B.-R. Lin

Analysis and implementation of a bidirectional converter with high conversion ratio

A bidirectional dc converter with high conversion ratio is presented in this paper to have the capability of bidirectional power flow. Two boost conversion stages are adopted in the converter to achieve high voltage step-up conversion. The other power flow direction can also be achieved in the proposed converter with low voltage step-down conversion. Comparison with the conventional boost converter with narrow turn-off period, the proposed converter has wide conversion ratio so that the higher or lower output voltage can be achieved. To reduce the switching losses and limit the voltage stress on the power switch, the boost type of active snubber is used in the converter. The resonance based on the output capacitance of power switch and resonant inductance at the transition interval will make the power switches to turn on at zero voltage switching (ZVS). The circuit configuration, principle operation, system analysis, and design consideration of the proposed converter are presented. Finally, experiments conducted on a laboratory prototype are presented to verify the effectiveness of the proposed converter.

Active Clamp Sepic Converter with Power Factor Correction

A soft switching sepic converter with active clamp scheme is presented in this paper to achieve zero voltage switching (ZVS) on the power switches. The active clamp topology is used in the circuit to limit the voltage stresses of power semiconductors. When main switch is turned off, the positive resonant inductor current flows through the anti-parallel diode of auxiliary switch so that the auxiliary switch can be turned on at ZVS. When auxiliary switch is turned off, the negative resonant inductor current will discharge the output capacitor of main switch so that the ZVS turn-on of main switch can be achieved. Finally, experiments based on a laboratory prototype rated at 300 W are presented to verify the effectiveness of the proposed converter.

Analysis of a Zero Voltage Switching Cuk Converter

A boost type zero voltage switching (ZVS) isolated Cuk converter is presented in this paper to reduce the switching losses of main switch. An auxiliary switch and a clamp capacitor are connected in parallel with the main switch to absorb all the energy stored in the leakage inductance of the transformer. The ZVS operation of main switch is achieved by the resonance with the resonant inductor and output capacitor of main switch. The ZVS operation of auxiliary switch is achieved by the resonance with the resonant inductor and the clamp capacitor. Therefore both switches are turned on at ZVS. The principle of operation, system analysis and design consideration are presented Finally, experiments based on an 180 W (12 V/15 A) prototype are provided to demonstrate the effectiveness of the proposed converter.

Implementation of parallel zero-voltage switching converter with series-connected transformers

SUMMARY This paper presents a parallel zero-voltage switching (ZVS) DC–DC converter with series-connected transformers. In order to increase output power, two transformers connected in series are used in the proposed converter. Two buck-type converters connected in parallel have the same switching devices. The primary windings of series-connected transformers can achieve the balanced secondary winding currents. The current doubler rectifiers with ripple current cancellation are connected in parallel at the output side to reduce the current stress of the secondary winding. Thus, the current ripple on the output capacitor is reduced, and the size of the output choke and output capacitor are reduced. Only two switches are used in the proposed circuit instead of four switches in the conventional parallel ZVS converter to achieve ZVS and output current sharing. Therefore, the proposed converter has less power switches. The ZVS turn-on is implemented during the commutation stage of two complementary switches such that the switching losses and thermal stresses on the semiconductors are reduced. Experimental results for a 528-W (48 V/11 A) prototype are presented to prove the theoretical analysis and circuit performance. Copyright

Analysis and Implementation of an Active Clamp Two-Switch Converter with Current Doubler Rectifie

A wide range active clamp two-switch converter with current doubler rectifier (CDR) is presented in this paper. An active clamp circuit based on two clamp switches and one clamp capacitor are used to recycle the energy stored in the transformer leakage inductor to minimize the spike voltage at the transformer primary side and reduce the voltage stress of switching devices. The resonant behavior based on the output capacitance and leakage inductance of the transformer during the transition interval between the main and clamp switches in the proposed converter is used to achieve ZVS operation of main switching devices. The duty ratio of main switching devices in the proposed converter can be more than 50% of the conventional forward converter. In the output stage of the proposed converter, the CDR circuit offers the ripple current cancellation at the output capacitor and reduces the current stress of transformer secondary winding. The winding turn of the current doubler rectifier is also reduced compared with the winding turn of the center-tapped rectifier. The circuit configuration and the principle of operation are analyzed and discussed. The design considerations of the proposed converter are provided. Finally, the characteristics of the proposed converter are verified on a 130 V -350 V input and 5 V/20 A output experimental prototype.