JP5713291B2 - AC / DC converter - Google Patents

Description

  The present invention relates to an AC / DC converter that converts an AC input voltage into a DC output voltage having a desired target voltage value.

  As a conventional AC / DC converter, for example, Patent Document 1 discloses an AC / DC converter 10 shown in FIG. As shown in the figure, the AC / DC converter 10 converts an AC input voltage Vac into a DC output voltage Vdc having a desired target voltage value, and includes a diode bridge circuit 11, a high frequency filter circuit 12, and the like. A power factor correction circuit 13 composed of a step-up chopper circuit and a DC-DC conversion circuit 14 composed of a step-down chopper circuit are provided.

  Since the AC / DC converter 10 includes both the step-up chopper circuit and the step-down chopper circuit, the target voltage value can be set to a voltage value lower than the voltage value of the AC input voltage Vac, or a high voltage value can be set. Can also be set.

  As another conventional AC / DC converter, Non-Patent Document 1, for example, discloses an AC / DC converter 20 shown in FIG. As shown in the figure, the AC / DC converter 20 converts the AC input voltage Vac into a DC output voltage Vdc having a desired target voltage value (but not less than the voltage value of the AC input voltage Vac). The noise filter circuit 21, the inrush prevention circuit 22, the diode bridge circuit 23, the chopper circuit including the switching element SW and the like, and the switching element SW is controlled based on the voltage value of the DC output voltage Vdc and the current value of each part. And a control unit 24.

JP 2001-86737 A

Hiroshi Yamazaki, “Characteristics of Active Filter and Current Status of Development / Application”, Electronic Technology, Nikkan Kogyo Shimbun, March 1990, Vol. 32, No. 3, p. 76 (FIG. 9)

  However, in the AC / DC converters 10 and 20, since an input current always flows through the diode bridge circuits 11 and 23, when the output power increases and the input current increases, the diode bridge circuits 11 and 23 generate correspondingly. There was a problem that the loss to be increased and the efficiency deteriorated. In the AC / DC converter 20, since an input current always flows through the inrush prevention circuit 22, a loss has occurred in the circuit as well.

  Further, the efficiency of the AC / DC converter 10 that can set the target voltage value in a wide range is the efficiency of the power factor correction circuit (step-up chopper circuit) 13 and the DC-DC conversion circuit (step-down chopper circuit) 14 connected in series. Since it is a product, it is generally low and there is limited room for improvement. As described above, the AC / DC converter 20 cannot set the target voltage value lower than the AC input voltage Vac.

  The present invention has been made in view of the above circumstances, and the problem is that an AC / DC which is more efficient than the conventional one and can set a target voltage value of a DC output voltage in a wide range. The object is to provide a DC converter.

In order to solve the above problems, an AC / DC converter according to the present invention provides:
An output terminal pair consisting of a first output terminal and a second output terminal by converting an AC input voltage inputted to an input terminal pair consisting of a first input terminal and a second input terminal into a DC output voltage having a desired target voltage value In the AC / DC conversion device for outputting from the AC, the chopper unit having the coil, the capacitor and the first to fifth switching elements, the input voltage detection unit for detecting the voltage value of the AC input voltage, and the voltage value of the DC output voltage are detected. And the first to fifth switching elements of the chopper unit so that the voltage value of the DC output voltage becomes the target voltage value based on the voltage value detected by the input voltage detection unit and the output voltage detection unit. And a control circuit for controlling on / off of the first and second switching elements. A series circuit including first and second switching elements is connected between the first input terminal and the second input terminal. A series circuit composed of third and fourth switching elements is connected between the first input terminal and the second input terminal on the output side with respect to the series circuit composed of the ching elements, and is connected to the first and second switching elements. The part and the connection part of the third and fourth switching elements are connected by a coil, the fifth switching element is connected between the connection part of the third and fourth switching elements and the first output terminal, and the capacitor Connected between the first output terminal and the second output terminal on the output side of the fifth switching element, the control unit controls on / off of the first to fifth switching elements and moves up and down to the chopper unit. The AC input voltage is converted into a DC output voltage having a target voltage value by selectively executing either the pressure chopper operation or the reverse buck-boost chopper operation.

  According to this configuration, the AC input voltage is obtained when the chopper controlled based on the polarity of the AC input voltage and the polarity of the target voltage value selectively executes either the step-up / step-down chopper operation or the reverse step-up / step-down chopper operation. Are directly switched, a diode bridge circuit can be dispensed with, and loss due to the circuit can be prevented. Further, according to this configuration, since it is not necessary to connect two or more chopper circuits in series, it is possible to prevent the efficiency from deteriorating.

