JP2012114991A - Power supply unit and air conditioner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power supply unit and an air conditioner capable of stably operating regardless of variation in a supply voltage from an AC power source.SOLUTION: A power supply unit 50 of an air conditioner 100 includes: a reactor 2 connected to an AC power source 1 in series; a converter (a diode bridge 3 and electrolytic capacitors 4, 5); a diode bridge 6; a short-circuiting element 7; a voltage phase detecting circuit 8 and a control circuit 11 that controls the short-circuiting circuit 7. The control circuit 11 includes: an estimation section 21 that estimates variation in an AC power source voltage based on a pulse width of a pulse signal from the voltage phase detecting circuit 8; an adjusting section 22 that adjusts a short-circuiting period of the AC power source 1 by the short-circuiting element 7 based on an estimation result of the estimation section 21; and a short-circuiting control section 23 that controls the short-circuiting element 7 so as to make the AC power source 1 short during the short-circuiting period.

Description

  The present invention relates to a power supply device and an air conditioner that convert an AC voltage from an AC power source into a DC voltage and supply the converted voltage to a load.

  Conventionally, as a DC power supply device that converts an AC voltage from an AC power supply into a DC voltage and supplies it to a load, the AC power supply is short-circuited by a reactor for a certain period to improve the power factor or suppress harmonic components. A power supply is known.

  For example, Patent Document 1 (Japanese Patent No. 3734583) discloses a power supply apparatus further including an inverter that converts DC power into AC power by pulse width modulation control in addition to the above configuration. In this power supply device, the short-circuit period is controlled based on the duty ratio of the pulse width modulation control signal that controls the inverter.

  Patent Document 2 (Japanese Patent Laid-Open No. 2005-192266) and Patent Document 3 (Japanese Patent Laid-Open No. 2008-259395) disclose that short-circuiting of an AC power supply is started from the time when a zero-cross point of the AC power supply is detected. is doing.

Japanese Patent No. 3734583 JP 2005-192266 A JP 2008-259395 A

  In the power supply device having the above-described configuration, when the power supply voltage of the AC power supply decreases, the DC voltage at no load obtained by rectifying the AC voltage also decreases. On the other hand, if the target value of the DC voltage does not change, the DC voltage increase width (boost width) by the short-circuit means must be increased.

  However, increasing the boosting width may cause problems such as a deterioration in power factor or an increase in harmonic components. When the AC voltage of the AC power source increases, the DC voltage at no load also increases. However, in this case, if the target value of the DC voltage does not change, for example, a problem such as deterioration of the power factor. Can occur.

  The above Patent Documents 1 to 3 do not disclose the possibility that the power supply voltage from the AC power supply fluctuates, and therefore do not disclose a specific solution to such a problem.

  The objective of this invention is providing the power supply device and air conditioner which can operate | move stably irrespective of the fluctuation | variation of the power supply voltage from AC power supply.

  A power supply device according to an aspect of the present invention includes a converter that converts an AC power supply voltage from an AC power supply into a DC voltage, a reactor connected in series to the AC power supply, and a short circuit that short-circuits the AC power supply through the reactor. A voltage phase detection circuit for detecting a phase of the AC power supply voltage when the AC power supply voltage reaches a predetermined phase detection reference voltage and outputting a pulse signal having a pulse width corresponding to the detected phase; and a voltage phase A control circuit that controls the short circuit based on the pulse signal from the detection circuit, the control circuit estimating the fluctuation of the AC power supply voltage based on the pulse width of the pulse signal, and the estimation unit Based on the results, the short circuit controls the short circuit so that the short circuit shorts the AC power supply during the short circuit period adjusted by the adjustment unit and the adjustment unit adjusting the short circuit period to short the AC power supply That and a short-circuit control unit.

