JP2018121373A - Heat source device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat source device capable of reducing power loss of a booster circuit.SOLUTION: A diode for reverse current prevention in a booster circuit is connected in parallel to a second switch. And, a step-up operation and a non-step-up operation are alternatively switched according to an operating state of a motor, and at a step-up operation by turning on/off of a first switch in the booster circuit, the second switch is turned on/off with a phase opposite to turning on/off of the first switch, and at a non-step-up operation by turning off of the first switch, the second switch is turned on.SELECTED DRAWING: Figure 1

Description

  Embodiments described herein relate generally to a heat source device including a booster circuit.

  In a heat source device such as an air conditioner, the compressor motor is driven at a variable speed by an inverter to vary the heating or cooling capacity. In order to obtain a large capacity, it is necessary to increase the rotational speed of the compressor motor. Therefore, in order to obtain a larger rotational speed, a booster circuit is provided to increase the DC voltage supplied to the inverter.

  As such a booster circuit, an input voltage is applied to a reactor through a switch element, the input voltage is boosted by switching the switch element on and off, and the boosted voltage is output through a diode for preventing backflow. A circuit is known.

JP 2014-212588 A

  The backflow prevention diode mounted on the booster circuit has a resistance value with respect to a current flowing in the forward direction. The existence of this resistance value leads to power loss of the booster circuit and cannot be ignored in terms of energy saving.

  Further, during the boosting operation of the booster circuit, the switch element is driven, and thus a loss corresponding to that occurs.

  An object of an embodiment of the present invention is to provide a heat source device that can reduce power loss when a booster circuit is provided.

  The heat source device according to claim 1 boosts the input voltage by turning on and off the first switch and outputs the boosted voltage through a backflow prevention diode, and converts the output of the booster circuit into alternating current and outputs it as drive power to the motor. An inverter, and a second switch connected in parallel to the diode, and switches between a boosting operation and a non-boosting operation of the booster circuit according to the operating state of the motor, and the first switch is turned on , A control means for turning on and off the second switch at a phase opposite to the on / off of the first switch during the boost operation by turning off, and turning on the second switch at the non-boosting operation by turning off the first switch And comprising.

The block diagram which shows the structure of one Embodiment. The flowchart which shows the control of one Embodiment. 4 is a time chart showing the boosting operation of the boosting circuit in one embodiment. The block diagram which shows the structure of the modification of one Embodiment.

Hereinafter, as an embodiment, a refrigeration cycle apparatus mounted on a heat source apparatus such as an air conditioner will be described as an example.
As shown in FIG. 1, a full-wave rectifier circuit 2 of a diode bridge is connected to an AC power source 1, and a smoothing capacitor 3 is connected to the output terminal of the full-wave rectifier circuit 2. The booster circuit 10 is connected to both ends of the smoothing capacitor 3.

  The step-up circuit 10 includes a step-up reactor 11, a switch element (first switch) SW1, a backflow prevention diode 12, and a smoothing capacitor (electrolytic capacitor) 13. The switch element SW1 is turned on / off and turned on. The input voltage (the output voltage of the full-wave rectifier circuit 2) is boosted by repeating the charge and discharge of the reactor 11 accompanying the turn-off, and the boosted voltage is applied to the capacitor 13 through the diode 12, The voltage generated in the capacitor 13 is output. Further, the booster circuit 10 applies the input voltage to the capacitor 13 without being boosted as it is through the reactor 11 and the diode 12 by continuously turning off the switch element SW1, and outputs the voltage generated in the capacitor 13. For example, a MOSFET is used as the switch element SW1.

  A switch element (second switch) SW2 is connected in parallel to the diode 12 of the booster circuit 10. The switch element SW2 is a switch element such as a MOSFET having bidirectionality in which current flows in both directions between the emitter and the collector when turned on and having a resistance value smaller than the forward resistance value of the diode 12 when turned on.

  An inverter 20 is connected to the output terminal of the booster circuit 10. The inverter 20 performs AC conversion on the output voltage of the booster circuit 10 by switching, and outputs it as drive power to the motor 40M. The motor 40M is a driving motor (for example, a brushless DC motor) for the compressor 40 mounted on the refrigeration apparatus.

  The compressor 40 sucks in the refrigerant, compresses it, and discharges it. One end of an outdoor heat exchanger 42 is connected to the refrigerant discharge port of the compressor 40 via a four-way valve 41, and the other end of the outdoor heat exchanger 42 is connected to one end of the indoor heat exchanger 44 via an expansion valve 43. Connected. The other end of the indoor heat exchanger 44 is connected to the refrigerant suction port of the compressor 40 via the four-way valve 41. The compressor 40, the four-way valve 41, the outdoor heat exchanger 42, the expansion valve 43, and the indoor heat exchanger 44 constitute a refrigeration cycle for an air conditioner.

