JP2010220309A - Bidirectional voltage step-up/down converter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a bidirectional voltage step-up/down converter capable of miniaturizing a reactor more than a conventional one and suppressing an increase in expenses for production. <P>SOLUTION: In the bidirectional voltage step-up/down converter, a voltage step-up chopper circuit has a plurality of voltage step-up switching elements connected in parallel to the other terminal of a voltage step-up reactor, a voltage step-down chopper circuit has a plurality of voltage step-down switching elements connected in parallel to the other terminal of a voltage step-down reactor, a control section causes the plurality of voltage step-up switching elements of the voltage step-up chopper circuit to switch so that an ON-timing is not superimposed in stepping up the DC voltage input from a first input output terminal, and causes the plurality of voltage step-down switching elements of the voltage step-down chopper circuit to switch so that the ON-timing is not superimposed in stepping down the DC voltage input from a second input output terminal. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a bidirectional buck-boost converter.

  When the motor / generator operates as a motor, it is necessary to output a voltage higher than the voltage of the battery to the motor / generator, and when the motor / generator operates as a generator, the motor / generator outputs When it is necessary to step down the power and charge the battery, generally, a bidirectional buck-boost converter (DC / DC converter) boosts the power output from the battery to the motor / generator, and from the motor / generator By reducing the power to be output to the battery, the voltage necessary for operating the motor / generator and the voltage that can be charged to the battery are obtained. As such a bidirectional buck-boost converter, a chopper-type bidirectional buck-boost chopper circuit having a relatively simple circuit configuration is widely used. This bidirectional buck-boost chopper circuit changes the current flowing through the reactor by repeatedly turning on / off a switching element such as a bipolar transistor or FET (Field Effect Transistor), and generates an induced electromotive force generated by the change in the current flowing through the reactor. Utilizing it, the voltage is stepped up and down.

  However, since the bidirectional buck-boost chopper circuit must operate in the “continuous current mode” without a period in which the current flowing through the reactor becomes zero, a reactor capable of storing a large amount of energy, that is, a large-scale reactor. Must be installed. And in a bidirectional | two-way buck-boost chopper circuit, you have to enlarge own volume with mounting of a big reactor. Therefore, as an invention that solves such a problem, Patent Document 1 below discloses a bidirectional converter that can reduce the size of a reactor because it is not necessary to lower the switching frequency by reducing the switching loss. Yes. This bidirectional converter comprises a step-up chopper circuit composed of a step-up reactor, a step-up switching element and a step-up diode composed of a wide gap semiconductor unipolar device, and a step-down reactor, a step-down switching element and a wide gap semiconductor unipolar device. A step-down chopper circuit including a step-down diode.

JP 2006-006061 A

By the way, the bidirectional buck-boost chopper circuit in the prior art has a problem that the volume of the reactor has to be increased as described above.
Further, in the above-mentioned prior art 1 in the above prior art, unipolar diodes such as SiC or GaN are employed as boosting and stepping-down diodes in the bidirectional buck-boost chopper circuit. However, since unipolar diodes such as SiC or GaN are expensive, the bidirectional buck-boost chopper circuit to which the above-mentioned Patent Document 1 is applied has a problem that the production cost increases.

  The present invention has been made in view of the above-described circumstances, and provides a bidirectional buck-boost converter capable of reducing the size of a reactor as compared with the prior art and suppressing an increase in production costs. With the goal.

  In order to achieve the above object, according to the present invention, as a first solution for a bidirectional buck-boost converter, a boosting reactor having one terminal connected to a first input / output terminal is provided. A step-up chopper circuit that boosts a DC voltage input from a terminal by the boosting reactor and outputs the boosted DC voltage from a second input / output terminal; and a step-down reactor having one terminal connected to the first input / output terminal A step-down chopper circuit that steps down a DC voltage input from a second input / output terminal by the step-down reactor and outputs the stepped-down DC voltage from the first input / output terminal, the step-up chopper circuit, and the step-down chopper A bidirectional buck-boost converter comprising a control unit for controlling the circuit, wherein the boost chopper circuit is connected in parallel to the other terminal of the boost reactor The step-down chopper circuit includes a plurality of step-down switching elements connected in parallel to the other terminal of the step-down reactor, and the control unit includes the first input / output terminal. When boosting the DC voltage input from, the plurality of boosting switching elements of the boost chopper circuit are switched so that the ON timing does not overlap, and the DC voltage input from the second input / output terminal is stepped down. In such a case, means for switching to the plurality of step-down switching elements of the step-down chopper circuit is employed so that the ON timing does not overlap.

