 62c.

[0084] Specifically, one end (collector or drain) of the first auxiliary switching element 61a is connected to the main connection point P2. The other end (emitter or source) of the first auxiliary switching element 61a is connected to the anode of the first auxiliary diode 62a. The cathode of the first auxiliary diode 62a is connected to the resonant connection point P4. The anode of the second auxiliary diode 62b is connected to the other end of the first auxiliary switching element 61a. The cathode of the second auxiliary diode 62b is connected to one end of the first auxiliary switching element 61a.

[0085] One end (collector or drain) of the second auxiliary switching element 61b is connected to the cathode of the third auxiliary diode 62c. The other end (emitter or source) of the second auxiliary switching element 61b is connected to the main connection point P2. The anode of the third auxiliary diode 62c is connected to the resonant connection point P4. The anode of the fourth auxiliary diode 62d is connected to the other end of the second auxiliary switching element 61b. The cathode of the fourth auxiliary diode 62d is connected to one end of the second auxiliary switching element 61b.

[0086] The structures of the first auxiliary switching element 61a and the second auxiliary switching element 61b are the same as those of the switching element SW. When the voltage at the control terminal of the first auxiliary switching element 61a exceeds the threshold voltage, the first auxiliary switching element 61a switches from open to closed; when the voltage at the control terminal of the first auxiliary switching element 61a is lower than the threshold voltage, the first auxiliary switching element 61a switches from closed to open. The operation of the second auxiliary switching element 61b is the same as that of the first auxiliary switching element 61a.

[0087] The structures of the first auxiliary switching element 61a and the second auxiliary diode 62b can also be the same as those of the switching element SW and the freewheeling diode DF. Similarly, the structures of the second auxiliary switching element 61b and the fourth auxiliary diode 62d can also be the same as those of the switching element SW and the freewheeling diode DF.

[0088] <Auxiliary Drive Section>

[0089] The auxiliary drive unit 70 includes an auxiliary driver 71. The auxiliary driver 71 controls the on / off switching of the auxiliary switching element 61. The auxiliary drive unit 70 includes a first auxiliary driver 71a, a second auxiliary driver 71b, a first auxiliary output resistor element 72a, and a second auxiliary output resistor element 72b. The first auxiliary driver 71a corresponds to the auxiliary driver 71 described above.

[0090] First Auxiliary Driver

[0091] The first auxiliary driver 71a controls the switching on and off of the first auxiliary switching element 61a. The structure of the first auxiliary driver 71a is the same as that of the high-side driver 32. A voltage for turning on the first auxiliary switching element 61a (the operating voltage of the first auxiliary driver 71a) is applied to the positive terminal of the first auxiliary driver 71a. A voltage for turning off the first auxiliary driver 71a (a voltage serving as a reference potential) is applied to the negative terminal of the first auxiliary driver 71a.

[0092] In response to the control of the control unit 55, the first auxiliary driver 71a connects one of its positive and negative terminals to its control terminal, thereby supplying one of the voltages of the positive and negative terminals to the control terminal of the first auxiliary switching element 61a. This operation switches the signal level (voltage) of the drive signal supplied from the first auxiliary driver 71a to the control terminal of the first auxiliary switching element 61a, thus switching the first auxiliary switching element 61a on and off.

[0093] One end of the first auxiliary power supply capacitor 81a (described later) is connected to the positive terminal of the first auxiliary driver 71a. A voltage generated in the first auxiliary power supply capacitor 81a is applied to the positive terminal of the first auxiliary driver 71a. The connection point between the first auxiliary switching element 61a and the first auxiliary diode 62a is connected to the negative terminal of the first auxiliary driver 71a. A voltage at the connection point between the first auxiliary switching element 61a and the first auxiliary diode 62a is applied to the negative terminal of the first auxiliary driver 71a.

[0094] First Auxiliary Output Resistive Element

[0095] The first auxiliary output resistor element 72a is connected between the output terminal of the first auxiliary driver 71a and the control terminal (gate) of the first auxiliary switching element 61a. The first auxiliary output resistor element 72a is equivalent to "the auxiliary output resistor element 72 connected between the output terminal of the auxiliary driver 71 and the control terminal of the auxiliary switching element 61".

[0096] Second Auxiliary Driver

[0097] The second auxiliary driver 71b controls the on / off state of the second auxiliary switching element 61b.

[0098] The second auxiliary driver 71b controls the switching on and off of the second auxiliary switching element 61b. The structure of the second auxiliary driver 71b is the same as that of the high-side driver 32. A voltage for turning on the second auxiliary switching element 61b (the operating voltage of the second auxiliary driver 71b) is applied to the positive terminal of the second auxiliary driver 71b. A voltage for turning off the second auxiliary driver 71b (a voltage serving as a reference potential) is applied to the negative terminal of the second auxiliary driver 71b. In response to the control of the control unit 55, the second auxiliary driver 71b connects one of its positive and negative terminals to its control terminal, thereby supplying one of the voltages of the positive and negative terminals to the control terminal of the second auxiliary switching element 61b. Through this operation, the signal level (voltage) of the drive signal supplied from the second auxiliary driver 71b to the second auxiliary switching element 61b is switched, thereby switching the on and off of the second auxiliary switching element 61b.

[0099] One end of the second auxiliary power supply capacitor 81b (described later) is connected to the positive terminal of the second auxiliary driver 71b. A voltage generated in the second auxiliary power supply capacitor 81b is applied to the positive terminal of the second auxiliary driver 71b. The negative terminal of the second auxiliary driver 71b is connected to the main connection point P2, and a voltage at the main connection point P2 is applied to it.

[0100] Second Auxiliary Output Resistor Element

[0101] The second auxiliary output resistor element 72b is connected between the output terminal of the second auxiliary driver 71b and the control terminal (gate) of the second auxiliary switching element 61b.

[0102] [Auxiliary Power Supply Section]

[0103] The auxiliary power supply unit 80 includes an auxiliary power supply capacitor 81. The auxiliary power supply capacitor 81 is a capacitor used to generate the operating voltage of the auxiliary driver 71. The auxiliary power supply unit 80 is configured such that when the auxiliary switching element 61 is off and the high-side switching element SWH is off, and the low-side switching element SWL becomes on, current flows from the drive power supply unit 25 through the auxiliary power supply capacitor 81 to the main connection point P2.

[0104] The auxiliary power supply unit 80 includes a first auxiliary power supply capacitor 81a and a second auxiliary power supply capacitor 81b. The first auxiliary power supply capacitor 81a is a capacitor used to generate the operating voltage of the first auxiliary driver 71a. The second auxiliary power supply capacitor 81b is a capacitor used to generate the operating voltage of the second auxiliary driver 71b. The first auxiliary power supply capacitor 81a corresponds to the auxiliary power supply capacitor 81 described above.