  Preferably, the estimation unit estimates the AC power supply voltage based on a predetermined relationship between the pulse width and the AC power supply voltage. The adjustment unit is set by a target voltage setting unit that sets a target voltage that is a target value of the DC voltage and a target voltage setting unit by comparing the AC power supply voltage estimated by the estimation unit and the reference level of the AC power supply voltage. And a short-circuit period setting unit that sets a short-circuit period based on the target voltage. The target voltage setting unit, when the AC power supply voltage estimated by the estimation unit is larger than the reference level of the AC power supply voltage, makes the target voltage higher than the reference target voltage of the DC voltage, while being estimated by the estimation unit. If the AC power supply voltage is smaller than the reference level, the target voltage is set lower than the reference target voltage.

  Preferably, the power supply device further includes a DC voltage detection circuit for detecting a DC voltage output from the converter. When the target voltage is lower than the DC voltage detected by the DC voltage detection circuit, the short-circuit period setting unit detects the DC voltage detection circuit while shortening the short-circuit period shorter than the currently set period. When the target voltage is larger than the DC voltage, the short-circuit period is made longer than the currently set period.

  Preferably, the power supply device supplies a DC voltage to the inverter. The inverter converts the DC voltage from the power supply device into an AC voltage to drive the motor.

  An air conditioner according to another aspect of the present invention includes the power supply device described above, an inverter that converts a DC voltage supplied from the power supply device into an AC voltage, and a motor that is driven by the AC voltage from the inverter.

  ADVANTAGE OF THE INVENTION According to this invention, a power supply device and an air conditioner can be operated stably irrespective of the fluctuation | variation of the power supply voltage from AC power supply.

It is the circuit diagram which showed the structure of the air conditioner provided with the power supply device which concerns on embodiment of this invention. FIG. 2 is a block diagram illustrating configurations of an estimation unit 21 and a short-circuit period adjustment unit 22 illustrated in FIG. 1. It is the conceptual diagram which showed the relationship between an alternating current power supply voltage and the pulse signal output from a voltage phase detection circuit. It is a flowchart for demonstrating adjustment of the short circuit period by a short circuit period adjustment part.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings for understanding of the present invention. The following embodiment is an example embodying the present invention, and is not intended to limit the technical scope of the present invention. The same reference numerals are used for the same and corresponding parts, and the description thereof will not be repeated in principle.

  FIG. 1 is a circuit diagram illustrating a configuration of an air conditioner including a power supply device according to an embodiment of the present invention. Referring to FIG. 1, an air conditioner 100 includes a power supply device 50 that converts an AC voltage from an AC power supply 1 (for example, a commercial power supply) into a DC voltage, and a DC voltage from the power supply device 50 that is an AC voltage (in this example). An inverter circuit 10 for converting to a three-phase AC voltage) and a compressor 12 including a motor 13 driven by the AC voltage from the inverter circuit 10.

  The power supply device 50 includes a reactor 2 having one end connected to one output end of the AC power source 1, a diode bridge 3 connected to the other end of the reactor 2 and the other output end of the AC power source 1, and an electrolytic capacitor 4. , 5. The diode bridge 3 rectifies an AC voltage (hereinafter also referred to as “AC power supply voltage” or simply “power supply voltage”) from the AC power supply 1 into a DC voltage. The electrolytic capacitors 4 and 5 smooth the DC voltage output from the diode bridge 3. Diode bridge 3 and electrolytic capacitors 4 and 5 constitute a converter that converts an AC power supply voltage from AC power supply 1 into a DC voltage.

  The DC voltage Vdc output from the converter is supplied to the inverter circuit 10. The inverter circuit 10 converts the DC voltage Vdc into a three-phase AC voltage, and drives the motor 13 with the three-phase AC voltage.

  The power supply device 50 further includes a diode bridge 6, a short-circuit element 7, and a control circuit 11. One input terminal of the diode bridge 6 is connected to one output terminal of the AC power supply 1 through the reactor 2. The other input end of the diode bridge 6 is connected to the other output end of the AC power supply 1.

