Converter device and motor drive device equipped with the same

Abstract

To provide a converter device capable of suppressing surge current flowing in a switching element and an electric element connected to the switching element and to provide a motor drive device including the converter device.SOLUTION: A converter device includes: a bridge rectifier circuit having a plurality of rectifier elements D1 to D4 for rectifying power supplied from an AC power supply; a plurality of capacitors C1 and C2 which are connected in parallel to an output side of the bridge rectifier circuit and are mutually connected in series; a switching element SW1 in which a first terminal is connected to a middle point P1 between the plurality of rectifier elements connected in series and a second terminal is connected to a middle point P2 between the plurality of capacitors; and a control unit 24 for controlling a state of the switching element and switching low voltage control in which current is supplied to all the capacitors from one direction and high voltage control in which the capacitor charged at every half period of the AC power supply is switched. The control unit turns on the switching element at switching timing in which a difference of voltages at both ends of the switching element becomes approximately zero.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a converter device and a motor drive device including the converter device. [Background technology]

[0002] Conventionally, rectification control and boost control using a bridge circuit formed by power transistors have been widely used.

[0003] For example, Patent Document 1 discloses the configuration of an inverter device that is equipped with a bridge circuit made up of diodes and capacitors and that supplies power from an AC power supply. This inverter device converts AC voltage output from the AC power supply into DC voltage, and controls the on / off of a relay that switches the conduction state of the bridge circuit according to the frequency of the converted DC voltage, thereby switching between two rectification modes: a bridge rectification mode and a double voltage rectification mode. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 112575 / 1983 Summary of the Invention [Problem to be solved by the invention]

[0005] In the bridge circuit disclosed in Patent Document 1, when the relay is switched on / off while the bridge circuit is operating, if there is a voltage between both terminals of the relay contacts, a surge current flows through the relay and the electrical element connected to the relay when the relay is turned on. The surge current flowing through the electrical element connected to the relay increases in proportion to the magnitude of the voltage between both terminals of the relay contacts. Furthermore, if the surge current is excessive, it will reduce the durability and lifespan of the relay and the electrical element connected to the relay, causing a malfunction.

[0006] An object of the present disclosure is to provide a converter device that can suppress surge currents that flow through switching elements and electrical elements connected to the switching elements, and a motor drive device that includes the converter device. [Means for solving the problem]

[0007] A converter device in some embodiments of the present disclosure includes: a bridge rectifier circuit having a plurality of rectifier elements that rectify AC power supplied from an AC power supply; a plurality of capacitors connected in parallel to an output side of the bridge rectifier circuit and connected in series with each other; a switching element having a first terminal connected to a midpoint between the plurality of series-connected rectifier elements and a second terminal connected to a midpoint between the plurality of capacitors; and a control unit that controls on / off of the switching element to switch between low-voltage control in which current is supplied in one direction to all of the capacitors and high-voltage control in which the capacitors to be charged are switched every half cycle of the AC power supply, and the control unit turns on the switching element at a switching timing when a difference in voltage across the switching element becomes zero.

[0008] A motor drive device in some embodiments of the present disclosure includes the converter device described above. [Effects of the Invention]

[0009] According to the present disclosure, it is possible to suppress surge currents flowing through switching elements and electric elements connected to the switching elements. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a diagram illustrating a configuration of a motor drive device according to an embodiment of the present disclosure. [Figure 2] FIG. 2 is a diagram illustrating a configuration of a control unit according to an embodiment of the present disclosure. [Figure 3] 3A to 3C are diagrams illustrating waveforms showing changes in current and voltage during various controls in the converter device. [Figure 4]FIG. 10 is a comparative diagram showing the relationship between the timing of switching the connection state of the relay and the surge current generated at the time of switching. [Figure 5] 2 is a diagram illustrating an example of a converter device in which a resistor and a capacitor are provided as a filter in the converter device of FIG. 1. FIG. [Figure 6] 6 is a diagram showing the simulation results of the input voltage and the difference in voltage across the relay when the inductance is 1 mH and the capacitance is 2000 μF in the converter device of FIG. 5. FIG. [Figure 7] 6 is a diagram showing the results of a simulation of the input voltage and the difference in voltage across the relay when the inductance is 10 mH and the capacitance is 2000 μF in the converter device of FIG. 5. FIG. [Figure 8] 6 is a diagram showing the simulation results of the input voltage and the difference in voltage across the relay when the inductance is 1 mH and the capacitance is 3000 μF in the converter device of FIG. 5. [Figure 9] 2 is a diagram illustrating an example of the converter device in which detection resistors for detecting voltages at both terminals of a relay are provided in the converter device of FIG. 1. FIG. [Figure 10] 2 is a diagram illustrating an example of the converter device of FIG. 1 in which a detection resistor for detecting a difference in voltage across a relay is provided. DETAILED DESCRIPTION OF THE INVENTION

[0011] [First embodiment] A converter device according to an embodiment of the present disclosure will be described below with reference to the drawings. Fig. 1 is a diagram showing the configuration of a motor drive device according to an embodiment of the present disclosure. As shown in Fig. 1, motor drive device 1 includes an AC power supply 2, a converter device 10, an inverter device 40, and a motor 50. Converter device 10 also includes a reactor L1, bridge-connected diodes (rectifier elements) D1 to D4, capacitors C1 and C2, a relay (switching element) SW1, a relay drive power supply device 3, an input voltage detection unit 22, a zero-cross detection unit 23, and a control unit 24.

