JP2009261077A - Alternating current-direct current converter, compressor driving device, and air conditioner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an alternating current-direct current converter that inexpensively detects unbalance in capacitor voltage. <P>SOLUTION: The converter includes: capacitors 6, 7 connected in series between the outputs of a rectifier 2; a bidirectional switch 3 placed between one input terminal of the rectifier 2 and the point of junction between the capacitors 6, 7; a bidirectional switch 4 placed between the other input terminal of the rectifier 2 and the point of junction between the capacitors 6, 7; a voltage detector 30 that detects voltage between ends of the capacitors 6, 7; a voltage detector 31 that detects the voltage of the capacitor 7 positioned on the lower potential side of the capacitors 6, 7; and a control unit 20 that operates the two bidirectional switches 3, 4 to control the output voltage to a desired output voltage value during a half period of an alternating-current power supply 1. The control unit 20 includes a voltage detection unit 32 that is connected on the ground side with the negative pole side of the rectifier 2 in a non-isolated manner and detects the voltage of the capacitor 6 on the higher potential side from the difference between the detected voltage from the voltage detector 30 and the detected voltage from the voltage detector 31. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an AC / DC converter that suppresses harmonic current and controls a DC voltage, a compressor driving apparatus using the apparatus, and an air conditioner.

  As a conventional AC / DC converter, it synchronizes with the power supply by means of a zero-cross signal of the power supply voltage, etc., and short-circuits the power supply only once every half cycle to cause the current to flow through the reactor, thereby suppressing the harmonic current and improving the power factor (For example, refer to Patent Document 1).

  Further, since the reactor is enlarged when the power supply is short-circuited only once in a half cycle of the power supply, some reactors are miniaturized by performing a short-circuit operation twice or more in a half cycle of the power supply (see, for example, Patent Document 2). .

  Further, there is a switch means for switching between full-wave rectification and voltage doubler rectification, and a switch means for short-circuiting the power supply, and there are some which control the two switch means to suppress the harmonic current and improve the power factor ( For example, see Patent Documents 3 and 4).

  Some switch means are operated by high-frequency PWM to control the input current in a substantially sinusoidal shape to suppress harmonics and improve the power factor (see, for example, Patent Document 5).

  Furthermore, there are some that attempt to suppress the harmonic current by operating two switching elements (see, for example, Non-Patent Document 1).

Japanese Patent No. 2763479 Japanese Patent No. 3485047 JP 2003-9535 A Japanese Patent No. 3687641 Japanese Patent No. 2140103 (Japanese Patent Publication No. 7-89743) Shinichi Hoshi, Kuniomi Oguchi, “Switching pattern determination method for single-phase multi-level rectifier circuit”, H17 Annual Conference of the Institute of Electrical Engineers of Japan, No. 1-61

  The method of causing the short circuit current to flow by operating the switch means every half cycle of the power supply is very simple control. The operation of the switch means in the half cycle of the power supply is low frequency switching at 100 Hz or 120 Hz, and the generated noise is also generated. It has been widely put into practical use as a method that can reduce harmonic currents at low cost.

  However, the limit value is determined for the harmonic current included in the input current flowing in from the power source, and it is necessary to suppress it below the limit value. There was a problem of increasing the size.

  Therefore, it is described in Non-Patent Document 1 that the level of the input voltage of the rectifier is increased by two switch means and the harmonics of the input current are suppressed. Although there is an advantage that it is possible to reduce the size, since a smoothing capacitor connected in series is required, it is necessary to use a control for monitoring and protecting and balancing the voltage so that each smoothing capacitor does not exceed the withstand voltage.

  Furthermore, in the method of Non-Patent Document 1, if a difference occurs between the voltages of the upper and lower smoothing capacitors due to the influence of the capacitance variation of the capacitors, the harmonics of the power supply current increase, and thus it is necessary to keep this voltage in balance. There was a problem.

  The present invention has been made to solve the above-described problems, and a first object thereof is to obtain an AC / DC converter that detects an unbalance of capacitor voltage at low cost.

  Furthermore, the second object is to obtain an AC / DC converter capable of suppressing power supply harmonics by balancing the voltages of smoothing capacitors connected in series, and reducing the reactor size and realizing cost reduction. is there.