[0105] The auxiliary power supply unit 80 is configured such that, when the first auxiliary switching element 61a and the second auxiliary switching element 61b are off and the high-side switching element SWH is off, and the low-side switching element SWL becomes on, current flows from the drive power supply unit 25 through the first auxiliary power supply capacitor 81a and the second auxiliary power supply capacitor 81b to the main connection point P2.

[0106] Specifically, in addition to the first auxiliary power supply capacitor 81a and the second auxiliary power supply capacitor 81b, the auxiliary power supply unit 80 also includes a first auxiliary power supply diode 82a, a first auxiliary power supply resistor element 83a, a second auxiliary power supply diode 82b, and a second auxiliary power supply resistor element 83b. The first auxiliary power supply capacitor 81a, the first auxiliary power supply diode 82a, and the first auxiliary power supply resistor element 83a constitute a bootstrap circuit. Similarly, the second auxiliary power supply capacitor 81b, the second auxiliary power supply diode 82b, and the second auxiliary power supply resistor element 83b constitute a bootstrap circuit.

[0107] First Auxiliary Power Supply Capacitor

[0108] The first auxiliary power supply capacitor 81a is connected between the connection point of the first auxiliary switching element 61a and the first auxiliary diode 62a and the drive power supply unit 25. Specifically, one end of the first auxiliary power supply capacitor 81a is connected to the drive line L25 via the first auxiliary power supply diode 82a and the first auxiliary power supply resistor element 83a. The other end of the first auxiliary power supply capacitor 81a is connected to the connection point of the first auxiliary switching element 61a and the first auxiliary diode 62a.

[0109] First Auxiliary Power Supply Diode and First Auxiliary Power Supply Resistor

[0110] A first auxiliary power supply diode 82a is connected between the drive power supply unit 25 and the first auxiliary power supply capacitor 81a. The first auxiliary power supply diode 82a is positively oriented from the drive power supply unit 25 toward the first auxiliary power supply capacitor 81a. A first auxiliary power supply resistor element 83a is connected in series with the first auxiliary power supply diode 82a between the drive power supply unit 25 and the first auxiliary power supply capacitor 81a. Specifically, the anode of the first auxiliary power supply diode 82a is connected to the drive line L25 via the first auxiliary power supply resistor element 83a. The cathode of the first auxiliary power supply diode 82a is connected to one end of the first auxiliary power supply capacitor 81a.

[0111] Second Auxiliary Power Supply Capacitor

[0112] The second auxiliary power supply capacitor 81b is connected between the main connection point P2 and the drive power supply unit 25. Specifically, one end of the second auxiliary power supply capacitor 81b is connected to the drive line L25 via the second auxiliary power supply diode 82b and the second auxiliary power supply resistor element 83b. The other end of the second auxiliary power supply capacitor 81b is connected to the main connection point P2.

[0113] Second auxiliary power supply diode and second auxiliary power supply resistor

[0114] The second auxiliary power supply diode 82b is connected between the drive power supply unit 25 and the second auxiliary power supply capacitor 81b. The second auxiliary power supply diode 82b is positively oriented from the drive power supply unit 25 toward the second auxiliary power supply capacitor 81b. The second auxiliary power supply resistor element 83b is connected in series with the second auxiliary power supply diode 82b between the drive power supply unit 25 and the second auxiliary power supply capacitor 81b. Specifically, the anode of the second auxiliary power supply diode 82b is connected to the drive line L25 via the second auxiliary power supply resistor element 83b. The cathode of the second auxiliary power supply diode 82b is connected to one end of the second auxiliary power supply capacitor 81b.

[0115] The first auxiliary power supply diode 82a corresponds to "the auxiliary power supply diode 82 connected between the drive power supply unit 25 and the auxiliary power supply capacitor 81, with the direction from the drive power supply unit 25 toward the auxiliary power supply capacitor 81 being positive". The first auxiliary power supply resistor element 83a corresponds to "the auxiliary power supply resistor element 83 connected in series with the auxiliary power supply diode 82 between the drive power supply unit 25 and the auxiliary power supply capacitor 81".

[0116] [Various sensors and storage units]

[0117] Various sensors (not shown) and a storage unit (not shown) are provided in the power conversion device 10. Examples of various sensors include a current sensor that detects the three-phase current flowing through the motor 12, and a rotation angle sensor that detects the rotation angle of the motor 12. Various information obtained from the various sensors is sent to the control unit 55. The storage unit stores various information for control in the power conversion device 10.

[0118] [Control Department]

[0119] The control unit 55 is connected to each part of the power conversion device 10 in a way that allows signal transmission. Based on information obtained from various sensors, information stored in the storage unit, and information provided from the outside, the control unit 55 controls each part of the power conversion device 10 to control the operation of the power conversion device 10.

[0120] For example, the control unit 55 includes a processor and a memory that stores various programs for causing the processor to operate. Various functions of the control unit 55 are achieved by the processor executing the various programs stored in the memory.

[0121] The control unit 55 controls n drive units 30 to convert the input voltage into a desired output voltage by switching the switching elements SW in the n branches 21. For example, the control unit 55 controls the high-side driver 32 and the low-side driver 36 of the n drive units 30 to control the switching of the high-side switching elements SWH and the low-side switching elements SWL in the n branches 21 so that the speed of the motor 12 becomes the target speed (supplying the motor 12 with an output voltage to make the speed of the motor 12 become the target speed).

[0122] The control unit 55 controls n auxiliary circuits 50 to reduce the switching losses (switching losses) during the switching of the switching elements SW in the n branches 21. The control unit 55 controls the auxiliary drivers 71 (first auxiliary driver 71a and second auxiliary driver 71b) of the n auxiliary circuits 50 to control the switching of the auxiliary switching elements 61 (first auxiliary switching element 61a and second auxiliary switching element 61b) of the auxiliary circuits 50, so as to perform zero-voltage switching in the n branches 21.

[0123] [Charging action of the auxiliary power capacitor]

[0124] Next, referring to FIG2, the charging operation of the auxiliary power supply capacitor 81 (first auxiliary power supply capacitor 81a and second auxiliary power supply capacitor 81b) in the auxiliary circuit 50 will be described.

[0125] When the auxiliary switching element 61 (first auxiliary switching element 61a and second auxiliary switching element 61b) is off and the high-side switching element SWH is off, when the low-side switching element SWL becomes on, current flows from the drive power supply unit 25 to the auxiliary power supply unit 80 via the drive line L25.