[0012] The converter device 10 is a device that converts AC power supplied from an AC power source 2 into DC power. The DC power generated by the converter device 10 is converted into three-phase AC power by, for example, an inverter device 40, and used to drive a motor 50. The motor 50 is driven in response to the three-phase AC power supplied from the inverter device 40, and is, for example, a compressor motor used in an air conditioner.

[0013] The AC power supply 2 is, for example, a single-phase AC power supply, and supplies an input voltage and an input current to the converter device 10.

[0014] The bridge rectifier circuit 5 included in the converter device 10 includes a plurality of diodes D1 to D4 that rectify AC power supplied from the AC power supply 2. The diodes D1 to D4 are bridge-connected, and which diode rectifies the AC power supplied from the AC power supply 2 varies depending on the polarity of the AC power supply 2.

[0015] For example, when AC power is supplied from the positive electrode of the AC power supply 2, the AC power is rectified by passing through diodes D1 and D4. When AC power is supplied from the negative electrode of the AC power supply 2, the AC power is rectified by passing through diodes D3 and D2.

[0016] The reactor L1 is provided between the AC power supply 2 and the bridge rectifier circuit 5. The reactor L1 stores the power supplied from the AC power supply 2 as energy and then releases this energy to boost the voltage. The capacitor C1 smoothes the voltage rectified through the diode D1 or the diode D3, respectively, to generate a DC voltage.

[0017] The capacitors C1 and C2 are connected in parallel to the output side of the bridge rectifier circuit 5 and are also connected in series to each other. The positive electrode of the capacitor C1 is connected to the cathodes of the diodes D1 and D3, and the negative electrode is connected to the positive electrode of the capacitor C2. The positive electrode of the capacitor C2 is connected to the negative electrode of the capacitor C1, and the negative electrode is connected to the anodes of the diodes D2 and D4. Here, capacitors C1 and C2 are capacitors that smooth the DC power output from bridge rectifier circuit 5. Capacitors C1 and C2 suppress fluctuations in the voltage value of the DC voltage. Capacitors C1 and C2 are, for example, electrolytic capacitors.

[0018] The relay SW1 has a first terminal connected to a midpoint P1 between the series-connected diodes D3 and D4, and a second terminal connected to a midpoint P2 between the capacitors C1 and C2. The relay SW1 is switched on / off by power supply from the relay driving power supply device 3. The relay driving power supply device 3 controls whether or not to supply power to the relay SW1 based on a command from the control unit 24.

[0019] As will be described later, the converter device 10 switches between low-voltage control, in which current is supplied to all capacitors C1 and C2 in one direction, and high-voltage control, in which the capacitor to be charged is switched every half cycle of the AC voltage, by the control unit 24 controlling the on / off of the relay SW1.

[0020] Low voltage control is executed when the control unit 24 controls the relay SW1 to be turned off. In the low voltage control, when power is supplied from the positive electrode side of the AC power supply 2, a current rectified by the diode D1 flows to the capacitors C1 and C2, thereby charging the capacitors C1 and C2, and when power is supplied from the negative electrode side of the AC power supply 2, a current rectified by the diode D3 flows to the capacitors C1 and C2, thereby charging the capacitors C1 and C2.

[0021] When the control unit 24 controls the relay SW1 to be turned on, high voltage control is executed. In the high voltage control, the capacitor C1 is charged by the current flowing through the diode D1 during the half cycle in which power is supplied from the positive electrode side of the AC power supply 2, and the capacitor C2 is charged by the current flowing through the diode D2 during the half cycle in which power is supplied from the negative electrode side of the AC power supply 2. As a result, a DC voltage twice the input value Va of the AC voltage is generated between the terminals of the capacitors C1 and C2, and this output power is supplied to the inverter device.

[0022] The converter device 10 also includes an input voltage detection unit 22 that detects an AC voltage as an input voltage. In addition, a current sensor (not shown) for detecting a current between the AC power supply 2 and the bridge rectifier circuit 5 may also be provided.

