JP5713261B2 - 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, Non-Patent Document 1, for example, discloses an AC / DC converter 10 shown in FIG. As shown in the figure, an 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 noise filter 11, an inrush prevention circuit 12, A diode bridge circuit 13, a chopper circuit including a switching element SW and the like, and a control unit 14 that controls the switching element SW based on the voltage value of the DC output voltage Vdc and the current value of each part are provided.

  As another conventional AC / DC converter, Non-Patent Document 2, for example, discloses an AC / DC converter 20 shown in FIG. As shown in the figure, the AC / DC converter 20 includes a power thermistor TH that functions as an inrush prevention circuit and a diode bridge circuit 21 at the subsequent stage of the filter circuit for removing noise. The AC / DC converter 20 is common to the AC / DC converter 10 shown in FIG. 7 in that the DC voltage rectified by the diode bridge circuit 21 is input to the chopper circuit 22.

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) Masatoshi Sugimoto, Hironobu Shiroyama, “Design of Power Factor Correction Circuit Using Boost Converter”, Power Circuit Design 2009, CQ Publisher, May 2009, p. 184 (Fig. 33)

  However, since the input current always flows through the inrush prevention circuits 12 and TH and the diode bridge circuits 13 and 21 in the AC / DC converters 10 and 20, when the output power increases and the input current increases, the above-described AC / DC converters 10 and 20 respond accordingly. There is a problem that the loss generated in the circuit increases and the efficiency deteriorates. Further, the AC / DC converters 10 and 20 have a problem that the voltage value of the DC output voltage Vdc cannot be made lower than the voltage value of the AC input voltage Vac.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide an AC / DC converter that is more efficient than the conventional one and can output an arbitrary positive output voltage. It is in.

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. A first switching element, a coil, and a second switch in order from the input side to the output side between the first input end and the first output end. Are connected in series, one end of the third switching element is connected to the connection portion of the first switching element and the coil, the other end of the third switching element is connected to the second input end and the second output end, One end of the fourth switching element is connected to a connection portion between the coil and the second switching element, the other end of the fourth switching element is connected to the second input end and the second output end, and a capacitor is an output of the second switching element. Is connected between the first output end and the second output end, one end of the fifth switching element is connected to the connection portion of the first switching element and the coil, and the other end of the fifth switching element is The control unit is connected to the first output terminal, and the control unit controls on / off of the first to fifth switching elements, and the chopper unit performs step-up chopper operation, step-down chopper operation, and step-up / step-down chopper operation. Any pre-inverting buck-boost chopper operation by executing selectively, is characterized by converting an AC input voltage into a DC output voltage having a desired voltage value.

  According to this configuration, the chopper unit controlled based on the voltage value of the AC input voltage selectively executes any one of the step-up chopper operation, the step-down chopper operation, the step-up / step-down chopper operation, and the reverse step-up / step-down chopper operation. Since the AC input voltage is directly switched by each chopper operation, a diode bridge circuit can be dispensed with, and loss due to the circuit can be prevented. Further, according to this configuration, it is possible to output not only a DC output voltage having a voltage value higher than the AC input voltage but also a DC output voltage having a voltage value lower than the AC input voltage.

  As a first aspect of the AC / DC converter according to the invention, the control unit causes the chopper unit to perform a boost chopper operation when the voltage value of the AC input voltage is positive and lower than the target voltage value. When the voltage value of the AC input voltage is positive and higher than the target voltage value, the chopper unit performs a step-down chopper operation. When the voltage value of the AC input voltage is negative, the chopper unit performs an inverted buck-boost chopper. It is characterized by having an operation performed.

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

  In the control of the AC / DC converter according to the first aspect, the voltage value of the DC output voltage reaches the predetermined voltage value until a predetermined time elapses after the input of the AC input voltage is started. In the meantime, it is preferable that the control unit sets the duty to be low by shortening the ON time of the second switching element in the step-up chopper operation and / or increasing the OFF time of the first switching element.

  According to this configuration, since the soft start function can be realized only by changing the duty of any one of the switching elements, the inrush prevention circuit can be eliminated, and the occurrence of loss due to the circuit can be prevented. .

  In order to solve the above problem, as a second aspect of the AC / DC converter according to the present invention, the control unit performs a step-up / step-down chopper operation on the chopper unit when the voltage value of the AC input voltage is positive. In addition, when the voltage value of the AC input voltage is negative, the chopper unit is caused to perform an inverted buck-boost chopper operation.

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

  The control of the AC / DC converter according to the second aspect is performed until the predetermined time elapses after the input of the AC input voltage is started and / or the voltage value of the DC output voltage reaches the predetermined voltage value. In the meantime, it is preferable that the control unit sets the duty low by shortening the on-time of the first and fourth switching elements in the step-up / step-down chopper operation.

