JP2005245167A - Dc power supply unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To adjust DC voltage to an optimum voltage irrespective of fluctuations in AC voltage and to improve a power factor. <P>SOLUTION: The DC power unit comprises a bidirectional switch 10 to be short-circuited to an AC power supply 1 via a reactor 7; an opening/closing time selection means a for comparing an AC voltage applied to a load with a target voltage to select the opening/closing time of the bidirectional switch so that the DC voltage approaches the target voltage; an opening/closing time storage means 18 for storing the opening/closing time of the bidirectional switch according to the load amount; and an opening/closing time selection means b19 for selecting at which time of an opening/closing cycle consisting of two or more opening/closing times per half cycle of the power supply. The closing time stored in the opening/closing time storage means 18 is applied. At least once in two or more opening/closing per half cycle of the bidirectional switch power supply is made to be a closing time adjusted by the closing time selection means a, and at least once is made to be a closing time selected by the closing time selection means b, thereby enabling power rate to be improved while making the DC voltage approach to the target value, irrespective of the fluctuations in the AC voltage. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a DC power supply apparatus used in an air conditioner or the like, and more particularly to a DC power supply apparatus that requires an improvement in power factor and a boost in DC voltage.

  2. Description of the Related Art Conventionally, a step-up chopper system that short-circuits an AC power source at a high frequency via a reactor is widely known as means for simultaneously achieving power factor improvement and DC voltage boosting of a DC power supply device. In the boost chopper method, the power source power factor is improved and the harmonic current is suppressed, and the DC voltage is increased / decreased so that the operating range can be reduced, especially for loads with a wide operating range, such as compressor motors for air conditioners. Expansion and optimization of motor efficiency are possible. In addition, a method of reducing the number of short circuits to several times in a half cycle of the AC power supply has been proposed (see, for example, Patent Document 1).

FIG. 7 shows a conventional DC power supply device described in Patent Document 1. In FIG. As shown in FIG. 7, the AC power source 1, the rectifying means 6, the reactor 7, the backflow prevention diode 24, the smoothing capacitor 25, the load 11, the zero cross detecting means 12, and the reactor 7 are passed through. It comprises a bidirectional switch 10 for short-circuiting the AC power supply, a load amount detection means 15, a bidirectional switch control means 13 for controlling the opening / closing of the bidirectional switch 10, an opening / closing time selection means 26, and an opening / closing time storage means 18. The open / close time selection means 26 selects the open / close time of the bidirectional switch 10 corresponding to the load amount from the open / close time storage means 18 and transmits it to the bidirectional switch control means 13. The bidirectional switch control means 13 In this method, the bidirectional switch 10 is controlled at least twice in a half cycle of the power supply in synchronization with the zero cross.
JP 2000-125545 A

  However, in the conventional configuration, the high-frequency boost chopper method has problems such as an increase in noise generated due to high-frequency switching, a reduction in system efficiency due to an increase in switching element loss, and an increase in cost due to control complexity. Was.

  The method described in Patent Document 1 achieves power factor improvement while reducing the number of switching times compared with the step-up chopper method. However, the opening / closing time of the bidirectional switch 10 is stored in the storage unit 18 in advance. Since it is limited to the switching time corresponding to the load, for example, it has a problem that it is difficult to cope with a decrease in the DC voltage due to a fluctuation or a decrease in the AC voltage and a decrease in the compressor motor rotation speed associated therewith. It was.

  The present invention solves the above-mentioned conventional problems, and provides a DC power supply device that achieves both improvement in power factor, expansion of the operating range of a load represented by a compressor motor, and improvement in efficiency. Objective.

In order to solve the conventional problems, a DC power supply device of the present invention includes an AC power supply, a rectifier circuit that rectifies the AC power supply, a reactor connected between the AC power supply and an input terminal of the rectifier circuit, Connected in series with each other, connected in parallel to the output terminal of the rectifier circuit, the connection point of the series connection is a voltage doubler boost capacitor connected to one input terminal of the rectifier circuit, the voltage doubler boost capacitor and the A load connected in parallel to the output terminal of the rectifier circuit, a DC voltage detecting means for detecting a DC voltage applied to the load, a zero cross detecting means for detecting a zero cross of the AC power supply, and the AC power supply short-circuited through the reactor And at least twice in a half cycle of the AC power supply and in synchronization with the power supply cycle of the AC power supply in synchronism with the zero crossing point detected by the zero cross detection means. Bidirectional switch control means for opening and closing the switch, load amount detection means for detecting the load amount, target voltage storage means for storing the target value of the DC voltage corresponding to the load amount, and DC detected by the DC voltage detection means A closing time selection means a for adjusting at least one of the closing times of the bidirectional switch so that the voltage approaches the target voltage; and a closing time storage means for storing the closing time of the bidirectional switch corresponding to the detected load amount. And a closing time selection means b for selecting the number of times of closing and opening the closing time stored in the closing time storage means to be applied in a half cycle of the power supply. Of the two or more opening / closing cycles, at least once is the closing time adjusted by the closing time selection means a, and at least once is the closing time selected by the closing time selection means b. .

