【正文】 relying mainly on the transformer primary current to charge/discharge the appropriate switch capacitances just prior to turnon. From ZVS point of view, the leftleg switches ( and ) and the rightleg switches ( and ) operate under significantly differentconditions. The rightleg switches undergo turnon/turnoff during the transition from the powertransfer interval to the freewheeling interval, while the leftleg switches turn on/off during the transition from the freewheeling interval to the powertransfer interval. As shown in Fig. 1(b), during the rightleg transition, the transformer primary current does not change direction and remains in the proper direction to achieve discharging of the appropriate switch capacitance to achieve ZVS. However, during the leftleg transition the current reduces and eventually changes polarity. Therefore, the energy available for charging/discharging the switch capacitance is less, and hence, achieving ZVS for the leftleg switches is more difficult.The energy available is a function of the load current, and atlightloads ZVS is lost [1]–[4].There are two main ways by which the ZVS load range can be increased in the conventional PMC. The first approach is to make the leakage inductance of the transformer very large or to add an external inductor in series with the transformer approach, while extending the ZVS loadrange, results in high loss of voltseconds, requiring the transformer turnsratioto be promised. The net result is increased switch current and conduction losses. Use of saturable inductors [5], [6] instead of linear inductors reduces the voltseconds lost to a certain extent, but still cannot achieve ZVS at very light second approach to increasing the ZVS load range is to increase the magnetizing current of the transformer. In conventional PMC, this results in significant increase in the rms switch current, since during the entire freewheeling interval the magnetizing current circulates through the switches at its peak value.Therefore, in conventional PMC, ZVS at lightloads is achieved only at the expense of increased conduction modifications of the basic PMC have been proposed to extend the ZVS range down to very light loads, with smaller penalty on conduction losses. A mutation aid network consisting of an external inductor in series with the primary of the transformer and two clamping diodes is proposed in [7], [8]. Use of saturable inductors along with increased magnetizing current is discussed in [5] and secondaryside control using magamps is suggested in [9].A novel hybrid fullbridge converter that achieves ZVS rightdown to noload without serious conduction loss penalty was proposed in [10]. Apart from the improved softswitching characteristics, another distinguishing feature of this hybrid converter is that the filter waveforms, both at the input and the output are close to ideal (which is pure dc). Hence, the filter requirements are significantly less. The present paper is a more plete presentation of the hybrid configuration proposed in 10.II. PROPOSED CONFIGURATIONThe schematic diagram of the proposed configuration is shown in Fig. 2. As seen, it is a hybrid bination of a halfbridge section, prising of the switches and , and the transformer , and a fullbridge section prisingof the switches , , and , and the transformer . Since the switches and are mon to both the sections, the hybrid bination is realized using just fourswitches as in a regular fullbridge converter (with the same total switch ratings). The output of each section is added at the secondary, rectified and filtered to obtain regulated dc will be explained in detail in later sections, the halfbridge section is uncontrolled (., operates with full pulsewidth always) while the pulsewidth of the fullbridge section is controlled by varying the phaseshift between the two legs, A and B. All the four switches are operated at fixed 50% dutyratio (neglecting the small timedelay provided to achieve ZVS transitions) and constant switching frequency