  An AC / DC converter according to the present invention includes a rectifier connected to an AC power source via a reactor, a plurality of capacitors connected in series between output terminals of the rectifier, one input terminal of the rectifier, and a plurality of capacitors. A first bidirectional switch inserted between the connection points, a second bidirectional switch inserted between the other input terminal of the rectifier and the connection points of the capacitors, and both ends of the capacitors A first voltage detecting means for detecting a voltage between them, a second voltage detecting means for detecting a voltage of a capacitor located on the low potential side of the plurality of capacitors, and a high potential side of the plurality of capacitors. Third voltage detection means for detecting the voltage of the capacitor, and control means for operating both the first and second bidirectional switches to control to a desired output voltage value during a half cycle of the AC power supply And the ground side of the control means is connected to the negative side of the rectifier in a non-insulated manner, and the third voltage detection means is high from the difference between the detection voltage of the first voltage detection means and the detection voltage of the second voltage detection means. The voltage of the capacitor located on the potential side is detected.

  According to the present invention, the voltage across the plurality of capacitors is detected by the first voltage detection means, the voltage of the capacitor located on the low potential side among the plurality of capacitors is detected by the second voltage detection means, The voltage of the capacitor located on the high potential side is detected from the difference between the detection voltage of the first voltage detection means and the detection voltage of the second voltage detection means by the third voltage detection means. Withstand voltage protection and voltage balance control are possible, and the reactor can be miniaturized. In addition, since voltage imbalance of a plurality of capacitors can be suppressed by feedback, voltage fluctuations of the plurality of capacitors can be suppressed, and smoke and ignition of the circuit due to aging deterioration of the capacitor capacity can be prevented.

  Further, since the ground side of the control means is connected to the negative side of the rectifier in a non-insulated manner, it is not necessary to insulate the voltage detection signal based on the detection voltage of the first and second voltage detection means, and the detection circuit is simplified. The device can be configured at low cost.

Embodiment 1 FIG.
FIG. 1 is a circuit diagram of an AC / DC converter according to Embodiment 1 of the present invention.
1 includes a rectifier 2 connected to an AC power source 1 via a reactor 5, a first bidirectional switch 3 having one end connected to one input terminal of the rectifier 2, and one end being The second bidirectional switch 4 connected to the other input terminal of the rectifier 2 and the output terminal of the rectifier 2 are connected in series, and the connection point of each of the first and second bidirectional switches 3 and 4 The first and second capacitors 6 and 7 connected to the other end, the control unit 20 formed of a microcomputer having an A / D converter, for example, and the first and second capacitors 6 and 7 in series between both ends The first voltage detector 30 composed of two connected resistors, the second voltage detector 31 composed of two resistors connected in series between both ends of the second capacitor 7, and the voltage of the AC power source 1. The zero cross point is detected and the information is sent to the control unit 20 Power supply phase detector 33, an interface circuit 34 for supplying the switching output signal from the control unit 20 to the first bidirectional switch 3, and a switching output signal from the control unit 20 to the second bidirectional switch 4. And an interface circuit 35. In this AC / DC converter, a DC load 8 is connected between output terminals.

  The rectifier 2, the second capacitor 7, the first and second voltage detectors 30 and 31, and the DC load 8 are each connected to a low potential side terminal. In the reactor 5 described above, a non-magnetic material for suppressing the reactor sound is inserted in the gap portion of the magnetic flux, and the first bidirectional switch 3 includes, for example, an IGBT 3a and a diode rectifier 3b. The direction switch 4 includes an IGBT 4a and a diode rectifier 4b as described above. The first voltage detector 30 divides the voltage Vo between both ends of the first and second capacitors 6 and 7 on the low potential side and outputs the divided voltage Vo to the control unit 20. The second voltage detector 31 The voltage Vd <b> 2 across the two capacitors 7 is divided on the low potential side and output to the control unit 20.