  In the booster circuit 10, the current sensor 14 is disposed on the connection line between the reactor 11 and the diode 12 and at a position closer to the reactor 11 than the connection point of the switch element SW1. The current sensor 14 detects the current flowing through the reactor 11. In addition, the voltage detector 15 is connected to both ends of the capacitor 13 in the booster circuit 10. The voltage detector 15 detects the output voltage (voltage of the capacitor 13) Vdc of the booster circuit 10. Furthermore, current sensors 16, 17, and 18 that detect a current (phase winding current) flowing through the motor 40 </ b> M are arranged on a connection line between the inverter 20 and the motor 40 </ b> M. These current sensor 14, voltage detection unit 15, and current sensors 16 to 18 are connected to the control unit 30. In addition, an operating unit 31 for setting operating conditions is connected to the control unit 30.

The control unit 30 controls the booster circuit 10 and the inverter 20 and has the following means (1) to (5) as main functions.
(1) First control means for controlling the on / off duty of switching of the inverter 20 so that the speed of the motor 40M becomes a target speed corresponding to the load of the compressor 40 (= the required load of cooling / heating).

  (2) When the on / off duty controlled by the first control means is greater than or equal to a predetermined value A%, the switch element SW1 of the booster circuit 10 is turned on and off to boost the booster circuit 10, and the first control means The second control means for turning off the switch element SW1 of the booster circuit 10 (continuously off) and causing the booster circuit 10 to perform a non-boosting operation when the on / off duty by the control of is lower than a predetermined value B% (<A%) .

  Originally, the pressure increase is necessary when the rotational speed of the compressor 40 is increased, and is not necessary when operating at a low rotational speed. On the other hand, when the booster circuit 10 is operated, a loss occurs due to the on / off operation of the switch element SW1. Therefore, when the rotation speed of the compressor 40 is low, the booster circuit 10 is stopped (non-boosted). As a result, the efficiency of the compressor 40 at a low rotation speed is improved. Here, the on / off duty values controlled by the first control means are used as parameters indicating the motor operating state. However, other values indicating the motor operating state include the motor rotation speed and the motor target rotation. Number, motor current, etc. may be used.

  (3) During the boosting operation of the booster circuit 10, the on / off duty of the switch element SW1 is controlled so that the output voltage Vdc of the booster circuit 10 becomes a predetermined target value, and the on / off of the switch element SW1 Third control means for turning on and off the switch element SW2 in the opposite phase.

  (4) Fourth control means for turning on (continuously on) the switch element SW2 during the non-boosting operation of the booster circuit 10.

  (5) When the switch element SW2 is turned on / off, the switch element SW2 is switched from on to off before the switch element SW1 is switched from off to on, whereby the switch element SW1 is switched from off to on. A dead time t1 in which both the switch elements SW1 and SW2 are both turned off is ensured between the timing when SW2 is switched from on to off, and the switch element SW2 is switched after the switch element SW1 is switched from on to off. The dead time t2 when both the switch elements SW1 and SW2 are turned off between the timing at which the switch element SW1 is switched from on to off and the timing at which the switch element SW2 is switched from off to on. 5th control means to ensure.

  The full-wave rectifier circuit 2, the booster circuit 10, the inverter 20, the current sensors 14, 16 to 17, the voltage detection unit 15, the control unit 30, and the like constitute the heat source device of the present embodiment.

  Next, the control executed by the control unit 30 will be described with reference to the flowchart of FIG. 2 and the time chart of FIG. In FIG. 3, Isw1 is a current flowing through the switch element SW1, Idi is a current flowing through the diode 12, and Isw2 is a current flowing through the switch element SW2.

  When there is an operation start operation at the operation unit 31 (YES in step S1), the control unit 30 turns off (continuously turns off) the switch element SW1 of the booster circuit 10 to cause the booster circuit 10 to perform a non-boosting operation. In the state, the operation of the inverter 20 is started and the compressor 40 is started (step S2).

  Along with this activation, the control unit 30 detects the speed of the motor 40M from the detected currents of the current sensors 16 to 18, and the inverter so that the detected speed becomes a target speed corresponding to the load (air conditioning load) of the compressor 40. The on / off duty (also referred to as a current supply rate) of 20 switching is controlled (step S3).

  At this point, the control unit 30 has not yet boosted the booster circuit 10 (NO in step S4), so the on / off duty of switching of the inverter 20 reaches a predetermined value A% (for example, the maximum value 100%). It is determined whether or not (step S5). When the on / off duty of switching of the inverter 20 does not reach the predetermined value A% (NO in step S5), the control unit 30 monitors the operation stop operation of the operation unit 31 (step S9). When there is no operation to stop (NO in step S9), the control unit 30 returns to the inverter output control in step S3.