[0023] The input voltage detection unit 22 detects the voltage value of the input voltage supplied from the AC power supply 2 to the bridge rectifier circuit 5 at intervals that are sufficiently shorter than the period of the AC voltage output by the AC power supply 2. For example, the input voltage detection unit 22 includes a voltage sensor provided between the AC power supply 2 and the bridge rectifier circuit 5, and detects the voltage value of the input voltage (an example of a physical quantity related to the input voltage) read by the voltage sensor. The input voltage detection unit 22 outputs the detected voltage value of the input voltage to the zero-cross detection unit 23 .

[0024] Zero cross detection section ( No. 2 The zero-cross detection unit 23 has a function of determining whether the voltage value of the AC power supply 2 detected by the input voltage detection unit 22 has switched between positive and negative (whether the zero-cross point has been reached). The zero-cross detection unit 23 also has a function of detecting the phase of the voltage of the AC power supply 2. The zero-cross detection unit 23 is a polarity detection unit that detects the polarity of the voltage of the AC power supply 2, and outputs a zero-cross signal to the control unit 24. For example, the zero-cross detection unit 23 outputs a signal of "1" to the control unit 24 while the voltage of the AC power supply 2 is positive, and outputs a signal of "0" to the control unit 24 while the voltage of the AC power supply 2 is negative.

[0025] The zero-cross detector 23 may detect a phase other than the zero-cross point related to the voltage of the AC power supply 2 and output a phase detection signal to the controller 24. In this case, the zero-cross detector 23 outputs a signal of "1" or "0" to the controller 24 based on, for example, the detected phase and a preset phase reference value. Furthermore, the converter device 10 may include a phase detector having such a function independent of the zero-cross detector 23. In the following description of the embodiment, the zero-cross detector 23 outputs a zero-cross signal to the controller 24 as an example.

[0026] The control unit 24 is composed of, for example, a CPU (Central Processing Unit), RAM (Random Access Memory), ROM (Read Only Memory), and a computer-readable storage medium. A series of processes for realizing various functions is stored in a storage medium, for example, in the form of a program. The CPU reads this program into RAM and executes information processing and arithmetic operations to realize various functions. The program may be pre-installed in a ROM or other storage medium, provided in a state stored in a computer-readable storage medium, or distributed via wired or wireless communication means. Examples of computer-readable storage media include magnetic disks, magneto-optical disks, CD-ROMs, DVD-ROMs, and semiconductor memories.

[0027] The control unit 24 switches between low voltage control and high voltage control by switching relay SW1 on and off based on the motor rotation speed, which is the rotation speed of the motor 50. For example, when the motor rotation speed is equal to or less than a predetermined threshold, the control unit 24 turns relay SW1 off to perform low voltage control, and when the motor rotation speed exceeds the predetermined threshold, the control unit 24 turns relay SW1 on to perform high voltage control. In switching relay SW1, the control unit 24 switches relay SW1 from the off state to the on state at a timing when the difference in voltage across relay SW1 becomes approximately zero. In this embodiment, the zero-cross timing (zero-cross point) is used as the timing when the voltage difference between both ends of relay SW1 becomes approximately zero. That is, the control unit 24 receives a signal from the zero-cross detection unit 23 and switches on relay SW1 at the zero-cross timing when the input voltage becomes zero.

[0028] 2 is a functional configuration diagram showing an example of functions included in the control unit 24 according to an embodiment of the present disclosure. As shown in FIG. 2, the control unit 24 includes a timing identification unit 241, a control signal generation unit 243, and a storage unit 244.

[0029] The timing specifying unit 241 specifies the switching timing. Specifically, the timing specifying unit 241 acquires a zero-cross signal from the zero-cross detection unit 23, and specifies the switching timing for switching the relay SW1 based on the acquired zero-cross signal. In this embodiment, the timing specifying unit 241 specifies the zero-cross timing based on the zero-cross signal, and outputs the specified zero-cross timing to the control signal generation unit 243 as the switching timing.

[0030] The control signal generating unit 243 generates a control signal for switching the relay SW1 on / off at the switching timing acquired from the timing identifying unit 241, and outputs the generated control signal to the relay driving power supply device 3. As a result, the relay driving power supply device 3 is driven based on the control signal, and the contact of the relay SW1 is closed, switching it on.

[0031] In this way, the control unit 24 switches on the relay SW1 at the zero-cross timing based on the output signal of the zero-cross detection unit, thereby making it possible to suppress the occurrence of surge current across the relay SW1.

[0032] Figure 3 shows the current and voltage waveforms when relay SW1 is switched from the OFF state to the ON state at the zero-cross timing. In Figure 3, the horizontal axis represents time, and the vertical axis represents current in the upper diagram and voltage in the lower diagram. The solid line represents current I1 flowing through capacitor C1 in Figure 1, and the dashed line represents current I2 flowing through capacitor C2 in Figure 1. The dashed-dotted line represents voltage Vac in Figure 1, and the dashed-double-dotted line represents voltage Vn1 in Figure 1. The dotted line that crosses the upper and lower diagrams represents zero-cross timing ZC.