  The control unit 20 includes a third voltage detection unit 32 whose ground side is connected to the negative electrode side of the rectifier 2 in a non-insulated manner and detects the voltage of the first capacitor 6 located on the high potential side. . The third voltage detector 32 is composed of, for example, a subtracter, and is digitized by the detected voltage Vo of the first voltage detector 30 digitized by the A / D converter and the other A / D converter. The voltage Vd1 of the first capacitor 6 located on the high potential side is detected from the difference from the detected voltage Vd2 of the second voltage detector 31. The calculation of the voltage Vd1 of the first capacitor 6 by the subtractor (third voltage detection unit 32) is performed because the control unit 20 that is a microcomputer is connected to the negative electrode side of the rectifier 2 without being insulated. This is because the A / D converter that is used is also of a non-insulating type, so that the voltage Vd1 of the first capacitor 6 on the high potential side cannot be directly detected.

Here, the basic operation of the AC / DC converter under the control of the control unit 20 will be described with reference to FIGS.
2 is a circuit diagram in an ideal state for explaining the first embodiment, FIG. 3 is a waveform diagram showing the principle operation for explaining the first embodiment, and FIG. 4 is a circuit diagram showing an operation mode in the first embodiment. FIG. 5 is a diagram for explaining an operation at the time of voltage imbalance in the first embodiment.

  When the input voltage of the rectifier 2 in FIG. 1 is the converter voltage Vc, the relationship between the voltage Vs of the AC power supply 1 and the input current Is is as shown in FIG. In general, the control unit 20 that suppresses the harmonic current controls the input current Is of the AC / DC converter so as to have a sine wave shape, so that the converter voltage Vc is also substantially sinusoidal in synchronization with the frequency of the AC power source 1. The voltage waveform is The substantially sinusoidal voltage is realized by controlling the first bidirectional switch 3 (hereinafter abbreviated as “Sa”) and the second bidirectional switch 4 (hereinafter abbreviated as “Sb”) shown in FIG. The This is determined by the operating states of the first and second bidirectional switches 3 and 4 and the polarity of the input current Is, and specifically, eight types of operation modes shown in FIGS. Are combined to generate a sine-wave converter voltage Vc shown in FIG.

  As shown in FIG. 4A, when the first and second bidirectional switches Sa and Sb are simultaneously turned on (power supply short-circuit mode), the input terminals of the rectifier 2 are short-circuited because the input terminals of the rectifier 2 are short-circuited. The converter voltage Vc on the side becomes Vc = 0. The voltage waveform at this time is a voltage in the period (1) shown in FIG.

  Next, as shown in (b), when the first bidirectional switch Sa is turned on and the second bidirectional switch Sb is turned off (first voltage rectification mode), the input side of the rectifier 2 is turned on. Since the converter voltage Vc is equal to the voltage Vd2 across the second capacitor 7, it is ½ of the DC voltage Vo. The voltage waveform at this time is the period (2) shown in FIG.

  Further, as shown in (c), when the first bidirectional switch Sa is turned OFF and the second bidirectional switch Sb is turned ON (second voltage doubler rectification mode), the input side of the rectifier 2 is turned on. Since the converter voltage Vc is equal to the voltage Vd1 across the first capacitor 6, the converter voltage Vc is ½ of the DC voltage Vo as in FIG. 4B. The voltage waveform at this time is the period (2) as described above. In the first and second voltage doubler rectification modes, the magnitude relationship between the charging voltages of the first and second capacitors 6 and 7 and the polarity of the power supply current (input current Is) detected by the power supply phase detector 33 are determined. It is determined based on. Alternatively, the polarity of the power supply current may be estimated from the phase detected by the power supply phase detector 33 and determined from the magnitude relationship between the charging voltages of the first and second capacitors 6 and 7.

  As shown in (d), when the first and second bidirectional switches Sa and Sb are simultaneously turned off (full-wave rectification mode), the converter voltage Vc on the input side of the rectifier 2 is in the full-wave rectification state. Therefore, the converter voltage Vc on the input side of the rectifier 2 is equal to Vo which is the voltage across the first and second capacitors 6 and 7. The voltage waveform at this time is the period (3) shown in FIG.

  (E) to (h) shown in FIG. 4 are also the same operations as described above, except that the polarity of the AC power supply 1 is different. The fact that only the direction of the converter voltage Vc has not changed indicates that the polarity (direction) of the converter voltage Vc, in other words, when the polarity of the voltage Vs of the AC power supply 1 is negative, the converter voltage Vc is also negative. Because. Therefore, it is possible to obtain a period (2 ') in which the voltage waveform when the polarity is negative is opposite to Vc = -Vo / 2 and a period (3') in which Vc = -Vo.