  According to this configuration, since the soft start function can be realized only by changing the duty of the first and fourth switching elements in the step-up / step-down chopper operation, the inrush prevention circuit can be dispensed with and the loss caused by the circuit Can be prevented.

  According to the present invention, since the diode bridge circuit and the inrush prevention circuit can be omitted, the occurrence of loss in the circuit can be prevented, the AC is more efficient than the conventional one, and can output any positive output voltage. A DC / DC converter can be provided.

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 the voltage value of alternating current input voltage, and three chopper operation | movement in 1st Embodiment. FIG. 3 is an equivalent circuit diagram of the AC / DC converter according to the first embodiment, where (A) is a step-up chopper operation, (B) is a step-down chopper operation, and (C) is an equivalent circuit during an inverting buck-boost chopper operation. FIG. It is a figure which shows the correspondence of the voltage value of alternating current input voltage, and two chopper operation | movement in 2nd Embodiment. It is an equivalent circuit diagram of the AC / DC converter according to the second embodiment, where (A) is an equivalent circuit diagram during a buck-boost chopper operation, and (B) is an equivalent circuit diagram during an inverting buck-boost chopper operation. It is a block diagram at the time of replacing the 2nd and 4th switching element of FIG. 1 with the actual semiconductor element. 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.

[First Embodiment]
FIG. 1 is a schematic configuration diagram of an AC / DC converter 1A according to the first embodiment of the present invention. As shown in the figure, the AC / DC converter 1A converts the AC input voltage Vac input from the paired 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 5A 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 having one end connected to the first input end 6a, a third switching element SW3 having one end connected to the other end of the first switching element SW1, a fifth switching element SW5, and The coil L includes a second switching element SW2 and a fourth switching element SW4 each having one end connected to the other end of the coil L, and a capacitor Co having one end connected to the other end of the second switching element SW2. The other ends of the third switching element SW3, the fourth switching element SW4 and the capacitor Co are connected to the second input terminal 6b and the second output terminal 7b, respectively, and the other ends of the second switching element SW2 and the fifth switching element SW5. Are respectively connected to the first output terminal 7a. Each switching element SW1-5 is ON / OFF controlled by the control unit 5A.

  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, in this invention, 5 A of control parts change control of each switching element SW1-SW5 according to the voltage value of AC input voltage Vac. 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.

  Specifically, the chopper unit 2 of the AC / DC converter 1 </ b> A according to the present embodiment includes (1) the voltage value of the AC input voltage Vac (the first input terminal 6 a when the second input terminal 6 b is used as a reference). When the potential is positive and lower than the target voltage value Vt (the voltage value of the DC output voltage Vdc to be output to the load RL), the boost chopper operation is performed. (2) The voltage value of the AC input voltage Vac is positive. When the voltage value is higher than the target voltage value Vt, the step-down chopper operation is performed. (3) When the voltage value of the AC input voltage Vac is negative, the inverting step-up / step-down 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.

  Of the three chopper operations of the chopper unit 2, the boost chopper operation will be described first. In this operation, the first switching element SW1 is always ON, and the third switching element SW3 and the fifth switching element SW5 are always OFF. Therefore, the AC / DC conversion device 1A in this operation is expressed by a simple equivalent circuit shown in FIG.

In this operation, the fourth switching element SW4 and the second switching element SW2 that functions as a rectifier diode are alternately turned ON / OFF. That is, when the fourth switching element SW4 is switched from the ON state to the OFF state, the second switching element SW2 is synchronously switched from the OFF state to the ON state. When the ON time of the fourth switching element SW4 in one switching cycle T is Ton4, the duty α (= Ton4 / T) of the fourth switching element SW4 can be obtained by the following equation.

Duty α = 1−Vac voltage value / Vdc voltage value

  In the step-down chopper operation, the second switching element SW2 is always on, and the fourth switching element SW4 and the fifth switching element SW5 are always off. Therefore, the AC / DC conversion device 1A in this operation is expressed by a simple equivalent circuit shown in FIG.

In this operation, the first switching element SW1 and the third switching element SW3 serving as a rectifier diode are alternately turned on / off. That is, when the first switching element SW1 is switched from the ON state to the OFF state, the third switching element SW3 is synchronously switched from the OFF state to the ON state. When the ON time of the first switching element SW1 in one switching cycle T is Ton1, the duty α (= Ton1 / T) of the first switching element SW1 can be obtained by the following equation.

