JP7198344B2 - DC power supplies, motor drives, air conditioners, refrigerators and heat pump water heaters - Google Patents

Description

The present invention provides a DC power supply device comprising a step-up circuit in which a plurality of series circuits each composed of a reactor and a switching element are connected in parallel, a motor drive device, an air conditioner, a refrigerator, and a heat pump hot water supply device comprising the DC power supply device. Regarding the device.

In the power supply device disclosed in Patent Document 1, the output of a rectifier circuit is branched into a plurality of current paths, and a plurality of series circuits each composed of a reactor and a switching element are provided in parallel. When the switching element is off, the current output from the reactor provided in each of the plurality of series circuits is supplied to the smoothing capacitor via the backflow prevention diode. In the power supply device disclosed in Patent Literature 1, the voltage output from the smoothing capacitor can be boosted by adjusting the duty ratio of the switching element. In the power supply device disclosed in Patent Document 1, the switching elements provided in each of the plurality of series circuits are driven in different phases. As a result, the current flowing through each of the plurality of switching elements is suppressed, and the ripple component of the current output from the reactor is suppressed. A booster circuit that includes a plurality of series circuits connected in parallel and in which switching elements provided in each of the plurality of series circuits that are connected in parallel are driven in different phases is generally called an interleaved booster circuit.

JP 2007-195282 A

In a booster circuit in which a plurality of series circuits each composed of a reactor and a switching element are connected in parallel, as described in Patent Document 1, when a voltage exceeding a target voltage for boosting is input, the boosting operation is performed. Since there is no need to perform switching, the switching duty ratio of the switching element is zero. When the switching duty ratio of the switching element becomes 0, active control by switching of the switching element is no longer performed, so the booster circuit behaves like a passive circuit. At that time, the current concentrates in the series circuit reactors connected in parallel and in the low-impedance path. As a result, there is a problem that parts such as reactors and electronic parts on paths with low impedance may generate abnormal heat.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a DC power supply device capable of suppressing abnormal heat generation of components.

In order to solve the above-described problems and achieve the object, a DC power supply device according to the present invention includes a rectifier circuit that rectifies an AC voltage output from an AC power supply, a plurality of reactors, a plurality of switching elements, and a plurality of reverse currents. a booster circuit that has a prevention element and boosts the voltage rectified by the rectifier circuit. Further, the DC power supply device includes a smoothing capacitor that smoothes an output voltage, which is a voltage output from the booster circuit, and a voltage detection section that detects the voltage across the smoothing capacitor. Furthermore, when the voltage detected by the voltage detection unit is equal to or higher than the target value of the output voltage, the DC power supply determines the duty ratios of the plurality of switching elements to a predetermined value greater than 0 and equal to or less than the threshold, and determines and a primary current detection circuit that detects current flowing between the rectifier circuit and the booster circuit . The control unit detects an abnormality depending on whether at least one of the current detected by the primary current detection circuit and the voltage detected by the voltage detection unit is within an abnormal range, and if an abnormality is detected, the switching elements are switched. to stop the operation of

ADVANTAGE OF THE INVENTION The DC power supply device concerning this invention is effective in the ability to suppress abnormal heat_generation|fever of components.

1 is a diagram showing a configuration example of a DC power supply device according to a first embodiment; FIG. 1 is a diagram showing a configuration example of a control circuit including the processor of Embodiment 1; FIG. 3 is a flow chart showing an example of the operation of the control unit of the DC power supply device according to Embodiment 1. FIG. 10 is a diagram showing a configuration example of a motor drive device according to Embodiment 2; A diagram showing a configuration example of an air conditioner according to Embodiment 3

BEST MODE FOR CARRYING OUT THE INVENTION A DC power supply device, a motor drive device, an air conditioner, a refrigerator, and a heat pump water heater according to embodiments of the present invention will be described below in detail with reference to the drawings. In addition, this invention is not limited by this embodiment.

Embodiment 1.
FIG. 1 is a diagram showing a configuration example of a DC power supply device according to Embodiment 1 of the present invention. The DC power supply device 100 can convert AC power supplied from an AC power supply 1, which is a single-phase AC power supply, into DC power, and then boost and output the DC power.