[0126] A portion of the current flowing into the auxiliary power supply section 80 passes sequentially through the first auxiliary power supply resistor element 83a, the first auxiliary power supply diode 82a, and the first auxiliary power supply capacitor 81a within the auxiliary power supply section 80, and then through the second auxiliary diode 62b in the auxiliary switch section 60. Subsequently, a portion of the current flowing into the auxiliary power supply section 80 flows sequentially through the main connection point P2 and the on-state low-side switch element SWL to the negative line L2. This forms a charging path for the first auxiliary power supply capacitor 81a, and the first auxiliary power supply capacitor 81a is charged.

[0127] The remaining portion of the current flowing into the auxiliary power supply section 80 passes sequentially through the second auxiliary power supply resistor element 83b, the second auxiliary power supply diode 82b, and the second auxiliary power supply capacitor 81b within the auxiliary power supply section 80. Then, the remaining portion of the current flowing into the auxiliary power supply section 80 flows sequentially through the main connection point P2 and the on-state low-side switching element SWL to the negative line L2. This forms a charging path for the second auxiliary power supply capacitor 81b, and the second auxiliary power supply capacitor 81b is charged.

[0128] [Operation of the power conversion device]

[0129] Next, the operation of the power conversion device 10 will be described with reference to Figures 3 and 4. Figure 3 is a waveform diagram illustrating the first operation of the power conversion device 10 (the operation of turning on the high-side switching element after turning off the low-side switching element). Figure 4 is a waveform diagram illustrating the second operation of the power conversion device 10 (the operation of turning on the low-side switching element after turning off the high-side switching element).

[0130] In Figures 3 and 4, the drive signal supplied from the high-side driver 32 to the high-side switching element SWH is designated as "high-side drive signal SSH", and the drive signal supplied from the low-side driver 36 to the low-side switching element SWL is designated as "low-side drive signal SSL". The drive signal supplied from the first auxiliary driver 71a to the first auxiliary switching element 61a is designated as "first auxiliary drive signal S61a", and the drive signal supplied from the second auxiliary driver 71b to the second auxiliary switching element 61b is designated as "second auxiliary drive signal S61b".

[0131] In Figures 3 and 4, the current flowing in the high-side switching element SWH is designated as "high-side switching current iSWH", the current flowing in the low-side switching element SWL is designated as "low-side switching current iSWL", and the current flowing in the low-side freewheeling diode DL is designated as "low-side diode current iDL".

[0132] In Figures 3 and 4, the current flowing through the auxiliary circuit 50 in the resonant section 40 (resonant inductor 41) and branch 21 is defined as "resonant current i50", and the voltage at the main connection point P2, i.e., the voltage of each phase (e.g., U phase) of the motor 12, is defined as "motor voltage VM". The resonant current i50 is "positive" in the direction from the resonant inductor 41 toward the main connection point P2.

[0133] [The first action of the power conversion device]

[0134] The first operation of the power conversion device 10 (the operation of turning on the high-side switching element after turning off the low-side switching element) will be described with reference to FIG3.

[0135] When time t1 is reached, the signal level of the low-side drive signal SSL changes from high level to low level, and the low-side switching element SWL changes from on to off.

[0136] When time t2 is reached, the low-side switching element SWL becomes open, and the low-side diode current iDL (regenerative current) begins to flow.

[0137] When time t3 is reached, the signal level of the second auxiliary drive signal S61b changes from low level to high level, and the second auxiliary switch element 61b changes from open to closed.

[0138] At time t4, the second auxiliary switching element 61b turns on, and the resonant current i50 begins to flow from the resonant inductor 41 of the resonant section 40 to the main connection point P2 of branch 21. Consequently, the low-side diode current iDL gradually decreases. During the period from time t4 to time t8, the resonant current i50 gradually increases from zero to its maximum value and then gradually decreases to zero.

[0139] At time t5, the rising resonant current i50 reaches the motor current iM. The motor current iM is the current flowing in each phase (e.g., phase U) of motor 12. Consequently, the low-side diode current iDL becomes zero. Then, the motor voltage VM rises from zero.

[0140] At time t6, the decreasing resonant current i50 reaches the motor current iM. At this time, the motor voltage VM reaches the DC voltage VDC. The DC voltage VDC is the input voltage applied between the positive line L1 and the negative line L2. Therefore, the voltage at the main connection point P2 is the same as the voltage at the positive line L1, and the potential difference across the high-side switching element SWH is zero.

[0141] At time t6, the signal level of the high-side drive signal SSH changes from low to high, and the high-side switching element SWH changes from open to closed when the potential difference across the two ends of the high-side switching element SWH is zero.

[0142] At time t6, the signal level of the second auxiliary drive signal S61b changes from high level to low level, and the second auxiliary switch element 61b changes from on to off.

[0143] When time t7 is reached, the high-side switching element SWH turns on, and the absolute value of the high-side switching current iSWH becomes the motor current iM. That is, the motor current iM begins to flow through the high-side switching element SWH.

[0144] When time t8 is reached, the resonant current i50 becomes zero. The first operation of the power conversion device 10 (the operation of turning on the high-side switching element after turning off the low-side switching element) ends.

[0145] In this way, zero-voltage switching of the high-side switching element SWH can be performed during the first operation of the power conversion device 10. As a result, the switching losses in the high-side switching element SWH can be reduced.

[0146] [The second operation of the power conversion device]

[0147] The second operation of the power conversion device 10 (the operation of turning on the low-side switching element after turning off the high-side switching element) will be described with reference to FIG4.

[0148] When time t1 is reached, the signal level of the high-side drive signal SSH changes from high level to low level, and the high-side switching element SWH changes from on to off.

[0149] When time t2 is reached, the high-side switching element SWH becomes open, the resonant capacitor 45, which is driven by the motor current, begins to discharge, and the motor voltage VM begins to decrease.

[0150] When time t3 is reached, the signal level of the first auxiliary drive signal S61a changes from low level to high level, and the first auxiliary switch element 61a changes from open to closed.

[0151] When time t4 is reached, the first auxiliary switching element 61a is turned on, and the resonant current i50 begins to flow from the resonant capacitor 45 through the main connection point P2 of branch 21 to the resonant inductor 41.

[0152] At time t5, the motor voltage VM reaches "half of the DC voltage VDC". Therefore, the increase in the resonant current i50 is suppressed. The motor voltage VM gradually decreases until it becomes zero after time t5. When the motor voltage VM becomes zero, the voltage at the main connection point P2 is the same as the voltage in the negative line L2, and the potential difference across the low-side switching element SWL is zero.

