CROSS REFERENCE TO RELATED APPLICATIONS

This application is a National Stage of International Application No. PCT/JP2016/056857, filed Mar. 4, 2016.

TECHNICAL FIELD

The present invention relates to a power conversion device including a coupling reactor and a capacitor, and more particularly, to a coupling coefficient of a coupling reactor at which a size and cost are reduced.

BACKGROUND ART

Rapid changes in global environment typified by global warming and matters concerning the use of energy resources are a major topic of discussion in today's world, and electric vehicles (EVs), as well as hybrid automobiles including hybrid electric vehicles (HEVs) and plug-in hybrid electric vehicles (PHEVs), are being developed as ecologically friendly automobiles.

In hybrid automobiles in which an engine and a traction motor are mounted to use one or both of the engine and the traction motor as a main drive source, a boost converter or a similar power conversion device has been used in order to optimize the battery voltage and the drive voltage of an inverter, which is connected to the traction motor.

The boost converter or similar power conversion device for automobiles of this type is demanded to be smaller in size and loss with the advancement in power electronics technology. As an example of the related art, a converter circuit using a reactor for a multi-phase converter is disclosed in which the reactor includes a core and multi-phase coils wound around the core and magnetically coupled to each other.

CITATION LSIT

Patent Literature

[PTL 1] JP 2012-65453 A

SUMMARY OF INVENTION

Technical Problem

A boost converter circuit using a magnetic coupling reactor of the related art has the following problem:

In a boost converter using a magnetic coupling reactor of the related art, ripple current components of reactors of the respective phases switch in the same phase, unlike in an interleave configuration, which means that the total ripple current of the reactors has an amplitude that is the sum of the ripple currents of the respective phases. The ripple current of a filtering capacitor provided upstream of the magnetic coupling reactor is accordingly increased. This gives rise to a problem of an increase in size of the capacitor and in manufacturing cost.

The present invention has been made to solve the problem described above, and it is an object of the present invention to provide a power conversion device free from the possibility of an increase in size of a capacitor in a multi-phase converter using a magnetic coupling reactor by adjusting the coupling factor of the magnetic coupling reactor.

Solution to Problem

According to one embodiment of the present invention, there is provided a power conversion device, which is configured to convert a voltage input from a power source into a desired direct current voltage, the power conversion device including: a first semiconductor switching element and a second semiconductor switching element, which are connected in series between a positive output terminal and a negative output terminal; a third semiconductor switching element and a fourth semiconductor switching element, which are connected in series between the positive output terminal and the negative output terminal at a point closer to the output terminals than the first semiconductor switching element and the second semiconductor switching element are; a controller, which is configured to control on/off of each of the first semiconductor switching element, the second semiconductor switching element, the third semiconductor switching element, and the fourth semiconductor switching element; a magnetic coupling reactor including a first winding wire and a second winding wire, which are wound around a shared iron core so as to be magnetically coupled to each other in opposite directions at a turn ratio of 1:1, the first winding wire being connected between a connection point connecting the first semiconductor switching element to the second semiconductor switching element and a positive input terminal, the second winding wire being connected between a connection point connecting the third semiconductor switching element to the fourth semiconductor switching element and the positive input terminal; and an input capacitor, which is configured to reduce a ripple current, the input capacitor being connected, on a positive side thereof, to the positive input terminal and an input side of the magnetic coupling reactor, the input capacitor being connected, on a negative side thereof, to a negative input terminal and the negative output terminal, wherein the magnetic coupling reactor has a coupling factor equal to or less than a set value, the set value being determined by taking into consideration an area in which the ripple current of the input capacitor increases rapidly in response to a rise in coupling factor.

Advantageous Effects of Invention

According to the present invention, in the power conversion device provided with the multi-phase converter in which the magnetic coupling reactor element is included, a ripple current flowing into the capacitor that is provided upstream of the magnetic coupling reactor can be suppressed and the size of the capacitor can be reduced by keeping the coupling factor of the magnetic coupling reactor to a value equal to or less than a set value. In this manner, it is possible to provide a small-sized, highly efficient power conversion device having a small number of parts.