The DC power supply device 100 is provided between the inrush prevention circuit 3, which is an inrush current prevention circuit for preventing inrush current, and the AC power supply 1 and the inrush prevention circuit 3, and is superimposed on the current output from the AC power supply 1. and a noise filter 2 for reducing high frequency noise. The DC power supply device 100 further includes a rectifier circuit 4 that rectifies the AC voltage output from the AC power supply 1 via the noise filter 2 and the inrush prevention circuit 3, and a booster circuit 20 that boosts the voltage rectified by the rectifier circuit 4. and a smoothing capacitor 8 for smoothing the voltage output from the booster circuit 20 . The DC power supply 100 further includes a primary current detection shunt resistor 9 connected to the negative end of the booster circuit 20, and a primary current detecting shunt resistor 9 disposed between the rectifier circuit 4 and the shunt resistor 9, which is the power supply current. It comprises a primary current detection circuit 10 which is a current detection circuit for detecting current, and a voltage detection section 12 for detecting the voltage across the smoothing capacitor 8 . The DC power supply device 100 further includes a control section 11 that controls the booster circuit 20 .

When the DC power supply 100 shown in FIG. 1 starts to operate, a current called rush current flows because the smoothing capacitor 8 does not have electric charge in the initial state. The rush prevention circuit 3 is provided to prevent damage to parts due to rush current. AC power supplied from an AC power supply 1 is full-wave rectified by a rectifier circuit 4 via a noise filter 2 and an inrush prevention circuit 3 , boosted by a booster circuit 20 and smoothed by a smoothing capacitor 8 .

The booster circuit 20 includes three reactors 5 , three switching elements 6 and three backflow prevention diodes 7 . One reactor 5 and one switching element 6 constitute one series circuit. Although three series circuits are connected in parallel in the example shown in FIG. 1, the number of series circuits connected in parallel is not limited to three, and may be two or four or more. That is, the booster circuit 20 only needs to have multiple reactors 5 , multiple switching elements 6 and multiple backflow prevention diodes 7 . The midpoint of each series circuit is connected to the positive electrode of a smoothing capacitor 8 via a backflow prevention diode 7 .

Each of the three reactors 5 can use, for example, a core with low harmonic iron loss, but the core of each of the three reactors 5 is not limited to this. The core of each of the three reactors 5 is the circuit configuration of the DC power supply 100, the control method by the control unit 11, the power conversion efficiency of the DC power supply 100, the amount of heat generated in the DC power supply 100, and the weight of the DC power supply 100. , the volume of the DC power supply device 100 may be considered.

Each of the three switching elements 6 is, for example, an IGBT (Insulated Gate Bipolar Transistor) or a MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor). Each of the three switching elements 6 has a collector or drain connected between the reactor 5 and the backflow prevention diode 7 and an emitter or source connected to the shunt resistor 9 .

Each of the three backflow prevention diodes 7 is an example of a backflow prevention element. The backflow prevention diode 7 has an anode connected to the reactor 5 and the switching element 6 and a cathode connected to the smoothing capacitor 8 .

The shunt resistor 9 is provided for primary current detection, and has one end connected to one end of the booster circuit 20 , specifically the emitter or source of the switching element 6 . The other end of the shunt resistor 9 is connected to a connection line that connects the negative terminal of the rectifier circuit 4 and the negative electrode of the smoothing capacitor 8 . The primary current detection circuit 10 is connected between the connection line connecting the negative terminal of the rectifier circuit 4 and the negative electrode of the smoothing capacitor 8 to the shunt resistor 9 at a connection point 13 and the negative terminal of the rectifier circuit 4. provided in Thereby, the primary current detection circuit 10 detects the current flowing between the rectifier circuit 4 and the booster circuit 20 as the primary current. The primary current detection circuit 10 outputs the primary current detection result to the control unit 11 .

The smoothing capacitor 8 smoothes the voltage that has been full-wave rectified by the rectifier circuit 4 and boosted by the booster circuit 20 . The positive electrode of smoothing capacitor 8 is connected to the cathode of backflow prevention diode 7 , and the negative electrode of smoothing capacitor 8 is connected to shunt resistor 9 and primary current detection circuit 10 .