  The voltage waveform periods (1) to (3) and (1 ′) to (3 ′) described above are unit times (1) of the switching pattern divided by the charging paths to the first and second capacitors 6 and 7. It is obtained by calculating the generation time ratio per period) and appropriately controlling the switching output signals to the first and second bidirectional switches 3 (Sa) and 4 (Sb) for each unit time based on this. It is done. Note that the number of occurrences of the full-wave rectification mode, the first voltage doubler rectification mode, the second voltage doubler rectification mode, and the power supply short-circuit mode controlled by the control unit 20 is twice within the unit time for controlling the switching mode. ing.

  In addition, the control unit 20 generates the voltage Vd2 of the second capacitor 7 detected by the second voltage detector 31 when the input side of the rectifier 2 is generated in a sine wave shape, and a third subtractor. The first and second bidirectional switches 3 and 4 are controlled so that the difference from the voltage Vd1 of the first capacitor 6 calculated by the voltage detector 32 becomes smaller. When the voltage Vd1 of the first capacitor 6 of the first and second capacitors 6 and 7 reaches the maximum rated voltage of the capacitor as shown in FIG. 5, for example, the first and second bidirectional capacitors are used. The switching control of the switches 3 and 4 is stopped.

  As described above, according to the first embodiment, Vo (Vd1 + Vd2) is detected by the first voltage detector 30, the voltage Vd2 is detected by the second voltage detector 31, and these are detected by the A / After the data is acquired by the D converter, the voltage Vd1 is detected by calculation by the third voltage detector 32 as a subtractor, so that the withstand voltage protection and voltage balance of the first and second capacitors 6 and 7 are detected. Control becomes possible and the reactor 5 can be reduced in size. In addition, since voltage imbalance of the first and second capacitors 6 and 7 can be suppressed by feedback, voltage fluctuations of the first and second capacitors 6 and 7 can be suppressed, and a circuit due to deterioration of the capacitor capacity over time. Can prevent smoke and fire.

  Further, since the control unit 20 and the first and second voltage detectors 30 and 31 are connected to the same ground side, a voltage detection signal based on the detection voltage of the first and second voltage detectors 30 and 31. Therefore, the detection circuit can be configured simply and the present apparatus can be realized at low cost.

  In the first embodiment, it has been described that the first and second bidirectional switches 3 and 4 are composed of IGBTs and diode rectifiers. However, the present invention is not limited to this. For example, FIG. As shown, the first switching element 60 and the first diode 61 connected in series to flow current in one direction are connected in parallel to the first switching element 60 and the first diode 61, and the current flows in the reverse direction. A bidirectional switch composed of a second switching element 62 and a second diode 63 connected in series may be used.

Embodiment 2. FIG.
FIG. 6 is a circuit diagram of an AC / DC converter according to Embodiment 2 of the present invention. In addition, the same code | symbol is attached | subjected to the part which is the same as that of Embodiment 1 demonstrated in FIG. 1, or an equivalent, and description is abbreviate | omitted.
6 includes a second rectifier 40 connected in parallel to an AC power source 1 via a reactor 5 and a rectifier 2 (hereinafter referred to as “first rectifier 2”), and a second rectifier. 40, the first switching element 41 (SW1) inserted between the positive electrode side of 40 and the connection point of the first and second capacitors 6, 7, the negative electrode side of the second rectifier 40 and the first and second The second switching element 42 (SW2) inserted between the connection points of the capacitors 6 and 7 and the control unit 20 having the converter voltage calculation unit 26 and the operation signal generation unit 27 are provided.

The converter voltage calculation unit 26 of the control unit 20 includes the power supply phase based on the zero cross information detected by the power supply phase detector 33, the DC voltage command Vd ^* , the voltage Vo between the output terminals of the first rectifier 2, and the first capacitor. The operation mode (mode) and the modulation rate command are calculated based on each information of the voltage Vd1 of 6. The operation signal generator 27 generates a PWM switching output signal based on the operation mode calculated by the converter voltage calculator 26 and the PWM (pulse width modulation) duty (pulse ON / OFF ratio), and the interface circuit 34. , 35 to the first and second switching elements 41 (SW1) and 42 (SW2).