[0033] As shown in Fig. 3, the connection state of relay SW1 is off until zero-cross timing ZC, and converter device 10 executes low-voltage control. Then, at zero-cross timing ZC, when voltage Vac becomes zero, the connection state of relay SW1 is switched on, and converter device 10 executes high-voltage control after zero-cross timing ZC. Also, from Fig. 3, it can be seen that, as high-voltage control is executed, the values ​​of current I1, current I2, and voltage Vn1 increase compared to before high-voltage control was executed (before zero-cross timing ZC). In this way, converter device 10 shown in Fig. 1 can execute both low-voltage control and high-voltage control by switching the connection state of relay SW1.

[0034] Second Embodiment Next, the determination of the switching timing of the relay SW1 according to the second embodiment of the present disclosure will be described. In the first embodiment described above, the zero-cross timing was used as the timing at which the voltage difference between both ends of relay SW1 becomes zero. However, when the inventors actually performed tests and simulations, they found that there was a time difference between the zero-cross timing of the input voltage and the timing at which the voltage difference between both ends of relay SW1 actually becomes zero, which resulted in the generation of a certain amount of surge current. From these results, it was discovered that there is a more optimal timing for switching relay SW1. Therefore, in this embodiment, simulations or tests are performed in advance to identify a range of phase shift from the zero-cross point where the surge current is equal to or less than a predetermined value, and a phase shift θ for determining the switching timing of relay SW1 is determined within the identified range of phase shift.

[0035] Figure 4 is a comparative diagram showing the relationship between the timing of switching the connection state of the relay and the surge current that occurs when switching. Each of Figures 4(a) to 4(e) shows a range equivalent to range R in Figure 3, and the switching timing of relay SW1 is different. In Figure 4, the solid line shows the transition of current I1 flowing through capacitor C1 in Figure 1. The dashed line shows the transition of current I2 flowing through capacitor C2 in Figure 1. In addition, in each figure, the solid line parallel to the vertical axis indicates the occurrence of a surge current.

[0036] First, Figure 4(c) shows the surge current when the connection state of relay SW1 is switched on at the zero-cross timing. As can be seen from Figure 4(c), a surge current is generated even when relay SW1 is switched from off to on at the zero-cross timing. In other words, it can be seen that the voltage difference between both ends of relay SW1 at the zero-cross timing is not necessarily zero. This is because resonance occurs in the voltage due to the parasitic capacitance of reactor L1 and capacitors C1 and C2 provided in converter device 10 and the dead band of Vf of diodes D1 to D4.

[0037] The examples in Figures 4(a) and 4(b) show whether or not a surge current occurs when the switching timing of relay SW1 is made earlier than the zero-cross timing, while the examples in Figures 4(d) and 4(e) show whether or not a surge current occurs when the switching timing of relay SW1 is made later than the zero-cross timing. Comparing the figures, in the example of FIG. 4(a), where the switching timing of relay SW1 is advanced, a larger surge current is generated than in the example of FIG. 4(c). Similarly, in the examples of FIG. 4(d) and FIG. 4(e), where the switching timing of relay SW1 is delayed, a larger surge current is generated than in the example of FIG. 4(c). On the other hand, in the example of FIG. 4(b), where the switching timing of relay SW1 is advanced, no surge current is generated. From this, it can be inferred that the difference in voltage across relay SW1 becomes zero when the switching timing of relay SW1 is advanced by a predetermined phase from the zero-cross timing.

[0038] (Setting the switching timing based on the results of a simulation conducted in advance) A method for setting the switching timing of the relay SW1 so that the difference in voltage between both ends of the relay SW1 becomes approximately zero will be described below based on the results of a simulation performed in advance.

[0039] In this embodiment, the phase shift θ obtained from a simulation result or test result performed in advance is stored in the storage unit 244. Then, the timing specifying unit 241 specifies the switching timing, which is the timing at which the difference in voltage between both ends of the relay SW1 becomes zero, based on the zero-cross timing of the input voltage and the phase shift θ stored in the storage unit 244.

[0040] In this embodiment, a command to change the rotation speed of the motor 50 equipped in the compressor is input to the control unit 24, and if the rotation speed of the rotation speed change command is high, the control unit 24 determines that processing is required to switch from low pressure control to high pressure control.

[0041] Next, when it is determined to switch from low voltage control to high voltage control, the timing determination unit 241 determines the switching timing based on the input zero cross signal and the phase shift amount θ stored in the memory unit 244.

[0042] Then, the control signal generating unit 243 outputs a control signal for switching the relay SW1 at the switching timing identified by the timing identifying unit 241, and switches the relay SW1 from off to on.