The control section 11 is connected to the primary current detection circuit 10 and to the voltage detection section 12 . The control unit 11 acquires the detection result of the primary current from the primary current detection circuit 10 and acquires the detection result of the voltage across the smoothing capacitor 8 from the voltage detection unit 12 . Also, although not shown, the control unit 11 is connected to each switching element 6 and sends a PWM (Pulse Width Modulation) control signal for controlling ON and OFF of each switching element 6 to each switching element 6. Output. The control unit 11 generates a PWM signal such that the periods in which the switching elements 6 are turned on are shifted from each other so that the switching elements 6 are not turned on at the same time.

In addition, the control unit 11 adjusts the target voltage and the primary current so that the output voltage, which is the voltage boosted by the booster circuit 20, becomes the target voltage, which is the target value of the output voltage and is a predetermined value. A switching duty ratio that is a duty ratio of each switching element 6 is determined based on the detection result and the voltage value, and a PWM signal is generated based on the switching duty ratio. A general method can be used for determining the switching duty ratio of each switching element 6 so that the voltage boosted by the booster circuit 20 becomes the target voltage, and there are no particular restrictions, so detailed description is omitted. .

The control unit 11 is implemented by a processing circuit. This processing circuit may be a control circuit comprising a processor, or may be dedicated hardware. FIG. 2 is a diagram showing a configuration example of a control circuit including the processor of this embodiment. The control circuit 200 has a processor 201 and a memory 202 . The processor 201 is a CPU (also referred to as a Central Processing Unit, central processing unit, processing unit, arithmetic unit, microprocessor, microcomputer, processor, DSP (Digital Signal Processor)). The memory 202 corresponds to, for example, non-volatile or volatile semiconductor memory such as RAM (Random Access Memory), ROM (Read Only Memory), and flash memory.

When the control unit 11 is implemented by the control circuit 200 shown in FIG. 2, the control unit 11 is implemented by the processor 201 reading and executing a program stored in the memory 202 . The memory 202 is also used as temporary memory in each process performed by the processor 201 .

When the above processing circuit is configured as dedicated hardware, the processing circuit includes a single circuit, a composite circuit, a programmed processor, a parallel programmed processor, an ASIC (Application Specific Integrated Circuit), an FPGA (Field Programmable Gate Array), or a combination of these. The control unit 11 may be realized by combining a processing circuit and a control circuit, which are dedicated hardware.

Next, the operation of this embodiment will be described. In a general booster circuit in which a plurality of series circuits each composed of a reactor and a switching element are connected in parallel, the switching duty ratio becomes 0 when a voltage exceeding the target voltage for boosting is input. When the switching duty ratio becomes 0, current concentrates in multiple reactors and low-impedance paths. This may cause abnormal heat generation in parts such as reactors and electronic parts on paths with low impedance. In the present embodiment, in order to suppress such abnormal heat generation of parts, as described below, the control unit 11 sets the detected value of the voltage across the smoothing capacitor 8 (hereinafter simply referred to as the detected voltage value) as a target. If it is equal to or higher than the voltage, the duty ratio of the switching elements 6 is determined to be a predetermined value greater than 0 and equal to or less than the threshold value, and the switching elements 6 are controlled based on the determined duty ratio. An example of this predetermined value is a specified minimum value. That is, the control unit 11 operates the switching element 6 with a specified minimum switching duty ratio, for example. As a result, the DC power supply device 100 of the present embodiment suppresses concentration of current in the plurality of reactors 5 and low-impedance paths. Therefore, abnormal heat generation of the parts can be suppressed. The prescribed minimum switching duty ratio is, for example, the minimum switching duty ratio that can be set in DC power supply 100 . That is, one example of the predetermined value is the minimum value that can be set. The minimum switching duty ratio is determined, for example, by delays caused by switching characteristics of switching elements and circuit specifications, such as delays caused by RC filters, photocouplers, and the like. Also, the switch element has restrictions such as the minimum allowable pulse width. A minimum switching duty ratio is defined, for example, to satisfy these constraints. In the following, an example in which a specified minimum switching duty ratio is used when the detected value of the voltage across the smoothing capacitor 8 is equal to or higher than the target voltage will be described. Any duty ratio may be used.

