A current-fed zero-voltage-switching (ZVS) and zero-current-switching (ZCS) CL-resonant push–pull dc – dc converter is given in this paper. The planned push–pull converter topology is suitable for unchecked low-voltage to high-voltage power conversion with low ripple input current. The resonant density of both capacitor and inductor is operated at almost twice the main switching density.
In this topology, the main switch is control under ZVS because of the commutation of the transformer magnetising current and the parasitic drain–source capacitance. Because of the leakage inductance of the transformer and the resonant capacitance from the resonant circuit, both the main switch and output rectifier are operated by implementing ZCS. The operation and work of the planned converter has been cofirmed on a 400-W prototype.
Figure 1 Schematic diagram of the proposed current-fed ZVS–ZCS CL-resonant push–pull dc–dc converter
EXPECTED SIMULATION RESULTS:
Figure 2 Measured waveforms of gate to source voltage and drain to source voltage a ZVS operations for Q1 and Q2 at the full load b Expanded scale of Fig. 7a in point A
Figure 3 ZCS operations for Q1 and Q2 at the full load
Figure 4 ZCS operations for rectifier diode at the full load
Figure 5 Waveforms of vin, iin, ip and icr at the full load
Figure 6 Waveforms with excessive dead time
Figure 7 Step change with resistance load
a Load connection
b Load disconnection
This study prepared, analysed, and quantified a current-fed ZVS–ZCS CL-resonant push–pull dc–dc converter that utilises the commutation of the transformer magnetizing current and the parasitic drain–source capacitance to obtain the main switch to be operated under ZVS. By using the leakage inductance of a transformer and resonant capacitor, a sinusoidal current is formed in this resonant circuit by turning on and off the switch.
Thus, both the main switch and the output rectifier can be operated under ZCS. Because this prepared converter includes an input inductance, the input terminal of the converter cannot be added with a filter. This converter can reach a steady state with a small ripple input current, which is particularly suitable for unregulated dc–dc conversion from a low-voltage high-current source.
From the experimental results, the main switch can be control using both ZVS and ZCS and the output rectifier can be conducted using ZCS. The control principles and logical analysis of this planned converter were verified by using a 400-W and 65-kHz original. The overall ability of the converter nearly reached 93% at full output power.
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