[0043] An example of a simulation for determining the phase shift amount θ for correcting the zero-cross timing of the input voltage will be described below. Figure 5 shows a circuit model from a simulation conducted in advance. Note that the circuit model in Figure 5 adds resistors R2 and R3 and capacitors C3 and C4 to the circuit in Figure 1. Figure 6 shows the simulation results of the input voltage and the voltage difference across relay SW1 when the inductance is 1 mH and the capacitance is 2000 μF, using the circuit model in Figure 5. In Figure 6, the upper graph shows the input voltage waveform, and the lower graph shows the waveform of the voltage difference across the relay.

[0044] 6, the timing at which the voltage becomes zero does not match in both figures. This is because resonance occurs in the voltage difference across the relay due to the influence of the inductance of reactor L1, the parasitic capacitance of capacitors C1 and C2, the dead band of Vf of diodes D1 to D4, and other factors included in converter device 10. Therefore, when determining the timing at which relay SW1 is switched on to execute control switching of converter device 13, it is necessary to consider the time difference (or phase difference) between the zero-cross timing of the input voltage and the zero-cross timing of the voltage difference across relay SW1.

[0045] Here, as shown in FIG. 6, simulation results for an inductance of 1 mH and a capacitance of 2000 μF confirmed that the timing at which the voltage difference across relay SW1 becomes substantially zero is approximately 1 msec earlier than the zero-cross timing of the input voltage. Furthermore, this simulation result is converted to a phase of approximately 27 degrees. Based on this simulation result, control signal generator 243 sets the switching timing of relay SW1 to be approximately 1 msec (approximately 27 degrees) earlier than the zero-cross timing of the input voltage. Based on this switching timing, control signal generator 243 then outputs a control signal to relay drive power supply device 3 to switch the connection state of relay SW1 to ON.

[0046] In this way, the control unit 24 sets the switching timing based on the simulation results under the same conditions as the current control conditions stored in the storage unit 244, and switches the connection state of the relay SW1 based on the switching timing, thereby making it possible to avoid the occurrence of surge current.

[0047] 7 shows the simulation results of the input voltage and the voltage difference across the relay when the inductance is 10 mH and the capacitance is 2000 μF in the converter device of FIG. 5. In FIG. 7, the upper graph shows the input voltage waveform, and the lower graph shows the waveform of the voltage difference across relay SW1. This embodiment is the same as the example shown in FIG. 6 except for the inductance value.

[0048] As shown in Figure 7, simulation results for an inductance of 10 mH and a capacitance of 2000 μF confirmed that the timing at which the voltage difference between both ends of relay SW1 becomes substantially zero is approximately 1 msec earlier than the zero-cross timing of the input voltage. Furthermore, this simulation result is converted to a phase of approximately 27 degrees. Based on this simulation result, the control signal generator 243 actually sets the switching timing of relay SW1 to be approximately 1 msec (approximately 27 degrees) earlier than the zero-cross timing of the input voltage.

[0049] Furthermore, when the results of this simulation are compared with the results of a simulation based on the conditions in Figure 6, it is clear that an increase in inductance does not have a significant effect on the time difference between the zero-crossing timing of the input voltage and the switching timing at which the difference in voltage across relay SW1 is approximately zero.

[0050] Fig. 8 shows the simulation results of the input voltage and the voltage difference across the relay when the inductance is 1 mH and the capacitance is 3000 μF in the converter device of Fig. 5. In Fig. 8, the upper diagram shows the input voltage waveform, and the lower diagram shows the waveform of the voltage difference across relay SW1. Note that this embodiment is the same as the example shown in Fig. 9 except for the capacitance value.

[0051] As shown in Fig. 8, simulation results for an inductance of 10 mH and a capacitance of 3000 µF confirmed that the timing at which the voltage difference between both ends of relay SW1 becomes substantially zero is approximately 1.5 msec earlier than the zero-crossing timing of the input voltage. This result is equivalent to approximately 40 degrees in phase. Based on this simulation result, the control signal generator 243 sets the switching timing, which is the timing at which the connection state of relay SW1 is actually switched, to approximately 1.5 msec (approximately 40 degrees) earlier than the zero-crossing timing of the input voltage.

[0052] Furthermore, when the results of this simulation are compared with the results of a simulation based on the conditions in Figure 6, it is clear that an increase in capacitance affects the time difference between the zero-cross timing of the input voltage and the switching timing at which the difference in voltage across relay SW1 is approximately zero.

[0053] Based on the above simulation results, and taking into consideration the influence of the electric elements provided in each converter device, the zero cross timing is shifted by the phase shift amount θ as the switching timing, thereby making it possible to more reliably avoid the occurrence of surge current when switching relay SW1.