  As a result, an optimum DC voltage can be supplied to the load regardless of a voltage drop of the AC power supply, and when the compressor of the air conditioner is a load, a reduction in the maximum rotational speed can be prevented.

  The DC power supply device of the present invention can realize optimization of DC voltage while maintaining a high power factor.

  A first invention is an AC power supply, a rectifying circuit for rectifying the AC power supply, a reactor connected between the AC power supply and an input end of the rectifying circuit, and connected in series to each other at an output end of the rectifying circuit. The connecting point of the series connection is a voltage doubler boosting capacitor connected to one input terminal of the rectifier circuit, and a load connected in parallel to the voltage doubler voltage boosting capacitor and the output terminal of the rectifier circuit. Detected by a DC voltage detecting means for detecting a DC voltage applied to a load, a zero cross detecting means for detecting a zero cross of an AC power supply, a bidirectional switch for short-circuiting the AC power supply through the reactor, and a zero cross detecting means Bi-directional switch control means for opening and closing the bi-directional switch in synchronization with the power cycle of the AC power source at least twice in half cycle of the AC power source in synchronism with the zero cross point A load amount detection means for detecting a load amount, a target voltage storage means for storing a target value of a DC voltage corresponding to the load amount, and a bidirectional voltage so that the DC voltage detected by the DC voltage detection means approaches the target voltage. The closing time selection means a for adjusting at least one of the closing times of the switch, the closing time storage means for storing the closing time of the bidirectional switch corresponding to the detected load amount, and the closing time storage means. A closing time selection means (b) for selecting the number of opening / closing times of the two or more open / closed times in the power supply half cycle, and at least of the two or more open / closed times in the power supply half cycle of the bidirectional switch; One time is the closing time adjusted by the closing time selection means a, and at least once is the closing time selected by the closing time selection means b, so that the bidirectional time adjusted by the closing time selection means a Opening the switch Accordingly, while closer to DC voltage regardless decrease of the alternating voltage to a target value, the opening and closing of the bidirectional switch selected by closing time selection means b can be improved power factor. In the present invention, the AC power supply is short-circuited by a bidirectional switch based on a so-called voltage doubler rectifier circuit, but the same effect can be obtained by providing the closed time selection means a and the closed time selection means b even in different power supply systems. It goes without saying that you can get it.

  In particular, the second invention is directed to the DC power supply device according to the first invention. When the DC voltage exceeds a certain value, the bidirectional switch is forcibly opened regardless of the control state of the bidirectional switch control means. By providing an overvoltage protection means that is fixed to the DC voltage and suppresses boosting of the DC voltage, an abnormal increase in the DC voltage can be suppressed even when an abnormality occurs in the bidirectional switch control means, and the DC voltage is applied. Can be prevented from being destroyed.

In the third aspect of the invention, particularly with respect to the direct current power supply device of the first or second aspect of the invention, the load is an inverter and a direct current motor connected to the inverter, and the load amount detecting means is the direct current power source. By detecting the load on the motor, it is possible to improve the power source power factor while maintaining the DC voltage at a voltage at which the efficiency of the DC motor that is the load is optimum, regardless of fluctuations in the AC voltage.

  In particular, the fourth invention uses the DC power supply device according to any one of the first to third inventions as a DC power supply device for a compressor of an air conditioner, and the open / close time selection means b includes an outdoor unit in addition to the load amount. By selecting the open / close time of the bidirectional switch based on the temperature, compressor temperature, and refrigerant discharge temperature information, the optimal DC voltage supply and power supply for the load and operating environment of the compressor motor The improvement in rate can be achieved at the same time.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the present invention is not limited to the embodiments.

(Embodiment 1)
FIG. 1 is a block diagram of a DC power supply device according to a first embodiment of the present invention.