  Next, the converter voltage calculation unit 26 described above will be described with reference to FIGS. 7 is a block diagram showing the configuration of the converter voltage calculation unit in the second embodiment, FIG. 8 is a diagram showing the relationship between the switching states of the first and second switching elements and the capacitor voltage in the second embodiment, and FIG. These are the figures which show the production | generation method of the switching pattern in Embodiment 2. FIG.

When the DC voltage command Vd ^* and the DC voltage Vo (Vd1 + Vd2) are input, the converter voltage calculation unit 26 obtains a difference from the DC voltage command Vd ^* and the DC voltage Vo, and the PI controller calculates the difference from the difference. The input current command value I ^* is derived. Next, the voltage drop of the reactor 5 due to the input current Is is obtained as ωLI ^* , and the voltage command phase difference φ and amplitude V ₂ are obtained respectively. Then, converter voltage command Vcr = V ₂ · sin (ωt + φ) is calculated using phase ωt detected by power supply phase detector 33.

  The aforementioned DC voltage Vo is the voltage across the first and second capacitors 6 and 7 detected by the first voltage detector 30, and Vd 2 is the second voltage detected by the second voltage detector 31. Vd1 is the voltage of the first capacitor 6 detected by the operation of the third voltage detector 32, which is a subtractor. Among these voltages, the charging pattern of the voltages Vd1 and Vd2 is determined by the switching states of the first and second switching elements 41 (SW1) and 42 (SW2) and the polarity of the input current Is as shown in FIG. . FIG. 8 shows the operation modes of FIG. 4 collectively. When both the first and second switching elements 41 (SW1) and 42 (SW2) are OFF, the full-wave rectification mode is set. When the switching element 41 (SW1) is ON and the second switching element 42 (SW2) is OFF, the first voltage doubler rectification mode is set, and the first switching element 41 (SW1) is OFF and the second switching element 41 (SW1) is OFF. When the switching element 42 (SW2) is ON, the second voltage doubler rectification mode is set, and when both the first and second switching elements 41 (SW1) and 42 (SW2) are ON, the power supply short-circuit mode is set. .

Next, a switching pattern selection method based on converter voltage command Vcr will be described with reference to FIG. In the notation of the first line in FIG. 9, the colon symbol (:) is intended to compare the left and right variables, and the second and subsequent lines indicate the comparison result and the corresponding arithmetic processing.
After calculating the converter voltage command Vcr, first, the capacitor voltages Vd1 and Vd2 are compared, and the capacitor having the lower voltage is selected for charging (50). Next, an operation mode is selected from the polarity of the input current Vs (51). Note that when the operation is performed under high power factor operation conditions, the polarity of the input current Vs may be considered to be substantially in phase with the phase of the voltage Vs. By estimating, a current sensor becomes unnecessary. In the second embodiment, the operation mode, that is, the PWM state of the first and second switching elements Sa and Sb is determined based on the voltage phase sign (Vs) (52). Further, the PWM duty for generating the voltage according to the voltage command in the determined operation mode is calculated (53). Then, the operation signal generation unit 27 generates the switching output signals of the first and second switching elements Sa and Sb based on the PWM duty and the operation mode, and the first and second switching circuits Sa and Sb through the interface circuits 34 and 35. Output to the second switching elements 41 and 42.

By sequentially performing the above operations, the converter voltage command Vcr based on the instantaneous voltage of each capacitor 6 and 7 is calculated even if the values of the capacitor voltages Vd1 and Vd2 are kept in balance and transiently unbalanced. Therefore, it is possible to realize extremely high quality power supply harmonic suppression.
In addition, since voltage fluctuations of the first and second capacitors 6 and 7 can be suppressed, a capacitor having a low withstand voltage can be selected, and the circuit can be configured at low cost. Moreover, since the voltage fluctuation of each capacitor | condenser 6 and 7 is small, the aged deterioration of the capacitor capacity depending on charging / discharging voltage can be suppressed, and the lifetime of a circuit can be extended.