[0054] 6 to 8, the switching timing is, for example, a timing that advances the phase of the input voltage by about 10 to 50 degrees, including a margin, relative to the zero-cross timing of the input voltage, and more preferably, a timing that advances the phase by about 27 to 40 degrees relative to the zero-cross timing of the input voltage. Note that these ranges are just examples based on this simulation, and may be changed as appropriate depending on the electrical characteristics of the converter device.

[0055] From the above simulation results, the phase shift θ to be applied to the zero-cross timing has a numerical range. That is, the phase shift θ may be any value within a numerical range that can prevent the occurrence of a surge current. Therefore, the control unit 24 may set a numerical range for the phase shift θ that can be set. Alternatively, multiple allowable ranges may be set that are gradually reduced within a predetermined numerical range that includes the phase shift θ. By gradually setting the allowable range for the phase shift θ in this manner, the phase shift θ can be flexibly set in accordance with the control conditions of the converter device.

[0056] (Setting the timing of switching based on the results of tests conducted in advance) In the above-described method, the phase shift amount θ is calculated based on the results of a simulation performed in advance, and the switching timing is set. However, the control unit 24 may calculate the phase shift amount θ based on the results of a test performed in advance, instead of the simulation results, and set the switching timing. In this case, the storage unit 244 stores the phase shift amount θ calculated based on the results of a test performed in advance, and the timing specifying unit 241 specifies the switching timing based on the phase shift amount θ stored in the storage unit. Note that other processing performed by the control unit 24 is the same as when using the simulation results.

[0057] Third Embodiment (Regarding setting the switching timing by voltage monitoring) In the above embodiment, a method for determining the switching timing by shifting the phase of the zero-cross timing of the input voltage has been described. However, as another method, the switching timing may be determined by monitoring the difference in voltage across relay SW1. A method for setting the switching timing for switching the connection state of relay SW1 by monitoring the voltage across both terminals of relay SW1 will be described below. FIG. 9 is a diagram illustrating an example of the converter device in which detection resistors for detecting voltages at both terminals of the relay are provided in the converter device of FIG. In the configuration of FIG. 9, both terminals of the relay SW1 are connected to voltage dividing resistor groups ( No. 1 Detectors Rd1 and Rd2 are connected to the resistors Rd1 and Rd2, respectively. The voltage at the midpoint P3 of the resistor group Rd1 and the voltage at the midpoint P4 of the resistor group Rd2 are both input to the control unit 24. The control unit 24 may be provided with a microcomputer AD port so that the input voltage amount can be A / D converted.

[0058] 9 is mounted on an air conditioner, a rotation speed change command for the motor 50 of the compressor is input to the control unit 24, and if the rotation speed of the rotation speed change command is high, the control unit 24 switches the control of the converter device 11 from low-voltage control to high-voltage control. In this case, the control unit 24 first determines whether or not it is possible to switch from low-voltage control to high-voltage control based on both the input voltage at midpoint P3 of the voltage-dividing resistor group Rd1 and the voltage at midpoint P4 of the voltage-dividing resistor group Rd2.

[0059] Next, when the control unit 24 determines that the control can be switched from low voltage control to high voltage control, the control signal generation unit 243 included in the control unit 24 determines the timing when the voltage at midpoint P3 and the voltage at midpoint P4 match, that is, the timing when the difference in voltage across relay SW1 is zero, as the switching timing. Then, based on the switching timing, the control signal generation unit 243 outputs a control signal to the relay drive power supply device 3 to switch the connection state of relay SW1 to ON.

[0060] In this way, the control unit 24 sets the switching timing based on the voltages at both terminals of the relay SW1, and switches the connection state of the relay SW1 to on based on the switching timing, thereby avoiding the occurrence of surge current in the converter device 11.

[0061] FIG. 10 is a diagram illustrating an example of the converter device in which a detection resistor for detecting a difference in voltage across the relay is provided in the converter device of FIG. 10, a voltage dividing resistor group (detection unit) Rd3 including a plurality of resistors, which are detection resistors for detecting voltage, is connected in parallel to both terminals of the relay SW1. The voltage at a midpoint P5 of the voltage dividing resistor group Rd3 is input to the control unit 24. The control unit 24 may be provided with a microcomputer AD port so as to be able to perform A / D conversion of the input voltage amount.

[0062] 10 is installed in an air conditioner, the controller 24 receives a command to change the rotation speed of the motor 50 of the compressor, and if the rotation speed is high, the controller 24 switches the control of the converter device 12 from low-voltage control to high-voltage control. In this case, the controller 24 first determines whether or not switching from low-voltage control to high-voltage control is possible based on the input voltage at midpoint P5 of the voltage-dividing resistor group Rd3. Specifically, the controller 24 determines whether or not a surge current will flow when relay SW1 is switched on.