  In the present invention, as a second solving means related to the bidirectional buck-boost converter, in the first solving means, the control unit is configured to increase the number of DC voltages input from the first input / output terminal. The step-up switching element is switched at equal time intervals.

  In the present invention, as a third solving means related to the bidirectional buck-boost converter, in the first or second solving means, the control unit steps down a DC voltage input from the second input / output terminal. In addition, means for switching the plurality of step-down switching elements at equal time intervals is employed.

  In the present invention, as a fourth solving means related to the bidirectional buck-boost converter, in any one of the first to third solving means, a step-up / step-down reactor is provided, and the step-up / step-down reactor is used at the time of boosting. And is used as a step-down reactor at the time of step-down.

  In the present invention, as a fifth solving means related to the bidirectional buck-boost converter, in any one of the first to fourth solving means, the control unit boosts the DC voltage input from the first input / output terminal. In this case, means for changing the step-up rate by changing the ON duty of the plurality of step-up switching elements is adopted.

  In the present invention, as a sixth solving means relating to the bidirectional buck-boost converter, in any one of the first to fifth solving means, a control unit is provided, and the control unit is input from the second input / output terminal. In the case of stepping down the DC voltage, a means is adopted in which the step-down rate is changed by changing the ON duty of the plurality of step-down switching elements.

  According to the present invention, in the bidirectional buck-boost converter, the step-up chopper circuit has a plurality of step-up switching elements connected in parallel to the other terminal of the step-up reactor, and the step-down chopper circuit includes the other step-down reactor. And a plurality of step-up chopper circuits so that the ON timing does not overlap when the DC voltage input from the first input / output terminal is stepped up. When the DC voltage input from the second input / output terminal is stepped down, switching is performed to a plurality of step-down chopper circuits of the step-down chopper circuit so that the ON timing does not overlap.

  In this way, in the bidirectional buck-boost converter, by providing a plurality of step-up switching elements and a plurality of step-down switching elements, switching with a short cycle can be performed, so that the energy stored in the reactor at a time can be reduced. I can do it. And in bidirectional | two-way buck-boost converter A, it becomes possible to reduce a reactor in size.

  In addition, in the bidirectional buck-boost converter, by providing a plurality of step-up switching elements and step-down switching elements, the number of times of switching per unit time can be increased, so that the ripple of the output DC voltage is reduced. I can do it. In addition, the bidirectional buck-boost converter can suppress the increase in production cost because the number of times of switching per unit time can be increased without mounting an expensive unipolar diode such as SiC or GaN. I can do it.

It is a circuit diagram which shows the structure of the bidirectional | two-way buck-boost converter A which concerns on one Embodiment of this invention. It is a circuit diagram which shows the structure of the bidirectional | two-way buck-boost chopper circuit which is one of the conventional bidirectional | two-way buck-boost converters. It is a wave form diagram which shows the switching period at the time of pressure | voltage rise of the bidirectional | two-way buck-boost converter A which concerns on one Embodiment of this invention, and the conventional bidirectional | two-way buck-boost chopper circuit. FIG. 6 is a waveform diagram of a boosted DC voltage output from a bidirectional buck-boost converter A according to an embodiment of the present invention and a conventional bidirectional buck-boost chopper circuit.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings. The present embodiment relates to a bidirectional buck-boost converter that boosts or steps down an input voltage.
First, the circuit configuration of the bidirectional buck-boost converter A according to the present embodiment will be described with reference to FIG. FIG. 1 is a circuit diagram showing a configuration of a bidirectional buck-boost converter A according to the present embodiment.
The bidirectional step-up / down converter A boosts the DC voltage input from the battery B and outputs it to the inverter C as a load, and steps down the DC voltage input from the inverter C and outputs it to the battery B. , First input / output terminals 1a and 1b, step-up / down reactor 2, step-up MOSFETs (Metal Oxide Semiconductor Field Effect Transistors) 3a to 3c, step-down MOSFETs 4a to 4c, capacitor 5, second input / output terminals 6a and 6b, and control unit 7 is provided.

First input / output terminals 1a and 1b are used to input a DC voltage input from battery B to bidirectional buck-boost converter A and to output a DC voltage stepped down by bidirectional buck-boost converter A to battery B. A pair of connection terminals. One first input / output terminal 1 a is connected to the positive terminal of the battery B, and the other first input / output terminal 1 b is connected to the negative terminal of the battery B.
The step-up / down reactor 2 has one end connected to one first input / output terminal 1a and the other end connected to the drain terminals of the step-up MOSFETs 3a to 3c and the source terminals of the step-down MOSFETs 4a to 4c.