Duty α = Voltage value of Vdc / Voltage value of Vac

  In the reverse buck-boost chopper operation, the fourth switching element SW4 is always in the ON state, and the second switching element SW2 and the third switching element SW3 are always in the OFF state. Therefore, the AC / DC conversion device 1A in this operation is expressed by a simple equivalent circuit shown in FIG.

Further, in this operation, the first switching element SW1 and the fifth switching element SW5 that functions as a rectifier diode are alternately turned ON / OFF. That is, when the first switching element SW1 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 ON time of the first switching element SW1 in one switching cycle T is Ton1, the duty α (= Ton1 / T) of the first switching element SW1 can be obtained by the following equation. However, the voltage value of the AC input voltage Vac is negative.

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

  As described above, in the AC / DC converter 1A according to the present embodiment, the control unit 5A performs (1) step-up chopper operation, (2) step-down chopper operation, and (3) inversion step-up / step-down operation. Switch to 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 1A according to the present embodiment, the diode bridge circuit (reference numeral 13 in FIG. 7 and reference numeral 21 in FIG. 8) can be eliminated, so that generation of loss due to the circuit is prevented. Can improve efficiency.

[Second Embodiment]
Subsequently, an AC / DC converter 1B according to a second embodiment of the present invention will be described. As shown in FIG. 1, the AC / DC converter 1B according to the present embodiment is the same as the AC / DC converter 1A according to the first embodiment except that the controller 5B is provided. For this reason, the detailed description about a circuit structure is abbreviate | omitted.

  As shown in FIG. 4, also in the present embodiment, the control unit 5B changes the ON / OFF control of each of the switching elements SW1 to SW5 according to the voltage value of the AC input voltage Vac. In other words, the chopper operation of the chopper unit 2 is changed according to the voltage value of the AC input voltage Vac.

  Specifically, the chopper unit 2 of the AC / DC converter 1B according to the present embodiment performs (1) a step-up / step-down chopper operation when the voltage value of the AC input voltage Vac is positive, and (2) an AC input. When the voltage value of the voltage Vac is negative, an inversion buck-boost chopper operation is performed. As a result, the voltage value of the DC output voltage Vdc is maintained (stabilized) at the target voltage value Vt.

  In the step-up / step-down chopper operation, the fifth switching element SW5 is always turned off. Therefore, the AC / DC conversion device 1B during this operation is expressed by a simple equivalent circuit shown in FIG.

In this operation, the first and fourth switching elements SW1 and SW4 and the second and third switching elements SW2 and SW3 that function as rectifier diodes are alternately turned ON / OFF. That is, when the first and fourth switching elements SW1 and SW4 are switched from the ON state to the OFF state, the second and third switching elements SW2 and SW3 are synchronously switched from the OFF state to the ON state. When the ON time of the first and fourth switching elements SW1 and SW4 in one switching period T is Ton14, the duty α (= Ton14 / T) of the first and fourth switching elements SW1 and SW4 can be obtained by the following equation. .

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

  In the reverse buck-boost chopper operation, the same control as the reverse buck-boost chopper operation of the first embodiment is performed. That is, the fourth switching element SW4 is always on, the second switching element SW2 and the third switching element SW3 are always off, and the first switching element SW1 and the fifth switching element SW5 serving as a rectifier diode are provided. The ON / OFF control is performed alternately (see FIG. 5B).

  As described above, in the AC / DC converter 1B according to the present embodiment, the control unit 5B switches the chopper operation of the chopper unit 2 to (1) the step-up / step-down chopper operation and (2) the inversion step-up / step-down 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 1B according to the present embodiment, a diode bridge circuit can be eliminated, so that loss due to the circuit can be prevented and efficiency can be improved.

  Furthermore, FIG. 6 shows an example in which the switching elements schematically shown are replaced with actual semiconductor elements. In the figure, the second switching element SW2 is replaced with a diode D2, and the fourth switching element SW4 is replaced with an n-channel MOSFET Q4. According to the circuit shown in FIG. 6, by connecting the anode of the diode D2 and the drain of the FET Q4 to the coil side, all the operations of the first embodiment and the second embodiment can be efficiently performed.

  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, Vt, for example, until a predetermined time elapses after the input of the AC input voltage Vac is started). Until it reaches about 95%), it is preferable to set the duty in each chopper operation to a duty different from the normal time. According to this, since the amount of inrush current can be limited without the inrush prevention circuit (reference numeral 12 in FIG. 7, reference numeral TH in FIG. 8), it is possible to prevent the occurrence of loss due to the circuit.