  The state where the on / off duty of switching of the inverter 20 reaches the maximum value of 100% is a state where the output voltage of the inverter 20 cannot be increased any more, and the output voltage of the inverter 20 needs to be further increased. In this case, the boosting operation of the booster circuit 10 is necessary.

  When the ON / OFF duty of switching of the inverter 20 reaches the predetermined value A% (YES in step S5), the control unit 30 turns on and off the switch element SW1 of the booster circuit 10 to boost the booster circuit 10. (Step S6). Specifically, the control unit 30 performs PWM modulation on a carrier signal (triangular wave signal) having a predetermined frequency based on the level of the current detected by the current sensor 14 (reactor current), thereby driving the switching element SW1 (PWM signal). And the ON / OFF duty of the drive signal is controlled so that the detection voltage (output voltage of the booster circuit 10) Vdc of the voltage detection unit 15 becomes a predetermined target value. Further, the control unit 30 turns on / off the switch element SW2 at a phase opposite to that of the switch element SW1.

  When the switch element SW1 is turned on, an energization path for the reactor 11 is formed through the switch element SW1, and the reactor 11 is charged with electric charges (energy). At this time, since the switch element SW2 is OFF, the voltage of the capacitor 13 is not discharged through the switch element SW1 due to the backflow prevention action of the diode 12.

  Subsequently, when the switch element SW1 is turned off, electric charges are discharged from the reactor 11, and the voltage generated at both ends of the switch element SW1 changes in an increasing direction. At this time, since the switch element SW2 is on, the voltage generated at both ends of the switch element SW1 is applied to the capacitor 13 via the switch element SW2 having a resistance value smaller than that of the diode 12. That is, the current directed to the capacitor 13 passes through the switch element SW2 having a smaller resistance value than that of the diode 12. The power loss due to the current flowing through the switch element SW2 is smaller than the power loss when the current flows through the diode 12.

  When both switch elements SW1 and SW2 are turned on simultaneously, the capacitor 13 is short-circuited. In order to prevent this, a dead time t1 in which both the switch elements SW1 and SW2 are turned off is between the timing when the switch element SW1 is switched from OFF to ON and the timing when the switch element SW2 is switched from ON to OFF. Secured. Further, a dead time t2 in which both the switch elements SW1 and SW2 are turned off is secured between the timing when the switch element SW1 is switched from on to off and the timing when the switch element SW2 is switched from off to on. By ensuring the dead times t1 and t2, there is no problem that the voltage of the capacitor 13 is discharged through the switch element SW1. The dead times t1 and t2 may be the same time or different times, and optimum times are set for each.

  Note that, during the period of dead time t1 and t2 when both switch elements SW1 and SW2 are both turned off, the input voltage is applied to the capacitor 13 via the reactor 11 and the diode 12, so that current flows through the diode 12. Since the dead times t1 and t2 are extremely short, the power loss in the diode 12 is small.

  With the start of this boosting operation, the control unit 30 monitors the operation stop operation of the operation unit 31 (step S9). When there is no operation to stop (NO in step S9), the control unit 30 returns to the inverter output control in step S3.

  During the step-up operation (YES in step S4), the control unit 30 determines whether the switching on / off duty of the inverter 20 is less than a predetermined value B% (for example, 90%) (step S7). When the on / off duty of switching of the inverter 20 is not less than the predetermined value B% (NO in step S7), the control unit 30 monitors the operation stop operation of the operation unit 31 (step S9). When there is no operation to stop (NO in step S9), the control unit 30 returns to the inverter output control in step S3.

  When the on / off duty of switching of the inverter 20 is reduced to less than the predetermined value B% (YES in step S7), the control unit 30 turns off the switch element SW1 (continuously turns off) and does not boost the booster circuit 10 Operate (step S8). In this case, the input voltage to the booster circuit 10 is applied to the capacitor 13 without being boosted as it is through the reactor 11 and the switch element SW2, and the voltage generated in the capacitor 13 is output.

  Even during this non-boosting, current flows through the switch element SW2 having a smaller resistance value than the diode 12, so that the power loss in the boosting circuit 10 is small.

  At the time of non-boosting, the control unit 30 switches the switch element SW2 from off to on after the switch element SW1 is switched from on to off. This ensures a dead time during which both switch elements SW1 and SW2 are turned off between the timing when the switch element SW1 switches from on to off and the timing when the switch element SW2 switches from off to on. Therefore, the voltage of the capacitor 13 is not discharged through the switch element SW1.