[0153] When time t6 is reached, the resonant current i50 becomes zero, and the low-side diode current iDL begins to flow.

[0154] When time t7 is reached, the signal level of the low-side drive signal SSL changes from low to high, and the low-side switching element SWL changes from open to closed when the potential difference across the low-side switching element SWL is zero.

[0155] At time t7, the signal level of the first auxiliary drive signal S61a changes from high level to low level, and the first auxiliary switch element 61a changes from on to off.

[0156] When time t8 is reached, the low-side switching element SWL turns on, and the absolute value of the low-side switching current iSWL becomes the motor current iM. That is, the motor current iM begins to flow through the low-side switching element SWL.

[0157] The second operation of the power conversion device 10 (the operation of turning on the low-side switching element after turning off the high-side switching element) ends.

[0158] Thus, in the second operation of the power conversion device 10, zero-voltage switching of the low-side switching element SWL can be performed. This reduces the switching losses in the low-side switching element SWL.

[0159] [Effects of Implementation Method 1]

[0160] As described above, in the motor unit 1 of Embodiment 1, the auxiliary power supply unit 80 is configured such that when the auxiliary switching element 61 is off and the high-side switching element SWH is off, and the low-side switching element SWL is turned on, current flows from the drive power supply unit 25 through the auxiliary power supply capacitor 81 to the main connection point P2 (the connection point between the high-side switching element SWH and the low-side switching element SWL).

[0161] With the above structure, the auxiliary power supply capacitor 81 can be charged using the drive voltage generated by the drive power supply unit 25. This allows the operating voltage of the auxiliary driver 71 to be generated in the auxiliary power supply capacitor 81. Thus, the operating voltage of the auxiliary driver 71 can be generated without the need for a separate power supply such as a floating power supply.

[0162] Alternatively, a power supply (e.g., a power supply with an insulated transformer) can be provided independently of the drive power supply unit 25. In this case, the drive power supply unit 25 generates the drive voltage (operating voltage of the drive unit 30) based on the input voltage to the power conversion device 10, while the other power supply independently generates the operating voltage of the auxiliary driver 71 based on the input voltage to the power conversion device 10. Therefore, compared to the case where a separate power supply is provided as described above, the auxiliary circuit can be miniaturized and its cost reduced.

[0163] (Modification 1 of Implementation Method 1)

[0164] Figure 5 is a circuit diagram showing the structure of the power conversion device 10A of Embodiment 1, Modification 1. The structure of the resonant section 40 of the power conversion device 10A of Embodiment 1, Modification 1, differs from that of the power conversion device 10 of Embodiment 1. The other structures of the power conversion device 10A of Embodiment 1, Modification 1, are the same as those of the power conversion device 10 of Embodiment 1.

[0165] In a variation of embodiment 1, the resonant section 40, in addition to having the structure of the resonant section 40 shown in FIG1 and FIG2, also has a resonant power supply capacitor 42 connected between the positive line L1 and the resonant inductor 41, and n resonant capacitors 45 respectively connected between the positive line L1 and the main connection point P2 in the n branches 21.

[0166] [Effects of Variation 1 of Implementation Method 1]

[0167] In the motor unit 1 of the modified example 1 of embodiment 1, the same effect as that of the motor unit 1 of embodiment 1 can be obtained.

[0168] In the motor unit 1 of the modified embodiment 1, the voltage (voltage across the terminals) of the resonant power capacitor 42 can be quickly set to "1 / 2 of the input voltage" shortly after the power is turned on. As a result, the operation of the power conversion device 10A during startup can be stabilized.

[0169] In the motor unit 1 of the modified embodiment 1, the resonant capacitor 45 can be arranged near the switching element SW. Therefore, wiring related to the switching element SW and the resonant capacitor 45 can be easily made on the control board (not shown).

[0170] (Modification 2 of Implementation Method 1)

[0171] Figure 6 is a circuit diagram showing the structure of the power conversion device 10B according to a modification 2 of Embodiment 1. The structure of the resonant section 40 in the power conversion device 10B of Modification 2 of Embodiment 1 differs from that of the power conversion device 10 of Embodiment 1. The power conversion device 10B of Modification 2 of Embodiment 1 includes a resonant voltage sensor 91 and a power supply voltage sensor 92. The resonant voltage sensor 91 detects the voltage (voltage across the terminals) of the resonant power supply capacitor 42. The power supply voltage sensor 92 detects the input voltage. The other structures of the power conversion device 10B of Modification 2 of Embodiment 1 are the same as those of the power conversion device 10 of Embodiment 1.

[0172] [Resonance Section]

[0173] In Modification 2 of Embodiment 1, in the resonant section 40, the resonant power supply capacitor 42 is connected between the positive line L1 and the resonant inductor 41. n resonant capacitors 45 are connected between the positive line L1 and the main connection point P2 in the n branches 21. The other structures of the resonant section 40 in Modification 2 of Embodiment 1 are the same as those in Embodiment 1.

[0174] [Effects of Variation 2 of Implementation Method 1]

[0175] In the motor unit 1 of the modified example 2 of embodiment 1, the same effect as that of the motor unit 1 of embodiment 1 can be obtained.

[0176] In the motor unit 1 of the variation 2 of embodiment 1, the power conversion device 10B can be started appropriately while monitoring the voltage of the resonant power supply capacitor 42 detected by the resonant voltage sensor 91 and the input voltage detected by the power supply voltage sensor 92.

[0177] (Modification 3 of Implementation Method 1)

[0178] Figure 7 is a circuit diagram showing the structure of the power conversion device 10C of Embodiment 1, Modification 3. The structure of the n auxiliary circuits 50 in the power conversion device 10C of Embodiment 1, Modification 3, differs from that of the power conversion device 10 of Embodiment 1. The power conversion device 10C of Embodiment 1, Modification 3, includes n driving diodes 27. The other structures of the power conversion device 10C of Embodiment 1, Modification 3, are the same as those of the power conversion device 10 of Embodiment 1.

[0179] [Auxiliary Circuit]

[0180] In Variation 3 of Embodiment 1, each of the n auxiliary circuits 50 has an auxiliary power supply unit 80 that, in addition to having the structure of the auxiliary power supply unit 80 shown in FIG. 2, also has a third auxiliary power supply diode 82c. The other structures of the auxiliary circuit 50 in Variation 3 of Embodiment 1 are the same as those of the auxiliary circuit 50 in Embodiment 1.