  Here, when the target voltage value is set to be positive, the control unit causes the buck-boost chopper operation to be performed when the AC input voltage is a positive voltage value, and when the AC input voltage is a negative voltage value. If the target voltage value is set to a negative value while the inverting buck-boost chopper operation is performed, the inverting buck-boost chopper operation is performed when the AC input voltage is a positive voltage value, and the AC input voltage is a negative voltage. The step-up / step-down chopper operation is performed when the value is a value.

  More specifically, in the step-up / step-down chopper operation, the third switching element is turned off, and the first and fourth switching elements and the second and fifth switching elements are alternately turned on / off and inverted. In the step-up / step-down chopper operation, the second switching element is turned on, the first and fourth switching elements are turned off, and the third switching element and the fifth switching element are alternately turned on / off.

  The control unit of the AC / DC converter is configured until a predetermined time elapses after input of an AC input voltage is started and / or until a voltage value of the DC output voltage reaches a predetermined voltage value. In the step-up / step-down chopper operation, it is preferable to set the duty low by shortening the ON time of the first and fourth switching elements.

  According to this configuration, since the soft start function can be realized only by changing the duty in the step-up / step-down chopper operation, the inrush prevention circuit can be eliminated, and the occurrence of loss due to the circuit can be prevented.

  Further, the control unit of the AC / DC conversion device may start the input of the AC input voltage until the predetermined time elapses and / or until the voltage value of the DC output voltage reaches the predetermined voltage value. Meanwhile, in the inverting step-up / down chopper operation, the duty may be set low by shortening the ON time of the third switching element.

  Also with this configuration, the soft start function can be realized only by changing the duty in the inverting step-up / step-down chopper operation, so that the inrush prevention circuit can be made unnecessary and the occurrence of loss due to the circuit can be prevented.

  ADVANTAGE OF THE INVENTION According to this invention, the AC / DC converter which can set the target voltage value of DC output voltage in a wide range can be provided which is more efficient than the conventional one.

1 is a schematic configuration diagram of an AC / DC converter according to the present invention. It is a figure which shows the correspondence of two chopper operation | movement performed when the voltage value of alternating current input voltage and a target voltage value are positive. It is a figure which shows the correspondence of two chopper operation | movement performed when the voltage value of alternating current input voltage and a target voltage value are negative. It is an equivalent circuit diagram of the AC / DC converter according to the present invention, where (A) is an equivalent circuit diagram during a first buck-boost chopper operation, and (B) is an equivalent circuit diagram during a first inversion buck-boost chopper operation. 4A and 4B are equivalent circuit diagrams of the AC / DC converter according to the present invention, where FIG. 5A is an equivalent circuit diagram during a second inversion buck-boost chopper operation, and FIG. It is a schematic block diagram of the conventional AC / DC converter. It is a schematic block diagram of the conventional AC / DC converter.

  Hereinafter, preferred embodiments of an AC / DC converter according to the present invention will be described with reference to the accompanying drawings.

  FIG. 1 is a schematic configuration diagram of an AC / DC converter 1 according to the present invention. As shown in the figure, the AC / DC converter 1 converts an AC input voltage Vac input from a pair of first input terminal 6a and second input terminal 6b into a DC output voltage Vdc having a desired target voltage value. The DC output voltage Vdc is converted and output to the load RL from the first output terminal 7a and the second output terminal 7b that make a pair, and the chopper unit 2 having a plurality of switching elements SW1 to SW5, and the AC input Based on the input voltage detector 3 that detects the voltage value of the voltage Vac, the output voltage detector 4 that detects the voltage value of the DC output voltage Vdc, and the voltage values detected by the input voltage detector 3 and the output voltage detector 4. The control unit 5 is provided for controlling the chopper unit 2 so that the voltage value of the DC output voltage Vdc becomes the target voltage value.

  The chopper unit 2 includes a first switching element SW1 and a third switching element SW3 each having one end connected to the first input terminal 6a, and a second switching element SW2 having one end connected to the other end of the first switching element SW1. And the coil L, the third switching element SW3 and the fourth switching element SW4 and one end connected to the other end of the coil L, respectively, and the other end of the fifth switching element SW5 and one end connected to the other end of the fifth switching element SW5. And a capacitor Co. The other ends of the second switching element SW2, the fourth switching element SW4, and the capacitor Co are connected to the second input end 6b and the second output end 7b, respectively, and the other end of the fifth switching element SW5 is the first output end 7a. It is connected to the. Each switching element SW <b> 1 to SW <b> 5 is ON / OFF controlled by the control unit 5.