  The boosting MOSFETs 3 a to 3 c are connected in parallel to the other end of the step-up / step-down reactor 2. The step-down MOSFETs 4a to 4c are also connected in parallel to the other end of the step-up / step-down reactor 2 in the same manner as the step-up MOSFETs 3a to 3c. The six boosting MOSFETs 3a to 3c and the step-down MOSFETs 34a to 4c constitute first to third switching arms as shown in FIG. That is, among the six step-up MOSFETs 3a to 3c and the step-down MOSFETs 4a to 4c, the step-up MOSFET 3a and the step-down MOSFET 4a serve as the first switching arm, and the step-up MOSFET 3b and the step-down MOSFET 4b serve as the third switching arm. Further, the step-up MOSFET 3c and the step-down MOSFET 4c constitute a third switching arm, respectively.

  In the step-up MOSFET 3a constituting the first switching arm, the drain terminal is the other end of the step-up / step-down reactor 2 and the source terminal of the step-down MOSFET 4a, the source terminal is the one first input / output terminal 1b, and the gate terminal is Each is connected to the control unit 7. The step-down MOSFET 4a has a drain terminal connected to the second input / output terminal 6a, a source terminal connected to the other end of the step-up / step-down reactor 2, the drain terminal of the step-up MOSFET 3a as described above, and a gate terminal connected to the control unit 7. Are connected to each.

  The step-up MOSFET 3b constituting the second switching arm has a drain terminal connected to the other end of the step-up / step-down reactor 2 and the source terminal of the step-down MOSFET 4b, a source terminal connected to the first input / output terminal 1b, and a gate terminal Each is connected to the control unit 7. In the step-down MOSFET 4b, the drain terminal is connected to the second input / output terminal 6a, the source terminal is the other end of the step-up / step-down reactor 2, the drain terminal of the step-up MOSFET 3b as described above, and the gate terminal is the control unit 7. Are connected to each.

In the step-up MOSFET 3c constituting the third switching arm, the drain terminal is the other end of the step-up / step-down reactor 2 and the source terminal of the step-down MOSFET 4c, the source terminal is the one first input / output terminal 1b, and the gate terminal is Each is connected to the control unit 7. The step-down MOSFET 4c has a drain terminal connected to the second input / output terminal 6a, a source terminal connected to the other end of the step-up / step-down reactor 2, the drain terminal of the step-up MOSFET 3c as described above, and a gate terminal connected to the control unit 7. Are connected to each.
A control signal is input from the control unit 7 to each gate terminal of the step-up MOSFETs 3a to 3c and the step-down MOSFETs 4a to 4c. The boosting MOSFETs 3a to 3c and the step-down MOSFETs 4a to 4c are turned on / off based on the control signal.

  The capacitor 5 is provided for the purpose of reducing the ripple of the DC voltage output to the inverter C, that is, for smoothing, and has one end connected to the drain terminal of each of the step-down MOSFETs 4a to 4c and the one of the second input. Connected to the output terminal 6a, the other end is connected to the source terminals of the boosting MOSFETs 3a to 3c, the other first input / output terminal 1b and the other second input / output terminal 6b.

The second input / output terminals 6a and 6b are a pair for outputting the DC voltage boosted by the bidirectional buck-boost converter A to the inverter C and for inputting the DC voltage input from the inverter C to the bidirectional buck-boost converter A. One second input / output terminal 6a is connected to one end of the inverter C, and the other second input / output terminal 6b is connected to the other end of the inverter C.
The control unit 7 includes a CPU (Central Processing Unit), ROM (Read Only Memory), RAM (Random Access Memory), boosting MOSFETs 3a to 3c, and step-down MOSFETs 4a to 4c and interface circuits for inputting and outputting signals. The step-up MOSFETs 3a to 3c and the step-down MOSFETs 4a to 4c are controlled based on the control program stored in the ROM.

Next, the operation of the bidirectional buck-boost converter A configured as described above will be described in detail.
First, the boosting operation in the bidirectional buck-boost converter A will be described. In this case, the first input / output terminals 1a and 1b are on the input side, and the second input / output terminals 6a and 6b are on the output side.