[0181] One end of the third auxiliary power diode 82c is connected to the drive power supply section 25 (drive line L25 in this example). The third auxiliary power diode 82c is positively oriented from one end to the other. The first auxiliary power diode 82a and the first auxiliary power resistor element 83a are connected between one end (anode) of the third auxiliary power diode 82c and the first auxiliary power capacitor 81a. The second auxiliary power diode 82b and the second auxiliary power resistor element 83b are connected between the other end (cathode) of the third auxiliary power diode 82c and the second auxiliary power capacitor 81b.

[0182] [Driver Diode]

[0183] n driving diodes 27 correspond to n driving sections 30. The n driving diodes 27 are connected between the high-side power supply section 33 and the driving power supply section 25 (driving line L25 in this example) of the driving section 30 corresponding to each driving diode 27. The n driving diodes 27 are positively oriented from the driving power supply section 25 toward the high-side power supply section 33. Specifically, the anode of the driving diode 27 is connected to the driving line L25. The cathode of the driving diode 27 is connected to one end of the high-side power supply capacitor C33 via the high-side power supply resistor element R33 and the high-side power supply diode D33 of the high-side power supply section 33.

[0184] [Effects of Variation 3 of Implementation Method 1]

[0185] In the motor unit 1 of the modified example 3 of embodiment 1, the same effect as that of the motor unit 1 of embodiment 1 can be obtained.

[0186] In the motor unit 1 of the variation 3 of embodiment 1, by providing a third auxiliary power supply diode 82c, the difference between the voltage generated in the first auxiliary power supply capacitor 81a and the voltage generated in the second auxiliary power supply capacitor 81b can be easily reduced (making these voltages the same). As a result, the difference in operation between the first auxiliary driver 71a and the second auxiliary driver 71b (e.g., the time difference between charging and discharging of the control terminal of the auxiliary switching element 61) can be easily reduced.

[0187] In the motor unit 1 of the variation 3 of embodiment 1, by providing n driving diodes 27, the difference in the voltage generated in the high-side power supply capacitor C33 included in each of the n driving units 30 can be easily reduced (making these voltages the same). As a result, the difference in operation of each of the n driving units 30 (e.g., the time difference of charging and discharging of the control terminal of the switching element SW) can be easily reduced.

[0188] (Modification 4 of Implementation Method 1)

[0189] Figure 8 is a circuit diagram showing the structure of the power conversion device 10D of Modification 4 of Embodiment 1. The structure of the n auxiliary circuits 50 of the power conversion device 10D of Modification 4 of Embodiment 1 is different from that of the power conversion device 10 of Embodiment 1. The other structures of the power conversion device 10D of Modification 4 of Embodiment 1 are the same as those of the power conversion device 10 of Embodiment 1.

[0190] [Auxiliary Circuit]

[0191] In a variation 4 of embodiment 1, in each of the n auxiliary circuits 50, the auxiliary power supply section 80 is configured such that a portion of the current flowing from the drive power supply section 25 to the high-side power supply capacitor C33 in the high-side power supply section 33 included in the drive section 30 corresponding to the auxiliary circuit 50 flows to the main connection point P2 via the second auxiliary power supply capacitor 81b.

[0192] In this example, the auxiliary power supply unit 80 of Variation 4 of Embodiment 1 has an auxiliary power line L8 instead of the second auxiliary power diode 82b and the second auxiliary power resistor element 83b shown in FIG2. The auxiliary power line L8 connects one end of the second auxiliary power capacitor 81b to one end of the high-side power capacitor C33 (the connection point between the high-side power capacitor C33 and the high-side power diode D33). The other structures of the auxiliary power supply unit 80 of Variation 4 of Embodiment 1 are the same as those of the auxiliary power supply unit 80 of Embodiment 1.

[0193] [Effects of Variation 4 of Implementation Method 1]

[0194] In the motor unit 1 of the modified example 4 of embodiment 1, the same effect as that of the motor unit 1 of embodiment 1 can be obtained.

[0195] In the motor unit 1 of the variation 4 of embodiment 1, the second auxiliary power supply diode 82b and the second auxiliary power supply resistor element 83b shown in FIG2 can be omitted. Therefore, the auxiliary circuit 50 can be miniaturized.

[0196] (Implementation Method 2)

[0197] Figure 9 is a circuit diagram showing the structure of the power conversion device 10E according to Embodiment 2. The structures of the auxiliary switch section 60 and auxiliary power supply section 80 of each of the n auxiliary circuits 50 in Embodiment 2 are different from those in Embodiment 1. The other structures of the power conversion device 10E in Embodiment 2 are the same as those of the power conversion device 10 in Embodiment 1.

[0198] [Auxiliary Switch Section]

[0199] In embodiment 2, in each of the n auxiliary circuits 50, the auxiliary switch section 60 has a first auxiliary switch element 61a, a second auxiliary switch element 61b, a first auxiliary diode 62a, and a second auxiliary diode 62b.

[0200] The first auxiliary switching element 61a and the second auxiliary switching element 61b are connected in series between the main connection point P2 and the resonant inductor 41. The second auxiliary switching element 61b is connected between the first auxiliary switching element 61a and the resonant inductor 41.

[0201] The first auxiliary diode 62a is connected between the auxiliary connection point P6 (the connection point between the first auxiliary switching element 61a and the second auxiliary switching element 61b) and the resonant inductor 41. The first auxiliary diode 62a is positively oriented from the auxiliary connection point P6 toward the resonant inductor 41. The second auxiliary diode 62b is connected between the main connection point P2 and the auxiliary connection point P6. The second auxiliary diode 62b is positively oriented from the auxiliary connection point P6 toward the main connection point P2.

[0202] Specifically, one end (collector or drain) of the first auxiliary switching element 61a is connected to the main connection point P2. One end (collector or drain) of the second auxiliary switching element 61b is connected to the resonant connection point P4. The other end (emitter or source) of the first auxiliary switching element 61a is connected to the other end (emitter or source) of the second auxiliary switching element 61b. The anode of the first auxiliary diode 62a is connected to the auxiliary connection point P6. The cathode of the first auxiliary diode 62a is connected to the resonant connection point P4. The anode of the second auxiliary diode 62b is connected to the auxiliary connection point P6. The cathode of the second auxiliary diode 62b is connected to the main connection point P2.

[0203] [Auxiliary Power Supply Section]

[0204] In Embodiment 2, each of the n auxiliary circuits 50 includes an auxiliary power supply unit 80 with an auxiliary power supply capacitor 81. The auxiliary power supply capacitor 81 is provided to generate the operating voltage of the first auxiliary driver 71a and the operating voltage of the second auxiliary driver 71b. The auxiliary power supply unit 80 is configured such that, when the first auxiliary switching element 61a and the second auxiliary switching element 61b are off and the high-side switching element SWH is off, and the low-side switching element SWL becomes on, current flows from the drive power supply unit 25 through the auxiliary power supply capacitor 81 to the main connection point P2.