[0063] Next, when the control unit 24 determines that a change from low voltage control to high voltage control is possible, the control signal generation unit 243 included in the control unit 24 determines the timing when the voltage at the midpoint P5 is zero, that is, the timing when the difference in voltage across the relay SW1 is zero, as the switching timing. Then, based on the switching timing, the control signal generation unit 243 outputs a control signal to the relay drive power supply device 3 to switch the connection state of the relay SW1 to ON.

[0064] In this way, the control unit 24 sets the switching timing based on the voltage at the midpoint P5 between both terminals of the relay SW1, and switches the connection state of the relay SW1 to on based on the switching timing, thereby avoiding the occurrence of surge current in the converter device 12.

[0065] In the above example, voltage detection using a detection resistor is illustrated, but the present invention is not limited to this example. For example, a voltmeter or a voltage sensor may be used to detect the voltage difference between both ends of relay SW1, or other methods may be used as appropriate.

[0066] According to this embodiment, the following effects are achieved. In the converter devices 10, 11, 12, and 13 of the present disclosure, the control unit 24 may switch between low-voltage control and high-voltage control by switching the relay SW1 at a switching timing when the difference in voltage between both ends of the relay SW1 becomes substantially zero. That is, the control unit 24 turns on the relay SW1 at a switching timing when the difference in voltage between both ends of the relay SW1 becomes substantially zero. This makes it possible to suppress surge currents flowing through the relay SW1 and electrical elements connected to the relay SW1, such as the diodes D1 to D4 and the capacitors C1 and C2. This also makes it possible to reduce damage to these electrical elements.

[0067] The converter devices 11, 12 of the present disclosure may include a zero-cross detector 23 that detects zero-cross timings of AC power supplied from an AC power source, and the controller 24 may set the switching timing to a timing that is shifted by a predetermined phase amount from the zero-cross timings detected by the zero-cross detector 23. Note that this predetermined phase amount is determined based on the results of a simulation or test performed in advance. This makes it possible to more accurately set the switching timing, which is the timing when the voltage difference between both ends of the relay SW1 becomes approximately zero, and more reliably suppress surge currents.

[0068] The predetermined phase amount may be selected from a plurality of allowable ranges that are gradually reduced within a predetermined numerical range based on simulation results. By providing an allowable range for the predetermined amount in this manner, the predetermined phase amount can be flexibly set in accordance with the control conditions of the converter device.

[0069] The converter devices 11 and 12 of the present disclosure may be provided with voltage-dividing resistor groups Rd1, Rd2, and Rd3 that detect the voltage across the relay SW1, and the control unit 24 may set the switching timing based on the detection result of any one of the voltage-dividing resistor groups Rd1, Rd2, and Rd3. This allows the switching timing to be determined when the directly detected voltage difference across the relay SW1 becomes approximately zero. This allows surge current to be more reliably suppressed.

[0070] Although the present disclosure has been described above using embodiments, the technical scope of the present disclosure is not limited to the scope described in the above embodiments. Various modifications or improvements can be made to the above embodiments without departing from the gist of the present disclosure, and such modifications or improvements are also included in the technical scope of the present disclosure. Furthermore, the above embodiments may be combined as appropriate.

[0071] For example, in the present disclosure, the timing when the voltage difference between both ends of relay SW1 is zero is set as the switching timing, but taking into account a margin, the timing when the voltage difference between both ends of relay SW1 is approximately zero may be specified as the switching timing. In this case, the approximately zero range may be determined according to the characteristics of the electrical elements included in the converter device. Alternatively, it may be a range specified by the designer.

[0072] In addition, in the present disclosure, an example has been described in which the timing when the voltage difference between both ends of relay SW1 is approximately zero is set as the switching timing, and relay SW1 is turned on at the switching timing to avoid the generation of surge current, but this is not limited to this and may be applied to other switching elements.Furthermore, the circuit configuration of the rectifier element provided in the converter device is not limited to the example of this embodiment, and may be any of a bridge rectifier circuit, a horizontal bridgeless circuit, and a full-bridgeless rectifier circuit.

[0073] (Additional notes) The control system, the switching circuit including this control system, and the outdoor unit including this switching circuit described in the above-described embodiment can be understood, for example, as follows. The converter device according to the above-described embodiment and the motor drive device including the converter device can be understood, for example, as follows. A converter device according to a first aspect of the present disclosure includes a bridge rectifier circuit having a plurality of rectifier elements (D1 to D4) that rectify AC power supplied from an AC power supply; a plurality of capacitors (C1, C2) that are connected in parallel to the output side of the bridge rectifier circuit and are connected to each other in series; a switching element (SW1) having a first terminal connected to a midpoint (P1) between the plurality of series-connected rectifier elements and a second terminal connected to a midpoint (P2) between the plurality of capacitors; and a control unit (24) that controls the on / off of the switching element to switch between low-voltage control, in which current is supplied to all of the capacitors in one direction, and high-voltage control, in which the capacitors to be charged are switched every half cycle of the AC power supply, and the control unit turns on the switching element at a switching timing when the difference in voltage across the switching element becomes approximately zero.

