(a) Field of the Invention
The present invention relates to a pulse width modulation resonance converter and a charger for a vehicle using the same. 
(b) Description of the Related Art
Recently, since chargers mounted within an electric vehicle (hereinafter, referred to as an ‘EV’) which rapidly rises in demand and a plug-in hybrid type vehicle are important components which are directly connected to fuel efficiency of the vehicle, the demand for high efficiency has increased.  Since a vehicle mounted type charger uses commercial power as an input, the commercial power needs to be used in an input voltage range of about 90 Vrms to 265 Vrms, needs to have power-factor improvement, and needs to correspond to a charging voltage in a wide range of about 250 V to 450 V according to a battery specification. 
In order to satisfy the requirements, a converter for EV charging is configured by two steps of a power factor correction (PFC) boost converter (hereinafter, referred to as a PFC converter), which is an alternating current-direct current (AC/DC) converter for power-factor improvement and a DC/DC converter configured to convert a DC voltage output from the PFC converter into a battery charging voltage.  Among the converters, the DC/DC converter uses an insulation type transformer for insulation, and the insulation type DC/DC converter has a substantial effect on efficiency of the charger. 
For the DC/DC converter for the commercialized EV charger, a phase shift full bridge (hereinafter, referred to as a ‘PSFB’) type converter is mainly used, and in the PSFB type converter, soft switching may be difficult at a substantially low load, an excessive internal voltage is applied to a rectified terminal of a secondary side to use an element having a substantial conduction loss, and a snubber for reducing voltage surge is required.  As a result, for the PSFB type converter, it may be difficult that efficiency at a maximum load exceeds about 92%. 
The above information disclosed in this section is merely for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.