  When boosting the DC voltage input from the battery B, the control unit 7 turns off all the step-down MOSFETs 4a to 4c, and turns on / off the step-up MOSFETs 3a to 3c by sequentially shifting the phase by 120 degrees. Is repeated to boost the DC voltage input from the battery B. At this time, the control unit 7 prevents the ON timings of the boosting MOSFETs 3a to 3c from overlapping each other.

  FIG. 2 is a circuit diagram showing a configuration of a bidirectional buck-boost chopper circuit which is one of the conventional bidirectional buck-boost converters. FIG. 3 shows a bidirectional buck-boost converter A according to this embodiment and a conventional one. FIG. 4 is a waveform diagram showing a switching cycle at the time of boosting with the bidirectional buck-boost chopper circuit, and FIG. 4 is a boost output from the bidirectional buck-boost converter A according to the present embodiment and the conventional bidirectional buck-boost chopper circuit. FIG.

  FIG. 3A is a waveform diagram showing switching periods of the boosting MOSFETs 3a to 3b at the time of boosting of the bidirectional buck-boost converter A, and FIG. 3B is a bidirectional buck-boost shown in FIG. It is a wave form diagram which shows the switching period of step-up MOSFET at the time of step-up of a pressure chopper circuit. In FIG. 3A, the solid rectangle indicates that the boost MOSFET 3a is ON, the broken rectangle indicates that the boost MOSFET 3b is ON, and the alternate long and short dash line rectangle indicates that the boost MOSFET 3c is ON. It is shown that. In FIGS. 3A and 3B, the vertical axis represents voltage, and the horizontal axis represents time.

  4A is a waveform diagram showing a boosted DC voltage output from the bidirectional buck-boost converter A, and FIG. 4B is an output of the bidirectional buck-boost chopper circuit shown in FIG. It is a wave form diagram which shows the stepped up DC voltage. And in (a), (b) of Drawing 4, a vertical axis shows voltage and a horizontal axis shows time.

  As shown in FIG. 3A, the bidirectional buck-boost converter A according to the present embodiment performs switching with a shorter period within a unit time as shown in FIG. As described above, the bidirectional buck-boost converter A can reduce the energy stored in the step-up / step-down reactor 2 at a time by performing switching at a short cycle, and therefore, the step-up / step-down reactor 2 can be downsized. Is possible. Further, since the bidirectional buck-boost converter A has a short switching cycle, as shown in FIG. 4A, the ripple of the boosted DC voltage to be output becomes smaller as compared with FIG. 4B.

  Further, in the bidirectional step-up / down converter A, the control unit 7 can increase the step-up rate by increasing the ON duty of the switching of the step-up MOSFETs 3a to 3b shown in FIG. Moreover, the step-up rate can be lowered by lowering the ON duty.

Next, the step-down operation in the bidirectional buck-boost converter A will be described. In this case, the second input / output terminals 6a and 6b are on the input side, and the first input / output terminals 1a and 1b are on the output side.
When the DC voltage input from the inverter C is stepped down, the control unit 7 turns off all the step-up MOSFETs 3a to 3c, and turns on / off the step-down MOSFETs 4a to 4c by sequentially shifting the phase by 120 degrees. Is repeated to step down the DC voltage input from the inverter C. At this time, the controller 7 prevents the step-down MOSFETs 4a to 4c from turning on at the same timing.

  In the bidirectional step-up / down converter A, the control unit 7 can increase the step-down rate and increase the ON duty by decreasing the ON duty of switching of the step-down MOSFETs 4a to 4b at the time of step-down. Thus, the step-down rate can be lowered.

  As described above, in the bidirectional buck-boost converter A according to the present embodiment, when the DC voltage input from the battery B is boosted, the boosting MOSFETs 3a to 3c repeat ON / OFF in order to shorten the DC voltage. Boosting by switching in a cycle becomes possible. In the bidirectional buck-boost converter A, when the DC voltage input from the inverter C is stepped down, the step-down MOSFETs 4a to 4c can be stepped down by switching in a short cycle by repeating ON / OFF in order. become.

  As described above, the bidirectional buck-boost converter A includes the boosting MOSFETs 3a to 3c and the step-down MOSFETs 4a to 4c, so that switching can be executed in a short cycle. Therefore, the energy stored in the buck-boost reactor 2 at a time. Can be reduced. In the bidirectional step-up / step-down converter A, the step-up / step-down reactor 2 can be downsized. Further, in the bidirectional buck-boost converter A, by providing a plurality of boosting MOSFETs and step-down MOSFETs, the number of times of switching per unit time can be increased, so the ripple of the output DC voltage is reduced. I can do it. Furthermore, in the bidirectional buck-boost converter A, since the number of switching per unit time can be increased without mounting an expensive unipolar diode such as SiC or GaN, the increase in production cost is suppressed. I can do it.