[0074] According to the converter device of the present disclosure, the control unit switches between low-voltage control and high-voltage control by switching the switching element at a switching timing when the voltage difference between both ends of the switching element is approximately zero. For example, if the switching element switches from off to on at a timing when the voltage difference between both ends of the switching element is not approximately zero, a surge current will flow through the switching element and the electrical elements connected to the switching element. Furthermore, if the voltage difference between both ends of the switching element is large, the surge current will also be large, which may damage the switching element and the electrical elements connected to the switching element. Therefore, the control unit turns on the switching element at a switching timing when the voltage difference between both ends of the switching element is approximately zero. This suppresses the surge current flowing through the switching element and the electrical elements connected to the switching element. Furthermore, damage to each electrical element can be reduced.

[0075] The converter device according to a second aspect of the present disclosure is the converter device of the first aspect, which includes a detection unit (23) that detects zero-cross timings of AC power supplied from an AC power supply, and the control unit sets the switching timing to a timing that is shifted by a predetermined amount from the zero-cross timing detected by the detection unit.

[0076] The converter device disclosed herein includes a detector that detects the zero-cross timing of AC power supplied from an AC power supply, and a controller that sets the switching timing to a timing that is shifted a predetermined amount from the zero-cross timing detected by the detector. This allows the switching timing to be set to a timing at which the voltage difference between both ends of the switching element becomes approximately zero, even in cases where a surge current occurs when a switching element is turned on at the zero-cross timing of AC power supplied from the AC power supply. This allows the switching timing of the switching element to be changed as needed, thereby more reliably suppressing the occurrence of surge current.

[0077] A converter device according to a third aspect of the present disclosure is the converter device of the second aspect, wherein the predetermined amount is set based on the results of a simulation performed in advance or the results of a test performed in advance.

[0078] According to the converter device of the present disclosure, the predetermined amount is set based on the results of a simulation or test that has been performed in advance, which allows the switching timing, at which the voltage difference between both ends of the switching element becomes approximately zero, to be set more accurately, thereby more reliably suppressing surge currents.

[0079] The converter device according to a fourth aspect of the present disclosure is the converter device according to the first aspect, which includes a detection unit (Rd1, Rd2, Rd3) that detects the voltage across the switching element, and the control unit sets the switching timing based on the detection result of the detection unit.

[0080] The converter device of the present disclosure includes a detector that detects the voltage across the switching element, and the controller sets the switching timing based on the detection result. This allows the switching timing to be determined when the directly detected voltage difference across the switching element becomes approximately zero, thereby more reliably suppressing surge currents.

[0081] A motor drive device according to a first aspect of the present disclosure includes a converter device (10, 11, 12, 13) according to any one of the first to fourth aspects. [Explanation of symbols]

[0082] 1. Motor drive unit 2 AC power supply 3. Relay drive power supply 5 Bridge rectifier circuit 10, 11, 12, 13 Converter device 22 Input voltage detection section 23 Zero cross detector 24 Control Unit 40 Inverter device 50 motor 241 Timing Identification Unit 243 Control signal generation unit 244 Storage section C1 and C2 capacitors D1~D4 Diodes I1, I2 current L1 reactor Rd1, Rd2, Rd3 voltage dividing resistors SW1 relay ZC Zero cross timing

Claims

1. a bridge rectifier circuit including a plurality of rectifier elements that rectify AC power supplied from an AC power supply; a plurality of capacitors connected in parallel to an output side of the bridge rectifier circuit and connected in series with each other; a switching element having a first terminal connected to a midpoint between the plurality of rectifying elements connected in series and a second terminal connected to a midpoint between the plurality of capacitors; a control unit that controls on / off of the switching elements to switch between a low voltage control in which current is supplied to all of the capacitors in one direction and a high voltage control in which the capacitors to be charged are switched every half cycle of the AC power supply; a first detection unit that detects a voltage across the switching element; Equipped with The control unit turns on the switching element at a switching timing when a difference in voltage across the switching element becomes substantially zero based on the detection result of the first detection unit.

2. a second detection unit that detects zero-cross timings of AC power supplied from the AC power supply, The converter device according to claim 1 , wherein the control unit turns on the switching element at a switching timing that is shifted by a predetermined phase from the zero-cross timing detected by the second detection unit.

3. 3. The converter device according to claim 2, wherein the predetermined phase is set based on the results of a simulation or a test that has been carried out in advance.

4. The converter device according to claim 1; an inverter device that converts DC power supplied from the converter device into AC power and outputs the AC power; A motor drive device comprising:

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