Embodiment 3 FIG.
FIG. 10 is a circuit diagram of an AC / DC converter according to Embodiment 3 of the present invention. In addition, the same code | symbol is attached | subjected to the part which is the same as that of Embodiment 1 demonstrated in FIG. 1, or an equivalent, and description is abbreviate | omitted.
The difference in configuration from the first embodiment shown in FIG. 1 is that the first bidirectional switch 3 and the second bidirectional switch 4 are similar to the second rectifier 40 in the first and second embodiments. This is the point that the second switching elements 41 and 42 are replaced.
The AC / DC converter according to the third embodiment also uses the input voltage Vs (converter voltage Vc) of the first rectifier 2 as a substantially sinusoidal wave having three stages of voltage levels using the two capacitor voltages Vd1 and Vd2 on the DC side. It has the same function in terms of control.

  Accordingly, since the voltage detection circuit form is the same as that of the first embodiment, the withstand voltage protection and voltage balance control of the first and second capacitors 6 and 7 can be performed, and the reactor 5 can be downsized. it can. In addition, since voltage imbalance of the first and second capacitors 6 and 7 can be suppressed by feedback, voltage fluctuations of the first and second capacitors 6 and 7 can be suppressed, and a circuit due to deterioration of the capacitor capacity over time. Can prevent smoke and fire.

  Further, since the control unit 20 and the first and second voltage detectors 30 and 31 are connected to the same ground side, a voltage detection signal based on the detection voltage of the first and second voltage detectors 30 and 31. Therefore, the detection circuit can be configured simply and the present apparatus can be realized at low cost.

  In FIG. 10, when the first and second switching elements 41 and 42 are simultaneously turned on, or when any one of them is turned on, the current path flowing from the AC power supply 1 passes through two diodes. On the other hand, in the first embodiment, as shown in FIG. 1, the current path at the time of a short circuit goes through 3 to 4 diodes. Therefore, in the third embodiment, the number of diodes through which current flows is small, and therefore, there is an effect that the size, the cost, and the loss are reduced.

Embodiment 4 FIG.
FIG. 11 is a diagram showing the relationship between the switching states of the two switching elements and the capacitor voltage in the fourth embodiment of the present invention, and FIG. 12 is a diagram showing a method for generating a switching pattern in the second embodiment. In addition, the same number is attached | subjected about the part which shows the function operation | movement common to FIG. 8, FIG.
As shown in FIG. 11, the only factors that determine the capacitor voltage are the switching states (ON / OFF) of the first and second switching elements SW1 and SW2 (four types), and the input current Is is also taken into consideration. This is simpler than the second mode (see FIG. 8). Therefore, the generation method of the switching pattern is also shown in FIG. 12, and the determination based on the voltage or current polarity (51 in FIG. 9) is unnecessary.
In the fourth embodiment, in addition to the effects shown in the first embodiment, the determination based on the current Is or the voltage polarity of the AC power supply 1 is not required, so that the configuration of the control unit 20 can be further simplified.

Embodiment 5 FIG.
The capacitor voltage unbalanced state as shown in FIG. 5 described in the first embodiment may be generated not only by an event caused by operation but also by a circuit. The fifth embodiment is for eliminating the unbalanced state of the capacitor voltage caused by the circuit, and will be described below with reference to FIGS. FIG. 13 is a diagram showing the circuits of the first and second voltage detectors in the circuit diagram of the first embodiment, and FIG. 14 is a diagram showing a circuit around the capacitor for explaining the fifth embodiment of the present invention. is there.

  In the case of FIG. 13, the discharge circuit Rs <b> 2 is formed by the second capacitor 7 and the voltage detection resistor constituting the second voltage detector 7. On the other hand, since there is no independent discharge path for the first capacitor 6, the voltage is unbalanced if left untreated. In particular, when the power consumption of the DC load 8 is zero or very small, the power consumption ratio indicated by the discharge circuit Rs2 becomes large, and the voltage imbalance becomes more prominent. Thereby, there is a possibility that problems such as the stability of the operation of the control unit 20 being impaired or the protection being applied.

  Therefore, as shown in FIG. 14, a circuit Rs2 having an impedance equivalent to that of the discharge circuit Rs2 formed independently on the second capacitor 7 side is provided on the first capacitor 6 side. Thereby, the time constant of discharge of each capacitor | condenser 6 and 7 becomes the same, and the problem by the imbalance of a capacitor voltage is eliminated.