  The short-circuit element 7 is a switch element such as a bipolar transistor, IGBT, or MOSFET, and is connected to one and the other output terminals of the diode bridge 6. The short-circuit element 7 is turned on / off by the control circuit 11. When the short-circuit element 7 is turned on, the two output ends of the diode bridge 6 are short-circuited. As a result, one and the other output terminals of the AC power supply 1 are short-circuited via the reactor 2 and the diode bridge 6, and the power factor of the power supply device can be improved.

  The power supply device 50 further includes a voltage phase detection circuit 8 and a DC voltage detection circuit 9. The voltage phase detection circuit 8 detects the phase of the AC power supply voltage when the AC power supply voltage reaches a predetermined phase detection reference voltage, and outputs a pulse signal having a pulse width corresponding to the detected phase. The DC voltage detection circuit 9 detects the DC voltage Vdc output from the converter.

  The control circuit 11 is realized by a microcomputer (microcomputer), for example. The control circuit 11 includes an estimation unit 21, a short-circuit period adjustment unit 22, a short-circuit element control unit 23, and an inverter control unit 24.

  The short-circuit element control unit 23 controls on / off of the short-circuit element 7. The on-period of the short-circuit element 7, that is, the short-circuit period of the AC power supply 1 is adjusted by the short-circuit period adjusting unit 22. For example, the short-circuit element control unit 23 short-circuits the short-circuit element 7 for a predetermined time in each cycle of the power supply voltage. Further, the short-circuit element control unit 23 determines the timing for starting the short-circuit of the AC power supply 1 by the short-circuit element 7 by detecting the edge of the pulse signal from the voltage phase detection circuit 8.

  The estimation unit 21 estimates fluctuations in the AC power supply voltage output from the AC power supply 1 based on the pulse width of the pulse signal sent from the voltage phase detection circuit 8. The short-circuit period adjusting unit 22 adjusts the short-circuit period based on the estimation result of the estimation unit 21 and the output from the DC voltage detection circuit 9.

  The inverter control unit 24 performs pulse width modulation (PWM) control on the inverter circuit 10. Thereby, the inverter circuit 10 converts the DC voltage Vdc into a three-phase AC voltage. At that time, the pulse width may be adjusted based on the output from the DC voltage detection circuit 9.

  FIG. 2 is a block diagram illustrating the configuration of the estimation unit 21 and the short-circuit period adjustment unit 22 illustrated in FIG. Referring to FIG. 2, estimation unit 21 includes a power supply voltage estimation unit 31, a table 32, and a comparison unit 33. The table 32 predefines the correspondence between the pulse width of the pulse signal output from the voltage phase detection circuit 8 and the power supply voltage. The power supply voltage estimation unit 31 estimates the AC power supply voltage using the pulse signal output from the voltage phase detection circuit 8 and the table 32.

FIG. 3 is a conceptual diagram showing the relationship between the AC power supply voltage and the pulse signal output from the voltage phase detection circuit. Referring to FIG. 3, even when the AC power supply voltage fluctuates, the power supply frequency is kept constant. Therefore, the period T ₀ of the AC power supply voltage is also constant.

The phase detection reference voltage for detecting the voltage phase is set to a predetermined voltage different from 0V. AC power supply voltage is expressed as T ₁ in FIG. 3 the time to reach the phase detection reference voltage for the voltage phase detection after passing the 0V. AC power supply voltage becomes shorter time becomes higher than the standard voltage T _1. Conversely, an AC power supply voltage becomes longer time T ₁ becomes lower than the standard voltage. That is, the phase of the AC power supply voltage when the AC power supply voltage reaches the phase detection reference voltage depends on the magnitude of the AC power supply voltage.