  The chopper unit 2 also includes a capacitor Ci connected to the first input terminal 6a and the second input terminal 6b, but the capacitor Ci has a very small capacity compared to the capacitor Co, and the operation of the chopper unit 2 Is ignored in the following, in order to simplify the explanation, the capacitor Ci is ignored.

  As shown in FIG. 2 and FIG. 3, in the present invention, the control unit 5 performs each control according to the voltage value of the AC input voltage Vac and the target voltage value Vt (the voltage value of the DC output voltage Vdc to be output to the load RL). The control of the switching elements SW1 to SW5 is changed. In other words, in the present invention, the chopper operation of the chopper unit 2 is changed according to the voltage value of the AC input voltage Vac and the target voltage value Vt.

  Specifically, the chopper unit 2 of the AC / DC converter 1 according to the present invention (1) voltage value of the AC input voltage Vac (the potential of the first input terminal 6a when the second input terminal 6b is used as a reference). ) Is positive and the target voltage value Vt (target potential of the first output terminal 7a when the second output terminal 7b is used as a reference) is positive, the first step-up / step-down chopper operation is performed, and (2) AC When the voltage value of the input voltage Vac is negative and the target voltage value Vt is positive, the first inversion buck-boost chopper operation is performed. (3) The voltage value of the AC input voltage Vac is positive and the target voltage value When Vt is negative, the second inversion buck-boost chopper operation is performed. (4) When the voltage value of the AC input voltage Vac is negative and the target voltage value Vt is negative, the second buck-boost chopper operation is performed. With these operations, the voltage value of the DC output voltage Vdc is maintained (stabilized) at the target voltage value Vt. 2 and 3 show a state where the voltage value of the DC output voltage Vdc becomes the target voltage value Vt by the above control.

  Of the four chopper operations of the chopper unit 2, the first step-up / step-down chopper operation will be described first. In this operation, the third switching element SW3 is always turned off. Therefore, the AC / DC converter 1 during this operation is expressed by a simple equivalent circuit shown in FIG.

  In this operation, the first switching element SW1 and the fourth switching element SW4, the second switching element SW2 and the fifth switching element SW5 are alternately turned on and off. That is, when the first switching element SW1 and the fourth switching element SW4 are switched from the ON state to the OFF state, the second switching element SW2 and the fifth switching element SW5 are synchronously switched from the OFF state to the ON state. When the first switching element SW1 and the fourth switching element SW4 are turned on, energy is stored in the coil L. Further, when the second switching element SW2 and the fifth switching element SW5 are turned on, the energy stored in the coil L is released.

When the ON time of the first switching element SW1 and the fourth switching element SW4 in one switching cycle T is Ton, the duty α (= Ton / T) of the first switching element SW1 and the fourth switching element SW4 is obtained by the following equation. Can do.

Duty α = Vdc voltage value / (Vdc voltage value + Vac voltage value)

  According to the first step-up / step-down chopper operation, the direct-current output voltage Vdc whose voltage value is the target voltage value Vt can be obtained by stepping up / down the alternating-current input voltage Vac, and the direct-current output voltage Vdc can be supplied to the load RL ( However, the voltage value of the AC input voltage Vac> 0, the target voltage value Vt> 0, and the DC output voltage Vdc> 0).

  In the first inversion step-up / step-down chopper operation, the second switching element SW2 is always turned on, and the first switching element SW1 and the fourth switching element SW4 are always turned off. Therefore, the AC / DC conversion device 1 during this operation is expressed by a simple equivalent circuit shown in FIG.

  In this operation, the third switching element SW3 and the fifth switching element SW5 are alternately turned ON / OFF. That is, when the third switching element SW3 is switched from the ON state to the OFF state, the fifth switching element SW5 is synchronously switched from the OFF state to the ON state. When the third switching element SW3 is turned on, energy is stored in the coil L. Further, when the fifth switching element SW5 is turned on, the energy stored in the coil L is released.

When the ON time of the third switching element SW3 in one switching cycle T is Ton, the duty α (= Ton / T) of the third switching element SW3 can be obtained by the following equation.

Duty α = Vdc voltage value / (Vdc voltage value−Vac voltage value)

  According to the first inversion step-up / down chopper operation, the DC input voltage Vac having the target voltage value Vt is obtained by inverting and stepping up / down the AC input voltage Vac, and the DC output voltage Vdc is supplied to the load RL. (However, the voltage value <0 of the AC input voltage Vac, the target voltage value Vt> 0, and the DC output voltage Vdc> 0).