  As an application example of the present invention, the present invention can be used for a power supply device for a load that consumes power by direct current. In particular, it can be used as a power supply device for an inverter that is a DC / AC converter, and can be applied to an inverter that drives a permanent magnet motor, realizing energy saving, a low-cost, low-noise AC / DC converter configuration, etc. In addition to refrigerators and washing dryers, it can be applied to household appliances such as refrigerators, dehumidifiers, heat pump water heaters, showcases, vacuum cleaners, and can also be applied to fan motors, ventilation fans, hand dryers, etc. .

It is a circuit diagram of the AC / DC converter showing Embodiment 1 of the present invention. FIG. 3 is a circuit diagram in an ideal state for explaining the first embodiment; FIG. 4 is a waveform diagram showing a principle operation for explaining the first embodiment. 3 is a circuit diagram showing an operation mode in the first embodiment. FIG. 6 is a diagram for explaining an operation at the time of voltage imbalance in the first embodiment. FIG. It is a circuit diagram of the alternating current direct current converter which shows Embodiment 2 of this invention. 6 is a block diagram showing a configuration of a converter voltage calculation unit in a second embodiment. FIG. It is a figure which shows the relationship between the switching state of the 1st and 2nd switching element in Embodiment 2, and a capacitor | condenser voltage. 10 is a diagram illustrating a switching pattern generation method according to Embodiment 2. FIG. It is a circuit diagram of the alternating current direct current converter which shows Embodiment 3 of this invention. It is a figure which shows the relationship between the switching state of two switching elements and capacitor voltage in Embodiment 4 of this invention. 10 is a diagram illustrating a switching pattern generation method according to Embodiment 2. FIG. FIG. 3 is a diagram illustrating circuits of first and second voltage detectors in the circuit diagram of the first embodiment. It is a figure which shows the circuit around a capacitor | condenser for demonstrating Embodiment 5 of this invention. It is a circuit diagram which shows the other example of a bidirectional switch.

Explanation of symbols

1 AC power source, 2 rectifier (first rectifier), 3 (Sa) first bidirectional switch,
4 (Sb) second bidirectional switch, 5 reactor, 6 first capacitor, 7 second capacitor, 8 DC load, 20 control unit, 26 converter voltage calculation unit, 27 operation signal generation unit, 30 first Voltage detector, 31 second voltage detector, 32 third voltage detector of subtractor, 33 power supply phase detector, 40 second rectifier, 41 (SW1) first switching element, 42 (SW2) first 2 switching elements.

Claims (17)