In the example described in FIG. 3, when the AC power supply voltage becomes higher than the phase detection reference voltage, the output waveform of the voltage phase detection circuit 8 rises and becomes a Hi output, while the AC power supply voltage is higher than the phase detection reference voltage. When the voltage becomes lower, the output waveform of the voltage phase detection circuit 8 falls and becomes a Low output. The time T ₂ is the time from the rise to the fall of the output waveform of the voltage phase detection circuit 8 and corresponds to the pulse width of the pulse signal output from the voltage phase detection circuit 8. The period T ₀ is constant, and the time T ₁ changes according to the power supply voltage. Therefore, the time T ₂ are made longer as the power supply voltage is high, becomes higher the power supply voltage is low short.

  When the AC power supply voltage becomes higher than the phase detection reference voltage, the output waveform of the voltage phase detection circuit 8 becomes a Low output, and when the AC power supply voltage becomes lower than the phase detection reference voltage, the voltage phase detection is performed. The output waveform of the circuit 8 may be a Hi output. In the example shown in FIG. 3, the phase detection reference voltage is set to a positive voltage, but the phase detection reference voltage may be set to a negative voltage depending on the polarity of the circuit.

Returning to FIG. 2, in the embodiment of the present invention, the power supply voltage is estimated using the relationship shown in FIG. Table 32 is obtained by predefined relationship between time T ₂ and the AC power supply voltage. This relationship can be obtained in advance by, for example, experiments. Power supply voltage estimation unit 31 from the table 32 and the time _{T 2,} to estimate the supply voltage. The comparison unit 33 compares the power supply voltage estimated by the power supply voltage estimation unit 31 with a reference value. The reference value is a standard voltage value. Thereby, the fluctuation of the power supply voltage is estimated.

  Thus, by estimating the power supply voltage using the width of the pulse signal output from the voltage phase detection circuit 8, the value of the power supply voltage can be grasped without the need to add a circuit component for measuring the power supply voltage. can do.

  Furthermore, when the load varies due to the operation of the air conditioner, the DC voltage Vdc varies. In the case of no load, the value of √2 times the power supply voltage is the value of the DC voltage. Therefore, if there is no load, the power supply voltage can be easily estimated from the value of the DC voltage Vdc detected by the DC voltage detection circuit 9. However, the DC voltage Vdc decreases during operation of the air conditioner. The amount of decrease in DC voltage can vary depending on the environment or temperature around the air conditioner. For this reason, it is difficult to estimate the power supply voltage from the DC voltage Vdc detected by the DC voltage detection circuit 9. However, according to the embodiment of the present invention, it is possible to estimate the power supply voltage even when the load fluctuates due to the operation of the air conditioner.

  On the other hand, the short circuit period adjustment unit 22 includes a target voltage setting unit 41 and a short circuit period setting unit 42. The target voltage setting unit 41 sets a target value (target voltage) of the DC voltage Vdc detected by the DC voltage detection circuit 9. Specifically, when the estimation unit 21 estimates that the power supply voltage is greater than the standard voltage (reference value), the target voltage setting unit 41 sets the target voltage to the target value when the power supply voltage is the standard voltage. Higher than the reference target voltage. Conversely, when the estimation unit 21 estimates that the power supply voltage is smaller than the reference voltage, the target voltage setting unit 41 makes the target voltage lower than the reference target voltage. The reference target voltage is an experimentally determined value, and may be larger or smaller than the value of the DC voltage when the power supply voltage is equal to the standard voltage and no load is applied.

  When the target voltage is lower than the DC voltage Vdc detected by the DC voltage detection circuit 9, the short-circuit period setting unit 42 shortens the short-circuit period from the currently set period. Conversely, when the target voltage is larger than the DC voltage Vdc detected by the DC voltage detection circuit 9, the short circuit period setting unit 42 makes the short circuit period longer than the currently set period.

  FIG. 4 is a flowchart for explaining the adjustment of the short circuit period by the short circuit period adjustment unit. Referring to FIGS. 3 and 4, in step S <b> 1, target voltage setting unit 41 receives an estimation result of fluctuations in power supply voltage by estimation unit 21. The target voltage setting unit 41 determines whether or not the estimation result indicates that the power supply voltage is higher than the reference level.