  In the second inversion step-up / step-down chopper operation, the second switching element SW2 is always turned on, and the first switching element SW1 and the fourth switching element SW4 are always turned off. Therefore, the AC / DC conversion device 1 during this operation is expressed by a simple equivalent circuit shown in FIG. The equivalent circuit shown in FIG. 4 is common to the equivalent circuit shown in FIG. 4B except that the polarity of the DC output voltage Vdc (target voltage value Vt) is inverted between positive and negative.

  In this operation, the third switching element SW3 and the fifth switching element SW5 are alternately turned ON / OFF. That is, when the third switching element SW3 is switched from the ON state to the OFF state, the fifth switching element SW5 is synchronously switched from the OFF state to the ON state. When the third switching element SW3 is turned on, energy is stored in the coil L. Further, when the fifth switching element SW5 is turned on, the energy stored in the coil L is released.

When the ON time of the third switching element SW3 in one switching cycle T is Ton, the duty α (= Ton / T) of the third switching element SW3 can be obtained by the following equation.

Duty α = Vdc voltage value / (Vdc voltage value−Vac voltage value)

  According to the second inversion step-up / step-down chopper operation, the DC input voltage Vac having the target voltage value Vt is obtained by inverting and stepping up / down the AC input voltage Vac, and the DC output voltage Vdc is supplied to the load RL. (However, the voltage value of the AC input voltage Vac> 0, the target voltage value Vt <0, and the DC output voltage Vdc <0).

  In the second step-up / step-down chopper operation, the third switching element SW3 is always turned off. Therefore, the AC / DC converter 1 during this operation is expressed by a simple equivalent circuit shown in FIG. The equivalent circuit shown in the figure is common to the equivalent circuit shown in FIG. 4A except that the polarity of the DC output voltage Vdc (target voltage value Vt) is inverted between positive and negative.

  In this operation, the first switching element SW1 and the fourth switching element SW4, the second switching element SW2 and the fifth switching element SW5 are alternately turned on and off. That is, when the first switching element SW1 and the fourth switching element SW4 are switched from the ON state to the OFF state, the second switching element SW2 and the fifth switching element SW5 are synchronously switched from the OFF state to the ON state. When the first switching element SW1 and the fourth switching element SW4 are turned on, energy is stored in the coil L. Further, when the second switching element SW2 and the fifth switching element SW5 are turned on, the energy stored in the coil L is released.

When the ON time of the first switching element SW1 and the fourth switching element SW4 in one switching cycle T is Ton, the duty α (= Ton / T) of the first switching element SW1 and the fourth switching element SW4 is obtained by the following equation. Can do.

Duty α = Vdc voltage value / (Vdc voltage value + Vac voltage value)

  According to the second step-up / step-down chopper operation, the direct-current output voltage Vdc whose voltage value is the target voltage value Vt can be obtained by stepping up / down the alternating-current input voltage Vac, and the direct-current output voltage Vdc can be supplied to the load RL ( However, the voltage value <0 of the AC input voltage Vac, the target voltage value Vt <0, and the DC output voltage Vdc <0).

  As described above, in the AC / DC converter 1 according to the present invention, the control unit 5 performs the chopper operation of the chopper unit 2 as (1) first step-up / step-down chopper operation, (2) first inversion step-up / step-down chopper operation, ( 3) Switch to the second reverse buck-boost chopper operation and (4) the second buck-boost chopper operation. In each chopper operation, the chopper unit 2 switches the AC input voltage Vac directly. Therefore, according to the AC / DC conversion apparatus 1 according to the present invention, the diode bridge circuit (reference numeral 11 in FIG. 6 and reference numeral 23 in FIG. 7) can be eliminated, so that the generation of loss due to the circuit can be prevented. Can improve efficiency.

  Further, as is apparent from FIGS. 1, 4 and 5, the AC / DC converter 1 according to the present invention does not have a configuration in which two or more chopper circuits are connected in series. Therefore, according to the AC / DC conversion apparatus 1 according to the present invention, it is possible to prevent the deterioration of the efficiency of the entire apparatus due to the deterioration of the efficiency of each of the two or more chopper circuits.

  The AC / DC converter according to the present invention is not limited to the above-described configuration, and various modifications can be considered.

  For example, in order to further improve the efficiency, the voltage value of the DC output voltage Vdc is set to a predetermined voltage value (for example, a target value) until a predetermined time elapses after the input of the AC input voltage Vac is started. It is preferable to set the duty in each chopper operation to a duty different from the normal time until the voltage value reaches about 95% of the voltage value Vt). According to this, since the amount of inrush current can be limited without the inrush prevention circuit (reference numeral 22 in FIG. 7), it is possible to prevent the occurrence of loss due to the circuit.