  More specifically, in the step-up chopper operation of the first embodiment, when the second switching element SW2 is in the ON state, an inrush current flows through the path of the first input terminal 6a → the coil L → the second switching element SW2 → the capacitor Co. Therefore, the amount of inrush current can be limited by shortening the ON time of the second switching element SW2 as compared with the normal time. The amount of inrush current can also be limited by lengthening the state in which the first switching element SW1 is OFF so that the step-up chopper operation of the first embodiment is not substantially performed. That is, the amount of inrush current can be limited by gradually increasing (soft start) the voltage value of the DC output voltage Vdc. Similarly, in the step-down chopper operation of the first embodiment, the duty α (= Ton1 / T) may be set lower than in normal times, and the ON time of the first switching element SW1 may be shortened.

  In the inverting buck-boost chopper operation of the first embodiment and the second embodiment, the energy stored in the coil L when the first switching element SW1 is switched to the OFF state is transferred to the capacitor Co through the fifth switching element SW5. To be supplied. Therefore, the amount of inrush current is limited by setting the duty α (= Ton1 / T) lower than usual to shorten the ON time of the first switching element SW1 and reducing the energy accumulated in the coil L. can do. Similarly, in the step-up / step-down chopper operation of the second embodiment, the duty α (= Ton14 / T) is set to be lower than in normal times to shorten the ON time of the first and fourth switching elements SW1, SW4, By reducing the energy stored in the coil L, the amount of inrush current can be limited.

  As another modification, by providing an input current detection circuit, the control units 5A and 5B allow each of the switching elements SW1 to SW1 to bring the input current waveform closer to a sine wave for power factor improvement and harmonic countermeasures. SW5 may be additionally controlled.

1A, 1B AC / DC converter 2 Chopper unit 3 Input voltage detection unit 4 Output voltage detection unit 5A, 5B Control unit

Claims (7)

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;
The first to fifth switching elements of the chopper unit such that the voltage value of the DC output voltage becomes the target voltage value based on voltage values detected by the input voltage detection unit and the output voltage detection unit. And a controller for controlling on / off of the
Between the first input terminal and the first output terminal, the first switching element, the coil, and the second switching element are connected in series from the input side to the output side,
One end of the third switching element is connected to a connection site between the first switching element and the coil, and the other end of the third switching element is connected to the second input end and the second output end,
One end of the fourth switching element is connected to a connection site between the coil and the second switching element, and the other end of the fourth switching element is connected to the second input end and the second output end,
The capacitor is on the output side of the second switching element and connected between the first output end and the second output end;
One end of the fifth switching element is connected to a connection portion between the first switching element and the coil, and the other end of the fifth switching element is connected to the first output end.
The control unit controls on / off of the first to fifth switching elements, and selectively selects one of a step-up chopper operation, a step-down chopper operation, a step-up / step-down chopper operation, and a reverse step-up / step-down chopper operation for the chopper unit. The AC / DC conversion device converts the AC input voltage into a DC output voltage having the target voltage value. The controller is
When the voltage value of the AC input voltage is positive and lower than the target voltage value, the chopper unit performs a boost chopper operation,
When the voltage value of the AC input voltage is positive and higher than the target voltage value, the chopper unit performs a step-down chopper operation,
2. The AC / DC converter according to claim 1, wherein when the voltage value of the AC input voltage is negative, the chopper unit performs an inverted buck-boost chopper operation. In the step-up chopper operation, the first switching element is turned on, the third and fifth switching elements are turned off, and the second switching element and the fourth switching element are alternately turned on / off. And
In the step-down chopper operation, the second switching element is turned on, the fourth and fifth switching elements are turned off, and the first switching element and the third switching element are alternately turned on / off. And
In the inverting buck-boost chopper operation, the fourth switching element is turned on, the second and third switching elements are turned off, and the first 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.   The control unit includes the step-up chopper until a predetermined time elapses after the input of the AC input voltage is started and / or until a voltage value of the DC output voltage reaches a predetermined voltage value. 4. The AC according to claim 2, wherein the duty is set to be low by shortening an ON time of the second switching element in operation and / or increasing an OFF time of the first switching element. 5. / DC converter. The controller is
When the voltage value of the AC input voltage is positive, the chopper part performs a step-up / step-down chopper operation,
2. The AC / DC converter according to claim 1, wherein when the voltage value of the AC input voltage is negative, the chopper unit performs an inverted buck-boost chopper operation. In the step-up / step-down chopper operation, the fifth switching element is turned off, and the first and fourth switching elements and the second and third switching elements are alternately turned on / off,
In the inverting buck-boost chopper operation, the fourth switching element is turned on, the second and third switching elements are turned off, and the first switching element and the fifth switching element are alternately turned on / off. 6. The AC / DC conversion apparatus according to claim 5, 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 The AC / DC converter according to claim 5 or 6, wherein the duty is set low by shortening the ON time of the first and fourth switching elements in the chopper operation.

Images