  If the power supply voltage is higher than the reference level (YES in step S1), the process proceeds to step S2. In step S2, the target voltage setting unit 41 makes the target value (target voltage) of the DC voltage Vdc higher than the reference target voltage.

  On the other hand, when the power supply voltage is lower than the reference level (NO in step S1), the process proceeds to step S3. In step S3, the target voltage setting unit 41 makes the target voltage lower than the reference target voltage. After the process of step S2 or S3, the process of step S4 is executed.

  In step S <b> 4, the short circuit period setting unit 42 acquires the detected value of the DC voltage Vdc from the DC voltage detection circuit 9. In step S5, the short circuit period setting unit 42 determines whether or not the target voltage is larger than the detected DC voltage by comparing the detected value of the DC voltage Vdc with the target value (target voltage).

  If the target voltage is larger than the detected DC voltage (YES in step S5), the process proceeds to step S7. In step S7, the short circuit period setting unit 42 makes the short circuit period longer than the currently set period.

  On the other hand, when the target voltage is smaller than the detected DC voltage (NO in step S5), the process proceeds to step S6. In step S6, the short circuit period setting unit 42 makes the short circuit period shorter than the currently set period. In order to prevent the short-circuit period from changing abruptly, it is preferable to change the short-circuit period by a constant value every certain time. Further, in order to determine the amount of change in the short-circuit period, the short-circuit period setting unit 42 may store, for example, a table representing the relationship between the detected DC voltage and target voltage difference and the amount of change in the short-circuit period. Good.

  The process of FIG. 4 will be described more specifically. In addition, the numerical value shown below was used in order to make an understanding of this invention easy, and does not limit this invention.

  Since the DC voltage at no load is √2 times the power supply voltage from the AC power supply 1, the DC voltage at no load can be roughly calculated from the power supply voltage. For example, if the power supply voltage is 200V, the DC voltage at no load is 280V, and if the power supply voltage is 180V, the DC voltage at no load is 252V.

  The target voltage of the DC voltage when the power supply voltage is 200 V (standard voltage) and the rotation speed of the compressor 12 is 3000 rpm is, for example, 280 V. The DC voltage Vdc is lowered by the load (compressor 12), and the detected value of the DC voltage Vdc is acquired (step S4). The target voltage is larger than the detected DC voltage (YES in step S5). For this reason, in order to boost the detected DC voltage Vdc (increase the voltage), the short-circuit period is made longer than the currently set period (step S7).

  During the short-circuit period set as described above, the short-circuit element 7 is turned on, so that the DC voltage Vdc is boosted by a reduced amount. Thereby, the DC voltage Vdc can be made equal to the target value. If the DC voltage Vdc detected in step S4 exceeds the target voltage, the process proceeds to step S6. In step S6, in order to step down the detected DC voltage Vdc (lower the voltage), the short-circuit period is made shorter than the currently set period.

  On the other hand, when the power supply voltage is estimated to be 180V by the estimation unit 21, the power supply voltage (180V) is lower than the reference level (200V). In this case (NO in step S1), the target voltage is lowered from the reference voltage (280V) (step S3). In step S3, the target voltage is set to 260V, for example. Thereafter, the processes of steps S4, S5, S6 (or S7) are executed, and a short circuit period is set. During the short-circuit period, the short-circuit element 7 is turned on, so that the boost width of the DC voltage Vdc can be set to the same level as the above-described boost width.

  As described above, according to the embodiment of the present invention, the fluctuation of the AC power supply voltage can be estimated based on the pulse width of the pulse signal output from the voltage phase detection circuit. Therefore, it is possible to estimate the fluctuation of the voltage of the AC power supply without adding parts to the power supply device.

