Fig. 1 presents the circuit configuration of the proposed AC-DC converter. The proposed converter
consists of the resonant-type rectifier which is reported by K. Matsui et al. [14] and the bidirectional
boost chopper. The resonant-type rectifier achieves a PFC operation using a resonance between the
inductor which is connected in series to the input terminal and the capacitors in parallel to the upper
arm. The resonant-type rectifier has been demonstrated in a commercial frequency in [14]. However,
this converter causes a low power density in the low-frequency operation because a bulky inductor and
capacitors as resonance components are required. Additionally, the possibility of the input impedance
matching is not discussed. In this paper, the resonant-type rectifier is operated at high-frequency.
Furthermore the function of the input impedance matching is evaluated. The high-frequency operation
improves the power density owing to the downsizing of the passive components.
In addition, Ref. [14] pointed out that the amplitude of the input current and the input power factor
hinge upon a load condition when a resistance load is connected directly to the resonant-type rectifier.
It means that the input impedance of the stand-alone resonant-type rectifier depends on the load
conditions. In order to overcome this problem, the bidirectional boost chopper is connected at the
output side of the resonant-type rectifier in Fig. 1. The bidirectional boost chopper is operated in
purpose to fix the operating point which is decided by the rectifier output voltage vch of the resonanttype
rectifier. The MOSFET S1 is used for an initial charge of the C4 instead of a diode because the
input power factor closes to zero when the rectifier outputs voltage vch is around zero.
The control for the chopper circuit does not need a high dynamic response. Thus, the chopper circuit
does not need either a high-speed or a high-frequency switching. Thus, the chopper may be operated at
a low switching frequency such as 20 kHz. However, a switching frequency of 100 kHz is selected in
this paper with the objective of the downsizing of the inductor L2.