A rectifier connected to an AC power source via a reactor;
A plurality of capacitors connected in series between the output terminals of the rectifier;
A first bidirectional switch inserted between one input terminal of the rectifier and a connection point of the plurality of capacitors;
A second bidirectional switch inserted between the other input terminal of the rectifier and a connection point of the plurality of capacitors;
First voltage detection means for detecting voltages across the plurality of capacitors;
Second voltage detecting means for detecting a voltage of a capacitor located on a low potential side among the plurality of capacitors;
Third voltage detection means for detecting the voltage of the capacitor located on the high potential side among the plurality of capacitors;
Control means for operating both the first and second bidirectional switches during a half cycle of the AC power source to control to a desired output voltage value;
The ground side of the control means is connected to the negative side of the rectifier in a non-insulated manner, and the third voltage detection means is a difference between a detection voltage of the first voltage detection means and a detection voltage of the second voltage detection means. An AC / DC converter characterized by detecting the voltage of a capacitor located on the high potential side from the capacitor. First and second rectifiers connected in parallel to an AC power source via a reactor;
A plurality of capacitors connected in series between output terminals of the first rectifier;
A first switching element inserted between a positive electrode side of the second rectifier and connection points of the plurality of capacitors;
A second switching element inserted between a negative electrode side of the second rectifier and connection points of the plurality of capacitors;
A first voltage detector for detecting a voltage across the plurality of capacitors;
Second voltage detecting means for detecting a voltage of a capacitor located on a low potential side among the plurality of capacitors;
Third voltage detection means for detecting the voltage of the capacitor located on the high potential side among the plurality of capacitors;
Control means for controlling both the first and second switching elements to a desired output voltage value during a half cycle of the AC power source,
The ground side of the control unit is connected to the negative side of the first rectifier in a non-insulated manner, and the third voltage detection unit is configured to detect the detection voltage of the first voltage detection unit and the detection of the second voltage detection unit. An AC / DC converter characterized by detecting a voltage of a capacitor located on a high potential side from a voltage difference.   The AC / DC converter according to claim 1, wherein the control unit includes the third voltage detection unit.   The control means calculates a generation time ratio per unit time of a switching pattern divided by charging paths to the plurality of capacitors, and controls a switching output signal for each unit time based on the ratio. The AC / DC converter according to any one of claims 1 to 3.   The said control means controls the said 1st and 2nd bidirectional | two-way switch so that the difference of each detection voltage of the said 2nd and 3rd voltage detection means may become small. 5. The AC / DC converter according to any one of 4 above.   5. The control means controls the first and second switching elements so that a difference between detection voltages of the second and third voltage detection means becomes small. The AC / DC converter according to any one of the above. The control means includes
A full-wave rectification mode in which both the first and second bidirectional switches are OFF;
A first voltage doubler rectification mode in which the first bidirectional switch is turned on and the second bidirectional switch is turned off;
A second voltage rectification mode in which the first bidirectional switch is turned off and the second bidirectional switch is turned on;
A power supply short-circuit mode in which both the first and second bidirectional switches are turned on,
The first and second voltage doubler rectification modes are discriminated based on a magnitude relationship between charging voltages of the plurality of capacitors and a power supply current polarity or an estimated power supply current polarity. Item 6. The AC / DC converter according to any one of Items 3 to 5. The control means includes
A full-wave rectification mode in which both the first and second switching elements are OFF;
A first voltage doubler rectification mode in which the first switching element is turned on and the second switching element is turned off;
A second voltage rectification mode in which the first switching element is turned off and the second switching element is turned on;
A power supply short-circuit mode in which both the first and second switching elements are ON,
7. The alternating current according to claim 2, wherein the first and second voltage doubler rectification modes are controlled so that a difference between charging voltages of the plurality of capacitors is reduced. DC converter.   9. The AC / DC converter according to claim 8, wherein the control means estimates a power supply current polarity based on phase information of a power supply voltage.   The number of occurrences of the full-wave rectification mode, the first voltage doubler rectification mode, the second voltage doubler rectification mode, and the power supply short-circuit mode controlled by the control means is set to be twice within a unit time for controlling the switching mode The AC / DC converter according to claim 1, wherein the converter is an AC / DC converter.   The first voltage detection means digitally converts a plurality of resistors connected in series between both ends of the plurality of capacitors and a voltage on the low potential side of the negative electrode of the rectifier circuit divided by the plurality of resistors. The second voltage detecting means includes a plurality of resistors connected in series between both ends of the capacitor located on the low potential side of the plurality of capacitors, and the plurality of resistors. 11. The AC / DC converter according to claim 1, comprising: an A / D converter that converts a voltage on a low potential side of the negative electrode of the rectifier circuit divided by a resistor into a digital value. Conversion device.   12. The AC / DC converter according to claim 1, wherein a nonmagnetic material for suppressing reactor noise is inserted into a gap portion of the magnetic flux.   The said 1st and 2nd bidirectional switch is comprised by the diode rectifier and the switching element, The any one of Claim 1, Claim 3 thru | or 5, Claim 7 and Claim 9 thru | or 12 characterized by the above-mentioned. AC-DC converter described in 1.   The first and second bidirectional switches are connected in parallel to a first switching element and a first diode connected in series to pass a current in one direction, and to the first switching element and the first diode; 14. The system according to claim 1, wherein the second switching element and the second diode are connected in series so that a current flows in the reverse direction. AC to DC converter.   The impedance between both ends of a capacitor located on the high potential side of the plurality of capacitors and the impedance between both ends of the capacitor located on the low potential side are substantially matched to each other. The AC / DC converter according to any one of the above. An AC / DC converter according to any one of claims 1 to 15,
A compressor driving device comprising: an inverter that converts DC power from the AC / DC converter into AC power to drive a permanent magnet motor of the compressor.   An air conditioner in which refrigerant is circulated by the compressor driving device according to claim 16.

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