  In FIG. 1, the same components as those in the conventional configuration are denoted by the same reference numerals, and description thereof is omitted. The open / close time selection means a17 compares the DC voltage detected by the DC voltage detection means 14 with the target voltage stored in the target voltage storage means 16 so that the detected value of the DC voltage approaches the target voltage. The opening / closing time of the switch 10 is adjusted and transmitted to the bidirectional switch control means 13, and the bidirectional switch control means 13 is synchronized with the zero cross point detected by the zero cross detection means 12 according to the transmitted opening / closing time. The direction switch 10 is opened and closed. The opening / closing time selection means b19 selects the opening / closing time of the bidirectional switch 10 corresponding to the load amount detected by the load amount detection means 15 from the opening / closing time stored in the opening / closing time storage means 18, and the bidirectional switch The bidirectional switch control means 13 performs an opening / closing operation of the bidirectional switch 10 according to the transmitted opening / closing time. The rectifying means 6 is composed of diodes 2, 3, 4, and 5. Reference numerals 8 and 9 are connected in series with each other, connected in parallel to the output terminal of the rectifying means 6, and the connecting point of the series connection is a voltage doubler voltage boosting capacitor connected to one input terminal of the rectifying means 6.

  By performing the operation as described above, the DC power supply device of the present embodiment can always bring the DC voltage applied to the load 11 close to the target value regardless of the change in the voltage of the AC power supply 1, etc. The optimum DC voltage can be supplied with respect to the quantity, and the power factor can be improved.

  2 and 3, the operating waveform of the DC power supply device of the present embodiment in the state where the AC voltage is 100 V and the AC voltage is 90 V with the same load amount, the switching operation of the bidirectional switch 10 is the power source. The case of twice in a half cycle will be described as an example.

  FIG. 2 is an operation waveform diagram of the present embodiment when the AC voltage Vi is 100V. The closing time a is the closing operation time of the bidirectional switch 10 adjusted by the opening / closing time selection means a17. The opening / closing time selection means a17 increases or decreases the closing time a so that the DC voltage Vdc approaches the target voltage. Yes. Here, since the operation waveform in a state where the load is stable is described, the target voltage and the DC voltage detected by the DC voltage detecting means 14 are substantially the same, and therefore the DC voltage Vdc is detected by the target voltage. Both DC voltages to be used are shown. The closing time b is the closing operation time of the bidirectional switch 10 selected by the opening / closing time selection means b19, and corresponds to the load amount.

FIG. 3 is an operation waveform diagram in a state where the DC power supply device of the present embodiment is stably operated after the AC voltage Vi is changed to 90 V with the same load amount as in FIG. Since the load amount is the same regardless of the decrease in the AC voltage Vi, the target voltage that is a value corresponding to the load amount is also the same as in the case of FIG. However, since the AC voltage has decreased, in order to maintain the DC voltage at the same voltage as in the state of FIG. 2, the open / close time selection means a17 increases the closing time a of the bidirectional switch 10 from the state of FIG. By doing so, it can be seen that the DC voltage is brought close to the target voltage.

(Embodiment 2)
FIG. 4 is a block diagram showing a DC power supply device according to the second embodiment of the present invention. In FIG. 4, the same components as those of FIG. 1 used in the first embodiment are denoted by the same reference numerals, and description thereof is omitted. In the first embodiment, the detected DC voltage is brought close to the target voltage by using the step-up action of the DC voltage by opening and closing the bidirectional switch 10. For example, the bidirectional switch control means 13 When the component abnormality forming the two-way switch occurs, the bidirectional switch 10 maintains the closed state for an unnecessarily long time. As a result, the DC voltage is abnormally boosted, and a DC voltage such as a portion forming the load is applied. There is a risk of damage to the parts due to destruction. Therefore, in the second embodiment of the present invention, the overvoltage protection means 20 stores the threshold value of the DC voltage inside, and when the DC voltage detected by the DC voltage detection means 14 exceeds the threshold value, the switching time selection means. Regardless of the closing time a or the closing time b selected by a17 or the opening / closing time selection means b19, the bidirectional switch 10 is forcibly fixed to the open state to prevent the DC voltage from exceeding the threshold value. is there.

  By performing the operation as described above, it is possible to prevent an excessive increase in the DC voltage accompanying the abnormal operation of the block related to the selection of the open / close time of the bidirectional switch 10 or the control of the open / close operation.

(Embodiment 3)
FIG. 5 is a block diagram showing a DC power supply device according to the third embodiment of the present invention. In FIG. 5, the same components as those of FIG. 1 used in the first embodiment are denoted by the same reference numerals, and description thereof is omitted. In the present embodiment, the load is an inverter 21 and a DC motor 22 directly connected to the inverter 21, and the load amount detection means 15 detects the load of the motor 22. As a general characteristic of the DC motor 22 driven by the inverter 21, it is well known that the motor efficiency improves as the DC voltage decreases, and the maximum rotational speed increases as the DC voltage increases. It has been. In the third embodiment, motor efficiency is improved by setting the target voltage to an optimum DC voltage according to the characteristics of the DC motor that are grasped in advance and the detected load amount. The maximum number of revolutions can be improved by increasing the voltage.