FIG. 3 is a flow chart showing an example of the operation of the control unit 11 of the DC power supply device 100 of this embodiment. In the initial state, the control section 11 stops all switching elements 6 . When the control unit 11 starts operating (step S1), it acquires detection results of the primary current and voltage (step S2). Specifically, the control unit 11 acquires the detection result of the primary current from the primary current detection circuit 10 and acquires the detection result of the voltage across the smoothing capacitor 8 from the voltage detection unit 12 . The primary current detection circuit 10 and the voltage detection unit 12 may periodically output detection results to the control unit 11, and the control unit 11 may cause the primary current detection circuit 10 and the voltage detection unit 12 to transmit the detection results. Detection results may be obtained from the primary current detection circuit 10 and the voltage detection unit 12 by instructing them.

The control unit 11 determines whether at least one of the primary current and the voltage is within the abnormal range (step S3). Abnormal ranges are predetermined for each of the primary current and voltage. An abnormal range is a range outside the normal range. The upper limit of the normal range is set, for example, to a voltage that satisfies the withstand voltage constraints of the power module and capacitor used. The lower limit of the normal range is set according to the load-side current tolerance, inrush current tolerance, and the like. For example, if for some reason the DC voltage cannot be boosted to the target voltage during operation and the DC voltage drops, the current on the load side, including the inverter, will increase, and electronic components may break down or performance may decline. be. Further, when the DC power supply is restored after the DC voltage drops due to an instantaneous power failure during operation, a large inrush current may flow. For these reasons, the lower limit of the normal range is set, and if the lower limit is exceeded, it is judged to be abnormal and the operation is stopped. Returning to the description of FIG. 3, if at least one of the primary current and voltage is within the abnormal range (step S3 Yes), the control unit 11 determines that there is an abnormality and stops the switching element 6 from operating. That is, the control unit 11 detects an abnormality based on at least one of the current detected by the primary current detection circuit 10 and the voltage detected by the voltage detection unit 12, and when an abnormality is detected, the switching elements Stop the operation of 6. At this time, the control unit 11 may inform the user of the abnormality by notifying it to the outside or displaying it on a display unit (not shown).

An open phase may occur in the booster circuit 20 due to disconnection of the reactor 5, failure of the switching element 6, or the like. If the step-up operation is continued in the open-phase state, the energy supplied to the smoothing capacitor 8 may be insufficient depending on the size of the load connected to the subsequent stage of the DC power supply 100, and the load cannot be operated continuously. there is a possibility. For example, when the DC power supply device 100 is used in an air conditioner or the like, the inability to continuously operate the air conditioner or the like causes a problem of impairing comfort and energy saving. For this reason, in the present embodiment, the abnormal ranges of the primary current and voltage are defined as ranges assumed to be in the case of an open-phase state, and switching is performed when at least one of the primary current and voltage is within the abnormal range. By stopping the operation of the element 6, it is possible to prevent the boosting operation from continuing in the open-phase state.

Further, as will be described later, in the present embodiment, the switching element 6 is operated in a state where the detected voltage is equal to or higher than the target voltage (step S6 via step S7 described later). The voltage may exceed the target voltage, or the control may become unstable and the voltage across the smoothing capacitor 8 may fall below the target voltage. If a range higher than the target voltage by a certain value or more and a range lower than the target voltage by a certain value or more are defined as the abnormal range of the voltage, it is judged as Yes in step S3 after step S6 via step S7, and the switching element 6 can be stopped.

If both the primary current and voltage are not within the abnormal range (step S3 No), the control unit 11 determines whether the detected voltage, that is, the detection result of the voltage detection unit 12, is less than the target voltage (step S4). If the detected voltage is less than the target voltage (step S4 Yes), the control unit 11 determines the switching duty ratio based on the target voltage, the detected primary current and the voltage (step S5). Then, the control unit 11 generates a PWM signal based on the determined switching duty ratio and outputs it to the switching element 6 (step S6), and repeats the processing from step S2.