  More specifically, in the first buck-boost chopper operation and the second buck-boost chopper operation, when the second switching element SW2 and the fifth switching element SW5 are switched to the ON state, the energy accumulated in the coil L is The voltage is supplied to the capacitor Co through the fifth switching element SW5. Therefore, the duty time (= Ton / T) is set lower than normal so that the ON time Ton of the first switching element SW1 and the fourth switching element SW4 is shortened, and the energy accumulated in the coil L is reduced. The amount of inrush current can be limited.

  In the first inversion buck-boost chopper operation and the second inversion buck-boost chopper operation, when the fifth switching element SW5 is switched to the ON state, the energy accumulated in the coil L passes through the fifth switching element SW5. It is supplied to the capacitor Co. Accordingly, the amount of inrush current can be reduced by setting the duty [alpha] (= Ton / T) lower than usual to shorten the ON time Ton of the third switching element SW3 and reducing the energy accumulated in the coil L. Can be limited.

  As another modified example, by providing an input current detection circuit, the control unit 5 allows each of the switching elements SW1 to SW5 to bring the input current waveform closer to a sine wave for power factor improvement and harmonic countermeasures. Control may be additionally performed.

DESCRIPTION OF SYMBOLS 1 AC / DC converter 2 Chopper part 3 Input voltage detection part 4 Output voltage detection part 5 Control part

Claims (5)

An output terminal pair consisting of a first output terminal and a second output terminal by converting an AC input voltage inputted to an input terminal pair consisting of a first input terminal and a second input terminal into a DC output voltage having a desired target voltage value In the AC / DC converter for outputting from
A chopper portion having a coil, a capacitor, and first to fifth switching elements;
An input voltage detector for detecting a voltage value of the AC input voltage;
An output voltage detector for detecting a voltage value of the DC output voltage;
Based on the voltage values detected by the input voltage detector and the output voltage detector, the first to fifth switching elements of the chopper unit are set so that the voltage value of the DC output voltage becomes the target voltage value. A control unit for on / off control,
A series circuit composed of the first and second switching elements is connected between the first input terminal and the second input terminal,
A series circuit composed of the third and fourth switching elements is connected between the first input terminal and the second input terminal on the output side with respect to the series circuit composed of the first and second switching elements;
The connection part of the first and second switching elements and the connection part of the third and fourth switching elements are connected by the coil,
The fifth switching element is connected between the connection portion of the third and fourth switching elements and the first output end,
The capacitor is on the output side of the fifth switching element and is connected between the first output end and the second output end;
The control unit performs on / off control of the first to fifth switching elements, and causes the chopper unit to selectively execute either a step-up / step-down chopper operation or a reverse step-up / step-down chopper operation, whereby the AC input is performed. An AC / DC converter characterized by converting a voltage into a DC output voltage having the target voltage value. The controller is
When the target voltage value is set to be positive, a step-up / step-down chopper operation is performed when the AC input voltage is a positive voltage value, and an inverting step-up / step-down chopper is performed when the AC input voltage is a negative voltage value. While doing the action,
When the target voltage value is set to be negative, an inversion buck-boost chopper operation is performed when the AC input voltage is a positive voltage value, and a buck-boost chopper when the AC input voltage is a negative voltage value. 2. The AC / DC conversion apparatus according to claim 1, wherein the operation is performed. In the step-up / step-down chopper operation, the third switching element is turned off, and the first and fourth switching elements and the second and fifth switching elements are alternately turned on / off,
In the inverting buck-boost chopper operation, the second switching element is turned on, the first and fourth switching elements are turned off, and the third switching element and the fifth switching element are alternately turned on / off. The AC / DC conversion apparatus according to claim 2, wherein the AC / DC conversion apparatus is off-controlled.   Until the predetermined time elapses after the input of the AC input voltage is started and / or until the voltage value of the DC output voltage reaches a predetermined voltage value, the controller 4. The AC / DC converter according to claim 1, wherein in the chopper operation, the duty is set to be low by shortening the ON time of the first and fourth switching elements. 5.   Until the predetermined time elapses after the input of the AC input voltage is started and / or until the voltage value of the DC output voltage reaches a predetermined voltage value, the control unit 4. The AC / DC converter according to claim 1, wherein, in the pressure chopper operation, the duty is set to be low by shortening the ON time of the third switching element. 5.

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