(Embodiment 4)
FIG. 6 is a block diagram showing a DC power supply device according to the fourth embodiment of the present invention. In FIG. 6, the same components as those of FIG. 1 used in the first embodiment are denoted by the same reference numerals, and description thereof is omitted. In the present embodiment, the DC power supply device is a DC power supply device for an air conditioner compressor, and the load is an inverter 21 and a compressor motor 23. The opening / closing time selection means b19 selects the opening / closing time of the bidirectional switch 10 based on the outdoor temperature, the compressor temperature, and the refrigerant discharge temperature information 21 in addition to the load amount, thereby loading the compressor motor 23. In addition, it is possible to achieve both the supply of the optimum DC voltage for the operating environment and the improvement of the power source power factor.

  As described above, the DC power supply device according to the present invention can output the optimum DC voltage according to the load and improve the power factor regardless of the change in the AC voltage. It can also be applied to other uses.

The block diagram which shows the DC power supply device in Embodiment 1 of this invention Operation waveform diagram when AC voltage is 100 V in DC power supply apparatus according to Embodiment 1 of the present invention Operation waveform diagram when AC voltage is 90 V in DC power supply device according to Embodiment 1 of the present invention The block diagram which shows the DC power supply device in Embodiment 2 of this invention The block diagram which shows the DC power supply device in Embodiment 3 of this invention The block diagram which shows the DC power supply device in Embodiment 4 of this invention Block diagram showing a conventional DC power supply

Explanation of symbols

1 AC power supply 6 Rectifying means 7 Reactor 8 Double voltage boosting capacitor a
Nine voltage boost capacitor b
DESCRIPTION OF SYMBOLS 10 Bidirectional switch 11 Load 12 Zero cross detection means 13 Bidirectional switch control means 14 DC voltage detection means 15 Load amount detection means 16 Target voltage storage means 17 Opening / closing time selection means a
18 Opening / closing time storage means 19 Opening / closing time selection means b
20 Overvoltage protection means 21 Inverter 22 Motor

Claims (4)

An AC power supply, a rectifier circuit for rectifying the AC power supply, a reactor connected between the AC power supply and the input end of the rectifier circuit, connected in series to each other, and connected in parallel to the output end of the rectifier circuit; The connection point of the series connection is applied to the voltage doubler voltage boosting capacitor connected to one input terminal of the rectifier circuit, the voltage doubler voltage boosting capacitor and the load connected in parallel to the output terminal of the rectifier circuit, and the load. DC voltage detection means for detecting a DC voltage, zero cross detection means for detecting a zero cross of the AC power supply, a bidirectional switch for short-circuiting the AC power supply via the reactor, and a zero cross point detected by the zero cross detection means And bidirectional switch control means for opening and closing the bidirectional switch in synchronization with the power cycle of the AC power source at least twice in a half cycle of the AC power source, and detecting the load amount. A load amount detecting means for performing the operation, a target voltage storing means for storing a target value of the DC voltage corresponding to the load amount, and a closing time of the bidirectional switch so that the DC voltage detected by the DC voltage detecting means approaches the target voltage. An open / close time selection means a for adjusting at least one of the following, an open / close time storage means for storing the open / close time of the bidirectional switch corresponding to the detected load, and an open / close time stored in the open / close time storage means. An opening / closing time selection means b is provided for selecting the number of times of opening / closing two or more times in the power supply half cycle, and at least one of the two or more times of opening / closing in the power supply half cycle of the bidirectional switch A DC power supply device that is a closing time adjusted by the opening / closing time selection means a and at least once is a closing time selected by the closing time selection means b. 2. An overvoltage protection unit that suppresses boosting of the DC voltage by forcibly fixing the bidirectional switch to an open state regardless of the control state of the bidirectional switch control unit when a DC voltage exceeds a certain value. The direct current power supply device described in 1. 3. The DC power supply apparatus according to claim 1, wherein the load is an inverter and a DC motor connected to the inverter, and the load amount detecting means detects the load of the DC motor. The DC power supply device according to any one of claims 1 to 3 is used as a DC power supply device for a compressor, and the open / close time selection means b includes information on outdoor temperature, compressor temperature, and refrigerant discharge temperature in addition to the load amount. The air conditioner is characterized in that the open / close time of the bidirectional switch is selected based on the above.

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