[0205] In embodiment 2, an auxiliary power supply capacitor 81 is connected between the drive power supply unit 25 and the auxiliary connection point P6. The positive terminals of the first auxiliary driver 71a and the second auxiliary driver 71b are connected to one end of the auxiliary power supply capacitor 81, and a voltage generated in the auxiliary power supply capacitor 81 is applied. The negative terminals of the first auxiliary driver 71a and the second auxiliary driver 71b are connected to the auxiliary connection point P6, and a voltage at the auxiliary connection point P6 is applied.

[0206] [Charging action of the auxiliary power capacitor]

[0207] The charging operation of the auxiliary power supply capacitor 81 in the auxiliary circuit 50 of Embodiment 2 will be described. When the auxiliary switching element 61 (first auxiliary switching element 61a and second auxiliary switching element 61b) is off and the high-side switching element SWH is off, when the low-side switching element SWL is turned on, current flows from the drive power supply unit 25 to the auxiliary power supply unit 80 via the drive line L25.

[0208] The current flowing into the auxiliary power supply section 80 passes sequentially through the auxiliary power supply resistor element 83, the auxiliary power supply diode 82, and the auxiliary power supply capacitor 81 within the auxiliary power supply section 80. In the auxiliary switching section 60, it passes sequentially through the auxiliary connection point P6 and the second auxiliary diode 62b. Afterward, the current flowing into the auxiliary power supply section 80 passes sequentially through the main connection point P2 and the on-state low-side switching element SWL, flowing into the negative line L2. This forms a charging path for the auxiliary power supply capacitor 81, and the auxiliary power supply capacitor 81 is charged.

[0209] [Effects of Implementation Method 2]

[0210] In the motor unit 1 of embodiment 2, the same effect as that of the motor unit 1 of embodiment 1 can be obtained.

[0211] In the motor unit 1 of Embodiment 2, the third auxiliary diode 62c and the fourth auxiliary diode 62d shown in FIG2 can be omitted. As a result, the auxiliary circuit 50 can be miniaturized.

[0212] In the motor unit 1 of Embodiment 2, the second auxiliary power supply diode 82b and the second auxiliary power supply resistor element 83b shown in FIG2 can be omitted. As a result, the auxiliary circuit 50 can be miniaturized.

[0213] (Implementation Method 3)

[0214] Figure 10 is a circuit diagram showing the structure of the power conversion device 10F according to Embodiment 3. The structure and processing of the n auxiliary circuits 50 of the power conversion device 10F in Embodiment 3 are different from those of the power conversion device 10 in Embodiment 1. The other structures and processing of the power conversion device 10F in Embodiment 3 are the same as those of the power conversion device 10 in Embodiment 1.

[0215] [Auxiliary Switch Section]

[0216] In embodiment 3, in each of the n auxiliary circuits 50, the auxiliary switching unit 60 includes an auxiliary switching element 61, a first auxiliary diode 62a, a second auxiliary diode 62b, a third auxiliary diode 62c, and a fourth auxiliary diode 62d. The first auxiliary diode 62a, the second auxiliary diode 62b, the third auxiliary diode 62c, and the fourth auxiliary diode 62d constitute a diode bridge circuit.

[0217] The first auxiliary diode 62a is connected between the main connection point P2 and one end (emitter or source) of the auxiliary switching element 61. The first auxiliary diode 62a is positively oriented from the main connection point P2 toward the auxiliary switching element 61. The second auxiliary diode 62b is connected between the other end (collector or drain) of the auxiliary switching element 61 and the resonant inductor 41. The second auxiliary diode 62b is positively oriented from the auxiliary switching element 61 toward the resonant inductor 41.

[0218] The third auxiliary diode 62c is connected between the resonant inductor 41 and one end of the auxiliary switching element 61. The third auxiliary diode 62c is positively oriented in the direction from the resonant inductor 41 toward the auxiliary switching element 61. The fourth auxiliary diode 62d is connected between the other end of the auxiliary switching element 61 and the main connection point P2. The fourth auxiliary diode 62d is positively oriented in the direction from the auxiliary switching element 61 toward the main connection point.

[0219] Specifically, one end of the auxiliary switching element 61 is connected to the cathode of the first auxiliary diode 62a and the cathode of the third auxiliary diode 62c. The other end of the auxiliary switching element 61 is connected to the anode of the second auxiliary diode 62b and the anode of the fourth auxiliary diode 62d. The main connection point P2 is connected to the anode of the first auxiliary diode 62a and the cathode of the fourth auxiliary diode 62d. The resonant connection point P4 is connected to the anode of the third auxiliary diode 62c and the cathode of the second auxiliary diode 62b.

[0220] [Auxiliary Drive Section]

[0221] In Embodiment 2, in each of the n auxiliary circuits 50, the auxiliary drive unit 70 has an auxiliary driver 71 and an auxiliary output resistor element 72. The auxiliary driver 71 controls the switching on and off of the auxiliary switching element 61 in response to the control of the control unit 55. For example, in the operation of the power conversion device 10 shown in Figures 3 and 4, the auxiliary switching element 61 is controlled to be turned on during the period when the first auxiliary switching element 61a or the second auxiliary switching element 61b is turned on, and turned off during the period when the first auxiliary switching element 61a and the second auxiliary switching element 61b are turned off.

[0222] [Auxiliary Power Supply Section]

[0223] In embodiment 3, each of the n auxiliary circuits 50 includes an auxiliary power supply capacitor 81. The auxiliary power supply capacitor 81 is provided to generate the operating voltage of an auxiliary driver 71. The auxiliary power supply unit 80 is configured such that, when the first auxiliary switching element 61a and the second auxiliary switching element 61b are off and the high-side switching element SWH is off, and the low-side switching element SWL becomes on, current flows from the drive power supply unit 25 through the auxiliary power supply capacitor 81 to the main connection point P2.

[0224] In embodiment 3, the auxiliary power supply capacitor 81 is connected between the connection point of the other end of the auxiliary switching element 61 and the fourth auxiliary diode 62d, and the drive power supply unit 25. The positive terminal of the auxiliary driver 71 is connected to one end of the auxiliary power supply capacitor 81. A voltage generated in the auxiliary power supply capacitor 81 is applied to the positive terminal of the auxiliary driver 71. The negative terminal of the auxiliary driver 71 is connected to the connection point of the other end of the auxiliary switching element 61 and the fourth auxiliary diode 62d. A voltage at the connection point of the other end of the auxiliary switching element 61 and the fourth auxiliary diode 62d is applied to the negative terminal of the auxiliary driver 71.