If the detected voltage is equal to or higher than the target voltage (step S4 No), the control unit 11 sets the switching duty ratio to the specified minimum switching duty ratio (step S7), and proceeds to the process of step S6. As described above, in the present embodiment, the switching element 6 is operated while the detected voltage is equal to or higher than the target voltage. It may become unstable and the voltage across the smoothing capacitor 8 may fall below the target voltage. However, as described above, by appropriately determining the abnormal range of the voltage, it is determined that the voltage is within the abnormal range by the determination in step S3 (step S3 Yes), and the operation of the switching element 6 is stopped. be done. During normal operation, a current flows to the load side, so if the switching element 6 is turned off, a large current may flow to the reactor 5 or the like. , even if the switching element 6 is turned off, a large current does not flow through the reactor 5 or the like.

In general, abnormal heat generation of parts is difficult to detect until the parts fail. This is for the following reasons. When a voltage exceeding the target voltage is applied, the booster circuit does not perform boosting operation, so the current flows unevenly in the phase with the lowest impedance among the components such as reactors and reverse current element diodes connected in parallel in the booster circuit. Fever. In general, it is not possible to detect the temperature rise of these parts because the temperature of these parts is not necessary for control. Therefore, it is difficult to detect abnormal heat generation of a component until the component fails. Moreover, if a thermistor, a current detector, etc. are added only for the protection of the components, additional components will be required for the circuit, resulting in an increase in cost. On the other hand, as described above, the DC power supply device 100 of the present embodiment operates the switching element 6 with the specified minimum switching duty ratio when the detected voltage is equal to or higher than the target voltage. , a plurality of reactors 5, and a low-impedance path. Therefore, abnormal heat generation of the parts can be suppressed. Further, when the detected primary current or voltage is within the abnormal range, the switching element 6 is stopped, so that it is possible to prevent the voltage boosting operation from continuing in the open-phase state.

Embodiment 2.
FIG. 4 is a diagram showing a configuration example of a motor drive device according to Embodiment 2. In FIG. A motor drive device 101 according to the second embodiment includes the DC power supply device 100 described in the first embodiment. A motor drive device 101 drives a motor 42 as a load. Motor drive device 101 includes DC power supply device 100 described in the first embodiment, inverter 41 , motor current detector 44 , and inverter controller 43 . Inverter 41 converts the DC power supplied from DC power supply device 100 described in Embodiment 1 into AC power and outputs the AC power to motor 42 to drive motor 42 . In the following, the motor drive device 101 will be described as an example of a device using the DC power supply device 100 as a power source for the inverter 41. is not limited to That is, the load connected to the inverter 41 may be a device to which AC power is input, and may be a device other than the motor 42 .

The inverter 41 is a circuit in which switching elements such as IGBTs have a three-phase bridge configuration or a two-phase bridge configuration. The switching elements used in inverter 41 are not limited to IGBTs.

A motor current detector 44 detects a current flowing between the inverter 41 and the motor 42 . The inverter control unit 43 uses the current detected by the motor current detection unit 44 to generate a PWM signal for driving the switching elements in the inverter 41 so that the motor 42 rotates at a desired rotation speed. is applied to the inverter 41. The inverter control unit 43 is realized by a processing circuit, like the control unit 11 of the first embodiment.

As described above, motor drive device 101 of the present embodiment can suppress abnormal heat generation of components by using DC power supply device 100 described in the first embodiment. Further, when the detected primary current or voltage is within the abnormal range, the switching element 6 is stopped, so the operation of the motor 42 can be stopped. Therefore, it is possible to prevent the voltage boosting operation from continuing in the state of an open phase, and to prevent the motor 42 from being continuously operated.

Embodiment 3.
FIG. 5 is a diagram showing a configuration example of an air conditioner according to Embodiment 3. In FIG. As shown in FIG. 5, air conditioner 700 of the present embodiment includes motor drive device 101 and motor 42 described in the second embodiment. That is, air conditioner 700 includes DC power supply device 100 described in the first embodiment. The air conditioner 700 includes a compressor 81 incorporating a compression mechanism 87 and a motor 42, a four-way valve 82, an outdoor heat exchanger 83, an expansion valve 84, an indoor heat exchanger 85, and a refrigerant pipe 86. . The air conditioner 700 is not limited to a separate type air conditioner in which the outdoor unit is separated from the indoor unit, and may be one in which the compressor 81, the indoor heat exchanger 85 and the outdoor heat exchanger 83 are provided in one housing. A body type air conditioner may be used. The motor 42 is driven by a motor drive device 101 .