  According to the embodiment of the present invention, the target value of the DC voltage can be set to an appropriate value based on the estimated fluctuation of the power supply voltage. As a result, when the power supply voltage of the AC power supply fluctuates, the short-circuiting time can be determined so as to obtain an optimum DC voltage considering power factor or harmonic components. For example, when the power supply voltage is lower than the reference level, the target voltage is set lower than the reference target voltage. Thereby, since the boosting width of the DC voltage can be set to an appropriate size, the possibility of occurrence of problems such as deterioration of power factor or increase of harmonic components due to increase of the boosting width can be reduced.

  As described above, according to the embodiment of the present invention, it is possible to realize a power supply device and an air conditioner that are resistant to fluctuations in the AC power supply voltage without increasing costs.

Incidentally, for example, in the present embodiment, although estimates the supply voltage from the table 32 and the time T _2, may be estimated power supply voltage from a calculation in which the time T ₂ as a variable.

  The embodiment disclosed this time must be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  DESCRIPTION OF SYMBOLS 1 AC power supply, 2 Reactor, 3, 6 Diode bridge, 4,5 Electrolytic capacitor, 7 Short circuit element, 8 Voltage phase detection circuit, 9 DC voltage detection circuit, 10 Inverter circuit, 11 Control circuit, 12 Compressor, 13 Motor, 21 Estimating unit, 22 Short-circuit period adjusting unit, 23 Short-circuit element control unit, 24 Inverter control unit, 31 Power supply voltage estimating unit, 32 Table, 33 Comparison unit, 41 Target voltage setting unit, 42 Short-circuiting period setting unit, 50 Power supply device, 100 Air conditioner.

Claims (5)

A converter that converts an AC power supply voltage from an AC power supply into a DC voltage;
A reactor connected in series to the AC power source;
A short circuit that short-circuits the AC power supply through the reactor;
A voltage phase detection circuit that detects a phase of the AC power supply voltage when the AC power supply voltage reaches a predetermined phase detection reference voltage, and outputs a pulse signal having a pulse width corresponding to the detected phase;
A control circuit for controlling the short circuit based on the pulse signal from the voltage phase detection circuit;
The control circuit includes:
Based on the pulse width of the pulse signal, an estimation unit that estimates fluctuations in the AC power supply voltage;
Based on the estimation result of the estimation unit, an adjustment unit that adjusts a short circuit period in which the short circuit short-circuits the AC power supply; and
And a short-circuit control unit that controls the short-circuit circuit so that the short-circuit circuit short-circuits the AC power supply during the short-circuit period adjusted by the adjustment unit. The estimation unit estimates the AC power supply voltage based on a predetermined relationship between the pulse width and the AC power supply voltage,
The adjustment unit is
A target voltage setting unit that sets a target voltage that is a target value of the DC voltage by comparing the AC power supply voltage estimated by the estimation unit with a reference level of the AC power supply voltage;
A short-circuit period setting unit for setting the short-circuit period based on the target voltage set by the target voltage setting unit,
The target voltage setting unit is configured to make the target voltage higher than the reference target voltage of the DC voltage when the AC power supply voltage estimated by the estimation unit is higher than a reference level of the AC power supply voltage. 2. The power supply device according to claim 1, wherein when the AC power supply voltage estimated by the estimation unit is smaller than the reference level, the target voltage is made lower than the reference target voltage. The power supply device further includes a DC voltage detection circuit for detecting the DC voltage output from the converter,
When the target voltage is smaller than the DC voltage detected by the DC voltage detection circuit, the short-circuit period setting unit makes the short-circuit period shorter than the currently set period, while the DC voltage The power supply device according to claim 2, wherein when the target voltage is larger than the DC voltage detected by a detection circuit, the short-circuit period is made longer than a currently set period. The power supply device supplies a DC voltage to the inverter,
The power supply device according to claim 1, wherein the inverter converts a DC voltage from the power supply device into an AC voltage to drive a motor. A power supply device according to claim 1;
An inverter that converts a DC voltage supplied from the power supply device into an AC voltage;
An air conditioner comprising: a motor driven by an AC voltage from the inverter.

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