[0225] [Charging action of the auxiliary power capacitor]

[0226] The charging operation of the auxiliary power supply capacitor 81 in the auxiliary circuit 50 of Embodiment 3 will be described. When the auxiliary switching element 61 (first auxiliary switching element 61a and second auxiliary switching element 61b) is off and the high-side switching element SWH is off, when the low-side switching element SWL is turned on, current flows from the drive power supply unit 25 to the auxiliary power supply unit 80 via the drive line L25.

[0227] The current flowing into the auxiliary power supply section 80 passes sequentially through the auxiliary power supply resistor element 83, the auxiliary power supply diode 82, and the auxiliary power supply capacitor 81, and then through the fourth auxiliary diode 62d in the auxiliary switch section 60. Afterward, the current flowing into the auxiliary power supply section 80 flows sequentially through the main connection point P2 and the on-state low-side switch element SWL to the negative line L2. This forms a charging path for the auxiliary power supply capacitor 81, and the auxiliary power supply capacitor 81 is charged.

[0228] [Effects of Implementation Method 3]

[0229] In the motor unit 1 of embodiment 3, the same effect as that of the motor unit 1 of embodiment 1 can be obtained.

[0230] In the motor unit 1 of embodiment 3, the second auxiliary switching element 61b shown in FIG2 can be omitted. As a result, the auxiliary circuit 50 can be miniaturized.

[0231] (Other implementation methods)

[0232] In the above explanation, the example of input voltage is "power supplied from power source 11, which is a DC power source". However, it is not limited to this. For example, the input voltage can also be a DC voltage obtained by rectifying the AC power supplied from power source 11, which is an AC power source, by a converter.

[0233] In the above description, the control unit 55 can be composed of a single processor or multiple processors.

[0234] The above embodiments can also be implemented by appropriate combinations. The above embodiments are essentially preferred embodiments and are not intended to limit the scope of the technology, its applications or uses disclosed herein.

[0235] Industrial availability

[0236] As explained above, the technology disclosed herein is useful as an auxiliary circuit, power conversion device, motor unit, etc.

[0237] Explanation of reference numerals in the attached figures

[0238] 1: Motor unit; 10, 10A, 10B, 10C, 10D, 10E, 10F: Power conversion device; 11: Power supply; 12: Motor; 20: Conversion section; 21: Branch circuit; SWH: High-side switching element; SWL: Low-side switching element; DH: High-side freewheeling diode; DL: Low-side freewheeling diode; P2: Main connection point; 25: Drive power supply section; 26: Control power supply section; 27: Drive diode; 30: Drive section; 31: High-side drive section; 32: High-side driver; 33: High-side power supply section C33: High-side power supply capacitor; D33: High-side power supply diode; R33: High-side power supply resistor; 34: High-side output resistor; 35: Low-side drive unit; 36: Low-side driver; 37: Low-side output resistor; 40: Resonant unit; 41: Resonant inductor; 42: Resonant power supply capacitor; 43: First resonant diode; 44: Second resonant diode; 45: Resonant capacitor; 50: Auxiliary circuit; 55: Control unit; 60: Auxiliary switching unit; 61: Auxiliary switching element; 61a: First Auxiliary switching element; 61b: Second auxiliary switching element; 62a: First auxiliary diode; 62b: Second auxiliary diode; 62c: Third auxiliary diode; 62d: Fourth auxiliary diode; P6: Auxiliary connection point; 70: Auxiliary driving unit; 71: Auxiliary driver; 71a: First auxiliary driver; 71b: Second auxiliary driver; 72: Auxiliary output resistor element; 72a: First auxiliary output resistor element; 72b: Second auxiliary output resistor element; 80: Auxiliary power supply unit; 81: Auxiliary power supply capacitor; 81a: First auxiliary power supply capacitor; 81b: Second auxiliary power supply capacitor; 82: Auxiliary power supply diode; 82a: First auxiliary power supply diode; 82b: Second auxiliary power supply diode; 82c: Third auxiliary power supply diode; 83: Auxiliary power supply resistor element; 83a: First auxiliary power supply resistor element; 83b: Second auxiliary power supply resistor element; 91: Resonant voltage sensor; 92: Power supply voltage sensor; L1: Positive line; L2: Negative line; L3: Output line; C1: Smoothing capacitor.

Claims

1. An auxiliary circuit for a power conversion device, the power conversion device having a conversion section, a drive power supply section, and a resonant section, for converting an input voltage applied between a positive line and a negative line into an output voltage, wherein, The auxiliary circuit includes an auxiliary switching section, an auxiliary driving section, and an auxiliary power supply section. The conversion section has a branch including a high-side switching element and a low-side switching element connected in series between the positive and negative lines. By switching the high-side and low-side switching elements on and off, the input voltage is converted into the output voltage. The driving power supply section generates a driving voltage based on the input voltage for controlling the on and off of the high-side and low-side switching elements. The resonant section includes a resonant inductor and a resonant capacitor. The resonant capacitor is connected to the connection point between the high-side and low-side switching elements, i.e., the main connection point. The auxiliary switching section has an auxiliary switching element disposed between the main connection point and the resonant inductor. The auxiliary switching section is configured such that when the auxiliary switching element is turned on, current flows between the main connection point and the resonant inductor. The auxiliary driving section has an auxiliary driver for controlling the on and off of the auxiliary switching element. The auxiliary power supply section has an auxiliary power supply capacitor for generating the operating voltage of the auxiliary driver. The auxiliary power supply section is configured such that when the low-side switching element is turned on while the auxiliary switching element is turned off and the high-side switching element is off, current flows from the driving power supply section through the auxiliary power supply capacitor to the main connection point.

2. The auxiliary circuit according to claim 1, wherein, The auxiliary switching section has a first auxiliary switching element and a second auxiliary switching element disposed between the main connection point and the resonant inductor. The auxiliary switching section is configured such that when the first auxiliary switching element is turned on and the second auxiliary switching element is turned off, current flows from the main connection point to the resonant inductor, and when the first auxiliary switching element is turned off and the second auxiliary switching element is turned on, current flows from the resonant inductor to the main connection point. The auxiliary driving section has: a first auxiliary driver that controls the turning on and off of the first auxiliary switching element; and a second auxiliary driver that controls the turning on and off of the second auxiliary switching element. The auxiliary power supply section has: a first auxiliary power supply capacitor that generates the operating voltage of the first auxiliary driver. And a second auxiliary power supply capacitor, which is used to generate the operating voltage of the second auxiliary driver, wherein the auxiliary switching element is the first auxiliary switching element, the auxiliary driver is the first auxiliary driver, and the auxiliary power supply capacitor is the first auxiliary power supply capacitor.