A compression mechanism 87 that compresses refrigerant and a motor 42 that operates the compression mechanism 87 are provided inside the compressor 81 . The refrigerant circulates through the compressor 81, the four-way valve 82, the outdoor heat exchanger 83, the expansion valve 84, the indoor heat exchanger 85, and the refrigerant pipe 86, thereby forming a refrigeration cycle. Although the air conditioner 700 has been described as an example of the refrigeration cycle device including the motor drive device 101 and the motor 42 described in Embodiment 2, the refrigeration cycle device including the DC power supply device 100 is the air conditioner 700. Without limitation, it may be a refrigerator, a heat pump water heater, or the like.

Further, in the example described above, the configuration example in which the motor 42 is used as the driving source of the compressor 81 and the motor 42 is driven by the motor driving device 101 has been described. However, the motor 42 may be applied to the drive source for driving the indoor unit fan and the outdoor unit fan (not shown) provided in the air conditioner 700 and the motor 42 may be driven by the motor drive device 101 . Alternatively, the motor 42 may be applied to the drive source of the indoor blower, the outdoor blower, and the compressor 81 , and the motor 42 may be driven by the motor drive device 101 .

As described above, air conditioner 700 of the present embodiment can suppress abnormal heat generation of components by using DC power supply device 100 described in the first embodiment. Further, when the detected primary current or voltage is within the abnormal range, the switching element 6 is stopped, so the operation of the air conditioner 700 can be stopped. Therefore, it is possible to prevent the pressure-increasing operation from continuing in the state of open-phase, and it is possible to prevent the phenomenon that the air conditioner 700 cannot be operated continuously. Thereby, comfort and energy saving can be maintained. Even when DC power supply device 100 described in Embodiment 1 is applied to a refrigeration cycle device other than air conditioner 700, the same effects as air conditioner 700 can be obtained.

The configuration shown in the above embodiment shows an example of the content of the present invention, and it is possible to combine it with another known technology, and one configuration can be used without departing from the scope of the present invention. It is also possible to omit or change the part.

1 AC power supply, 2 noise filter, 3 inrush prevention circuit, 4 rectifier circuit, 5 reactor, 6 switching element, 7 backflow prevention diode, 8 smoothing capacitor, 9 shunt resistor, 10 primary current detection circuit, 11 control section, 12 voltage detection Section 20 Booster Circuit 41 Inverter 42 Motor 43 Inverter Control Section 44 Motor Current Detection Section 81 Compressor 82 Four-Way Valve 83 Outdoor Heat Exchanger 84 Expansion Valve 85 Indoor Heat Exchanger 86 Refrigerant Piping , 87 compression mechanism, 100 DC power supply, 101 motor drive, 700 air conditioner.

Claims (6)

a rectifier circuit that rectifies an AC voltage output from an AC power supply;
a booster circuit having a plurality of reactors, a plurality of switching elements, and a plurality of backflow prevention elements, for boosting the voltage rectified by the rectifier circuit;
a smoothing capacitor for smoothing the output voltage, which is the voltage output from the booster circuit;
a voltage detection unit that detects the voltage across the smoothing capacitor;
when the voltage detected by the voltage detection unit is equal to or higher than the target value of the output voltage, the duty ratio of the plurality of switching elements is determined to be a predetermined value greater than 0 and less than or equal to a threshold, and the determined duty ratio a control unit that controls the plurality of switching elements based on
a primary current detection circuit that detects current flowing between the rectifier circuit and the booster circuit;
with
The control unit detects an abnormality depending on whether at least one of the current detected by the primary current detection circuit and the voltage detected by the voltage detection unit is within an abnormal range. A DC power supply that stops the operation of a plurality of switching elements. 2. The DC power supply according to claim 1, wherein said predetermined value is a settable minimum value. A DC power supply device according to claim 1 or 2 ;
an inverter that converts the DC power output from the DC power supply into AC power and outputs the AC power to the motor;
A motor drive device comprising: a motor;
a motor driving device according to claim 3 , which drives the motor;
An air conditioner with a motor;
a motor driving device according to claim 3 , which drives the motor;
refrigerator. a motor;
a motor driving device according to claim 3 , which drives the motor;
A heat pump water heater.

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