As mentioned above, although one Embodiment of this invention was described, this invention is not limited to the said embodiment, For example, the following modifications can be considered.
(1) In the above embodiment, the three step-up MOSFETs 3a to 3c are connected in parallel and the three step-down MOSFETs 4a to 4c are connected in parallel. However, the present invention is not limited to this.

  For example, the bidirectional buck-boost converter A may include two boosting MOSFETs and two step-down MOSFETs, or may include four or more boosting MOSFETs and step-down MOSFETs. It may be. In such a case, the switching timing of the step-up MOSFET and the step-down MOSFET is shifted by “360 / number of step-up MOSFETs (step-down MOSFETs)”, respectively.

In addition, when the number of boosting MOSFETs and step-down MOSFETs is n, the ripple of the DC voltage output from the bidirectional buck-boost converter A is smaller than that in the case where there is one boosting MOSFET and step-down MOSFET. 1 / n ". That is, as the number of step-up MOSFETs and step-down MOSFETs increases, the ripple of the output DC voltage can be reduced.
Further, a general bipolar type can be used as the switching element instead of the MOSFET. When the number of step-up switching elements and step-down switching elements is two or three, a commercially available full bridge circuit can be used, and thus production costs can be reduced.

(2) In the above embodiment, the control unit 7 changes the ON duty of the boosting MOSFETs 3a to 3c in order to change the boosting rate. However, the control unit 7 synchronizes with the ripple generated by the inverter C that is the output destination of the boosted voltage. By controlling the boosting MOSFETs 3a to 3c so as not to generate ripples, the operation in the inverter C can be stabilized.

A ... Bidirectional buck-boost converter, 1a, 1b ... First input / output terminal, 2 ... Buck-boost reactor, 3a-3c ... Boosting MOSFET, 4a-4c ... Step-down MOSFET, 5 ... Capacitor, 6a, 6b ... Second Input / output terminals, 7 ... control section

Claims (6)

A boosting reactor having one terminal connected to the first input / output terminal; the DC voltage input from the first input / output terminal is boosted by the boosting reactor; and the boosted DC voltage is boosted to the second input / output terminal A step-up chopper circuit that outputs from
The first input / output terminal has a step-down reactor having one terminal connected thereto, the DC voltage input from the second input / output terminal is stepped down by the step-down reactor, and the stepped-down DC voltage is reduced to the first input / output terminal. A step-down chopper circuit that outputs from
A bidirectional buck-boost converter comprising a control unit for controlling the step-up chopper circuit and the step-down chopper circuit,
The step-up chopper circuit has a plurality of step-up switching elements connected in parallel to the other terminal of the step-up reactor;
The step-down chopper circuit has a plurality of step-down switching elements connected in parallel to the other terminal of the step-down reactor,
When the DC voltage input from the first input / output terminal is boosted, the control unit causes the plurality of boosting switching elements of the boosting chopper circuit to switch so that the ON timing does not overlap, and the second input A bidirectional buck-boost converter, wherein when stepping down a DC voltage input from an output terminal, the step-down chopper circuit switches the step-down chopper circuit so that ON timing does not overlap.   2. The bidirectional device according to claim 1, wherein when the DC voltage input from the first input / output terminal is boosted, the control unit switches the plurality of boosting switching elements at equal time intervals. 3. Buck-boost converter.   3. The control unit according to claim 1, wherein when the DC voltage input from the second input / output terminal is stepped down, the control unit switches the plurality of step-down switching elements at equal time intervals. 4. Bidirectional buck-boost converter. With a step-up / down reactor,
The bidirectional step-up / step-down converter according to any one of claims 1 to 3, wherein the step-up / step-down reactor is used as the step-up reactor when boosting, and is used as the step-down reactor when stepping down.   The control unit, when boosting the DC voltage input from the first input / output terminal, changes the boost rate by changing ON duty of the plurality of boost switching elements. Item 5. The bidirectional buck-boost converter according to any one of Items 1 to 4. A control unit,
The control unit, when stepping down a DC voltage input from the second input / output terminal, changes the step-down rate by changing ON duty of the plurality of step-down switching elements. Item 6. The bidirectional buck-boost converter according to any one of Items 1 to 5.

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