  And the control part 30 monitors operation stop operation of the operation part 31 (step S9). When there is no operation to stop (NO in step S9), the control unit 30 returns to the inverter output control in step S3. When there is a driving stop operation (YES in step S9), the control unit 30 ends all the driving (step S10).

  As described above, the switch element SW2 is connected in parallel with the backflow prevention diode 12 in the booster circuit 10 and the switch element SW2 is turned on / off. The power loss of the booster circuit 10 can be reduced by turning on the switch element SW2 at the time of non-boosting when the switch element SW1 is turned off and turned on in the opposite phase. The energy saving effect can be improved.

  In the above embodiment, the booster circuit 10 having one diode 12 has been described as an example. However, as shown in FIG. 4, a plurality of, for example, three diodes 12a, 12b, and 12c are connected in parallel to each other, The booster circuit 10 having a configuration in which the switch elements (second switch elements) SW2a, SW2b, and SW2c are connected in parallel for each of 12b and 12c may be employed. The switch elements SW2a, SW2b, and SW2c are turned on while being synchronized with each other, and are turned off when being synchronized with each other.

  When the switch elements SW2a, SW2b, and SW2c are on, the current that flows from the reactor 11 side toward the capacitor 13 is shunted to the switch elements SW2a, SW2b, and SW2c. At the timing when both the switch element SW1 and the switch elements SW2a, SW2b, and SW2c are turned off in the dead time, the current flowing from the reactor 11 side toward the capacitor 13 is shunted to the diodes 12a, 12b, and 12c. By the diversion, the individual temperature rises of the diodes 12a, 12b, and 12c and the individual resistance values of the diodes 12a, 12b, and 12c accompanying the temperature rise can be suppressed. Thereby, the power loss when a current flows through the diodes 12a, 12b, and 12c can be suppressed as much as possible.

  In the above embodiment, the MOSFET is used as the switch element SW2. However, the switch element SW2 has a bidirectional property in which a current flows bidirectionally when turned on, and the switch element has a resistance value smaller than the forward resistance value of the diode 12 when turned on. For example, a switch element other than a MOSFET may be used.

  In addition, the said embodiment and modification are shown as an example and are not intending limiting the range of invention. The novel embodiments and modifications can be implemented in various other forms, and various omissions, rewrites, and changes can be made without departing from the spirit of the invention. In these embodiments and modifications, the scope of the invention is included in the gist, and is included in the invention described in the claims and the equivalents thereof.

  DESCRIPTION OF SYMBOLS 1 ... AC power source, 2 ... Full wave rectifier circuit, 10 ... Booster circuit, 11 ... Boosting reactor, 12 ... Backflow prevention diode, 13 ... Capacitor, SW1 ... Switch element (first switch element), SW2 ... Switch Element (second switch element), 14 ... current sensor, 15 ... voltage detection unit, 16-18 ... current sensor, 20 ... inverter, 30 ... control unit, 31 ... operation unit, 40 ... compressor, 40M ... motor, 41 ... Four-way valve, 42 ... Outdoor heat exchanger, 43 ... Expansion valve, 44 ... Indoor heat exchanger

Claims (6)

A booster circuit that boosts the input voltage by turning on and off the first switch and outputs the boosted voltage through a diode for preventing backflow;
An inverter that converts the output of the booster circuit into an alternating current and outputs it as drive power to the motor;
In a heat source device comprising:
A second switch connected in parallel to the diode;
According to the operating state of the motor, the boosting operation and non-boosting operation of the booster circuit are switched, and at the time of the boosting operation by turning on / off the first switch, the first switch is in a phase opposite to the on / off of the first switch. Control means for turning on and off two switches and turning on the second switch during non-boosting operation by turning off the first switch;
A heat source device comprising: The heat source device according to claim 1, wherein the second switch is a bidirectional switch element having a resistance value when turned on that is smaller than a forward resistance value of the diode. The heat source device according to claim 1, wherein the booster circuit applies a voltage passing through the diode to a capacitor and outputs a voltage of the capacitor. The heat source apparatus according to claim 1, wherein the control unit controls an on / off duty of the first switch so that an output voltage of the booster circuit becomes a target value. The control means ensures a dead time during which both switches are turned off between the timing when the first switch is switched from off to on and the timing when the second switch is switched from on to off. The dead time when both the switches are turned off is ensured between the timing when the first switch switches from on to off and the timing when the second switch switches from off to on. Heat source device. The inverter converts the output of the booster circuit into AC by switching and outputs it as driving power to the motor.
The control means controls on / off duty of switching of the inverter so that the speed of the motor becomes a target speed, and turns on / off the first switch when the on / off duty is a predetermined value or more. Continuously turning off the first switch when less than a predetermined value;
The heat source device according to claim 1.

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