3. The auxiliary circuit according to claim 2, wherein, The auxiliary power supply is configured such that, when the low-side switch element becomes on while the first auxiliary switch element and the second auxiliary switch element are off and the high-side switch element is off, current flows from the drive power supply to the main connection point via the first auxiliary power supply capacitor and the second auxiliary power supply capacitor.

4. The auxiliary circuit according to claim 3, wherein, The first auxiliary switching element and the second auxiliary switching element are connected in parallel between the main connection point and the resonant inductor. The auxiliary switching section includes: a first auxiliary diode connected between the first auxiliary switching element and the resonant inductor, with the direction from the first auxiliary switching element toward the resonant inductor being positive; a second auxiliary diode connected in parallel with the first auxiliary switching element between the main connection point and the first auxiliary diode, with the direction from the first auxiliary diode toward the main connection point being positive; and a third auxiliary diode connected between the second auxiliary switching element and the resonant inductor, with the direction from the resonant inductor toward the second auxiliary switching element being positive. A fourth auxiliary diode is connected in parallel with the second auxiliary switching element between the main connection point and the third auxiliary diode, with the direction from the main connection point toward the third auxiliary diode being positive. The first auxiliary power supply capacitor is connected between the connection point of the first auxiliary switching element and the first auxiliary diode and the driving power supply unit. The second auxiliary power supply capacitor is connected between the main connection point and the driving power supply unit.

5. The auxiliary circuit according to claim 4, wherein, The auxiliary power supply unit includes: a first auxiliary power supply diode connected between the driving power supply unit and the first auxiliary power supply capacitor, with the direction from the driving power supply unit toward the first auxiliary power supply capacitor being positive; and a first auxiliary power supply resistor element connected in series with the first auxiliary power supply diode between the driving power supply unit and the first auxiliary power supply capacitor. A second auxiliary power supply diode is connected between the driving power supply unit and the second auxiliary power supply capacitor, with the direction from the driving power supply unit toward the second auxiliary power supply capacitor being positive; and a second auxiliary power supply resistor element is connected in series with the second auxiliary power supply diode between the driving power supply unit and the second auxiliary power supply capacitor.

6. The auxiliary circuit according to claim 5, wherein, The auxiliary power supply unit has a third auxiliary power diode, which is positively oriented from one end connected to the drive power supply unit toward the other end. The first auxiliary power diode and the first auxiliary power resistor are connected between one end of the third auxiliary power diode and the first auxiliary power capacitor. The second auxiliary power diode and the second auxiliary power resistor are connected between the other end of the third auxiliary power diode and the second auxiliary power capacitor.

7. The auxiliary circuit according to claim 2, wherein, The switching on and off of the high-side switching element is controlled by a high-side drive unit, which includes: a high-side driver that controls the switching on and off of the high-side switching element; and a high-side power supply unit having a high-side power supply capacitor for generating the operating voltage of the high-side driver. The high-side power supply unit is configured such that when the low-side switching element becomes on while the high-side switching element is off, current flows from the drive power supply unit to the main connection point via the high-side power supply capacitor. The auxiliary power supply unit is configured such that a portion of the current flowing from the drive power supply unit to the high-side power supply capacitor in the high-side power supply unit flows to the main connection point via a second auxiliary power supply capacitor.

8. The auxiliary circuit according to claim 1, wherein, The auxiliary switching section has a first auxiliary switching element and a second auxiliary switching element disposed between the main connection point and the resonant inductor. The auxiliary switching section is configured such that when the first auxiliary switching element is turned on and the second auxiliary switching element is turned off, current flows from the main connection point to the resonant inductor, and when the first auxiliary switching element is turned off and the second auxiliary switching element is turned on, current flows from the resonant inductor to the main connection point. The auxiliary driving section has: a first auxiliary driver that controls the turning on and off of the first auxiliary switching element; and a second auxiliary driver that controls the turning on and off of the second auxiliary switching element. The auxiliary power supply capacitor is configured to generate the operating voltage of the first auxiliary driver and the operating voltage of the second auxiliary driver. The auxiliary switching element is the first auxiliary switching element, and the auxiliary driver is the first auxiliary driver.

9. The auxiliary circuit according to claim 8, wherein, The first auxiliary switching element and the second auxiliary switching element are connected in series between the main connection point and the resonant inductor. The second auxiliary switching element is connected between the first auxiliary switching element and the resonant inductor. The auxiliary switching part includes: a first auxiliary diode connected between the auxiliary connection point and the resonant inductor, with the direction from the auxiliary connection point toward the resonant inductor being positive, wherein the auxiliary connection point is the connection point of the first auxiliary switching element and the second auxiliary switching element; and a second auxiliary diode connected between the main connection point and the auxiliary connection point, with the direction from the auxiliary connection point toward the main connection point being positive. The auxiliary power supply capacitor is connected between the driving power supply part and the auxiliary connection point.

10. The auxiliary circuit according to claim 1, wherein, The auxiliary switching section includes: a first auxiliary diode connected between the main connection point and one end of the auxiliary switching element, with the direction from the main connection point toward the auxiliary switching element being positive; a second auxiliary diode connected between the other end of the auxiliary switching element and the resonant inductor, with the direction from the auxiliary switching element toward the resonant inductor being positive; and a third auxiliary diode connected between the resonant inductor and one end of the auxiliary switching element, with the direction from the resonant inductor toward the auxiliary switching element being positive. And a fourth auxiliary diode, which is connected between the other end of the auxiliary switching element and the main connection point, with the direction from the auxiliary switching element toward the main connection point being positive, and the auxiliary power supply capacitor is connected between the other end of the auxiliary switching element, the connection point of the fourth auxiliary diode, and the drive power supply unit.

11. A power conversion device comprising: n auxiliary circuits, wherein the n auxiliary circuits are respectively the auxiliary circuits according to any one of claims 1 to 10; the conversion unit; the drive power supply unit; and the resonant unit, wherein, The n is an integer greater than or equal to 1, the transformation unit has n branches, the n branches are respectively the branches, and the resonant unit has: the resonant inductor; And n resonant capacitors, each corresponding to one of the resonant capacitors, the n resonant capacitors corresponding to the n branches, and the n auxiliary circuits corresponding to the n branches respectively.

12. A motor unit comprising: a motor; and a power conversion device according to claim 11, which drives the motor.

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